Washington's diverse and spectacular geology is highlighted in its State and National Parks. The geology includes a remarkably wide range of features, such as the features carved by the Missoula ice age floods that swept across eastern Washington and down the Columbia River Gorge. Washington is renowned for active stratovolcanos in the Cascade Range, characterized by widespread flood basalt in the Columbia Basin, and home to extensive glacial features in the Puget Lowland. Older, accreted terrains and metamorphic rocks are present in the North Cascades and Okanogan Highlands.
Washington’s parks are a great place to study the geologic and structural setting of western North America. To the southeast, in Oregon and Nevada, extensional features predominate as reflected by basin-and-range terrain. To the east, the Rocky Mountains influence the geology of Idaho. To the north, western British Columbia is characterized by a massive coastal crystalline belt and remnants of the geologic continent Wrangellia. All of these major crustal features of the adjacent regions terminate in Washington, therefore the state has been subject to continental collisions, metamorphism, intrusion of igneous rocks, volcanism, mountain-building episodes, erosion, and massive flooding events. This diversity has a strong influence on soil productivity, location of mineral deposits, scenic grandeur, and even the climate. To read more about Washington's fascinating geology, click here.
Dry Falls State Park, Grant County, Washington. The Dry Falls were created by Ice Age floods.
The state's uniqueness is further enhanced by two major geologic conditions. First, Washington is impacted by crustal tectonics as the oceanic Juan de Fuca plate is being forced under the North American continent through a process called subduction (see more on the subduction zone and earthquakes in Washington). Second, the Columbia Basin in Washington and adjacent Oregon was subjected to one of the greatest outpourings of basalt known in the geologic record.
Washington's geology and parks are highly diverse. The easiest way to understand Washington's complex geology is to visit its great parks. Both State and National Parks Services have used DNR geology data to compile maps and informational materials for their visitors. Additionally, the Division of Geology and Earth Resources has published various roadside geology and field trip guides, including those for Mount Rainier and Mount St. Helens.