Caldera

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Mount Mazama's eruption timeline, an example of caldera formation Mount Mazama eruption timeline.PNG
Mount Mazama's eruption timeline, an example of caldera formation

A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber/reservoir in a volcanic eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is lost. The ground surface then collapses downward into the emptied or partially emptied magma chamber, leaving a massive depression at the surface (from one to dozens of kilometers in diameter). Although sometimes described as a crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Only seven caldera-forming collapses are known to have occurred since 1900, most recently at Bárðarbunga volcano, Iceland in 2014. [1]

Contents

Etymology

The term caldera comes from Spanish caldera , and Latin caldaria , meaning "cooking pot". In some texts the English term cauldron is also used. The term caldera was introduced into the geological vocabulary by the German geologist Leopold von Buch when he published his memoirs of his 1815 visit to the Canary Islands, [note 1] where he first saw the Las Cañadas caldera on Tenerife, with Montaña Teide dominating the landscape, and then the Caldera de Taburiente on La Palma.

Caldera formation

Animation of analogue experiment showing origin of volcanic caldera in box filled with flour. Origin of volcanic caldera via analogue model.gif
Animation of analogue experiment showing origin of volcanic caldera in box filled with flour.
Landsat image of Lake Toba, on the island of Sumatra, Indonesia (100 km/62 mi long and 30 km/19 mi wide, one of the world's largest calderas). A resurgent dome formed the island of Samosir. Toba zoom.jpg
Landsat image of Lake Toba, on the island of Sumatra, Indonesia (100 km/62 mi long and 30 km/19 mi wide, one of the world's largest calderas). A resurgent dome formed the island of Samosir.

A collapse is triggered by the emptying of the magma chamber beneath the volcano, sometimes as the result of a large explosive volcanic eruption (see Tambora in 1815), but also during effusive eruptions on the flanks of a volcano (see Piton de la Fournaise in 2007) [2] or in a connected fissure system (see Bárðarbunga in 2014–2015). If enough magma is ejected, the emptied chamber is unable to support the weight of the volcanic edifice above it. A roughly circular fracture, the "ring fault", develops around the edge of the chamber. Ring fractures serve as feeders for fault intrusions which are also known as ring dikes. Secondary volcanic vents may form above the ring fracture. As the magma chamber empties, the center of the volcano within the ring fracture begins to collapse. The collapse may occur as the result of a single cataclysmic eruption, or it may occur in stages as the result of a series of eruptions. The total area that collapses may be hundreds or thousands of square kilometers.

Mineralization in calderas

Caldera formation under water. Caldera formation.gif
Caldera formation under water.

Some calderas are known to host rich ore deposits. Metal-rich fluids can circulate through the caldera, forming hydrothermal ore deposits of metals such as lead, silver, gold, mercury, lithium and uranium. [3] One of the world's best-preserved mineralized calderas is the Sturgeon Lake Caldera in northwestern Ontario, Canada, which formed during the Neoarchean era [4] about 2.7 billion years ago. [5]

Types of caldera

Explosive caldera eruptions

If the magma is rich in silica, the caldera is often filled in with ignimbrite, tuff, rhyolite, and other igneous rocks. Silica-rich magma has a high viscosity, and therefore does not flow easily like basalt. As a result, gases tend to become trapped at high pressure within the magma. When the magma approaches the surface of the Earth, the rapid off-loading of overlying material causes the trapped gases to decompress rapidly, thus triggering explosive destruction of the magma and spreading volcanic ash over wide areas. Further lava flows may be erupted.

If volcanic activity continues, the center of the caldera may be uplifted in the form of a resurgent dome such as is seen at Cerro Galán, Lake Toba, Yellowstone, etc., by subsequent intrusion of magma. A silicic or rhyolitic caldera may erupt hundreds or even thousands of cubic kilometers of material in a single event. Even small caldera-forming eruptions, such as Krakatoa in 1883 or Mount Pinatubo in 1991, may result in significant local destruction and a noticeable drop in temperature around the world. Large calderas may have even greater effects.

When Yellowstone Caldera last erupted some 650,000 years ago, it released about 1,000 km3 of material (as measured in dense rock equivalent (DRE)), covering a substantial part of North America in up to two metres of debris. By comparison, when Mount St. Helens erupted in 1980, it released ~1.2 km3 (DRE) of ejecta. The ecological effects of the eruption of a large caldera can be seen in the record of the Lake Toba eruption in Indonesia.

