September 13, 2019
3:00pm in PLS 1130
Dr. Belinda Huang from Senior Advisor for Diversity and Inclusion in the Office of the Dean
Inclusivity, Diversity, and Equity Awareness (IDEA) Workshop

Abstract: Dr. Belinda Huang, Senior Advisor for Diversity and Inclusion in the Office of the Dean, has graciously offered to customize an interactive workshop on Inclusivity Excellence as our first Geology Colloquium of the semester. This tutorial will serve to educate on equitable practices, and help develop skills that will foster an inclusive climate in our own department. Dr. Huang and her team have also offered to provide refreshments for this event, so they have asked for a head count.

Webpage: https://www.geol.umd.edu/idea/

September 20, 2019
3:00pm in PLS 1130
Laurent Montesi from University of Maryland
Strength of Plates and Plate Boundaries
October 18, 2019
3:00pm in PLS 1130
Michael Ryan from The Magma Physics Project in Hilo, Hawai’i.
House building, subdivision development and farming in (and below) the active rift zones of Kilauea and Mauna Loa volcanoes, island of Hawai’i: What could possibly go wrong?

Abstract: From May through August, 2018, Kilauea erupted from two sites with a pattern and vigor not seen in the past 200 years. Summit eruptions were characterized by repeated caldera collapse events that sent magma reservoir roof blocks into the molten reservoir below, triggering M 5.1 to 5.4 earthquakes and sending ash and ejecta skyward and surges of magma into east rift zone conduits. Some 38 km distant, voluminous lava eruptions within the lower east rift zone have devastated numerous communities, laying waste to houses, farms and coastal resorts. These distant and seemingly different eruptions are intimately connected and the talk will integrate their several interrelationships. Overlaid on Kilauea since Hawaiian statehood, is a settlement pattern that generates profound and growing volcanic risk. For Kilauea, the eruption impacts have been addressed by the USGS’s HVO, by the County of Hawaii Civil Defense, by the National Park Service, by FEMA and by the Red Cross. Both eruptions have impacted a large community of rattled or displaced citizens. In addition, Mauna Loa is currently slowly building towards eruption and it too contains rift zones that loom over recently settled areas, and contribute towards significant and now potentially more dangerous volcanic risk.

October 25, 2019
3:00pm in PLS 1130
Geoffrey Abers from Cornell University
Searching for the deep roots of arc volcanoes: results from iMUSH seismic imaging in the Washington Cascades

Abstract: Many arc volcanoes erupt mantle-sourced basalts and high-temperature lower-crustal magmas, yet seismic images of this deep plumbing are almost non-existent. Are deep partial-melt bodies too small for seismology to see, or are typical seismic arrays too limited to detect them? We address these questions with a 2014-16, 70-station broadband array around Mount St. Helens (MSH), termed iMUSH (imaging Magma Under St. Helens). iMUSH provides some of the highest resolution 3D images of arc crust and underlying upper mantle anywhere. Imaging deep structure requires teleseismic and ambient wavefield methods. Receiver functions image 35-40 km of upper-plate crust and a subducting plate 65-68 km directly beneath MSH. This leaves very little mantle to melt, yet basalts are present. As elsewhere in the Cascades, the upper-plate Moho vanishes in the forearc (west of MSH), an observation usually interpreted as serpentinized mantle. Ambient-noise tomography shows low wavespeeds here consistent with hydrated mantle, requiring temperatures low enough for serpentines to be stable, as does low forearc heat flow. Seismic body-wave attenuation also confirms large temperature contrasts between the forearc and back arc. However, much of the reduction in Moho strength is a consequence of upper-plate geology: very high wavespeeds are observed in the lower crust west of MSH, greatly reducing the Moho velocity contrast. We see little evidence for melt except far east of MSH and overall these observations show little sign of the deep magma plumbing system. In fact, they imply that the lower crust and uppermost mantle are too cold directly beneath the edifice to generate the observed melts. To reconcile these observations with the volcanism at MSH requires significant lateral melt transport within the crust. These pathways are not directly visible with seismic imaging techniques currently available, motivating the need for other approaches.

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November 1, 2019
3:00pm in PLS 1130
Noah Randolph-Flagg from NASA Ames
Shakedowns, creeps, and other triggering events: investigating the relationship between water and earthquakes in California and Taiwan

Abstract: Earthquakes can be triggered by changes in water pressure and can also cause dramatic changes in water levels in wells thousands of miles away. How do small changes in stress (equivalent to the weight of a cup of coffee) amplify to cause wells to explode or to cause other earthquakes? In the first half of the talk, we will examine changes in groundwater due to earthquakes and propose a quantitative model where Rayleigh waves pump water out of aquifers and into fractures and faults even deep in the crust. In the second half of the talk, we will examine how the flow of water into fault may explain both some triggered earthquakes and seasonal creep on faults.

November 8, 2019
3:00pm in PLS 1130
Kristina Walowski from Middlebury College
Tracking volatile recycling in a heterogeneous mantle: Insights from the boron isotope composition of ocean island basalts

Abstract: Boron isotopes are a valuable tracer of recycled material because they fractionate strongly at the surface of the Earth and during subduction, but are not perturbed during high-T mantle processes. Thus, we utilize the B concentration and isotope composition from end-member OIB to document how recycling contributes to mantle heterogeneity. We present the largest high-precision B isotope dataset from ocean island material (basaltic glasses and olivine-hosted melt inclusions measured by SIMS) to date, with data from 38 different samples derived from 9 different ocean island chains that represent the main end-member OIB compositions including: EMI (Pitcairn Islands); EMII (Ra Seamount; Tristan de Cunha Island; Sao Miguel, Azores); HIMU (St. Helena; La Palma, Canary Islands) and FOZO (Fogo, Cape Verde; La Reunion Island; Ascension Island). After careful screening for seawater contamination, we find that despite trace element and radiogenic isotope variability, OIB show little variation with respect to their B isotope compositions and B concentrations when compared with the range observed in mafic arc magmas, and generally overlap with B isotope compositions and concentrations measured in mid- ocean ridge basalts. The results suggest little B is recycled into the deeper mantle because it is effectively stripped from recycled lithologies during upper mantle processes (e.g., subduction dehydration) or diluted during melting in the uppermost mantle. In addition, the results highlight the decoupling of B isotopes and traditional radiogenic isotopes and provide a new perspective on mantle source heterogeneity and volatile recycling in the deep mantle.

November 15, 2019
3:00pm in PLS 1130
Heloise Lynn from Texaco, Amoco-BP, Lynn Incorporated
Azimuthal P-P seismic measurements: Past, present, and future

Abstract: Azimuthal (az’l) seismic analyses give rise to better imaged data and insights into the in-situ stress field and the aligned porosity (fractures) that flow fluids. Ignoring azimuthal seismic information, which in the past was quite easy to do, is now inexcusable because of vast improvements in: (a) platforms to view, map, and analyze az’l prestack or partial stack data; (b) acquisition (more data); and (c) processing algorithms. As affordable compute power continues to increase, the ability to view, analyze, and process 3D P-P data from 0 to 360° shall become the norm, especially in complex geology settings. Continual improvements in imaging will drive this advance. The world is filled with new and exciting opportunities. With each new technology advance, new production is discovered. In the 33 years since the first SEG session on anisotropy, we have made a good start, but the best is still to come.


The coordinator for the Colloquium Series is Dr. Mong-Han Huang. You can contact him at mhhuang@umd.edu.
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