East Rock from SSS Hall, October 17, 2008

Trap rock, also known as either trapp or trap, is any dark-colored, fine-grained, non-granitic intrusive or extrusive

igneous rock Igneous rock (derived from the Latin word ''ignis'' meaning fire), or magmatic rock, is one of the three main rock types, the others being sedimentary and metamorphic. Igneous rock is formed through the cooling and solidification of magma o ...

. Types of trap rock include

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...

peridotite Peridotite ( ) is a dense, coarse-grained igneous rock consisting mostly of the silicate minerals olivine and pyroxene. Peridotite is ultramafic, as the rock contains less than 45% silica. It is high in magnesium (Mg2+), reflecting the high pr ...

diabase Diabase (), also called dolerite () or microgabbro, is a mafic, holocrystalline, subvolcanic rock equivalent to volcanic basalt or plutonic gabbro. Diabase dikes and sills are typically shallow intrusive bodies and often exhibit fine-grain ...

, and

gabbro Gabbro () is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is ...

.Neuendorf, K.K.E., J.P. Mehl, Jr., and J.A. Jackson, J.A., eds. (2005) ''Glossary of Geology'' (5th ed.) American Geological Institute, Alexandria, Virginia. 779 pp. Trapp (trap) is also used to refer to flood (plateau) basalts, e.g. the

Deccan Traps The Deccan Traps is a large igneous province of west-central India (17–24°N, 73–74°E). It is one of the largest volcanic features on Earth, taking the form of a large shield volcano. It consists of numerous layers of solidified flo ...

and

Siberian Traps The Siberian Traps (russian: Сибирские траппы, Sibirskiye trappy) is a large region of volcanic rock, known as a large igneous province, in Siberia, Russia. The massive eruptive event that formed the traps is one of the largest ...

.Le Maitre, R. W., ed. (2002) ''Igneous Rocks: A Classification and Glossary of Terminology''. Cambridge University Press, New York. 236 pp. The erosion of trap rock created by the stacking of successive

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or ...

flows often created a distinct stairstep landscape from which the term ''trap'' was derived from the Swedish word ''trappa'', which means "stairway". The slow cooling of

magma Magma () is the molten or semi-molten natural material from which all igneous rocks are formed. Magma is found beneath the surface of the Earth, and evidence of magmatism has also been discovered on other terrestrial planets and some natura ...

either as a

sill Sill may refer to: * Sill (dock), a weir at the low water mark retaining water within a dock * Sill (geology), a subhorizontal sheet intrusion of molten or solidified magma * Sill (geostatistics) * Sill (river), a river in Austria * Sill plate, ...

or as a thick

flow sometimes creates systematic vertical fractures within the resulting layer of trap rock. These fractures often form rock columns that are typically hexagonal, but also four- to eight-sided.Muller, G. (1998) "Experimental simulation of basalt columns". ''Journal of Volcanology and Geothermal Research''. vol. 86, no. 1–4, pp. 93–96Spry, A. (1962). "The origin of columnar jointing, particularly in basalt flows". ''Journal of the Geological Society of Australia''. Vol. 5, pp. 191–216.

Uses

Trap rock, i.e. basalt or diabase, has a variety of uses. A major use for basalt is crushed rock for road and housing construction in

concrete Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most wid ...

macadam Macadam is a type of road construction, pioneered by Scottish engineer John Loudon McAdam around 1820, in which crushed stone is placed in shallow, convex layers and compacted thoroughly. A binding layer of stone dust (crushed stone from the ...

, and paving stones. Because of its insensitivity to chemical influences, resistance to mechanical stress, high dry relative density, frost resistance, and sea water resistance, trap rock is used as ballast for railroad

track bed The track bed or trackbed is the groundwork onto which a railway track is laid. Trackbeds of disused railways are sometimes used for recreational paths or new light rail links. According to Network Rail, the trackbed is the layers of ballast a ...

and hydraulic engineering rock (

riprap Riprap (in North American English), also known as rip rap, rip-rap, shot rock, rock armour (in British English) or rubble, is human-placed rock or other material used to protect shoreline structures against scour and water, wave, or ice erosion. ...

