Flood basalt

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Flood basalt

A flood basalt or trap basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean

Ocean

An ocean is a major body of Seawater, and a principal component of the hydrosphere. Approximately 71% of the Earth's surface is covered by ocean, a World Ocean that is customarily divided into several principal oceans and smaller seas....
floor with basalt

Basalt

Basalt is a common extrusive volcanic rock. It is usually gray to black and fine-grained due to rapid cooling of lava at the surface of a planet....
lava

Lava

Lava is molten Rock expelled by a volcano during an eruption. When first expelled from a volcanic vent, it is a liquid at temperatures from 700 ?C to 1,200 ?C ....
. Flood basalts have occurred on continent

Continent

A continent is one of several large landmasses on Earth. They are generally identified by convention rather than any strict criteria, with seven regions commonly regarded as continents ? they are : Asia, Africa, North America, South America, Antarctica, Europe, and Australia ....
al scales (large igneous province

Large igneous province

Prehistory

Prehistory is a term often used to describe the period before Recorded history. Paul Tournal originally coined the term Pr?-historique in describing the finds he had made in the caves of southern France....
, creating great plateau

Plateau

In geology and earth science, a plateau, also called a high plateau or tableland, is an area of highland , usually consisting of relatively flat terrain....
s and mountain range

Mountain range

A mountain range is a chain of mountains bordered by highlands or separated from other mountains by mountain pass or valleys. Individual mountains within the same mountain range do not necessarily have the same geology, though they often do; they may be a mix of different orogeny, for example volcanoes, uplifted mountains or Fold mountains...
s. Flood basalts have erupted at random intervals throughout geological history

Geological history

Geological history describes geological events that account for the stratigraphy, petrology and structure seen in rocks or earth materials.See geologic timescale....
and are clear evidence that the Earth

Earth

Earth is the third planet from the Sun. Earth is the largest of the terrestrial planets in the Solar System in diameter, mass and density. It is also referred to as the World and Wiktionary:Terra.Note that by International Astronomical Union convention, the term "Terra" is used for naming extensive land masses, rather...
undergoes periods of enhanced activity rather than being in a uniform steady state.

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

Mantle plume

A mantle plume is an upwelling of abnormally hot rock within the Earth's mantle . As the heads of mantle plumes can partly melt when they reach shallow depths, they are thought to be the cause of volcano centers known as Hotspot and probably also to have caused flood basalts....
also undergoing decompression melting, producing vast quantities of a tholeiitic basaltic magma

Magma

Magma is molten Rock that is found beneath the surface of the Earth, and may also exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and gas bubbles....
.

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Encyclopedia

A flood basalt or trap basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean

Ocean

Basalt

Basalt is a common extrusive volcanic rock. It is usually gray to black and fine-grained due to rapid cooling of lava at the surface of a planet....
lava

Lava

Continent

Large igneous province

Prehistory

Plateau

In geology and earth science, a plateau, also called a high plateau or tableland, is an area of highland , usually consisting of relatively flat terrain....
s and mountain range

Mountain range

Geological history

Earth

Mantle plume

Magma

Viscosity

Viscosity is a measure of the Drag of a fluid which is being deformed by either shear stress or extensional stress. In everyday terms , viscosity is "thickness"....
, which is why they 'flood' rather than form taller volcano

Volcano

A volcano is an opening, or rupture, in a planet's surface or Crust , which allows hot, molten rock, ash, and gases to escape from below the surface....
es.

The Deccan Traps

Deccan Traps

The Deccan Traps are a large igneous province located on the Deccan Plateau of west-central India and one of the largest volcanic features on Earth....
of central India

India

India, officially the Republic of India , is a country in South Asia. It is the List of countries and outlying territories by total area country by geographical area, the List of countries by population country, and the most populous liberal democracy in the world....
, the Siberian Traps

Siberian Traps

File:Extent_of_Siberian_traps_german.pngThe Siberian Traps form a large igneous province in Siberia. The massive eruptive event spans the Permian-Triassic boundary, about 251 to 250 million years ago, and was essentially coincident with the Permian?Triassic extinction event in what was one of the largest known volcano events of the l...
and the Columbia River Plateau

Columbia River Plateau

The Columbia River Plateau is a geology and geography region that lies across parts of the U.S. states of Washington, Oregon, and Idaho. It is a wide flood basalt plateau between the Cascade Mountains and Rocky Mountains, cut through by the Columbia River....
of western North America

North America

North America is the northern continent of the Americas, situated in the Earth's northern hemisphere and almost totally in the western hemisphere....
are three regions covered by prehistoric flood basalts. The two largest flood basalt events in historic time have been at Eldgjá

