September 2, 2020
12:00pm in Online
Doyeon Kim from Geology Department, University of Maryland College Park
Sequencing Seismograms: A Panoptic View of Scattering in the Core-Mantle Boundary Region

Abstract: Scattering of seismic waves can reveal subsurface structures, but usually in a piecemeal way focused on specific target areas. We used a manifold learning algorithm, the Sequencer, to simultaneously analyze thousands of seismograms of waves diffracting along the core-mantle boundary and obtain a panoptic view of scattering across the Pacific region. In nearly half of the diffracting waveforms, we detected seismic waves scattered by 3D structures near the core-mantle boundary. The prevalence of these scattered arrivals shows that the region hosts pervasive lateral heterogeneity. Our analysis revealed loud signals due to a plume root beneath Hawaii and a previously unrecognized ultralow-velocity zone beneath the Marquesas islands. These observations illustrate how approaches flexible enough to detect robust patterns with little-to-no user supervision can reveal unique insights into the deep Earth.

September 9, 2020
12:00pm in Online
Meng Guo from Yale University, Earth and Planetary Sciences
Argon constraints on the growth of continental crust and its composition

Abstract: Continental crust is a major geochemical reservoir whose evolution is tightly linked to the onset of plate tectonics, degassing history, and the budget of heat production within the Earth. Understanding the evolution of continental crust helps to unravel the workings of the Earth system as a whole. In this study, we present a coupled crust-mantle-atmosphere evolution model to explore the constraints of atmospheric argon on crustal evolution. Our model is the first to quantitatively investigate the effects of crustal recycling and reworking on degassing by computing the formation and surface age distributions of continental crust. The thermal history is coupled with the degassing history to ensure a self-consistent evolution of the Earth system. Parameter uncertainties are incorporated by Monte Carlo sampling, and successful results are selected by how closely they can reproduce the present-day and Archean atmospheric argon ratios, Proterozoic and Archean mantle potential temperatures, and the formation and surface age distributions of continental crust. We have collected an ensemble of 104 successful solutions, which suggests that the history of argon degassing favors rapid crustal growth during the early Earth. The highly incompatible nature of K requires a large quantity of early developed felsic crust (>80%), which challenges the popular notion of less than 10% of felsic crust at Archean. The presence of the early felsic crust provides important indications for the thermal regime, surface environment, and the extent of mantle processing during the early Earth.

Watch on YouTube

September 16, 2020
12:00pm in Online
Harrison Lisabeth from Lawrence Berkeley National Lab
Experimental insights into the seismic response of single fractures

Abstract: In order to interpret seismic data, rock physics models are required to make explicit links between observed quantities and physical properties.  Many of our fundamental rock physics models have been formulated with clastic sedimentary rocks in mind.  Today, as our scientific and technological questions expand to address more diverse lithologies, we need to revisit these older models.  I'll be presenting a broadband experimental study of the seismic velocity and attenuation of a single fracture in low porosity rock, which can shed some insight into the future directions of rock physics.

September 23, 2020
12:00pm in Online
Anna Gülcher from ETH Zürich
Evidence for widespread ongoing plume activity on Venus - clues from corona morphologies

Abstract: In the absence of global plate tectonics, mantle convection and plume-lithosphere interaction are thought to be the main drivers of surface deformation on Venus, resulting in a wealth of volcanoes, coronae, rifts, and mountains that cover the Venusian surface. It remains in question to what extent these surface tectonic and volcanic features reflect the current state of the planet’s interior.
In this seminar talk, Anna will showcase how the mysterious corona structures bear testimony to turbulent processes within Venus. Coronae are large ring-shapes structures with traces of volcanic and tectonic activity, and they feature a wide range of sizes and morphologies. While they are commonly thought to form by plume-lithosphere interactions, the exact processes underlying their development and the reasons for their diverse morphologies are uncertain.
Anna will present a systematic numerical study of plume-lithosphere interaction that links the morphological diversity of large coronae to the lithospheric structure and underlying processes. She will then provide guidance for identifying which coronae on Venus may be active today. Her assessment revealed that at least thirty-seven coronae feature structures that are consistent with ongoing plume activity, providing new evidence for widespread plume activity on the planet.

Watch on YouTube

September 30, 2020
12:00pm in Online
Jared Lee Wilmoth from Environmental Science and Technology Department, University of Maryland College Park
Soil Interfaces and Redox Oscillations at the Confluence of Environmental Chemistry, Microbiome Interactions and Climate Change

Abstract: This talk will focus on small-scale soil interfaces in redox-dynamic systems and their broader environmental impacts spanning different research projects. Dr. Jared Wilmoth has recently joined UMD as a new Assistant Professor in the Department of Environmental Science and Technology (ENST). Current investigations continue to examine the biogeochemistry of redox-dynamic interfaces in soils with an emphasis on the pursuit of using ultrahigh-resolution mass spectrometry (MS) and various geochemical and microbiome characterization techniques, including heavy metal isotope tracing with Mossbauer spectroscopy and meta-omics. His Ph.D. research at the University of Georgia focused on mineral-microbe interactions in redox-oscillating, forest soils of Puerto Rico. He then joined the Biological and Nanoscale Systems Group at Oak Ridge National Laboratory (ORNL) as a postdoc to study environmental microsites using microfluidics and high-performance computer simulations. He most recently completed a second postdoctoral project at Princeton University, with the Princeton Environmental Institute, to study how large methane emissions from wetlands are stimulated by soil redox transitions. His ongoing research seeks to understand the mechanistic linkages between soil organic and mineral chemistry, soil microbiome activity and global climate change using advanced analytical, omics and computational approaches.

Watch on YouTube

October 7, 2020
12:00pm in Online
Kathleen F. McKee from Carnegie Institution for Science
October 14, 2020
12:00pm in Online
Xiaoming Liu from The University of North Carolina at Chapel Hill
October 21, 2020
12:00pm in Online
George Guice from Smithsonian National Museum of Natural History
October 28, 2020
12:00pm in Online
Zachary A. Torrano from Carnegie Institution for Science
November 4, 2020
12:00pm in Online
David Johnston from Havard University
November 11, 2020
12:00pm in Online
Da Wang from Carnegie Institution for Science
November 18, 2020
12:00pm in Online
Richard Pepino from University of Pennsylvania
December 2, 2020
12:00pm in Online
Mojhgan Haghnegahdar from Geology Department, University of Maryland College Park
December 9, 2020
12:00pm in Online
Leah Dodson from Chemistry and biochemistry, University of Maryland College Park

The organizer for the lunchtime seminar is Grace Ni. You can contact her at zni@umd.edu.