In the summer of 2000, 15 interns spent 6-10 weeks in the Department of Geology & Geophysics. The research projects were supplemented by optional field trips to the caves of southern Minnesota, the Minnesota River Valley, Lake Superior (cruise on the Blue Heron research vessel), and the famous Duluth gabbro and North Shore volcanics along the scenic shore of Lake Superior (part of the Proterozoic mid-continent rift system).

2000 Interns

Jen Bobich (Penn State). Tectonics. Jen explored fault deformation on the Greek island of Rhodes, as part of a collaborative project to study the tectonic evolution of Rhodes and Crete. Summer research involved sample preparation for isotopic dating of microfossils in deformed sediments, to bracket the age of deformation; examination of fault characteristics to determine stress directions; creation of 3d shaded surface images to provide a view of the stress fields on Rhodes to help interpret the number of deformation episodes; and design of a device to simulate oblique divergence to model tectonics vs. sedimentary processes. (advisers: Kleinspehn, ten Veen)

Laura Clor (College of Wooster). Geophysics/mineral physics. Conducted grain boundary migration experiments with olivine to study the effects of crystallographic orientation on grain boundary migration distance. Seismic anisotropy provides an important clue as to the nature of flow in the mantle but the relationship between flow pattern and seismic anisotropy has not been well-understood because of the complications of the processes by which anisotropic structures might be formed. To study the orientation dependence of boundary mobility, the velocity of grain-boundary migration for many boundaries with different orientations must be determined. The experiments involved preparing single crystals of olivine with a high degree of structural dislocations by subjecting them to high pressures for specific amounts of time.  Polycrystalline samples with few dislocations were also prepared, and the effects of adjacent crystals with high vs. low dislocation densities were examined.  (adviser: Karato)

Billy D'Andrea (SUNY-Binghamton). Limnogeology. Billy worked in the Limnological Research Center on lake cores collected from Lake Zeribar, Iran.  He and Beth Erickson (see below ) prepared 80 samples from the core in order to separate ostracodes from mud. They performed loss on ignition measurements to calculate relative amounts of the volatile components of each sample. (adviser: Ito)

Beth Erickson (University of the South). Limnogeology. Beth worked in the Limnological Research Center on lake cores collected from Lake Zeribar, Iran.  She prepared samples for isotopic analysis and determination of volatile content. She also helped collect ostracodes in local Twin Cities lakes with Karen Hays for a study the behavior of live ostracodes. (adviser: Ito)

Nicole Feldl (University of North Carolina - Chapel Hill). Sedimentology. Nicole ran physical experiments to look at the transition from upper plane bed parallel lamination to massive deposition, as typified in the Bouma sequence of turbidites. The experiments were conducted in a recirculating flume, and hoppers were set on top of the flume to provide a sediment influx and control sediment fallout rate. (adviser: Paola)

Mark Heil (San Juan College). Limnogeology. Worked on developing methods and techniques for extracting climatic information from annually-laminated sediments.  The focus of the study were several hundred meters of varved sediments from Michigan recovered the previous year by a team from LRC, but Mark and others took an additional field excursion to collect varved sediments from Michigan lakes.  After splitting and describing the cores, he spent time developing a digital imaging system for counting and measuring varve thickness, made the measurements, and plotted the results to examine how varve thickness varied over time in relation to climatic and environmental changes both at a regional and a local scale.  He detected a marked increase in varved thickness relating to local vegetation disturbance (logging and agriculture) in the recent record.  (advisers: Ito and Schnurrenberger)

Sonja Heuscher (Colorado School of Mines). Soil chemistry/groundwater. Sonja studied the cation exchange capacity of some Minnesota soils, to examine effects on groundwater chemistry. She ran simulated hog manure solutions (ammonium acetate and ammonium chloride) through soil columns and collected column effluent fractions while monitoring flow and conductivity. The resulting ion chromatograms indicated order of ion breakthrough and allowed calculation of cation exchange coefficients for specific soil types. Cation concentrations were measured with ICP-MS and anion concentrations with ion chromatography. Results showed that ammonia breakthrough occurred, indicating that the exchange capacity of the soil was overloaded. (adviser: Alexander)

 
 
 
 
 
 
 
 
 

Lauren Jankovic (Purdue University). Limnogeology. Researched sulfur in lake sediments: reasons for accumulation/no accumulation in sediments from Lake Victoria and Lake Edward in East Africa.  The percent sulfur in the sample was obtained using a sulfur coulometer. Some of the other procedures used to investigate lake sediments included coarse fractioning, preparation of x-ray diffraction slides, sampling and making of smear slides. (adviser: Kelts)

