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The extraordinary thermal activity of El Tatio Geyser Field, Antofagasta Region, Chile

January 2003

Authors:

Alan Glennon

University of California, Santa Barbara

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31The GOSA Transactions2003

Abstract

El Tatio Geyser Field (locally known as Los Géiseres del

Tatio) is located within the Andes Mountains of northern

Chile at 4,200 meters above mean sea level, 150 kilometers

east, southeast of Calama, Chile. With over 80 active gey-

sers, El Tatio is the largest geyser field in the southern hemi-

sphere and the third largest field in the world, following

Yellowstone, USA, and Dolina Geizerov, Russia. From

March 19–21, 2002, the authors visited the geothermal field

to inventory the geysers and their behavior. Of over 110

erupting springs documented, more than 80 were identified

as true geysers and an additional 30 were perpetual spouters.

Despite reports that geyser activity occurred only in the

morning, no abatement in activity was observed at any time

within any part of the field. Although the observed activity

was vigorous, eruptions commonly reached less than one

meter. Of the erupting springs cataloged, the mean spout-

ing height was 69 centimeters. Of the true geysers cata-

loged, the eruptions averaged 76 centimeters. El Tatio Gey-

ser Field contains approximately 8 percent of the world’s

geysers.

TABLE OF CONTENTS

ACKNOWLEDGEMENTS

PART I. EL TATIO GEYSER FIELD

A. INTRODUCTION

B. GEOGRAPHY

C. HYDROGEOLOGIC SETTING

D. METHODS

E. DISCUSSION AND FUTURE

RESEARCH

PART II. SPRING DESCRIPTIONS

PART III. APPENDICES:

I. Summary of Geyser Activity

II. Expedition Log

III. Hazards

REFERENCES

Acknowledgements

We wish to thank our friends Shane Fryer and

Weldon Hawkins for their assistance in the field.

Scott Bryan (Geyser Observation and Study Asso-

ciation) and Randall Marrett (Department of Geo-

logical Sciences, University of Texas at Austin) were

particularly helpful in providing information on pre-

vious investigations to the area. Thanks to Keith

and Arlene Pfaff for aiding in travel logistics. Cyril

Cavadore graciously allowed the use of several

photographs of the basin. Special thanks to Larry

Fryer for making special travel arrangements for

our group.

The Extraordinary Thermal Activity of

El Tatio Geyser Field,

Antofagasta Region, Chile

J. Alan Glennon

Department of Geography

University of California, Santa Barbara

Santa Barbara, California 93106

Rhonda M. Pfaff

Environmental Systems Research Institute

380 New York Street

Redlands, California 92373

A Special Report

The authors among the mudpots of Group M-III.

Left to right: Alan Glennon, Weldon Hawkins,

Rhonda Pfaff and Shane Fryer. (Photo by Alan

Glennon)

32 The GOSA Transactions Volume VIII

PART I. EL TATIO GEYSER FIELD

I. INTRODUCTION

El Tatio Geyser Field, with over 100 erupting

springs, is the largest geyser field in the southern

hemisphere and the third largest field in the world,

following Yellowstone, USA, and Dolina Geizerov,

Russia. From March 19–21, 2002, a four–person

team visited the geothermal field to inventory the

area’s geysers and their behavior. Of over 100 fea-

tures documented, more than 80 were identified as

true geysers and an additional 30 or more appear

to be perpetual spouters (however, some of these

spouters may be geysers with long durations). Three

regions at El Tatio where geysers have been previ-

ously reported were not visited. An extended study

at El Tatio would likely find many more true gey-

sers. Although the observed activity at El Tatio is

vigorous, eruption heights are commonly less than

one meter. Numerous uncataloged springs continu-

ously boil and occasionally eject small erratic

splashes.

The Tatio geysers (locally known as Los

Géiseres del Tatio) are located within the Andes

Mountains of northern Chile at 4,200 meters above

mean sea level, 150 kilometers east, southeast of

Calama, Chile. El Tatio spans a 10 km2 region of

Andean altiplano. Geyser activity is fueled by wa-

ter heated by a volcanic complex that lies primarily

east of the field. Ignimbrite (which is composition-

ally similar to rhyolite) is the likely source of silica

needed for development of the geyser plumbing

network.

Within the field (Map A, above), three separate

zones of geysers exist, each with a different char-

acter. The three major geyser zones are: 1) The

Map A — Index Map to El Tatio Geyser Field

33The GOSA Transactions2003

Upper Geyser Basin (or Main Terrace) lies near

the floor of a gently sloping valley and is charac-

terized by relatively low water discharge but well–

developed sinter terraces. Numerous large active

and inactive geyser cones lie within the Upper Ba-

sin. The Upper Basin is the largest of the fields

(spanning 5 km2) and contains the greatest single

number of erupting springs. A feature in this zone

was the tallest observed geyser of the basin, erupt-

ing to 5 meters or more. While a majority of the

erupting springs at El Tatio appears erratic, numer-

ous geysers in the Upper Basin appear to have pre-

dictable intervals and durations. 2) The Middle

Geyser Basin, a flat sinter plain, lies immediately

to the south of the Upper Basin. A series of 3–meter

deep pools have frothy, fountain–type eruptions.

The intervals are short (near continuous) and the

eruptions are erratic in duration and height. 3) The

Lower Geyser Basin (or River Group) lies along

the banks of the Río Salado, approximately 2 kilo-

meters downstream from the Middle Basin. At least

ten springs erupt in and near the river to heights of

1 to 3 meters. Some features in the Lower Basin

erupt from within the flow channels of the river

itself, including several underwater geysers whose

eruptions eject sediment onto the riverbank. Very

little sinter accumulation has occurred in this down-

stream river group.

Previous Work

Mentions of geysers in the altiplano were first

included in descriptions of northern Chile by

Bertrand [1885] and Sundt [1909]. In 1921, Ital-

ian engineer Ettore Tocchi [1923] began a study of

the geology and geothermal manifestations to de-

termine their suitability as a source for electricity

production. The next attempt at a detailed study of

El Tatio was by Brueggen [1943]; however, due to

the isolation of the area and difficulty traveling to

the geysers, only a few observations were made. In

1953 and 1960, Dr. Angelo Filipponi, a professor

at the Universidad Técnica Federico Santa María,

Chile, described the characteristics of the hydro-

thermal phenomena at El Tatio and made compari-

sons with the geothermal source and production

facilities in Italy [Filipponi, 1953, 1960; Andres et

al., 1998]. Zeil’s 1956 and 1959 works were the

first to provide a numerical count of features and a

description of the springs’ geochemistry.

The next detailed investigation began in 1968

with the joint work of the United Nations Devel-

opment Program and the Government of Chile.

These investigations included a detailed survey of

the natural features of the basin by Trujillo et al.

[1969], in which over 200 features were mapped.

Continuing investigations were commissioned to

assess the economic feasibility of geothermal elec-

tricity production and water desalinization. These

studies included discussions of regional geology,

structure, and geochemistry [Trujillo, 1969; Lahsen

and Trujillo, 1976; Cusquicanqui et al., 1976]. Six

exploration wells (at depths to 740 meters) and

production wells (to 1,821 meters deep) were

drilled between 1969 and 1974. The majority of

these wells are 2 kilometers south of the Main Ter-

race. In 1974, a pilot desalinization plant was sited

adjacent to the Main Terrace. In 1981, the Chilean

Economic Development Agency (CORFO) con-

ducted a study on the basin concluding that, with

existing wells, El Tatio has electrical production

potential of 15 to 30 megawatts [Andres et al.,

1998]. In March 2002, no wells were discharging

and no geothermal electric production facilities

were in place at the field. The abandoned desalin-

ization equipment still stands within 100 meters of

El Tatio’s tallest geyser (T25). Other recent scien-

tific work has examined El Tatio’s silica deposi-

tion, with an emphasis on geyser eggs and pearls

around thermal pools and geyser cones [Jones and

Renaut, 1997].

Purpose and Scope of This Study

The purpose of the investigation was to inven-

tory and characterize the behavior of the geysers

of El Tatio. The study is restricted to assessing the

geysers themselves; within the limited time of only

three days at the basin, many significant hydrother-

mal manifestations were not inventoried. While at

least 30 perpetual spouters were noted, descrip-

tive information was not collected for all of them.

Based on previous investigations, our inventory

includes approximately 25 percent of the thermal

features in the field. Numerous perpetual spouters,

mudpots, warm springs, solfataras, and fumaroles,

34 The GOSA Transactions Volume VIII

await future investigators. In addition, with our lim-

ited time, we were able to collect only basic, pre-

liminary data for each cataloged feature.

For most of the geysers, only one or two closed

intervals were observed. Data presented reflect

these short observation periods and should be evalu-

ated accordingly by readers. In addition, the be-

havioral data represent a three–day snapshot of

conditions at the basin. Seasonal climactic varia-

tions, seismic effects, and anthropogenic interven-

tion are just a few of many factors that could greatly

affect data presented in this report. During the study,

we obtained only passive information from the ba-

sin and transcribed data to field notebooks; no water

or rock samples were collected. During our visit to

the geysers, no other people (guides, tourists, or

workers) were at the basin. Thus, the cultural com-

ponent of names and history of various features

were not collected. According to local guides in

San Pedro, the larger geysers and cones and sev-

eral of the pools have been named. However, for

this study, individual features are presented with a

code assigned in the field. Where possible, we cor-

relate these codes to the Trujillo et al. [1969]

map numbers.

II. GEOGRAPHY

Regional Geography

The geysers of northern Chile are found in the

Atacama Desert, a region of South America known

for being one of the driest places on earth. The

Andes Mountains bound the eastern side of Chile,

with a high plain (altiplano) nestled between the

mountain peaks. The Andes are tectonically active;

volcanic eruptions and earthquakes are common.

The mountains are forming as the Nazca oceanic

plate subducts under the South American continen-

tal plate. Surface hydrothermal activity is present

over a wide area of northern Chile and southern

Bolivia, including several areas containing geysers

or perpetual spouters. The known geyser fields of

Chile include El Tatio, Polloquere, Puchultisa, and

Tuja. Though unconfirmed, geysers and erupting

springs also have been reported at San Andres de

Quiguata near the village Lirima. The Sol de

Mañana geothermal field lies across the interna-

tional border from El Tatio in Bolivia.

The main cities of interest in the Antofagasta

(or Region II) province of Chile, the zone in which

El Tatio is located, include Antofagasta, Calama,

and San Pedro de Atacama. The city of Antofagasta,

with a population of 275,000, is the capital of the

region. Antofagasta is a coastal harbor city that

serves as a shipping center for the mineral resources

produced in northern Chile and landlocked Bolivia.

Calama lies about 300 kilometers northeast of

Antofagasta at an altitude of 2,250 meters. Calama

has the nearest commercial airport for travel to El

Tatio. Calama, with a population of 150,000, is the

service center and residential base for the

Chuquicamata mine that is located 16 kilometers

north of Calama. The mine is one of the largest

copper mines in the world.

Shane Fryer and Weldon Hawkins atop a large

sanddune at Valle de la Luna, near the village of

San Pedro de Atacama. (Photo by Alan Glennon)

35The GOSA Transactions2003

San Pedro de Atacama is about 100 kilometers

southeast of Calama. San Pedro is a small village

of about a thousand permanent residents settled

around an oasis in the Atacama Desert. The village

emerged as a rest on a cattle trail and a stop con-

necting the llama herders of the altiplano with the

fishing communities on the Pacific [Graham et al.,

1999]. San Pedro, at 2,440 meters in elevation, now

serves as an eco–tourism mecca — a springboard

for tours to the Atacama Desert, the Altiplano, and

Andes Mountains. El Tatio, 86 kilometers north-

east of San Pedro, is located at 4,200 to 4,300

meters above mean sea level.

The altiplano, or puna, is a stark region with

unique wildlife. Several types of llama are found in

this area, with vicuña most commonly seen around

El Tatio. Small nocturnal animals, such as chinchil-

las and their relatives, viscachas, also live in this

region. The desert, in many places, is void of veg-

etation. The rocky, reddish volcanic soils are ex-

posed throughout, except where shrubby grasses

and trees grow in wetter areas. Hydrothermally al-

tered soils are widespread in the geyser basin and

throughout the regional linear depression (graben)

extending north and south of El Tatio. The thermal

areas often feature rich, brightly colored algae and

bacterial mats.

“El Tatio”

“El Tatio” comes from the Atacama word, el

tata, meaning “the grandfather.” Volcán El Tatio

lies 10 kilometers southeast of the geyser field.

According to local legend, the Grandfather, the

volcanic mountain, protected the Atacama people

and has provided the force of steam for hundreds

of years [ENTEL Antofagasta, 2002].

Tourism at El Tatio Geysers

Our experiences at El Tatio were quite differ-

ent from those of the typical visitor. We arrived

later, stayed longer, had our own transportation,

took notes, and saw more water than steam from

the geysers. For the normal visitor, tours from San

Pedro to El Tatio leave at 4 a.m. and return by noon,

costing about US$20 per person. Regarding El

Tatio, Lonely Planet stated that the “visual impact

of its steaming fumaroles at sunrise…is unforget-

table and strikingly beautiful” [Bernhardson, 2000,

p. 287].

Another guidebook, The Rough Guide, said of

the El Tatio tourist experience [Graham et al.,

1999]:

First, you drag yourself out of bed in the dead

of the night, with no electric lights to see by;

you then stand shivering in the street while you

wait for your tour company to come and pick

you up at 4 a.m.; and finally, you embark on a

three–hour journey across a rough, bumpy road.

Add to this is the somewhat surreal experience

of finding yourself in a pre–dawn rush hour.

These guidebooks recommended that the morn-

ing is the best time to see the geysers. Tourists typi-

cally watch the sun rise, eat breakfast, view the

geysers, and take a soak in a warm pool before

returning to San Pedro de Atacama. The tour agen-

cies tell tourists that El Tatio is only active in the

cool, early morning when there are tall, billowing

steam plumes. As expected, we found that though

the large steam clouds do diminish as daytime tem-

peratures rise, geyser activity continues through-

out the day unabated.

Tours also typically include breakfast at El

Tatio, often consisting of eggs boiled in hot springs.

Some tourists we spoke to at our hotel said that

their guides served pieces of the hot spring bacte-

rial mats and hot tea and milk warmed with ther-

mal water. Several springs on the Main Terrace

appeared altered for tourism. For instance, spring

T60 had probably been used for cooking—its calm

greenish–brown water had a thick film on its sur-

face and had trash scattered around it. The pool’s

temperature was measured at 43.8oC, with an ad-

joining pool measured at 25oC. These temperatures

were at least 30oC lower than other surrounding,

non–erupting springs.

At El Tatio, there are no boardwalks or desig-

nated roads. Unfortunately, footprints and tire

tracks are found all over the field. In fact, some

sediment–filled spouters lie in the middle of tire ruts.

Many springs had been vandalized with rocks

jammed into their vents; one of the larger cones

had a metal rod, trash, and rocks stuffed into its

vent. We removed artificially placed rocks and

pebbles from at least ten Main Terrace springs.

36 The GOSA Transactions Volume VIII

Many of these geysers erupted to greater heights

after their obstructions were cleared. Given its gen-

erally unmanaged, unprotected status, it is prob-

able that large amounts of geysersite and sinter

pearls have been removed over the years. Overall,

even though subjected to a great deal of abuse, the

appearance and intensity of activity within the field

is extraordinary.

Getting Around in the Basin

No roads from San Pedro to El Tatio or within

El Tatio itself are paved. With its approximately 10

km2 area, the main geyser areas are within 3 kilo-

meters of one another. Tire tracks from other ve-

hicles are visible throughout the basin and roads to

drilled wells are obvious. The entire length of the

Main Terrace is accessible by road, although we

walked along the banks of the river to visit the

springs downstream along the Río Salado (Lower

Geyser Basin). Although no trail existed, it was a

relatively easy walk. A manmade dam–like struc-

ture, possibly a weir, was located just upstream of

the lowest spring group. The presence of the dam

likely indicates the existence of a nearby road with

easier access to the area; the road would likely be

on the south side of the river. Some of the Río

Salado could be waded, since it flows as a shallow

(less than a 50 centimeters deep), braided river

throughout much of the basin. Only a visit to the

Lower Geyser Basin or to a thermal swamp above

the wells required traveling more than 2 kilome-

ters from the Main Terrace. A series of roads at the

drilled wells lead upward to the thermal swamp and

its perpetual spouter. The roads were built for geo-

thermal drilling, and require a high–clearance ve-

hicle; they also easily could be walked. Although

El Tatio Geyser Basin poses the safety hazards of a

typical major hydrothermal field, navigating within

the basin is relatively straightforward.

III. HYDROGEOLOGIC SETTING

El Tatio Geyser Field is located in northern Chile

on the western flank of the Andes at an altitude of

4,200–4,300 meters. The boiling point of water at

the Upper Geyser Basin is 86.3oC. Though hydro-

thermal manifestations occur over a 30 km2 area,

the primary geyser field comprises only 10 km2.

Other smaller thermal areas have been noted south-

east of the geyser area at altitudes greater than 4,600

meters.

El Tatio is situated in the Altiplano–Puna Vol-

canic Complex. Surface thermal manifestations are

located on the upper levels of the sunken block

called the Tatio graben, which is oriented north–

south for approximately 20 kilometers. The gra-

ben is limited to the west by the horst of Serrania

de Tucle–Loma Lucero and may be limited to the

east by the modern volcanic chain that reaches alti-

tudes above 5,500 meters [Lahsen and Trujillo,

1976; de Silva and Francis, 1991]. The horst and

graben originated in a Pliocene extension that was

largely responsible for the uplift of the Andes. El

Tatio is set on ignimbrites and lavas of the upper

Cenozoic overlying a basement of Mesozoic sedi-

ment. Silicic volcanism has occurred in the region

for at least 10.4 million years [de Silva and Francis,

1991]. The hot water of the basin is mainly con-

fined to two aquifers, which are overlain by rela-

tively impermeable formations. The Puripica and

Salado ignimbrites, forming the lower aquifer, are

overlain by the impermeable Tucle tuffs. Another

aquifer spanning the central, southern, and south-

eastern region of the basin is formed in the Tucle

dacite, which is overlain by the impermeable Tatio

ignimbrite [Cusicanqui et al., 1976].

Preliminary tritium data for thermal waters

within El Tatio Geyser Basin yielded an age of 15

to 17 years at discharge [Cusicanqui et al., 1976].

In contrast, geochemical dating at Yellowstone in-

dicates that the water ejected by Old Faithful Gey-

ser today fell as precipitation approximately 1100

years ago [Rye and Truesdale, 1993]. The likely

source basin for the Tatio water is an area 15 to 20

kilometers east and southeast of El Tatio, although

the topography of the region may cause the water

to travel twice that distance. The rate of water

movement has been estimated at about 1 kilome-

ter/year [Cusicanqui et al., 1976]. The Sol de

Mañana thermal field is located 30 kilometers east,

southeast of El Tatio Geyser Basin. It is likely that

the El Tatio and Sol de Mañana hydrothermal fields

are both fueled by the Pastos Grandes and Cerro

37The GOSA Transactions2003

Guacha caldera systems, with Sol de Mañana be-

ing closer to the thermal source and El Tatio being

a lower elevation distal discharge location [Healy

and Hochstein, 1973; Lahsen and Trujillo, 1976].

Spring discharge from El Tatio Geyser Field

coalesces to form the headwaters of the Río Salado.

The river flows westerly out of the basin, through

a narrow gorge penetrating the Serrania de Tucle

Horst. Discharge of the Río Salado varies by sea-

son from 250 to 500 liters/second [Lahsen and

Trujillo, 1976]. These measurements can roughly

be compared to a range between the discharges of

Yellowstone’s Excelsior Geyser of the Midway

Geyser Basin (223 liters/second) and the Upper

Geyser Basin (518 liters/second) [Allen and Day,

1935; Rinehart, 1980]. Previous investigations at

El Tatio have denoted an average thermal water

pH of 7.2 [Lahsen and Trujillo, 1976], denoting an

approximately neutral basin.

IV. METHODS

For this investigation, a geyser is defined as a

hot spring in which eruptive activity is induced by

boiling at depth within a plumbing system that forc-

ibly ejects water out of the vent in an intermittent

fashion [White, 1968; Bryan, 2001]. A perpetual

spouter is a hot spring that ejects water out of its

vent or pool with continuous eruptive activity.

In order to inventory and characterize the erupt-

ing springs of El Tatio, a combination of handwrit-

ten notes, Global Positioning System (GPS) loca-

tions, temperatures from a digital thermometer, still

photographs, and video were collected during the

three–day visit in March 2002. Working in the ba-

sin from the northeast to southwest, a two–person

team took notes about each feature. For each fea-

ture exhibiting geyser–like behavior, the feature was

assigned a code number. The feature’s latitude and

longitude, temperature, interval, duration, eruption

height, and any other notes concerning unusual

characteristics or behavior were then collected. GPS

coordinates were obtained as close to the erupting

vent as possible (within 1 meter horizontal and ver-

tical) using a Garmin GPS III Plus handheld unit.

