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8. Columbia River Basalt: the Yellowstone hot spot arrives in a flood of fire

Exotic Terranes

Seventeen million years ago the Yellowstone hot spot, a plumesee Plate Tectonics diagram of very hot rock, rose from deep within the Earth beneath eastern Oregon, setting off a huge pulse of volcanic activity. The first eruptions were a series of gigantic lava floods erupted from great fissures near the Oregon-Idaho-Washington border. These lava flows are among the largest to have occurred anywhere on Earth. Some of these rapidly moving sheets of lava traveled as far as 400 miles from their vents to their far ends at Newport, Oregon. Individual flows cover as much as 10,000 square miles, equivalent to one tenth of the state, and many are over 100 feet thick. Most of this huge body of lava (originally covering half of the state) was erupted between 17 million and 15 million years ago, a very brief period in geologic history. Columbia River Basalt often cools to form stone columns, an iconic part of Oregon’s scenery.

OGDC units: Miocene Grande Ronde, Hunter Creek, Imnaha, Picture Gorge, Prineville, Saddle Mountains, Steens, Venator Ranch and Wanapum Basalts

Age Range: 17 to 6 million years ago
Rock Types: basalt
Did You Know? The largest individual Columbia River Basalt flows covered an area the size of the state of Maine.


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