Tracy K.P Gregg

University at Buffalo, State University of New York | SUNY Buffalo · Department of Geology

We have constructed a global geologic map of the minor planet Vesta at 1:300,000-scale using Dawn spacecraft imaging, spectroscopic, topographic, and elemental data. In this effort, we used a mapping method that requires creating two maps independently: the first map uses morphology and topography to define map units, while the second map relies on...

We examine unconformable lobate deposits along the north-facing slopes of Alba Patera (40°N 250°E with an elevation of ~6 km), Mars, using data from the Mars Reconnaissance Orbiter Context Camera, High-Resolution Imaging Science Experiment, and the Mars Orbiter Laser Altimeter. We interpret the lobate north-facing slope deposits (NSFDs) to be small...

Much has been discovered about volcanism on Mars over the past fifty years of space exploration. Previous reviews of these discoveries have generally focused on the volcanic constructs (e.g., Olympus Mons and the other volcanoes within the Tharsis and Elysium regions), the analysis of individual lava flows, and how this activity has evolved over ti...

Cryovolcanism has been either observed on or suspected for numerous icy bodies across the Solar System, most notably Saturn’s tiny moon Enceladus, where jets of water vapor and other constituents are spewed into space from giant fractures near the South Pole. In this chapter, we review cryomagmatism and cryovolcanism, which are the subsurface and s...

On Earth, volcanological studies are commonly motivated by natural disaster prevention: understanding how volcanoes work helps us to predict their behaviors, thereby helping to save human lives. Volcanic risks to human life and property are not (yet!) an extraterrestrial concern, so our drive to understand volcanism throughout the Solar System is u...

On Earth, geologists have many techniques available to determine the absolute ages of minerals, rocks, and unconsolidated deposits; but obtaining absolute ages requires actual samples of materials collected in controlled ways from known locations. To date, such samples exist only for a handful of locations on the lunar surface. For all other extrat...

This volume is the first in a series intended to introduce the concept of comparative planetology to geoscientists who, to date, have only considered processes on a single world. The following chapters describe igneous processes throughout the Solar System. Herein, we define a volcano as an area on the surface of solid planetary body (a planet, a m...

Io is a priority destination for solar system exploration. The scope and importance of science questions at Io necessitates a broad portfolio of research and analysis, telescopic observations, and planetary missions — including a dedicated New Frontiers class Io mission.

Io is a priority destination for solar system exploration, as it is the best natural laboratory to study the intertwined processes of tidal heating, extreme volcanism, and atmosphere-magnetosphere interactions. Io exploration is relevant to understanding terrestrial worlds (including the early Earth), ocean worlds, and exoplanets across the cosmos.

Syrtis Major Planum (centered at 9.2°N, 67.1°E) is a unique volcano on Mars. Its large (1300 km) diameter and low summit height (~ 2 km) give flank slopes of < 1°. Lava flow lobes, channels, and tubes are identified on Syrtis Major Planum's flanks. Intersecting wrinkle ridges, similar to those found on other Martian planitia, cover Syrtis Major Pla...

The Medusae Fossae Formation (MFF) is hypothesized to be an enormous deposit of pyroclastic material, generated during explosive eruptions from unknown volcanic vents. Investigation of these materials has been hampered for decades by dust that hides the surface rocks from easy remote observation. The MFF materials have been sculpted by sand and win...

All solid planetary bodies in the in the Solar System are either currently volcanically active or have been active in the past. By comparing the volcanic compositions and eruption styles observed throughout the Solar System, commonalities and differences help to reveal how different planetary bodies, with distinct chemical makeup, have evolved thro...

Most lava flows have been emplaced away from the watchful eyes of volcanologists, so there is a desire to use solidified lava-flow morphologies to reveal important information about the eruption that formed them. Our current understanding of the relationship between solidified basaltic lava morphology and the responsible eruption and emplacement pr...

