Geophysical Sciences

Faculty Research Summaries | Chairman's Introduction

Alfred T. Anderson, Jr.

My current research focuses on how volcanism contributes magmatic evolution, planetary outgassing and recycling of CO2 and H2O. Volcanoes may be primarily gas vents for buried bodies of magma. Emitted gas, although at igneous temperature may be juvenile or recycled. My current studies focus on the rhyolitic Bishop Tuff, California and the young Oruanui rhyolite from Taupo, New Zealand. Colin Wilson and postdoctoral associate Yang Liu are spearheading the work on the Oruanui rhyolite. Other collaborations continue with former postdoc Paul Wallace now with the Department of Geology, University of Oregon and other colleagues at the University of Michigan. Our work uses chemical and physical observation and analysis of pumice and melt inclusions in volcanic phenocrysts to assess the pressure of crystallization and the amount of exsolved gas in preeruptive magma. We are not yet sure if the gas is juvenile or recycled.

My work on rhyolitic magmas has focused on the Bishop Tuff, California. Graduate students Chris Skirius (now at Omni Labs, Houston) and Fangqiong Lu (now at IBM, Austin) analyzed H2O and CO2 (using infrared spectroscopy) and trace elements in melt inclusions (using the Chicago ion probe with the help of Andy Davis). Their work demonstrated that later erupting Bishop melt was poorer in H2O, richer in CO2 and less differentiated. Crystal sinking appears to have had a role in its evolution.

Post-doctoral associate Paul Wallace established the amount of exsolved gas that was in early-erupted Bishop magma. Big bodies of silicic magma may commonly contain large amounts of gas that have accumulated within them from huge underlying (?batholithic) reservoirs of magma. This concept has important implications for stratospheric injections of volcanic sulfur as well as for some ores and the outgassing and rigidification of new continental crust.

An ongoing effort focuses on the cathodoluminescent zoning of quartz phenocrysts in the Bishop Tuff. The crystals are concentrically zoned and the zoning is conspicuously correlated with the eruptive stratigraphy. The zoning is consistent with free-swimming solitary phenocrysts, and there is no evidence that the crystals were dislodged from intergrown aggregates such as would be expected from the largely crystalline walls of the magma. This work was spearheaded by Bret Peppard, a former undergraduate. Paul Wallace and several of us are continuing to look for a correlation between phenocryst sizes and their melt incusion compositions.

Joe Dufek (as an undergrad at U of C), Paul Wallace, and I are estimating cooling rates of H20-rich glass inclusions from Zhang's experimental work and relating these to stratigraphic level and depth beneath overlying ash-flows. The warming and cooling imposed by hot ash-flows that overlie the plinian pumice fall deposits can be used to constrain the thickness and temperature of the now-eroded ash-flow. The cooling rates of the glass inclusions in plinian pumice can constrain cooling in the eruptive column.

Since Fall of 2002 I have been working with a group of graduate students at Chicago to document and interpret the sizes of phenocryst in Bishop pumice. By combining several approaches, including synchrocron X-ray tomography, we have documented the number density of phenocrysts as a function of their size. We found a three-fold variation in crystal content that unexpectedly correlates inversely with the vesicle content. This correlation suggests that crystals sank out of the magma and bubbles accumulated into it. Our manuscript was presented by one of the students (Guilherme Gualda) at the 5th Hutton Symposium on the Origin of Granites, August, 2003, Japan. We are continuing the work by analyzing the compositions of melt inclusions, glassy reentrants and hourglass inclusions in phenocrysts from the same pumice clasts.

David Archer

My interests are all pretty closely tied to the marine carbon cycle, today and in the past, at the sea surface and in the sediments of the deep sea. The ocean contains fifty times as much CO2 as the atmosphere, and the pH and pCO2 of the ocean are actually buffered (stabilized) by vast reserves of carbon stored as calcium carbonate in deep sea sediments. Hence the ocean controls the atmospheric CO2 concentration, on time scales of thousands to hundreds of thousands of years, and changes in ocean dynamics can drive changes in the CO2 of the atmosphere.

At the end of the last ice age, for example, carbon was removed from the atmosphere by growth of forests. The oceanic CO2 exhale that resulted is documented by a "spike" of calcium carbonate preservation in sediments (the counter-intuitive backwards behavior is caused by the systematics of carbonate pH equilibrium chemistry). By the analogous process in reverse the ultimate sink for the fossil fuel CO2 will be to enter the ocean and dissolve sedimentary calcium carbonate. Some change in the dynamics of the ocean carbon cycle (as yet not well understood) drove the interglacial atmospheric CO2 to higher levels than the glacial, as recorded in samples of ancient air trapped in bubbles in polar ice cores.

