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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: The Complexities of Wind Flow through Wind Power Plants

An image showing the complex turbulent flow in the
wake of an individual wind turbine.

Abstract: Wind-driven electrical generation is becoming increasingly popular because it is clean, cost effective, and sustainable. Wind is the fuel to the wind power plant, and the flow of wind through the plant is amazingly complex, spanning a huge range of scales from the regional-scale weather down to the thin boundary layers on each wind turbine’s blades. Gaining a better understanding of this complex flow enables the design of even more efficient, robust, and innovative wind plant technologies. Additionally, this knowledge can be used to help better understand topics such as how wind plants interact with surrounding crops, wildlife, communities, and the electrical grid. In this talk, I will give a broad overview of the National Renewable Energy Laboratory’s research on wind-plant aerodynamics using both numerical tools and experimental measurements. My goal is that the audience, technical and nontechnical, will leave the talk with a better understanding of the complexity of the wind flow through wind plants and an appreciation for the possibilities for further improving wind energy through improved understanding of its complex flow.

Bio: Matt Churchfield is a senior researcher at the National Renewable Energy Laboratory (NREL). He is part of NREL’s National Wind Technology Center south of Boulder, Colorado. He has recently moved to Bloomington, continuing to work for NREL remotely. His research focuses on wind plant aerodynamics. He is particularly interested in wind-turbine wake effects, mesoscale-microscale coupling, the effects of atmospheric stability on wind-plant behavior, turbulence modeling, and wind-plant control. Matt earned his B.S. in Mechanical Engineering from the University of Nevada, Reno and his M.S. and Ph.D. from Purdue University’s School of Aeronautics and Astronautics before joining NREL as a postdoc in 2009.

October 8: Sarah Schanz, Earth and Atmospheric Sciences. Title: River terraces as Quaternary history books

Abstract: River terraces, the abandoned remnants of past floodplains, contain a wealth of data about past fluvial, tectonic, and climatic environments. In particular, terraces underlain by planar, fluvially sculpted bedrock – called strath terraces – are useful markers of tectonic deformation and river incision. Strath terraces form through 1) lateral planation, when the flat terrace top and strath are carved and the valley bottom widens, and 2) vertical incision, in which the river erodes down to a new base level and abandons the terrace. The switch between these two processes is controlled by many factors, including climate change, human activity, volcanic eruptions, and earthquakes. By investigating when and how river terraces form, we can derive the geologic and environmental history of a region. Here, I’ll show a case study in which we used strath terraces to quantify the impact of land-use on mountain rivers. I’ll also highlight current work using the geometry of river terraces to assess different processes of valley formation.

October 15: Suzana Camargo, Columbia University. Title: Tropical cyclones in climate models: Subseasonal forecasts, climatology and new diagnostics

Abstract: In this talk, I’ll discuss the characteristics of tropical cyclones in climate models, which are used in projections of TC activity under anthropogenic climate change. Some characteristics of TC climatology improve with model resolution, but not all do, and the improvement is not uniform across models. Using a large number of climate models, the relationship of standard TC diagnostics with the mean climate state is analyzed. Models with the same resolution can have a very different TC climatology, even if their large-scale environments are very similar. In order to understand these differences, two new diagnostics were developed that can give insight on how to improve models’ TC climatology, as well as the reliability of their projections.

In the second part of this talk the ability of the current generation of models in forecasting tropical cyclones (TCs) – hurricanes, typhoons – weeks in advance will be discussed. There is predictability in this time scales due to the well-known modulation of TC activity by the Madden-Julian Oscillation (MJO), with a higher level of TC activity when the MJO is in its active phase in a region. As the models’ skill in forecasting the MJO has improved in the last few years, the possibility of forecasting TC formation weeks in advance can be examined. The questions we will discuss are: How well do models simulate the MJO-TC relationship? Do models have skill in forecasting the probability of TC formation weeks in advance? Is the model skill dependent on the amplitude of the MJO?