Although Earth is the only planet in the solar system with active plate tectonics, the planetary bodies of the inner solar system (Mercury, Venus, the Moon, and Mars) display a familiar array of tectonic and volcanic features. Nonexplosive eruptions of basaltic lava are the most common volcanic activity on Earth and appear to have been the dominant...

DefinitionLow-relief volcano displaying broad, low-sloped, heavily radially channeled flanks and complex central calderas on Mars.SynonymsAsh shield; Hellas rim structure (obsolete); Highland volcanoDescriptionPositive-relief, low-lying construct with a prominent central caldera (or caldera complex) and flank slopes of 1990). Paterae on Mars have l...

We present characterizations of erosional patterns for terrestrial ignimbrites and lava flow fields for comparisons with eroded terrains on Mars.

Hollow cylinders of basalt < 2.5 m tall and generally < 1 m in diameter were generated by non-explosive lava–water interactions during the emplacement of the Laki lava flow in Iceland during 1783–1784. We know of only one location within the Laki lava flow where these basalt formations occur: a valley called Skaelingar, located at ~ 64.0°N, 18.5°W,...

Although mid-ocean ridge (MOR) magmatism is estimated to account for 75% of the recent global magmatic budget [Crisp, 1984], volcanic eruptions on submarine MOR's are notoriously difficult to observe directly, and their study necessitates a variety of unconventional approaches. Along the global MOR system, the products of only about two-dozen subma...

Eruptions on the seafloor are notoriously difficult to observe, map, and document. As a result, the rates of volcanism and controlling factors are very poorly constrained for the Earth's largest volcanic system. In lieu of direct observation, lava morphology provides a remarkably good proxy of the eruptive dynamics on the seafloor, albeit only semi...

The discovery of numerous extra-terrestrial volcanoes, including active ones, has stretched our traditional definition of what is a volcano. We now know that the nature of volcanism is highly variable over the Solar System, and the traditional definition of a volcano as defined for Earth needs to be modified and expanded to include processes such a...

We statistically examine the spatial distribution of volcanic edifices within fields on the terrestrial planets.

We present our efforts to constrain the lithologies of Tyrrhena Patera flank materials and the ridged plains of Hesperia Planum using MOC and HiRISE images.

Overview Volcanism is of primary importance in shaping the surfaces of many planets and satellites of the Solar System. In this chapter we show how models developed for volcanic processes on Earth can be adapted to model volcanism on other planetary bodies, including those displaying familiar silicate volcanism (such as Mars, Venus, and the Moon),...

Overview The most abundant and widespread volcanic behavior on Earth is the effusive eruption of basaltic lava on the ocean floors – most of it from mid-ocean ridge eruptions. The inaccessibility of the deep (> 500 m below sea level) sea floor limits direct observations of submarine volcanic phenomena. Observations of volcanic products are therefor...

Understanding the physical behavior of volcanoes is key to mitigating the hazards active volcanoes pose to the ever-increasing populations living nearby. The processes involved in volcanic eruptions are driven by a series of interlinked physical phenomena, and to fully understand these, volcanologists must employ various physics subdisciplines. Thi...

The volcano Tyrrhena Patera (22°S, 108°E), Mars, is a low-relief structure with a central caldera complex, and whose flanks are dissected by broad (< 5 km wide), flat-floored radiating channels. The morphology of the volcano flanks is consistent with eroded, differentially welded pyroclastic flows. Hesperian- aged plains materials embay the volcano...

Observations of active dacite domes and evolved (SiO2 wt.% >65) plinian-style eruptions are considered to reveal typical behaviors of Si-rich volcanic systems. However, despite lack of mention in modern volcanology textbooks, large-volume (>4 km3) evolved lava flows exist globally. These large- volume evolved lava flows have many characteristics in...

NASA's Planetary Geology and Geophysics Program began funding PGGURP in 1978, in an effort to help planetary scientists deal with what was then seen as a flood of Viking Orbiter data. Each subsequent year, PGGURP has paired 8 - 15 undergraduates with NASA-funded Principal Investigators (PIs) around the country for approximately 8 weeks during the s...

