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Fall 2016 Colloquia

August 22: First day of classes, no colloquium.

August 29: Tae Hee Hwang, Indiana University Department of Geography. Title: Simulating vegetation controls on hurricane-induced shallow landslides with a distributed ecohydrological model

Abstract: The spatial distribution of shallow landslides in steep forested mountains is strongly controlled by above- and belowground biomass, including the distribution of root cohesion. While remote sensing of aboveground canopy properties is relatively advanced, estimating the spatial distribution of root cohesion at the forest landscape scale remains challenging. We utilize canopy height information estimated using LiDAR (Light Detecting And Ranging) technology as a tool to produce a spatially distributed root cohesion model for landslide hazard prediction. We characterize spatial patterns of total belowground biomass based on the empirically derived allometric relationship developed from soil pit measurements in the Coweeta Hydrologic Laboratory, North Carolina. The vertical distribution of roots and tensile strength were sampled at soil pits allowing us to directly relate canopy height to root cohesion and use this model within a distributed ecohydrological modeling framework, providing transient estimates of runoff, subsurface flow, soil moisture, and pore pressures. We tested our model in mountainous southern Appalachian catchments that experienced a number of landslides during the 2004 hurricane season. Slope stability estimates under the assumption of spatially uniform root cohesion significantly underpredicted both the total number of landslides and the number of “false positives”, unfailed areas of the landscape that were predicted to fail. When we incorporate spatially distributed root cohesion, the accuracy of the slope stability forecast improves dramatically. With the growing availability of LiDAR data that can be used to infer belowground information, these methods may provide a wider utility for improving landslide hazard prediction and forecasting.

September 5: Labor Day, no colloquium.

September 12: Shemin Ge, University of Colorado at Boulder. Title: Fluid Injection Induced Earthquakes

Abstract: Since the 1960s, pore fluid pressure was identified as the primary culprit for inducing earthquakes that occurred near deep fluid-injection wells and surface reservoirs. As these human activities continue to grow in past decades, induced seismicity has proliferated, notably in otherwise tectonically quiescent locales such as the central eastern US. Yet, many injection sites do not experience induced seismicity. Increased seismicity in some regions but not everywhere raises the question of what fundamental hydrogeological processes and operational parameters make some sites more prone to induced seismicity. This study offers an overview and physical insights on fluid induced seismicity from a hydrogeologic perspective. A case study in central Oklahoma is used to illustrate how pore fluid pressure could have played a role in observed seismicity. Results suggest that high rates of hydrologic loading, i.e., fluid injection rates, emerge as an important player in contributing to induced seismicity. Within the first few years of these hydrologic loadings is typically a critical period when increased seismicity is most likely. Assuming the Earth’s crust is critically stressed, relatively small pore pressure perturbation, i.e., on the order of 0.05 MPa, could be sufficient to trigger or speed up earthquake occurrence. While pre-existing faults could dictate earthquake locations, the spatial extent of pore pressure influence could reach tens of kilometres from fluid injection or reservoir impoundment sites. Continued research to further probe connections between pore pressure propagation and fault spatial distribution in deep geologic formations will advance current understanding on hydrogeologic and seismologic processes, which will ultimately help provide guidance for best practices in the quest for energy resources in coming decades.

September 19: Michael Hamburger, Department of Geological Sciences, IU Title: Geology, Theology, and Foreign Policy: Representing science at the US State Department

Abstract: In this colloquium, Michael Hamburger will report on his year in Washington, DC as a Jefferson Science Fellow. The Jefferson Fellowship is a program run by the National Academy of Sciences that brings scientists and engineers to work with the State Department and the US Agency for International Development on issues of science and foreign policy. In his year at the State Department, Professor Hamburger had an unusual posting as a senior advisor in the Department’s Office of Religion and Global Affairs, an office newly created by Secretary John Kerry to advise on global issues at the intersection of religion and US foreign policy. Hamburger was the sole scientist in that office. His work involved engaging religious communities on issues of global environmental policy, climate change, and disaster risk reduction. As part of his fellowship, he spent six weeks as an Embassy Science Fellow in Kathmandu, Nepal, working on post-earthquake reconstruction and hazard assessment. The colloquium will review the emerging role of science in high-level international policy issues, and the intriguing intersection between science, religion, and foreign policy.