Eldgjá

Eldgj? is a volcanic canyon in Iceland. Eldgj? and the nearby Laki craters are part of the same volcanic system as Katla in the south of the country....
and Lakagigar, both in Iceland

Iceland

Iceland, officially the Republic of Iceland , is an island country located in the North Atlantic Ocean between mainland Europe and Greenland....
. The maria

Lunar mare

The lunar maria are large, dark, basaltic plains on Earth's Moon, formed by ancient volcanic eruptions. They were dubbed maria, Latin for "seas", by early astronomers who mistook them for actual seas....
on the Moon

Moon

The Moon is Earth's only natural satellite and the List of natural satellites by diameter satellite in the Solar System. The average centre-to-centre distance from the Earth to the Moon is km, about thirty times the diameter of the Earth....
are additional, even more extensive, flood basalts. Flood basalts on the ocean floor produce oceanic plateau

Oceanic plateau

An oceanic plateau is a large, relatively flat submarine region that rises well above the level of the ambient seabed. While many oceanic plateaus are composed of continental crust, and often form a step interrupting the continental slope, some plateaus are undersea remnants of large igneous provinces....
s.

The surface covered by one eruption can vary from around 200,000 km² (Karoo

Karoo-Ferrar

The Karoo and Farrar provinces together comprise a major flood basalt province, most of which is found in South Africa and Antarctica, although parts extend into South America, India, Australia and New Zealand....
) to 1,500,000 km² (Siberian Traps). The thickness can vary from 2000 metres (Deccan Traps) to 12,000 m (Lake Superior

Lake Superior

Lake Superior is the largest of the five Great Lakes of North America. It is bounded to the north by Ontario, Canada and Minnesota, United States, and to the south by the U.S....
). These are smaller than the original volume

Volume

The volume of any solid, liquid, plasma, vacuum or theoretical object is how much three-dimensional space it occupies, often quantified numerically....
s due to erosion

Erosion

For morphological image processing operations, see Erosion 'For use of in dermatopathology, see Erosion Erosion is the removal of solids in the natural environment....
.

Flood basalts originate at between 100 and 400 km depth, in the asthenosphere

Asthenosphere

The asthenosphere is the mechanically weak ductily-deforming region of the upper Mantle of the Earth. It lies below the lithosphere, at depths between 100 and 200 km below the surface, but perhaps extending as deep as 400 km ....
. To obtain a partial fusion as large as that of the traps, expelling huge quantities of lava, it is necessary to have a large heat

Heat

In physics and thermodynamics, heat is any transfer of energy from one body or thermodynamic system to another due to a difference in temperature....
input. Such fusion

Fusion

Fusion can refer to combining two or more distinct things*Cell fusion*Melting, a chemistry term for a solid undergoing a phase change into a liquid...
can take place near a hotspot

Hotspot (geology)

In geology, a hotspot is a location on the Earth's surface that has experienced active volcano for a long period of time. J. Tuzo Wilson came up with the idea in 1963 that volcanic chains like the Hawaiian Islands result from the slow movement of a tectonic plate across a "fixed" hot spot deep beneath the surface of the planet....
, resulting in a mixture of magma from the depths of the hotspot with superficial magma produced by a mantle plume.

Petrography

Flood basalts have tholeiite and olivine

Olivine

The mineral olivine is a magnesium iron Silicate minerals with the formula 2siliconoxygen4. It is one of the most common minerals on Earth, and has also been identified in meteorites and on the Moon, Mars, and comet Wild 2....
compositions (according to the classification of Yoder

Yoder

Yoder is a surname originating in the Canton of Berne in Switzerland. The surname is a shortened version of St. Theodorus, the first Roman Catholic Bishop of Sion in present day Martigny, Switzerland....
and Tilley

Tilley

Tilley may refer to:* Tilley, Alberta, a village in Canada* Tilley, Shropshire, a village in England* Tilley , people with the surname Tilley...
). The composition of the basalts from the Paraná

Paraná

Paran? may refer to*Paran? in Brazil*Paran? River in Brazil, Paraguay, and Argentina*Paran? River in Brazil*Paran?, Buenos Aires, a settlement in Escobar Partido, province of Buenos Aires, Argentina...
is fairly typical of that of flood basalts; it contains phenocryst

Phenocryst

A phenocryst is a relatively large and usually conspicuous crystal distinctly larger than the grains of the rock Matrix of a porphyritic igneous rock....
s occupying around 25% of the volume of rock, trapped in volcanic glass