Kimberly McGlynn (University of North Dakota). Isotope geochemistry. Kimberly applied U/Th dating methods to corals that most likely represented a marine transgression for oxygen Isotope stage 5a along the coast of Virginia. Analytical methods included XRD analysis and mass spectrometry. (adviser: Larry Edwards)

Joanna Minott (Mt. Holyoke College). Geophysics/magnetism. Joanna researched the effects of climate on magnetic properties of Nebraska's Holocene loess and paleosols. She studied three sites along a transect that had equal loess thickness but different amounts of precipitation. The study involved measuring magnetic and non-magnetic multi-parameters on the cores at each site. The results showed a positive correlation between precipitation and magnetic enhancement. (advisers: Christoph Geiss, Subir Banerjee)

Marylee Murphy (Colby College). Geophysics. Marylee and co-workers at the Minneapolis Supercomputer Institute conducted numerical experiments of mantle convection. They focused on the development of secondary instabilities developed from plumes and compared results  with laboratory experiments of other workers. Results showed that secondary instabilities can develop from a single plume. When applied to the upper mantle, these results may explain the formation of hot-spots in a turbulently convecting upper-mantle. Marylee's paper on this work, submitted to Electronic Geosciences, can be read at http://link.springer.de/link/service/journals/10069/discussion/murphy/murphy.html. (adviser: Yuen)

Mehgan O'Hearn (Augustana College). Metamorphic geology/experimental petrology. Mehgan investigated the fate of subducted sediments by conducting an experimental simulation of subduction zone conditions. The motivation of the study was to understand the dehydration and/or partial melting behavior of sediments in subduction zones, as subducted sediments have been shown to significantly influence arc magmatism. She first conducted an exhaustive survey of the literature to determine the best composition for starting material in the experiments. Previous experimental work by other researchers had used marine clays as starting materials, but this may be an unrealistic composition because it introduces chemical components not likely present by the time the sedimentary material has been subducted to moderate depths (fluids, salts). Mehgan therefore selected a metasedimentary rock (phyllite) that might better represent the composition of a rock in a subduction zone where it experiences dehydration and/or partial melting at P-T conditions relevant for influence arc magmatism. She compiled chemical analyses, obtained new chemical analyses (ICP-MS), and ran one piston cylinder experiment. She also participated in two weeks of field work in the North Cascades, Washington, to examine metamorphic rock in a magmatic arc and collect more samples for future experiments. (advisers: Whitney, Hirschmann)

Ben Siwiec (Western Washington University). Structural geology/tectonics. Field, microstructural, and magnetic study of the Bitterroot Shear zone, Montana, to study shear zone development related to lithospheric extension. This shear zone developed at the roof of an igneous complex, part of the Idaho batholith, that transferred heat and fluids to the upper part of the crust in early Tertiary.  Shear zones are the focus of fluid flow in the crust, and Ben's project was related to fabric development in the shear zone, to better understand the anisotropy of mylonites and the role of this anisotropy on fluid flow.  Ben studied the preferred orientation of minerals (feldspar, mica) and the anisotropy of magnetic susceptibility. His results show that the planar fabric is composite: increased fluid flow may occur at the intersection of the two planar fabrics.  Ben also conducted preliminary work on the anisotropy of magnetic susceptibility (AMS) and the change of AMS as a function of retrogression and cataclastic flow.  See Ben's website on his intern adventures at http://www.ac.wwu.edu/~ben. (adviser: Teyssier)

Brendon Stanton (Carleton College). Geophysics/rock deformation. Computer visualization of experimentally deformed and partially melted olivine samples to determine the structure and connectivity of melt pockets.  (adviser: Kohlstedt)

Monique Tsang (Haverford College). Geochemistry. Monique worked on a wide range of problems related to microbial growth in cultures purged with hydrogen gas, including trying to determine the mechanism by which H2 dissolves in solution. She investigated the conditions necessary to sustain growth of anaerobic thermophiles. The experiments involved introducing various pressures of hydrogen gas into a high-pressure vessel designed to withstand the high pressures of the deep sea. Gas analysis was conducted with a gas chromatography mass spectrometer. (adviser: Seyfried)

Shawn Wheelock (University of California - Santa Cruz). Hydrogeology. Shawn developed 2d models of aquifers beneath Nantucket Island to study the effect of sea level fluctuations on salt water intrusion into the aquifers. At present, the fresh water/salt water interface is lower than predicted by theory, suggesting the system is not in equilibrium. The motivation for this work was understanding an aquifer system needed for supply of fresh water for human consumption. (adviser: Person)