September 26: GSA Annual Meeting, no colloquium.

October 3: This colloquium is cancelled Jim Boles, University of California, Santa Barbara. Title: TBA

October 10: Kimberly Rogers, University of Colorado Title: Doomed to Drown? Sediment Dynamics and the Threat of Sea Level Rise in the Bengal Delta

Abstract: The Bengal Delta in Bangladesh is regularly described as a "delta in peril" of catastrophic coastal flooding. In order to maintain a positive surface elevation, sediment aggradation on the delta must be equal to or greater than that of local sea level rise. Paradoxically, widespread armoring of the delta by coastal embankments meant to protect crops from tidal flooding has limited fluvial floodplain deposition, leading to rapid compaction and lowered land surface levels. This renders the floodplains of the delta susceptible to devastating flooding by sea level rise and storm surges capable of breaching the poorly maintained embankments. The government of Bangladesh is currently proposing a one-size-fits-all approach to renovating the embankments under the assumption that sediment dynamics in the delta are everywhere the same. However, natural physical processes are spatially variable across the delta front and therefore the impact of dikes on sediment dispersal and morphology should reflect these variations. Direct sedimentation measurements and short-lived radionuclides are used to show that transport processes and sedimentation rates are highly variable across the delta front, and in some places aggradation is more than double the rate of local sea level rise. Dominant modes of transport are reflected in the patterns of sediment routing and flux across the lower deltaplain, though embankments are major controls on sediment dynamics throughout the coastal delta. This challenges the assumption that the Bengal Delta is doomed to drown; rather it signifies that effective preparation for 21st century climate change will require consideration of spatially variable local dynamics.

October 17: Amos Winter, Indiana State University. Title: Persistent Mesoamerican monsoon regime initiated by deglaciation in the early Holocene

Abstract: Understanding the global monsoonal system is of great societal importance because monsoons supply much of the world’s population with precipitation. Most paleo-monsoon records from various tropical regions of the Earth reveal a dominant relation with insolation changes during the Holocene, where the linking mechanism typically ascribes a major role to precessionally-driven southward displacement of the Inter-Tropical Convergence Zone (ITCZ). Fewer monsoonal records feature characteristics that are incompatible with insolation driven changes and show relatively stable conditions, especially after 7000 yr BP. Intertwining of different, often competing response mechanisms to forcings acting at different timescales and changed boundary conditions can generate high spatial-temporal complexity of monsoonal systems and complicate the dynamical understanding and attribution of reconstructed changes.

Here we use a continuous, absolutely dated record from a Guatemalan speleothem (RM-MA). The Yucatan peninsula located on the narrow stretch of land separating the tropical Atlantic and Pacific Oceans is at the northern margin of the ITCZ influence region and thus results in strong forcing on the respective ITCZ segments via inter-basin SST gradients. The region is also subject to phasing of dominant modes of Northern Hemisphere large-scale atmospheric variability, namely the North Atlantic Oscillation and the Pacific North American pattern.

Owing to the topographic setting, there is heightened competition from the different controls on MesoAmerican paleomonsoon variability, including orbitally-forced insolation changes, large-scale atmospheric variability and sea-surface temperatures (SSTs). Furthermore, stalagmite records from MesoAmerica covering the past few centuries indicate strong sensitivity to external radiative forcing resulting in prominent multidecadal hydroclimate variability in the region. However, how much the reconstructed changes are representative of the broader MesoAmerican monsoon variability during the Holocene remains unknown.

The record displays an abrupt transition of Mesoamerican hydroclimate variability from a dry to a wet, relatively stable regime around 9000 yr BP. We demonstrate that the transition is linked to a northward displacement of the ITCZ over Mesoamerica, which was predominantly forced by the dynamical changes induced by the melting of the Laurentide ice sheet over North America. Once the latitudinal threshold in the northward ITCZ shift was reached a stable monsoon regime characterized Mesoamerican hydroclimate evolution throughout the Holocene, and a continuously active MesoAmerican monsoon was in place throughout the last 9.000 kyr BP. Stationary regional SSTs provided stable boundary forcing of local convective activity, with a negligible impact from orbitally driven insolation changes. Our record shows consistent multicentennial and millennial scale variability with a Venezuelan record, once cleaned from insolation-driven changes, indicating that both capture the same character of regional hydroclimate variability at these timescales, hence substantiating the robustness of the proxy information.