Volcanic glass

Volcanic glass can refer to any of several types of vitreous igneous rocks. Most commonly, it refers to:* Obsidian, a rhyolitic glass with high silica content....
. These phenocrysts are pyroxenes (augite

Augite

Augite is a Silicate_minerals#Single_chain_inosilicates: mineral described chemically as SiO3 or calcium magnesium iron silicate. The crystals are monoclinic and prismatic....
and pigeonite

Pigeonite

Pigeonite is a mineral in the clinopyroxene group. It has a general formula of Silicon2Oxygen6 The calcium cation fraction can vary from 5% to 25%, with iron and magnesium making up the rest of the cations....
), plagioclase

Plagioclase

Plagioclase is a very important series of Silicate minerals minerals within the feldspar family. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a solid solution series, more properly known as the plagioclase feldspar series ....
s, opaque crystal

Crystal

A crystal or crystalline solid is a solid material whose constituent atoms, molecules, or ions are arranged in an orderly repeating pattern extending in all three spatial dimensions....
s such as titanomagnetite or ilmenite

Ilmenite

Ilmenite is a weakly Magnetism titanium-iron oxide mineral which is iron-black or steel-gray. It is a crystalline iron titanium oxide . It crystallizes in the trigonal system, and it has the same crystal structure as corundum and hematite....
, and occasionally some olivine. Sometimes more differentiated volcanic products such andesite

Andesite

Andesite is an igneous rock, volcanic rock, of Igneous rock#Chemical classification, with aphanitic to porphyritic texture. The mineral assemblage is typically dominated by plagioclase plus pyroxene and/or hornblende....
s, dacite

Dacite

Dacite is an igneous rock, volcanic rock with a high iron content. It is intermediate in compositions between andesite and rhyolite, and, like andesite, it consists mostly of plagioclase feldspar with biotite, hornblende, and pyroxene ....
s and rhyodacite

Rhyodacite

Rhyodacite is an extrusive volcanic rock intermediate in composition between dacite and rhyolite. It is the extrusive equivalent of granodiorite....
s have been observed, but only in small quantities at the top of former magma chamber

Magma chamber

A magma chamber is a large underground pool of molten Rock lying under the surface of the earth's crust. The molten rock in such a chamber is under great pressure, and given enough time pressure can gradually fracture the rock around it creating outlets for the magma....
s.

Structures

Subaerial flood basalts can be of two kinds :

with a smooth or twisted surface : very compact surface; vesicle
Vesicle

Vesicle may refer to:* Synaptic vesicle* Auditory vesicle* Optic vesicles* Seminal vesicle* Subsporangial vesicle* Vesical arteries* Vesicle , a relatively small and enclosed compartment within a cell...
s and rare. Degassing was easy (magma maintained at a high temperature
Temperature

In physics, temperature is a physical property of a Physical system that underlies the common notions of hot and cold; something that feels hotter generally has the greater temperature....
and more fluid
Fluid

A fluid is defined as a substance that continually deforms under an applied shear stress. All liquids and all gases are fluids. Fluids are a subset of the Phase and include liquids, gas, Plasma physics and, to some extent, plasticity ....
in a chamber of a size such that confining pressure
Pressure

Pressure is the force per unit area applied to an object in a direction surface normal to the surface. Gauge pressure is the pressure relative to the local atmospheric or ambient pressure....
s 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 the 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

Massif Central

The Massif Central is an elevated region in south-central France, consisting of mountains and plateaus.Subject to volcano that has subsided in the last 10,000 years, these central mountains are separated from the Alps by a deep north-south cleft created by the Rh?ne River and known in French language as the sillon rhodanien ....
in Auvergne

Auvergne (région)

Auvergne is one of the 26 administrative regions of France of France.The current administrative region of Auvergne is larger than the historical provinces of France of Auvergne , and includes provinces and areas that historically were not part of Auvergne....
, there is a good example of chaotic basalt floods, produced by eruptions from Puy de la Vache and Puy de Lassolas

Puy de Lassolas

The Puy de Lassolas is a volcano in the Cha?ne des Puys in France, peaking at 1187 metres. It forms, with the Puy de Vache, a group of volcanic craters....
.

At depth, flows can crystallise more slowly, producing columnar jointing.

