Fall 2017 Colloquia

August 21: First day of classes - no colloquium

August 28: Claudia Johnson, Department of Earth and Atmospheric Sciences. Title: Evolutionary paleoecology: A model for looking at the past to interpret the future

September 4: Labor Day - no colloquium

September 11: Jim Brophy Department of Earth and Atmospheric Sciences. Title: Deciphering the origin of silicic magma…an aging petrologist›s swan song

September 18: David Wald, U.S. Geological Survey, National Earthquake Information Center, Golden, CO Title: Uncertainties and Challenges in Real-time Earthquake Shaking and Loss Estimation

Abstract: USGS has developed several near-real time earthquake information systems that provide rapid and automated alerting of shaking distribution, critical facility inspection priorities, and estimates of economic and human impacts following earthquakes. I’ll describe the research and development behind the components required to rapidly assess an earthquake’s impact: rapid source characterization, estimates of shaking distribution, losses estimates, and communicating uncertain loss estimates in an appropriate form for actionable decision-making among a variety of users.

Rapidly and automatically assessing the wide range of seismological, demographic, building inventory, and vulnerability information necessary to make such loss estimates entails a requisite balance of empirical and physics-based modeling strategies. In the course of explaining the end-to-end strategies and science/engineering employed by the USGS Prompt Assessment for Global Earthquake for Response (PAGER) system, we describe what pragmatic choices were made in balancing the uncertainties in and benefits provided by our empirical, semi-empirical, expert-opinion, and physical models.

Topics to be introduced that could be flagged for follow-up discussions include: spatial variability of ground shaking and implications for loss estimates, portfolio fragility functions and loss estimation (ShakeCast), financial instruments triggered by these systems (including cat bonds and contingency loans), earthquake scenarios for planning and portfolio analyses, and developing tools for landslide and liquefaction assessment in addition to shaking-based loss estimates.

September 25: Lixin Wang, IUPUI. Title: Ecohydrology in water-stressed environments - an isotope perspective

Abstract: Intrinsic water-limited ecosystems cover at least 40% of the global land surface and most other ecosystems will experience water stress (e.g., drought) at certain stage. In water-stressed ecosystems, patterns of water availability constrain the vegetation spatial and temporal dynamics, and vegetation has strong feedbacks to water cycle. This talk will discuss how to use stable isotopes as a powerful tracer to enhance our understanding of ecohydrological processes in water-stressed environments and the responses to a changing environment. Specifically, this talk will focus on two main questions, 1) how to partition evapotranspiration and what is the warming effect on evapotranspiration partitioning using newly developed laser-based isotope techniques; and 2) how to identify the origins of non-rainfall water (e.g., fog and dew) in extremely water-limited environments and how to differentiate fog and dew formations using novel isotope techniques.

October 2: Tom Bianchi, University of Florida. Title: Carbon Remineralization and Burial in the Coastal Margin: Linkages in the Anthropocene

Abstract: Continental margin systems collectively receive and store vast amounts of organic carbon (OC) derived from primary productivity both on land and in the ocean, thereby playing a central role in the global carbon cycle. The land-ocean interface is however extremely heterogeneous in terms of terrigenous inputs, marine primary productivity, sediment transport processes and, depositional conditions such as bottom water oxygen levels. Continental margins are also highly dynamic, with processes occurring over a broad range of spatial and temporal scales. The rates of organic carbon burial and oxidation are consequently variable over both space and time, hindering our ability to derive a global picture of OC cycling at the land-ocean interface. Here, I review the processes controlling the fate of organic matter in continental margin sediments with a special emphasis on “hot spots” of OC burial and oxidation. I will present a compilation of compositional data from a set of illustrative settings, including fjords, small mountainous river margins, large deltaic systems and upwelling areas. Bulk organic carbon stable isotope and radiocarbon compositions reveal the diversity and complexity characteristic of organic carbon buried in marginal seas. This primarily relates to the differences in marine and terrestrial inputs, the composition of the terrestrial component (e.g. vascular plant OC, soil, and petrogenic OC inputs), and processes modulating the fate of organic carbon within the marine environment (e.g., priming). This widely contrasting behavior illustrates that the reactivity of organic carbon is a product of its chemical composition and ecosystem properties. Interpreted in the context of bulk compositional data as well as that obtained on specific molecular markers (e.g., lignin-derived phenols), the possibility exists to tease apart complex mixtures of terrestrial and marine inputs, and to shed light on the role of the myriad depositional and post-depositional processes.

October 9: Jeff Oslund, Anadarko Petroleum, Retired. Title: Flourishing Thru Volatile Times. Learnings from an IU alum›s 35 year career in petroleum exploration

Abstract: There are over 30,000 geoscientists employed in the US, and roughly 20% of these are in oil and natural gas exploration and production. The stability of petroleum geoscience careers is directly linked to product prices, technical training (academic and on the job), and attitude of the geoscientist. For those fortunate enough (or savvy enough) to “be in the right place at the right time” and willing/able to learn quickly, the opportunities afforded by this career can be amazing! From the first discovery well on US soil to traveling the world to study unexplored basins and build alliances with foreign partners and governments, it’s been a great ride!

