Skip to main content
U.S. flag

An official website of the United States government

Pacific northwest tectonic setting

Detailed Description

Subduction in Cascadia has been underway for about 35 million years. It has produced a crustal architecture known from subduction zones around the world: an accretionary prism, extending from the deformation front into the continental shelf; a fore-arc region; a volcanic arc; and a back-arc region. These features are developed within a pre-existing continental framework, are modified by motion along the continental margin, and are overprinted by other plate boundary regimes as the extent of the subduction zone changes through time.