![]() ![]() Parts of Rainier also sit upon three older formations of volcanic rocks and associated sediments: Fife's Peak (26 to 22 Ma), Stevens Ridge (26 Ma), and Ohanapecosh (36 to 28 Ma). Volcanoes were probably also fed by these magma bodies, but about 10 million years ago, the western margin of North America was uplifted and erosion stripped volcanic rocks overlying the granodiorite. Some of this magma solidified as the 18- to 14-million-year-old Tatoosh Granodiorite, which formed when large volumes of magma rose into the subsurface and slowly cooled. ![]() Before this, magmas both erupted and accumulated beneath the surface. The edifice of modern Mount Rainier assembled over the last half million years by the accumulation of hundreds individual lava flows, but an ancestral Mount Rainier stood in the same place from 1 to 2 million years ago. Mount Rainier is not the first volcano to have grown in its present location. Volcanism occurs at Mount Rainier and other Cascades arc volcanoes because of the subduction of the Juan de Fuca Plate off the western coast of North America. Mount Rainier is an active volcano of the Cascade Range in Washington State, 50-70 km (30-44 mi) southeast of the Seattle–Tacoma metropolitan area. Mount Rainier, Washington with flowers from Paradise, Mount Rainier National Park. ![]()
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