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Moses Coulee 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 trapp basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalts have occurred on continental scales (large igneous provinces) in prehistory, creating great plateaus and mountain ranges. Flood basalts have erupted at random intervals throughout history and are clear evidence that the Earth undergoes periods of enhanced activity rather than being in a uniform steady state. Image File history File links This is a lossless scalable vector image. ... Image File history File links Size of this preview: 721 × 600 pixelsFull resolution (1694 × 1409 pixel, file size: 670 KB, MIME type: image/jpeg) Photo taken from Three Devils Grade in mid-Moses Coulee in November, 2006. ... Image File history File links Size of this preview: 721 × 600 pixelsFull resolution (1694 × 1409 pixel, file size: 670 KB, MIME type: image/jpeg) Photo taken from Three Devils Grade in mid-Moses Coulee in November, 2006. ... Three Devils grade in Moses Coulee, Washington. ... The Columbia River Basalt Group encompasses portions of 3 states. ... This article is about volcanoes in geology. ... Basalt Basalt (IPA: ) is a common gray to black extrusive volcanic rock. ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ... Animated, colour-coded map showing the various continents. ... A large igneous province (LIP) is an extensive region of basalts resulting from flood basalt volcanism. ... It has been suggested that this article or section be merged with Prehistoric man. ... Image:NONE Monte Roraima In geology and earth science, a plateau, also called a high plateau or tableland, is an area of highland, usually consisting of relatively flat rural area. ... The Himalaya as seen from the International Space Station A mountain range is a group of mountains bordered by lowlands or separated from other mountain ranges by passes or rivers. ...

One explanation for flood basalts is that they are caused by the combination of continental rifting and its associated decompression melting in conjunction with a mantle plume also undergoing decompression melting, producing vast quantities of a tholeiitic basaltic magma. These lavas have a very low viscosity, which is why they 'flood' rather than form taller volcanoes. It has been suggested that this article or section be merged with Rift valley. ... Tholeiitic basalt is an igneous rock, a type of basalt. ... Magma is molten rock located beneath the surface of the Earth (or any other terrestrial planet), and which often collects in a magma chamber. ... Viscosity is a measure of the resistance of a fluid to deform under shear stress. ...

The Deccan Traps of central India, the Siberian Traps and the Columbia River Plateau of the western United States are three regions covered by prehistoric flood basalts. The two largest flood basalt events in historic time have been at Eldgjá and Lakagigar, both in Iceland. The maria on the Moon are another, even more extensive, example of a flood basalt. Flood basalts on the ocean floor produce the oceanic plateaus. The Deccan Traps is a large igneous province located in west-central India and is one of the largest volcanic features on Earth. ... The Siberian Traps (Russian: ) form a large igneous province in Siberia. ... The Columbia River Plateau is shown in green on this map. ... Eldgjá is a volcanic canyon in Iceland. ... The name Laki has more than one meaning:- A town called Laki in Plovdiv district in Bulgaria. ... The Lunar maria (singular: mare, IPA: //) are large, dark, basaltic plains on Earths Moon, formed by ancient volcanic eruptions. ... Apparent magnitude: up to -12. ... An oceanic plateau is an undersea large igneous province, the equivalent of continental flood basalts such as the Deccan Traps in India and the Snake River Plain in the Pacific Northwest of the United States. ...

The surface covered by one eruption can vary from around 200,000 km² (Karoo) to 1,500,000 km² (Siberia). The thickness can vary from 2000 m (Deccan) to 12,000 m (Lake Superior). However one must take into consideration the fact that these values are smaller than the original ones due to erosion. The Karoo and Farrar provinces together comprise a major flood basalt province of the which is found in both South Africa and Antartica. ... The Siberian Traps (Russian: ) form a large igneous province in Siberia. ... The Deccan Traps is a large igneous province located in west-central India and is one of the largest volcanic features on Earth. ... Lake Superior, bounded by Ontario and Minnesota to the north and Wisconsin and Michigan to the south, is the largest of North Americas Great Lakes. ...

