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The Columbia River Basalt Group (including the Steen and Picture Gorge basalts) extends over portions of four states. The Columbia River Basalt Group (CRBG) is the youngest, smallest and one of the best-preserved continental flood basalt provinces on Earth, covering over 210,000 km 2 (81,000 sq mi) mainly eastern Oregon and Washington, western Idaho, and part of northern Nevada. [1]
Columbia River Basin. Wallula Gap (/ w ə ˈ l uː l ə /) is a large water gap of the Columbia River in the Northwestern United States, in Southeastern Washington.It cuts through the Horse Heaven Hills basalt anticlines in the Columbia River Basin, just south of the confluence of the Walla Walla and Columbia rivers.
Moses Coulee in the US showing multiple flood basalt flows of the Columbia River Basalt Group. The upper basalt is Roza Member, while the lower canyon exposes Frenchmen Springs Member basalt A flood basalt (or plateau basalt [ 1 ] ) is the result of a giant volcanic eruption or series of eruptions that covers large stretches of land or the ...
With an average flow at the mouth of about 265,000 cu ft/s (7,500 m 3 /s), [4] the Columbia is the largest river by discharge flowing into the Pacific from the Americas [25] and is the fourth-largest by volume in the U.S. [4] The average flow where the river crosses the international border between Canada and the United States is 2,790 m 3 /s ...
The Columbia River Basalt Group consists of seven formations: The Steens Basalt, Imnaha Basalt, Grande Ronde Basalt, Picture Gorge Basalt, Prineville Basalt, Wanapum Basalt, and Saddle Mountains Basalt. Many of these formations are subdivided into formal and informal members and flows.
Over 170,000 km 3 (41,000 cu mi) of basaltic lava, known as the Columbia River Basalt Group, covers the western part of the province. These tremendous flows erupted between 17–6 million years ago. Most of the lava flooded out in the first 1.5 million years: an extraordinarily short time for such an outpouring of molten rock. [8]
The Channeled Scablands are a relatively barren and soil-free region of interconnected relict and dry flood channels, coulees and cataracts eroded into Palouse loess and the typically flat-lying basalt flows that remain after cataclysmic floods within the southeastern part of Washington state.
Also closely related in space and time is the eruption of the 16.6 Ma Steens Basalts, the initial and most voluminous phase of the Columbia River Basalt Group lava flows that blanket eastern Oregon and the entire southeastern quarter of Washington.