Monogenetic basaltic volcanoes are the most common volcanic landforms on the continents. They encompass a range of morphologies from small pyroclastic constructs to larger shields and reflect a wide range of eruptive processes. This paper reviews physical volcanological aspects of continental basaltic eruptions that are driven primarily by magmatic...

Loki Patera (310° W, 12° N) is Io's largest patera at ∼180 km in diameter. Its morphology and distinct thermal behavior have led researchers to hypothesize that Loki Patera may either be an active lava lake that experiences periodic overturn, or a shallow depression whose floor is episodically resurfaced with thin flows. Using results from mathemat...

To determine if there is a systematic distribution of transverse aeolian ridges (TARs) across the martian dichotomy boundary, we examined Mars Orbiter Camera (MOC) images from 60°N to 60°S and 0° to 20°W.

A general petrogenetic model illustrates processes in most, if not all, vent fields in plains-style volcanic settings. Low shields in the Tharsis region could be targets to evaluate possible serial magmatism and source mixing.

Volcanic flows in our solar system are remarkably varied. Io and Titan are particularly good examples of relatively large bodies that have erupted a variety of flows, ranging from basaltic and possibly sulfur and ultramafic lavas on Io to mixtures of water and possibly ammonia and methanol on Titan. These exotic extraterrestrial flows can be much d...

The morphology of materials on the floor of Gusev Crater (14° S, 175° W), Mars, imply a history of volcanism and subsequent removal of an ice-rich deposit. Fluid lava flows observed in the western portion of Gusev Crater paradoxically terminate in a steep, thick (< 60 m) flow front adjacent to hummocky terrain. The hummocky terrain is morphological...

High Resolution Stereo Camera (HRSC) images of Hadriaca Patera, Mars, in combination with Mars Orbiter Camera (MOC), Mars Orbiter Laser Altimeter (MOLA), and Thermal Infrared Imaging System (THEMIS) data sets, reveal morphologic details about this volcano and enable determination of a chronology of the major geologic events through new cratering ag...

Channeled lava flows, hundreds of kilometers long, are common on the lower flanks of the Tharsis Montes on Mars. Our analysis of a 690-km-long lava flow along the southwest perimeter of Ascraeus Mons shows that it was emplaced on low local slopes (100 km in length, but the maximum effusion rates necessary on Earth are essentially the minimum for Ma...

The distribution and nature of sedimentary and volcanic units within southern Hesperia Planum is examined and new constraints on the formation and modification of Hesperia Planum are provided from crater statistics.

The ridged plains of Hesperia Planum, Mars, are not a single geologic unit emplaced at the same geologic time.

Growndwater flow and valley discharge is evaluated for highland basins and their surrounding watersheds in the highlands near Hesperia Planum, Mars.

We will discuss the constraints on Mars platy terrain from models, etc.

Hesperia Planum is characterized by a vast expanse (> 2 million square kilometers) of ridged plains that fill a depression in the cratered highlands NE of Hellas Basin. Hesperia Planum also contains Tyrrhena Patera, an ancient volcano thought to be composed of a main shield of pyroclastic deposits and a flank unit of lava flows that extends SW for...

The Bruneau-Jarbidge eruptive center (BJEC) in southwestern Idaho is responsible for more than 10 large- volume lava flows ranging from a few km3 to > 200 km3. These Miocene flows have high SiO2 contents of between 70 and 75 wt% and range in thickness from a few tens of meters to 200 m thick. Well exposed in deep canyon walls, these flows typically...

To constrain the behavior of Ionian volcanic paterae in general, and Loki Patera in particular, we have used the following techniques in concert: 1) geologic mapping and analyses; 2) laboratory simulations; and 3) mathematical modeling. Here, we present preliminary results from the synthesis of these data. Loki Patera (310°W, 12°°N) is significantl...