October 22: Quinn Lewis, Post-Doctoral Fellow, Earth and Atmospheric Sciences Title: Compressing Δ x and Δ t: High Resolution Fluvial Geomorphology from Confluences to Cutoffs

Abstract: Fluvial processes and landforms are spatially and temporally dynamic, yet the scales at which data can be acquired in the field are often not detailed enough to fully characterize this complexity. The study of river confluences and cutoffs in the field has typically relied upon relatively sparse measurements in time and space, such as cross sections of flow velocity or channel morphology. This presentation explores the use of current tools and methods capable of compressing the spatial and temporal scales typically employed in fluvial geomorphology fieldwork. Case studies on the dynamics of merging flow at confluences in Illinois and meandering river chute cutoffs in Indiana are used to discuss the relationships among research questions, data resolution, data interpretation, and conclusions. Although the case studies demonstrate that compressing space and time leads to a more nuanced and detailed understanding of confluences and cutoffs, what might be neglected or misunderstood when space and time is reduced?

October 29:Dylan Ward, University of Cincinnati. Title: Of cliffs and cuestas: the complex response to stream incision through layered rocks, Colorado Plateau, USA

Abstract: The retreat of cliffs is an important mode of erosion in layered rocks of variable strength. For example, the iconic Colorado Plateau landscapes of Grand Canyon, Canyonlands, and Monument Valley owe their unique forms to this process. Interactions between stochastic rockfall and first-order channels draining a cliff complicate the cliff retreat response to incision by regional streams. The broad-scale response to tectonic uplift or base level fall in these landscapes therefore depends upon the local dynamics of cliff retreat. I will present work based on a 2D numerical model of cliff erosion, informed by natural experiment site in Utah. The site has a sandstone-over-shale stratigraphy with an ongoing transient response to base level fall. The model simulates fluvial and hillslope erosion, and rockfall from resistant units, including talus redistribution. Our results show that, in escarpments with multiple cliff-forming layers, cliff retreat response to regional base level change is complex. The base level signal reaches the upper cliffs when small transverse escarpments propagate along benches that form between the resistant layers. Specifically, these features form where the long-term incision rate exceeds the product of three terms: the caprock layer spacing; the ratio of the tangent and cosine of the structural dip; and a celerity factor describing the relationship between cliff retreat rate and its height. As a result: 1) the separation between the upper and lower cliffs expands and contracts through time; 2) incision waves reach the upper cliff after a significant lag and work to increase cliff height progressively along the cliff; 3) a single baselevel drop may become several separate waves of incision before it is felt by the upper cliff; and 4) rockfall debris then buffers the retreat response of the cliff itself to the arriving incision pulse?

November 5: Annual GSA Meeting, Indianapolis

November 12:Scott Robeson, IU Department of Geography. Title: Detecting Extreme Droughts in Time and Space

Abstract: The planet is warming at unprecedented rates. Does a warming climate necessarily lead to drier conditions and more drought? No, at least not universally. A warmer world also is a wetter world and precipitation is increasing at many locations. Because of these competing factors, several recent studies have shown little change in drought frequency and area, despite ongoing increases in potential evapotranspiration. Here, I evaluate the relative intensity and spatial distribution of extreme droughts: those that occur in the tails of the (drought-index) probability distribution. Two related questions motivate this work: (1) how extreme are recent droughts, such as the 2012-2015 California drought, in a long-term context and (2) what trends are occurring in the tails of the spatial drought distribution across the North American continent. To answer these questions, I use bias-correction techniques to match tree-ring records to instrumental data more closely than before and develop a new approach for estimating trends in spatial frequency distributions. In the case of the California drought, it far exceeded those from prior periods. Meanwhile, spatial distributions of drought show differing trends in the two tails. Both of these results suggest that we are experiencing a different phase of extreme droughts, even though drought frequency and area have not increased.

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