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Online Seminars & Events

Week of January 17, 2022
GPS Division Seminar
4:00 pm
DIX Planetary Science Seminar
4:00 pm to 5:00 pm
Environmental Science and Engineering Seminar
4:00 pm to 5:00 pm
Geoclub Seminar Series
4:00 pm to 5:00 pm
Seismo Lab Seminar
4:00 pm

Division Seminar

Mondays from 4:00pm to 5:00pm
For more information, please contact: Leticia Calderon

"Reconstructing Depositional and Diagenetic Conditions from Bulk and Microscale Sedimentary Sulfur Isotope Records"
David Fike, Washington University
Abstract: Stable isotopic data (e.g., d13C or d34S) provide a framework for understanding biogeochemical cycling today and for reconstructing both global redox budgets and environmental change over Earth history. These reconstructions often rely on bulk sediment measurements and the assumption that the values measured at a given stratigraphic section provide information about global biogeochemistry. Here we demonstrate that d34S signatures that span a range of > 70‰ in marine sedimentary pyrites are controlled by variations in ambient depositional conditions, particularly sedimentation rate, organic carbon loading, and iron availability. Grain-specific isotope analysis by secondary ion mass spectrometry (SIMS) reveals that this isotopic sensitivity primarily results from how these depositional conditions modulate pyrite formation in the sediment column, rather than variations in the inherent isotopic fractionation by sulfur cycling metabolisms. Moreover, these results demonstrate that we can reconstruct original biological fractionation and resolve the relative order of pyrite formation within a sediment, extracting additional information about the evolving porewater environment. We show that local depositional variations in modern systems give rise to stratigraphically coherent d34S trends that are not representative of global S cycling. This requires that we revisit the interpretation of pyrite d34S records preserved in ancient strata.

"Geoscience Careers in the DOE National Laboratory System"
Marianne Walck – The James R. and Shirley A. Kliegel Lecture in Geological and Planetary Sciences, Idaho National Laboratory


The Department of Energy national laboratory system, comprised of 17 individual laboratories, is a premier research and development system for science and engineering in the US. The national laboratories employ more than 63,000 people, including >20,000 scientists and engineers in numerous disciplines. The national labs also host more than 3000 postdoctoral scientists. The majority of the national labs have significant R&D associated with earth and atmospheric sciences. Geoscientists have been part of the national laboratories for many decades, working on topics as diverse as climate change and earth system modeling and experimental programs, environmental remediation, earthquake/explosion discrimination, energy development, carbon sequestration, subsurface storage/disposal and critical minerals. National laboratories offer the opportunity for cutting-edge multidisciplinary collaboration in a team environment, as well as for more focused, small-group or individual R&D, and provide unique experimental and computational resources for staff. National laboratories also offer the opportunity for exploration of a variety of technical topics and leadership opportunities, either at one or multiple labs, during a career. The presentation will describe DOE and its laboratory system, highlight current geoscience topics and projects at several of the laboratories, and provide career path examples of some CIT GPS alumni who have spent all or part of their careers in the national laboratory system.

About the Speaker:

Marianne Walck is the Deputy Laboratory Director for Science and Technology and Chief Research Officer at Idaho National Laboratory (INL). Marianne earned her PhD in geophysics at Caltech in 1984; her thesis addressed upper mantle structure using data from the southern California seismic network. She began her career in the national laboratory system as a member of the technical staff at Sandia National Laboratories in Albuquerque, New Mexico. Research topics in the early part of her career included seismic tomography for upper crustal velocity variations, P-wave attenuation from underground nuclear explosions, crustal velocity anomalies at the US DOE Nevada Test Site, and use of early expert systems techniques to analyze seismic data. Additional topics included seismic hazard assessment for the proposed Yucca Mountain nuclear waste repository and geophysical characterization for deeply buried man-made structures.