Tyrrhena Patera (22°S, 104°E), Mars, is a low-relief (1800 m maximum relief), central-vent volcano whose flanks are dissected with broad (∼5 km wide), flat-floored channels. The easily eroded nature of the shield materials, combined with extremely low flank slopes (≤ 2.0°), suggest that Tyrrhena Patera is composed of pyroclastic materials. These sh...

Laboratory simulations using polyethylene glycol (PEG) extruded at a constant rate and temperature into a tank with a uniform basal slope and filled with a cold sucrose solution generate channels that are defined by stationary levees and mobile flow interiors. These laboratory channels consistently display the following surface textures in the chan...

Detailed investigation of hummocky terrain on the floor of Gusev crater, Mars, reveals robust similarities with terrestrial glaciated landscapes.

Laboratory simulations and mathematical models test lava lake hypotheses for the formation of Loki Patera, Io.

A morphological investigation of the Ionian paterae containing islands suggests that the islands are not solidified rafts of crust.

Overview of morphological analysis done on paterae with bright ”islands”

Analysis of the morphology for a ~365 km long lava flow near Ascraeus Mons.

We develop maps of roughness statistics of analog lava flows in Hawaii to identify the topographic resolution required to constrain the emplacement of volcanic features on the surface of Mars.

One of the more surprising discoveries from the Magellan imaging campaign was that the impact craters have a spatial distribution closely consistent with a random pattern. First impressions of most craters were that they are also well preserved. These observations led to an initial post-Magellan consensus that the planet is nearly geologically inac...

1] The orthogonal pattern of NE and NW striking wrinkle ridges in Hesperia Planum makes this area unique and enigmatic. The wrinkle ridge morphologies revealed in Mars Orbiter Laser Altimeter topography across ridge structures in Hesperia Planum suggest that wrinkle ridges form above thrust faults. The timing relationship among wrinkle ridge sets i...

An analysis of stable, transitional, and dispersed flow zones in Martian lava channels. These zones have been observed in terrestrial lava channels and simulated channels. We present a comparative study of terrestrial, PEG, and Martian channels.

We have used images obtained by the High Resolution Stereo Camera (HRSC) on the ESA Mars Express orbiter to assess geologic activity at two of Mars' highland volcanoes: Hadriaca Patera and Tyrrhena Patera. HRSC images cover wide swaths at consistent lighting conditions and resolutions, making them ideal resources for assessing surfaces ages using c...

This study shows a positive correlation between a strong diktytaxitic texture and increased summit steepness among ESRP basaltic shield volcanoes.

Hesperia Planum is the type locale for "Hesperian ridged plains" on Mars, and is commonly believed to be composed of flood lavas. However, its surface may not be entirely Hesperian, nor composed of a single material unit. We present alternative interpretations for Hesperia Planum.

Geochemical models of magma evolution, oxygen fugacity determinations, and variable eruptive temperatures of plains-style basalts suggest an extensive system of small mafic intrusions beneath the volcanic plains.

Observations of active basalt, dacite, and polyethylene glycol (PEG) flows suggest that the channel-forming process is similar through various scales and is independent of composition. Specifically, analysis of subaerial and simulated flows shows the systematic formation of channel zones (stable, transitional, zone of dispersed flow), as described...

Although less well known than their smaller counterparts, large-volume (>4 km3) evolved lavas (SiO2 > 60%) are common and contribute significantly to the volume of continental crust. However, little is known about the eruption and emplacement of evolved flows as they have not yet been observed while active. In the western Snake River Plains (SRP),...

Basaltic volcanism is the predominant volcanic mode for the terrestrial planets, and constraining basaltic emplacement styles and rates is key in estimating regional resurfacing rates, eruption durations, etc. In this study, we combine field and remote sensing data to constrain emplacement styles and eruption rates. For field approaches, we examine...

Jupiter's moon Io is the most volcanically active body in the Solar System. The Galileo spacecraft spent nearly 8 years in orbit around Jupiter, making several close passes of Io and obtaining numerous observations in visible and IR wavelengths that have led to a new view of how magma erupts on Io's surface. We now know of at least 166 active volca...