) in coast and bank protection for paving embankments. It is also used for the production of cast rock that is used in corrosion and abrasion protection, as for sewage pipes and acid-resistant rocks. Other uses of trap rock include gardening and landscaping, for the production of millstones, for the production of mineral fibres (basalt wool), as a flux in ceramic masses and glazes, for the production of glass ceramics, crushed as a filter aggregate (air filtration of poison gas in ABC bunkers), as filter bed material water treatment facilities, and ground as a soil improvement product.Lorenz, W., and W. Gwosdz (2003). ''Manual on the Geological-technical Assessment of Mineral Construction Materials''. Geological Yearbook Special Issue series H, issue SH15. Federal Institute for Geosciences and Natural Resources and the State geological surveys in the Federal Republic of Germany, Commission E. Hense (Naegele and Obermiller), Hanover, Germany. 497 pp. . Trap rock has been used to construct buildings and churches: Trinity Church on the Green with trap rock quarried from

Eli Whitney Eli Whitney Jr. (December 8, 1765January 8, 1825) was an American inventor, widely known for inventing the cotton gin, one of the key inventions of the Industrial Revolution that shaped the economy of the Antebellum South. Although Whitney hi ...

's quarry, is a particularly colorful example of a red-orange-brown-colored, natural-faced trap rock. It was also used for foundations and railroad beds in the New Haven area.

Examples

Well-known examples of outcropping trap rock include both intrusive sills and extrusive lava flows. They include the

Palisades Sill The Palisades Sill is a Triassic, 200 Ma diabase intrusion. It extends through portions of New York and New Jersey. It is most noteworthy for The Palisades, the cliffs that rise steeply above the western bank of the Hudson River. The ideal loc ...

, a

Triassic The Triassic ( ) is a geologic period and system which spans 50.6 million years from the end of the Permian Period 251.902 million years ago ( Mya), to the beginning of the Jurassic Period 201.36 Mya. The Triassic is the first and shortest per ...

, 200 Ma

intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...

that forms the Palisades along of the

Hudson River The Hudson River is a river that flows from north to south primarily through eastern New York. It originates in the Adirondack Mountains of Upstate New York and flows southward through the Hudson Valley to the New York Harbor between Ne ...

New York New York most commonly refers to: * New York City, the most populous city in the United States, located in the state of New York * New York (state), a state in the northeastern United States New York may also refer to: Film and television * '' ...

and

New Jersey New Jersey is a state in the Mid-Atlantic and Northeastern regions of the United States. It is bordered on the north and east by the state of New York; on the east, southeast, and south by the Atlantic Ocean; on the west by the Delawa ...

. Vast areas of trap rock in the form of thick lava flows and other volcanic rocks comprise the

of India and

of Russia. Other prominent basalt ridges, mountains, buttes, canyons, and other landscape features include: * In North America: ** The ridges and cliffs of the

Columbia River Gorge The Columbia River Gorge is a canyon of the Columbia River in the Pacific Northwest of the United States. Up to deep, the canyon stretches for over as the river winds westward through the Cascade Range, forming the boundary between the st ...

in Oregon and

Washington state Washington (), officially the State of Washington, is a U.S. state, state in the Northwestern United States, Pacific Northwest region of the Western United States. Named for George Washington—the first President of the United States, U.S. p ...

** Basalt Mountain in

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of the ...

, for which the town of

Basalt, Colorado The Town of Basalt is a home rule municipality located in Eagle and Pitkin counties, Colorado, United States. The town population was 3,984 at the 2020 United States Census with 2,917 residing in Eagle County and 1,067 residing in Pitkin Cou ...

is named. ** The

Metacomet Ridge The Metacomet Ridge, Metacomet Ridge Mountains, or Metacomet Range of southern New England is a narrow and steep fault-block mountain ridge known for its extensive cliff faces, scenic vistas, microclimate ecosystems, and rare or endangered plants. ...