Horizontal (degree, minute, decimal minute) and

vertical (elevation in meters, with reference to mean

sea level) locations were obtained in the WGS 1984

coordinate system; these data were recorded “raw,”

as non–differentially corrected. For the report’s

maps, initial positions were adjusted to reflect data

from existing maps, satellite imagery, and relative

feature locations in field sketches. For many of the

features, vent and runoff channel temperature data

were obtained, in degrees Celsius, using a digital

thermometer. For most features, due to the preva-

lence of activity and time constraints, only two or

three closed intervals were observed. It is likely

that longer observations would show the geysers’

behaviors to be more complex.

As two people inventoried and collected GPS

locations, another person videotaped each feature,

while the fourth individual conducted reconnais-

sance. Digital video was collected using a JVC GR–

DVL815U mini–DV digital camcorder. In all, over

six hours of video were taken at El Tatio, captur-

ing the eruption of over 100 springs. Each of the

four team members had a camera and several hun-

dred still photographs were taken within the basin.

With our team’s limited time in the basin and the

unexpectedly large number of true geysers, numer-

ous perpetual spouters, mudpots, non–boiling

springs, solfataras, and fumaroles were not inven-

toried.

Upon returning to the United States, field notes

were transferred to a Microsoft Excel spreadsheet.

Careful analyses of the field video and still photo-

graphs allowed the spreadsheet and notes to be

verified and supplemented. In particular, the digi-

tal video provided the team with a method to de-

velop detailed descriptions of both eruptive activ-

ity and feature appearance. Maps of the basin were

created by importing name, location, and behavior

data into the Environmental Systems Research In-

stitute (ESRI) ArcInfo 8.3 Geographic Information

System (GIS). A basemap of the basin was created

by digitizing portions of topographic maps (Cerros

de Tocorpuri and Toconce) from the Instituto

Geográfico Militar [1985, 2001b] and further en-

hanced with NASA Advanced Spaceborne Ther-

mal Emission and Reflection Radiometer (ASTER)

data. An Instituto Geográfico Militar [2001a] to-

pographic map of Mauque, containing the

38 The GOSA Transactions Volume VIII

Puchultisa thermal area, was also digitized and

added to the GIS. Given the close proximity of fea-

tures compared to the resolution accuracy of

sources, maps produced for this report are best

suited for relative positioning and locating features

in the field.

In the field at El Tatio, we used a map of ther-

mal features by Trujillo et al. [1969]. Before the

trip, Scott Bryan provided a list of feature num-

bers from the Trujillo et al. map that had been re-

ported as geysers. Unfortunately, the density of

springs made identification of individual features

on the Trujillo et al. map difficult. Nonetheless, the

map provided a reference to major spring groups

and facilitated general navigation. Once the GIS

was created, we attempted to reference our field

numbers with the Trujillo et al. feature numbers.

Using the ESRI ArcView Image Analysis exten-

sion, the Trujillo et al. map was georeferenced to

the basemap. Overall, the density of thermal fea-

tures decreased our ability to correlate specific

numbered points from the Trujillo map. However,

general spring groupings are apparent and consis-

tent.

V. DISCUSSION AND FUTURE RESEARCH

Investigations at El Tatio Geyser Field have

determined that it contains at least 100 erupting

springs. With geothermal energy production and

other exploitation impairing the major geysers fields

throughout the world [Allis, 1981; Collar, 1990;

Hroarsson and Jonsson, 1992; White, 1998; Sorey,

2000; Bryan, 2001], El Tatio stands as the third

largest geyser field on earth and the largest geyser

field in the southern hemisphere. The greatest num-

ber of geysers remains in the hydrothermal basins

of Yellowstone, USA and Dolina Geizerov, Russia

[Bryan, 2001]. With 80 or more, El Tatio’s geysers

account for approximately 8 percent of the world’s

active geysers. In addition, at least seven features

previously reported [Trujillo et al., 1969] as gey-

sers were not visited. While many geysers and erupt-

ing springs were inventoried in this study, there are

hundreds of other thermal manifestations at El Tatio

to be documented, precisely mapped, and described.

Additional mapping is necessary to gain greater

detail, including observing more closed intervals,

examining interrelationships among features, and

updating behaviors that have changed since this and

previous studies. Detailed maps of all features, not

just the geysers, should be completed with higher–

grade GPS units and applying differential correc-

tion or carrier–phase processing to the data. High–

resolution satellite imagery can also provide an ef-

fective mapping tool for the area. A thermal fea-

ture inventory may be useful to evaluate the effects

of previous and future hydrothermal drilling on the

region.

Previous information reported that the geysers

were only active in the morning. El Tatio tours typi-

cally arrive at the basin in the cool, early morning

hours when tall steam plumes hide the geysers’ rela-

tively short eruption heights. We observed sustained

geyser activity throughout our visit to El Tatio.

There was no abatement in activity for any length

of time within any part of the field. Although activ-

ity was consistent, geyser eruptions were observed

to be relatively short in height. Of the erupting

springs cataloged, the mean spouting height is 69

centimeters. Of the true geysers cataloged, the erup-

tions averaged 76 centimeters. A total of 31 gey-

sers in the basin erupt to at least a meter; of these

geysers, 13 have eruptions greater than a meter in

height. Compared to Yellowstone and Dolina

Geizerov, which both have a dozen or more gey-

sers that erupt to 50 meters and greater, El Tatio

geysers are small. The causes behind the short

heights are unknown. More research is needed to

determine if the heights at El Tatio are related to

the plumbing system, the heat source, or other fac-

tors.

Many questions remain and numerous research

avenues exist for the El Tatio geysers. Additional

examination into the timeframe for the development

and history of the activity of El Tatio, along with

further tritium dating, are needed. The relationship

between El Tatio and other Andean thermal areas,

such as Sol de Mañana, should also be examined

and quantified in future research. With its location

in an active volcanic arc, opportunities exist to

monitor relationships between seismic and volca-

nic activity and the field’s hydrothermal behavior.

39The GOSA Transactions2003

In addition, El Tatio’s high altitude location within

an exceptionally dry desert, create an extreme habi-

tat for microorganisms. Microorganisms within

other extreme environments, like the springs of

Yellowstone, have been known to exhibit useful and

financially marketable characteristics. Moreover,

hydrothermal systems may be a “cradle” for early

biosphere evolution, as thermophilic life may have

the characteristics of the common ancestor of life

on earth and other planets [Farmer, 2000; Walter

and Des Marais, 1993; Farmer and Des Marais,

1994].

With its vigorous activity and rare display of

geysers, El Tatio Hydrothermal Field is a unique,

world–class natural resource. We hope this initial

report will provide footing for researchers to de-

velop a better understanding of this remarkable lo-

cation.

PART II. SPRING DESCRIPTIONS

UPPER GEYSER BASIN OVERVIEW

The Upper Geyser Basin (or Main Terrace) lies

near the floor of a gently sloping valley and is char-

acterized by widespread, well–developed sinter ter-

races (Map B, below; see also Map A). The scene

within the basin is stark. The broadly sloped flat of

gray and white is punctuated by a handful of active

and inactive geyser cones. During cold tempera-

tures, steam is emitted from hundreds of crevices

and vents. During warmer weather, viewing the area

from a distance, it may appear that very little activ-

ity is occurring. However, a closer look reveals that

the Main Terrace is always highly active. Numer-

ous small spouters are in continuous eruption, sev-

eral handsome pools bubble gently, and many of

the largest geysers are usually nearing eruption.

Map B — Upper Geyser Basin (Main Terrace)

40 The GOSA Transactions Volume VIII

Within the Upper Geyser Basin of El Tatio, gey-

sers surround the visitor.

Next to the broad flats of the geyser basin, the

surrounding hills and mountains provide a contrast

of color and scenery. To the west, north, and south,

tall brown hills with scrubby grass line the basin.

These steep hills are covered with reddish soils and

have large boulders strewn along their slopes. The

red soils are tempered by hints of green and yellow

from grasses and stubby plant life. A wide, broad

break in the hills to the southeast reveals the pass

down out of the mountains. In the foreground of

the pass, numerous steam plumes from the Middle

Basin are visible low in the valley. Commanding

the view to the east are the tall, snow–capped vol-

canoes of the Andes. The distant high–elevation

mountains appear a shadowy blue.

The Upper Basin is the largest of the fields

(spanning 5 km2) and contains the greatest number

of erupting springs. Though the Main Terrace ex-

tends into and down the valley to the Middle Ba-

sin, the primary zone of geysers stretches along a

narrow band. The band follows a northeast–south-

west lineament about 500 meters long and 100

meters wide. No less than 50 true geysers are in

this small zone. Besides possessing the greatest

number of geysers within El Tatio’s three main ba-

sins, many geysers in the Upper Basin appear to

have predictable intervals and durations.

Descriptions follow roughly from the northeast

to southwest. With its small area and high concen-

tration of springs, most Main Terrace features do

not lend themselves to clear groupings. However,

the springs’ characters do change throughout the

basin, with springs in close proximity often main-

taining a similar character.

UPPER GEYSER BASIN, MAIN TERRACE

GROUP U–I

T5a (Suspect Geyser and Fumaroles)

In the far northeast zone of geyser activity, T5A

is an elevated gray–white sinter terrace 3 meters

high, spanning an area of 30–by–30 meters. Sitting

atop the terrace is a large, steep–sided, highly

weathered geyser cone. The cone is oblong–shaped

and 1.5 meters high. With its crest approximately 3

meters above nearby features, within the eastern

portion of the field, the terrace and cone are a domi-

nating presence. Although we did not take detailed

notes about the feature, Alan Glennon climbed to

its top to assess its eruptive potential. Upon closer

inspection, Alan found the feature not only highly

weathered, but it also appeared to have been sub-

ject to explosive force. Large cracks had ripped

open a portion of the cone, but its main vent was

still intact. The feature’s throat was approximately

15 centimeters in diameter. Unfortunately, several

rocks had been lodged 50 centimeters down the

vent. Regardless, below the rock jam, a loud belch-

ing churning sound could be heard. The vent itself

was moist and hot with steam.

Approximately 20 meters to the northeast of

the steep geyser cone, the sinter of the terrace meets

the slope of the hill to the north. At the intersec-

tion, two deep, dangerous–looking, steep–sided rift

craters are present.

T5b (Geyser)

Along the western base of the steep cone lies a

small, round pool 20 centimeters deep and 50 cen-

timeters wide. The pool occasionally sends radiat-

ing ripples along its surface as steam bubbles im-

plode at depth. A deep thumping underground could

be felt on the surface. Over a period of 10 minutes,

the ripples increased. The pool began a slightly more

vigorous overflow and weak splashing to 10 centi-

meters began. The splashing lasted about a minute

before the pool level dropped approximately a cen-

timeter and activity ceased.

T5c (Perpetual Spouter)

This is an attractive 1.5–meter high white sin-

ter mound with a diameter of 2 meters. The mound

gently slopes downward such that it is about twice

as wide at ground level as at its vents. Water spurts

nearly perpetually to 1 meter from at least two vents

on its top. Three quarters of the mound is smooth

and the other portion is rough and filled with jagged

holes. Much of the mound is covered in orange and

light brown–colored bacteria (or perhaps mineral

deposition). Much of the runoff flows east. The

41The GOSA Transactions2003

nearby ground is composed of smooth, white sin-

ter surrounded by small gravels.

T5 (Perpetual Spouter)

T5 is a small perpetual spouter that splashes to

5 centimeters from a vent 20 centimeters wide.

T6 (Geyser)

T6 plays from a 1–meter tall, 2–meter in diam-

eter, white mound with occasional spurts to 10 cen-

timeters for 5 seconds. While no major activity was

observed, it appears to have larger eruptive poten-

tial. Vigorous, agitated boiling can be seen 50 cen-

timeters down in the cone. A hole in the cone’s side

has developed as a secondary vent. Water in the

spring rises and falls, but only occasionally did it

rise high enough to splash outside its cone. There

is some chance that the secondary vent and nearby

small perpetual spouters are robbing the geyser of

energy, but not enough is known about the feature

to develop informed conclusions.

T7 (Perpetual Spouter)

T7 is a cluster of 4 vents covered in green al-

gae on a dry, white 40–centimeter tall mound. Ac-

tivity is apparently perpetual, with spurts to 5 cen-

timeters.

T18 (Geyser)

T18 is one of several vents located on a 3–meter

long light gray sinter mound. Most of the vents

gurgle and hiss as small frying pans. The smooth

mound is only 10 centimeters tall and 10 centime-

ters wide at its largest. The area around the mound

serves as a splash pool for T18. Beaded sinter de-

posits and other pebbles are scattered about the

area.

T18 is a small geyser that splashes to 40 centi-

meters from a tiny vent along a rift line on the low

sinter mound. The geyser erupts for 1+ minutes

every 15 to 20 minutes. When not erupting, only a

meter–wide zone of wetness hints at the geyser’s

existence. Otherwise, not even a puff of steam is

emitted from its vent. Eruptions begin quickly and

consist of splashing pulses, alternating between 20

and 40 centimeters tall.

T9 (Perpetual Spouter)

T9 is a small, typical El Tatio perpetual spouter.

It perpetually splashes to 20 centimeters from a 20–

centimeter deep, 25–centimeter in diameter pool.

A brick–like rock, now covered in sinter, has fallen

into the vent.

T10 (Perpetual Spouter)

T10 perpetually boils vigorously to 10 centi-

meters from a small pool. Both T9 and T10 are

located in a small flat area just slightly higher in

elevation than the geysers to the south. The flat

area is covered with pebbles, gravel, and sand.

GROUP U–II

T12, T13, T14, T17,

and possibly T15 and T16,

are a complex of interre-

lated geysers. During our

observations, activity

within T13 and T14 were

closely related. As T13

ended its eruption, T14 be-

gan steaming intensely and

erupted 50 seconds after

T13’s end. We noticed that

at the end of an eruption of

either feature, both would

commonly simultaneously

Rhonda Pfaff at Spring T5c. (Photo by Shane Fryer)

42 The GOSA Transactions Volume VIII

steam lightly. Their eruptions also appeared to af-

fect the eruptions of the complex’s major feature,

T12, and vice versa. In addition, T17 and T12 also

appeared to have sympathetic eruptions and steam

phases. The features have relatively short intervals

and durations and detailed observation may prove

or disprove these hypotheses. In January 2003, Dr.

Randall Marrett, Associate Professor of Geo-

sciences at the University of Texas at Austin, con-

ducted a multi–day investigation of this spring

group. His findings have not yet been published.

A shallow, half–moon–shaped linear depression

lies immediately south of the T12/13/14 complex.

The feature was noted because of the suspicious

zone of wetness around it. A couple of small frac-

tures are vent possibilities. Further observation may

show the feature to have eruptive potential.

T12 (Geyser)

T12 is a geyser that erupts from a sinter–rift

complex. It appears to be the dominant geyser in a

zone of several interrelated small geysers. The vent

is located at the eastern base of the sinter mound.

The current vent appears to be developed along

the remnants of a geyser cone that has been cracked

through its middle and is now heavily weathered.

The geyser erupts up to 1.5 meters from a vent on

the ground surface at the front of the rift crack.

The play is vigorous, and during larger eruptions,

a layer of water radiates to the northeast for ap-

proximately 3 to 4 meters. The discharge flows over

a sinter apron and onto the sandy gravel beyond.

Steam increases from the overlying rift and water

weakly splashes from the primary vent in the pre–

play. The eruption lasts less than 2 minutes and

occurs on an interval of about 15 minutes.

T13 (Geyser)

T13 is a small geyser 4 meters northwest of

T12 and is located on the sinter complex. It erupts

from a gray crack and splashes to 20 centimeters

for 2.5 minutes about every 15 minutes. Its play

consists of continual splashes ejected as a wide,

thin ribbon of water. It is likely to be closely re-

lated to the other geysers on the sinter complex,

especially T14. At the conclusion of a T14 erup-

tion, T13 typically begins steaming lightly.

T14 (Geyser)

Prior to eruption, steam billows out of a small

crack (less than 10 centimeters wide) on a mound

2 meters from T12. Eruptions observed typically

occurred within a few minutes of the conclusion of

an eruption of T13. The crack and mound have a

reddish–orange color. The eruption splashes clear

water to 50 centimeters for 1.5 minutes. The play

is at full volume and height after only a few sec-

onds of thin spurting. The eruption ends over sev-

eral seconds as volume, height, and splash inten-

sity decrease. Quickly, water is no longer visible at

the surface. The interval ranges from 3 to 15 min-

utes.

T15/T16 (Geyser)

T15 and T16 are two adjoining fountain–type

spouters that splash clear water to 10 centimeters

nearly perpetually. The pools are located on top of

a small sinter mound. The runoff channel has or-

ange bacteria in it. The geyser plays for several

minutes, with an interval of 4 minutes.

T17 (Geyser)

T17 is a small geyser that erupts from a gray

sinter crater measuring 75 centimeters across and

30 centimeters deep. The vent at the bottom of the

crater is about 5 centimeters in diameter. A light

gray sinter crust lines the splashdown area around

the crater. Clear water vigorously splashes to 50

centimeters for 9 minutes every 5+ minutes. Water

rapidly fills the crater half–full and then gradually

rises to overflowing during the eruption. When the

eruption is finished, the pool’s surface becomes still

and the pool empties quietly. The pool is completely

drained 30 seconds after the eruption’s last splash.

T19 (Geyser)

T19 is a geyser that erupts from a shallow cra-

ter to heights of 1 to 1.5 meters. One of the more

significant geysers of the Upper Basin, T19’s erup-

tions consist of a surging, but sustained, fountain

of frothy water. Its vent is located on a short, broad

terrace. The vent is surrounded by a flat, platy sin-

ter splashdown ring and its runoff flows south down

the steeper side of its terrace. A black, softball–

sized rock was located a meter east of the vent.

43The GOSA Transactions2003

The geyser erupts for 3 minutes every 20 to 23

minutes.

T20 (Perpetual Spouter)

T20 consists of a round, non–erupting pool and

a ragged, splashing vent 25 centimeters away. The

pool is about a meter across and 10 centimeters

deep. The pool’s rim is encrusted in white and tan

sinter and has a silty, tan–colored bed. A softball–

sized rock has been jammed into the pool’s vent.

The adjacent erupting vent perpetually splashes to

10 centimeters from a jagged hole. A wet, dark–

brown–colored splash area extends 50 centimeters

from the erupting vent. A 5–centimeter wide run-

off channel carries its small discharge a meter be-

fore the flow disappears into sand and gravel.

T21 (Perpetual Spouter)

T21 is a 2–meter long white–gray mound with

10+ vents that sputter perpetually to 5 centime-

ters. The mound is banded gray and white with al-

ternating wet and dry areas of sinter. A round non–

erupting pool lies in sand and gravel about 3 meters

north of the mound.

T22 (Geyser)

T22 is a very unusual, 50–centimeter tall, spiny

sinter mound. It has at least 20 vents of pencil–

sized diameter, out of which water sizzles for 2

minutes, every 5+ minutes. The eruption gains full

strength within 30 seconds, with water spitting up

to 30 centimeters vertically from several vents.

Other vents shoot water short distances at many

angles. The eruption slowly wanes over the next

minute and a half. Eventually, only steam and a quiet

sizzling sound can be heard. The steam persists for

30 seconds before leading to a 5–minute period of

complete quiescence. There are two small runoff

channels extending from opposite sizes of the

mound. Intricate geyserite makes up the mound and

Weldon Hawkins at Spring T19. Springs T23

and T23a are visible in the background. (Photo

by Rhonda Pfaff)

The unusual, multi-vented geyser, Spring

T22. (Photo by Rhonda Pfaff)

44 The GOSA Transactions Volume VIII

immediate area. Strips of thin sinter radiate in a

few places farther from the mound indicating splash

areas of individual vents. The color of the sinter

ranges from whites to grays and dark browns.

GROUP U–III

T23 (Geyser)

T23 is a very steep, 1.5–meter tall, dark brown

and orange–brown cone that has a nearby dry,

white–colored twin cone (T23A). T23 nearly per-

petually splashes from a 30–centimeter wide vent

at its top. Several periods of minutes had markedly

less activity (for instance, splashing every several

seconds to less than 10 centimeters). During most

of our visit, splashes commonly reached 40 centi-

meters, with occasional droplets reaching a meter.

The splashes often discharged enough water to send

a bath of water down all sides of its cone. Along

with the T5c, T23 is one of the only large continu-

ously wet geyser cones observed in the basin. Pho-

tographs from February 2000 by Cyril Cavadore

show the cone of T23 completely dry with no steam.