My research focuses on understanding the dynamics of CO2 dissolved in the ocean and how it interacts with circulation and biology of the ocean, and on learning how to interpret various signals stored in the sedimentary record in terms diagnostic of the carbon cycle in past climates. One current project is to improve the representation of coastal oceanography in the coarse-resolution global ocean circulation models that we use to do carbon cycle research. I am also working on modeling the abundance and stability of methane hydrate deposits in coastal ocean sediments, the interaction of shallow-water sediments with fossil fuel CO2, and the distribution of redox-sensitive trace metals such as rhenium and uranium as indicators of paleo sedimentary conditions.

C. Kevin Boyce

I am interested in the evolution of plant structure, development, and physiology during the Paleozoic colonization of land and subsequent radiation of land plant form. Of particular emphasis is the evolution of novel organ and cell types and comparison of the multiple independent evolutions of structures such as roots, leaves, and wood in different plant lineages. The first of two main approaches that I use in my research is comparative, cell- and tissue-specific analysis of elemental, isotopic, and organic chemistry in living plants and anatomically preserved fossils. This has required the adaptation of existing chemical techniques, such as the electron microprobe, isotope ratio mass spectrometry, and X-ray spectromicroscopy, to the study of fossils and has required taphonomic studies of how the chemistry of fossils changes during diagenesis. A primary application of this approach has been to the evolution of vascular cells and questions such as how the unique characteristics of these cells were assembled in the extremely simple, pre-vascular plants of the Silurian and Devonian and how physiologically important details of cell wall chemistry have been modified during the proliferation of vascular cell types and rise in land plant complexity. Chemical analyses are also being used to interpret enigmatic fossils of controversial biological affinity. A second approach involves developmental and physiological study of living plants in conjunction with detailed surveys of morphological evolution in the fossil record. The primary subject of this approach has been the independent evolution of laminate leaves in at least four different lineages during the Paleozoic as well as the post-Paleozoic patterns of drastic rearrangement of how leaves are constructed. The question driving much of this work is to what extent the frequent, extreme convergence of morphology seen in the fossil record also has required evolutionary convergence of development and physiology.

Bruce A. Buffett

Advances in computing capabilities over the past few years have made it feasible to simulate the generation of Earth's magnetic field. Early efforts of various workers have been remarkably successful in the sense that models can now reproduce the dominant features of Earth's field at the surface. However, the internal workings of different models are surprisingly discordant. We are working to develop better dynamo models by devising more realistic parameterizations of the sub-grid-scale processes. We are also involved in an effort to distinguish between possible models by making novel use of available observations. Variations in the magnetic field, changes in the length of day, and fluctuations in the global gravity field all contain signatures of the convective processes in Earth's liquid iron core. We are currently developing a new theoretical framework to jointly invert these observations to make inferences about the structure of the internal magnetic field and the influence of this field on the style of convection in the core.

Robert N. Clayton

(See Department of Chemistry)

Nicolas Dauphas

My interests are closely tied to the question of origins. Which processes governed the synthesis of the elements? How did matter expelled from the successive generations of stars contribute to shape the cosmic abundances  of the elements? How and when did solar system bodies such as planets,  asteroids, and comets form? How did the Earth get its wet atmosphere? What is the oldest geological record of life on Earth? For addressing these questions, I study the natural distribution of elements and isotopes using various instruments designed for separating nuclides according to their  mass.

Gidon Eshel

My research focuses on ocean-atmosphere dynamics and interactions relevant to the Earth's climate.

One ongoing project focuses on the formation of deep waters. In this process, warm/fresh surface water loses sufficient heat and fresh water to the atmosphere (by cooling and evaporation) to become dense enough to sink to great depths. Since this is a very complicated process, in which oceanic and atmospheric dynamics and thermodynamics interact on small space and time scales, it is very hard to observe. To overcome this major difficulty, my approach has been to employ a 'natural lab'. That is, I study the process in the smaller, better observed northern Red Sea, assuming that some of the insights are applicable to larger scales and other sites. In the past, I used a numerical model to study this phenomenon. More recently, we use corals from the formation region to study long-term variability of formation. We have already used relatively modern corals to construct a simple theory for regional air-sea interactions and the evolution of surface density (the key dynamical variable controlling water mass formation). Currently we are working on a 300 year long coral record, which documents the interplay between tropical modes of climate variability (primarily El Nino-Southern Oscillation and Monsoon), and mid-latitude ones (the North Atlantic Oscillation).

