Colloquia: Spring 2015
January 12: First day of term (no seminar)
January 19: MLK Day (no classes, no seminar)
January 26: Shuhai Xiao, Virginia Tech. Title: In the Wave of a Cryogenian glaciation and on the Eve of the Cambrian Explosion: Biological Evolution in the Ediacaran Period
Abstract: The evolutionary fuse of the Cambrian explosion is probably buried in the Ediacaran Period. In the past decade, significant progress has been made in Ediacaran paleobiology and geobiology to allow a better understanding of the interactions between environmental and biological evolution across the Ediacaran-Cambrian transition. With integrative paleobiological, stratigraphic, sedimentological and geochemical data, we can now establish a more robust chronostratigraphic framework and environmental context to better understand what happened on the eve of the Cambrian explosion. The discovery of new fossils allows us to have a more complete understanding of Ediacaran biodiversity, paleoecology, and evolutionary dynamics. The calibration and application of novel geochemical proxies gives us new tools to reconstruct paleoenvironmental conditions in the Ediacaran Period. In this talk, I will focus on possible animal fossils in the Ediacaran Period, and will discuss the potential roles of oxygenation and ecological feedbacks in early animal evolution.
February 2: Ariel Anbar, Arizona State University. Title: Education Through Exploration
Abstract: Education Through Exploration: Traditional introductory STEM courses often reinforce misconceptions because the large scale of many classes forces a structured, lecture-centric model of instruction that emphasizes delivery of facts rather than exploration, inquiry, and scientific reasoning. At ASU’s new Center for Education Through Exploration (ETX) we are developing immersive and engaging virtual environments (e.g., http://vft.asu.edu) and courseware (e.g., http://habworlds.org) that address this challenge. Our goal is to redefine learning as the rational exploration of the unknown, not just mastery of what is known, by developing engaging, adaptive, transdisciplinary digital learning experiences, deployed and supported by teaching and mentoring networks and other platforms, to educate-through-exploration effectively and at scale.
February 3: Ariel Anbar, Arizona State University. Brown-bag talk, 12:00 p.m., S201. Title: A Non-Traditional Application of Non-Traditional Isotopes: Can Calcium Isotopes Detect Cancer
Abstract: The ability to rapidly detect changes in bone mineral balance (BMB) would be of great value in the early diagnosis and evaluation of therapies for metabolic bone diseases such as osteoporosis and some cancers. However, measurements of BMB are hampered by difficulties with using biochemical markers to quantify the relative rates of bone resorption and formation and the need to wait months to years for altered BMB to produce changes in bone mineral density large enough to resolve by X-ray densitometry. We find that, in humans, the natural abundances of Ca isotopes in urine and blood change rapidly in response to changes in BMB. The physiological basis of these changes in understood. Therefore, Ca isotopic analysis provides a powerful way to monitor bone loss, potentially making it possible to diagnose metabolic bone disease and track the impact of treatments more effectively than is currently possible.
February 9: Kay Behrensmeyer, Smithsonian Institution. Title: Did Environmental Change Control Human Evolution in Africa
Abstract: In spite of many decades of energetic research and debate about this issue, it is not yet resolved. There is little doubt that environmental change must have played SOME role in shaping human evolution, as it has for most of Earth’s organisms over geological time. This talk is aimed at a balanced consideration of different biological and physical processes, including environmental change, and how they could have affected the evolution of our ancestors. The audience will be invited to think about these processes as possible "controls" in light of the many kinds of evidence that relate to human evolution in Africa, including associated faunas, paleoenvironments, stable isotopes, climate records in drill cores, and patterns contained in the hominid fossil and archeological record itself.
February 16: Frank Ettensohn, Department of Earth and Environmental Sciences, University of Kentucky, Lexington, KY 40506. Title: Large-Scale Tectonic and Structural Controls on Ordovician Black-Shale Distribution (Utica and Martinsburg) during the Taconian Orogeny, Northern Appalachian Basin, U.S.A.