Another tourist photograph showed a tourist seated

atop its dry cone. Though its durations and inter-

val are unknown, it appears that the duration, at

least, is days. Given the photographic record, the

geysers’ intervals are likely to be days long, also.

T23a (Geyser)

Twenty meters west of T23, T23a possesses a

cone of similar shape and height (1.5 meters tall

and steep sided). However, unlike its twin, the cone

is completely white and dry. Several rocks and a

metal rod have been stuffed down its vent. A Feb-

ruary 2000 photograph by Cyril Cavadore shows

the cone wet and several small springs along its

base overflowing. Randall Marrett reported T23a

active in January 2003 (with T23 inactive). When

active, the geyser splashes 0.5 meters over its rim

several times per minute. The geyser’s interval and

duration is days. The twin features (T23 and T23a)

display an apparent exchange of function. Observ-

ers, so far, have noted only one of the springs ac-

tive at a given time.

A small runoff stream flows between the two

twin cones. Downstream, along its banks are sev-

eral small boiling springs and perpetual spouters.

Seven smaller, broad sinter mounds lie along the

stream’s downstream banks.

T24 (Geyser)

T24 is a geyser that erupts from a 2–meter wide

cone with a 40–centimeter wide vent. The cone is

light–to–medium gray–colored sinter and is 40 cen-

timeters tall. The geyser splashes to a meter and

forms a pool in the depression of its cone. Splashes

infrequently reach 2 meters and land far beyond its

elevated sinter mound.

The duration of the

splashing is less than 35

minutes, with an interval

greater than 3 minutes.

A series of rising and

falling water levels were

observed in the vent be-

fore the eruption, but fu-

ture observation is nec-

essary to characterize its

exact behavior.

T25 (Geyser)

In terms of height

and beauty, T25 is the

star of El Tatio. The

geyser, the tallest ob-

The cones of Spring T23a (left) and Spring T23. (Photo by Cyril Cavadore)

45The GOSA Transactions2003

served at El Tatio, can reach heights greater than 5

meters. The geyser is located on top of a wide,

multi–tiered terrace 1.5 meters high. The southern

portion of the terrace is a meter–high scarp cov-

ered with active columnar sinter. The runoff chan-

nel is composed of thousands of shallow

microterraces. Beaded sinter and oncoids are lo-

cated everywhere. The geyser exhibits lots of pre–

play, consisting of slow building of water volume

and height from its 30–centimeter tall mound.

The preplay builds for at least 30 minutes be-

fore the full eruption begins. The geyser plays for

up to 15 minutes every 2 or more hours, although

there was typically small splashes up to

30 centimeters at all times the geyser was

observed. A short steam phase and sev-

eral minutes of inactivity follow its ma-

jor eruptions. During major eruptions,

water is ejected nearly vertically to 5

meters, although a smaller amount of

water is shot at a 45o angle to heights of

1.5 meters. During one eruption, the

water phase appeared to taper into a

longer steam phase. At the end of this

type of eruption, the jet of water became

increasingly narrow. The thin jet of wa-

ter may reach heights exceeding 8

meters. Over several minutes, a narrow

column of steam replaces the water. Of

six eruptions seen, this higher type of

eruption was observed only once. The

geyser lies approximately 100 meters

away from the abandoned desalinization

well. A temperature of 62oC was taken

from the surrounding splash pool that

has orange bacteria growing in it.

Visitors in January and May 2003 re-

ported hours to days of perpetual spout-

ing from T25.

Shane Fryer and Rhonda Pfaff taking a temper-

ature measurement at Geyser T25. (Photo by Alan

Glennon)

Storm clouds darken the sky behind Geyser T25. Machinery

remains from an abandoned project to test steam-driven

thermal water desalinization. (Photo by Alan Glennon)

46 The GOSA Transactions Volume VIII

GROUP U–IV

Below a 60–centimeter tall, 1–meter wide el-

evated hot spring pool, lies a series of small craters

arranged linearly. Typically vertical perforations in

the sinter, 40 centimeters in diameter and 30 centi-

meters deep, these craters are aligned primarily

along three different trends. Each of the lineaments

originates at the elevated hot spring pool and radi-

ate outward. The first trend is approximately aligned

toward the east. Only one or two craters exist along

the trend, but they head toward a dilapidated, broad

geyserite cone 20 meters away. Two geysers are

located at the worn geyser cone. The second trend

stretches southeast toward T25. Along this trend

are numerous craters. Nearly all of the small cra-

ters emit steam and boil vigorously in the subsur-

face. Several of these craters periodically erupt to

short heights as geysers. The third lineament trends

to the southwest. Several steaming craters and small

vents are present, but only one’s boiling would pe-

riodically reach above the ground level. The trend

continues outward toward a region of small vents.

The vents trend roughly toward T36 and include

numerous multi–colored warm springs with tiny

vents (less than 5 centimeters in diameter), several

steaming 20–centimeter deep craters, and tiny boil-

ing springs.

T27 (Geyser)

T27 is a geyser that plays from a broad, heavily

worn cone, 60 centimeters tall and a meter wide at

its top. The top of the geyser cone funnels down

40 centimeters to a circular vent 15 centimeters

wide. Most of the vent is clogged with pointy rocks

and dry gravel, although a gap along one side of

the vent provides an opening for eruptions. Erup-

tions play as angled surges splashing to 40 centi-

meters. The eruption rarely plays water outside of

the cone’s funnel and only a small area of the total

geyser vent is wetted by the eruption. One eruptive

duration lasted 5 minutes with a minute pause in

activity. Other observations found the feature to

be perpetual.

T34 (Geyser)

At the northwest base of T27’s cone is a small

geyser that typically plays to 10 centimeters, but

occasionally splashes to six times that height. The

geyser plays from a shallow, dark–colored funnel

on the ground level amongst sinter gravel. The fun-

nel itself appears worn and some of its sinter is bro-

ken. The play is nearly perpetual with momentary

pauses. During a typical eruption, very little water

flows away from the cone; however, during occa-

sional 60–centimeter tall splashes, water often lands

beyond its sinter funnel and onto the nearby gravel.

The geyser’s runoff channel is an area of moist

gravel, but the wet area extends at least 6 meters

from the little geyser. From its appearance, the fea-

ture occasionally sends significant but short–lived

washes of overflow down its channel.

T28 (Geyser)

T28 lies along the southern base of the elevated

cone of a 1.5–meter wide, non–erupting, steaming

hot spring. The elongated vent creates a jagged cut

laterally along the base of the cone. The vent is a

meter long and 30 centimeters wide. A primary vent

plays often and sends splashes up to a meter. Two

satellite vents occasionally play in concert to 10

centimeters or more. The feature appears erratic

but almost perpetual, with seconds to a minute of

nearly continuous eruption followed by a pause of

up to 20 seconds. The vent is angular and jagged,

possibly indicating that the feature is relatively new,

had a particularly explosive genesis, or has long

periods of quiescence.

T29 (Geyser)

T29 lies along the lineament of craters toward

T25 approximately three meters from southeast of

the elevated hot spring. The steaming jagged cra-

ter, approximately 30 centimeters wide and deep,

plays to 50 centimeters above ground level. Sev-

eral observed closed intervals showed the play to

last 30 seconds with an interval of approximately 2

minutes. The crater steams gently throughout its

quiet period.

T30 (Geyser)

Six craters in a 3–by–3 meter area include sev-

eral small, apparently erratic geysers (T30, T31,

and T33). The largest of the group is T30. T30

possesses a 50–centimeter wide, 30–centimeter

47The GOSA Transactions2003

deep crater. Similar to the other features in the im-

mediate vicinity, the crater drops off at ground level

with vertical walls and has an irregular shape. Dur-

ing three closed intervals, T30 played to 30 to 40

centimeters above ground level with a 5 second

duration and an interval between 15 and 25 sec-

onds. Very little water is discharged by the erup-

tion.

T31 (Weak Geyser)

T31 is a very small and apparently erratic gey-

ser playing from a narrow, 1–meter long vent.

Though boiling can be heard constantly in the vent,

an occasional splash to 20 centimeters may occur.

During our observation of the area, a single weak

splash would occur from the southern portion of

the vent not more than once per minute. Overall,

compared to the nearby activity, the eruption is very

easy to miss. Normally, the geyser is a gently steam-

ing crater.

T33 (Weak Geyser)

T33 is another very small and apparently er-

ratic geyser. It plays from a 30–centimeter in diam-

eter, erratically shaped vent along the lineament

between T28 and T25. A single splash, lasting no

more than a second occurs every 30 seconds or

more. The weak splash commonly plays to 20 cen-

timeters above ground level.

T33b (Fumarole)

Although not seen in eruption, this feature may

be more important than the several other minor fea-

tures in the area. T33B is an elongated vent sub–

parallel with the T28/T25 lineament. The 20–cen-

timeter deep crack has a tiny vent that hisses a 5–

centimeter spray. The misty spray’s height remains

well below the ground surface. Although not as

impressive as the other features in the immediate

vicinity, T33B has a small, but distinct, runoff chan-

nel. A layer of small gravel lies ten centimeters from

the vent in the upstream direction. It appears to be

a high water mark for the feature. Though it may

have eruptive potential, for now, it is classified as a

small fumarole or dormant vent.

T32 (Geyser)

T32 is fan–shaped depression that slopes down

to a point 30 centimeters below the ground sur-

face. The vent is 20 centimeters wide at the bottom

of the depression. Rocks have been jammed into

the vent such that the small eruptions occur only

through openings in the obstruction.

The eruptions barely splash above

the rock jam, with none observed

to splash above ground level. Erup-

tions occurred during occasional

rises in water level that reveal highly

convective boiling leading to weak

splashing to 10 centimeters. The

activity appeared relatively erratic

with rising and lowering of water

to occur over several minutes and

splashing to last only several sec-

onds.

T26 (Geyser)

T26 is a fountain–type geyser

that erupts from an L–shaped pool,

1.5 meters in length. The pool is 5

centimeters deep, with a gray mud

bottom. The rim of the pool is lined

with reddish–orange bacteria. Play

Small Geyser T29 (middle left) plays in Spring Group U-IV. An

afternoon storm hides the hills behind a weak, steamy eruption of

Geyser T25 (background). (Photo by Shane Fryer)

48 The GOSA Transactions Volume VIII

to 40 centimeters comes from two primary vents,

which are 10 centimeters in diameter. The splashes

are formed as the clear water rhythmically surges

in and out of the vents every second. A third vent

forming the bottom leg of the “L” is separated from

the main area of the pool by a small natural bridge

at the water level. Water in this 20–centimeter wide

vent rhythmically surges. A tiny fourth vent lies 2

meters north of the pool and erupts in concert with

the other vents (to heights of 20 centimeters). The

eruption goes for a few minutes with periods of

quiescence occurring in all vents lasting only a

couple of seconds. In short, the spring is active

nearly all the time.

GROUP U–V

T35 (Geyser)

T35 is one of the more significant geysers in

the basin. It appears to be a consistent player with

a well–developed, often–used runoff channel, con-

sistent durations and predictable intervals. T35

erupts as a fountain from a vent flush to the ground

50 centimeters wide. The geyser reaches heights of

1.5 meters during its 1–minute eruption that oc-

curs every 2 minutes. The eruption reaches full

strength within 10 seconds with no pre–play. The

eruption height overall is sustained in a series of

splashy bursts throughout the eruption. After 50

seconds, the height of the eruption starts to decline

and 10 seconds later the eruption has completely

ended. It takes less than 10 more seconds for wa-

ter to drain from the vent. The primary vent is lo-

cated among a series of other smaller vents. The

geyser erupts from only one vent, but it overflows

and spills into several of the surrounding small holes.

T36 (Perpetual Spouter)

T36 is an attractive spouter whose play (up to

50 centimeters) emerges from a 40–centimeter

wide, dark brown–colored cone in the middle of a

10–centimeter high, white, flat sinter–mound. The

lower mound, which is nearly circular, is approxi-

mately 1.5 meters in diameter. The lower mound is

very wet from splashes. Orange and dark brown

bacteria are growing in some areas of the lower

mound, primarily around the outer rim of the flat

mound. A small pool (30 centimeters in length and

less than 2 centimeters deep) has formed over a

portion of the lower mound. There are many gey-

ser pearls and other small silica deposits in the pool.

T37 (Geyser)

T37 is lo-

cated near the

road along the

northern side of

the Main Ter-

race. Several

small perpetual

spouters are lo-

cated in the vi-

cinity, but only

T37 was seen to

have intermit-

tent activity. The

gurgling play is

up to 10 centi-

meters high and

is nearly per-

petual. Quiet

pauses last only

Spring T35. (Photo by Shane Fryer)

49The GOSA Transactions2003

a few seconds. During the momentary pause, the

water level in the feature drops before gurgling and

splashing begins again.

T38 (Geyser)

T38 is a muddy, oval–shaped pool level to the

ground. Four linear vents are present in the small

pool. The pool measures less than a meter in length

and is about 5 centimeters deep. T38 is near the

main road that runs through the upper basin. All

the vents splatter to 20 centimeters for about 30

seconds. When in eruption, the splashes of clear

water occur from different vents while the pool is

overflowing. At the conclusion of the eruption, the

pool drains completely. Its interval is about 2 min-

utes.

T67 (Geyser)

T67 is a spring with a 10–centimeter deep pool

at the vent. The vent was clogged with rocks that

had probably been placed in the vent by tourists.

The rock nearest the surface oscillated with the

splashing of the water during the eruption. When

two rocks were removed, the pool drained. After

inventorying several other features, we noticed the

vent had begun splashing to 40 centimeters. In ad-

dition, it had started to overflow and wet its small

runoff channel. The eruption lasted for at least 10

minutes, but nothing is known about its interval. A

ring of platy, rough gray sinter is

present around the pool. Beyond

that, the ground is composed of red-

dish–sandy deposits. A couple

meters away, two tiny features spurt

to a centimeter.

T67b (Geyser)

T67B plays from a 20–centime-

ter deep pool that is about a meter

wide. A meter to the west, a 5–cen-

timeter hole acts as a satellite vent.

The geyser itself is located immedi-

ately north of the road that many

tourist vans take into the basin. Only

cursory observations of the geyser

were made, but the activity was quite

intriguing. The activity starts from

a gently boiling pool and small splashes begin along

the pool’s northern side. The side of pool muffles

the splashes and they reach only about 10 centime-

ters. After a minute of this activity, the splashing

ends with a weak, but agitated, rocking of the pool.

Over the next 30 seconds, boiling begins along the

pool’s southern side. The southern side of the pool

has a ragged, overhanging sinter ledge that begins

enduring most of the boiling. After several vigor-

ous boils, a steeply angled splash begins jetting 30

to 40 centimeters from under the sinter ledge and

tangent to the pool. The splashing increases in in-

tensity for several seconds before the satellite vent

begins a constant boil to 10 centimeters. The activ-

ity sends a thin overflow of water across the road.

The eruption lasts around 4 minutes before return-

ing to a somewhat agitated boiling along the pool’s

northern edge. Nothing is known about its interval

other than the activity was not repeated within 5

minutes of observation.

T39 (Geyser)

T39 is a sediment–filled geyser that, unfortu-

nately, lies in the middle of tire tracks on the main

road through the upper terrace. The vent and pool

together are 50 centimeters across and are com-

pletely choked with small gravels and pebbles. The

small feature spouts to 10 centimeters for several

seconds with an interval of less than a minute. When

Spring T36. (Photo by Shane Fryer)

50 The GOSA Transactions Volume VIII

in eruption, activity in a series of frying pans 50

centimeters away intensifies.

T40 (Perpetual Spouter)

T40 is a small spouter that splashes from a 20–

centimeter wide vent. The pool splashes perpetu-

ally up to 10 centimeters.

T41 (Geyser)

T41 is a small geyser that spurts to 40 centime-

ters (at least 20 centimeters above ground level)

from a hole that is 20 centimeters in diameter. There

is a dry sinter–encrusted circular area reaching a

meter from the vent, indicating that the geyser could

possibly erupt higher than observed. The vent and

splash ring are encrusted in beaded sinter. T41

splashes for approximately 2 minutes, with an in-

terval of greater than 5 minutes. The vent dries in

between eruptions, although the splash ring remains

wet. The geyser is located 1 meter away from the

crater of an old, large (1 meter in diameter, nearly

1 meter tall) dormant, reddish–colored cone.

T42 (Intermittent Spring)

T42 overflows and gurgles from a hole 25 cen-

timeters across for 30 seconds. Another vent a meter

away has similar behavior every 3 minutes.

T43 (Geyser)

T43 is a crater level to the ground coated in

dark green and black algae. The coloration was

unusual among the other spouters. Splashing

reaches heights of a meter for several minutes with

a very short (only seconds long) interval. The sur-

rounding splash area extends a meter out from the

vent, with similar dark–colored bacteria growing

in all directions. There are no gravels or sediments

located within the splash area, possibly indicating

a high water mark. The outer rim of the splash area

has some orange bacteria. A small, round hole lo-

cated within the splash area occasionally spurts a

few centimeters.

T44 (Geyser)

From above, T44 resembles a gray, open–faced

seashell. The inner vent is nearly black. The top of

the vent is flush to the ground, although the open-

ing extends 20 centimeters beneath ground level.

Frothy water surges once every few seconds from

the 30–centimeter long sinter–covered vent with a

sound that is reminiscent of rhythmic ocean waves

breaking on the seashore. One side of the vent gently

and smoothly slopes downward, while the oppo-

site side is jagged like a half–conch shell. The bot-

tom of the vent is full of fist–sized rocks and pebbles

blocking the geyser’s full eruption power. The sur-

rounding splash area and reddish–colored sandy

sediments are dry. The frothy eruption reaches to

10 centimeters and lasts more than a minute. The

interval is greater than 5 minutes. A 10–centimeter

in diameter hole—a satellite vent—adjacent to the

main opening, occasionally splashes as well.

T45 (Geyser)

T45 is a geyser on a meter–tall, gently sloped,

white sinter mound. Sinter beads are present on

the mound. Several small rocks that were choking

the 5–centimeter wide, round vent were removed,

but several still remain. The eruption has an angled

component and reaches laterally 70 centimeters.

The east side of the geyser is wet, while the west

side remains dry. A splash area at ground level has

a coating of dark film. The geyser erupts for 1

minute at intervals of greater than 2 minutes.

GROUP U–VI

T46 (Geyser)

T46 is a geyser that produced a vigorous erup-

tion after we removed ten rocks and pebbles that

had been stuffed by vandals into its 10–centimeter

in diameter vent. The vent and splash area were

slightly damp and there was little activity (play to

less than 10 centimeters). Cleared of blockage, the

geyser plays to 1 meter, with an angled eruption

emanating from an opening on the side of a low,

gray sinter mound. Water from the geyser’s erup-

tion spills over into a lower splash area. Light and

dark gray beaded sinter is present, with little or no

coloration in either the vent or splash pools. The

eruption lasts a minute or more with a 15+ minute

interval.

51The GOSA Transactions2003

T47 (Geyser)

T47 is a small geyser that erupts with weak

splashing to 10 centimeters. Only one eruptive epi-

sode was observed. The duration was less than 10

seconds. Its small, wet splash cone implies that the

interval is relatively short.

T48 (Geyser)

T48 has a smooth, 10–centimeter in diameter

vent that extends 10 centimeters beneath the ground

before being obstructed by several rocks. The rocks

appear to have been artificially placed in the vent,

so we attempted to clear them (most could not

safely be removed). The geyser erupts up to 20

centimeters. There is a light gray sinter splash ring

around the vent and a handful of pebbles scattered

about it. The geyser has periods of quiescence min-

utes long. Eruptions observed consisted of a series

of splashes every few seconds.

T49 (Geyser)

T49 is a somewhat–round pool 50 centimeters

in diameter. The pool’s western edge is bounded

by a low, lumpy sinter accumulation that overhangs

the pool and creates an irregularly shaped western

shore. The pool’s vent is located below the irregu-

lar side 10 centimeters underwater. Eruptive activ-

ity is typically weak and consists of small surges to

5 centimeters. Otherwise, during its quiet period,

boiling at depth creates small ripples along the

pool’s surface. Orange bacteria line the eastern rim

of the pool. A tiny runoff channel flows from T49

into T50.

T50 (Geyser)

T50 is a fountain–type geyser that splashes from

two distinct vents. The vents share the same small

pool. The shallow pool, which is oval–shaped and

1 meter across, has a dark green tint, with orange

bacteria around the rim. Both vents commonly

splash to 50 centimeters. Two frying pans splatter

in T50’s overflow channel. The intensity of boiling

rises and falls and brief total pauses were observed.

The duration is greater than 1 minute with an inter-

val of seconds.

T51 (Geyser)

T51 is a geyser located immediately south of

the road through the upper terrace. Its eruption

consists of a continual gush of water, with heights

up to 1 meter. Compared to the other small gey-

sers of the basin, its eruption creates considerable

discharge. Its pool and splash area, which is about

1 meter across, is full of small rocks. The pool is

level to the ground. When the geyser is not in erup-

tion, the pool is drained and its vent gently steams.

