EPSS Colloquium - winter-2024
Calibrating Timescales and Measuring pCO2 to test the role of Columbia River Basalt volcanism in the Miocene Climate Optimum
Jan. 9, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Jennifer Kasbohm - Yale University
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Large igneous province volcanism in the Columbia River Basalt Group (CRBG) has been suggested to play a causal role in the elevated global temperatures and atmospheric carbon dioxide levels of the Miocene Climate Optimum (MCO). However, assessing the connection between volcanism and warming depends on developing accurate and precise chronologies for both events. Building on my previous work (Kasbohm & Schoene, 2018), I present fifteen new high-precision ages, using CA-ID-TIMS U-Pb on zircon and multi-collector 40Ar/39Ar on basaltic groundmass, to provide a detailed dual-chronometer timeline for CRBG eruptions (Kasbohm et al., 2023). Next, I have obtained the first high-precision U-Pb zircon ages targeting the duration of the MCO from volcanic ashes in ODP Site 1000 (Nicaragua Rise), which I use as an absolute age calibration for a new high-resolution bulk carbonate δ13C and δ18O record from this site. My new ages from Site 1000 pinpoint the interval of CRBG volcanism in the core, coincident with the interval of greatest sustained warmth in the MCO, yet the onset of warming begins hundreds of thousands of years prior to the onset of volcanism. Finally, I have obtained a new high-resolution (~15 ka) boron isotope record from IODP Site U1490 (Western Pacific Warm Pool) targeting the onset of the MCO through the end of the main phase CRBG volcanism (17.1-16 Ma) that shows well-resolved and relatively stable pH values across the MCO. Small changes in CO2 are coincident with CRBG volcanism but are likely insufficient to be the main driver of MCO warming. While my work reinforces the correlation in ages of the CRBG and MCO, these new records suggest a limited causal role for the CRBG in the MCO.
Alternating macroevolutionary regimes: do mass extinctions alter the rules of evolution?
Jan. 16, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Pedro Monarrez - EPSS, UCLA
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Mass extinctions have played a profound role in the evolutionary history of life. A central debate in paleobiology, however, centers on whether mass extinctions represent an intensification of background extinction dynamics versus mass extinctions representing a change in macroevolutionary regimes in which the rules that govern evolution temporarily change. In this talk, I will review some of the work around this debate and present recent work using fossil animal body size and geographic range that sheds light on how mass extinctions have been so important in the evolutionary history of marine life.
How Fast, How Deep, and How Much? — Understanding Groundwater Fluctuations with Seismic Sensing
Jan. 30, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Prof. Shujuan Mao - Dept. of Geophysics, Stanford University
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With climate change and population growth, two imminent challenges are facing humanity globally: water security and clean energy transition. Addressing these challenges requires a refined understanding of fluid systems hidden below the Earth’s surface (e.g., groundwater and geothermal reservoirs). However, our knowledge of near-surface fluids is still limited due to insufficient resolution or applicability of observational tools. In this seminar, I will present a novel, cost-effective approach to aquifer monitoring using seismometers. I will showcase the promise of this approach with a pilot application studying groundwater aquifers in Metropolitan Los Angeles (LA). Utilizing state-of-the-art seismic interferometry techniques, the seismological measurements recover the groundwater table near LA during 2000-2023 and match well with the surface deformations inferred from satellite sensing. The seismic images further allow, for the first time, the direct mapping of aquifer storage changes at deep depth over the past two decades. This pilot application bridges the gap between seismology and hydrology, and highlights the potential of leveraging seismometers worldwide to provide 4D (space-time) characterizations of aquifer systems. I will also demonstrate how this seismological approach can help to monitor geoenergy production and geohazards and quantitatively assess the anthropogenic impact on near-surface systems.
Current Events at Saturn: Insights from the Cassini Mission
Feb. 13, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Dr. Omakshi Agiwal - Center for Space Physics, Boston University
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Saturn, the sixth planet from the Sun in our solar system, is a rapidly rotating gas giant which was explored by the Cassini spacecraft for ~13 years. The observations from the Cassini mission have shown us that the space environment around Saturn is shaped externally by the solar wind, and internally by its atmosphere, its rings and its moons, where Saturn’s unique magnetic field serves as a primary channel for energy and momentum transport. This presentation will provide an overview of how Saturn's unique magnetic field geometry impacts energy circulation throughout the Saturnian system, including its effect on processes such as magnetic reconnection and structures such as the rings, and the planetary upper atmosphere. The presentation will focus on some of the key discoveries from the Cassini era, for example, the discovery of polar upper atmospheric vortices that modulate Saturn’s magnetosphere with a 10 hour periodicity; a zonal-wind driven field-aligned current system (the same process that drives the polar aurora at Earth and other planets in our solar system) at near-equatorial latitudes; and various channels for mass loss from the rings to Saturn’s atmosphere.
