Volcanic crater

A volcanic crater is an approximately circular depression in the ground caused by volcanic activity.[1] It is typically a bowl-shaped feature within which occurs a vent or vents. During volcanic eruptions, molten magma and volcanic gases rise from an underground magma chamber, through a tube-shaped conduit, until they reach the crater's vent, from where the gases escape into the atmosphere and the magma is erupted as lava. A volcanic crater can be of large dimensions, and sometimes of great depth. During certain types of explosive eruptions, a volcano's magma chamber may empty enough for an area above it to subside, forming a type of larger depression known as a caldera.

Mount Cameroon craters
Craters on Mount Cameroon
Tangkuban Parahu
The volcanic crater of a Tangkuban Parahu mount, Bandung, Indonesia

Geomorphology

In most volcanoes, the crater is situated at the top of a mountain formed from the erupted volcanic deposits such as lava flows and tephra. Volcanoes that terminate in such a summit crater are usually of a conical form. Other volcanic craters may be found on the flanks of volcanoes, and these are commonly referred to as flank craters. Some volcanic craters may fill either fully or partially with rain and/or melted snow, forming a crater lake.

A crater may be breached during an eruption, either by explosions or by lava, or through later erosion. Breached craters have a much lower rim on one side.

Some volcanoes, such as maars, consist of a crater alone, with scarcely any mountain at all. These volcanic explosion craters are formed when magma rises through water-saturated rocks, which causes a phreatic eruption. Volcanic craters from phreatic eruptions often occur on plains away from other obvious volcanoes. Not all volcanoes form craters.

See also

  • Caldera – Cauldron-like volcanic feature formed by the emptying of a magma chamber

Footnotes

  1. ^ "Glossary of Terms: C". physicalgeography.net. Retrieved 2008-04-12.
Aljojuca

Aljojuca Municipality is a municipality located in central eastern Puebla, Mexico.It is bordered by the municipalities of San Juan Atenco to the south, Chalchicomula de Sesma (Cd. Serdan) to the southeast, Tlachichuca to the east, San Nicolas, Buenos Aires to the north, and San Salvador El Seco to the west. Nearby is the highest peak of Mexico, Citlaltepetl or Pico de Orizaba.

Located on the plains of San Andres, Aljojuca was founded in colonial times with its main purpose being the prime grazing lands around the small settlement. It quickly became the most established town between El Seco and San Andres Chalchicomula (now Serdan), providing employment to many of the region's Indian population. Currently the population numbers approximately 5000 and is distributed in the settlements of Aljojuca, San Miguel Tecuitlapa, and San Antonio Jalapasco. However the numbers continue to fall due to large-scale emigration, especially in recent years.

Local attractions include a 1 km-wide volcanic crater lake, known as the Laguna de Aljojuca, a 19th-century church, completed in 1906, a 17th-century church, and the ruins of the hacienda Cascantla.

Black Bottom Crater

Black Bottom Crater is a volcanic crater located in Arizona, east-northeast of Sunset Crater, and west-southwest of Roden Crater. To the northwest is Strawberry Crater. Black Bottom Crater is a cinder cone in the San Francisco volcanic field.

Cave Bay

Cave Bay (53°2′S 73°22′E) is a cove, 0.3 nautical miles (0.6 km) wide, which has been formed by the erosion of an extinct volcanic crater of which Mount Andree forms the north side, indenting the west side of Heard Island between West Bay and South West Bay. The cove is roughly charted on an American sealer's sketch map prepared during the 1860–70 period. It was more accurately charted and first named on a geological sketch map illustrating the 1929 work of the British Australian New Zealand Antarctic Research Expedition under Douglas Mawson.

Centrochelys atlantica

Centrochelys atlantica is an extinct species of tortoise that lived in the Pleistocene. It was first recorded in the volcanic crater on Sal, Cape Verde. It was initially identified as similar to the extant Testudo calcarata (= Centrochelys sulcata). The species is no longer present anywhere in the Cape Verde islands. It has since been described as a new species, differentiated from C. sulcata by its smaller size and lesser robusticity. It does not seem there is any evidence this species came into contact with humans.

