Colloquium Schedule
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August 8, 2014
0:00am in CHEM 0215
Raquel Cepeda
Increasing Your Chances in Scoring an Oil and Gas Career
September 5, 2014
3:00pm in PLS 1130
Scott Burdick from NSF Postdoc at UMD
Probing Earth structure with teleseismic transmitted and reflected waves

Additional Information: Doctorate from Massachusetts Institute of Technology

September 19, 2014
3:00pm in PLS 1130
Robert Shedlock from MD-DE-DC Water Science Center
The U.S. Geological Survey in the 21st Century

Abstract: The U.S. Geological Survey is one of the oldest science bureaus in the federal government. For most of its history, it was organized around the disciplines of geology, hydrology, and topographic mapping. Significant changes in the Survey's disciplinary approach began in the 1990's when it implemented a major national water quality assessment program, added a new discipline in the form of the Biological Resources Division, and downsized its efforts in a number of classical areas of geologic investigation. Over the last 20 years USGS science programs have evolved to meet the needs of modern society for interdisciplinary earth and biological science. During this period the USGS reorganized into a number of interdisciplinary mission areas that cover climate and land use change, natural hazards, ecosystems, energy and minerals, environmental health, and water. The Mid-Atlantic Region is a fertile area for such interdisciplinary investigations, with important ecosystems in the Chesapeake and Delaware Bay regions and the Atlantic coastline. Regulators, resource managers, and planners in the Mid-Atlantic Region and throughout the Nation face many challenges caused by urbanization and population growth, land-use change, climate change, and sea-level rise. The USGS in the 21st Century is striving to generate reliable and objective environmental data and interdisciplinary investigations, which provide important scientific information for wise management of critical natural resources and important ecosystems and for intelligent planning for an uncertain future.

September 26, 2014
3:00pm in PLS 1130
Derrick Lampkin from UMD-AOSC
Shear Weakening Due to Drainage from Water-Filled Crevasses Along the Margins of Jakobshavn Isbræ

Abstract: Several marine-terminating outlet glaciers on the Greenland Ice Sheet have undergone dynamic thinning, acceleration, and retreat, largely driven by ocean-ice interactions at the glacier terminus. Commensurate with these changes, surface melt rates are also increasing, resulting in enhanced runoff and infiltration known to influence regional ice velocity and mass flux. In particular, Jakobshavn Isbræ has experienced some of the most dramatic changes relative to the other major outlet glaciers largely responsible for Greenland’s contribution to sea level rise. The fast-flowing trunk of Jakobshavn Isbræ is well within the ablation zone and is exposed to significant accumulated runoff and drainage from water-filled crevasses within the shear margins during the summer. The impact of drainage from these structures on Jakobshavn’s response to terminus instability is not well understood. There are seven major water-filled crevasse regions along the margins, with the largest demonstrating potential drainage volume on order of that from large supraglacial lakes. This effort explores the impact of meltwater injection on shear-margin weakening. Meltwater can reduce lateral drag through enhanced sliding due to distributed basal lubrication or reduced ice viscosity due to cryo-hyrologic warming. The finite-element Ice Sheet System Model (ISSM) was used to evaluate the impact of meltwater input into the shear margins on basal sliding and ice stiffness. Ratios of misfit between modeled and measured velocity for inversions of basal friction and ice viscosity show a shift from basal friction-to-viscosity dominated conditions from the winter to the summer, at locations where water-filled crevasses exist.

October 3, 2014
3:00pm in PLS 1130
Karen Prestegaard from UMD - Geology
Nonlinear effects of landuse and climate changes on stream channels and networks
October 24, 2014
3:00pm in PLS 1130
Eric Hellebrand from University of Hawaii - SOEST
Old refractory mantle peridotites at mid-ocean ridges

Abstract: Melt supply and crustal thickness can vary along slow-spreading ridges, as suggested by common exposures of serpentinized mantle peridotites on the ocean floor. An unexpected large fraction of these residues of partial melting contains evidence of ancient melt extraction that is unrelated to recent upwelling under the mid-ocean ridges, as well as chemical isolation on a billion year timescale. In this presentation, we will evaluate the geological and geochemical evidence for the widespread distribution of this refractory mantle component, and explore the role that this melting-suppressing material may have during crustal accretion processes at mid-ocean ridges.

