NationMaster - Encyclopedia: Columbia River Basalt Group

The Columbia River Basalt Group is a large igneous province that lies across parts of the states of Washington, Oregon, and Idaho in the United States of America. During late Miocene and early Pliocene times, one of the largest flood basalts ever to appear on the earth's surface engulfed about 163,700 km² (63,000 mile²) of the Pacific Northwest, forming a large igneous province with an estimated volume of 174,300 km3. Eruptions were most vigorous from 17—14 million years ago, when over 99% of the basalt was released. Less extensive eruptions continued from 14—6 million years ago. ^[1] Image File history File links Download high resolution version (455x700, 27 KB)USGS map of volcanic areas in US Pacific Northwest File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... Image File history File links Download high resolution version (455x700, 27 KB)USGS map of volcanic areas in US Pacific Northwest File history Legend: (cur) = this is the current file, (del) = delete this old version, (rev) = revert to this old version. ... A large igneous province (LIP) is an extensive region of basalts resulting from flood basalt volcanism. ... Official language(s) None Capital Olympia Largest city Seattle Area Ranked 18th - Total 71,342 sq mi (184,824 kmÂ²) - Width 240 miles (385 km) - Length 360 miles (580 km) - % water 6. ... Official language(s) None Capital Salem Largest city Portland Area Ranked 9th - Total 98,466 sq mi (255,026 kmÂ²) - Width 260 miles (420 km) - Length 360 miles (580 km) - % water 2. ... This article or section does not cite its references or sources. ... The Miocene epoch is a period of time that extends from about 23 to 5. ... The Pliocene epoch (spelled Pleiocene in some older texts) is the period in the geologic timescale that extends from 5. ... A flood basalt is a giant volcanic eruption that coats large stretches of land with basalt lava. ... Earth (IPA: , often referred to as the Earth, Terra, the World or Planet Earth) is the third planet in the solar system in terms of distance from the Sun, and the fifth largest. ... A large igneous province (LIP) is an extensive region of basalts resulting from flood basalt volcanism. ...

These lava flows have been extensively exposed by the errosion resulting from the Missoula Floods, which laid bare many layers of the basalt flows at Wallula Gap, the lower Palouse River, the Columbia River Gorge and throughout the Channeled Scablands. Glacial Lake Columbia (west) and Glacial Lake Missoula (east) are shown south of Cordilleran Ice Sheet. ... A river that runs from Northwest Idaho to the Snake River in southest Washington. ... The Columbia River Gorge is a spectacular canyon of the Columbia River in the Pacific Northwest of the United States. ... DrumHeller Channels The Channeled Scablands are unique geological erosion features in the U.S. state of Washington. ...

Formation of the Columbia River Basalt Group

Over a period of perhaps 10 to 15 million years lava flow after lava flow poured out, eventually accumulating to a thickness of more than 1.8 km (6,000 feet). As the molten rock came to the surface, the earth's crust gradually sank into the space left by the rising lava. The subsidence of the crust produced a large, slightly depressed lava plain now known as the Columbia Basin or Columbia River Plateau. The ancient Columbia River was forced into its present course by the northwesterly advancing lava. The lava, as it flowed over the area, first filled the stream valleys, forming dams that in turn caused impoundments or lakes. In these ancient lake beds are found fossil leaf impressions, petrified wood, fossil insects, and bones of vertebrate animals. ^[2]^[3] ^[4]^[5] The Washington towns of Spokane, Vantage, Yakima and Pasco, and the Oregon town of Pendleton, lie on the Columbia River Plateau. ... Columbia River Gorge, Washington or North side The Columbia River (French: fleuve Columbia) is a river situated in British Columbia and the Pacific Northwest of the United States. ... An ammonite fossil Eocene fossil fish of the genus Knightia Petrified wood fossil formed through permineralization. ... Petrified log at the Petrified Forest National Park A petrified tree from California Petrified wood is a type of fossil, in which the tissues of a dead plant are replaced with minerals (most often a silicate, such as quartz). ...