Crater Lake (South Shetland Islands)

Crater Lake is a volcanic crater, now filled with water, lying north-west of Mount Kirkwood on the south side of Deception Island, in the South Shetland Islands of Antarctica. The descriptive name was given by the United Kingdom Antarctic Place-Names Committee (UK-APC) in 1959.

Crater lake

A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite, or in the crater left by an artificial explosion caused by humans. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not made. Crater lakes covering active (fumarolic) volcanic vents are sometimes known as volcanic lakes, and the water within them is often acidic, saturated with volcanic gases, and cloudy with a strong greenish color. For example, the crater lake of Kawah Ijen in Indonesia has a pH of under 0.5. Lakes located in dormant or extinct volcanoes tend to have fresh water, and the water clarity in such lakes can be exceptional due to the lack of inflowing streams and sediment.

Laguna de la Cocha

La Cocha Lagoon (Spanish: Laguna de la Cocha) is a 39,000-hectare (96,000-acre) volcanic crater lake located within the Pasto Municipality in Nariño, Colombia.

La Cocha Lagoon is Colombia's second largest inland body of water after Lake Tota in terms of surface area.

Lakes of New Zealand

There are 3,820 lakes in New Zealand that have a surface area larger than one hectare. Many of the lakes in the central North Island are volcanic crater lakes. The majority of the lakes near the Southern Alps were carved by glaciers. Artificial lakes created as hydroelectric reservoirs are common in South Canterbury, Central Otago and along the Waikato River.

Maar

A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow crater lake which may also be called a maar. The name comes from a Moselle Franconian dialect word used for the circular lakes of the Daun area of Germany.

Maars are shallow, flat-floored craters that scientists interpret as having formed above diatremes as a result of a violent expansion of magmatic gas or steam; deep erosion of a maar presumably would expose a diatreme. Maars range in size from 60 to 8,000 m (200 to 26,250 ft) across and from 10 to 200 m (33 to 656 ft) deep; most maars commonly fill with water to form natural lakes. Most maars have low rims composed of a mixture of loose fragments of volcanic rocks and rocks torn from the walls of the diatreme.

Mehetia

Meheti'a or Me'eti'a is a volcanic island in the Windward Islands, in the east of the Society Islands in French Polynesia. This island is a very young active stratovolcano 110 kilometres (68 mi) east of the Taiarapu Peninsula of Tahiti. It belongs to the Teahiti'a-Mehetia hotspot.

The island has an area of 2.3 square kilometres (0.89 sq mi) and its highest point is 435 metres (1,427 ft). Meheti'a's well-defined volcanic crater contains a very active hot point. In 1981 the island was the centre of earthquakes.

Monti Cimini

The Monti Cimini, in English: Cimini Hills, are a range of densely wooded volcanic hills approximately 56 km (35 mi) north-west of Rome. They are part of the Antiapennine range, facing the Apennines main range towards the Tyrrhenian Sea. They are situated in the centre of Tuscia Viterbese, the highest point at Mount Cimino, 1,053 m (3,455 ft) above sea level. Lake Vico, a volcanic crater lake, is situated in the hills.

The vegetation is predominantly beech forestation. The area is renowned for its hot springs, renaissance villas and Etruscan ruins.

Nemi

Nemi is a town and comune in the Metropolitan City of Rome (central Italy), in the Alban Hills overlooking Lake Nemi, a volcanic crater lake. It is 6 kilometres (4 mi) northwest of Velletri and about 30 kilometres (19 mi) southeast of Rome.

The town's name derives from the Latin nemus, or "holy wood". In antiquity the area had no town, but the grove was the site of one of the most famous of Roman cults and temples: the Temple of Diana Nemorensis, a study of which served as the seed for Sir James Frazer's seminal work on the anthropology of religion, The Golden Bough.

In 1514 Marcantonio I Colonna gave to Nemi the "Statuti e Capituli del Castello di Nemi", the first city statute with rules and regulations to observe.

Onepoto (volcanic crater)

Onepoto is the name of a volcanic explosion crater (or maar) in North Shore City, New Zealand. It is a part of the Auckland volcanic field.

Located near the approaches to the Auckland Harbour Bridge, it was created by a series of eruptions approximately 250,000 years ago. The crater first became a freshwater lake, and later became a tidal lagoon when sea level rose to the present level 7,000 years ago after the last ice age. The crater's floor has been reclaimed, with recreational sports fields and a pond, and some parts of the tuff ring were quarried away in the 1950s to provide fill for the Northern Motorway.

