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Fall 2018 Colloquia

August 20: Gary Pavlis, Earth and Atmospheric Sciences Title: Three-dimensional Structure of the Alaska System and the St. Elias Syntaxis

Abstract: My presentation is a review of current knowledge the three-dimensional structure of Alaska at lithospheric to crustal scale. I will first review the Cenozoic history of Alaska to clarify the fundamental role the Yakutat microplate has played in shaping Alaska tectonic over the past 20 million years. I use plate kinematics to argue that the southern tip of the Yakutat microplate can serve as an anchor to constrain the geometry of the eastern edge of subducting Yakutat slab. GPS data indicate the Yakutat microplate is currently moving as an independent block midway between two feasible end members. The end members are defined by two strike slip faults that define the southern (Transition Fault) and eastern (Fairweather Fault) boundaries of the Yakutat microplate. I then show components of a 3D model of Alaska developed for a paper presently in press in Geosphere. The model defines the geometry by three surfaces: (1) topography, (2) crust-mantle boundary, and (3) mantle lithosphere. The later is different from the former throughout much of the area because multiple lines of evidence indicate large parts of southeast Alaska crust do not move coherently with underlying mantle. Finally, I focus on the syntaxis formed by a tectonic corner in southeast Alaska near Mt. St. Elias.

Thermochronology results demonstrate uplift rates in the region east of St. Elias are comparable to the eastern and western syntaxes of the Himalya. In our Geosphere paper we argue the strong uplift is linked to a crustal scale structure we call the middlebuster structure because of its resemblance to a two sided plow with that name used in farming.

August 27: Larisa DeSantis, Vanderbilt University. Title: Clarifying Mammalian Responses to Climate Change and Megafaunal Extinctions during the Pleistocene

September 3: No Colloquium - Labor Day

September 10: Maria Mastalerz, Indiana University Geological and Water Survey. Title: Improving Characterization of Anthropogenic Methane Emissions in the United States

Abstract: Methane, the primary component of natural gas, is a potent anthropogenic greenhouse gas that is second only to carbon dioxide in its contribution to rising global average temperatures. Methane has a diverse range of anthropogenic sources in the United States, including petroleum and natural gas systems, livestock and manure management, landfills, and coal mines. Being able to accurately quantify methane emissions from specific sources is critical for evaluating climate change policy proposals aimed at limiting greenhouse gases, as well as for a variety of health, safety, and economic reasons. At the request of multiple U.S. federal agencies, the National Academies of Sciences, Engineering, and Medicine established a committee to examine approaches to measuring, monitoring, presenting, and developing inventories of anthropogenic emissions of methane to the atmosphere. This presentation will discuss the Committee’s report, which summarizes measurement approaches, evaluates opportunities for methodological and inventory development improvements, and informs future research agendas of various U.S. agencies. Recommendations include continuing and enhancing current atmospheric methane observations and advancing model and assimilation techniques used in top-down approaches; establishing and maintaining a fine-scale, spatially and temporally (gridded) inventory of U.S. emissions, that is testable using atmospheric observations and update it on a regular basis; promoting a sustainable process for incorporating the latest science into the U.S. Greenhouse Gas Inventory and regular review of inventory methodologies; and establishment and maintenance of a nationwide research effort to improve accuracy, reliability, and applicability of anthropogenic methane emission estimates at scales ranging from individual facilities to gridded regional/national estimates.

September 17: Brian Tucker, President, Geohazards International Title: Reducing Natural Disaster Risk in Poor Countries

Abstract: GeoHazards International, a California-based nonprofit organization, was founded in 1991 in response to the large and rapidly growing risk of natural hazards in poor countries. Our mission is to reduce death and suffering from earthquakes, tsunamis, and other natural hazards in the world’s most vulnerable, underserved communities, by working before disasters strike. Our approach emphasizes preparation, sustainability, local capacity and advocacy. Over the last quarter century, GeoHazards International has applied this approach successfully in scores of communities around the world. During this same period, other organizations have joined our efforts and, even, a new UN organization was created to reduce exposure to natural hazards.

Despite these diverse efforts, disaster losses are increasing in poor countries and the human and economic toll is projected to continue to rise. If the world’s poorest countries are to develop unimpeded by disasters – to the benefit of all countries – several difficult changes are necessary. Investments in disaster preparedness and mitigation must be increased. The task of reducing risk must be viewed not as just an engineering and scientific challenge but also as a sociological, political, and psychological one. Financial and intellectual resources of industrialized countries must be recommitted to help poor countries.

September 24: Arndt Schimmelmann, IU Earth and Atmospheric Sciences. Title: Natural seepage of shale gas into the atmosphere as a source of greenhouse gas

Abstract: Geological hydrocarbon gas seepage is a global source of atmospheric methane as a greenhouse gas. Natural gas seepage is generally related to faults and associated fracture intensification domains that provide conduits for natural gas from reservoir rocks to migrate upward and enter the atmosphere. We compare the case of intense gas seepage stemming directly from source rocks, mostly organic-rich fractured black shales in western New York State (NYS) versus areas with rare seepage in the more southern regions of the Appalachian Basin and the Midwest USA. In addition to thermogenic methane, western NYS shale gas seeps emit a hydrocarbon gas mixture with ethane and propane gas concentrations reaching up to 35 vol. %. Fractures in NYS developed, reactivated and maintained permeability for gas as a result of repeated Quaternary glaciation and post-glacial basin uplift. In contrast, the Appalachian regions farther south and the southern Midwest regions experienced less glacial loading and unloading than in NYS, resulting in less recent natural fracturing, as witnessed by the rarity of seepage on surface outcrops and in caves overlying gas-bearing shales and coals. Microbial methanotrophic communities along gas seepage routes, the vadose zone and in soil are likely acting as efficient natural scavengers of small fluxes of methane before methane can enter the atmosphere. Only strong upward fluxes of methane at macroseeps can overwhelm the methanotrophic capacity. The historical literature suggests that early western NYS drilling and production of oil and gas diminished shale gas pressure and resulted in declining gas seepage rates. Our survey documented 12 active western NYS natural gas seeps, whereas more than 32 seeps have been reported or documented since the 17th century. Preliminary tests showed that SCIAMACHY satellite data did not detect atmospheric methane anomalies over western NYS seeps.

October 1:Dr. Matthew Churchfield from National Renewable Energy Laboratory http://www.nrel.gov Title: TBA

October 8: Sarah Schanz, Earth and Atmospheric Sciences. Title: TBA

October 15: Suzana Camargo, Columbia University. Title: TBA

October 22: Quinn Lewis, Earth and Atmospheric Sciences Title: TBA

October 29:Dylan Ward, University of Cincinnati. Title: TBA

November 5: Annual GSA Meeting, Indianapolis

November 12:Scott Robeson, IU Department of Geography. Title: TBA

November 19:No Colloquium, Thanksgiving Break

November 26:David Boutt, Northeast Climate Adaptation Science Center, University of Massachusetts Amherst. Title: TBA

December 3: TBA

December 10:End of Semester