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

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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
REFERENCES
Allen, E.T., and Day, A.L., 1935, Hot Springs of the
Yellowstone National Park, Publ. 466. Carnegie
Institution of Washington: Washington, D.C., 525 pp.
Allis, R.G., 1981, Changes in heat flow associated with
exploitation of Wairakei geothermal field, New
Zealand. New Zealand Journal of Geology and
Geophysics,24, 1–19.
Andres, L.R., Raul, M.R., and Hugh, R.V., 1998, Energía
Eólica y Geotérmica en Chile: Evaluación de su
potencial y desarrollo (unpublished paper on wind and
geothermal energy in Chile). Pontificia Universidad
Católica de Chile: Chile, 30 pp.
Bernhardson, W, 2000, Chile & Easter Island. 5th edition.
Lonely Planet Publications: Melbourne, Australia, 599
pp.
Bertrand, A., 1885, Memoria sobre las cordilleras del
desierto de Atacama y regiónes limítrofes, presentada
al señor ministro del interior. Imprenta nacional:
Santiago, Chile, 304pp.
Brueggen, J., 1943, Los geisers de los volcanes del Tatio.
Rev. Chil. Hist. Geogr. 101, 236.
Bryan, T.S., 2001, The Geysers of Yellowstone. 3rd edition.
Colorado University Press: Boulder, Colorado, 472 pp.
Collar, R.J., 1990, Causes for the decline of hot spring
and geyser activity, Steamboat Springs, Nevada.
Master’s Thesis. San Diego State University: San
Diego, California, 327 pp.
Cusicanqui, H., Mahon, W.A., and Ellis, A.J., 1976, The
geochemistry of the El Tatio Geothermal Field,
northern Chile. In Proceedings of the 2nd United
Nations Symposium on Geothermal Fields, Berkeley,
California, pp. 703–711.
de Silva, S.L., and Francis, P.W., 1991, Volcanoes of the
Central Andes. Springer–Verlag: New York, 216 pp.
ENTEL Antofagasta, 2002, Misterios del Tatio. Santiago,
Chile, 1 p. www.puntoantofagasta.cl/.
Farmer, J.D., 2000, Hydrothermal systems: doorways to
early biosphere evolution. GSA Today 10, 7, 1–2.
Farmer, J.D., and Des Marais, D.J., 1994, Biological
versus inorganic processes in stromatolite morphogen-
esis: observations from mineralizing systems. In L.J.
Stal and P. Caumette (Eds.), Microbial mats: struc-
ture, development, and environmental significance.
Springer–Verlag: Berlin, pp. 61–68.
Filipponi, A., 1953, Energía geotérmica del Tatio chileno.
Scientia Año XX, 74.
Filipponi, A., 1960, Electrifación del norte con energía
geotérmica del Tatio chileno (2 parts), Universidad de
Chile Boletín, I part no. 16, p. 4; II part no. 17–18, p.
42.
Graham, M., Sainsbury, C., and Danbury, R., 1999,
Chile: The Rough Guide. Rough Guides Ltd: London,
UK, 488 pp.
Healy, J., and Hochstein, M.P., 1973, Horizontal flow in
hydrothermal systems. Journal of Hydrology (New
Zealand) 12, 71–82.
Hroarsson, B., and Jonsson, S.S., 1992, Geysers and Hot
Springs in Iceland. Mal og Menning: Reykjavik,
Iceland, 158pp.
Instituto Geográfico Militar, 1985, Cerros de Tocorpuri
2215–6745 [map]. 1st edition. 1:50,000 scale. Instituto
Geográfico Militar: Santiago, Chile.
Instituto Geográfico Militar, 2001a, Mauque A–045
[map]. 2nd edition. 1:50,000 scale. Instituto Geográfico
Militar: Santiago, Chile.
Instituto Geográfico Militar, 2001b, Toconce 2215–6800
[map]. 1st edition. 1:50,000 scale. Instituto Geográfico
Militar: Santiago, Chile.
