Track of the Yellowstone hotspot: Young and ongoing geologic processes from the Snake River Plain to the Yellowstone Plateau and Tetons

Abstract

This fi eld trip highlights various stages in the evolution of the Snake River Plain– Yellowstone Plateau bimodal volcanic province, and associated faulting and uplift, also known as the track of the Yellowstone hotspot. The 16 Ma Yellowstone hotspot track is one of the few places on Earth where time-transgressive processes on continental crust can be observed in the volcanic and tectonic (faulting and uplift) record at the rate and direction predicted by plate motion. Recent interest in young and possible renewed volcanism at Yellowstone along with new discoveries and synthesis of previous studies, i.e., tomographic, deformation, bathymetric, and seismic surveys, provide a framework of evidence of plate motion over a mantle plume. This 3-day trip is organized to present an overview into volcanism and tectonism in this dynamically active region. Field trip stops will include the young basaltic Craters of the Moon, exposures of 12–4 Ma rhyolites and edges of their associated collapsed calderas on the Snake River Plain, and exposures of faults which show an age progression similar to the volcanic fi elds. An essential stop is Yellowstone National Park, where the last major caldera-forming event occurred 640,000 years ago and now is host to the world’s largest concentration of hydrothermal features (>10,000 hot springs and geysers). This trip presents a quick, intensive overview into volcanism and tectonism in this dynamically active region. Field stops are directly linked to conceptual models related to hotspot passage through this volcano-tectonic province. Features that may refl ect a tilted thermal mantle plume suggested in recent *lmorgan@usgs.gov, kpierce@usgs.gov, pshanks@usgs.gov Morgan, L.A., Pierce, K.L., and Shanks, W.C.P., 2008, Track of the Yellowstone hotspot: Young and ongoing geologic processes from the Snake River Plain to the Yellowstone Plateau and Tetons, in Raynolds, R.G., ed., Roaming the Rocky Mountains and Environs: Geological Field Trips: Geological Society of America Field Guide 10, p. XX–XX, doi: 10.1130/2007.fl d010(XX). For permission to copy, contact editing@geosociety.org. ©2008 The Geological Society of America. All rights reserved. 2 Morgan et al. FLD010-l.morgan 2nd pgs page 2