Another project involves understanding and forecasting Eastern Mediterranean rainfall variability. Using atmospheric and surface data and statistical techniques, we are now able to forecast Eastern Mediterranean winter rainfall variability robustly and skillfully, with obvious practical applications. More fundamentally, the work demonstrates and explains the influence of planetary waves on downstream predictability. The inherent predictability of the North Atlantic/European sector, which emerges from this work, is something I will pursue in the near future.

My most recent work (circa mid-2001) addresses predictability of geophysical/climate phenomena in general, and the North Atlantic Oscillation in particular. The work has so far yielded a novel approach to statistical forecasting that is based on drastically reduced-dimension phase-space history of the studied phenomena. The North Atlantic Oscillation makes an excellent test bed in which to evaluate the method's performance. The work addresses the interannual and decadal timescales separately, and, in both, shows extended, substantial predictive skill that has not been reported or suggested previously.

Michael J. Foote

My research focuses on rates of evolution, diversity dynamics, and large-scale patterns of origination and extinction in the fossil record. This work involves analysis of stratigraphic, geographic, and environmental occurrences of species as well as mathematical modeling of evolution and of paleontological incompleteness. I am currently investigating a number of questions, including: (1) To what extent is temporal variation in diversity correlated with variation in origination versus extinction rates, and how is this correlation influenced by environmental setting? (2) Are origination and extinction events in earth history concentrated in brief episodes of turnover or spread out over longer intervals of time? (3) How can we estimate true patterns of taxonomic diversity given the incomplete data of the fossil record? and (4) How can data on living organisms be made commensurate with paleontological data so that extinction rates in the present day can be meaningfully compared with extinction rates in the geologic past?

John E. Frederick

Current research focuses on studies in radiative transfer, including the conduct and analysis of ground-based solar and terrestrial radiation measurements. The goal is to advance understanding of the physical mechanisms that control the energy balance of urbanized regions. Of particular interest is the role of urbanization in modifying the optical properties of the atmosphere on regional scales. Specific topics of interest include the roles of scattering by clouds, scattering and absorption by particulate matter and trapping of upwelling thermal radiation by particles and gases of urban origin.

Recent work has examined the influence of urban particle layers on the opacity of the atmosphere in polluted regions. When the particles include a substantial amount of carbon, the visible solar irradiance can be reduced to 70% of the values appropriate to clear skies. In the ultraviolet the interaction of absorption by ozone in a polluted boundary layer and scattering by particles can lead to irradiances which are only 50-60% of the clear-sky values. Related studies have also considered the role of absorption by particles contained in cloud droplets and the influence of enhanced particle amounts on cloud optical properties via modifications of the drop size distribution.

Finally, collaboration with researchers in the Center for Integrating Statistical and Environmental Sciences focuses on quantifying the relationship between respiratory health, air quality and natural factors, such as pollen, in the Chicago metropolitan area.

Mark S. Ghiorso

I am interested in the thermodynamic properties of materials, particularly those naturally occurring substances that make up the Earth, and especially minerals and liquids at higher temperatures and pressures. My work is motivated by a desire to understand the chemical differentiation of the Earth, which is driven by melting of the interior to form magma, with subsequent transport and delivery of that molten material to the surface. My research mainly falls under the category of computational thermodynamics, although I devote quite a bit of effort to the study of minerals, their phase transitions, and the energetics of ordering and disordering of atoms in these structures. My previous work has touched on high-temperature water-rock interaction and the formation of ore deposits and both terrestrial and submarine hot spring systems. I have also worked on chemical diffusion as well as the rate of crystal growth in molten silicate systems at high temperature. My current research is focused on the development, calibration and implementation of an equation of state (a relation between density, temperature and pressure) for molten silicate liquids that will allow calculation of the thermodynamic properties of this phase to very high pressures corresponding to depths in the Earth of ~1,000 km. The objective is to use this tool to calculate degrees of melting at these depths with the hope of better understanding the chemistry of volcanic rocks found at the Earth’s surface whose source regions are thought to sample this melting regime.