Jones, B., and Renaut, R.W., 1997, Formation of silica
oncoids around geysers and hot springs at El Tatio,
northern Chile. Sedimentology 44, 287–304.
La Estrella de Loa, 12 January 2001, “Alarma por
supuesta bomba en El Tatio.”
La Estrella de Loa, 7 October 2002, “Turista español se
quemó en los Géisers del Tatio.”
La Estrella de Loa, 16 July 2003, “Géiser ofrecieron
espectáculo único.”
Lahsen, A., and Trujillo, P., 1976, El Tatio Geothermal
Field. In Proceedings of the 2nd United Nations
Symposium on Geothermal Fields. Berkeley, Califor-
nia, pp. 157–158.
78 The GOSA Transactions Volume VIII
Rinehart, J.S., 1980, Geysers and Geothermal Energy.
Springer–Verlag: New York, 223 pp.
Rye, R.O. and Truesdell, A.H., 1993, The question of
recharge to the geysers and hot springs of Yellowstone
National Park. U.S. Geological Survey, Open–File
Report 93–384, 40 pp.
Sorey, M.L., 2000, Geothermal development and changes
in surficial features: examples from the Western
United States. In Proceedings of the World Geother-
mal Conference, Kyushu – Tohuku, Japan, May 28 –
June 10, 2000, p. 705–711.
Sundt, L., 1909, Estudios geológicos y topográficos del
Desierto y Puna de Atacama. Two parts. Santiago de
Chile, 212 pp.
Tocchi, E., 1923, Studio geologico e geotermico del Tatio
cileno. Reserved report to Larderello S.A.: Italy.
Trujillo, P., 1969, Estudio para el desarollo geotermico en
el norte de Chile – Manifestaciónes termales de El
Tatio, Provencia de Antofagasta: CORFO Project
Report.
Trujillo, P., Lahsen, A., and Varar, J., 1969, Estudio
Geotermico Manifestaciones Termales Superficiales
de El Tatio [map]. 1:10,000 scale. Photocopy, approxi-
mately 60–by–60 centimeters.
Walter, M.R., and Des Marais, D.J., 1993, Preservation of
biological information in thermal spring deposits:
developing a strategy for the search for fossil life on
Mars. Icarus,101, 129–143.
White, D.E., 1968, Hydrology, activity, and heat flow of
the Steamboat Springs thermal system, Washoe
County, Nevada. U.S. Geological Survey Professional
Paper 458–C, 109 pp.
White, D.E., 1998, The Beowawe Geysers, Nevada,
before geothermal development. U.S. Geological
Survey Bulletin 998, 25 pp.
Zeil, W., 1956, Theoretical and experimental study of the
possible use of geothermal energy provided by the
geysers and fumaroles of El Tatio. In Siegel [thesis]:
Universidad de Chile: Santiago.
Zeil, W., 1959, Das Fumarolen– und Geysir–Feld
westlich der Vulkangruppe des Tatio (Provinz
Antofagasta, Chile). Bayerische Akademie der
Wissenschaften, Abhandlung der Mathematisch–
Naturwissenschaftliche Klasse: Muenchen,
Deutschland, n. 96, 22 pp.
Zúñiga, C.M. (CTC generente general), 2001, TURISTEL
Norte Guía Turística de Chile. Telefónica CTC Chile:
Santiago, Chile, 240 pp.
Alan Glennon has visited several of the world’s geyser areas. This photo, taken in
2003, shows a small geyser at HvHv
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... The El Tatio geothermal field is located in the Chilean Altiplano at an elevation of 4200 m above sea level (Fig. 1). It is the largest geyser field in the southern hemisphere and the third largest in the world (approximately 10% of the geysers in the world), covering more than 30 km 2 and containing more than two hundred active geothermal manifestations such as: geysers, perpetual spouters, fumaroles, hot spring pools and mud-pools (e.g., Glennon and Pfaff, 2003;Munoz-Saez et al. 2018). ...