Porosity in Catchments and Critical Zones: New Frontiers in CZ Geophysics
Feb. 20, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Prof. W. Steven Holbrook - Department of Geosciences, Virginia Tech
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The critical zone (CZ) is Earth’s breathing skin, where fluxes of water, gases, matter, and nutrients transform bedrock into soil and support virtually all terrestrial life. Although the CZ extends from “treetop to bedrock,” the subsurface portions of the CZ are challenging to study, given their inaccessibility — requiring drilling, sampling, and geophysics. In this talk I will present new views of subsurface CZ structure, and its connections to surface vegetation and subsurface hydrology, using data from an NSF-supported Critical Zone Collaborative Network project. I’ll especially highlight rapid progress in CZ imaging due to new seismic nodal technologies and advanced imaging approaches.
What's Wrong with Deep Time Geology?
Feb. 27, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Prof. T. Mark Harrison - EPSS, UCLA
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One explanation for the broad range of views of what constitutes a philosophy of science is that there's no such thing. Geochemistry came of age ~60 years ago when it was popular to imagine that a definable “scientific method” separated what we do from other rational avenues of human endeavor. But geologists of that time lacked the intellectual infrastructure to prevent inspired speculations from ossifying into accepted wisdom. This is increasingly true as we look progressively further back in geologic time through a profoundly incomplete rock record strewn with preservation biases. Several features stand outin the dozen or so papers published since the beginning of the plate tectonic era that sought to portray Earth’s first half-billion year evolution, including the stature of the authors, their seeming confidence in opinions for which little evidence then existed or has since arisen, and that not one of them imagined a role for mobile lid tectonics in that eon. Over the past 20 years, evidence from lithic fragments as old as ~4.4 Ga have suggested that our planet supported Hadean oceans, life, continents, and plate boundary interactions. Thus it’s worth asking how essentially unconstrained speculations become cemented into community conventions and how this process could represent a 'scientific method'. Although the limitations imposed by the biased and fragmentary rock record might have been ameliorated by a greater emphasis on multiple working hypotheses, a community practice tailored to the paucity and type of evidence available is needed to prevent future lapses into Deep Time groupthink. Specifically, the importance of minimalism – giving weight to simpler models that are more easily refutable – suggests that the base level tectonic evolution model (the null to be disproved before more complex models are invoked) is continuous plate tectonics since global silicate differentiation. A community-derived, ethically sound approach would help balance the sometimes rival competitive and cooperative aspects of scientific research and provide a more uniform and satisfactory style of communication to the general public than, say, presently encouraged by weekly, international science publications.
Rheology of amphibole-bearing rocks across tectonic environments
March 5, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Prof. Caroline Seyler - Department of Earth Science, USC Dornsife College of Letters, Arts and Sciences
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Amphibole-bearing rocks are commonly found in the deeper sections of plate-boundary shear zones, including oceanic transforms, subduction plate interfaces, and strike-slip shear zones in the lower continental crust. The rheology of amphibole-bearing rocks is fundamental to the formation and maintenance of these shear zones, which has wide-reaching implications from subduction initiation to the earthquake cycle. Yet amphibole rheology remains under-constrained. In this talk, I will present three studies of amphibole deformation across PT-space and tectonic environments from natural shear zones and laboratory experiments. The composition of amphibole and its interactions with other phases influence and change its rheology across environments. Ultimately, amphibole is consistently an important and relatively weak mineral phase, especially in fluid-present shear zones.
Why We Collect
March 12, 2024
3:30 p.m. - 4:30 p.m.
3853 Slichter Hall
Presented By:
- Dr. Aaron Celestian - Natural History Museum, Los Angeles
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Mineral museums are pivotal in fostering multidisciplinary research endeavors within the scientific community. The mineral collection at the Natural History Museum of Los Angeles not only houses extensive collections of mineral specimens (~175,000), but also provides invaluable resources for researchers to study Earth's geological history, mineral composition/structure, and formation processes. Through access to curated collections, scientists can conduct detailed analyses using our advanced analytical capabilities, borrow minerals for destructive and non-destructive analyses, and unravel the intricate complexities of Earth's geology. Furthermore, the Mineral Sciences Department at NHMLA often collaborates with academic institutions and research organizations, facilitating interdisciplinary studies and knowledge exchange. By supporting research initiatives, mineral museums contribute significantly to the advancement of geological sciences, enriching our understanding of the natural world and its evolution over time. This presentation will cover some of the research being performed at NHMLA, and dive into our global collection from the bottom of the Pacific to the top of Mt. Everest.