Geology topics

James R. Zimbelman

Publications and source records attributed to James R. Zimbelman.

7 recordsLinked to original sources

USGS2021

Aeolian processes and landforms across the Solar System: Science and technology requirements for the next decade

Discussions of planetary atmospheric-surface interactions (including aeolian processes and phenomena and the resulting landforms) are often tied to a specific planetary body. Considering this, a series of workshops were initiated in 2008 to facilitate an interdisciplinary and interplanetary body approach to further our understanding of aeolian processes, phenomena, and landforms (Titus et al., 2008, 2010, 2012, 2015, 2017). The most recent workshop, held 12-13 May 2020, transitioned to a virtual format due to the COVID-19 pandemic, with a specific focus on the planetary aeolian community’s vision for the next decade. Discussions centered around dynamics and resulting landforms, missions and models, and facilities. Participants determined that a planetary aeolian goals-and-objectives document was needed that was inclusive of multiple planetary bodies, processes, and phenomena that all intersect where the surface meets the atmosphere. This white paper is the first iteration of that vision, with definition of Goals/Objectives that organize the broad range of existing and needed planetary aeolian studies.

Bulletin of the AAS↗

USGS2021

Planetary dunes tell of otherworldly winds

Dune fields are common on beaches and in deserts—think of the imposing sand hills and sinuous ripples of the Sahara in Africa or the Karakum in Central Asia, for example—as well as underwater on the beds of rivers, lakes, and oceans. The varied shapes, sizes, and orientations of both modern dunes and those preserved in the geologic record tell of the conditions under which they formed, particularly the strengths and patterns of winds and ocean currents. This information offers us valuable windows into environments and climates at different places and at different times in Earth’s history.

Eos, American Geophysical Union↗

USGS2017

Plateaus and sinuous ridges as the fingerprints of lava flow inflation in the Eastern Tharsis Plains of Mars

The Tharsis Montes rift aprons are composed of outpourings of lava from chaotic terrains to the northeast and southwest flank of each volcano. Sinuous and branching channel networks that are present on the rift aprons suggest the possibility of fluvial processes in their development, or erosion by rapidly emplaced lavas, but the style of lava flow emplacement throughout rift apron development is not clearly understood. To better characterize the style of lava emplacement and role of fluvial processes in rift apron development, we conducted morphological mapping of the Pavonis Mons southwest rift apron and the eastern Tharsis plains using images from the High Resolution Imaging Science Experiment (HiRISE), Mars Orbiter Camera (MOC), Context Camera (CTX), Thermal Emission Imaging System (THEMIS), and High Resolution Stereo Camera (HRSC) along with the Mars Orbiter Laser Altimeter (MOLA) Precision Experiment Data Records (PEDRs) and gridded data. Our approach was to: (1) search for depositional fans at the slope break between the rift apron and adjacent low slope plains; (2) determine if there is evidence that previously formed deposits might have been buried by plains units; (3) characterize the Tharsis plains morphologies east of Pavonis Mons; and (4) assess their relationship to the rift apron units. We have not identified topographically significant depositional fans, nor did we observe evidence to suggest that plains units have buried older rift apron units. Flow features associated with the rift apron are observed to continue across the slope break onto the plains. In this area, the plains are composed of a variety of small fissures and low shield vents around which broad channel-fed and tube-fed flows have been identified. We also find broad, flat-topped plateaus and sinuous ridges mixed among the channels, tubes and vents. Flat-topped plateaus and sinuous ridges are morphologies that are analogous to those observed on the coastal plain of Hawai‘i, where lava flows have advanced from the volcano's several degree flank onto the nearly zero degree coastal plain. When local volumetric flow rates are low, flow fronts tend to spread laterally and often thicken via endogenous growth, or inflation, of the sheet-like flow units. If flow advance is restricted by existing topography into narrow pathways, inflation can be focused into sinuous, elongate ridges. The presence of plateaus and ridges—emplaced from the rift zones, across the plains to the east of Pavonis Mons—and a lack of fan-like features, or evidence for their burial, are consistent with rift apron lavas crossing a slope break with low local volumetric flow rates that led to inflation of sheet-like and tube-fed lava flows.