... Other studies in the 1970's included geochemical analysis (Cusicanqui 1975;Giggenbach 1978) and geophysical imaging using Vertical Electrical Soundings (Lahsen and Trujillo 1976). In the last two decades, new studies were conducted to understand the large-scale dynamics of the geothermal area (e.g., Cortecci et al. 2005;Glennon and Pfaff, 2003;Lucchi et al. 2009;Mourguesr, 2017;Munoz-Saez et al. 2015, 2018Tassi et al. 2010;Cumming et al. 2002;Ardid et al. 2019;Figueroa 2019). Most of these previous studies were on a regional scale, providing insights into the subsurface water flow, possible geothermal heat source, and electrical resistivities at kilometer scale. ...
... However, Lucchi et al. (2009) proposed that the structural pattern of El Tatio consists mainly of thrust faults largely striking NNE-SSW, intersected by local NW-SE trending lineaments. Most of geothermal manifestations in El Tatio are distributed along three basins: The Upper, Middle and Lower Basin (Glennon and Pfaff, 2003). Here, we focus on the Upper Basin (UB) and the Middle Basin (MB), which are two largest (Fig. 1). ...
Article
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.
... The correlation between chloride, HCO 3 /SO 4 and Na/K presented above, allows us to segment the whole geothermal field into five groups illustrated in Fig. 9D: (a) Steam Heated group feeded by meteoric recharge (SHg m ), characterized by acid-sulfate waters in perched aquifers with low amounts of chloride, low HCO 3 -SO 4 ratios and low Na-K ratios, (b) Peripheral water group feeded by the reservoirs A and B (Pg AB ), characterized by bicarbonate waters with low amounts of chloride, very high HCO 3 -SO 4 ratios and intermediate Na-K ratios, (c) Geysers group feeded by the reservoirs A and B (Gg AB ), characterized by the presence of active geysers with intermediate and high amounts of chloride, HCO 3 /SO 4 and Na/K, (d) Boiling Pools group feeded by the reservoir B (BPg B ), characterized by the presence of very hot pools of different diameter with high amounts of chloride, HCO 3 /SO 4 and Na/K, and (e) Deep Wells group feed by the reservoir A (DWg A ), where waters are taken by deep wells. Following the segmentation for the El Tatio geothermal field proposed by Glennon and Pfaff (2003), the group Gg AB is in the upper and lower basins, while groups BPg B and DWg A are in the middle basin. In this work, we propose an extension of the segmentation proposed by Glennon and Pfaff (2003), incorporating the outer basin (Pg AB ) and the inner basin (SHg m ). ...
... Following the segmentation for the El Tatio geothermal field proposed by Glennon and Pfaff (2003), the group Gg AB is in the upper and lower basins, while groups BPg B and DWg A are in the middle basin. In this work, we propose an extension of the segmentation proposed by Glennon and Pfaff (2003), incorporating the outer basin (Pg AB ) and the inner basin (SHg m ). The geochemistry of the system here investigated shows that the El Tatio-La Torta must be a volcanic field type (Moeck, 2014) composed by a high-enthalpy reservoir system with neutral sodium-chloride waters at different temperatures. ...
Article
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.
... El Tatio geyser field is located in the Atacama desert of northern Chile (Figure 1a). Here more than 200 thermal features (Glennon & Pfaff, 2003) discharge regionally derived meteoric water (e.g., Munoz-Saez et al., 2018) mixed with magmatic fluids (e.g., Tassi et al., 2010). Of the thermal features, about 80 are geysers that erupt periodically or episodically at the local boiling temperature of water (86.6°C). ...
... There are active geysers between 20 and 70 m from El Jefe. In addition, Glennon and Pfaff (2003) catalog a series of other geysers that are now inactive around El Jefe, but these may still have subsurface activity. ...
