September 7, 2018
3:00pm in PLS 1130
Alan Brandon from University of Houston
Constraints on Crustal Contamination of Martian Shergottite Magmas

Abstract: For 3 decades, a debate over whether shergottite meteorites with incompatible trace element enriched compositions were the result of crustal contamination while their parent magmas migrated to the surface or instead represent a mantle source in Mars, has not been resolved.  There is now enough compositional data for shergottites to model the process of crustal contamination of possible parent magmas in order to resolve this debate.  This talk will present the results of these models with implications to the origins of shergottite magmas in Mars.

September 14, 2018
3:00pm in PLS 1130
Kei Shimizu from Carnegie DTM
Carbon contents in Earth's mantle domains constrained using silicate melt inclusions and geochemical modeling

Abstract: Estimates of carbon contents in mantle sources of mid-ocean ridge basalts (MORBs) and ocean island basalts (OIBs) can provide constraints on the origin of the geochemically heterogeneous mantle. Furthermore, carbon fluxes from MORB and OIB mantle sources to the atmosphere provide constraints for understanding Earth’s climate stability and habitability. However, carbon contents in these mantle sources are difficult to estimate since most MORBs and OIBs have lost significant portions of their CO2 through degassing. Silicate melt inclusions, which are small amount of quenched magma trapped in crystals, preserve the CO2 contents in MORB and OIB magmas at depths of melt inclusion entrapment prior to significant CO2 degassing. In this talk, I will discuss carbon contents for MORB mantle sources (Siqueiros and Garrett transform fault in the East Pacific Rise) and a component of an OIB mantle source (Borgarhraun in northern Iceland) estimated using data from silicate melt inclusions in combination with geochemical modeling of mantle melting, magma degassing and mixing. The preliminary results suggest that at least one component of the Iceland mantle source (~400 ppm CO2) may be significantly more carbon-rich compared to an EPR-type MORB mantle source (~100 ppm CO2).

September 21, 2018
3:00pm in PLS 1130
Dalia Kirschbaum from NASA Goddard
Finding the Slippery Slope: “Detecting” Landslides from Space

Abstract: Rainfall-triggered landslides occur in nearly every country around the world, causing billions of dollars of damages and cause thousands of fatalities each year. Understanding and modeling the dynamics of rainfall-triggered landslides is a challenging task due to rainfall variability and the complexity of approximating landslide failure mechanisms over broader scales. Satellite data provides a unique perspective to estimate where and when landslides may be occurring as well as to map areas when these events occur. However, the accuracy is highly dependent on the spatial scale and methods used. This presentation outlines several on-going efforts to better understand landslide activity at different spatial and temporal scales using different modeling, mapping and citizen science methods.

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October 5, 2018
3:00pm in PLS 1130
Jane Willenbring from Scripps Institution of Oceanography, UC San Diego
The Null Hypothesis: steady rates of erosion, weathering and sediment accumulation during Late Cenozoic mountain uplift and glaciation

Abstract: At the largest time and space scales, the pace of erosion and chemical weathering is determined by tectonic uplift rates. Deviations from this equilibrium condition arise from the transient response of landscape denudation to climatic and tectonic perturbations, and may be long lived. I posit that the constraint of mass balance, however, makes it unlikely that such disequilibrium could persist at the global scale over millions of years, as has been proposed for late Cenozoic erosion. In this talk, I will use the available data to discuss the possibility that erosion, weathering fluxes and shelf sediment accumulation have remained constant over the last ten (or more) million years. Two important implications are: (1) global climate change may not change global denudation rates, because the nature and sign of landscape responses are varied; and (2) tectonic and climatic perturbations are accommodated in the long term by changes in landscape form. This work undermines the hypothesis that increased weathering due to late Cenozoic mountain building or climate change was the primary agent for a decrease in global temperatures.

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October 19, 2018
3:00pm in PLS 1130
Gene Likens from Cary Institute of Ecosystem Studies
Lessons Learned from Long-Term Studies of a Forest Ecosystem

Abstract: This talk will discuss 50 years of intensive study of the Hubbard Brook ecosystem (air/land/water/biological interactions), where the regional impacts of acid rain on forest ecosystems were first discovered in North America.

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November 2, 2018
3:00pm in PLS 1130
Kristen Fauria from Woods Hole Oceanographic Institution
Submarine volcanic eruptions: why some rocks float and others sink

Abstract: The 2012 eruption of Havre submarine volcano was the largest submarine pyroclast-producing eruption in modern history. Most of the material from the eruption formed a > 1.2 km3 pumice raft that floated across the South Pacific for more than a year. Rafts of floating pumice spread volcanic material far from its source and are important for the dispersal of marine organisms. Here we explore how pumice get to the surface from deep submarine eruptions, why some – but not all – pumice stay afloat in rafts, and how high porosities and phase changes lead to complex behaviors. By understanding the clast-scale dynamics of pumice in water, we can better interpret deposits and understand the fate of volcanic material in the ocean.

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November 9, 2018
3:00pm in PLS 1130
Christine M Hartzell from Department of Aerospace Engineering, UMD
Granular Mechanics on Asteroids: The influence of non-gravitational forces

Abstract: While asteroids vary significantly in size, morphology and chemical composition, there is a consistent need to understand the behavior of granular materials in order to improve understanding of the evolution of these bodies. The behavior and interactions of grains drives the interior structure of small, "rubble pile" asteroids, and may strongly influence the surface morphology across the range of asteroid sizes. Due to the weak gravity and lack of an atmosphere on these bodies, non-gravitational forces can dominate the interactions of grains. This talk will discuss the physics and dynamics of electrostatic dust lofting and levitation on asteroids, as well as plans to look for signatures of these phenomena at Bennu. On-going experimental work to understand triboelectric charging of regolith as well as computational studies of magnetic forces on metallic grains will be discussed.

November 16, 2018
3:00pm in PLS 1130
Michelle Bensi from Department of Civil and Environmental Engineering, University of Maryland, College Park
Resilience and risk-informed decision-making for natural hazard events

Abstract: Natural hazard events impact communities in profound ways by damaging facilities, adversely impacting health and safety, harming economies, and causing significant disruption to the social and culture composition of communities. While it is not typically possible to prevent the occurrence of natural hazards events, it is possible to make individuals, communities, and organizations more resilient to these events. A key element of resilience involves the infrastructure facilities and systems that provide essential services on which individuals, communities, and organizations depend. A first steps towards improving the resilience of infrastructure involves understanding and quantifying the risks to which the infrastructure is exposed. By incorporating probabilistic risk insights into decision-making, stakeholders (e.g., policy-makers and infrastructure owners) can make better decisions regarding acceptable risk exposure and mitigating actions. The seminar will include an introduction to resilience and risk-informed decision-making, with particular emphasis on probabilistic hazard assessment. Examples from recent research activities will be discussed.

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February 22, 2019
3:00pm in PLS 1130

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