Marianne became the manager of the Geophysics Department at Sandia in 1990. Her staff conducted R&D in geophysics related to energy, waste management, and defense missions, and she led the DOE Basic Energy Sciences/Geosciences portfolio for the laboratory. Her career at Sandia lasted 33 years and included a variety of leadership positions in different technical areas such as Senior Manager for Nuclear Energy Safety Technologies, and Center Director for the Nuclear Energy and Global Security Technologies Center, and for the Geoscience, Climate and Consequence Effects Center. Working with the Sandia's Research Leadership Team and the Chief Technology Officer, Marianne successfully initiated a new Research Foundation at Sandia, focused on Geosciences. In early 2015, Marianne was named as Vice President for Sandia's California Laboratory site (located in Livermore, CA) and the leader of SNL's broad-based Energy and Climate Program.

After retiring from Sandia in 2017, Marianne returned to New Mexico, however she flunked retirement and reentered the workforce in early 2019 at INL. In her current position, she provides strategic leadership, direction, and integration for research, science and technology for the entire laboratory. She leads INL's internal R&D program, directs INL's interactions with DOE's Office of Science, and oversees the lab's strategic interactions with universities.

Marianne serves on several advisory boards for universities, national laboratories and technical organizations, including the Texas A&M Energy Institute Advisory Board and the Women in Nuclear Executive Advisory Council. She was named one of the 2021 100 Most Influential Women in Energy by the National Diversity Council. She is vice chair of the State of Idaho Higher Education Research Council and is past chair of the National Laboratory Chief Research Officers. Marianne and her husband Eric Chael (PhD '83 Geoph), are the parents of two sons. She enjoys traveling, skiing, and playing the violin in the Idaho Falls (ID) Symphony.

" Studying the Carbon Cycle from Space: The Orbiting Carbon "
Annmarie Eldering, Jet propulsion Laboratory

Brief Bio:

Annmarie received her Ph.D. in Environmental Engineering Science from Caltech in 1994 with a focus on air pollution and its impacts on visibility in Los Angeles. She has been at JPL since 1999, adapting her knowledge of radiative transfer and light scattering to algorithm development for the satellite air pollution measurements of the Tropospheric Emission Spectrometer (TES). After a leadership stint in Section Management, she joined the OCO–2 project in 2010 in the role of Deputy Project Scientist. She now also is the Project Scientist for OCO-3, a follow-on payload.


The Orbiting Carbon Observatory-2 was NASA first mission focused on space-born measurements of carbon dioxide. It launched in 2014, and the follow-on, OCO-3, was installed on the international Space Station in 2019. These two missions are providing a new view of carbon dioxide around the earth with coverage and precision never seen before. This talk will review some key aspects of how we measure carbon dioxide from space, how it moves between Earth's atmosphere, plants, and ocean, and then show what we see from space with these two instruments. Results will include the seasonal cycles in carbon dioxide from space, the influence of plants, city emissions, and how phenomena like El Nino impact carbon dioxide.

" Terrestrial Planet Formation in the Solar System and the Early Instability Scenario "
Matt Clement, Carnegie Institute of Washington
Abstract: The current consensus evolutionary model for the outer solar system describes how the giant planets attained their modern orbits through an epoch of dynamical instability. In numerical simulations of this instability, the planets' orbital shapes evolve rapidly and chaotically; greatly disturbing the orbits of the young terrestrial planets. Undesirable outcomes such as over-excited terrestrial orbits, ejections and collisions can be avoided if the instability occurs before the inner planets are fully formed. Such a scenario also has the advantage of limiting the mass and formation time of Mars if it occurs within several million years after nebular gas dissipation. The dynamical effects of the instability cause many small embryos and planetesimals to scatter away from the forming Mars, and lead to significant mass depletion in the asteroid belt. I will present the results from recent numerical simulations of this scenario that demonstrate its ability to accurately reproduce the dynamical state of both the inner and outer solar system. Our model is one of several capable of consistently replicating many properties of Venus, Earth, Mars and the asteroid belt in numerical simulations. However, adequate analogs of Mercury are rarely produced in these simulations. I will present new results from a collection of companion investigations designed to identify viable formation models capable of consistently generating Mercury-like planets. In particular, I will introduce a model where proto-Earth and proto-Venus initially form in the vicinity of Mercury's modern orbit before migrating outward due to interactions with the primordial nebular gas. In successful simulations, Earth and Venus accrete excessive material from the Mercury-region as they migrate, thus allowing a small Mercury to form in dynamical isolation from the other terrestrial worlds. In addition to explaining the precise masses and orbits of all four inner planets, our model is capable of replicating differences between the inferred isotopic compositions of Earth and Mars

