Richard Ash, Mike Evans, Vedran Lekić, Cecilia Sanders, and Nicholas Schmerr, University of Maryland
Faculty Lightning Talks
September 12, 2025 at 11:00 am (ESJ 0215)
Lightning-fast, 5-minute talks by 5 members of the Geology Faculty about their research.
Richard Ash — The UMD Plasma Lab and the Origin and Importance of Chondrites
Mike Evans — Common Era paleoclimate research emerging from a new database of databases
Ved Lekić — Topic TBD
Cecilia Sanders — The Geologic Record of Symbiosis and Community Resource Management (as told by A. Phosphorite)
Nick Schmerr — Planetary Geophysics: The Moon, Mars, and Beyond
Michael Kipp, Duke University
How precisely can we quantify oxygen levels in the ancient ocean?
September 19, 2025 at 11:00 am (ESJ 0215)
Reconstructing past changes in marine dissolved oxygen levels is critical for understanding Earth’s evolutionary history. It also allows us to use past events to guide our expectations for ocean chemistry under anthropogenic warming. In this talk, I will take a deep dive into the mechanics of what has rapidly become one of the most widely-used tools for estimating past ocean oxygen levels: the uranium isotopic composition of carbonate sediments. I will systematically review how this “paleo-redox proxy” works, moving from its calibration in the modern ocean to its quantitative underpinnings and finally to actual paleo-records from various archives. The talk will conclude with a preview of ongoing work to improve the rigor of statistical reconstructions from multi-proxy datasets.
Pupa Gilbert, University of Wisconsin, Madison
Biophysics of Biomineralization
September 26, 2025 at 11:00 am (ESJ 0215)
A cool human enamel evolution story, with fantastic images of enamel nanostructure, and how they changed dramatically with the introduction of meat 2 Ma and agriculture 12 Ka.
Matthew Jackson, University of California, Santa Barbara
A “Hotspot highway” that extends back into the Cretaceous Pacific… and into the Tonga Trench
October 10, 2025 at 11:00 am (ESJ 0215)
Samoa, Arago-Rurutu, and Rarotonga are three South Pacific Superswell hotspots that make up the “hotspot highway”, a suite of overlapping hotspot tracks in the Samoan and Cook-Austral region. Hotspot tracks emerging from the South Pacific Superswell—a region of unusually shallow bathymetry and high density of hotspots—can be traced back into the Cretaceous near the Mariana trench. We show that the Cretaceous portions of these hotspots are subducting into the Tonga trench, explaining the Mariana along-arc geochemical trends. Before subducting into the trench, two of the hotspots were overtopped by the Ontong-Java Plateau, which suppressed plume melting. Unfortunately, segments of all hotspot tracks remain unsampled and uncharacterized, particularly in the Cretaceous, leaving some uncertainty as to their long-term evolution. However, the 80-100 Ma sections of two of the hotspot highway hotspots, Arago-Rurutu and Samoa, allow us to redefine absolute plate motion models for the Cretaceous Pacific and show that the Louisville hotspot is linked to the eruption of the Ontong-Java Plateau.
Admin Husic, Virginia Tech
American Rivers are Transporting More Sediment in Less Time
October 17, 2025 at 11:00 am (ESJ 0215)
Rivers across the United States are increasingly event-driven, with both water and sediment transport often concentrated into short, intense periods of hydrologic activity. Using deep learning models trained on hydrometric, meteorological, and land-use data, we reconstructed multi-decadal records of event water fractions and suspended sediment dynamics at hundreds of sites nationwide. Results show that streamflow is increasingly dominated by ‘new’ water, with 34% of sites exhibiting significant increases in event water fraction, largely linked to deforestation, urbanization, and intensifying precipitation. Similarly, 33% of sites exhibited significant increases in sediment flux and the window of that transport has grown narrower – at most sites, half of the annual sediment load occurs in less than 2% of the time. Together, these findings reveal that U.S. rivers are exporting more sediment in increasingly compressed windows, reflecting the coupled impacts of climate change and human land use on watershed processes.
Austin Green, Virginia Tech
A Tale of Two Lithospheres: The Geodynamic Controls on the Habitability of Europa’s Subsurface Ocean
October 24, 2025 at 11:00 am (ESJ 0215)
Europa, the smallest of Jupiter’s four Galilean moons, harbors a 100-km deep ocean underneath its icy surface. Assessing the habitability (ability to support life) of this ocean is the overarching objective of NASA’s recently launched flagship mission Europa Clipper. Due to the ocean being entirely covered by ice, however, the hypothetical Europan biosphere cannot be supported by sunlight and by extension photosynthesis. Instead, chemotrophic life may be supported by the consistent delivery of nutrients into the ocean from both its overlying ice shell and underlying rocky/metallic mantle and core. These nutrients reside on Europa’s surface (oxidants) and within its mantle (reductants) and must be geodynamically conveyed through both icy and rocky lithospheres to the ocean by some means. In this talk, I will present my recent work on these geodynamic controls on ocean habitability in both the icy and the rocky layers of Europa’s interior. Salt infiltration may encourage weakening and densification of the surface ice lithosphere, causing it to collapse to the base of the shell, bringing these nutrients with it. The presence of volcanism on Europa’s seafloor will produce hydrothermal reductants to feed hydrothermal vent communities. Can the surface ice lithosphere overcome its rigidity and sink to the ocean? Can magma generated in Europa’s deep interior break through its rocky lithosphere to erupt on the seafloor?
David Williams, Arizona State University
Jupiter’s Volcanic Moon Io: Results from the Juno Mission and a Look toward Future Missions
October 31, 2025 at 11:00 am (ESJ 0215)
Jupiter’s moon Io is the most volcanically active object in the Solar System, where over 400 vents erupt effusive flows or explosive plumes rich in silicate, sulfur, or sulfur dioxide. Io’s geology is unique compared to other moons in the Solar System, and its tidally-induced activity is a model to investigate lava-rich exoplanets. While much was learned from the NASA Voyager flybys in 1979 and the NASA Galileo Jupiter orbiter from 1996-2001, and from additional spacecraft flybys and telescopic observations, new insights were provided by high-resolution observations obtained from the extended mission of NASA’s Juno Jupiter polar orbiter. In this talk we will review past results from earlier missions and take a look at results based on the new Juno data, as well as look ahead to possible future mission concepts such as the Io Volcano Observer and the Prometheus Io plume sample return.
TBD
November 14, 2025 at 11:00 am (ESJ 0215)
TBD
January 23, 2026 at 11:00 am (ESJ 0215)
TBD
January 30, 2026 at 11:00 am (ESJ 0215)
Vasilije Dobrosavljevic, Carnegie Science Earth & Planets Laboratory (EPL)
March 27, 2026 at 11:00 am (ESJ 0215)
Barbara Romanowicz - Helz Lecturer, University of California, Berkeley
April 3, 2026 at 11:00 am (ESJ 0215)
Cole Nypaver, Smithsonian Institution Center for Earth and Planetary Studies, National Air and Space Museum
April 10, 2026 at 11:00 am (ESJ 0215)
TBD
April 17, 2026 at 11:00 am (ESJ 0215)
The coordinator for the Colloquium Series is Dr. Cecilia Sanders.