Flood basalts originate in between 100 and 400 km depth in the asthenosphere. To obtain a partial fusion as large as that of the traps, effusing huge quantities of lava, it is necessary to have a large heat input. Such a fusion can take place near a hotspot, resulting in a mixture of magma from the depths of the hotspot and of superficial magma produced by a mantle plume. Earth cutaway from core to exosphere. ... In geology, a hotspot is a location on the Earths surface that has experienced active volcanism for a long period of time. ... A lava lamp illustrates the basic concept of a mantle plume. ...

Petrography

Ethiopian Highlands basalt

Flood basalts have tholeiite and olivine compositions (according to the classification of Yoder and Tilley). The composition of the basalts from the Paraná is fairly typical of that of flood basalts; it contains phenocrysts occupying around 25% of the volume of rock, trapped in volcanic glass. These phenocrysts are pyroxenes (augite and pigeonite), plagioclases, opaque crystals such as titanomagnetite or ilmenite, and occasionally some olivine. Sometimes more differentiated volcanic products such andesites, dacites and rhyodacites have been observed, but only in small quantities at the top of former magma chambers. Image File history File links Download high resolution version (2848x2136, 3012 KB) by Giustino modified by User:Andro96 Taken with a Fujifilm FinePix E550 on August 26, 2005 http://flickr. ... Image File history File links Download high resolution version (2848x2136, 3012 KB) by Giustino modified by User:Andro96 Taken with a Fujifilm FinePix E550 on August 26, 2005 http://flickr. ... Ethiopian Highlands with Ras Dashan in the background. ... The Pyroxenes are a group of important rock-forming silicate minerals found in many igneous and metamorphic rocks. ... Augite is a single chain inosilicate mineral described chemically as (Ca,Mg,Fe)SiO3 or calcium magnesium iron silicate. ... This page meets Wikipedias criteria for speedy deletion. ... Lunar Ferroan Anorthosite #60025 (Plagioclase Feldspar). ... Ilmenite is a weakly magnetic iron-black or steel-gray mineral found in metamorphic and igneous rocks. ... A sample of andesite (dark groundmass) with amygdaloidal vesicules filled with zeolite. ... Gray, red, black, altered white/tan, flow-banded pumice dacite poop Dacite (IPA: ) is a high-silica igneous, volcanic rock. ... BOOOOOOOOYAAAAAAAA!!!!!!!!!!! ...

Structures

Subaerial flood basalts can be of two kinds :

• with a smooth or twisted surface : very compact surface; vesicles and gas bubbles are rare. Degassing was easy (magma maintained at a high temperature and more fluid in a chamber of a size such that confining pressures did not confine gases to the melt before expulsion). Such lava flows may form underground rivers; when degassing fractures and conduits are present, very large flows may reach surface.
• with a chaotic surface : the basalt flood is very rich in bubbles of gas, with an irregular, fragmental surface. Degassing was difficult (less fuild magma expelled from a rift with no chance of progressive expansion in a hot chamber; the degassing took place closer to the surface where the flow forms a crust which cracks under the pressure of the gases in the flow itself and during more rapid cooling).

In the Massif Central in Auvergne, France, there is a good example of chaotic basalt floods, produced by eruptions from Puys de la Vache and Puy de Lassolas. France, viewed from the NASA Shuttle Topography Radar Mission. ... History Auvergne was also historically a province of France, deriving its name from Averni, a Gallic tribe who once occupied the area. ...

At depth, flows can crystallise more slowly, producing columnar jointing. Columnar jointed basalt in Turkey Columnar jointing in the basalt of the Giants Causeway in Ireland A joint is a generally planar fracture formed in a rock as a result of extensional stress. ...

Geochemistry

Geochemical analysis of the major oxides reveals a composition close to that of mid-ocean ridge basalts (MORB) but also close to that of ocean island basalts (OIB). These are in fact tholeiites with a silicon dioxide percentage close to 50%. Tholeiite (or Tholeiitic basalt) is a type of basalt rock that is olivine-poor, and dominated by clinopyroxene, plagioclase, and iron ore. ... R-phrases R42 R43 R49 S-phrases S22 S36 S37 S45 S53 Flash point non-flammable Supplementary data page Structure and properties n, εr, etc. ...