October 24: Daniel Horton, Northwestern University. Title: Impacts of Changing Atmospheric Circulation

Abstract: According to the World Health Organization, approximately 3-million premature deaths were attributable to outdoor air pollution in 2012, with 88% of those premature deaths occurring in low- and middle-income countries. Hazardous air quality occurs when atmospheric conditions allow natural and anthropogenic pollutants to accumulate and persist in the near-surface environment. Climate change-driven alteration of the hydrological cycle and atmospheric circulation are expected to modify the meteorological conditions that help to regulate pollutant accumulation and dispersal, though the magnitude, direction, geographic footprint, and public health impact of these changes remains poorly resolved. To assess the influence of enhanced radiative forcing on the occurrence and persistence of atmospheric conditions conducive to poor air quality, this talk will explore recent changes in observed large-scale atmospheric circulation patterns, as well as future changes projected by an ensemble of state-of-the-science climate model simulations. Daniel Horton CV

October 31: Leah Morgan, USGS Title: VPrecision and accuracy in 40Ar/39Ar geochronology and its application to the Middle- to Late-Acheulean at Hugub, Ethiopia.

November 7: Whitney Behr, University of Texas. Title: Geologic heterogeneity and transient rheology of the deep subduction interface

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Abstract: The viscosity of the deep subduction interface is fundamental to both large-scale and regional-scale plate dynamics, affecting plate velocities, styles and rates of exhumation of subducted material, and depths and style of seismicity. In this talk I will demonstrate how observations from the rock record can tell us fundamental information about the mechanical behavior of the deep roots of subduction megathrusts. I will focus on a spectacularly exposed exhumed analog of a warm subduction zone located on Syros Island in the Cyclades in Greece, which preserves blueschist- and eclogite-facies deformation fabrics within a wide range of protolith rock types (metabasalts, marbles, metavolcanics and metapelites). I will use these rocks to address two primary questions:

  • 1) What controls the long-term viscosity of the deep subduction interface?
  • 2) What processes may contribute to episodic tremor and slow slip (ETS) along the deep subduction interface?

I will make the case firstly that the viscosity of the plate interface is highly sensitive to subducted protolith rock type, and that switches from metamafic- to quartz-dominated protoliths with progressive subduction can result in plate velocity changes of up to 6 cm/yr and can substantially affect the exhumational style within the subduction channel. I will make the case secondly that smaller-scale heterogeneities within individual subducted protoliths may represent the rock record of ETS events similar to those observed along the deep interface in modern subduction zones (e.g. Cascadia). These heterogeneities range in scale from mm to 400+ meters in diameter and include fractured and veined eclogitic lenses embedded in a viscously deformed blueschist matrix (representing a single oceanic protolith), as well as meta-mafic pods lodged within viscously deformed quartz-rich, marble-rich or pelitic units (representing multiple protoliths that are tectonically mixed).

Gary Motz

November 9 Peebles Memorial Lectures in Information Technology: Gary Motz, IU Paleontology Collections Manager. Project Coordinator for Digitization Activities, Center for Biological Research Collections Indiana University. Title: Pervasive Technology and cyberinfrastructure working for biodiversity informatics and collection-based research . 9:30-11:30 a.m. Herman B. Wells Library Scholars’ Commons, Hazelbaker Lecture Hall Room E159.

Abstract: Indiana University’s research community has a wealth of resources for understanding the history of life on our planet that take advantage of tremendous human capital, collections of physical objects, and remarkable technological advances. When these assets work together in synergy, the potential for innovation in ‘big-data’ driven questions about Earth’s flora and fauna (past and present) is dramatically enhanced. The Center for Biological Research Collections has partnered with UITS and the Indiana University Libraries to bring biodiversity collection research into the 21st century by building upon well over a century’s worth of specimen collections to enhance research, teaching, and broad engagement of our collections using augmented reality, high-performance and high-throughput computing, machine learning, citizen-science, and 3-D printing. This lecture will present the broad applicability of technological innovations and the use of IU cyberinfrastructure in dramatically enhancing the discoverability, accessibility, and research potential of a treasure trove of invaluable biodiversity collections.