The duration is less than 5 minutes and the interval

is less than 15 minutes.

T53 (Geyser)

T53 is a small geyser that splashes to 15 centi-

meters from a 7–centimeter vent. The vent is cov-

ered in dark gray sinter. Adjacent to the geyser is a

low, white sinter mound. Three small rocks were

removed from the vent while it was not in erup-

tion. The interval is approximately 10 minutes.

T54 (Weak Geyser)

T54 is an obscure vent on an area of flat sinter

pavement. The 3–centimeter wide vent was noticed

when it suddenly began splashing and bubbling

water to 5 centimeters. The weak splashing only

lasted a few seconds before ending. No runoff was

produced. Further observation found the feature

to erupt at intervals of less than a minute.

T55 (Two Geysers)

T55 is a geyser that intensely splashes to 10

centimeters from a crack vent 3 centimeters across.

The crack, encircled by a smooth sinter splash zone,

is ringed by an apparent high water mark radiating

20 centimeters from the vent. Another small, wet

crack with an elongated sinter splash zone is lo-

cated 20 centimeters east. Its duration is less than

10 seconds. The interval is unknown, but the fea-

ture was seen in eruption again within 15 minutes.

With such a small geyser, any intervening eruptions

could have easily gone unnoticed.

T56 (Geyser)

T56 is a fountain–type spouter whose pool is

lightly scalloped around the edges. The pool is dark

gray and 10 centimeters deep. Fifty–centimeter high

52 The GOSA Transactions Volume VIII

splashing occurs from a vent in the center of the

pool. The geyser’s duration is short with long quiet

pauses of gentle boiling. The runoff channel has

bright orange bacteria present.

T57 (Geyser)

T57 is a small spouter that splashes to 5 centi-

meters from a hole 5 centimeters across. Located

in an area of flat sinter crust, its vent is obscure

until it erupts. Eruptions only last a few seconds

with an interval close to a minute.

T58 (Hot Spring)

T58 is a hot spring with a 1–meter long de-

pression that is 20 centimeters deep. Two vents

containing 72oC water were seen to be rising dur-

ing 15 minutes of observation. The elongated de-

pression has a thin coating of orange sinter.

GROUP U–VII

T59 (Geyser)

T59 was observed erupting up to 30 centime-

ters from its 30–centimeter tall, light–colored sin-

ter cone. The round geyser vent is level with the

ground, but is encircled by a short geyser cone. A

wet area of dark gray deposits or bacteria encircles

the geyser. Weak, brief splashes occur every 30

seconds. During 15 minutes of observation, occa-

sional puffs of steam and intermittent rising and

lowering of water levels in the crater were observed.

From the size of the cone and nearby well–main-

tained sinter apron, the geyser may have a history

of more vigorous activity. Given that two other

large geysers exist nearby (T63 and T51) with rela-

tively long intervals, perhaps this geyser also pos-

sesses a long interval between majors. In all, the

observed activity of T59 was frustrating. Several

times, when it appeared the water, steam, and ac-

tivity rose enough to preface an eruption, the wa-

ter level dropped, and the geyser became quiet.

T60 (Warm Spring)

T60 is a spring that may have been used by

guides to cook for tourists. T60’s calm water was

greenish–brown–colored with a heavy film on its

surface and there was some trash scattered about

the spring. The pool’s temperature was measured

at 43.8oC, with an adjoining smaller pool measured

at 25o C. These temperatures are at least 30oC lower

than other surrounding, non–erupting springs.

T61 (Geyser)

T61 is a rectangular pool that vigorously laps

back and forth, eventually surging and splashing

up to 60 centimeters from its orange–colored cra-

ter. The pool is sunk 10 centimeters from the sur-

face. A smaller vent one meter away emits weak

splashes to 10 centimeters. As the eruption ends,

the intensity of the surging in the main vent de-

creases and the water level lowers. A relatively dry

sinter–splash area encircles the vents. While always

agitated, the spring definitely displayed minutes of

stronger splashing and overflowing activity (and

increased activity in its satellite vent). This activity

is followed by minutes of weak rocking of water

within its pool and small splashes to 5 centimeters.

T62 (Perpetual Spouters)

T62 erratically splashes to 10 centimeters. Qui-

escent periods several seconds long were noted,

but not convincing enough to classify it as a gey-

ser. The hill northwest of T63 creates a 60–meter

wide alcove with several perpetual spouters,

mudpots, and fumaroles. T62’s irregularly shaped,

2–meter wide pool is scalloped and undercut around

the sinter–encrusted rim. Its runoff temperature was

measured at 84.6oC. The primary vent is obstructed

by rocks, which likely reduces its eruption height

to 30 centimeters. Two perpetual spouters that erupt

to 10 to 30 centimeters are located within 20 meters

to the north and west. T62 lies on the northern side

of the main terrace primary road, opposite T63 and

the majority of the main terrace geysers. About 10

meters up the slope east of T62, an interesting bright

red–orange pool has several splashing frying pans

along a slump on its uphill side. The pool’s water

shares the same red color. Above this pool and 50

meters farther to the east lies a lone, loud fumarole

on a gentle slope. From the fumarole along the hill-

side, most of the main terrace can be seen.

53The GOSA Transactions2003

T63 (Geyser)

T63 is one of the major geysers of El Tatio

Geyser Basin. It erupts to 3+ meters for 15 min-

utes with an interval greater than 2.5 hours. Steam

increases from the vent and the cone begins to splash

before an eruption begins. There are only about 10

seconds of splashing outside the cone before the

water reaches its full height. The cone, which stands

60 centimeters tall, is dry at the beginning of the

eruption. During the eruption, water gradually spills

over the cone and into the surrounding splash pool.

The runoff spills north, west, and east. Water also

drains into a nearby hole at ground level (T64).

Tourist postcards of T63 show what appear to be

bacteria covering its cone and splash area. The bac-

teria range in color from tans and browns close to

the orifice and deep reds, oranges, and near–blacks

a meter or more from the vent. Although the play

shown on the postcards is similar to what we ob-

served, some type of change in activity or water

chemistry has occurred.

T64 (Dormant Vent)

T64 is a dormant vent that is 2 meters east of

T63. The vent is level to the ground, such that run-

off from T63’s eruption drains into it. A well–main-

tained sinter apron, a short splash cone rim, and

intricate beading suggest that this feature may have

eruptive episodes.

T65 (Geyser)

T65 is a geyser that splashes

to 15 centimeters from a series

of three vents that lie in a 1.5–

meter line. Rocks fill one of the

vents.

T66 (Geyser)

T66 is a large pool, approxi-

mately 7 meters wide that has

quick surges to 3 meters. The

water is clear and there is a

brown, sandy mound a meter tall

on its northern side. The dura-

tions of the surges are only sev-

eral seconds long with an ob-

Dormant Vent T64 (foreground) and Spring T63.

(Photo by Shane Fryer)

Looking west at Spring T63 in eruption. (Photo by Shane Fryer)

54 The GOSA Transactions Volume VIII

served interval of more than an hour. During our

visit, we noticed the pool constantly steaming. Oc-

casionally the pool exhibits particularly intense,

heavy steaming. During one of these periods, we

noticed a low, white boiling surge in the pool. As

we watched, the boiling surge rose to 3 meters. A

few seconds of smaller surges were noted, as well

as very heavy steam, before the pool went back to

its normal boiling state. We walked to the pool in

hopes of further activity, but no other similar surges

occurred. The pool is located 100 meters south of

T63.

T67c (Geyser)

T67c plays from a 1–meter wide, round, meter–

deep pool. The pool has several different types of

activity that appear erratic, but are nearly perpetual.

The spring has momentary quiet modes. At those

times, the pool is about a centimeter below over-

flow. These times of quiescence are short–lived.

The typical eruption consists of either splashing with

overflow, splashing without overflow, or overflow

without splashing. Splashes occur from the center

of the pool and typically reach 30 centimeters.

Larger splashes reach a meter. Runoff from the

spring spills down two runoff channels, but a lower

runoff channel flows more often. The pool is lo-

cated immediately north of the tourist road on the

Main Terrace; its runoff channel crosses the road.

Longer eruptive episodes can play uninterrupted

up to a minute. The longest period of quiescence

was only about 30 seconds. Most eruptions consist

of a couple of splashes followed by a short 10 sec-

ond pause.

UPPER GEYSER BASIN,

OTHER PORTIONS

GROUP U–VIII (FAR UPPER GROUP)

Separated from main Upper Geyser Basin ac-

tivity 500 meters up the valley to the northeast, the

Far Upper Group features several kinds of land-

scapes. Rolling foothills surround the broad, flat

area. A great deal of the thermal area is covered in

green moss and scrub brush, much like a thermal

marsh. Small, shallow, often bubbling, hot springs

and runoff channels break up the patches of moss,

although some areas of moss are brown and dying.

Other areas of the Far Upper Group are character-

ized by a desolate landscape void of vegetation,

with volcanic boulders the sizes of cars strewn about

the area.

A few geysers exist in the Far Upper Group,

although most of the play observed reached heights

much less than a meter. There are, however, sev-

eral intense mud volcanoes. Two of them are lo-

cated on a hillside. The larger of the two continu-

ously and vigorously boils watery, light brown mud

up to 1 meter from a steaming crater 5 meters long,

3 meters wide, and 3.5 meters deep. The smaller

mud volcano (about 1 meter in diameter and 1 meter

deep) has formed in a hole downhill from the larger

volcano. The vigorous splashing nearly reached the

ground surface and had formed reddish–brown mud

stalactites under the rim.

There were also several mudpots located within

the area. An oblong–shaped, dark–gray 5–meter

long mudpot was nearly dry; mud cracks were

present throughout the depression. The only “plop-

ping” was found in a watery spot in its center. Many

of the hot springs and hot streams had patches of

cream–colored, sudsy foam on their surfaces. The

small springs of this area often had scalloped sinter

encrustations around their pool rims. Very little

bacteria mat growth was observed within the Far

Upper Group, although a few pools did have run-

off channels with red and orange bacteria present.

Inventorying the Far Upper Group in detail, due

to the possibly unstable nature of the soggy moss

and marsh, was dangerous. Therefore, only a por-

tion of the area was visited up close on foot. Much

of the basin was viewed at a distance from the hill-

sides.

T3 (Geyser)

T3 erupts up to 1 meter approximately every 4

minutes for 15 seconds from a series of three small,

reddish–colored vents. The largest and primary vent

is 20 centimeters across, with water splashing from

a 10–centimeter tall, rough, white and dark gray

sinter mound. The eruption begins with simulta-

neous splashes from the primary vent and a smaller

adjacent vent on a shorter, although still connected,

55The GOSA Transactions2003

mound. Water spills down the mound from the sec-

ondary vent. Splashing begins 15 seconds later from

a third vent, which is an elongated rift tangent to

the mound. The eruption creates an overflow stream

about 1 meter in length. The geyser is located in an

area several meters long comprised of rough, grav-

elly white and gray sinter. Two other mounds (one

up to 50 centimeters tall) are present, although no

eruptive activity was observed from these nearby

features. The sinter area is surrounded by green

moss and short, stubby grasses.

T4 (Geyser)

This geyser consists of a main vent and a sec-

ondary vent. From a distance, we saw a meter erup-

tion from the main vent, possibly a major. Up close,

we observed intense, 20–centimeter bursts from the

main vent. The main vent is a rounded, crater–like

pool that is 50– centimeters deep. The geyser has a

well–developed, smooth–bottomed runoff channel,

which, like the rim of the main pool, is encrusted

with scalloped, gray sinter. There are also thin run-

off lines radiating from the pool. One side of the

pool has a 20–centimeter tall, overhanging sponge–

like sinter deposit that is reddish–colored in loca-

tions where water splashes against it. The second-

ary vent alternates activity with the main vent. The

pools undergo a series of filling and emptying in an

8–minute (possibly minor) eruption duration. The

interval is greater than 14 minutes.

GROUP U–IX (MIDDLE VALLEY GROUP)

A spring cluster 700 meters east of the Main

Terrace was not visited. At least twenty hydro-

thermal manifestations are represented on the

Trujillo et al. [1969] map. At least a dozen more

features are noted downstream of this group in the

portion of the valley south of the Main Terrace.

Both of these vicinities can be seen in the distance

from the Main Terrace, but appreciable steam was

not observed.

LOWER GEYSER BASIN OVERVIEW

The Lower Geyser Basin (or River Group) lies

along the banks of the Río Salado, approximately

2 kilometers downstream from Middle Basin (Map

C; see also Map A). In all, at least 20 true geysers

are located in the area. Following downstream from

the Middle Basin, the river becomes increasingly

channelized between steep hills. The river through-

out the group flows with a gray–colored bed. The

river’s color contrasts with the red soils of the hill-

sides, white and yellow hydrothermally altered

ground, and many colors of the hot springs. At wide

points, the river reflects the surrounding hills and

sky.

For the first kilometer, the river remains a wide,

braided stream. Only a half–dozen features exist in

this zone, but they are of significant size (T68, T70,

T71). An additional 500 meters downstream, the

river takes a sharp southern meander loop. Along

the banks of this southern loop, a spring group ex-

ists that we did not visit. Steam and fumaroles are

visible in the distance. After the loop makes its

northern curve, it flows northwest. As it flows

northwest, a tightly packed grouping of spouting

springs exists. The area of vigorous activity lies

within a 100–by–100 meter area. Several springs

erupt in and near the river to heights of 1 to 3

meters. Numerous springs in the Lower Basin flow

or erupt from within the flow channels of the river

itself, including several underwater geysers whose

boiling deposits sediment on the riverbank. Two of

the larger geysers (T72/73) erupt at steep angles.

Very little sinter accumulation has occurred in this

downstream river group; many of the geysers ap-

pear to be erupting from fractures and fissures in

the bedrock itself. In this area, the Río Salado is a

much narrower stream, but still maintains a braided

character. Except when very close to a boiling

spring, the sound of the river overwhelms many of

the sounds of hissing, steaming, and splashing.

From the Lower Geyser Basin, the surround-

ing hills dominate the view to the south, west, and

north. Their reddish–brown soil is dotted with low

green and yellow scrub. Reddish boulders are

strewn about along many of the slopes. Above simi-

lar low hills to the east, the same tall, dark snow–

capped Andes stretch toward the north and south.

56 The GOSA Transactions Volume VIII

LOWER GEYSER BASIN, RIVER GROUP

GROUP L–I

T68 (Geyser)

T68 erupts from three ragged, red sinter–coated

vents comprising a complex approximately 8 meters

long and 5 meters wide. A nearby fourth vent is

filled with cloudy hot water and did not respond to

the geyser’s eruption. The geyser is located at the

intersection of a gulley draining from the north to-

ward the Río Salado valley. Immediately above the

vent complex, a contact between a conglomerate

and white silicic rock exists. The white rock unit

contains small flecks of garnets. Eruptions appear

to occur in series at the geyser, with both minors

(less than 1 meter) and majors (about 1 meter)

noted. However, with only six eruptions observed,

the geyser’s true behavior is unknown. Eruptions

consist of simultaneous splashing of frothy water

from each of the three vents for approximately 1

minute. The interval during several closed inter-

vals was timed at 3 minutes. The eruption ends with

all three vents draining completely with only slight

steam being emitted. Within 30 seconds, the steam-

ing ends. Steaming begins again about a minute

before an eruption.

T68b (Perpetual Spouter and Well–Developed

Sinter Terrace)

Located 30 meters east of T68 near the bottom

of the valley slope, a perpetual spouter (T68B)

erupts frothy, but clear, water. The splashdown area

surrounding the spouter is covered in dark green

(nearly black) bacteria, with some bright oranges

Map C — Lower Geyser Basin (River Group)

57The GOSA Transactions2003

along the outer rim and runoff channels. A grape-

fruit–sized rock covered in dark bacteria blocks part

of the vent’s opening. A small, bubbling vent lies

within the dark green runoff channel 50 centime-

ters downstream of the main vent. Fifty meters

south, a white and gray, 1–meter high, 2–meter wide

silica terrace is located on the northern bank of the

Río Salado.

T69 (Perpetual Spouter)

T69 is a perpetual spouter located just barely

above water on a small island in the Río Salado.

The vent is, at most, a few centimeters above river

level, and would be submerged during wet peri-

ods. Activity occurs from a small vent at the level

of the island. The spouter’s activity can be most

easily seen from the banks of the river on the path

downstream from T68. Clear water fountains a

consistent 30 centimeters.

T70/T71 (Two Geysers)

T70 and T71 geysers are located along the river

bank on the south side of the Río Salado immedi-

ately before the river takes a southern bend. T71 is

closest to the river and erupts as a surging fountain

to a meter or more for a minute. Its height, inter-

val, and duration are all greater than T70, which is

located on a red–sinter bank about one meter to

the southeast. While T71 remains quiescent between

eruptions, minor activity seems to be occurring

continuously at T70. Small splashes to 10 centime-

ters occur erratically, but eventually activity in-

creases until the activity reaches a meter or more.

The increase in activity at T70 appears to induce

T71 to eruption. Although closely related, the gey-

sers also exhibit independent activity. A small area

of hydrothermally altered soil lies immediately to

the south of the geysers. A large fumarole can be

seen steaming from a red soil–lined crater that lies

about 50 meters up the hill south of the two gey-

sers.

GROUP L–II

T72 (Geyser)

T72 is a geyser located on the slope of the north-

ern bank of the Río Salado about 10 meters north

of the observed river flow. Water shoots from a

ragged, red rocked vent. Outside the splash zone,

the soil near the vent is white and light red. Con-

tinuous jetting, up to 2 to 3 meters, is angled (about

30ofrom vertical) east and south toward T73. T72

has a more defined spray than does T73. Dark bac-

teria cover the wet areas. T72 has a smaller pool

than does T73, although its flow becomes

channelized before it reaches the primary Río Salado

flow (approximately 10 meters away during the

observed flow conditions). Considering the long

duration of eruptions, the geyser discharges a large

volume of water.

T73 (Geyser and

Several Perpetual

Spouters)

Quick splash pulses

from T73 gush at an

angle 45o from the ver-

tical southerly toward

the Río Salado. These

blasts of water splash

from a 30–centimeter

wide vent on the hill

slope; the splashes com-

monly reach 2 meters.

Several large rocks de-

flect some of the splash-

Looking west toward Group L–II. (Photo by Shane Fryer)

58 The GOSA Transactions Volume VIII

ing, but the volume of water typically inundates

them. The eruptions have formed a 3–meter wide

splash pool that channelizes the flow 20 meters

south into the Río Salado. A thin red sinter crust is

around the geyser vent and all the way down its

flow channel. The crust appears to be at least 10

centimeters thick in some areas. During some of

the particularly powerful pulses, the geyser fans

water from 90o from the vertical to the south to 30o

to the north. As a result, these occasional splashes

were observed to a meter or more outside the

geyser’s northern sinter lining. Several small per-

petual spouters erupting to 10 centimeters were

noted immediately southeast of T73.

T74 (Perpetual Spouter)

T74 erupts from a sinter–lined cauldron about

20 centimeters above the Río Salado’s southern

bank. A sinter crust creates a slight overhanging

edge above its crater. One side of the rounded cra-

ter is open and flows into the Río Salado. Eruption

heights approach the level of the ground surface,

about 40 centimeters above the vent, with occa-

sional droplets reaching a meter. The splashes

mostly are vertical and slightly angled toward the

center of the caul-

dron. The erup-

tion appears to be

perpetual.

T77 (Geyser)

T77 is a large

fountain geyser

that erupts to

heights of greater

than 1 meter. The

pool is located on

the edge of an ex-

ploded geyser

cone. The erup-

tion lasts 1 to 3

minutes, with an

interval of 5 min-

utes.

T78 (Geyser)

T78 is a pool

approximately 50 centimeters in diameter. The pool

is at ground level, but debris piles 10 to 20 centi-

meters high are located near the pool. During its

eruption, water surges and splashes to 40 centime-

ters. No closed intervals were carefully observed,

but field video recorded the feature to have an in-

terval of at least several minutes, with an eruption

lasting more than 1 minute. The intervals and dura-

tions may, in fact, be erratic.

T79 (Geyser)

T79 is a small fountain geyser that plays from a

pool that had dead frogs around it. The eruption

reaches heights of 50 centimeters. The geyser con-

tinued playing while the nearby T77 underwent sev-

eral closed intervals. T79’s play continued for at

least 15 minutes, and noticeably weakened through

the duration. The geyser has a 10 minute quiet in-

terval.

T76 (Four Perpetual Spouters)

Numerous apparent perpetual spouters lie near

the southern shore of the Río Salado north of T79.

At least four were noted splashing or causing surges

into an elongated discharge pool from 10 and 50

Geyser T73 (left foreground) and Geyser T72 (right background).

