Professor and Fellow of the Cooperative Institute for Research in
Environmental Sciences (CIRES), University of Colorado, Boulder
Department of Geological Sciences
Wednesday, February 5, 2014
3:45 p.m. – 5:00 p.m.
54-915, Green Building Lecture Room
Hosted by Tim Cronin
Mantle Dynamics, Isostasy, and Surface Topography
Abstract: We all agree that the earth is a dynamic planet. Without dynamic processes to elevate terrain, erosion would destroy all subaerial topography, and sediment would bury all submarine topography. Once we had a useful concept called “dynamic topography,” but now it is merely a slogan. For example, numerous authors agree that southern Africa, roughly 1000 m high, exemplifies “dynamic topography,” but if some claim < 300 m and others >1200 km, do they really agree? I contend that most long wavelength topography is isostatically compensated, as Airy and Pratt understood this in the mid-19th Century. Dynamic stresses can account for ~300 m; Tibet stands 5000 m high. Mantle flow beneath mountain belts may profoundly affect the structural and/or thermal history of such belts, but the stresses associated with that flow support a play a negligible amount (300 m) of high terrain. Mantle dynamics creates high terrain by moving crust together and thickening it, by removing mantle lithosphere and replacing it with hotter asthenosphere, by injecting the athenosphere with hotter material upwelled from below, etc., in all cases in a state that is nearly (±300 m) in isostatic equilibrium. Amen.
A reception in Building 54, Room 923 precedes the talk.
All are welcome.
If you have any questions regarding the lecture, please contact Jennifer DiNisco at 617.253.2127 or jdinisco [at] mit [dot] edu. Reservations not required.
Sponsored by the Department of Earth, Atmospheric and Planetary Science, MIT.