Toba

About 74,000 years ago, this Indonesian volcano released about 2,800 cubic kilometres (670 cu mi) dense-rock equivalent of ejecta. This was the largest known eruption during the ongoing Quaternary period (the last 2.6 million years) and the largest known explosive eruption during the last 25 million years. In the late 1990s, anthropologist Stanley Ambrose [6] proposed that a volcanic winter induced by this eruption reduced the human population to about 2,000–20,000 individuals, resulting in a population bottleneck. More recently, Lynn Jorde and Henry Harpending proposed that the human species was reduced to approximately 5,000-10,000 people. [7] There is no direct evidence, however, that either theory is correct, and there is no evidence for any other animal decline or extinction, even in environmentally sensitive species. [8] There is evidence that human habitation continued in India after the eruption. [9]

Eruptions forming even larger calderas are known, especially La Garita Caldera in the San Juan Mountains of Colorado, where the 5,000 cubic kilometres (1,200 cu mi) Fish Canyon Tuff was blasted out in eruptions about 27.8 million years ago. [10] [11]

At some points in geological time, rhyolitic calderas have appeared in distinct clusters. The remnants of such clusters may be found in places such as the San Juan Mountains of Colorado (formed during the Oligocene, Miocene, and Pliocene epochs) or the Saint Francois Mountain Range of Missouri (erupted during the Proterozoic eon). [12]

Satellite photograph of the summit caldera on Fernandina Island in the Galapagos archipelago. La Cumbre - ISS.JPG
Satellite photograph of the summit caldera on Fernandina Island in the Galápagos archipelago.
Oblique aerial photo of Nemrut Caldera, Van Lake, Eastern Turkey Nemrut Caldera aerial.jpg
Oblique aerial photo of Nemrut Caldera, Van Lake, Eastern Turkey

Non-explosive calderas

Sollipulli Caldera, located in central Chile near the border with Argentina, filled with ice. The volcano is in the southern Andes Mountains within Chile's Parque Nacional Villarica. Iss038e012569, Caldera Sollipulli.jpg
Sollipulli Caldera, located in central Chile near the border with Argentina, filled with ice. The volcano is in the southern Andes Mountains within Chile's Parque Nacional Villarica.

Some volcanoes, such as the large shield volcanoes Kīlauea and Mauna Loa on the island of Hawaii, form calderas in a different fashion. The magma feeding these volcanoes is basalt, which is silica poor. As a result, the magma is much less viscous than the magma of a rhyolitic volcano, and the magma chamber is drained by large lava flows rather than by explosive events. The resulting calderas are also known as subsidence calderas and can form more gradually than explosive calderas. For instance, the caldera atop Fernandina Island collapsed in 1968 when parts of the caldera floor dropped 350 metres (1,150 ft). [14]

Extraterrestrial calderas

Since the early 1960s, it has been known that volcanism has occurred on other planets and moons in the Solar System. Through the use of manned and unmanned spacecraft, volcanism has been discovered on Venus, Mars, the Moon, and Io, a satellite of Jupiter. None of these worlds have plate tectonics, which contributes approximately 60% of the Earth's volcanic activity (the other 40% is attributed to hotspot volcanism). [15] Caldera structure is similar on all of these planetary bodies, though the size varies considerably. The average caldera diameter on Venus is 68 km (42 mi). The average caldera diameter on Io is close to 40 km (25 mi), and the mode is 6 km (3.7 mi); Tvashtar Paterae is likely the largest caldera with a diameter of 290 km (180 mi). The average caldera diameter on Mars is 48 km (30 mi), smaller than Venus. Calderas on Earth are the smallest of all planetary bodies and vary from 1.6–80 km (1–50 mi) as a maximum. [16]

The Moon

The Moon has an outer shell of low-density crystalline rock that is a few hundred kilometers thick, which formed due to a rapid creation. The craters of the Moon have been well preserved through time and were once thought to have been the result of extreme volcanic activity, but actually were formed by meteorites, nearly all of which took place in the first few hundred million years after the Moon formed. Around 500 million years afterward, the Moon's mantle was able to be extensively melted due to the decay of radioactive elements. Massive basaltic eruptions took place generally at the base of large impact craters. Also, eruptions may have taken place due to a magma reservoir at the base of the crust. This forms a dome, possibly the same morphology of a shield volcano where calderas universally are known to form. [15] Although caldera-like structures are rare on the Moon, they are not completely absent. The Compton-Belkovich Volcanic Complex on the far side of the Moon is thought to be a caldera, possibly an ash-flow caldera. [17]