(Photo by Shane Fryer)

59The GOSA Transactions2003

centimeters high. Almost all of these features have

unique, colorful sinter mounds or overhangs. Their

close relationship to the river undeniably affects

their development and eruptive activity. A careful

inventory of these features would undoubtedly yield

additional small perpetual spouters, and likely small

geysers.

T80 (Geyser)

T80 is a geyser that sprays a thin stream of water

up to 2 meters high. The activity quickly subsides

into a steam phase lasting at least 20 minutes. Simi-

lar to its observed eruption, the geyser’s steam

phase consists of a thin column of steam being force-

fully ejected for about 2 meters before dissipating

into a less organized form. The geyser’s vent, which

is level to the ground, is surrounded by a circle of

gray and red softball to basketball–sized rocks, with

some much larger. These rocks possibly are the

result of a hydrothermal explosion related to the

geyser. The immediate ground is flat, barren, gray

and red. Two meters from the vent, beyond the ther-

mally altered ground, are patches of yellow–green

moss.

T75 (Geyser)

Nearly adjacent to T80, a small splashing gey-

ser erupts to 20 centimeters. It is immediately north-

west of the T80 vent. Similar to T80, the area

around the vent is strewn with softball–sized gray

and red rocks. When this geyser was first noticed,

it was vigorously splashing from a small pool. This

was concurrent with the steam phase of T80. An

inspection from a distance of 70 meters 30 minutes

later noted no activity and no steam. Nothing fur-

ther is known about its activity.

T81 (Fumarole and Perpetual Spouter)

Approximately 10 meters east of T80, a red soil

slump area contains a gentle fumarole. At the base

of the fumarole, a 50–centimeter high perpetual

spouter was observed.

T82 (Geyser)

T82 is an underwater geyser that gently boils

in a shallow, gray, murky pool next to the bank of

the Río Salado. A few handfuls of black and cream–

colored pebbles have been stirred up from the ri-

verbed and deposited on the surrounding reddish–

brown sinter crust. The main Río Salado flow has

been cut off from this area. Boiling reaches up to

10 centimeters. When T82 is not in eruption, the

water is still. The interval is at least 20 minutes and

the duration is at least several minutes.

T83 (Perpetual Spouter)

T83 is located near the upstream tip of the is-

land in the middle of the Río Salado. It is likely a

perpetual spouter, with its eruption partially sub-

merged in the river. The eruption gushes a mix of

water, gravel, and sand to 15 centimeters. Though

the spouter is in one of the two main channels of

the river, the geyser is located on a sandbar. The

water is only a couple of centimeters deep over its

vent. The spouter is located very close to the loca-

tion that T72’s runoff channel enters the Río Salado.

Spring T78. (Photo by Shane Fryer)

60 The GOSA Transactions Volume VIII

T84 (Geyser)

T84 is a completely underwater geyser. Intense

surging, which was observed as high as 1 meter

over the river’s water level, deposits pebbles from

the riverbed onto the surrounding shore crust. The

geyser is located near the northwestern corner of

the island in the middle of the Río Salado. The pel-

let–sized sediments are typically black or cream–

colored and form a 5–centimeter deep layer that

extends on the bank up to 1 meter from the boiling

pool. The geyser’s water is typically murky, due to

the pebbles and particles it is carrying. Two other

adjacent underwater geysers (including T85) are

located within several meters of T84 in the same

deep pool.

T84b (Very Small Geyser)

One meter southeast of T84’s splash area, a

small geyser erupts with weak splashing to 10 cen-

timeters for 10 seconds from two small vents. The

geyser was not observed directly in the field, but

noticed during examination of T84’s videotape. In

fact, during its quiet interval, we actually stepped

right over the geyser without noticing it. T85b’s

vent is one of numerous unremarkable fractures and

small holes spread throughout the island in this

spring area. It is possible that other small geysers

exist in the vicinity, but were not observed. The

geyser’s activity appears to be independent of T84.

Only a single eruptive episode was observed; how-

ever, given the vigorous activity of the area, its in-

terval is likely no more than several minutes.

T85 (Geyser)

T85 is a completely underwater geyser whose

boiling picks up pebbles from the river bottom and

deposits them on the bank. Located 2 meters north-

west of T84 and within the same deep spot in the

river, T85 periodically boils to 10 centimeters. One

splash to 30 centimeters water was seen.

Group L–III

In the northwest portion of the Group II springs

lies a concentration of features in a 20–by–20 meter

area. The small area, part of the Río Salado’s flood

plain, is pockmarked with small craters and

mudpots. These craters are typically 10 to 20 cen-

timeters in diameter and about as deep. Two per-

petual spouters and a number of geysers erupt from

the craters.

T86 (Mud Volcano)

The most distinctive feature in the group is a

50–centimeter tall, 50–centimeter wide mud vol-

cano along the northern shore of the Río Salado.

Mud has been deposited forming a cylinder with

walls about 10 centimeters thick. A small cauldron

of mud boils 70 centimeters down inside the cylin-

der, occasionally splashing mud 10 centimeters or

more out of the cone. A smaller mudpot adjoins

the little volcano, but for some reason has not de-

veloped a cone of its own.

T100 (Geyser)

T100 is comprised of three small 10–centime-

ter deep craters. The craters coalesce to form an

elongated feature that makes a highly distorted “T”–

shape. The entire “T” is no more than a meter

across. Each of the three craters contains a tiny

pool of agitated water. The middle pool is the most

active, with occasional erratic splashes to 10 centi-

meters. The middle pool occasionally offered larger

eruptions. When this occurs, the erratic splashing

increases its frequency and force until it is nearly

constant. The angled play throws water laterally at

least 50 centimeters. The vertical height reaches

no more than 50 centimeters. The duration of the

eruption was erratic, but commonly lasted over a

minute.

T101 (Geyser and Perpetual Spouter)

T101 erupts from a small elongated crater no

more than 80 centimeters long and 50 centimeters

wide. Similar to other craters in the immediate vi-

cinity, it is no more than 20 centimeters deep. The

crater is slightly narrower in the middle and is some-

what shaped like a “Figure 8.” The geyser was not

approached too closely due to dangerous ground,

but water appears to be relatively calm in its crater

during its quiet period. The geyser begins eruption

with an increase in boiling and water level in its

crater. The activity builds for 10 seconds or more

until the pulsing splashes reach a meter in height.

61The GOSA Transactions2003

The play occurs from nearly the entire crater, so

the splashes are typically 50 centimeters in diam-

eter. A glaze of water is sent toward the nearby Río

Salado. Several closed intervals were timed to be-

tween 100 to 220 seconds. Adjacent to T101, to-

ward the river, a perpetual spouter erupts from a

10–centimeter wide crater. Its 30–centimeter high

play looks like a smaller version of the T101 erup-

tion. A few red–lined craters are present to the east

of T101. Of these, the one closest to T101 appears

to occasionally splash within its crater. However,

no water rose above ground level. The next red–

lined crater had a 4–centimeter layer of wet red

mud downstream of its rim. During our observa-

tions, only steam was emitted from its crater.

T102 (Very Small Geyser and Perpetual

Spouter)

Barely a geyser, a small feature exists in close

proximity to a much more impressive perpetual

spouter. The spouter maintains a frothy play to 10

centimeters. Of the two perpetual spouters in the

L–III Spring Group, it is the farther downstream

of the two. Mossy green material is located on a

10–centimeter mound on the spouter’s southeast

side. A tiny feature was noted 50 centimeters north

of the spouter’s main play. Every 10 to 15 seconds,

a tiny vent throws a single, quick splash to 5 centi-

meters. The nearby ground is composed of light–

colored sand and gravel.

T103 (Geyser)

T103 plays from a shallow meter–wide crater.

It is effectively a twin feature with T104. Tilted

bedrock is visible at the bottom of the crater at the

geyser’s vent. A thin coating of gray sinter gives

the geyser a dark color. The geyser is nearly al-

ways erupting. Pauses were infrequent and lasted

no more than 10 seconds. When not erupting, the

crater is completely drained of water. The play con-

sists of frothy, but clear water splashing 30 to 60

centimeters high. The activity of the geyser appears

erratic.

T104 (Geyser)

T104 plays from a shallow meter–wide crater.

The crater is similar in shape and appearance as

T103, except that T104’s sinter is red. Bedrock can

also be seen near its vent at the bottom of the cra-

ter. The geyser plays almost continuously, but sev-

eral complete stops were noted. When not erupt-

ing, its crater is completely drained, with steam

coming from its vent. The play consists of erratic

splashes of frothy, but clear water 60 centimeters

to a meter high. Its duration lasted several minutes

or more between pauses. Quiet periods usually only

lasted several seconds, but a couple of 10 second

pauses were also noted. Similar to its neighboring

springs, the activity appears erratic.

T105 (Geyser)

T105 lies in an obscure area of craters west of

T103. The crater could not be approached due to

unstable ground, but appears to be about 30 centi-

meters across and about 10 to 20 centimeters deep.

The play sends one or two splashes of water to 20

centimeters above the ground surface. Only about

a liter of water is airborne during a single splash

and very little discharge leaves the crater.

T105a (Geyser)

Dwarfed by its larger neighbors, T105a occa-

sionally sends a single, weak splash of water to 10

centimeters above ground level. The small play

occurs from an obscure crater 30 centimeters wide.

The interval is less than a minute. Numerous simi-

lar craters lie within several meters of T105 and

105a.

LOWER GEYSER BASIN, OTHER SPRING

GROUPS

Group L–IV

Another spring group lies north of the vigor-

ous activity of main Lower River Group. From a

quick trip to the group, Shane Fryer reported a

geyser (T98), a suspected geyser (T99), and a pool

complex.

T98 (Geyser)

T98 is a 20–meter wide complex of three

springs, with at least one geyser that erupts from a

2–meter wide vent under a cliff face. Water shoots

62 The GOSA Transactions Volume VIII

1 meter before it hits a ledge. Momentary pauses

were noted in the otherwise continuous play, oth-

erwise nothing else is known about its duration and

interval.

T99 (Hot Spring/Reported Geyser)

T99 is an 8–meter long pool that is about 1

meter deep. The spring has at least ten underwater

vents. Vigorous boiling and fluctuating water lev-

els were observed, but no eruptions seen. This fea-

ture has previously been reported as a geyser

[Trujillo et al. (1969) feature 195]. Near T99, Shane

also reported a deep, meter–wide shaft. During his

quick visit to the area, the water level in the shaft

dropped several meters. No other information is

known about its activity.

Group L–V (Two Reported Geysers)

A spring group reportedly containing geysers

[Trujillo et al. features 98 and 111] is located on a

southern bend of Río Salado, downstream of T70/

71. From T70/71, fumaroles and intermittent steam

were seen. The group was not visited due to time

constraints. Since much of the activity appears to

be south of the river, approach from the southern

bank of the Río Salado may be the best strategy.

Feature 98 on the Trujillo et al. map was re-

ported to be a geyser [Trujillo et al., 1969]. It is

located downstream of T70/71 on the Río Salado.

Approximately 50 meters south of Trujillo et al.

feature 98, is another reported geyser. This spring

is number 111 on the Trujillo et al. map. Both of

these reported geysers were not visited on the

March 2002 trip.

Group L–VI (Three Reported Geysers)

In the upstream areas of the Lower Basin lies

another spring group that has been known to con-

tain geysers. The group lies roughly between the

Upper, Middle, and Lower geyser basins. Due to

time constraints, we were able to visit only a small

portion of the spring group. The group is located

above a 10– to 20–meter high escarpment that pre-

vented us from viewing the group from the Río

Salado. Three features, numbered 168, 181, and

184 on the Trujillo et al. map, have been reported

as geysers. The spring group extends southeast and

down the short escarpment. This small portion of

the group is along the road entering the geyser field.

T1 (Hot Spring Pool)

T1 is a 70–centimeter deep pool next to an

upended rock 30 meters north of a branch of the

Río Salado. The clear, shallow pool is 5.5 meters

wide, scalloped and undercut with temperatures

measured from the bubbling vent at 60.7oC. Sev-

eral bubbles float on the surface of the pool. The

pool has a tan–beige–colored bottom with a nar-

row band of red algae where the deeper pool meets

its runoff channel. The runoff channel has dark

brown and orange bacteria present, but the pool

has relatively little discharge.

Shane Fryer at Spring T2.

(Photo by Rhonda Pfaff)

63The GOSA Transactions2003

T2 (Perpetual Spouter)

T2 plays perpetually to 50 centimeters from a

10–centimeter tall cone on a 1–meter high sinter

mound. Orange bacteria are present on the sinter

runoff apron. The apron stretches in a semicircle,

with a radius of greater than 2 meters. The tem-

perature at the orifice was measured at 80.5oC. Two

nearby vents on 8–centimeter high sinter mounds

boil up to several centimeters in height. The dis-

charge trickles down the mound and into a tribu-

tary of the Río Salado.

MIDDLE GEYSER BASIN OVERVIEW

The Middle Geyser Basin lies immediately to

the south of Upper Basin and is a stark, flat sinter

plane. The geyser activity of the Middle Basin lies

in a zone 400 meters long and 100 meters wide

(Map D; see also Map A). The basin contains at

least ten true geysers. The area of geyser activity is

bounded on the west by a low, flat–topped hill and

a creek on the east; the creek is a major upstream

branch of the Río Salado. Along the creek, a small

dam has been created to form a soaking pool for

tourists. The pool is approximately 30 meters long

and 15 meters wide, with a few perpetual spouters

erupting within a few meters of the pool.

The most prominent thermal features of the

Middle Basin are six deep pools. Only one of these

pools (T90) was not seen to erupt. The other pools

average 3 meters deep and have frothy, fountain–

type eruptions. The intervals and durations for the

pools appear erratic. The area also contains numer-

ous small examples of fumaroles, mudpots, and

perpetual spouters between the pools and creek.

Some of these features may be geysers. One of the

features (T89) exhibited intermittent spouting as a

true geyser. Numerous parallel shallow runoff chan-

nels flow to the north from the pools. A low, long

hill follows to the west of the thermal flat.

Map D — Middle Geyser Basin

64 The GOSA Transactions Volume VIII

Besides the six pools, a widespread region of

thermal activity lies upstream along the main creek

and to the west (over the low hill, in a parallel

creek). These other areas contain numerous hydro-

thermal features, but few geysers. The environs of

these remaining geysers are described with their

individual descriptions.

GROUP M–I

T87 (Geyser)

T87 is a frothy pool with a 1–meter tall ex-

ploded cone on its southern end. The eruptions

occur from an overhung pool. The fountain, which

measures 5 meters across, produces frothy,

“Jacuzzi–like” surges up to 1 meter with an inter-

val of less than a minute. Nearly the entire pool is

frothy at some times in its eruption. The pool ap-

pears superheated and is rarely completely calm.

T88 (Geyser)

T88 is a pool adjacent to the north of T87 that

is separated from T87 by a 1 meter bridge of over-

hanging crust. Its overflow flows northward in a

wide runoff channel. Its surging is likely related to

the activity of T87. Small splashing (up to 30 cen-

timeters) that appears to be independent of activity

within T87 occurs along the overhanging ledge on

the pool’s northern edge.

T89 (Geyser)

T89 is a group of small sputtering, boiling

springs. A shallow pool 50 centimeters across vig-

orously boils and two vents a meter east erupt to

20 centimeters. During observation, the southern-

most spouter erupted for at least 2 minutes with

splashing to 20 centimeters before stopping. When

it stopped, a vent 40 centimeters to the north be-

gan erupting to 20 centimeters. Play continued on

the northern vent for more than a minute. Further

information about its interval and duration are un-

known.

T90 (Hot Spring Pool)

T90 is a handsome 2–by–2 meter pool that was

not seen in eruption, although it is suspected to be

a geyser because of its well developed, wide runoff

channel. In addition, a sinter–lined splash area sur-

rounds the pool and implies, if not eruptive activ-

ity, at least intermittent rises in water level. Con-

tinuous boiling occurs along the pool’s southeast

edge.

T91 (Geyser)

T91 is a pool 2 meters across with half of its

perimeter encircled by white, bumpy sinter depos-

its that radiate out 1.5 meters from the pool’s edge.

The active vent is located on the eastern corner of

the pool. The rim of the sinter next to the pool has

orange and dark–brown bacteria growing along it.

The pool had no distinct runoff chan-

nel. The geyser produces frothy

surges up to 2 meters in height for a

few seconds on an interval of about a

minute.

T92 (Geyser)

T92 erratically produces frothy

surges up to 2 meters from an elon-

gated pool. The undercut pool is 2.5

meters across. Its abundant discharge

flows north through a well–devel-

oped, meandering runoff channel. The

area surrounding the pool is bright

orange and wet to a distance of 1

meter. The temperature during qui-

escence was measured at 83.6oC.

Spring T92. Despite its sudsy, frothy appearance, there is no

evidence that Spring T92ís activity was induced. (Photo by

Shane Fryer)

65The GOSA Transactions2003

T93/T94/T95 (Three Closely Related Geysers)

T93–95 is a group of three fountain geysers

that surround an exploded cone at the base of the

western hill. These geysers now act independently,

although they may at one time have been one gey-

ser. The remnant of the cone is about 1.5 meters in

height and 3 meters in diameter. The cone is golden

brown in color, with some white patches. T94 is

the northern geyser, which splashes near perpetu-

ally to 1 meter from its bluish–colored pool. Its

discharge is channeled northward. The runoff chan-

nel, with scalloped sinter encrustations along its

borders, is about 50 centimeters wide and several

meters in length. The channel has rusty orange de-

posits (possibly bacteria, although the colors do not

vary along the channel), with some cream–colored

patches along the upper rim. The entire pool occa-

sionally appears to use a wide, wet overflow zone

with brown, rusty orange and cream–colored de-

posits. T93 is the eastern geyser, which surges near

almost perpetually to 2 meters. The overflow pool

around T93 had a temperature of 83.5o C. T95 is

the southernmost geyser, with near perpetual surges

to 1 meter.

Immediately south of the geyser complex is a

steaming rock–filled depression. Many of the rocks

in the depression are concreted together by a fine

layer of reddish–orange sinter. The sound of boil-

ing water can be heard under the rocks. It is pos-

sible that the feature has eruptive behavior, but none

was seen.

T96 (Geyser)

T96 is a 25–centimeter tall cone with an irregu-

larly shaped meter–long cauldron. It is located near

the top of the hill and its overflow is radial from

the elevated cone. Water inside the cone appears

to be 2 or more meters deep. This feature was not

observed in eruption. However, a visitor’s (Cyril

Cavadore) February 2000 photograph shows a

small eruption of the feature. The eruption appears

to be a vigorous boiling overflow with a splash to

20 centimeters. During March 2002, a wide, wet

zone surrounding the vent was noted, implying that

the geyser is active. A combination of shallow wa-

ter, mineral deposition, and bacteria create a color-

ful mosaic of dark reds and greens away from the

elevated vent. Its interval is greater than 15 min-

utes. This region has dark ashy soils and volcanic

rocks, ranging from baseball– to car–sized, spewed

everywhere. Yellow scrub grasses are interspersed

throughout the area.

T96b (Intermittent Spring Pool)

About 30 meters to the northeast of T96 is one

of the largest pools in the basin. The 9–by–6 meter

rectangular pool is filled with dark blue water on

the edge of boiling. Parts of the spring have an over-

hanging geyserite crust, but otherwise, the bed of

the pool descends as a cone to a meter–wide vent

at the pool’s bottom. At its deepest, the pool is at

least 6 meters deep. We observed the pool to be

approximately 1 centimeter below overflow. How-

ever, its shallow runoff channel was wet with scat-

Spring T91. (Photo by Cyril Cavadore)

66 The GOSA Transactions Volume VIII

tered moisture and tiny pools. Whether the spring

erupts is unknown, but the spring apparently has

some type of intermittent discharge activity.

GROUP M–II

T97 (Perpetual Spouter, Hot Springs, and

Sinter Terraces)

T97 is a red, iron–colored cone that is located

on a mound. The feature is about 100 meters south

of the Terrace Spring Group along a slope west of

a small stream. This spouter erupts nearly perpetu-

ally to 30 centimeters with an erratic duration. Sev-

eral similar boiling springs were noted on the same

western slope; several are small perpetual spouters.

This feature and one or two others are likely to be

actual geysers.

Downstream of T97 lies an extensive area of

short, white, brown, and orange terraces developed

from non–boiling springs. Several of the taller ter-

races are composed of multiple 10–centimeter high

tiers, combining to a height of no more than a meter.

Though short, the terraces are widespread. The area

follows down the small creek for at least 100 meters

with a width exceeding 20 meters along the way.

The terraces appear to be sinter.