Two kinds of basaltic floods basalts can be distinguished :

• those rich in P₂O₅ and in TiO₂, called LPT
• those rich in P₂O₅ and in TiO₂, called HPT

The isotopic ratios ⁸⁷Sr/⁸⁶Sr and ²⁰⁶Pb/²⁰⁴Pb are different from that observed in general, which shows that the basalt flood magma was contaminated as it passed through the continental crust. It is this contamination that explains the difference between the two kinds of basalt mentioned above. The LPT type has an excess of elements from the crust such as potassium and strontium.

The content in incompatible elements of basaltic floods is lower than that of ocean island basalts, but higher than that of mid-ocean ridge basalts. Incompatible element is a term used in petrology and geochemistry. ...

Other occurrences and implications

• Flood basalt volcanism has been implicated (along with the impact of large asteroids and/or comets, as well as disease and long-term climate changes) in major mass extinction events in the past.

Main article: Geology of Venus#Volcanoes

• Basalt floods on the planet Venus are even larger than those on earth. Their study may help understand the mechanisms responsible for these major geological events.

An extinction event (also extinction-level event, ELE) is a period in time when a large number of species die out. ... A global view of Venus made from a mosaic of radar images from the Magellan spacecraft, centred at 90 degrees longitude. ... Adjectives: Venusian or (rarely) Cytherean Atmosphere Surface pressure: 9. ...

List of volcanic flood basalts

All major continental flood basalts (also known as traps) and oceanic plateaus, together forming a listing of large igneous provinces, which is provided below. The listing ranges from the smallest Columbia flood basalts to the largest, although not yet well characterized remnants of a possible trap in eastern Siberia^[1]: A large igneous province (LIP) is an extensive region of basalts resulting from flood basalt volcanism. ...

1. The Columbia-Snake River flood basalts (see Columbia River Basalt Group)
2. The Ethiopian and Yemen traps in the Ethiopian Highlands
3. The Brito-Arctic province
4. The Deccan Traps (India) 65 million years ago (end of Cretaceous Period)
5. The Madagascar and Caribbean Provinces
6. The Kerguelen Plateau
7. The Ontong-Java Plateau
8. The Paraná and Etendeka traps (Brazil-Namibia)
9. The Karoo and Ferrar provinces (South Africa-Antarctica)
10. The Central Atlantic Magmatic Province
11. The Siberian Traps (Russia) 251 million years ago (end of Permian)
12. The Emeishan (western China)
13. The Viluy traps
14. Pre-Devonian traps

The Columbia River Basalt Group encompasses portions of 3 states. ... The Arabian-Nubian Shield (ANS) is an exposure of Precambrian crystalline rocks exposed on the flanks of the Red Sea. ... Ethiopian Highlands with Ras Dashan in the background. ... The Brito-Arctic province (also known as the North Atlantic Tertiary Volcanic Province) is a major flood basalt province of the North Atlantic Ocean. ... The Deccan Traps is a large igneous province located in west-central India and is one of the largest volcanic features on Earth. ... The Madagascar and Caribbean Provinces consist of a major flood basalt, which created this large igneous province. ... The Kerguelen Plateau is an underwater volcanic ridge—the largest in the Indian Ocean, and one of the largest in the world. ... The Ontong Java Plateau is a huge oceanic plateau located in the Pacific Ocean, lying north of the Solomon Islands. ... The Paraná and Etendeka traps in Brazil, South America comprise a large igneous province which includes both the main Paraná traps as well as the smaller severed portions of the flood basalts at the Etendeka traps in Namibia and Angola. ... The Karoo and Farrar provinces together comprise a major flood basalt province of the which is found in both South Africa and Antartica. ... CAMP, or the Central Atlantic Magmatic Province, was formed during the largest known volcanic event in Earth history. ... The Siberian Traps (Russian: ) form a large igneous province in Siberia. ...

See also

• Basalt
• Large igneous province
• Oceanic plateau
• Supervolcano

Basalt Basalt (IPA: ) is a common gray to black extrusive volcanic rock. ... A large igneous province (LIP) is an extensive region of basalts resulting from flood basalt volcanism. ... An oceanic plateau is an undersea large igneous province, the equivalent of continental flood basalts such as the Deccan Traps in India and the Snake River Plain in the Pacific Northwest of the United States. ... A supervolcano refers to a volcano that produces the largest and most voluminous kinds of eruption on Earth. ...

References