Terry Plank, Lamont Doherty Earth Observatory, Columbia University

Alyssa Rhoden, Southwest Research Institute, Boulder Colorado

Tanja Bosak, MIT

DIX Planetary Science Seminar

Tuesdays at 4:00 pm
For more information, please contact mcamarca@caltech.edu

"Effusive Volcanism on Earth and Mars"

Joana Voigt, Graduate Student, Lunar and Planetary Laboratory, University of Arizona

Lava surfaces are expressions of the volcanic and magmatic evolution of planetary bodies and thus provide a window into the emplacement as well as interior dynamics. The morphologies of volcanic terrains contain information about the thermo-physical parameters of the lava itself as well as the pre-eruption environment and thus can be used as a key to reveal emplacement conditions. This information is particularly important for interpreting eruption conditions for ancient lava flow-fields on Earth and other planetary bodies where only a post-emplacement geologic record is available.

A region of outstanding interest is Elysium Planitia on Mars, since it is home to the youngest volcanic terrains on Mars with ages of only a few million years and exhibits the largest fluvial outflow channel carved in the late Amazonian epoch. By using a combination of geomorphological (CTX and HiRISE) and geophysical data (SHARAD and MOLA), as well as chronological constrained we are reconstructing the fluvial, volcanic, and magmatic evolution in Elysium Planitia and show that lava morphologies can be a valuable tool to reveal the pre-existing topography and emplacement dynamics.

Further, analog sites here on Earth provide the means of testing our tools, approaches, and interpretations used in planetary sciences. The 2014–2015 Holuhraun lava flow-field in the Icelandic highlands provides a unique martian analog site to investigate the controlling factors of lava morphologies. I will show how we can obtain a comprehensive understanding of the relationship between eruption dynamics of lava flow-fields and the final lava morphologies of effusive eruptions by using a combination of remote sensing techniques and instruments, uncrewed aircraft systems (UAS), as well as field observations.

"Unveiling the early stages of planet formation"
Myriam Benisty
Abstract: Recent observing campaigns have revealed a great diversity in exoplanetary systems whose origin is yet to be understood. How and when planets form, and how they evolve and interact with their birth environment, the protoplanetary disks, are major open questions. Protoplanetary disks evolve and dissipate rapidly while planets are forming, implying a direct feedback between the processes of planet formation and disk evolution. These mechanisms leave clear imprints on the disk structure that can be directly observed.

In the past few years, high-resolution observations of protoplanetary disks obtained in the infrared scattered light and in the millimeter regime have led to exquisite images and shown that small scale structures are ubiquitous in protoplanetary disks, and could result from the dynamical interaction with embedded planets. I will present recent observational results on protoplanetary disks, that allow us to probe the disk structure and the dynamics of solids, and in particular, in the so far unique system that hosts two directly imaged protoplanets, PDS70.

Environmental Science and Engineering Seminar

Wednesdays from 4:00pm to 5:00pm
For more information, please contact: Bronagh Glaser

" The Effectiveness, Co-benefits, and Penalties of Adopting Solar Reflective Surfaces in Cities and Other Climate Change Mitigation/Adaptation Strategies"

Jianchen Zhang, California Air Resources Board
How can engineering methods and policies be utilized to mitigate and adapt to climate change? This seminar focuses on the effectiveness of adopting solar reflective "cool" surfaces in mitigating urban heat and their co-benefits and penalties on air quality and regional to global climate. Many cities are facing severe heat-related challenges (e.g., heat-related mortality) due to the combined effects of global rises in temperatures and the urban heat island effect. Using the Weather Research and Forecasting (WRF) and WRF-Chem models, we led the first study that systematically compared the climate and air quality effects of adopting energy-saving solar reflective "cool" walls and "cool" roofs in urban areas; our findings informed US Green Building Council's decision to give LEED building credits for using cool walls. We also estimated the global climate effects of "cool" roofs, which resolved discrepancies among previous studies.

This seminar will also briefly discuss other climate change mitigation/adaptation strategies and their air quality effects: (1) reducing the concentrations of light-absorbing black carbon aerosols in the atmosphere and (2) reducing GHG emissions through renewable energy adoption for the transportation and electricity sectors.