We have brought together a group of respected and well-known female planetary volcanologists to create a book designed to encourage young women to pursue scientific careers. The book, entitled "Volcanic Worlds: Exploring the Solar System's Volcanoes," published by Praxis, is written for undergraduates who may have no background in geology or planet...

Rock Corral Butte (RCB) is a basaltic shield volcano located at 43° 22.25'N, 113° 1.20'W within the Eastern Snake River Plains. The summit region is characterized by complex topography associated with late-stage eruption of spatter. Rock Corral Butte is surrounded by a large flow field (>16 km2) that is remarkable for its rolling, 2 to 4-m-scale to...

We observed active pahoehoe lobes erupted on Kilauea during May-June 1996, and found a range of emplacement styles associated with variations in local effusion rate, flow velocity, and strain rate. These emplacement styles were documented and quantified for comparison with earlier laboratory experiments.At the lowest effusion rates, velocities, and...

Mars Orbiter Laser Altimeter (MOLA) data allows insight to Martian features in great detail, revealing numerous small shields in the Tempe region, consisting of low profiles and a prominent summit caps . Terrestrial examples of this shield morphology are found on the Eastern Snake River Plain (ESRP), Idaho. This plains-style volcanism [2] allows an...

The Eastern Snake River Plains (ESRP) in Idaho have long been considered a terrestrial analog for the plains volcanism like that evident in Syria Planum and Tempe Terra, Mars. Both the ESRP and Tempe Terra are sediment-blanketed volcanic fields in areas with significant extensional faulting. Similar volcanic features can be observed throughout both...

The Cerberus Fossae and Elysium Planitia regions have been suggested as some of the youngest martian surfaces since the Viking mission, although there was doubt whether the origins were predominantly volcanic or fluvial. The Mars Global Surveyor and Mars Odyssey Missions have shown that the region is certainly young in terms of the topographic pres...

Topographic profiles and surface characteristics of small (5 - 25 km diameter) plains-style shield volcanoes on the eastern Snake River Plain (ESRP) provide a method to evaluate eruptive processes and magmatic evolution on Martian volcanic plains. The ESRP is an ideal place to observe Mars-like volcanic features where hundreds of small monogenetic...

Although there are recorded observations of active dacitic domes at Mount St. Helens, Soufriere, St. Vincent and Santiaguito, there is as yet no direct observation of an active rhyolite flow, dome or coulee. Thus, we must use numerical models and/or laboratory simulations to constrain the emplacement of evolved lavas. We have used fractals to descr...

Submarine lava channels observed on the East Pacific Rise (EPR) between 9-10° N exhibit five prominent surface textures: lobate, jumbled, lineated, folded, and smooth. These textures are similar in appearance and distribution to final morphologies observed in polyethylene glycol (PEG ) channel flows produced in laboratory simulations. Maps of the s...

[1] An extensive (106 km2) lava flow field SW of Arsia Mons contains individual lobes that are 102–103 km long, are ∼65 m thick, and display a surface ridging similar to the textures found on terrestrial andesite, dacite, and rhyolite flows, raising the question of whether large-volume evolved lava flows exist on Mars. The regularly spaced ridges o...

Previous investigators have demonstrated that submarine lava flow morphologies are the result of a complex interplay between lava rheology, effusion rate, and underlying slope. Here, we specifically investigate the relation between underlying slope and submarine lava flow morphology along three study sites of the Puna Ridge, Kilauea Volcano, Hawai′...

Paterae are the most ubiquitous volcanic construct on Io s surface. Paterae are irregular craters, or complex craters with scalloped edges, interpreted as calderas or pit craters. Data from Galileo has shown that the activity of Ionian paterae is often confined to its interior and that generally lava flows are not seen spilling out over the edges....