Abstract: In the Appalachian Basin, black shales are major parts of most flexural, foreland-basin sequences and reflect the timing of major loading-related, foreland subsidence. Moreover, because of their distinctive character in the surface and subsurface, mapping their distribution can help track the progression of orogeny in space and time. In the U. S. Appalachian area, the distribution of Middle to Upper Ordovician black shales suggests that the Taconian Orogeny proceeded in a diachronous fashion from south to north along the eastern Laurentian margin, and that tectophases were mediated by convergence at successive continental promontories. In the Late Ordovician (late Sandbian–Hirnantian) Taconic tectophase, changes in the distribution of the Martinsburg and Utica black shales support a reversal of subduction polarity that effected the reactivation of basement structures and basin migration sufficient to yoke Appalachian foreland basin with adjacent intracratonic basins. Shale distribution suggests that early Chatfieldian (late Sandbian–early Katian), east-verging subduction early in the tectophase generated a cratonic extensional regime that resulted in a relatively narrow foreland basin along reactivated Iapetan basement structures. Abruptly, however, in late Chatfieldian–early Edenian (early Katian) time, subduction vergence apparently changed to the west, generating a regionally compressional regime that was accompanied by subsidence and change in regional dip, such that black shales and an underlying unconformity migrated westwardly. By Maysvillian (mid-Katian) time, the distribution of Utica and Utica-equivalent black shales show that the Appalachian and Michigan basins merged into one large, fully yoked basin. The coincidence of changes in basin shape and migration with the shift in subduction polarity suggests a causal relationship. The approximate time of polarity change is well-known from other sources, but is also well-constrained by the biostratigraphic ages of and changes in the distribution of the effected black shales.
February 23: Jim Best, University of Illinois. Title: Sedimentology of the fluvial-tidal transition: field studies of the lower Columbia River, WA/OR
March 2: Ralph Milliken, Brown University. Title: Water in the Solar System, a Story in Three Acts
Abstract: Water has played a key role in the formation and evolution of our solar system, yet many questions remain about its distribution, form and origin for planetary bodies. A host of spacecraft observations, ground-based measurements, and laboratory analyses of extraterrestrial samples over the past twenty years has dramatically changed our view of aqueous processes. Our knowledge of objects known to have a water-rich history, such as Mars, has benefited greatly from high-resolution orbital datasets. This has revealed important information about the role of surface fluids as well as the potential role of deep crustal fluids through geologic time. In contrast, detailed lab analyses have shown that a body previously believed to be dry, the Moon, may contain as much water in its mantle as Earth. More speculatively, the largest object in the asteroid belt, Ceres, may contain low-temperature alteration minerals due to silicate-water interaction in the earliest days of the solar system, a hypothesis that will be tested in the coming weeks with the arrival of NASA’s Dawn spacecraft. This presentation will focus on these planetary bodies in the context of how their geologic records inform us of the distribution, role, and fate of water in the solar system.
March 9: Bob Hazen, Carnegie Institution of Washington, Geophysical Laboratory. Title: Mineral evolution, mineral ecology, and the co-evolution of life and rocks
Abstract: Earth’s near-surface environment has evolved as a consequence of physical, chemical, and biological processes—an evolution that is preserved in the mineral record. Recent studies of mineral diversification through time reveal correlations with major geochemical, tectonic, and biological events, including large-scale changes in ocean chemistry, the supercontinent cycle, the increase of atmospheric oxygen, and the rise of the terrestrial biosphere. Growing data resources and emerging statistical methods point to significant roles of both chance and necessity in the mineral diversity of terrestrial planets.