Lawrence Grossman

We study the mineralogical, chemical, and isotopic compositions of inclusions in chondritic meteorites and perform thermodynamic calculations on the stabilities of solids and liquids in cosmic gases. The purposes of our research are to elucidate the behavior of the elements during condensation of the solar system; infer the degree of physical, chemical, and isotopic heterogeneity in the presolar nebula; and determine what components were available in the nebula for accretion into meteorites and planets.

Dion L. Heinz

My main areas of interest are mineral physics and materials research. Mineral physics is the study of the chemical and physical properties of minerals applied to problems in the evolution and dynamics of planetary bodies. We use the diamond anvil cell to study simple materials as well as minerals at high pressures. The pressures that we can achieve are in excess of 100GPa or one million atmospheres, which corresponds to 2,500 km depth in the Earth. By using a laser to heat a sample we can reach temperatures of 6000 K while the sample is at high pressure.

These methods allow us to perform a wide variety of petrologic experiments at lower mantle pressures and temperatures. For instance we measure solid-solid and solid-liquid phase transformations as a function of temperature and pressure, as well as major and minor element partitioning between coexisting phases. Synchrotron radiation is used to measure equations of state of materials as a function of temperature and pressure. The combination of our laser heating technology with synchrotron radiation to make in situ measurements that are appropriate for the Earth's deep interior is one of our most important tools.

Diamonds are transparent to a wide range of electromagnetic radiation, which makes them a very good window material for a wide variety of spectroscopic techniques. In particular we are interested in using infrared, Raman and Brillouin spectroscopy on Earth materials. A combination of vibrational spectroscopy and the principles of solid state physics can place important constraints on the thermodynamic properties of Earth materials. Brillouin scattering is used to measure elastic constants of materials at high pressures, for comparison with elastic velocities derived from seismic models.

David Jablonski

My research focuses on macroevolution, the origins and fates of higher taxa and major adaptations. My work in the marine fossil record has focused recently on the evolutionary role of mass extinctions, on the ecology of major evolutionary novelties over the past 250 million years, and on the evolutionary and spatial dynamics of the latitudinal diversity gradient. I have found that mass extinctions are more profoundly disruptive of normal evolutionary processes than previously thought. Recoveries have also proven to play a crucial role in shaping large-scale evolutionary patterns, and turn out to be more variable geographically than expected, with some regions more subject to invasion and others showing diversifications fueled by local survivors. I have also found that major novelties do not originate randomly, but tend to appear in shallower, more unstable habitats, and in tropical settings. This work is being combined with analyses of biogeographic and evolutionary patterns in late Cenozoic-Recent marine mollusks to gain a fuller picture of evolutionary dynamics across latitudinal gradients, and among groups with contrasting larval and adult ecologies. The debate on whether the tropics are an evolutionary cradle or a museum is founded on a false dichotomy—analysis of marine mollusks in collaboration with Kaustuv Roy (San Diegeo) and James Valentine (Berkeley) show that the tropics are both the source and accumulator of biological diversity.These lines of research have implications not only for the evolutionary process but for conservation and biodiversity studies: past biological behaviors can provide a basis for anticipating future responses.

Susan M. Kidwell

My primary research interest is in quantifying the archival quality of the geologic record–the recognition, analysis and genesis of incompleteness (gaps, omission) and bias (skewing) in the physical and biological materials that survive for study by geologists and paleobiologists. Solo and collaborative research efforts, and the independent work of student advisees, have focused on identifying key patterns and drivers of differential record quality, particularly how and why quality varies as a function of environment (habitat, relative sealevel phase, tectonic setting, latitude, etc.), geologic age, and taxonomic or functional group. Subjects of particular interest include (1) unconformities and condensed intervals in stratigraphic records, (2) rates and selectivities in organic recycling and modification, and (3) increasingly, the practical application of death assemblages to modern conservation issues and the testing of biological principles (e.g., biodiversity inventory of present-day systems, reconstruction of ecological time-series via sedimentary cores and the integration of neo- and paleo-biologic data).