Article
Full-text available
Broadband seismic data were recorded on ground surface around an exceptionally regular eruptive system, geyser "El Jefe", in the El Tatio geyser field, Chile. We identify two stages in the eruption, recharge and discharge, characterized by a radial expansion and contraction, respectively, of the surface around the geyser. We model the deformation with spherical sources that vary in size, location and pressure, constrained by pressure observations inside the conduit that are highly correlated with deformation signals. We find that in order to fit the data, the subsurface pressure sources must be laterally offset from the geyser vent during the recharge phase, and that they must migrate upwards towards the vent during the eruption phase. This pattern is consistent with models in which ascending fluids accumulate and then are released from a bubble trap that is horizontally offset from the shallow conduit of the geyser.
... The hydrothermal area comprises more than 80 active geysers and thermal manifestations that expand over 30 km 2 at elevations from 4,200 to 4,600 m.a.s.l. (Glennon and Pfaff, 2003;Fernández-Turiel et al., 2005). Hydrothermal fluids are mostly meteoric, with minor magmatic components. ...
Article
Full-text available
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.
... The El Tatio geothermal field is located in the Andes Mountains of northern Chile, 80 km north of San Pedro de Atacama (Figure 1a). El Tatio contains the world's highest geyser field (~4300 m), and the largest geyser field in the Southern Hemisphere (~30 km 2 ) (Glennon & Pfaff, 2003;Jones & Renaut, 1997;Munoz-Saez et al., 2018;Tassi et al., 2005;Trujillo 1969;Zeil, 1959). The extreme altitude of El Tatio produces a unique environment relative to other hydrothermal localities. ...
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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.
... ETGF, El Tatio Geyser Field. Pfaff, 2003). The Lower Basin lies along the banks of the R io Salado, the headwaters of which are formed by geyser effluent from all three basins ( Figure S1). ...
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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.
... The ETGF is a complex volcanic geothermal field comprised of several hot springs, spouting pools, mud pots, mounds, and well water (Fernandez-Turiel et al. 2005). These water bodies are mainly characterized has having high temperatures, low pH, high concentrations of non-toxic ions (chlorides, sulfates, sodium and potassium), and toxic (arsenic, boron, antimony and lithium) dissolved minerals (Cortecci et al. 2005;Engel et al. 2013;Glennon and Pfaff 2003;Landrum et al. 2009). The extraordinary conditions at the ETGF have stimulated interests of researchers, who have focused their efforts on potential resources of geothermal energy (Breeze 2014) and the origin of life on earth (Mulkidjanian et al. 2012). ...
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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.
... The El Tatio geothermal field is located in the Andes Mountains of northern Chile,10 km west of the Chile-Bolivia border and 80 km north of San Pedro de Atacama (Fig. 1A). El Tatio contains the world's highest geyser field (~4300 m a.s.l.), and the largest geyser field (~30 km 2 ) in the Southern Hemisphere (Zeil, 1959;Trujillo et al., 1969;Jones & Renaut, 1997;Glennon and Pfaff, 2003;Tassi et al., 2005;Munoz-Saez et al., 2018). The extreme altitude of El Tatio produces a different environment compared with many sinter locations. ...
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Siliceous sinter deposits from El Tatio, Chile, preserve a wide variety of depositional environments and biosignatures, from high-temperature (~85 °C) vent-proximal facies to distal deposits dominated by silicified microbial mats. Four cores were drilled into an El Tatio sinster mound and associated distal apron to investigate changes in hydrothermal environments over geologic timescales. Sedimentary and geochemical analysis of multiple sinter cores records the initiation and accretion of diverse depositional features still observed today in El Tatio. Facies adjacent to hydrothermal vents are dominated by laminated sinter crusts on the steep margins of a high-temperature pool, with sparse microbial preservation. Outer margins of the same pool contain extensive sinter columns up to ten centimeters in length, precipitated during repeated cycles of pool overflow and subsequent evaporation. Low-relief hydrothermal pools also form minor deposits within distal debris aprons, and analogous pools are still active close to sampling locations. Debris aprons are dominated by palisade, tufted, and arborescent microbial fabrics, with distinct mat textures revealing well preserved microfossils. Surficial deposits in all cores feature detrital-rich and microbially-influenced sinters overlying higher-temperature facies, indicating a relative decrease in hydrothermal activity over time. Geochemical proxies for hydrothermal fluids and detrital input match depositional interpretations based on sedimentary structures. ¹⁴C ages from core deposits extend the mound's history by 11,000 years, recording at least three thousand years of sinter deposition on top of glacial sandstones (13,337–10,232 y. cal. BP). Importantly, this work provides a detailed depositional model unavailable through surficial sedimentology alone.
