By Whitney Harder
(Jan. 29, 2015) — Dave Moecher, University of Kentucky professor and chair of the Department of Earth and Environmental Sciences, has been awarded a $155,000 National Science Foundation (NSF) grant to understand how the Earth's crust produces magma, specifically, how unusually hot granites were formed 1 billion years ago.
The grant, a collaborative effort with Scott Samson and students at Syracuse University, will support two years of research from a UK graduate student, undergraduate student and at least one Lexington high school student, who will each work on a different component of the research. Undergraduate and high school students will not only work alongside the graduate student and Moecher, but will also have a hypothesis to test or problem to find the solution for.
Moecher, who has received two previous grants related to his research on the formation and evolution of the Earth's crust, will use this grant to prove the existence of 900-1,100 degrees Celsius granite magma in the crust, well above the average temperature of hot granites (700-800 degrees Celsius). Moecher says in the last decade, he and his team have identified a period in Earth's history, approximately 1 billion years ago, when there appears to be widespread production of this unusually hot granite magma.
Exposed in the Blue Ridge Mountains in Virginia, Moecher and his team have discovered what they think to be abnormally hot granites, produced when a large chunk of the North American crust was formed. Moecher says that chunk of crust underlies the eastern third of North America and is exposed in several places in the Appalachian Mountains, Adirondack Mountains, eastern Canadian Shield, and in drill holes that penetrate to “basement” rocks, otherwise known as the "crystalline rocks beneath the sedimentary rock layers one sees in road cuts driving around Kentucky."
Extremely hot granites require that conditions in the lower crust and mantle, where magma is generated, were hotter than usual 1 billion years ago, and were hotter across a very large area. One hypothesis for how the crust became so hot is the "lid" hypothesis. The lid theory proposes that the large expanse of existing crust kept a lid on the heat generated in the core and deep mantle, which is normally dissipated by continents breaking up and drifting apart (plate tectonics).
"However, to test the "lid" hypothesis, we must first prove that the purportedly "hot granites" were in fact hot. That is what we plan to prove with our new grant," said Moecher.