My current projects are (a) mentoring Ph.D. candidate Yael Furstenberg's field project on paleoecologic evaluation of paleo-oxygen in high-productivity settings, using the modern Namibian shelf as a possible analog for the Cretaceous Mishash Fm of Israel (wrap-up phase; supported by the Petroleum Research Fund and by the US Israel Binational Science Foundation); (b) reconstructing the extensional evolution of the Salton Trough/ northern Gulf of California via mapping complex Neogene stratigraphic relations with collaborator Charles Winker (Shell) (ongoing; field support from the Southern California Area Mapping Project of USGS); (c) integrating geochronologic data with field and experimental taphonomic data of former advisee Mairi Best (McGill University) and porewater geochemical data of collaborators Tim Ku & Lynn Walter (University of Michigan) to quantify skeletal recycling rates and selectivities in carbonate and siliciclastic sediments of Caribbean Panama (largely write-up phase; supported by NSF EAR); (d) data-mining and meta-analysis of ecological and fisheries studies to quantify the fidelity of molluscan death assemblages with respect to species composition, relative abundance, richness, body size patterns and, with collaborator Tom Olszewski (Texas A&M), community evenness (relatively new project; proposal pending with NSF EAR); (e) building a database of sedimentary core data relevant to ecological collapse in modern coastal habitats as part of a collaborative project on the role of overfishing (top-down disruption of food webs), a working group led by Jeremy Jackson (Scripps) (ongoing; funded by the NSF National Center for Ecological Analysis and Synthesis at UCSB); and (f) I am building a series of undergraduate lab exercises based on the Overfishing project to introduce students to the value of geohistorical (sedimentary) records in evaluating natural and anthropogenic effects on modern ecosystems. The first lab focuses on the Chesapeake Bay (see pdf associated with my web-page) and was used in the core course Physical Sciences 110 in Spring 2003; this will be improved and enlarged for use in Physical Sciences 110 and in our concentrators course Geophysical Sciences 132 in Spring 2004.

I currently advise the independent research projects of four other Ph.D. students (T. Rothfus, Norwegian Federal Fellow B. Hannisdal, P. Anderson, NSF Fellow R. Terry), chair the Student Advisory Committee of the Committee on Evolutionary Biology, and serve on the Advisory Committee of the GEO Directorate of NSF.

Michael C. LaBarbera

My research concentrates on the biomechanics of living and fossil marine invertebrates, applying the basic principles of solid and fluid mechanics to understand the functional morphology of these animals. Major areas of ongoing research include particle?capture mechanisms in suspension?feeding animals, the relation between pinnular and tube?foot morphology and hydrodynamic environments in crinoids, lophophore scaling and hydrodynamics in articulate and inarticulate brachiopods, swimming mechanics in scallops, aspects of shell design in gastropod and bivalve molluscs, and the hydrodynamics of circulatory systems.

Douglas R. MacAyeal

My research focuses in two main areas: (1) the study of iceberg drift in the Ross Sea, Antarctica, and (2) the computation of normal modes of the world ocean for use in understanding how the ocean's tidal regime changes across the glacial cycle. The first area of research takes me and my students (both graduate and undergraduate) to Antarctica where we deploy iceberg-tracking stations on some of the Earth's largest floating objects (B15 and C16, two titanic icebergs which calved from the Ross Ice Shelf in 2000).

Pamela Martin

My research broadly focuses on reconstructing changes in past deep ocean temperature, chemistry, and circulation to understand oceanic controls on climate change. I am interested in the links between the ocean biogeochemical cycles, atmospheric carbon dioxide and climate change on timescales ranging from changes in the earth’s orbit (hundreds of thousands of years) to anthropogenic variations (decades to millennium). I make measurements of the chemical composition of fossils to document climate changes in the geologic record and use numerical models to investigate the ocean’s role in the climate system. Some problems that I am currently pursuing with the help of graduate and undergraduate students include:

• Fossil shell magnesium content as a deep water temperature proxy

Accurate reconstruction of deep sea temperatures from fossil shell chemistry (Mg/Ca) relies on accurate calibration of this paleo-thermometer and an understanding of how it works under varying environmental conditions. Deep ocean temperature most likely changed in concert with changes in nutrient levels and other aspects of ocean chemistry; thus, it is important to understand all of the controls on shell chemistry. We are concurrently pursuing using shell chemistry to reconstruct changes in ocean temperature over the last million years. My initial focus in this area is on improving deep sea temperature estimates for the Pleistocene (generating new records) and investigating the factors that could give rise to the temperature changes using ocean circulation models.

• Reconstruction of glacial ocean carbonate chemistry

Deep ocean chemistry and circulation plays an important role in redistributing nutrients and, as a storehouse for carbon, regulating atmospheric carbon dioxide. Accurately quantifying changes in glacial carbonate chemistry of the deep ocean would be an important step towards explaining the large Quaternary oscillations in atmospheric carbon dioxide, one of the most puzzling aspects of glacial-interglacial climate change. It may also prove to be an important parameter for accurately reconstructing ocean temperatures because the effect dissolution has on shell chemistry.