Catastrophic beginnings

Prior to 17 million years ago, the Western Cascade Stratovolcanoes erupted with periodic regularity for over 20 million years, even as they do today. An abrupt transition to shield volcanic flooding occurred in the mid-Miocene. It has been postulated taht the transition was triggered by impact of a larger meteorite in southeast Oregon, creating a crater 160 km (100 miles) in diameter. The upwelling of lava changed the volcanic discharge regime for the Northwest, resulting in millions of years of flood basalt discharges. ^[5] A river that runs from Northwest Idaho to the Snake River in southest Washington. ... Mount Adams in Washington state The Cascade Range is a mountainous region famous for its chain of tall volcanos called the High Cascades that run north-south along the west coast of North America from British Columbia to the Shasta Cascade area of northern California. ... Stratovolcano Mount St. ... Shield volcano Mauna Kea, a shield volcano, on the Island of Hawaiâ€˜i with a light dusting of snow. ... The Miocene epoch is a period of time that extends from about 23 to 5. ... A meteorite is an extraterrestrial body that survives its impact with the Earths surface without being destroyed. ...

Although small when compared with the 600 km by 450 km across Shiva crater, which led to the similar Deccan Traps the phenomena is analogous. The Deccan Traps igneous province is 2,000 m thick and cover an area of 500,000 km² while the Columbia River Basalt Group is 1,800 km deep and covers an area of 160,000 km². The Oregon event was small enough that it did not result in major extinctions like those from the Shiva crater, which produced the Cretaceous-Tertiary extinction event; none-the-less the event had major regional impacts.^[1] The Shiva Crater is located in the Indian Ocean west of India. ... The Deccan Traps is a large igneous province located in west-central India and is one of the largest volcanic features on Earth. ... Badlands near Drumheller, Alberta where erosion has exposed the KT boundary. ...

The flows can be devided into major categories: The Grand Ronde Basalt, the Wanapum Basalt, and the Saddle Mountains Basalt. The ages of the various lava flows have been dated by radiometric dating—particularly through measurement of the ratios of isotopes of potassium to argon.^[1]

Imnaha Basalt

The oldest of the flows, from 17.4 million to 17.0 million years ago, is the Imnaha Basalt. The Imnaha flows welled up across northeastern Oregon. Although estimates are that this amounts to about 10% of the total flows, they have been buried under more recent flows, and are visible in few locations.^[5]

Grand Ronde Basalt

The next oldest of the flows, from 17 million to 15.6 million years ago, make up the Grand Ronde Basalt. Units (flow zones) within the Grand Ronde Basalt include the Meyer Ridge and the Sentinel Bluffs units. Geologists estimate that the Grand Ronde Basalt comprises about 85% of the total flow volume. It is characterized by a number of dikes called the Chief Joseph Dike Swarm through which the lava upwelling occurred (estimates range to up to 20,000 such dikes). Many of the dikes were fissures 5-10 meters wide, allowing for huge quantities of magma upwelling. Much of the lava flowed north into Washington as well as down the Columbia River channel to the Pacific Ocean; the tremendous flows created the Columbia River Plateau. The weight of this flow caused central Washington to sink, creating the broad Columbia Basin in Washington.^[1]^[5] Columbia River Gorge, Washington or North side The Columbia River (French: fleuve Columbia) is a river situated in British Columbia and the Pacific Northwest of the United States. ... The Washington towns of Spokane, Vantage, Yakima and Pasco, and the Oregon town of Pendleton, lie on the Columbia River Plateau. ...