October 16: Jessica Conroy, University of Illinois. Title: Loess accumulation and hydroclimate variability in association with Lake Michigan Lobe fluctuations during the Last Glacial Maximum

Abstract: A new age model of Peoria Silt accumulation along the Illinois River Valley indicates loess accumulated episodically from ˜28,500 to 18,000-16,000 cal yr BP, as the Lake Michigan Lobe margin fluctuated within northeastern Illinois. We find that high rates of loess deposition were coincident with regional glacial advances during the local Last Glacial Maximum. Overall, Peoria Silt mainly accumulated when the Lake Michigan Lobe was at or near its southernmost extent. This finding stands in contrast to previous, limited constraints on the timing of Peoria Silt deposition, which suggested high rates of loess accumulation persisted through the deglaciation, even after the Lake Michigan Lobe had retreated out of northeastern Illinois. A weakly developed paleosol, the Jules Geosol, represents a period of significantly slower deposition, from 23,700 to 22,000 cal yr BP. Stable oxygen and carbon isotope values (δ18O and δ13C) of gastropod carbonate do not vary significantly across the pedostratigraphic boundary of the Jules Geosol, suggesting slower loess accumulation was a result of reduced glacial sediment supply rather than direct climatic factors. However, a decrease in δ18O values occurred between 26,000 and 24,000 cal yr BP, synchronous with the Lake Michigan Lobe’s southernmost advance. This δ18O decrease suggests a coupling of regional summer hydroclimate and ice lobe position during the late glacial period, and highlights the utility of loess paleoclimate records to gain insight into the interconnectivity of glacial, aeolian, and atmospheric processes.

October 23: GSA Annual Meeting - no colloquium.

October 30: Robina Shaheen, University of California San Diego. Title: Present and Past Atmosphere-Geosphere-Hydrosphere Interactions on Earth and Mars and Implications for Mars 2020 .

Abstract: Earth’s climate is influenced by complex interactions between atmosphere-hydrosphere-geosphere and biosphere with sun being the central energy source. The hydrosphere (covering more than 70% of Earth’s surface) and atmosphere are closely linked via exchange of energy, gases and aerosols, thus affecting global carbon, oxygen, and sulfur cycles; and collectively exert a major influence on climate. A major challenge in 21st century atmospheric chemistry is to understand the spatio-temporal evolution of aerosol and its impact on climate. Each tiny particle with a large surface area acts as a complex reactor, constantly producing new compounds by its interaction with trace gases and through photochemical transformations on aerosol surfaces. I use a combination of field work, laboratory measurements, and trace gas satellite data to understand global transport and transformation processes. Oxygen triple isotopes, sulfur quadruple isotopes and concomitant isotope anomalies are used to unravel the present and past history of the atmosphere and atmo-hydro-geosphere interactions that are geochemically preserved in ice cores and rocks. I will discuss how oxygen and sulfur isotope anomalies can be used to describe gas to new particle formation, the oxidation history of particles, photochemical transformations, troposphere-stratosphere mixing and the "intricate dance" between the atmosphere and hydrosphere during El-Niño Southern Oscillation (ENSO). A better understanding of ENSO as a recurring natural phenomenon with global teleconnections extending from Australia to California is critical due to its impact on agriculture (droughts), and societies (fires and/or heavy rainfall) and fisheries. For instance, the strongest ENSO of the 20th century in 1997-98 caused ~ $86 billion economic losses worldwide. The extreme sulfur isotope anomaly observed during the1997-98 ENSO event provided a new perspective on Earth’s paleo-atmosphere such as the Pre-Cambrian rise of oxygen and the origin of life ˜2.2 Ga ago. The second part of my talk will focus on the serendipitous discovery of an oxygen triple isotope anomaly in atmospheric carbonates in aerosols collected at the Scripps Pier, La Jolla. The oxygen isotope anomaly in atmospheric carbonates provided a different perspective on the paleo-atmospheric carbon and hydrological cycles on Mars. I will discuss briefly how oxygen triple isotope analysis of carbonates and sulfate minerals preserved in Martian meteorites ALH84001, once considered to carry the relics of life from Mars and "Black Beauty" (NWA7034) provided new insights on the atmosphere-hydrosphere-geosphere interactions and photochemical transformations.

November 6: Enrique Merino, Professor Emeritus, Department of Earth and Atmospheric Sciences. Title: Replacement, metasomatism dynamics, and the blind spot of geochemists. (Examples: brucite-for-periclase in marbles; dolomite-for-calcite in dolomitization)

AbstractFor decades, geochemists have taken for granted that mineral replacement – a phenomenon only detectable visually – happens by "dissolution-precipitation." Based on that unwitting error, and underestimating petrography, they have totally missed crucial insights into the dynamics of all kinds of metasomatism. By correctly understanding the nature and physics of replacement I’ll derive new dynamic insights for one or two cases.

November 13: No colloquium

November 20: Thanksgiving Break - no colloquium

November 27: No colloquium Title: TBA

December 4: No colloquium