• Sapropel formation in the Mediterranean

Episodic formation of organic rich layers of sediment, sapropels, have occurred in the Mediterranean since the Miocene, and is one of the classic problems in paleoceanography. Two alternative circulation scenarios have been proposed to explain sapropel formation: 1) a weakened anti-estuarine mode (with a circulation pattern similar to today); and, 2) a reversed, estuarine mode where waters enter at depth and exit as surface waters. Recent studies favor the weakened anti-estuarine scheme; however, that scheme cannot account for the high concentrations of organic carbon. We are approaching this problem by (1) generating new fossil shell chemistry data from sediment cores to reconstruct environmental and chemical conditions in the Mediterranean Ocean and (2) using this new data (nutrient concentrations, temperature and salinity of surface and deep waters) to model changes in the circulation and biogeochemical cycling within the Mediterranean including the sediment geochemistry, a key component not included in previous modeling studies.

Noboru Nakamura

My research concerns fundamental dynamical processes in the atmosphere and ocean, and the current investigation includes three areas: (1) theory and diagnostics of mixing, (2) dynamics of the midlatitude troposphere, (3) laboratory experiments of geophysical turbulence.

In the atmosphere and ocean the dynamical and chemical properties of fluid mass often varies rapidly across a narrow transitional region. Examples include the tropopause, the edge of the stratospheric polar vortex, and the oceanic thermocline. The rate of exchange and irreversible mixing of substance across such interfaces is important for assessing the efficiency of environmental chemistry. We have developed rigorous yet efficient methods for computing effective diffusivity using a numerically synthesized tracer. The method is currently being exploited in the analysis of various stratospheric data.

We are also investigating the role of large-scale eddies in shaping up the midlatitude tropopause, using a hierarchy of mathematical models. This problem addresses the very fundamental question as to why the troposphere is separated from the stratosphere and what determines the height at which such separation occurs.

Our latest effort is collaboration with other faculty members of the Department to re-establish hydrodynamics laboratory for research/instruction. When completed in 2004, this facility will be used, among others, to study behaviors turbulence within rotating fluids.

Synte L. Peacock

My main research interests share the common link of utilizing tracer distributions in the ocean, to address questions from rates of transport to the temporal evolution of ocean uptake of various atmospheric trace gases.

Anthropogenic gases such as chlorofluorocarbons, which have entered the atmosphere over the past half century or so, and which have then entered the ocean via air-sea gas exchange, provide a unique 'dye' with which to track ocean circulation. Naturally occurring radioactive substances, such as radiocarbon and argon-39, can provide complementary information on timescales of ocean ventilation.

I have been working with two fundamentally different ocean general circulation models to address various tracer-related questions: POP (Parallel Ocean Program; a z-coordinate model) and MICOM (Miami Isopycnal Coordinate Ocean Model; which uses density as its vertical coordinate).

Current research topics include simulation of the age distribution of the ocean; exploring how model resolution affects simulated tracer distributions; validation of ocean models using transient tracers; and placing tighter constraints on the amount of anthropogenic CO2 which has entered the ocean.

Raymond T. Pierrehumbert

My research is directed toward understanding the physical and fluid dynamical processes that govern the climate of the Earth and other planets having an atmosphere. This has involved inquiries into genesis of atmospheric eddies by instability, and the nature of the consequent mixing. I have also been looking at theories and observations of moisture and potential vorticity transport in the Earth's atmosphere. Currently, it is not even known why the present atmosphere carries so much less water than it would at saturation; moistening of the atmosphere would result in considerable warming of the planet. We are also engaged in research on the present and past climate of Mars, soon to be aided by data from the Mars Explorer mission.

Work of a more abstract mathematical nature, but distantly related to the above, has revolved around Hamiltonian chaos, mixing problems, and area?preserving maps. Work is underway in allied fields, including fractal patterns of concentration gradients, two dimensional turbulence (simulations and theory), and probability distributions of passive and active tracers.

Frank M. Richter

My recent research focuses on geochemical signatures, especially kinetic isotope fractionation, associated with particular transport processes such as evaporation and chemical diffusion. The evaporation kinetics of molten silicates and the associated chemical and isotope fractionation of evaporation residues has been studied via laboratory experiments and theoretical models, and the results used as constraints on the thermal evolution of calcium-aluminum-rich inclusions from chondritic meteorites. These inclusions are among the earliest materials to have formed in the solar system and their thermal evolution is thus a clue to conditions prevailing at that very early state.