Wanapum Basalt

The Wanapum Basalt is comprised of the Eckler Mountain Member (15.6 million years ago), the Frenchmen Springs Member (15.5 million years ago), the Roza Member (14.9 million years ago) and the Priest Rapids Member (14.5 million years ago).^[1]^[6]

Saddle Mountains Basalt

The Saddle Mountain Basalt is comprised of the Umatilla Member flows, the Wilbur Creek Member flows, the Asotin Member flows (13 million years ago), the Weissenfels Ridge Member flows, the Esquatzel Member flows, the Elephant Mountain Member flows (10.5 million years ago), the Bujford Member flows, the Ice Harbor Member flows (8.5 million years ago) and the Lower Monumental Member flows (6 million years ago).^[1]

See also

The Grand Coulee The Grand Coulee is an ancient river bed in the U.S. state of Washington. ... DrumHeller Channels The Channeled Scablands are unique geological erosion features in the U.S. state of Washington. ... The Interior Plateau comprises a large region of central British Columbia, and lies between the Cariboo and Monashee Mountains on the east, and the Hazelton Mountains, Coast Mountains and Cascade Range on the west. ...

External links

References

^ ^a ^b ^c ^d ^e ^f Carson, Robert J. and Pogue, Kevin R. (1996). Flood Basalts and Glacier Floods:Roadside Geology of Parts of Walla Walla, Franklin, and Columbia Counties, Washington. Washington State Department of Natural Resources (Washington Division of Geology and Earth Resources Information Circular 90). ISBN none.
^ Alt, David. Glacial Lake Missoula & its Humongous Floods. Mountain Press Publishing Company. ISBN 0-87842-415-6.
^ Bjornstad, Bruce (2006). On the Trail of the Ice Age Floods: A Geological Guide to the Mid-Columbia Basin. Keokee Books; Sand Point, Idaho. ISBN 978-1-879628-27-4.
^ Portions of this article, including a figure, are adapted from works of the United States Government, which are in the public domain
^ ^a ^b ^c ^d Alt, David & Hyndman, Donald (1995). Northwest Exposures: a Geologic Story of the Northwest. Mountain Press Publishing Company. ISBN 0-87842-323-0.
^ Mueller, Marge & Ted (1997). Fire, Faults and Floods. University of Idaho Press, Moscow, Idaho. ISBN 0-89301-206-8.

A work of the United States Government is, as defined by United States copyright law, a work prepared by an officer or employee of the United States Government as part of that persons official duties. ... The public domain comprises the body of all creative works and other knowledge—writing, artwork, music, science, inventions, and others—in which no person or organization has any proprietary interest. ...

Exploring Ice Age Floods in the Pacific Northwest

| Glacial Lake Missoula | Missoula Floods | Channeled scablands | Grand Coulee | Dry Falls | Drumheller Channels | Columbia River Plateau | Wallula Gap | Touchet Formation | Lake Lewis | Columbia River Gorge | Columbia River Basalt Group | Palouse Falls | Sims Corner Eskers and Kames | Moses Coulee | Withrow Moraine The Pacific Northwest from space This page is about the region that includes parts of Canada and the US. For the US only region, see Northwestern United States The Pacific Northwest (abbreviated PNW, or PacNW) or Cascadia is a region in the northwest of North America. ... Glacial Lake Missoula was a prehistoric proglacial lake in western Montana that existed periodically at the end of the last ice age between 15,000 and 13,000 years ago. ... Glacial Lake Columbia (west) and Glacial Lake Missoula (east) are shown south of Cordilleran Ice Sheet. ... DrumHeller Channels The Channeled Scablands are unique geological erosion features in the U.S. state of Washington. ... The Grand Coulee The Grand Coulee is an ancient river bed in the U.S. state of Washington. ... In Central Washington at the opposite side of the Grand Coulee from the Columbia River resides a three and a half mile crescent shaped precipice known as Dry Falls. ... The Washington towns of Spokane, Vantage, Yakima and Pasco, and the Oregon town of Pendleton, lie on the Columbia River Plateau. ... The Columbia River Gorge is a spectacular canyon of the Columbia River in the Pacific Northwest of the United States. ... A Glacial erratic called Yeager Rock, Waterville Plateau, Washington, USA The Sims Corner Eskers and Kames National Natural Landmark includes excellent examples of Pleistocene ice stagnation landforms including numerous Glacial erratics terminal moraines, eskers and kames. ... The Withrow Moraine erratic on glacial till at the terminus of the Okanogan lobe. ...

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