40-17 million years ago The Cascade Mountains are formed. The Olympic Mountains appear as islands in the Pacific. 17-6 million years ago Floods of lava cover the Columbia Basin and destroy the Columbia River waterway. 6 million - 10,000 years ago Washington's Ice Age. Volcanos form in the Cascades and huge glaciers cover the mountains and Puget Sound.
Floods shape the southern part of the state.
11,000 B.P. People of the Clovis Culture inhabit the Northwest. 6,700 B.P. Mount Mazama erupts. 1741-43 Russian explorers reach Alaskan islands and coast and trade with native peoples for sea otter pelts. Juan Perez commands the first Spanish expedition to explore the Northwest Coast and sights the Olympic Mountains. Bruno de Hezeta lands on the Washington coast and claims the area for Spain.