Journal of Volcanology and Geothermal Research↗

USGS2015

The importance of dunes on a variety of planetary surfaces

Scientists observe aeolian bed forms, or dune-like structures, throughout the solar system in a range of locations, from bodies with only transient atmospheres, such as comets, to places with thick atmospheres, such as Venus and the Earth’s ocean floor. Determining the source of sand and the different dune formations that result are thus important to understanding solar system and planetary evolution.

Eos, Earth and Space Science News↗

USGS2013

Summary of the Third International Planetary Dunes Workshop: remote sensing and image analysis of planetary dunes

The Third International Planetary Dunes Workshop took place in Flagstaff, AZ, USA during June 12–15, 2012. This meeting brought together a diverse group of researchers to discuss recent advances in terrestrial and planetary research on aeolian bedforms. The workshop included two and a half days of oral and poster presentations, as well as one formal (and one informal) full-day field trip. Similar to its predecessors, the presented work provided new insight on the morphology, dynamics, composition, and origin of aeolian bedforms on Venus, Earth, Mars, and Titan, with some intriguing speculation about potential aeolian processes on Triton (a satellite of Neptune) and Pluto. Major advancements since the previous International Planetary Dunes Workshop include the introduction of several new data analysis and numerical tools and utilization of low-cost field instruments (most notably the time-lapse camera). Most presentations represented advancement towards research priorities identified in both of the prior two workshops, although some previously recommended research approaches were not discussed. In addition, this workshop provided a forum for participants to discuss the uncertain future of the Planetary Aeolian Laboratory; subsequent actions taken as a result of the decisions made during the workshop may lead to an expansion of funding opportunities to use the facilities, as well as other improvements. The interactions during this workshop contributed to the success of the Third International Planetary Dunes Workshop, further developing our understanding of aeolian processes on the aeolian worlds of the Solar System.

Aeolian Research↗

USGS1998

Geologic map of Pavonis Mons Volcano, Mars

The geologic map shows lava flows and fan-shaped deposits on Pavonis Mons, the central of three large shield volcanoes ( Arsia , Pavonis, and Ascr aeus Montes) that form the Tharsis Montes volcanic chain. The volcanoes lie along the crest of a regional northeast-trending rise that extends more than 3,000 km across the western equatorial region of Mars (fig. 1). The volcanic history of Pavonis Mons is similar to that of other volcanoes in the western equatorial region of Mars (Scott and others, 1981 a-c; Scott and Tanaka, 1981, 1986; Zimbelman and Edgett , 1992). Previous geologic mapping of this region (Scott and others, 1981a-c; Scott and Tanaka, 1981, 1986) shows six major lava flows that were extruded from the Tharsis volcanoes during the Early Hes perian to Late Amazonian Epochs; four of these lava flow members are present in the map area. On the northwest flank of Pavonis Mons, broad, lobate, fan-shaped deposits form a surficial cover similar to other fan-shaped deposits on the northwest flanks of Arsia , Arcaeus , and (to a lesser degree) Olympus Mons. Similar to those of Arsia Mons , the fan-shaped deposits of Pavonis Mons consists of several facies whose origins are attributed to glaciation, mass wasting, and pyroclastic volcanism origins.

IMAP↗

USGS1995

Geologic map of Arsia Mons Volcano, Mars

The geologic map shows the flanks and summit caldera of Arsia Mons, the southernmost of three large shield volcanoes ( Arsia , Pavonis, and Ascrae us Montes) that form the Tharsis Montes volcanic chain (fig. 1). The volcanoes lie along the cre st of a regional northeast-trending rise that extends more than 3,000 km along or near the planet-wide boundary that separates th e southern highlands from the northern lowlands. Previous geologic mapping of this region (Scott and others, 1981; Scott and Tanaka, 1986) shows six major lava flows that were extruded from the Tharsis volcanoes during the Early Hespe rian to Late Amazonian Epochs; the flows cover and area exceeding 7x10 6 km 2 around the volcanic centers. All of these flows – mapped as members of the Tharsis Montes Formation – are pre sent in the map area. Broad, fan-shaped surficial deposits that resemble landslides extend down the northwest sides of each volcano and of Olympus Mons, about 1,500 km northwest of Arsia Mons (fig. 1). The largest of these gently sloping, lobate deposits is on Arsia Mons, where ambiguous relations bet wee n one facies of the fan-shaped accumulations and underlying topographic features have provoked questions as to the origin of the deposits.

IMAP↗