A hundred years ago this past morning, the San Andreas fault slipped: the Great San Francisco Earthquake of 1906. Go back a half a billion years: there’s no California. Paleoamerica ended at Utah, the Osmonds instead of the Grateful Dead.
Over the next 500 million years, Laurentia (the core of the North American continent) drifts northwards, rotates counter-clockwise, and sweeps up arcs of islands that fill out the rest of the future Western US.
The subduction zone’s migrated north of us, and drives the Cascadian volcanoes: Hood, Saint Helens, and Rainier. But we’re still on a plate boundary, the Pacific Plate grinding against North America instead of slipping under us. Geology and catastrophe defined the American West, even before people and California.
The paleographic maps of North America linked above were produced by Dr. Ron Blakey of Northern Arizona University [ via Centripetal Notion. ] See also: Doc Searls on living in a geologically active zone, and read Basin and Range: our understanding of plate tectonics is younger than Darwin, Einstein, and Bohr.