Rootless cone

A rootless cone, also formerly called a pseudocrater, is a volcanic landform which resembles a true volcanic crater, but differs in that it is not an actual vent from which lava has erupted. They are characterised by the absence of any magma conduit which connects below the surface of a planet.

Rootless cones are formed by steam explosions as flowing hot lava crosses over a wet surface, such as a swamp, a lake, or a pond. The explosive gases break through the lava surface in a manner similar to a phreatic eruption, and the tephra builds up crater-like forms which can appear very similar to real volcanic craters.

Well known examples are found in Iceland like the craters in the lake Mývatn (Skútustaðagígar), the Rauðhólar in the region of the capital city Reykjavík or the Landbrotshólar located in South-Iceland in the Katla UNESCO Global Geopark in the vicinity of Kirkjubæjarklaustur. Rootless cones have also been discovered in the Athabasca Valles region of Mars, where lava flows superheated groundwater in the underlying rocks.Volcanologists witnessed the formation of a rootless cone for the first time in history during a steam explosion in connection with the first eruption of Eyjafjallajökull in March 2010.

Tooting (crater)

Tooting is a multi-layered Volcanic Crater (a type of rampart crater) at 23.1°N, 207.1°E, in Amazonis Planitia (Amazonis quadrangle), due west of the volcano Olympus Mons, on Mars. . It was identified by planetary geologist Peter Mouginis-Mark in September 2004. Scientists estimate that its age is on the order of hundreds of thousands of years, which is relatively young for a Martian crater. A later study confirms this order of magnitude estimate. A preliminary paper describing the geology and geometry of Tooting was published in 2007 by the journal "Meteoritics and Planetary Science", vol. 42, pages 1615 - 1625. Further papers have more recently been published, including a 2010 analysis of flows on the walls of Tooting crater by A.R. Morris et al. ("Icarus vol. 209, p. 369 - 389), and a 2012 review paper by P.J. Mouginis-Mark and J.M. Boyce in "Chemie der Erde Geochemistry", vol. 72, p. 1 - 23. A geologic map has also been submitted in 2012 to the U.S. Geological Survey for consideration and future publication.

Tyrrhenus Mons

Tyrrhenus Mons, formerly Tyrrhena Mons or Tyrrhena Patera, is a large volcano in the Mare Tyrrhenum quadrangle of Mars, located at 21.36° south latitude and 253.47° west longitude. The name "Tyrrhena Patera" now refers only to the central depression, a volcanic crater or caldera. It was named after a classical albedo feature name. Pit chains are found at the summit of Tyrrhenus Mons. They are formed by collapse of material into underground voids. Since they form chains and concentric fractures that are aligned, they are probably caused by extension of the surface. Volcanic processes made the crust pull apart. Voids were formed, then material fell into them, leaving holes. It is one of the oldest volcanoes on Mars. As a consequence of its old age, Tyrrhenus Mons has many radiating gullies on its slope. When it was formed, magma may have gone through frozen ground and then erupted as easily eroded ash, instead of lava flows.

Ubehebe Crater

Ubehebe Crater is a large volcanic crater of the Ubehebe Craters volcanic field in the northern half of Death Valley, in Death Valley National Park, California, USA.

Volcanogenic lake

A volcanogenic lake is a lake formed as a result of volcanic activity. They are generally a body of water inside an inactive volcanic crater (crater lakes) but can also be large volumes of molten lava within an active volcanic crater (lava lakes) and waterbodies constrained by lava flows, pyroclastic flows or lahars in valley systems. The term volcanic lake is also used to describe volcanogenic lakes, although it is more commonly assigned to those which host a vent.

Wizard Island

Wizard Island is a volcanic cinder cone which forms an island at the west end of Crater Lake in Crater Lake National Park, Oregon. The top of the island reaches 6,933 feet (2,113 m) above sea level, about 755 feet (230 m) above the average surface of the lake. The cone is capped by a volcanic crater about 500 feet (150 m) wide and 100 feet (30 m) deep. The crater was named the "Witches Cauldron" by William Gladstone Steel in 1885, who also gave Wizard Island its name at the same time.

The land area of the island is 315.85 acres (127.82 ha).

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