March 23: Steve Bell, IU Biology. Title: Evolution of genome complexity – insights from the Archaea
Abstract: During evolution of life on Earth there has been an increase in the size and complexity of cellular genomes. Increasing size of genomes comes hand-in-hand with increasing temporal and regulatory burdens on the cell to ensure complete, timely and accurate replication. To date, all bacterial cells have their chromosomes replicated from a single start site, or "origin" of replication. In contrast, eukaryotes replicate their genomes from hundreds to thousands of origins. In the talk I will describe our work on organisms from life’s third domain – the Archaea. These cells represent an intriguing blend of bacterial-like morphology and cellular machineries and replication modes that resemble those of eukaryotes. In the talk I will describe some of our work to dissect the mechanistic basis of DNA replication. Additionally, I will discuss the insights that we have gained regarding the evolution of genome complexity
March 30: Julie Elliott, Purdue University. Title: Using Geodetic Imaging and Historical Photographs to Document Glacier Change in Alaska
April 6: Berry Lyons, The Ohio State University. Title: The Hydrology and Aquatic Geochemistry of the McMurdo dry Valleys, Antarctica
April 13: Jonathan Snow, University of Houston Title: Fire and Ice: Seafloor Spreading from the Arctic to the Equator.
Abstract: The fundamental question I will be addressing in this talk is: How does the hydrologic "plumbing system" evolve in volcanic landscapes, and how does the development of this plumbing feedback on the evolution of the landscape itself? By plumbing system I mean the network of surface and subsurface flowpaths by which precipitation recharges aquifers and ultimately emerges as streamflow. Questions like this are receiving increasing attention with the burgeoning attention being paid to the science of the Critical Zone: the thin but essential surface of the Earth between the boundary layer and bedrock where all terrestrial life occurs. Young volcanic landscapes, such as in the Cascade Range of the Pacific Northwest, offer an extraordinary laboratory for studying this co-evolution among geology, geomorphology, hydrology, and ecology, because they provide us with constructional landscapes of discernible age from which we can extract evolutionary sequences. Drawing on over a decade of studies in the Oregon Cascades, I will explore how channel networks and aquifers develop in volcanic terrains, the timescales involved, and the implications of this evolution for predicting where water is likely to be in the future.
April 20: Gordon Grant, USDA/Oregon State University. Title: From volcanoes to rivers: co-evolution of hydrologic and geomorphic processes in the Oregon Cascades
Abstract: The fundamental question I will be addressing in this talk is: How does the hydrologic "plumbing” system" evolve in volcanic landscapes, and how does the development of this plumbing feedback on the evolution of the landscape itself? By plumbing system I mean the network of surface and subsurface flowpaths by which precipitation recharges aquifers and ultimately emerges as streamflow. Questions like this are receiving increasing attention with the burgeoning attention being paid to the science of the Critical Zone: the thin but essential surface of the Earth between the boundary layer and bedrock where all terrestrial life occurs. Young volcanic landscapes, such as in the Cascade Range of the Pacific Northwest, offer an extraordinary laboratory for studying this co-evolution among geology, geomorphology, hydrology, and ecology, because they provide us with constructional landscapes of discernible age from which we can extract evolutionary sequences. Drawing on over a decade of studies in the Oregon Cascades, I will explore how channel networks and aquifers develop in volcanic terrains, the timescales involved, and the implications of this evolution for predicting where water is likely to be in the future.
April 27: Tori Hoehler, NASA Ames. Title: Biological Potential in Serpentinizing Systems
Abstract: Generation of the microbial substrate hydrogen during serpentinization, the aqueous alteration of ultramafic rocks, has focused interest on the potential of serpentinizing systems to support biological communities or even the origin of life. However the process also generates considerable alkalinity, a challenge to life, and both pH and hydrogen concentrations vary widely across natural systems as a result of different host rock and fluid composition and differing physical and hydrogeologic conditions. Biological potential is expected to vary in concert. We examined the impact of such variability on the bioenergetics of an example metabolism, methanogenesis, using a cell-scale reactive transport model to compare rates of metabolic energy generation as a function of physicochemical environment. Potential rates vary over more than 5 orders of magnitude, including bioenergetically non-viable conditions, across the range of naturally occurring conditions. In parallel, we assayed rates of hydrogen metabolism in wells associated with the actively serpentinizing Coast Range Ophiolite, which includes conditions more alkaline and considerably less reducing than is typical of serpentinizing systems. Hydrogen metabolism is observed at pH approaching 12 but, consistent with the model predictions, biological methanogenesis is not observed.