GROUP M–III

A thermal marsh

with two distinct mudpot

areas and at least one

perpetual spouter lies

about 2 kilometers

southeast of the Middle

River Group. The marsh

is approximately 100

meters long, 50 meters

wide and situated in a

ravine. Geothermal well

drilling surrounds the

area. Mudpots that con-

sist of either entirely

black mud or reddish or-

ange mud are inter-

spersed throughout the

vicinity. In the upstream and northern portion of

the swamp, an area of flooded mudpots is sur-

rounded by tall grass and green moss. Along the

southeast end of the thermal marsh lies a perpetual

spouter that erupts clear water to a meter. It is lo-

cated along the bank of a small stream flowing

through the swamp. Its 30–centimeter deep cra-

ter–like vent is surrounded on one side by a leafy

green moss. The other side is open to the nearby

creek. Pebbles and gravel lie on its flat crater floor.

A large vigorous mudpot lies about 500 meters

west of the thermal swamp. The feature is located

south of the road in the same valley as the marsh.

Numerous geothermal wells are visible from the

The pool of intermittent Spring T96b. (Photo by Cyril Cavadore)

A view toward the mudpots near the thermal swamp

of Group M–III. (Photo by Alan Glennon)

67The GOSA Transactions2003

mudpot. The far southern end of the Middle Gey-

ser Group can be seen from the mudpots. By far

the most vigorous mudpot in the basin, the main

area of activity occurs in a 3–by–3 meter cauldron.

Watery red mud is splashed between 50 centime-

ters and 2 meters everywhere in the cauldron. A

couple of meters to the north of the cauldron, an

elongated pool 10 meters long and 4 meters wide

boils gently with a less watery variety of the red

mud. Fifty meters west of these mudpots, a fuma-

role belches steam from a 2–meter deep explosion

crater.

T106 (Geyser and Reported Geyser)

A geyser (probably Trujillo et al. [1969] fea-

ture 35) is located 400 meters southeast of the pri-

mary Middle Group. Its vent is well–hidden within

an area scattered with small ravines, small scrub

brush, gravel, and boulders. The geyser erupts a

stream of water 2 meters high at an angle about

30o from the vertical. The eruption lasts less than a

minute. We originally saw this geyser while driving

from the middle group to the thermal marsh area.

Taking a well–drilling road, we noticed the geyser

erupting, approximately 50 meters from our truck.

By the time we stopped the truck and made it over

to the geyser, the eruption had ended. In fact, when

we arrived at the geyser, not even a trace of steam

remained. Without using

the eruption itself as a

guide, the vent would be

very difficult to find. The

small vent looks like a

small animal’s burrow

near a large rock. Simi-

lar rocks and small ra-

vines make the location

quite nondescript. Luck-

ily, from the middle

group, steam from the

eruption is easily visible.

From the middle group,

having seen approxi-

mately three eruptions in

the distance, the geyser’s

interval was estimated at

15 minutes or more.

The immediate vicinity of this geyser is intrigu-

ing, but we did not have the time to investigate.

The area between the middle group and the ther-

mal marsh has the appearance of a long–dormant

geyser area. Several low, broad mounds appeared

to be dilapidated spring terraces.

Spring number 36 on the Trujillo et al. [1969]

map is a reported geyser. We did not visit the fea-

ture. The road into the basin from the south crosses

a steep–sided ravine where several small springs

can be seen from the road. The reported geyser is

located upstream in the stream valley and access

appears straightforward.

Mudpots within Group M–III. (Photo by Alan Glennon)

A perpetual spouter (unnumbered) in Group M–III.

(Photo by Alan Glennon)

68 The GOSA Transactions Volume VIII

Latitude Longitude Height Duration Interval Description

GROUP U-I

T5a see map see map - - fumarole

T5b see map see map 0.10 1 minute 10 minutes weak geyser

T5c -22.32985000 -68.00951667 1.00 perpetual perpetual perpetual spouter

T5 -22.32988333 -68.00976667 0.05 perpetual perpetual perpetual spouter

T6 -22.32993333 -68.00970000 0.10 5 seconds erratic geyser

T7 -22.32993333 -68.00970000 0.05 perpetual perpetual perpetual spouter

T18 -22.32993333 -68.00988333 0.40 >1 minute 15-20 minutes geyser

T9 -22.32975000 -68.01006667 0.20 perpetual perpetual perpetual spouter

T10 -22.32971667 -68.01010000 0.10 perpetual perpetual perpetual spouter

GROUP U-II

T12 -22.33006667 -68.01030000 1.50 1.25 - 2 minutes <15 minutes geyser

T13 -22.33006667 -68.01030000 0.20 2.5 minutes <14.75 minutes geyser

T14 -22.33011667 -68.01033333 0.50 1.5 minutes 3 - 15 minutes geyser

T15/16 -22.33015000 -68.01035000 0.10 minutes 4 minutes geyser

T17 -22.33000000 -68.01020000 0.50 9 minutes >5 minutes geyser

T19 -22.33023333 -68.01023333 1.50 3 minutes 20-23 minutes geyser

T20 -22.33016667 -68.01021667 0.10 perpetual perpetual perpetual spouter

T21 -22.33023333 -68.01016667 0.05 perpetual perpetual perpetual spouter

T22 -22.33045000 -68.01013333 0.30 2 minutes 5 minutes+ geyser

GROUP U-III

T23 -22.33058333 -68.01040000 0.40 days days geyser

T23a see map see map 0.50 days days geyser

T24 -22.33095000 -68.01061667 1.00 35 minutes >3 minutes geyser

T25 -22.33105000 -68.01115000 5.00 15 minutes 2 hours + geyser

GROUP U-IV

T27 see map see map 0.40 5 minutes >1 minute geyser

T34 see map see map 0.10 seconds seconds geyser

T28 -22.33090000 -68.01168333 1.00 <1 minute seconds geyser

T29 -22.33090000 -68.01165000 0.50 30 seconds 2 minutes geyser

T30 -22.33106667 -68.01163333 0.40 5 seconds 15-25 seconds geyser

T31 -22.33093333 -68.01161667 0.20 seconds > 1 minute weak geyser

T33 -22.33003333 -68.00968333 0.20 seconds 30 seconds weak geyser

T33b -22.33033333 -68.00968333 - - fumarole

T32 -22.33093333 -68.01161667 0.10 seconds > 2 minutes weak geyser

T26 -22.33116667 -68.01133333 0.20 minutes seconds geyser

GROUP U-V

T35 -22.33123333 -68.01176667 1.50 1 minute 2 minutes geyser

T36 -22.33143333 -68.01180000 0.50 perpetual perpetual perpetual spouter

T37 -22.33106667 -68.01193333 0.10 seconds seconds geyser

T38 -22.33121667 -68.01221667 0.20 < 30 seconds 2 minutes geyser

T67 -22.33140000 -68.01255000 0.30 10 minutes + unknown geyser

T67b see map see map 0.40 4 minutes > 1 minute geyser

Appendix I

The Geysers and Springs of El Tatio

Observations of March 8–24, 2002

69The GOSA Transactions2003

T39 -22.33116667 -68.01223333 0.10 seconds <1 minute geyser

T40 -22.33130000 -68.01210000 0.10 perpetual perpetual perpetual spouter

T41 -22.33138333 -68.01210000 0.40 2 minutes > 5 minutes geyser

T42 -22.33140000 -68.01183333 30 seconds 3 minutes intermittent overflow

T43 -22.33156667 -68.01215000 1.00 minutes seconds geyser

T44 -22.33160000 -68.01216667 0.10 > 1 minute > 5 minutes geyser

T45 -22.33158333 -68.01225000 0.70 1 minute > 2 minutes geyser

GROUP U-VI

T46 -22.33173333 -68.01213333 1.00 >1 minute >15 minutes geyser

T47 -22.33176667 -68.01221667 0.10 seconds unknown geyser

T48 -22.33170000 -68.01238333 0.20 seconds minutes geyser

T49 -22.33175000 -68.01246667 0.05 seconds seconds geyser

T50 -22.33175000 -68.01243333 0.50 > 1 minute seconds geyser

T51 -22.33155000 -68.01276667 1.00 < 5 minutes <15 minutes geyser

T53 -22.33190000 -68.01256667 0.15 unknown 10 minutes geyser

T54 -22.33175000 -68.01248333 0.05 seconds seconds weak geyser

T55 -22.33168333 -68.01251667 0.10 < 10 seconds unknown geyser

T56 -22.33191667 -68.01231667 0.50 seconds > 1 minute geyser

T57 -22.33171667 -68.01251667 0.05 seconds 1 minute geyser

T58 -22.33171667 -68.01250000 - - hot spring

GROUP U-VII

T59 -22.33195000 -68.01276667 0.30 1 second < 30 seconds geyser

T60 -22.33185000 -68.01288333 - - warm spring

T61 -22.33203333 -68.01275000 0.60 5+ minutes seconds geyser

T62 -22.33208333 -68.01345000 0.10 perpetual perpetual perpetual spouter

T63 -22.33216667 -68.01303333 3.00 15 minutes 2.5 hours+ geyser

T64 -22.33215000 -68.01290000 - - dormant vent

T65 -22.33220000 -68.01293333 0.15 seconds seconds geyser

T66 -22.33320000 -68.01300000 3.00 seconds > 1 hour geyser

T67c see map see map 1.00 1 minute seconds geyser

GROUP U-VIII

T3 -22.32728333 -68.00568333 1.00 15 seconds 4 minutes geyser

T4 -22.32813333 -68.00623333 0.20 8 minutes 14 minutes+ geyser

GROUP L-I

T68 -22.34088333 -68.02275000 1.00 1 minute 3 minutes+ geyser

T68b -22.34145000 -68.02235000 0.20 perpetual perpetual perpetual spouter

T69 -22.34106667 -68.02396667 0.30 perpetual perpetual perpetual spouter

T70 -22.34116667 -68.02421667 1.00 < 1 minute ~2 minutes geyser

T71 -22.34108333 -68.02423333 1.00 ~ 1 minute ~ 5 minutes geyser

GROUP L-II

T72 -22.34038333 -68.02635000 5.00 >30 minutes minutes geyser

T73 -22.34043333 -68.02621667 2.50 >30 minutes seconds geyser

T74 -22.34068333 -68.02655000 0.40 perpetual perpetual perpetual spouter

T77 -22.34050000 -68.02708333 1.00 3 minutes 5 minutes geyser

T78 -22.34058333 -68.02710000 0.40 > 1 minute minutes geyser

T79 -22.34050000 -68.02705000 0.50 ~15 minutes 10 minutes geyser

T76 -22.34041667 -68.02705000 0.50 perpetual perpetual perpetual spouter

T80 -22.34075000 -68.02700000 2.00 25 minutes unknown geyser

70 The GOSA Transactions Volume VIII

T75 -22.34071667 -68.02700000 0.20 seconds seconds geyser

T81 -22.34081667 -68.02686667 0.50 perpetual perpetual perpetual spouter

T82 -22.34038333 -68.02673333 0.10 minutes 20+ minutes geyser

T83 -22.34050000 -68.02650000 0.15 perpetual perpetual perpetual spouter

T84 -22.34038333 -68.02686667 1.00 minutes seconds geyser

T84b see map see map 0.10 10 seconds minutes weak geyser

T85 see map see map 0.30 seconds seconds geyser

GROUP L-III

T86 -22.34028333 -68.02690000 1.00 erratic erratic mud volcano

T100 see map see map 0.50 1 minute erratic geyser

T101 see map see map 1.00 1 minute 3 minutes geyser

T102 see map see map 0.05 1 second 10-15 seconds weak geyser

T103 see map see map 0.60 minutes seconds geyser

T104 see map see map 0.60 minutes seconds geyser

T105 see map see map 0.20 seconds seconds geyser

T105a see map see map 0.10 seconds < 1 minute geyser

GROUP L-IV

T98 -22.33715000 -68.02640000 1.00 near perpetual seconds geyser

T99 -22.33898333 -68.02615000 - - hot spring pool

GROUP L-VI

T1 -22.33955000 -68.01898333 - - hot spring pool

T2 -22.33958333 -68.01855000 0.50 perpetual perpetual perpetual spouter

GROUP M-I

T87 -22.34241667 -68.01283333 1.00 near perpetual < 1 minute geyser

T88 -22.34240000 -68.01283333 0.30 seconds > 1 minute geyser

T89 -22.34255000 -68.01233333 0.20 2 minutes 1 minute geyser

T90 -22.34265000 -68.01216667 - - hot spring pool

T91 -22.34348333 -68.01175000 2.00 seconds ~ 1 minute geyser

T92 -22.34346667 -68.01203333 2.00 seconds seconds geyser

T93 -22.34408333 -68.01198333 2.00 near perpetual seconds geyser

T94 -22.34405000 -68.01198333 1.00 near perpetual seconds geyser

T95 -22.34410000 -68.01190000 1.00 near perpetual seconds geyser

T96 -22.34558333 -68.01221667 0.20 unknown >15 minutes geyser

T96b see map see map - - hot spring pool

GROUP M-II

T97 -22.34638333 -68.01326667 0.30 perpetual perpetual perpetual spouter

GROUP M-III

T106 see map see map 2.00 <1 minute >15 minutes geyser

Sol de Manana -22.42545000 -67.76178333 - - Bolivian field

71The GOSA Transactions2003

APPENDIX II: Expedition Log

Inception — Before the trip in March 2002, Alan

Glennon had been talking about making a South

American geyser trip for nearly a year. Along the

way, his rambling about geysers high in the Andes

Mountains piqued the interest of several friends.

Rhonda Pfaff, a graduate student, had gained an

interest in geysers while working at the Yellow-

stone Center for Resources at Yellowstone National

Park during the summer of 2001. On one trip to

visit her, Alan brought along geology student

Weldon Hawkins. To show Weldon something dif-

ferent, Alan took him to Geyser Creek. After sev-

eral hours in the backcountry thermal area, Weldon

was hooked. Shane Fryer, a geography student and

avid traveler, was our fourth participant.

Since, we were all associated with Western

Kentucky University (WKU), we had the same

spring break holiday. In addition, Shane’s father

works for an airline serving Santiago, Chile and

was able to obtain discount passes. We left from

Louisville, Kentucky, for Chile on March 13, 2002.

We wanted to see the geyser field at El Tatio, and

other thermal fields, too, if we could arrange the

travel.

Flying standby from Louisville, we scheduled a

“buffer day” in Santiago, Chile’s capital and home

of 5 million inhabitants, before our 2,000–kilome-

ter domestic flight to Calama. We spent the day in

Santiago walking around downtown, visiting the

University of Chile, and obtaining maps at the

Instituto Geográfico Militar (IGM). We purchased

1:50,000 scale topographic maps of the Chilean

geyser fields of El Tatio and Puchultisa. The IGM

employees spoke some English, although much of

the conversation of selecting the particular map

sheets occurred in Spanish. Rhonda and Weldon

both speak Spanish. Their Spanish was particularly

useful in obtaining food, lodging, and the rental car.

From Santiago to the Atacama Desert — From

Santiago, we flew LanChile—Línea Aérea

Nacional, the government airline of Chile—north

to Calama, with a stop in Antofagasta. The Calama

airport had roll–up steps for deplaning and a single

baggage claim carousel inside. As we stepped off

the airplane, we saw a vast, wide–open landscape

voided of all vegetation and dotted with chunks of

rock. At the Calama airport gift shop, we purchased

a Spanish guidebook with road maps of northern

Chile, published by the telecommunications

company CTC Chile [Zúñiga, 2001].

A line of rental car agents from primarily Ameri-

can companies greeted the flight. We obtained our

vehicle from the Chilean company Econorent with-

out having confirmed reservations. We rented a

Toyota Hilux (similar to a Tacoma), which was a

double–cab, 4x4 sport utility truck with a 5–speed

manual transmission, roll bar, and room for five

people. We were sure to rent a truck that was tuned

for driving off–road and at high altitudes. It came

equipped with a flag on a 3–meter pole and a flash-

ing blue light for driving in the large open pit cop-

per mines near Calama. With unlimited kilometers,

two drivers, and insurance, a week’s rental was

about US$500. An International Driver’s Permit is

required to drive in Chile.

Paved roads become dirt paths in San Pedro de

Atacama, an oasis town of about a thousand per-

manent residents located about 60 kilometers south-

east of Calama. San Pedro is a tourist town, with

small hotels, quaint cafes and restaurants. The town

has an outdoor market, archaeological museum,

charming adobe church with a cactus–wood ceil-

ing, and an interesting cemetery. There are also

many Internet cafes, with an hour of access for as

little as US$1.50. Most of the visitors we saw in

San Pedro were German or Australian eco–tour-

ists; Americans were scarce. The town has elec-

tricity from 8 or 9 a.m. to midnight and most hotels

we found throughout northern Chile only have hot

water when tourists request it.

We arrived in San Pedro after 10 p.m., which,

without reservations, made it difficult to find a ho-

tel. Since the first hotel we checked had a sign

warning, “Peligro! Cholera,” we took our search

elsewhere (the sign was leftover from an outbreak

several years ago). We ended up spending the week

at the Hostal Sumaj–Jallpa, a hotel just outside of

the “downtown.” The small hotel had an inner

courtyard and about five rooms. Our room cost

about US$30 per night for four people. Weather

during the day in San Pedro, at nearly half the el-

72 The GOSA Transactions Volume VIII

evation of El Tatio, was typically hot at around

27oC. However, temperatures decreased enough

each night to make sleeping comfortable.

The majority of our meals in San Pedro were at

Petro Pizza, a small restaurant run by a German–

turned–Chilean hippy that, of course, served pizza.

He also served empanadas and other traditional

Chilean dishes. A pizza marguerita (cheese pizza)

was about US$1.50 there. We found that only chain

restaurants (like the Calama Domino’s Pizza) served

the typical American–style pizza. The local restau-

rants skipped the sauce and placed the cheese (of-

ten Roquefort) on wafer–like crusts. San Pedro

grocery stores have water jugs, snacks, and bever-

ages. Supplies had to be purchased in either San

Pedro or Calama, since the area between San Pedro

and the geysers is effectively wilderness.

As a general note, a Hepatitis A (and Hepatitis

B) immunization is recommended for the trip. We

visited travel doctors before the trip and received

prescription medication for diarrhea, nausea, eleva-

tion sickness, and other travel–related unpleasant-

ness. While some travelers said that much of Chile’s

water is potable, we drank only bottled water. Some

villages near Calama have water supplies that have

been contaminated by copper mine drainage. Alan

became very sick on the trip (he left the United

States with a terrible cold, which did not mix well

with elevation), and almost had to cut his trip short.

Because of lost time from his sickness, we were

unable travel to Puchultisa, although we spent three

days at El Tatio and one day in Bolivia.

San Pedro was our base for our El Tatio and

Bolivia excursions. We spent two nights in San

Pedro in order to acclimate to the high elevation

(2,440 meters at San Pedro). Just a few kilometers

outside of San Pedro is Valle de la Luna (Valley of

the Moon) within the Reserva Nacional Los Fla-

mencos (National Flamingo Reserve). Valle de la

Luna has widespread salt deposits, caves, pits,

heavily folded rocks, and sand dunes over 100

meters tall. However, in the area, we also passed

several former land mine fields with signs warning

visitors to remain on the road. Mines are a real

danger in Chile; in 2001, a group visiting El Tatio

found a mine along the main road [La Estrella de

Loa, 2001].

To Bolivia — After a few days in San Pedro,

everyone but Alan took a day–trip to Bolivia. The

stops along the tour were Laguna Blanca, Salvador

Dalí’s Rocks, Aguas Termales (warm springs), Sol

De Mañana thermal field, Laguna Colorada, and

Laguna Verde. Tour companies in San Pedro

primarily offered trips to Bolivia that lasted three

days and concluded at Uyuni, Bolivia; Pamela Tours

was the only company that we found that offered a

single–day–long trip to Bolivia. Since a three–day

trip to Uyuni is US$70 (plus an extra US$50 to

return to San Pedro), our single–day excursion, with

a minimum four people and a maximum of six

people, was considered very expensive at US$50

per person. The tour left at 8:30 a.m. and dropped

us off at our hotel at 8 p.m.

The trip began at the tour company’s office,

with the first stop at Chilean customs and immi-

gration just a few kilometers outside San Pedro.

An officer stamped us out of the country and col-

lected our yellow landing slips from our arrival at

the Santiago airport. The true border with Bolivia

was approximately another hour away on a road

that was paved for much of the way. At Bolivia,

the van driver dropped us off as a new driver in a

beaten–up Toyota Land Cruiser Sport Utility Ve-

hicle (SUV) met us. At Bolivian customs and im-

migration, a shack with abandoned vehicles strewn

about around the property, we each paid a US$5

entrance fee for the Reserva Nacional de Fauna

Andina Eduardo Avaroa (a national wildlife refuge)

and received a passport stamp valid for up to a 30–

day stay.