" Towards a truly global ocean science enterprise: Ocean Corps and the Coastal Ocean Environment Summer School in Ghana "
Brian Arbic, University of Michigan

Geoclub Seminar Series

Thursdays from 4:00pm to 5:00pm
For more information, please contact: Hannah Dion-Kirschner

"CaCO3 dissolution in carbonate-poor shelf sands increases with ocean acidification"

Abby Lunstrum- 5th year Graduate Student, USC


"Constraining CaCO3 export and dissolution with an ocean alkalinity model"

Hengdi Liang - 5th year Graduate Student, USC

"Controls on river avulsion style and stratigraphy in foreland basins"
Jeff Valenza, Postdoctoral Scholar, University of California, Santa Barbara


On decadal time-scales, most rivers remain relatively stable, changing through shifting bars and eroding cutbanks. On longer time-scales, rare but radical channel repositioning events are documented on rivers around the globe. This repositioning process, called avulsion, has caused some of the deadliest floods in human history, as river water and sediment are redirected from the parent channel onto the floodplain. However, while some avulsions create significant disturbance on the surrounding floodplain (termed progradation), most occur through rapid and discrete switching from the original channel to an adjacent channel with little to no floodplain disturbance (termed annexation). Despite the potential for significant impacts on floodplain environments and human infrastructure, a sparse record of these events has prevented avulsion models from predicting or explaining the different behaviors. To identify factors that lead to annexation or progradation, we turned to remotely sensed data of modern, avulsion-prone rivers in Andean, Himalayan, and New Guinean foreland basins. We focused on 63 rivers that hosted one or more avulsions and were captured in high-quality Landsat imagery. We first developed a remote sensing technique to map and quantify the area of floodplain disturbance due to avulsion activity. We found that the area of floodplain disturbance tends to increase with distance into the basin and with decreasing floodplain slope, and that single-thread, meandering river reaches hosted the largest-area avulsion events. Furthermore, we found that even in large avulsion events, avulsions switch between discrete channel switching and floodplain disturbance, sometimes multiple times. To determine whether these trends were observable in the sedimentary record, we turned to an ancient fluvial system in the Morrison Formation of Utah and Colorado. There, we found significant downstream trends in channel stacking patterns indicating annexation, as well as

Seismo Lab Seminar

Fridays from 4:00 pm to 5:00 pm
Location: Sharp Auditorium
For more information, please contact Seismo Seminar Committee.

" Earthquake Swarms and Slow Slip on an Upper Plate Sliver Fault in the Mexican Subduction Zone "
Michael Brudzinski, Miami University


The Mexican subduction zone is an ideal location for studying subduction processes due to the short trench-to-coast distances that bring broad portions of the seismogenic and transition zones of the plate interface inland. Using a seismicity catalog from a local network in Oaxaca, we identified 20 prominent swarms of M < 5 earthquakes from 2006 to 2012. Swarms outline what appears to be a steeply dipping structure in the overriding plate, indicative of an origin other than the plate interface. This steeply dipping structure corresponds to the northern boundary of the Xolapa terrane. In addition, we observed an interesting characteristic of slow slip events (SSEs) where they showed a shift from trenchward motion toward an along-strike direction at coastal GPS sites. A majority of the swarms were found to correspond in time to the along-strike shift. We propose that swarms and SSEs are occurring on a sliver fault that allows the oblique convergence to be partitioned into trench-perpendicular motion on the subduction interface and trench-parallel motion on the sliver fault. The resistivity structure surrounding the sliver fault suggests that SSEs and swarms of earthquakes occur due to high fluid content in the fault zone. We propose that the sliver fault provides a natural pathway for buoyant fluids attempting to migrate upward after being released from the downgoing plate. Thus, sliver faults could be responsible for the downdip end of the seismogenic zone by creating drier conditions on the subduction interface trenchward of the sliver fault, promoting fast-slip seismogenic rupture behavior.

Chloe Gustafson, UC San Diego

Zack Spica, University of Michigan

Fan-Chi Lin, University of Utah

Thesis Defense Seminars

For more information, please contact Julie Lee; julielee@caltech.edu