It has long been known that chemical diffusion in a gaseous medium will produce mass dependent isotope fractionation. We have now shown that chemical diffusion in a silicate melt will also fractionate isotopes to a degree that is much smaller than in a gas, but still large compared to our present ability to measure isotopic differences. For example, we have shown that chemical diffusion between a natural basalt melt and a natural rhyolite melt fractionates 40Ca from 44Ca by about 0.5% (relative to analytical precision of about 0.02%) and 6Li from 7Li by 4%. We have also shown that diffusion of water in rhyolite melt results in very significant fractionations of hydrogen from deuterium.

The common theme to this research is finding geochemical "fingerprints" for identifying when and to what degree particular transport mechanisms operated.

David B. Rowley

My current research can be separated into four main components: (1) Paleoaltimetry and paleohypsometry of mountain belts; (2) Age of initiation of the collision of India with Asia; (3) Exhumation of ultrahigh pressure metamorphic rocks in orogenic belts; and (4) Mesozoic and Cenozoic global plate motions and paleogeography.

Altitudes and particularly hypsometry are closely linked to large-scale crustal and mantle dynamics. A major problem is that we have very few techniques for extracting paleo-altitude estimates from the geologic record. I have been working on paleoaltimetry and paleohypsometry with Ray Pierrehumbert to develop a 1-D model of the behavior of oxygen and hydrogen isotopes in orographic precipitation to derive estimates of the heights at which precipitation fell and then accumulated in rivers, lakes, and soils in mountains. The basis of this work has been published in Earth and Planetary Science Letters. Using modern samples we have shown that we can extract both spot elevation and also hypsometric estimates. The initial application of the model to sediments preserved in basins in the High Himalayas revealed that the hypsometry of the front of the Himalayas has not changed in the last 10 million years or so. Current work is extending our analysis to older sequences preserved in the Himalayas and Tibet. Field mapping within Tibet and the Himalayas is intrinsically a part of this research. I am also beginning to work in the northern Andes to look at the development of this orogen as well. The development of the Himalayas and Tibet are directly related to the collision of India with Asia. Perhaps surprisingly we know relatively little about when collision began. Over the past several years I have been working in collaboration with Bill Kidd and student Bin Zhu at Albany, and Brian Currie, former post-doc here, and now on the faculty at Miami University in Ohio, to better constrain the age of onset of collision in the area north and east of Mount Everest. Work on exhumation of ultrahigh pressure (UHP) metamorphic rocks has focused on mapping relatively small, but critical localities in the Dabie Shan. Our focus has been to identify and map a number of very large faults that control exhumation. Mapping with former Ph.D. student and post-doc, Feng Xue, was the first to identify and name the Huwan Detachment that delimits the northern margin of the UHP rocks. Work on dating the age and kinematics of these faults is ongoing.

Finally, I continue to be involved in understanding the plate kinematic history of the Late Paleozoic, Mesozoic and Cenozoic through refining plate motion models. I have taken over the Paleographic Atlas Project, started by Fred Ziegler, that focuses on interpreting the geologic record in terms of its implications for the paleogeographic evolution of the world. Most recently this has led to a reassessment of the global ridge production history. This work, published in the Geological Society of America Bulletin, reveals that the preserved distribution of areas of oceanic lithosphere as a function of age is most readily interpreted as indicating that the global rate of seafloor production has been constant over the past 180 Ma. Ongoing collaborative work with Jerry Mitrovica (U of Toronto) and Alesandro Forte (Université du Québec à Montréal) seeks to link mantle dynamic and changing positions of continents to the evolution of dynamic topography and its implications for records of long-term sea level change.

Joseph V. Smith

Zeolite, aluminophosphate and other molecular sieves used as catalysts in the petroleum industry and ion-exchangers in the detergent industry. Mathematical topology of nets.

Determination of crystal structures by X-ray and neutron diffraction, magic-angle nuclear magnetic resonance, and energy calculations. Particular emphasis is being placed on synchrotron and pulsed-neutron sources.

Microanalytical techniques for spot analyses with particular emphasis on X-ray fluorescence (Advanced Photon Source) and electron and proton microprobe analysis of trace elements.

Mineralogy and chemistry of the earth's upper mantle and early crust, particularly factors related to origin of life and development of new species.