The Bolivian dirt roads were very bumpy and

heavily “wash–boarded.” The first stop along the

tour was a few kilometers from the border, at La-

guna Blanca (White Lake). It is a clear, shallow,

reflective lake surrounded by mountains. There

were a few flamingos wading in the water. Laguna

Blanca appeared to be a meeting point for several

tours, since there were many backpackers sitting

on the steps of a series of hostel rooms that faced

the lake. There, our driver checked over the SUV;

at one point, he was using a welder to repair some-

thing under the hood. This was also the last oppor-

tunity to use a flushing toilet, which cost 100 Chil-

ean pesos (about US$0.15).

73The GOSA Transactions2003

From Laguna Blanca, the next stop was Salva-

dor Dalí’s Rocks, a series of jagged outcrops that

are reminiscent of a Dalí painting. Some tours drive

up to the rocks, although ours remained a kilome-

ter or so away. The 20 minutes of hiking out to the

rocks spent time that could have instead been ap-

plied to the geysers.

About 20 minutes later, we reached Aguas

Termales, a lake with a series of hot springs around

the shore. At least five other tour groups were al-

ready at Aguas Termales. We measured the primary

spring at 37oC. One of the other tour SUVs had a

stereo and was blaring 1980s American dance mu-

sic, as many of the youthful, European tourists

bathed in the shallow waters or kicked a soccer

ball amongst each other. We saw some tourists sub-

merging themselves in the spring water, which we,

as students of water quality, deemed an unhealthy

decision.

At Aguas Termales, the tour company provided

“lunch,” which consisted of fresh cucumbers and

tomatoes, and Bolivian bologna (we think) with

pink and white fatty speckles. The “mystery meat”

had been in a basket—not a cooler—in the back of

the truck, in the sun, for several hours. Shane and

Weldon ate the meat and became ill that day, while

Rhonda, who brought a jar of peanut butter and

made her own sandwich, remained healthy. There-

fore, we suggest bringing your own lunch and

gracefully declining the tour company meal. The

tour operator also rinsed the dishes and knives from

lunch in one of the thermal springs. During the

dishwashing, we discovered that our vehicle had a

flat tire, which the driver changed in about ten min-

utes. In all, about two hours was spent at Aguas

Termales; a ten–minute stop is about all that is

needed.

After another 45 minutes of driving, we reached

Sol de Mañana thermal field (at elevations around

4,800–5,000 meters). At the field, there were al-

ready four tour SUVs. The air temperature was

warm and the sun was bright, although a chilly wind

blew across the altiplano. We drove across the hy-

drothermally altered ground and parked at an area

of intense activity. As the driver stopped the truck,

he turned around and said, “Diez minutos,” which

meant that we were leaving Sol de Mañana in ten

minutes. Frustrated, we offered to pay him extra to

skip the rest of the tour and remain longer at the

thermal area. He repeated, “Diez minutos.” Shane

ran as far as he could from the truck to provide us

with more time. In total, we spent about 25 min-

utes at the field; in the allotted time, we believe we

saw only a quarter of the area.

The hydrothermally altered, barren soils ranged

from reds and oranges to grays and whites. As we

stepped out of the truck, the ground was whistling

with steam and we felt thumps underfoot from in-

tense subterranean activity. Faded, wooden, red

signs warned us, “Peligro de muerte”: danger of

death. We saw tourists walking haphazardly through

many risky areas. None of the tourists appeared to

be in the field with their guides; indeed, our driver

(as he did at all the stops), leaned his seat back,

covered his eyes with his hat brim, and took a short

nap.

Trying to see as much hydrothermal activity at

Sol de Mañana as possible, we ran around the field

(as quickly as we could at high elevations and in

unstable terrain). The main area is about 10 km2,

although hydrothermal manifestations occur

throughout a much larger region. In the short time

that we were there, we saw one perpetual spouter

sputtering a fine spray a meter high within its cra-

ter. Because other features in the area appeared to

be watery, it is likely that there are other perpetual

spouters and possibly geysers. The area we visited

seemed to be part of the field’s higher elevations;

there is also a potential for eruptive features in the

lower elevations of the basin. Nonetheless, Sol de

Mañana has incredible mudpots that splash gray to

deep–brown mud up to 2 meters. Many of the wa-

terlogged pots splashed more than “plopped.”

Closely spaced depressions 3 meters deep and some

nearly 7 meters wide dominated the field, with each

splattering mud. Plumes of steam could be seen in

the distance and on hills lining one side of the field.

A strong fumarole vented steam 10 meters and

higher. Angular, volcanic rocks, many larger than

our truck, dotted the hillside and altiplano. Within

2 kilometers of the field, we noticed at least two

geothermal wells.

The final two stops along the tour were La-

guna Colorada and Laguna Verde. Laguna Colorada

74 The GOSA Transactions Volume VIII

is a pink–colored lake that had flamingos wading

in it. Mountains and volcanoes surround the ther-

mally fed lake. As we neared Laguna Verde, a bril-

liant, emerald green lake, the weather turned windy,

cold, and rainy. At Laguna Verde, we stopped only

long enough to snap a few photographs of the lake

and a rainbow behind us. We soon arrived again at

the Bolivian border, where we paid a “departure

tax” of 1,500 Chilean pesos each (about US$2) and

received exit stamps in our passports.

On the return trip to San Pedro, we passed

through a storm that dropped more than a centi-

meter of snow. Every few minutes, the front seat

passenger had to wipe the driver’s continuously

fogging windshield. As we descended to San Pedro,

the storm passed. At Chilean customs and immi-

gration on the outskirts of town, a narcotics dog

sniffed the van and our personal items. Inside cus-

toms, we had to empty our bags and were hand–

searched for drugs, fruits, and vegetables. Before

long, we were back at our hotel and regaling Alan

with stories about the tour. For the lakes, Andean

views, and miscellaneous hot springs, seeing south-

ern Bolivia is worthwhile, even with only 25 min-

utes at Sol de Mañana.

To El Tatio — After the day trip to Bolivia, we

spent our next three days at El Tatio. We drove

ourselves to and from El Tatio daily, again using

San Pedro as our base. The 86–kilometer drive from

San Pedro to El Tatio took between two and two–

and–a–half hours. The route was along a rocky and

heavily wash–boarded dirt road with occasional

stream crossings and detours at washed–out

bridges. The road to El Tatio is well–marked and

easy to follow. Traversing unimproved roads,

volcanic rocks, sand, and gravel proves hard on

car tires. We were sure to bring the tools necessary

to change a tire — including a good spare. In fact,

the locals recommend having two spares. We also

filled our gas tank daily, just in case weather or

unexpected washouts forced us to return via the

alternate route. The alternate road to El Tatio via

Calama is about 130 kilometers long. Gas in Calama

was reasonably priced, but was expensive in San

Pedro. The single gas station in San Pedro is at

Hostería San Pedro, where it cost as much as

US$80 for a fill–up. We also took camping gear

with us, in case we had major car troubles. It was

reassuring that a load of tourist buses would be

driving the road each morning.

Although the owner of our hotel in San Pedro

questioned us for heading to El Tatio when there

was supposedly no activity, we set out for El Tatio

each day in the mid–morning. We passed tour vans

returning to San Pedro, but we arrived at El Tatio

after all the tourist buses had left. For the three

days of our visit, we were alone in the basin.

At elevations close to 4,500 meters at the gey-

sers, the decreased oxygen level slowed our physi-

cal activities. We spent the days recording the ac-

tivity in a field notebook and collecting map coor-

dinates using a handheld Global Positioning Sys-

tem unit. We took still photographs and used a video

camera to document the activity. However, after

two days, the camcorder malfunctioned. The com-

bination of rough roads, dust, and steam proved

too much for the camera.

The afternoon temperatures at El Tatio in March

were chilly, primarily from mountain winds. As if

preparing for a cool day in Yellowstone and at high

elevations, we wore sunblock, sunglasses, blue

jeans, floppy hats, jackets and fleece liners, and

gloves. We also experienced a thunderstorm one

day at the basin. Though the clouds made the sky

dark, only a trace of rain fell.

We generally left El Tatio just before dark (at

around 6 or 7 p.m.), so we would at least be on the

road before night fell. We saw many chinchillas and

other small nocturnal animals bounding across the

road. By the time we arrived in San Pedro each

night and took a quick shower, the town had al-

ready slowed down. By 10 p.m., most of the tour-

ists had eaten and were wandering the streets re-

turning to their hotels. We usually hit a restaurant

as they closed and made a last supply run to one of

the small general stores.

APPENDIX III: HAZARDS

Numerous hazards exist while traveling abroad

in general. However, the following are some of the

hazards and cautions specifically relating to travel

to El Tatio Geyser Field.

75The GOSA Transactions2003

The Thermal Area

Although the El Tatio Geysers have become

increasingly accessible by tour and rented vehicle,

visitors should be aware of numerous hazards in-

volved in traveling to and within this thermal area.

Guides in San Pedro told us that burn accidents are

routine and several people have died by falling into

boiling pools. Unconfirmed accounts have reported

that a body was not recovered at El Tatio and that

several bodies may remain in the mudpots of Sol

de Mañana. In October 2002, a Spanish tourist to

El Tatio stepped backward into a hot spring—with

a temperature estimated at 90oC—and received

burns to 80 percent of his body [La Estrella de

Loa, 2002]. As a result, a $35,000 trail and park-

ing project are underway to enhance visitor safety

[La Estrella de Loa, 2003]. Regardless, as with all

geyser areas, extreme care must be taken while

walking throughout the basin. Thin crusts may con-

ceal underlying pools of boiling water and mud.

Unseen fragile rims may overhang deep boiling

pools, while seemingly innocuous dry cones and

rifts areas can violently eject boiling water with little

or no notice. One remarkable characteristic of the

El Tatio basin is that a number of thermal features

are submerged in the Río Salado. These features

look like deep spots in the otherwise shallow river,

although these locations actually discharge boiling

water. Visitors unaccustomed to the perils of

backcountry geyser travel should be careful to stay

with competent guides. Considerate travel through

the basin not only is safer, but also helps protect

the thermal features themselves.

Volcanoes

The geyser field is ringed by active volcanoes.

On the drive to El Tatio, we noticed two volcanic

vents. From San Pedro de Atacama we saw that

Volcán Lascar, about 100 kilometers to the south,

was having constant hydrothermal eruptions. These

occurred throughout our seven–day visit. Volcán

Lascar is one of the most active volcanoes in the

central Andes. Violent eruptions in July 2000 sent

ash streaming 4,000 to 5,000 meters above its sum-

mit. In addition, near Volcán Lascar, renewed ac-

tivity has appeared at Volcán Chilique. The activity

was first noted on NASA Aster satellite imagery in

January 2002. During our last day at El Tatio,

Volcán Putana, which is 25 kilometers southeast of

the basin, began spewing 200–meter–high columns

of steam from its crater. Visitors should be con-

stantly aware of their surroundings and ask locals

about ongoing volcanic activity.

Roads

The dirt roads to El Tatio from San Pedro and

Calama are well marked, but there are several points

to consider before traveling. First, make sure to

have a vehicle tuned to high elevation travel. While

El Tatio itself is at 4,200 meters, the road steadily

climbs from these cities and traverses altitudes of

greater than 4,700 meters. Elevation gain is accom-

plished through a series of occasionally sharp

switchbacks. Numerous memorial crosses have

been placed along the side of the road marking lo-

cations where vehicles have driven off the road and

down the steep hillsides. On a return trip from the

basin one evening, we encountered a truck that had

taken a turn too fast and was now resting upside

down with its windows shattered. We stopped to

investigate since the overhead light in the truck was

on, although there were no passengers inside when

we found the vehicle. The wreck had occurred

sometime while we were at El Tatio, since it was

not there on our way to the basin. By our trip to

the basin the next day, the vehicle had been towed

to San Pedro.

Several large road washouts exist along the

main route, too, but are not problematic with slow,

attentive driving. The locals, possibly the tour com-

panies, have created alternate winding routes

around each washout. The road from San Pedro to

the geysers also crosses a number of creeks that

were up to sixty centimeters deep. The creeks could

be dangerous if approached too quickly or if a re-

cent rain had raised the water levels. Flash floods

can create impassable muddy deluges during thun-

derstorms and sudden snow melts. During normal

conditions, other than occasional streams and mud

puddles, the route is dry. With a four–wheel drive

vehicle, having a flat tire (since the dirt roads tend

to be made of gravels and sharp volcanic basalts) is

the most likely problem to occur along the road.

Getting stuck at the geyser basin itself is possible,

76 The GOSA Transactions Volume VIII

though. Besides crossing the Río Salado, the road

through the basin travels around and literally over

numerous thermal features. Drivers should be ex-

tremely cautious. We originally planned to park at

the edge of the basin and walk to the features.

However, we found ourselves using our truck as a

ferry to keep ourselves dry, since the Río Salado

flows throughout much of the basin as a wide,

braided stream requiring frequent fording.

Plans appear to be underway to create a paved

road from San Pedro to the basin. Numerous gov-

ernment signs near San Pedro provide information

about the road project, but probably also portend

the beginning of geothermal electricity develop-

ment. We noticed flagged survey stakes along the

side of the road for a majority of the route.

Elevation Sickness

At elevations of 4,200 meters and greater, El

Tatio Geyser Field is one of the highest geyser fields

on earth. The road from San Pedro to the geyser

basin often exceeds 4,700 meters. At the basin’s

altitude, elevation sickness is common. Allow time

to acclimate slowly to the high elevations. Our team

stayed in San Pedro de Atacama (2,440 meters)

two nights before traveling to the higher elevations.

When we arrived at the basin, we each felt at least

some effect of the altitude. We found that the best

way to cope with the high altitude was to walk

slowly and minimize exertion (hiking and climbing

was very slow as well). Fortunately, most of the

geysers lie on gentle slopes or level ground. The

kilometer or two walk to the Lower Basin (River

Group) put everyone in our group out of breath;

Alan and Rhonda both got headaches, but an

ibuprofen solved the problem within an hour. Of

course, being well–hydrated and getting plenty of

sleep the night before lowers the risk of altitude

problems. Tourist accounts of the basin seemed to

come in two varieties: either the people loved the

tour or they became sick. Since it is a good idea to

consult a doctor about various immunizations be-

fore international travel anyway, ask about coping

with high altitudes.

Landmines

Politically, Chile is a civilized, modern destina-

tion for travelers and scientists. Social and legal

order are similar to Europe, Australia, and North

America. Nevertheless, from 1974 to 1978, ten-

sions between Chile and its neighbors Bolivia, Peru,

and Argentina were the basis for a program of

minefield creation. At least 293 separate minefields,

between 250,000 and 1,000,000 landmines were

laid in northern Chile. Although Chile now opposes

the use of landmines and, in 2001, ratified an inter-

national treaty banning their use, minefields still

exist in northern Chile. Particularly at Valle de Luna

and along the road between Calama and San Pedro

de Atacama, signs denote areas where minefields

still pose a danger. Although there is no indication

that mines were laid at the geysers themselves, tour-

ists in January 2001 reported an antipersonnel mine

on the way to El Tatio and notified local authori-

ties. Mine clearance personnel from Calama were

mobilized, but were unable to find any mines [La

Estrella de Loa, 2001]. In 1999, the Chilean Gov-

ernment began an 11–year mine clearing program

that will reduce the landmine threat.

Weather–related Hazards

With its location that spans the Andes Moun-

tains and the Atacama Desert, the weather at the

basin could be life–threatening for unprepared visi-

tors. Be sure to carry plenty of water; the Atacama

is known for being one of the driest places on earth.

Water quality varies widely in the thermal basin;

drinking the water is not recommended. Through-

out the year, weather typically gets near or below

freezing at night. Many tourist photos, which are

generally taken at sunrise, show ice patches around

the geyser cones. During the day, temperatures can

be warm. However, snow above 4,000 meters is

common. Although we did not encounter any dust

storms, they are apparently quite dangerous in the

area, particularly in the lower elevations at San

Pedro and Calama. We were told that when dust

storms occur, all travel, including tour operations,

halts.

77The GOSA Transactions2003

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Alan Glennon has visited several of the world’s geyser areas. This photo, taken in

2003, shows a small geyser at HvHv

HvHv

Hveraera

eraera

eravv

vellirellir

ellirellir

ellir, Iceland, Iceland

, Iceland, Iceland

, Iceland.

Characterization of the shallow structure of El Tatio geothermal field in the Central Andes, Chile using transient electromagnetics

Article

Feb 2021
J VOLCANOL GEOTH RES

This study presents the first high resolution geophysical survey conducted in The El Tatio geothermal field, northern of Chile, focused on the detection of shallow subsurface structures and identification of ascending fluid pathways. TEM data was collected along 5 profiles crossing the two main geothermal basins (Upper and Middle Basin) to obtain an electrical resistivity model up to 200 m depth. The models show important structures that allowed us to improve the conceptual model of the field connecting these geophysical observations with the geology and the geochemistry of the area. We found a shallow (<60 m) high conductivity layer in all profiles. This layer was interpreted as a shallow aquifer of thermal water, which is probably the water supplier of surface manifestations. In the Upper Basin a main permeable zone allows the ascent of fluids from deep aquifers to the shallower one, and a structure that probably act as impermeable geological barrier that forces the fluids to ascend has been detected. In the Middle Basin fluid ascent zones are less clear than in the Upper Basin but it is possible to observe areas of lower resistivity that could be associated with higher permeability.

Reservoir architecture model and heat transfer modes in the El Tatio-La Torta geothermal system, Central Andes of northern Chile

Article

Sep 2020
GEOTHERMICS

In this work, we present an update for the conceptual model of the El Tatio-La Torta geothermal system, one of the most studied geothermal fields in the Central Andes of South America. Using the structural model reported by Veloso et al. (2019) for northern Chile, the conceptual model proposes a reservoir architecture and heat transfer modes at different scales, connecting the distal catchment area located 15 km east of El Tatio with the outflow of the system: El Tatio geothermal field. The main results of this work are (a) the location of a complex and large reservoir system below El Tatio and La Torta, composed by three main levels named A, B and C, which are connected by the intersection of NW-striking left-lateral and N-striking thrust faults, (b) an explanation for the upflow below La Torta, which is given by the tectono-geothermal environment of the geothermal system, (c) the possible location of the main catchment area at the Tocorpuri basin/caldera, located 15-20 km to the east from the El Tatio geysers, and (d) an explanation for the apparent hydraulic disconnection at El Tatio observed by pressure interference tests, which is coherent with the proposed structural setting for the geothermal field. These results give a physical representation about the fluid circulation and heat transfer modes, connecting La Torta and El Tatio as a unique large-scale geothermal system in the Central Andes.

Isolation and Characterization of Thermus thermophilus Strain ET-1: An Extremely Thermophilic Bacterium with Extracellular Thermostable Proteolytic Activity Isolated from El Tatio Geothermal Field, Antofagasta, Chile

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Sep 2023
INT J MOL SCI

The present study describes the isolation of an extremely thermophilic bacterium from El Tatio, a geyser field in the high planes of Northern Chile. The thermophile bacterium named Thermus thermophilus strain ET-1 showed 99% identity with T. thermophilus SGO.5JP 17-16 (GenBank accession No. CP002777) by 16S rDNA gene analysis. Morphologically, the cells were non-sporeforming Gram-negative rods that formed colonies with yellow pigmentation. This strain is able to proliferate between 55 and 80 °C with a pH range of 6–10, presenting an optimum growth rate at 80 °C and pH 8. The bacterium produces an extracellular protease activity. Characterization of this activity in a concentrated enzyme preparation revealed that extracellular protease had an optimal enzymatic activity at 80 °C at pH 10, a high thermostability with a half-life at 80 °C of 10 h, indicating that this enzyme can be classified as an alkaline protease. The proteolytic enzyme exhibits great stability towards chelators, divalent ions, organic solvents, and detergents. The enzyme was inhibited by phenylmethylsulfonyl fluoride (PMSF), implying that it was a serine protease. The high thermal and pH stability and the resistance to chelators/detergents suggest that the protease activity from this T. thermophilus. strain could be of interest in biotechnological applications.

Global phylogenomic novelty of the Cas1 gene from hot spring microbial communities

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Dec 2022

The Cas1 protein is essential for the functioning of CRISPR-Cas adaptive systems. However, despite the high prevalence of CRISPR-Cas systems in thermophilic microorganisms, few studies have investigated the occurrence and diversity of Cas1 across hot spring microbial communities. Phylogenomic analysis of 2,150 Cas1 sequences recovered from 48 metagenomes representing hot springs (42–80°C, pH 6–9) from three continents, revealed similar ecological diversity of Cas1 and 16S rRNA associated with geographic location. Furthermore, phylogenetic analysis of the Cas1 sequences exposed a broad taxonomic distribution in thermophilic bacteria, with new clades of Cas1 homologs branching at the root of the tree or at the root of known clades harboring reference Cas1 types. Additionally, a new family of casposases was identified from hot springs, which further completes the evolutionary landscape of the Cas1 superfamily. This ecological study contributes new Cas1 sequences from known and novel locations worldwide, mainly focusing on under-sampled hot spring microbial mat taxa. Results herein show that circumneutral hot springs are environments harboring high diversity and novelty related to adaptive immunity systems.

