8051 Regents Drive
College Park, MD 20742
lsammon [at] umd [dot] edu
Though we live on Earth's crust, we understand relatively little about its properties. By mass, it only makes up 0.5% of Earth, but that is still 2x10²² kg of rock, or about half the mass of the Moon. We know some things about the continental crust, but we still do not understand it, how the interplay of its composition and structure might cause it to have distinct layers, or not.
I am quantifying what we do know about the composition of the continental crust and reconciling its chemical information with surface wave seismic data, starting with the lower crust of the United States. Because we cannot sample it or analyze the lower crust’s composition in situ (it is some twenty to forty kilometers beneath our feet), I am studying granulite xenoliths and massifs, and using the modeling software Perple_X to determine a range of physical properties based on their chemical compositions.
The combined suite of geochemical and geophysical data will inform us, in part, of the deep crust's formation, differentiation, composition, and structure, which in turn can help us better understand plate tectonics, earthquakes, volcanoes, and the distribution of heat producing elements [potassium (K), thorium (Th), and uranium (U)].
Sammon, L.G., Gao, C., McDonough, W.M. (2020) Lower Crustal Composition in the Southwestern United States. Journal of Geophysical Research: Solid Earth. 125 DOI: 10.1029/2019JB019011