Connecticut Connecticut () is the southernmost state in the New England region of the Northeastern United States. It is bordered by Rhode Island to the east, Massachusetts to the north, New York (state), New York to the west, and Long Island Sound to the ...

and

Massachusetts Massachusetts (Massachusett: ''Muhsachuweesut Massachusett_writing_systems.html" ;"title="nowiki/> məhswatʃəwiːsət.html" ;"title="Massachusett writing systems">məhswatʃəwiːsət">Massachusett writing systems">məhswatʃəwiːsət'' En ...

. ** The

Watchung Mountains The Watchung Mountains (once called the Blue Hills) are a group of three long low ridges of volcanic origin, between high, lying parallel to each other in northern New Jersey in the United States. The name is derived from the American Native Lena ...

of New Jersey ** Devils Postpile National Monument and other parts of

California California is a state in the Western United States, located along the Pacific Coast. With nearly 39.2million residents across a total area of approximately , it is the most populous U.S. state and the 3rd largest by area. It is also the m ...

's inner coastal range. ** Most of the

Hawaiian Islands The Hawaiian Islands ( haw, Nā Mokupuni o Hawai‘i) are an archipelago of eight major islands, several atolls, and numerous smaller islets in the North Pacific Ocean, extending some from the island of Hawaii in the south to northernmost ...

and their mountains are composed of basalt or similar volcanic rock. ** The Green Gardens region of

Gros Morne National Park Gros Morne National Park is a National Parks of Canada, Canadian national park and World Heritage Site located on the west coast of Newfoundland and Labrador, Newfoundland. At , it is the second largest national park in Atlantic Canada after To ...

Newfoundland Newfoundland and Labrador (; french: Terre-Neuve-et-Labrador; frequently abbreviated as NL) is the easternmost province of Canada, in the country's Atlantic region. The province comprises the island of Newfoundland and the continental region ...

* The

Emeishan Traps The Emeishan Traps constitute a flood basalt volcanic province, or large igneous province, in south-western China, centred in Sichuan province. It is sometimes referred to as the Permian Emeishan Large Igneous Province or Emeishan Flood Basalts. Li ...

in China *

Giant's Causeway The Giant's Causeway is an area of about 40,000 interlocking basalt columns, the result of an ancient volcanic fissure eruption. It is located in County Antrim on the north coast of Northern Ireland, about three miles (5 km) northeast of ...

in Ireland *

Organ Pipes National Park The Organ Pipes National Park, abbreviated as OPNP, is a national park located in the Central region of Victoria, Australia. The protected area was established with the focus on conservation of the native flora and fauna, and preservation of ...

in Australia * The

Paraná and Etendeka Traps The Paraná-Etendeka traps (or Paraná and Etendeka Plateau; or Paraná and Etendeka Province) comprise a large igneous province that includes both the main Paraná traps (in Paraná Basin, a South American geological basin) as well as the smal ...

of Brazil * The island of

Surtsey Surtsey (" Surtr's island" in Icelandic, ) is a volcanic island located in the Vestmannaeyjar archipelago off the southern coast of Iceland. At Surtsey is the southernmost point of Iceland. It was formed in a volcanic eruption which began ...

Iceland Iceland ( is, Ísland; ) is a Nordic island country in the North Atlantic Ocean and in the Arctic Ocean. Iceland is the most sparsely populated country in Europe. Iceland's capital and largest city is Reykjavík, which (along with its ...

, a new (1963) volcanic island. * The

Vilyuy Traps The Vilyuy ( rus, Вилю́й, p=vʲɪˈlʲʉj; sah, Бүлүү, ''Bülüü'', ) is a river in Russia, the longest tributary of the Lena. About long, it flows mostly within the Sakha Republic. Its basin covers about . History The river is fir ...

of Russia

References

{{DEFAULTSORT:Trap Rock Igneous petrology Igneous intrusions Mafic intrusions

Uses

Examples

See also

References