Lipid Profiles From Fresh Biofilms Along a Temperature Gradient on a Hydrothermal Stream at El Tatio (Chilean Andes), as a Proxy for the Interpretation of Past and Present Biomarkers Beyond Earth

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Full-text available

Jun 2022

Hydrothermal systems and their deposits are primary targets in the search for fossil evidence of life beyond Earth. However, to learn how to decode fossil biomarker records in ancient hydrothermal deposits, we must first be able to interpret unambiguously modern biosignatures, their distribution patterns, and their association with physicochemical factors. Here, we investigated the molecular and isotopic profile of microbial biomarkers along a thermal gradient (from 29 to 72°C) in a hot spring (labeled Cacao) from El Tatio, a geyser field in the Chilean Andes with abundant opaline silica deposits resembling the nodular and digitate structures discovered on Mars. As a molecular forensic approach, we focused on the analysis of lipid compounds bearing recognized resistance to degradation and the potential to reconstruct the paleobiology of an environment on a broader temporal scale than other, more labile, biomolecules. By exploiting the lipid biomarkers' potential to diagnose biological sources and carbon fixation pathways, we reconstructed the microbial community structure and its ecology along the Cacao hydrothermal transect. The taxonomic adscription of the lipid biomarkers was qualitatively corroborated with DNA sequencing analysis. The forensic capacity of the lipid biomarkers to identify biosources in fresh biofilms was validated down to the genus level for Roseiflexus, Chloroflexus, and Fischerella. We identified lipid biomarkers and DNA of several new cyanobacterial species in El Tatio and reported the first detection of Fischerella biomarkers at a temperature as high as 72 • C. This, together with ecological peculiarities and the proportion of clades being characterized as unclassified, illustrates the ecological singularity of El Tatio and strengthens its astrobiological relevance. The Cacao hydrothermal ecosystem was defined by a succession of microbial communities and metabolic traits associated with a high-(72°C) to low-(29°C) temperature gradient that resembled the inferred metabolic sequence events from the 16S rRNA gene universal phylogenetic tree from thermophilic to anoxygenic photosynthetic species and oxygenic phototrophs. The locally calibrated DNA-validated lipidic profile in the Cacao biofilms provided a modern (molecular and isotopic) end member to facilitate the recognition of past biosources and metabolisms from altered biomarkers records in ancient silica deposits at El Tatio analogous to Martian opaline silica structures.

Evaporative silicification in floating microbial mats: patterns of oxygen production and preservation potential in silica‐undersaturated streams, El Tatio, Chile

Article

Full-text available

Oct 2021

Microbial mats floating within multiple hydrothermally sourced streams in El Tatio, Chile, frequently exhibit brittle siliceous crusts (~1 mm thick) above the air–water interface. The partially silicified mats contain a diverse assemblage of microbial clades and metabolisms, including cyanobacteria performing oxygenic photosynthesis. Surficial crusts are composed of several amorphous silica layers containing well‐preserved filaments (most likely cyanobacteria) and other cellular textures overlying EPS‐rich unsilicified mats. Environmental logs, silica crust distribution, and microbial preservation patterns provide evidence for crust formation via repeated cycles of evaporation and silica precipitation. Within the mats, in situ microelectrode profiling reveals that daytime oxygen concentrations and pH values are diminished beneath silica crusts compared with adjacent unencrusted communities, indicating localized inhibition of oxygenic photosynthesis due to light attenuation. As a result, aqueous conditions under encrusted mats have a higher saturation state with regard to amorphous silica compared with adjacent, more active mats where high pH increases silica solubility, likely forming a modest feedback loop between diminished photosynthesis and crust precipitation. However, no fully lithified sinters are associated with floating encrusted mats in El Tatio streams, as both subaqueous and subaerial silica precipitation are limited by undersaturated, low‐SiO2 (<150 ppm) stream waters. By contrast, well‐cemented sinters can form by evaporation in silica‐undersaturated solutions above 200 ppm SiO2. Floating mats in El Tatio therefore represent a specific sinter preservation window, where evaporation in silica‐undersaturated microbial mats produces crusts, which preserve cells and affect mat chemistry, but low‐silica concentrations prevent the formation of lasting sinter deposits. Patterns of silica precipitation in El Tatio microbial communities show that the preservation potential of silicifying mats in the rock record is strongly dependent on aqueous silica concentrations.

Trace Elemental Partitioning on Clays Derived From Hydrothermal Muds of the El Tatio Geyser Field, Chile

Article

Full-text available

May 2021

Recent experimental studies have demonstrated that clay minerals (e.g., kaolinite, illite, and montmorillonite) have higher affinities for some trace elements under acidic versus alkaline conditions. This suggests that clays might be important vectors in the transport of trace elements from sites of acidic chemical weathering on land to marine depositional environments. To determine if clays behave similarly in nature, we collected water and mud (consisting of 38.5%–61.1% of kaolinite and montmorillonite) samples from boiling, low‐pH, mud pools venting at the El Tatio Geyser Field (ETGF) in Chile. Based on elemental abundances in the aqueous/solid phases, we observed that mud samples collected from lower pH pools (e.g., pH = 2.42 and 3.55) have high concentration factors for anionic elements (e.g., P and As) but low concentration factors for cationic elements (e.g., Ca, Mn, and Sr), while mud samples from higher pH pools (e.g., pH = 4.87 and 5.84) display the opposite trend. Acid‐base leaching experiments further reveal that increasing solution pH (to reflect downstream transport) led to the release of As and P from the mud surfaces due to increasingly negative surface charge, while decreasing pH (to determine the effects of re‐acidification) released Li, Ca, Co, Sr, Mo, and Cd. Our study confirms previous experimental findings that demonstrate clay minerals can assemble a diverse inventory of trace elements during acid weathering (e.g., As) but then liberate them back into the aqueous phase as aqueous pH increases. Importantly, these observations provide a mechanism to account for the previous observations of regional As contamination in rivers downstream of the ETGF.

Composition and predicted functions of the bacterial community in spouting pool sediments from the El Tatio Geyser field in Chile

Article

Aug 2020

The El Tatio Geyser Field (ETGF), located in Northern Chile, is the main geyser field in the southern hemisphere. Despite this, details of its microbial ecology are still unknown. Here, we briefly report on the composition and predicted functions of the bacterial community in spouting pool sediments from the ETGF as revealed by high-throughput sequencing of 16S rRNA genes. Results of this analysis showed that while there were differences in richness and diversity between samples, bacterial communities were primarily dominated by the phyla Proteobacteria, followed Firmicutes, Bacteroidetes, Acidobacteria, and Chloroflexi. Analyses of predicted functional activity indicated that the functions were mostly attributed to chemoheterotrophy and aerobic chemoheterotrophy, followed by sulfur (respiration of sulfur compounds and sulfate) and nitrogen (nitrate reduction, respiration of nitrogen and nitrate) cycling. Taken together, our results suggest a high diversity in taxonomy and predictive functions of bacterial communities in sediments from spouting pools. This study provides fundamentally important information on the structure and function predictive functions of microbiota communities in spouting pools. Moreover, since the ETGF is intensively visited and impacted by tens of thousands of tourists every year, our resultscan be used to help guide the design of sustainable conservation strategies.

Effects of hydrogeochemistry on the microbial ecology of terrestrial hot springs

Article

Full-text available

Sep 2023

Temperature, pH, and hydrochemistry of terrestrial hot springs play a critical role in shaping thermal microbial communities. However, the interactions of biotic and abiotic factors at this terrestrial-aquatic interface are still not well understood on a global scale, and the question of how underground events influence microbial communities remains open. To answer this, 11 new samples obtained from the El Tatio geothermal field were analyzed by 16S rRNA amplicon sequencing (V4 region), along with 191 samples from previous publications obtained from the Taupo Volcanic Zone, the Yellowstone Plateau Volcanic Field, and the Eastern Tibetan Plateau, with their temperature, pH, and major ion concentration. Microbial alpha diversity was lower in acid-sulfate waters, and no significant correlations were found with temperature. However, moderate correlations were observed between chemical parameters such as pH (mostly constrained to temperatures below 70°C), SO 4 ²⁻ and abundances of members of the phyla Armatimonadota, Deinococcota, Chloroflexota, Campilobacterota, and Thermoplasmatota. pH and SO 4 ²⁻ gradients were explained by phase separation of sulfur-rich hydrothermal fluids and oxidation of reduced sulfur in the steam phase, which were identified as key processes shaping these communities. Ordination and permutational analysis of variance showed that temperature, pH, and major element hydrochemistry explain only 24% of the microbial community structure. Therefore, most of the variance remained unexplained, suggesting that other environmental or biotic factors are also involved and highlighting the environmental complexity of the ecosystem and its great potential to test niche theory ecological associated questions. IMPORTANCE This is the first approach to investigate whether geothermal processes could have an influence on the ecology of thermal microbial communities on a global scale. In addition to temperature and pH, microbial communities are structured by sulfate concentrations, which depends on the tectono-magmatic settings (such as the depth of magmatic chambers) and the local settings (such as the availability of a confining layer separating NaCl waters from steam after phase separation) and the possibility of mixing with more diluted fluids. Comparison of microbial communities from different geothermal areas by homogeneous sequence processing showed that no significant geographic distance decay was detected on the microbial communities according to Bray-Curtis, Jaccard, unweighted, and weighted Unifrac similarity/dissimilarity indices. Instead, an ancient potential divergence in the same taxonomic groups is suggested between globally distant thermal zones.

Distribution, structural and hydrological control of the hot springs and geysers of El Tatio, Chile, revealed by optical and thermal infrared drone surveying

Article

Oct 2022
J VOLCANOL GEOTH RES

Boiling mud ponds, hot springs, and geysers are the scenic surface expression of rising thermal fluids, often emerging in clusters. The details on the spatial appearance and structural control of such geothermal objects as well as on the variability of their locations are rarely investigated, however. Here we use Unmanned Aerial Systems (UAS) to acquire close-range optical and thermal infrared data over the El Tatio geothermal field (Chile), one of the largest geyser fields in the world. From high-resolution aerial images, processed using the Structure from Motion (SfM) method, we compute spatial image data at 1.5 to 14.5 cm resolution for a ~ 2 km² area. We identify 1863 objects related to geothermal activity, providing an unprecedented catalog of the geothermal area. Out of these, 148 were classified as topography objects (e.g. cone geysers), 415 showed signs of fluid discharge, and 1091 were characterized by a thermal signature exceeding background temperatures. The geothermal objects were further analyzed regarding their spatial distribution and clustering, suggesting a high degree of organization in 5 main groups on a broader scale, and clustering in specific vent arrangements resembling two main orientations on a smaller scale. The 5 zones show significant differences considering their orientation, types of geothermal objects located within, but also their eruptive characteristics, and thermal energy release. We discuss these, considering the structural setup and hydrological setting of the El Tatio geothermal field. Over 90% of the mapped geothermal objects are located within a 100 m distance to an estimated trend line oriented NE-SW. We thus hypothesize a possible structural arrangement controlling the location and activity of geothermal objects at El Tatio with important implications for other geothermal areas worldwide.

The Question of Recharge to the Deep Thermal Reservoir Underlying the Geysers and Hot Springs of Yellowstone National Park

Article

Full-text available

Jan 2007

The extraordinary number, size, and unspoiled beauty of the geysers and hot springs of Yellowstone National Park (the Park) make them a national treasure. The hydrology of these special features and their relation to cold waters of the Yellowstone area are poorly known. In the absence of deep drill holes, such information is available only indirectly from isotope studies. The δD-δ18O values of precipitation and cold surface-water and ground-water samples are close to the global meteoric water line (Craig, 1961). δD values of monthly samples of rain and snow collected from 1978 to 1981 at two stations in the Park show strong seasonal variations, with average values for winter months close to those for cold waters near the collection sites. δD values of more than 300 samples from cold springs, cold streams, and rivers collected during the fall from 1967 to 1992 show consistent north-south and east-west patterns throughout and outside of the Park, although values at a given site vary by as much as 8 ‰ from year to year. These data, along with hot-spring data (Truesdell and others, 1977; Pearson and Truesdell, 1978), show that ascending Yellowstone thermal waters are modified isotopically and chemically by a variety of boiling and mixing processes in shallow reservoirs. Near geyser basins, shallow recharge waters from nearby rhyolite plateaus dilute the ascending deep thermal waters, particularly at basin margins, and mix and boil in reservoirs that commonly are interconnected. Deep recharge appears to derive from a major deep thermal-reservoir fluid that supplies steam and hot water to all geyser basins on the west side of the Park and perhaps in the entire Yellowstone caldera. This water (T ≥350°C; δD = –149±1 ‰) is isotopically lighter than all but the farthest north, highest altitude cold springs and streams and a sinter-producing warm spring (δD = –153 ‰) north of the Park. Derivation of this deep fluid solely from present-day recharge is problematical. The designation of source areas depends on assumptions about the age of the deep water, which in turn depend on assumptions about the nature of the deep thermal system. Modeling, based on published chloride-flux studies of thermal waters, suggests that for a 0.5- to 4-km-deep reservoir the residence time of most of the thermal water could be less than 1,900 years, for a piston-flow model, to more than 10,000 years, for a well-mixed model. For the piston-flow model, the deep system quickly reaches the isotopic composition of the recharge in response to climate change. For this model, stable-isotope data and geologic considerations suggest that the most likely area of recharge for the deep thermal water is in the northwestern part of the Park, in the Gallatin Range, where major north-south faults connect with the caldera. This possible recharge area for the deep thermal water is at least 20 km, and possibly as much as 70 km, from outflow in the thermal areas, indicating the presence of a hydrothermal system as large as those postulated to have operated around large, ancient igneous intrusions. For this model, the volume of isotopically light water infiltrating in the Gallatin Range during our sampling period is too small to balance the present outflow of deep water. This shortfall suggests that some recharge possibly occurred during a cooler time characterized by greater winter precipitation, such as during the Little Ice Age in the 15th century. However, this scenario requires exceptionally fast flow rates of recharge into the deep system. For the well-mixed model, the composition of the deep reservoir changes slowly in response to climate change, and a significant component of the deep thermal water could have recharged during Pleistocene glaciation. The latter interpretation is consistent with the recent discovery of warm waters in wells and springs in southern Idaho that have δD values 10–20 ‰ lower than the winter snow for their present-day high-level recharge. These waters have been interpreted to be Pleistocene in age (Smith and others, 2002). The well-mixed model permits a significant component of recharge water for the deep system to have δD values less negative than –150 ‰ and consequently for the deep system recharge to be closer to the caldera at a number of possible localitiesin the Park.

Horizontal flow in hydrothermal systems

Article

Full-text available

Jan 1973

D. c. resistivity measurements and drill hole data have shown the existence of extensive horizontal flows of hot water which originates within certain hydrothermal systems in Chile and New Zealand. The geological and hydrological conditions which favor such flows are discussed.

Biological versus inorganic processes in stromatolite morphogenesis: Observations from mineralizing sedimentary systems

Article

Jan 1994

Morphogenesis in stromatolites refers to the pattern of development that creates a megascopic laminated form through repeated cycles of sediment accretion. In general, all sedimentary laminations reflect periodic interruptions in deposition. For example, in stromatolites formed in detrital sedimentary systems, laminations may arise through variations in current velocity and rates of sedimentation (Farmer and Des Marais 1993). In mineralizing sedimentary systems, laminae may form by fluctuations of temperature, pH, or saturation (Guo and Riding 1992), or by seasonal growth cycles of organisms (Chafetz et al. 1991). Laminations can also originate by post-depositional (diagenetic) processes, such as dissolution (Ekdale and Bromley 1988).

Geysers and Geothermal Energy

Chapter

Jan 1980

John S. Rinehart

Hot springs and geysers add abnormal amounts of heat energy, mineral matter, and water to highly localized regions of a normally balanced ecosystem. As a consequence, these areas develop local anomalies in their biologic and geologic features and sometimes even modify the atmospheric environment. The extreme temperatures, violent processes, and unusual nature of such areas make them both beneficial and hazardous to plants and animals, including man.KeywordsGround MotionDrainage ChannelGround NoiseHigh Frequency PulseSteam BubbleThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Changes in heat flow associated with exploitation of Wairakei Geothermal Field, New Zealand

Article

Jan 1981

R. G. Allis

From measurements made during 1978-79 the total surface heat discharge from Wairakei hydrothermal system has been determined to have been 600 ± 150 MW. This paper describes and discusses the measurements leading to this result and compares it with the results of earlier surveys. The history of mass and heat flows since exploitation began in 1951 is discussed, and a model describing inferred changes within the 2-phase zone is presented. The analysis supports the conclusion that, while total mass flow appears now to be approaching equilibrium, approximately 800 MW of the total heat discharge continues to be derived from falling reservoir temperatures within the 2-phase zone. The 1978–79 heat flow survey has also revealed a 1 km² area between the production borefield and Geyser Valley where almost complete cessation of thermal activity has occurred. Faults through this area, which were originally conduits for the ascending hot water that emerged in Geyser Valley, may now be permitting downward infiltration of cold surface water.

Volcanos of the Central Andes

Article

Jan 1991

Hydrothermal systems: Doorways to early biosphere evolution

Article

Jan 2000

Jack D Farmer

Hydrothermal systems may have provided favorable environments for the prebiotic synthesis of organic compounds necessary for life and may also have been a site for life's origin. They could also have provided a refuge for thermophilic (heat-loving) microorganisms during late, giant-impact events. Phylogenetic information encoded in the genomes of extant thermophiles provides important clues about this early period of biosphere development that are broadly consistent with geological evidence for Archean environments. Hydrothermal environments often exhibit high rates of mineralization, which favors microbial fossilization. Thus, hydrothermal deposits are often rich storehouses of paleobiologic information. This is illustrated by studies of the microbial biosedimentology of hot springs in Yellowstone National Park that provide important constraints for interpreting the fossil record of thermophilic ecosystems. Hydrothermal processes appear to be inextricably linked to planetary formation and evolution and are likely to have existed on other bodies in the solar system. Such environments may have sustained an independent, extraterrestrial origin of life. Thus, hydrothermal systems and their deposits are considered primary targets in the search for fossil evidence of life elsewhere in the solar system.

Formation of silica oncoids around geysers and hot springs at El Tatio, northern Chile

Article

Apr 1997
SEDIMENTOLOGY

Siliceous oncoids, up to 4 cm in diameter, are common on the laterally extensive sinter aprons that surround the spectacular geysers and hot springs at El Tatio in northern Chile. Many of these complex oncoids developed close to geyser and spring vents that discharge boiling water. Internally the oncoids, which are composed of precipitated amorphous silica, are formed of complex arrays of spicules and concentric laminae as well as detrital volcanic grains. Spicular growth is dominant in most examples. The formation and growth of the spicules and concentric laminae were mediated by a microbial community which included filamentous microbes, mucus, and possibly bacteria. The microbes and mucus were silicified by replacement and encrustation. In some laminae the filamentous microbes lay parallel to the growth surface; in other laminae most filaments forming the thin mats were suberect. Amorphous silica precipitated between the filaments occluded porosity and commonly disguised the microbial fabric. The oncoids grew on the proximal sinter aprons around the geyser vents and hot spring pools. Most growth took place subaerially with the silica delivered to the precipitation sites by splashing water from the geysers and/or periodic shallow flooding of the discharge aprons. Unlike silica oncoids at other geothermal sites, vertical growth of oncoids that formed in some rimstone pools was not limited by water depth.

Das Fumarolen-und Geysir-Feld westlich der Vulkangruppe des Tatio (Provinz Antofagasta, Chile)

Article

Jan 1959

Werner Zeil

Preservation of Biological Information in Thermal Spring Deposits: Developing a Strategy for the Search for Fossil Life on Mars

Article

Feb 1993

Current interpretations of the early history of Mars suggest many similarities with the early Earth and therefore raise the possibility that the Archean and Proterozoic history of life on Earth could have a counterpart on Mars. Terrestrial experience suggests that, with techniques that can be employed remotely, ancient springs, including thermal springs, could well yield important information. By delivering water and various dissolved species to the sunlit surface of Mars, springs very likely created an environment suitable for life, which could have been difficult, if not impossible, to attain elsewhere. The chemical and temperature gradients associated with thermal springs sort organisms into sharply delineated, distinctive and different communities, and so diverse organisms are concentrated into relatively small areas in a predictable and informative fashion. A wide range of metabolic strategies are concentrated into small areas, thus furnishing a useful and representative sampling of the existing biota. Mineral-charged springwaters frequently deposit chemical precipitates of silica and/or carbonate which incorporate microorganisms and preserve them as fossils.