Geochemistry

Geochemical analysis of the major oxide

Oxide

An oxide is a chemical compound contaning at least one oxygen atom as well as at least one other element. Most of the Earth's crust consists of oxides....
s reveals a composition close to that of mid-ocean ridge

Mid-ocean ridge

A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, typically having a valley known as a rift running along its spine, formed by plate tectonics....
basalts (MORB) but also close to that of ocean island

Island

An island or isle is any piece of land that is surrounded by water. Very small islands such as emergent land features on atolls are called islets....
basalts (OIB

OIB

OIB is a three-letter abbreviation with multiple meanings, including:*Ocean island basalt, mainly alkaline mantle plume generated intra-plate basalts...
). These are in fact tholeiite

Tholeiite

Tholeiitic basalt is an igneous rock, a type of basalt. Like all basalt, the rock type is dominated by clinopyroxene plus plagioclase, with minor iron-titanium oxides....
s with a silicon dioxide

Silicon dioxide

The chemical compound 'silicon dioxide', also known as 'silica' , is an oxide of silicon with a chemical formula of and has been known for its hardness since antiquity....
percentage close to 50%.

Two kinds of basaltic floods basalts can be distinguished :

those poor in P₂O₅ and in TiO₂, called LPT
LPT

LPT is the original, yet still common, name of the parallel port interface on PC compatible computers. It was designed to operate a text computer printer that used IBM's 8-bit extended ASCII character set....
(low phosphorus
Phosphorus

Phosphorus is the chemical element that has the symbol P and atomic number 15. The name comes from the and . A Valency nonmetal of the nitrogen group, phosphorus is commonly found in inorganic phosphate minerals....
and titanium
Titanium

Titanium is a chemical element with the symbol Ti and atomic number 22. Sometimes called the ?space age metal?, it has a low density and is a strong, lustrous, corrosion-resistant transition metal with a silver colour....
)
those rich in P₂O₅ and in TiO₂, called HPT (high phosphorus and titanium)

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

Continental crust

The continental crust is the layer of igneous, sedimentary, and metamorphic rocks which form the continents and the areas of shallow seabed close to their shores, known as Continental shelf....
. 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

Crust (geology)

In geology, a crust is the outermost solid shell of a planet or moon, which is chemically distinct from the underlying mantle . Crusts of Earth , our Moon, Mercury , Venus, and Mars have been generated largely by igneous processes, and these crusts are richer in incompatible elements than their respective mantle s....
such as potassium

Potassium

Potassium is a chemical element. It has the symbol K , atomic number 19, and atomic mass 39.0983. Potassium was first isolated from potash, hence the name....
and strontium

Strontium

Strontium is a chemical element with the symbol Sr and the atomic number 38. An alkaline earth metal, strontium is a soft silver-white or yellowish metallic element that is highly reactive chemically....
.

The content in incompatible element

Incompatible element

Incompatible element is a term used in petrology and geochemistry.During the Fractional crystallization of magma, and magma generation by the partial melting of Mantle and crust, elements that have difficulty in entering cation sites of the minerals are concentrated in the melt phase of magma ....
s of basaltic floods is lower than that of ocean island basalts, but higher than that of mid-ocean ridge basalts.

Other occurrences and implications

Flood basalt volcanism has been implicated (along with the impact of large asteroid
Asteroid

Asteroids, sometimes called minor planets or planetoids, are small Solar System bodies in orbit around the Sun, smaller than planets but larger than meteoroids....
s and/or comet
Comet

A comet is a Small Solar System body that orbits the Sun and, when close enough to the Sun, exhibits a visible coma or a tail?both primarily from the effects of solar radiation upon the Comet nucleus....
s, as well as disease
Disease

A disease or medical condition is an abnormal condition of an organism that impairs bodily functions, associated with specific symptoms and Medical signs....
and long-term climate change
Climate change

Climate change is any long-term significant change in the expected patterns of average weather of a specific region over an appropriately significant period of time....
s) in major mass extinction events in the past.

Basalt floods on the planet Venus
Venus

Venus is the second-closest planet to the Sun, orbiting it every 224.7 Earth days. The planet is named after Venus , the Roman mythology goddess of love....
are even larger than those on Earth (see: Volcanism on Venus
Volcanism on Venus

The surface of Venus is dominated by volcano and has produced more volcanoes than any other planet in the solar system. It has a surface that is 90% basalt, and about 80% of the planet consists of a mosaic of volcanic lava plains, indicating that volcanism played a major role in shaping its surface....
). Their study may help understand the mechanisms responsible for these major geological events.