Mars

The volcanic activity of Mars is concentrated in two major provinces: Tharsis and Elysium. Each province contains a series of giant shield volcanoes that are similar to what we see on Earth and likely are the result of mantle hot spots. The surfaces are dominated by lava flows, and all have one or more collapse calderas. [15] Mars has the largest volcano in the Solar System, Olympus Mons, which is more than three times the height of Mount Everest, with a diameter of 520 km (323 miles). The summit of the mountain has six nested calderas. [18]

Venus

Because there is no plate tectonics on Venus, heat is mainly lost by conduction through the lithosphere. This causes enormous lava flows, accounting for 80% of Venus' surface area. Many of the mountains are large shield volcanoes that range in size from 150–400 km (95–250 mi) in diameter and 2–4 km (1.2–2.5 mi) high. More than 80 of these large shield volcanoes have summit calderas averaging 60 km (37 mi) across. [15]

Io

Io, unusually, is heated by solid flexing due to the tidal influence of Jupiter and Io's orbital resonance with neighboring large moons Europa and Ganymede, which keep its orbit slightly eccentric. Unlike any of the planets mentioned, Io is continuously volcanically active. For example, the NASA Voyager 1 and Voyager 2 spacecraft detected nine erupting volcanoes while passing Io in 1979. Io has many calderas with diameters tens of kilometers across. [15]

List of volcanic calderas

Aerial view of the Laacher See, Germany. Laacher See - Luftaufnahme.jpg
Aerial view of the Laacher See, Germany.

Erosion calderas

See also

Notes

  1. Leopold von Buch's book Physical Description of the Canary Isles was published in 1825

Related Research Articles

Lake Toba Crater lake located in Sumatra, Indonesia

Lake Toba is a large natural lake in Sumatra, Indonesia occupying the caldera of a supervolcano. The lake is located in the middle of the northern part of the island of Sumatra, with a surface elevation of about 900 metres (2,953 ft), the lake stretches from 2.88°N 98.52°E to 2.35°N 99.1°E. The lake is about 100 kilometres long, 30 kilometres (19 mi) wide, and up to 505 metres (1,657 ft) deep. It is the largest lake in Indonesia and the largest volcanic lake in the world. Lake Toba Caldera is one of the nineteen Geoparks in Indonesia, which is proposed to be included in the UNESCO Global Geopark.

Supervolcano Volcano that has erupted 1000 cubic km in a single eruption

A supervolcano is a large volcano that has had an eruption with a Volcanic Explosivity Index (VEI) of 8, the largest recorded value on the index. This means the volume of deposits for that eruption is greater than 1,000 cubic kilometers.

Volcano rupture in the crust of a planetary-mass object that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface

A volcano is a rupture in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface.

Stratovolcano Tall, conical volcano built up by many layers of hardened lava and other ejecta

A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava, tephra, pumice and ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and periodic intervals of explosive eruptions and effusive eruptions, although some have collapsed summit craters called calderas. The lava flowing from stratovolcanoes typically cools and hardens before spreading far, due to high viscosity. The magma forming this lava is often felsic, having high-to-intermediate levels of silica, with lesser amounts of less-viscous mafic magma. Extensive felsic lava flows are uncommon, but have travelled as far as 15 km (9.3 mi).

Ring of Fire Area of high earthquake and volcanic activity, also the circum-Pacific belt

The Ring of Fire is a major area in the basin of the Pacific Ocean where many earthquakes and volcanic eruptions occur. In a large 40,000 km (25,000 mi) horseshoe shape, it is associated with a nearly continuous series of oceanic trenches, volcanic arcs, and volcanic belts and plate movements. It has 452 volcanoes.

Shield volcano Low profile volcano usually formed almost entirely of fluid lava flows

A shield volcano is a type of volcano usually composed almost entirely of fluid lava flows. It is named for its low profile, resembling a warrior's shield lying on the ground. This is caused by the highly fluid lava erupted, which travels farther than lava erupted from a stratovolcano, and results in the steady accumulation of broad sheets of lava, building up the shield volcano's distinctive form.

