Roadside Geology of Oregon (Roadside Geology Series)

Until about 200 million years ago, the western margin of North America lay to the east, along the present Idaho border, and a broad coastal plain spread westward into Oregon. The rest of the state was ocean floor. Then the continent began moving slowly westward away from Europe and the floor of the Pacific Ocean began sliding beneath the western edge. That is what created Oregon, and this book tells how it happened.