... This location is noteworthy for its high evaporation and low precipitation rates, high solar ultraviolet flux, and diurnal freeze-thaw conditions (Nicolau et al., 2014), which provide more Mars-like conditions than most hydrothermal settings on the Earth (Ruff and Farmer, 2016). More than 100 geysers and other manifestations, including flowing hot springs, hot pools, mud pots, and fumaroles, have been documented, spanning an area of *10 km 2 (Glennon and Pfaff, 2003). Discharging waters are of alkali-chloride composition at near neutral pH (Nicolau et al., 2014). ...
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The origin and age of opaline silica deposits discovered by the Spirit rover adjacent to the Home Plate feature in the Columbia Hills of Gusev crater remains debated, in part because of their proximity to sulfur-rich soils. Processes related to fumarolic activity and to hot springs and/or geysers are the leading candidates. Both processes are known to produce opaline silica on Earth, but with differences in composition, morphology, texture, and stratigraphy. Here, we incorporate new and existing observations of the Home Plate region with observations from field and laboratory work to address the competing hypotheses. The results, which include new evidence for a hot spring vent mound, demonstrate that a volcanic hydrothermal system manifesting both hot spring/geyser and fumarolic activity best explains the opaline silica rocks and proximal S-rich materials, respectively. The opaline silica rocks most likely are sinter deposits derived from hot spring activity. Stratigraphic evidence indicates that their deposition occurred before the emplacement of the volcaniclastic deposits comprising Home Plate and nearby ridges. Because sinter deposits throughout geologic history on Earth preserve evidence for microbial life, they are a key target in the search for ancient life on Mars.
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Mud volcanoes are widespread both on land and in marine basins, in collision and transtensional settings (e.g., Kholodov 2002; Limonov 2004). The main conditions for mud volcano formation are a thick sedimentary cover (several kilometers) and plastic clayey components with an anomalously high formation of pore pressure and the presence of thermal water (Pilchin 1985b; Limonov 2004). Currently, more than 900 terrestrial and 800 offshore mud volcanoes are known or presumed to exist (Dimitrov 2002). More than a quarter of all the known mud volcanoes are concentrated within the Caucasus (e.g., Kadirov et al. 2005) and most (more than 220) (Kholodov 2002) are located within the ‘‘Abich triangle’’ (Abich 1863) near Baku, Azerbaijan. One of the most interesting problems in oil and gas geology is related to the genesis of mud volcanoes and their relationship to oil and gas fields and deposits. A mud volcano is a tectonic structure formed during the formation and eruption of significant amounts of water-rich sedimentary rocks (mostly clays and/or silts) in regions usually characterized by enormous amounts of sedimentary deposits collected over a short time. As it erupts, a mud volcano forms a mound up to a few 100 m high. They are known to form both onshore and offshore, and can in some cases create huge island structures (e.g., Bulla Island in the Caspian Sea). Researchers usually make a distinction between mud intrusions (called mud diapirs) and extrusions (called mud volcanos) (Dimitrov 2002), even though their origin can be similar. The term sedimentary volcanism is also used to refer to mud volcanoes (Kopf 2002). In many cases, the appearance of mud volcanoes is linked to regions of formation of oil and gas fields, volcanic and seismic activity, and orogenic belts (Kopf 2002).
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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.
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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.
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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.