INTERRELATION OF CONTINENTAL RIFT FORMATION AND VOLCANISM IN THE BASIN AND RANGE PROVINCE

The Basin and Range region has been subject to ongoing extensional deformation since middle Miocene time, and several currently active volcanic fields are present within it and adjacent to it. Data on the locations and ages of individual volcanoes in the San Francisco, Coso, Southwest Nevada, and Springerville fields consistently show a strong tendency for newer volcanoes to be located further away from the center of the Basin and Range than preceding ones.This behavior is observed throughout Miocene time up to the present. This migration of volcanism over time strongly suggests that volcanism in the Basin and Range is primarily driven by the release of pressure on the asthenosphere caused by the gradual thining of the crust, and concentrates at the locations of greatest tension at the edges of the expanding Basin and Range region.