Tectonic Blow Ended Mountain Building, Fired Up Volcanoes

摘要

Fifty-five million years ago, Siletzia arrived on North American shores with nary a bump. But the 500-kilometer-wide chunk of drifting oceanic plate had far-reaching geologic effects across the continent's western third, according to a presentation at the meeting. New seismic imaging shows Siletzia throwing a monkey wrench into the gears of the plate tectonics machine and thus reshaping western North America. Before Siletzia arrived, things tectonic were humming along nicely. The Farallon oceanic plate was creeping northeastward and diving into the mantle beneath North America. But unlike most subducting plates, the Farallon plate wasn't diving very deeply.