Investigation of the origin of minerals in sediments and soils using trace-element chemistry.

Crystal structure determination of minerals containing toxic elements of environmental significance, especially those in ore fields and waste deposits.

Geology and human welfare: covers volcanoes, earthquakes, tsunamis, coastal and lake erosion, landslides, hurricanes and typhoons, effects on earth's surface of civilization and industrialization ethics.

Museum conservation, with current emphasis on beads on royal thrones from Cameroon.

Ramesh C. Srivastava

My research is in the areas of cloud physics and radar meteorology. In clouds the initial growth of drops occurs by the diffusion of water vapor; subsequent growth to larger sizes occurs through collisions and coalescence of drops. I am involved in theoretical studies of both the processes.

Knowledge of the size distribution of raindrops (and other hydrometeors) and their electromagnetic scattering and extinction characteristics is crucial for remote measurement of precipitation by radar. The second item of my research involves interpreting and relating observations of precipitation particle size distributions to the radar returns from the clouds responsible for the precipitation.

Mark Webster

I study the ontogenetic development, morphology, and morphological variability of trilobite species in order to understand the paleobiology and evolutionary history of these organisms in unparalleled detail. Current projects include: (1) quantification and decomposition of the morphological variability within Early Cambrian olenelloid trilobite species into phylogenetic, environmental, and temporal components; (2) resolution of the phylogenetic relationships among basal trilobite groups; (3) analysis of evolutionary modification to trilobite ontogeny; and (4) investigation of broad-scale trends in trilobite evolution (such as homoplasy and polymorphism) and their implications for the Cambrian radiation.

Senior Research Associates in the Department

Andrew Campbell

Chemical evolution of planetary materials, with a particular emphasis on metals and other components of planetary cores. Experimental and analytical methods, including high pressure techniques and laser ablation ICP mass spectrometry, to understand the trace element and major element chemistry of meteorites as well as planetary interiors, refining our knowledge of the physical and chemical processes influencing solar nebula evolution and planetary formation and differentiation.

Ruslan Mendybaev

Experimental modeling of high and low temperature geochemical processes such as: evaporation of the silicate melts in a controlled gas atmosphere and in a vacuum; kinetic isotope fractionation caused by the evaporation or by the chemical diffusion in the salt-water systems. Experimental reproduction of the textural, chemical and mineralogical signatures of the refractory Ca-Al-rich inclusions found in carbonaceous chondrites in order to place constraints on the conditions in the early solar nebula where these objects have been formed.

Joseph J. Pluth

The application of X-ray, neutron, and synchrotron radiation diffraction to single-crystal and powder structural studies of materials. Development of techniques to determine crystal structures using microcrystals (single crystals less than 5 micrometers) at the Advanced Photon Source at Argonne National Laboratory. Structural studies of zeolites, aluminophosphates and other microporous materials to understand the relationship between structure and catalytic activity. In situ neutron powder diffraction structural studies of lead acid batteries undergoing conventional and rapid charging.

Mark L. Rivers

Development of synchrotron x-ray techniques, including fluorescence microprobe, diffraction, spectroscopy and microtomography. Development of x-ray optics and software to support these techniques. Application of these techniques to the study of earth and planetary materials.

Steve Simon

I study the mineralogy, petrography, and mineral chemistry of refractory inclusions found in carbonaceous chondrites, using the optical microscope, scanning electron microscope, and electron microprobe. We interpret the textures, mineral compositions, and bulk compositions of these objects in our attempts to determine how they formed. These objects are some of the first solids formed in the solar system, and study of them can give us important insights into the formation and early evolution of the solar system.

Ian M. Steele

Applications of microchemical analysis techniques using X-ray, electron, neutron and ion beams. Descriptions of changes in the active material over the lifetime of lead acid batteries with the goal of extending their life for use in electric and hybrid vehicles. Applications of CCD based single crystal diffractometers for crystal structure determinations in both the chemical and geological sciences. Mineralogy of meteorites with respect to the origin of the major silicate phases prior to formation of meteorites.

Stephen R. Sutton

Development and application of synchrotron x-ray microanalysis instrumentation and methods for trace element measurements using x-ray fluorescence microprobe and chemical speciation determinations using x-ray absorption spectroscopy. Applications focus on problems in geochemistry, planetary science, and environmental science, including chemistry of primitive extraterrestrial materials, speciation and mobility of contaminating chemical species in the environment, and oxidation state determinations of trace elements in minerals and glasses.