Prior to the Mars Global Surveyor (MGS) and Mars Odyssey (MO) missions, The Syria Planum region of Mars was noted for several clusters of small (5-100 km) shield volcanoes and collapse craters, long tube and fissure-fed lava flows, and possible volcanic vents that were thought to be nearly contemporaneous with the volcanism in the Tempe- Mareotis p...

The volcanic plains of Mars have long been thought to be analogous to the Snake River Plains (SRP), Idaho, on Earth, primarily in terms of the range of low shields, fissure eruptions, and flows that coalesce to resurface large tracts of plains regions. The Tempe region of Mars was usually the most frequently cited analog prior to the Mars Global Su...

Your division worked hard to make the Annual Meeting successful for you, and all the activity at the Planetary Division booth in the exhibit hall, the crowd at the Business Meeting, and attendance at the sessions indicate that we all had a fun and productive time! A hearty thanks to all who stopped by our booth to lend a helping hand (or just to sa...

[1] An extensive (10(6) km(2)) lava flow field SW of Arsia Mons contains individual lobes that are 10(2)-10(3) km long, are similar to65 m thick, and display a surface ridging similar to the textures found on terrestrial andesite, dacite, and rhyolite flows, raising the question of whether large-volume evolved lava flows exist on Mars. The regularl...

Polyethylene glycol (PEG) was extruded at constant rates and temperatures into a 75-cm-long tank filled with cold sucrose solution in a series of low-volume (< 2000 mL), short-duration ( 1 cm) usually comprise a hollow, internal conduit system that PEG can continue to flow through. The most striking feature of the cross-sectional morphology is the...

It is well recognized that interpretations of Mars must begin with the Earth as a reference. The most successful comparisons have focused on understanding geologic processes on the Earth well enough to extrapolate to Mars' environment. Several facets of terrestrial analog studies have been pursued and are continuing. These studies include field wor...

Side-scan sonar, submersible observations and sampling of lava flows from the East Pacific Rise, 17°–19°S constrain the character and variability of submarine volcanic eruptions along mid-ocean ridges. Nine separate lava sequences were mapped using relative age and lithological contrasts among recovered samples. Axial lengths activated during erupt...

Tyrrhena and Hadriaca Paterae are low-relief central-vent volcanoes with shallowly sloping flanks dissected by radial channels. We present results of our investigations of channel formation, the Tyrrhena Patera lava flow field, and the relation between Hesperia Planum and Tyrrhena Patera. Additional information is contained in the original extended...

Eruption styles on the subaerial East Rift Zone (ERZ) of Kilauea volcano are reviewed and a classification scheme for the different types of eruption is proposed. The various eruption types are produced by differing thermal and driving pressure behaviour in the feeder dikes. Existing evidence is reviewed and new evidence presented of the types and...

Constraints on the nature of the erosion surrounding Tyrrhena Patera will reveal important information about the volatile and climatic history of the region by providing estimates of the eroded volumes and erosion styles.

Wrinkle ridges are linear to arcuate, asymmetric, topographic highs; the precise origin is unknown. Study results reveal NE-striking wrinkle ridges formed prior to NW-striking wrinkle ridges, and the deposits of Hesperia Planum are thin,

Sabancaya volcano, Peru displays a large (~60 km2) andesitic flow field comprising 39 individual lobes. Our understanding of the behavior of evolved lava flows on Earth is limited, and we must understand the terrestrial analogs before we can hope to understand their behavior on Mars and Venus.

A lava flow field located SW of Arsia Mons is characterized by flow lobes with thick flow fronts (30 - 100 m) and ridged surfaces. This indicates a possible evolved composition. Mathematical models are used to estimate and compare the rheologic characteristics of the flow field.

Because an active lava flow has yet to be observed on Mars, and available data on surface composition is of limited scope (e.g., the SNC meteorites, or data collected by Sojourner) or resolution (e.g., the Mars Global Surveyor Thermal Emissions Spectrometer [MGS TES]), Martian eruption and emplacement parameters must be inferred from the resulting...