2008 Joint Meeting of The Geological Society of America, Soil Science Society of America, American Society of Agronomy, Crop Science Society of America, Gulf Coast Association of Geological Societies with the Gulf Coast Section of SEPM

Paper No. 5
Presentation Time: 2:55 PM

Effects of the Yellowstone Hotspot and Mantle Plume on the Western U.S

SMITH, Robert1, PUSKAS, Christine1, FARRELL, Jamie1, CHANG, Wulung1, STEINBERGER, Bernhard2 and O?CONNELL, Richard3, (1)Department of Geology and Geophysics, University of Utah, Salt Lake City, UT 84112, (2)Helmholtz Centre Potsdam, GFZ, Potsdam, 14473, Germany, (3)Department of Earth and Planetary Sciences, Harvard University, Cambridge, MA 02138, r.smith@earth.utah.edu

The Yellowstone hotspot resulted from interaction of a mantle plume with the overriding North America plate highly modifying the lithosphere by magmo-tectonic processes and producing the 16 Ma Yellowstone-Snake River Plain (YSRP) volcanic system. The accessibility of the YSRP has allowed large-scale geophysical experiments to seismically image the hotspot and to evaluate its kinematics and dynamic properties using geodetic measurements. Tomography reveals a Yellowstone upper-crustal magma body with 8-15% melt that is fed by an upper-mantle plume extending from 80 km to 650 km deep and tilting 60º west. Contemporary deformation of the Yellowstone caldera is dominated by SW-extension at up to ~3 mm/yr, a fourth of the total Basin-Range opening rate, but with superimposed volcanic uplift and subsidence at decade scales, averaging ~2 cm/yr. However unprecedented caldera uplift from 2004-2008 at up to 7 cm/yr was modeled as magmatic recharge of a 10-km deep sill. Mantle convection models reveal eastward flow beneath Yellowstone at relatively high rates of 5 cm/yr and opposite in direction to the overriding N. American Plate. Interaction of the eastward mantle-flow deflects the plume producing its westward tilt, i.e. "caught in the mantle wind”. Excess gravitational potential of the Yellowstone swell driving by buoyancy of the mantle plume provides excess potential energy that drives the YSRP lithosphere "downhill" in a SW direction. This motion then becomes part of the large-scale clockwise rotational pattern of tectonic elements of the western U.S. interior. Dynamic models reveals that low-density upper-mantle correlates with the thinned crust of the Basin-Range and with high-stresses from buoyancy caused by high surrounding topography and the Yellowstone swell.