As a geomorphologist, I seek to understand how landscapes change through time and how environmental changes are reflected across a landscape. To address these questions, I utilize a variety of geochronological techniques, including exposure dating with cosmogenic nuclides (such as 10Be, 26Al, and 21Ne) and lichenometry, which allow me to study questions about landscape evolution, the timing of geologic events, and the rates at which geomorphic processes occur. Most of my field areas are glacial terrains, and many of my projects look at determining the timing of glacial events and how quickly glacial deposits have changed since they were deposited. My work involves a balance of field-based studies in alpine areas and Antarctica, laboratory analysis, and numerical modeling.
I am working on research projects in Antarctica, Peru, and the Sierra Nevada, CA. Each of these projects involves glacial geology and utilizing dating techniques to determine the timing of glaciations and the rates of geomorphic processes.
In Antarctica, I study the glacial history of the continent and Cenozoic climate change, and to study this I visit the ice-free areas of Antarctica that contain glacial deposits, which record previous episodes of glaciation. These ice-free areas are extremely cold and dry deserts that are very similar to the environmental conditions found on the surface of Mars and the Moon. . They also present an apparent contradiction to geomorphologists in that they show both signs of being active, dynamic landscapes undergoing change, but also show areas of preservation for millions of years with little to no change. Typical projects of mine in Antarctica utilize cosmogenic nuclides to date glacial deposits and determine rates of geomorphic processes that are active in that environment. Results from this work often show that glacial tills in Antarctica are often millions of years old, and are eroding at rates of 0.2 – 4 m/Myrs. On many of these projects I collaborate with Jaakko Putkonen (University of North Dakota) and Greg Balco (Berkeley Geochronology Center), and I have a project in development with Mark Salvatore (University of Michigan-Dearborn).
In Peru, I am working with Steve Wernke, an archaeologist at Vanderbilt University. Dr. Wernke is beginning an excavation at Mawchu Llacta, which is in the Colca Valley in southern Peru. Lichenometry is a technique that has often been applied to young glacier moraines, but has been used in only a few instances for archaeological sites. During field visits to Peru in 2010 and 2012, an undergraduate student came with me to find control sites for developing a growth curve for the lichen rhizocarpon sp. (in collaboration with Michael O’Neal – University of Delaware). The main application for this lichen growth curve is to determine the construction and abandonment age of buildings at the archaeological site Mawchu Llacta near the city of Tuti in southern Peru. Lichenometry provides a non-destructive method for determining the exposure age of surfaces, and in this case we are testing if the outside and inside walls of the buildings at the archaeological site yield different exposure ages corresponding to their construction and abandonment ages, respectively.Additionally, I am assisting this project by looking at the environmental history of the site when it was occupied, which overlaps with the time period commonly known as the little ice age. By finding and dating glacial moraines associated with this glacial expansion, I can directly provide temperature and precipitation information about the site during its occupation.
In the Sierra Nevada Mountains, CA, I am working on a project that explores how glacial moraines change through time. In collaboration with David Furbish (Vanderbilt) and Josh Roering (U. of Oregon), our recently funded grant (NSF Awards #1420831 and #140898) is aimed at clarifying the factors that contribute to “local” transport, where downslope sediment movement involves small particle motions controlled by local soil and land-surface conditions, versus “nonlocal” transport associated with soil slips, biotic disturbances (e.g., tree-throw), particle ravel following fire, etc., which can involve relatively rapid, long-distance sediment motions.