Roadside Geology of Washington (Roadside Geology Series)

The geology of Washington is a story of islands--micro-continents--coming in from the sea. Two hundred million years ago most of Washington consisted of two large islands, each one a scrap of continent, lying somewhere in the vastness of the Pacific Ocean. One after the other they docked onto the North American continent, each adding its distinctive bit to the complex geologic and geographic mosaic of western North America.