Yellowstone Caldera volcanic caldera in Yellowstone National Park in the United states

The Yellowstone Caldera is a volcanic caldera and supervolcano in Yellowstone National Park in the Western United States, sometimes referred to as the Yellowstone Supervolcano. The caldera and most of the park are located in the northwest corner of Wyoming. The major features of the caldera measure about 34 by 45 miles.

Mount Mazama complex volcano in the Cascade Range

Mount Mazama is a complex volcano in the state of Oregon, United States, in a segment of the Cascade Volcanic Arc and Cascade Range. Most of the mountain collapsed following a major eruption approximately 7,700 years ago. The volcano is in Klamath County, in the southern Cascades, 60 miles (97 km) north of the Oregon-California border. Its collapse formed a caldera that holds Crater Lake. The mountain is in Crater Lake National Park. Mount Mazama originally had an elevation of 12,000 feet (3,700 m), but following its climactic eruption this was reduced to 8,157 feet (2,486 m). Crater Lake is 1,943 feet (592 m) deep, the deepest freshwater body in the US and the second deepest in North America after Great Slave Lake in Canada.

Mount Katmai mountain

Mount Katmai is a large stratovolcano on the Alaska Peninsula in southern Alaska, located within Katmai National Park and Preserve. It is about 6.3 miles (10 km) in diameter with a central lake-filled caldera about two by three miles in size, formed during the Novarupta eruption of 1912. The caldera rim reaches a maximum elevation of 6,716 feet (2,047 m). In 1975 the surface of the crater lake was at an elevation of about 4,220 feet (1,286 m), and the estimated elevation of the caldera floor is about 3,400 ft (1,040 m). The mountain is located in Kodiak Island Borough, very close to its border with Lake and Peninsula Borough.

Ambrym volcanic island in the archipelago of Vanuatu

Ambrym is a volcanic island in Malampa Province in the archipelago of Vanuatu. Volcanic activity on the island includes lava lakes in two craters near the summit.

Kikai Caldera A mostly submerged caldera in the Ōsumi Islands of Kagoshima Prefecture, Japan.

Kikai Caldera is a massive, mostly submerged caldera up to 19 kilometres (12 mi) in diameter in the Ōsumi Islands of Kagoshima Prefecture, Japan.

Plinian eruption type of volcanic eruption

Plinian eruptions or Vesuvian eruptions are volcanic eruptions marked by their similarity to the eruption of Mount Vesuvius in 79 AD, which destroyed the ancient Roman cities of Herculaneum and Pompeii. The eruption was described in a letter written by Pliny the Younger, after the death of his uncle Pliny the Elder.

Taunshits mountain in Russia

Taunshits is a stratovolcano located in the eastern part of Kamchatka Peninsula, Russia.

Types of volcanic eruptions Basic mechanisms of eruption and variations

Several types of volcanic eruptions—during which lava, tephra, and assorted gases are expelled from a volcanic vent or fissure—have been distinguished by volcanologists. These are often named after famous volcanoes where that type of behavior has been observed. Some volcanoes may exhibit only one characteristic type of eruption during a period of activity, while others may display an entire sequence of types all in one eruptive series.

Silverthrone Caldera Stratovolcano in Canada

The Silverthrone Caldera is a potentially active caldera complex in southwestern British Columbia, Canada, located over 350 kilometres (220 mi) northwest of the city of Vancouver and about 50 kilometres (31 mi) west of Mount Waddington in the Pacific Ranges of the Coast Mountains. The caldera is one of the largest of the few calderas in western Canada, measuring about 30 kilometres (19 mi) long (north-south) and 20 kilometres (12 mi) wide (east-west). Mount Silverthrone, an eroded lava dome on the caldera's northern flank that is 2,864 metres (9,396 ft) high, may be the highest volcano in Canada.

Timeline of volcanism on Earth

This timeline of volcanism on Earth is a list of major volcanic eruptions of approximately at least magnitude 6 on the Volcanic Explosivity Index (VEI) or equivalent sulfur dioxide emission around the Quaternary period.

Kurile Lake lake in Russia

Kurile Lake is a caldera and crater lake in Kamchatka, Russia. It is also known as Kurilskoye Lake or Kuril Lake. It is part of the Eastern Volcanic Zone of Kamchatka which, together with the Sredinny Range, forms one of the volcanic belts of Kamchatka. These volcanoes form from the subduction of the Pacific Plate beneath the Okhotsk Plate and the Asian Plate.

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Further reading