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9. Rift Volcanoes: aftermath of the Yellowstone hot spot

Exotic Terranes

After setting off the eruption of the Columbia River Basaltsee Unit 8, the Yellowstone hot spot remained stationary as North America drifted west. This movement left a trail of volcanoes that extends to the east, ending at the Yellowstone caldera, a giant dormant volcano in Yellowstone National Park, Wyoming. Back in Oregon, the arrival of the hot spot had caused the crust to break and stretch, riftingsee Plate Tectonics diagram apart to allow hundreds of volcanoes to break through and create a huge swath of volcanic rocks covering the southeast third of the state. These hot spot volcanoes range from 15 million to about 2 million years old and include everything from small cinder cones to calderas many miles across. The rifting caused the crust to break into large blocks separated by faults. Some blocks rose to form mountain ranges, while others sank to form basins; together they produced a landscape called the Basin and Range.

OGDC units: Miocene-Pliocene volcanic and volcaniclastic rocks and interbedded terrestrial sedimentary rocks of the High Lava Plains Volcanic Province and Oregon Idaho Graben; Kivett, Strawberry, and Northern Nevada Volcanics; Early Winema, Winema, Quaternary Winema, Harney Basin, Lake Owyhee, McDermitt, and Powder River Volcanic Fields

Age Range: 15 million to 2 million years ago
Rock Types: basalt, andesite, dacite, rhyolite, tuff, siltstone, sandstone
Did You Know? At least 790 individual volcanic vents have been mapped in the Rift Volcanoes.


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