List of volcanic flood basalts

All major continental flood basalts (also known as traps) and oceanic plateaus, together forming a listing of large igneous province

Large igneous province

Large Igneous rock provinces were originally defined by Coffin and Eldholm as areas of Earth's crust that contain very large volumes of magmatic rocks erupted over extremely short geological time intervals of a few million years or less....
s, 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:

The Columbia
Columbia River

The Columbia River is the largest river in the Pacific Northwest region of North America. It is named after the Columbia Rediviva, the first ship from the western world known to have traveled up the river....
-Snake River
Snake River

The Snake River is a major tributary of the Columbia River in the U.S. states of Wyoming, Idaho, Oregon, and Washington. The river's length is , its drainage basin drains , and the average discharge at its mouth is ....
flood basalts (see Columbia River Basalt Group
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....
)
The Ethiopian and Yemen traps
Arabian-Nubian Shield

The Arabian-Nubian Shield is an exposure of Precambrian crystalline rocks on the flanks of the Red Sea. The crystalline rocks are mostly Neoproterozoic in age....
in the Ethiopian Highlands
Ethiopian Highlands

The Ethiopian Highlands are a rugged mass of mountains in Ethiopia, Eritrea , and northern Somalia in the Horn of Africa. The Ethiopian Highlands form the largest continuous area of its altitude in the whole continent, with little of its surface falling below 1500 m , while the summits reach heights of up to 4550 m ....
The Brito-Arctic province
Brito-Arctic province

The Brito-Arctic province is a major flood basalt province of the North Atlantic Ocean. Basaltic volcanism flowed in two main pulses. The first which occurred ~Paleocene was of 2 x 106 km³ in total volume, into the current western and southeastern Greenland and northwestern Great Britain....
The Deccan Traps
Deccan Traps

The Deccan Traps are a large igneous province located on the Deccan Plateau of west-central India and one of the largest volcanic features on Earth....
(India) 65 million years ago (end of Cretaceous Period)
The Caribbean large igneous province
Caribbean large igneous province

The Caribbean large igneous province consists of a major flood basalt, which created this large igneous province. It the source of the current large eastern Pacific oceanic plateau, of which the Caribbean-Colombian oceanic plateau is the tectonized remnant....
The Kerguelen Plateau
Kerguelen Plateau

The Kerguelen Plateau is an underwater volcanic large igneous province in the Indian Ocean. It lies about 3,000 km to the southwest of Australia and is nearly three times the size of Japan....
The Ontong Java–Manihiki–Hikurangi Plateau
The Paraná and Etendeka traps
Paraná and Etendeka traps

The Paran? and Etendeka traps in Brazil, South America comprise a large igneous province which includes both the main Paran? traps as well as the smaller severed portions of the flood basalts at the Etendeka traps in Namibia and Angola....
(Brazil-Namibia)
The Karoo and Ferrar provinces
Karoo-Ferrar

The Karoo and Farrar provinces together comprise a major flood basalt province, most of which is found in South Africa and Antarctica, although parts extend into South America, India, Australia and New Zealand....
(South Africa-Antarctica)
The Central Atlantic Magmatic Province
Central Atlantic Magmatic Province

The Central Atlantic magmatic province was formed during the breakup of Pangaea during the Mesozoic Era. The initial breakup of Pangaea in early Jurassic time provided a legacy of basaltic Dike , Sill , and lavas over a vast area around the present central North Atlantic Ocean....
The Siberian Traps
Siberian Traps

File:Extent_of_Siberian_traps_german.pngThe Siberian Traps form a large igneous province in Siberia. The massive eruptive event spans the Permian-Triassic boundary, about 251 to 250 million years ago, and was essentially coincident with the Permian?Triassic extinction event in what was one of the largest known volcano events of the l...
(Russia) 251 million years ago (end of Permian)
The Emeishan Traps
Emeishan Traps

The Emeishan Traps constitute a flood basalt volcanic province, or large igneous province, in southwestern China, centered in Sichuan province. It is sometimes referred to as the Permian Emeishan Large Igneous Province or variations of that term....
(western China)
The Viluy traps
The Pre-Devonian traps
The Mackenzie dike swarm
Mackenzie dike swarm

The Mackenzie dike swarm, also called the Mackenzie dikes, form a large igneous province in the western Canadian Shield of Canada. It is one of more than three dozen dike swarms in various parts of the Canadian Shield and is the largest dike swarm known on Earth, more than 500 kilometers wide and 3,000 kilometers long, exte...
The Strand Fiord Formation
Strand Fiord Formation

The Strand Fiord Formation is a Late Cretaceous volcanic component, located on northwestern and west-central Axel Heiberg Island, Nunavut, Canada....
The Chilcotin Group (south-central British Columbia, Canada)
The North Mountain Basalt
North Mountain (Nova Scotia)

North Mountain is a narrow north-south trending volcano mountain range on the Nova Scotia peninsula, stretching from Brier Island, Nova Scotia to Cape Split, Nova Scotia....

Flood basalt

Petrography

Structures

Geochemistry

Other occurrences and implications

List of volcanic flood basalts

See also