Additional Information: Ocean Leadership Distinguished Lecture

October 31, 2014
3:00pm in PLS 1130
Lynn Carter from Goddard Space Flight Center
Revealing the stratigraphy of Martian volcanic deposits using radar

Abstract: Volcanism is one of the key processes that shaped Mars, and huge volcanic provinces such as Tharsis and Elysium produced flows and pyroclastic deposits over hundreds of millions to billions of years. Radar remote sensing has the capability to penetrate through rock and can reveal layers that are hundreds of meters below the surface. Recent ground penetrating radars (GPRs) on the Mars Express and Mars Reconnaissance Orbiter missions have revealed subsurface interfaces associated with lava flows and pyroclastics, and these data provide 3-D stratigraphic profiles, improved limits on unit volumes, and dielectric constant measurements (related to composition and density of the rocks). In the next decade, two rover-based (ExoMars and Mars2020) GPR instruments will provide higher-resolution subsurface profiling. In this talk I will discuss recent results regarding Tharsis and Amazonis Planitia volcanic deposits, show terrestrial analog GPR data, and discuss the future of radars at Mars.

November 7, 2014
3:00pm in PLS 1130
Julio Betancourt from USGS-Reston
Patterns, sources, and impacts of timing variations in seasonal transitions and trends across the coterminous U.S.

Abstract: Seasonal timing has myriad impacts on plants and animals, biospheric processes, and human systems, and is critical for formulating adaptive responses to both climate variability and change. In the coterminous U.S., the timing of seasonal transitions varies widely from year to year and is also changing directionally, yet the climatic drivers, patterns and consequences of these variations are poorly understood. I will synthesize growing knowledge about day-of-year (DOY) metrics that define the growing season and shape the water cycle in the U.S. All DOY metrics exhibit secular trends consistent with both natural variability and greenhouse warming, with abrupt advances spring for most regions clustered in the mid-1980’s and abrupt delays in fall clustered in the mid-1990. My presentation will reconcile different interpretations of large-scale drivers and discuss opportunities for long-range forecasting. I will conclude with two illustrations of the power of phenological monitoring at the continental scale. 

November 14, 2014
3:00pm in PLS 1130
Anna Kelbert from Oregon State University
Water Content and Processes in Complicated Subduction Settings as Inferred with Electromagnetic Methods

Abstract: Natural source electromagnetic induction methods in geophysics include
the local to regional scale magnetotelluric method, and the global to
semi-global electromagnetics. Introduced in 1950-s, these methods have
rapidly developed in the past 20 years to produce high resolution 3D
images of the electrical conductivity in the Earth¹s crust and upper
mantle. Electrical conductivity is most sensitive to the presence of
fluids and partial melts, and therefore provides a view that¹s highly
complementary to the seismic wave velocities. In this talk, I aim to
introduce the methods through a tour of one of their most useful deep
Earth applications: complicated subduction zone regions. I make use of
the versatility of our techniques to look at subduction zones, globally,
through the lens of electrical conductivity images; then zoom in to
regional scales. I give an overview of electromagnetic constraints on
the Philippine Sea plate subduction beneath China and Japan; the Nazca
and Cocos plate subduction in South and Central Americas; and finally
the younger subduction in North America, as imaged by EarthScope MT and
the earlier studies. Throughout my brief global tour I try to show that
electromagnetic inversion images the slabs and the associated volcanic
arcs in a geophysically consistent manner that complements the seismic
results, while adding independent and valuable information on the water
content and the associated subduction-related processes

Additional Information: EarthScope Speaker

December 5, 2014
3:00pm in PLS 1130
Zack Geballe from Carnegie - Geophysical Lab
A new laboratory technique to understand melting and freezing in planetary interiors

The coordinator for the Colloquium Series is Dr. Vedran Lekic. You can contact him at