BIO: Gary is a paleobiologist, but wears many different hats as the Digitization Coordinator for the Center for Biological Research Collections. His research focuses on the formation of biodiversity hotspots through deep time and the ecological significance of speciation and predator/prey dynamics in southeast Asia. He has traveled to museums and conducted field work all over the world in order to put together a big picture understanding of why biodiversity is critical to the health of the planet using digitized bio-collections and rich metadata contexts. Advancement of cyberinfrastructure and technological innovation are at the crux of what makes biodiversity research all the buzz in the biosciences community.

November 14: Simona Bordoni, California Institute of Technology. Title: Moist energetics of tropical circulations and their coupling to precipitation and radiative feedbacks

Abstract: Important advances have been made in the past decade in our theoretical understanding of controls on tropical precipitation. An emerging framework emphasizes the atmospheric energy balance as more fundamental than the traditional surface energetic perspective to understanding how the zonally-averaged Intertropical Convergence Zone (ITCZ) responds to radiative and surface energy flux perturbations. In this talk, I will discuss how this energetic perspective also provides strong constraints on monsoon circulations and associated convergence zones, which, while zonally localized, project strongly on the solstitial Hadley circulation. Numerical experiments with increasing complexity allow to shed light into the fundamental workings of monsoons and call for a reassessment of their driving mechanisms.

November 21: Thanksgiving Break, no colloquium

November 28: Tom Bianchi, University of Florida. Title: The Role of Terrestrially-Derived Organic Carbon in the Coastal Ocean: A Changing Paradigm

Abstract: Although inland waters comprise a small fraction of Earth’s surface, they play a critical role in the global C cycle. Global estimates of riverine flux of dissolved organic carbon (DOC) to the oceans range from about 250 to 360 Tg y-1. Interestingly, only a small fraction of the roughly 2900 Tg C yr-1 transported through inland waters globally ever reaches the ocean. Recent observations of immense CO2 evasion from streams and greater consumption of terrestrially-derived DOC (TDOC) suggests that TDOC is more unstable in aquatic systems than previously thought. Here, I posit that our view of "recalcitrance" and "lability" in characterizing organic matter (particulate and dissolved) need to be revised more in the context of "stability" and "instability" under different environmental conditions. For example, the residence time of litter and soil transport to the ocean vary considerably depending upon margin type (e.g., active versus passive), which strongly impacts the chemical character of the TDOC and TPOC reaching the coast. I will also provide a general background on the evolution of lignin in vascular plants and its role in key historical changes in global carbon preservation. Finally, I will discuss some new ideas about the role of priming in aquatic ecosystems, something that has largely been ignored to date. In particular, I will present results from simple lab-based experiments and new field results from the Amazon River, which demonstrate evidence for priming of TDOC.

December 5: Kyle Straub, Tulane University. Title: Lost in translation: Defining thresholds for the storage of environmental signals in stratigraphy

Abstract: Alluvial basins provide important records of climate and tectonic changes on Earth, as well as information about how land surfaces evolve under different boundary conditions. These deposits also contain important energy and water reserves and will serve as hosts for carbon capture and storage. Consequently our ability to reliably interpret and predict stratigraphic patterns is fundamentally important both scientifically and in its bearing on broader society. While stratigraphy is our best record of paleo Earth-surface dynamics, the record also contains significant gaps over a range of time and space scales. These gaps result from stasis on geomorphic surfaces and erosional events that remove previously deposited sediment. Building on earlier statistical studies, we examine the fidelity of the stratigraphic record in laboratory experiments where the topography of aggrading deltas was monitored at high temporal and spatial scales. In these experiments, we also quantify the depositional architecture that controls the 3D structure of the strata. This architecture is influenced by both stochastic (autogenic) and deterministic (allogenic) processes. Specifically, we investigate the temporal and spatial scales necessary for changes in forcing conditions (including sea level and/or sediment flux) to be stored in the stratigraphic record. This work helps improve efforts at recovering meaningful data about autogenic processes from stratigraphic datasets, isolating signals of changing boundary conditions in ancient basins, and modeling and predicting stratigraphy in alluvial basins.