Plinian eruption

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Plinian eruption: 1: ash plume, 2: magma conduit, 3: volcanic ash fall, 4: layers of lava and ash, 5: stratum, 6: magma chamber. Plinian Eruption-numbers.svg
Plinian eruption: 1: ash plume, 2: magma conduit, 3: volcanic ash fall, 4: layers of lava and ash, 5: stratum, 6: magma chamber.
1822 artist's impression of the eruption of Mount Vesuvius in 79, depicting what the AD 79 eruption may have looked like, by the English geologist George Julius Poulett Scrope. Lightning is depicted around the rising column of ash and gas. Vesuvius1822scrope.jpg
1822 artist's impression of the eruption of Mount Vesuvius in 79, depicting what the AD 79 eruption may have looked like, by the English geologist George Julius Poulett Scrope. Lightning is depicted around the rising column of ash and gas.

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.

Contents

Plinian/Vesuvian eruptions are marked by columns of volcanic debris and hot gases ejected high into the stratosphere, the second layer of Earth's atmosphere. The key characteristics are ejection of large amount of pumice and very powerful continuous gas-driven eruptions. According to the Volcanic Explosivity Index, Plinian eruptions have a VEI of 4, 5 or 6, sub-Plinian 3 or 4, and ultra-Plinian 6, 7 or 8.

Short eruptions can end in less than a day, but longer events can continue for several days or months. The longer eruptions begin with production of clouds of volcanic ash, sometimes with pyroclastic surges. The amount of magma erupted can be so large that it depletes the magma chamber below, causing the top of the volcano to collapse, resulting in a caldera. Fine ash and pulverized pumice can deposit over large areas. Plinian eruptions are often accompanied by loud noises, such as those generated by the 1883 eruption of Krakatoa. The sudden discharge of electrical charges accumulated in the air around the ascending column of volcanic ashes also often causes lightning strikes as depicted by the English geologist George Julius Poulett Scrope in his painting of 1822.

The lava is usually dacitic or rhyolitic, rich in silica. Basaltic, low-silica lavas are unusual for Plinian eruptions; the most recent basaltic example[ citation needed ] is the 1886 eruption of Mount Tarawera on New Zealand's North Island. [1]

Pliny's description

A Stone Pine, the type of tree used by Pliny to describe the eruption. Pinien La Brena2004.jpg
A Stone Pine, the type of tree used by Pliny to describe the eruption.
April 21, 1990 eruption cloud from Redoubt Volcano as viewed to the west from the Kenai Peninsula (more than 60 km from the volcano's summit) MtRedoubtedit1.jpg
April 21, 1990 eruption cloud from Redoubt Volcano as viewed to the west from the Kenai Peninsula (more than 60 km from the volcano's summit)

Pliny described his uncle's involvement from the first observation of the eruption: [2]

On August 24th, about one in the afternoon, my mother desired him to observe a cloud which appeared of a very unusual size and shape. He had just taken a turn in the sun and, after bathing himself in cold water, and making a light luncheon, gone back to his books: he immediately arose and went out upon a rising ground from whence he might get a better sight of this very uncommon appearance. A cloud, from which mountain was uncertain, at this distance (but it was found afterwards to come from Mount Vesuvius), was ascending, the appearance of which I cannot give you a more exact description of than by likening it to that of a pine tree, for it shot up to a great height in the form of a very tall trunk, which spread itself out at the top into a sort of branches; occasioned, I imagine, either by a sudden gust of air that impelled it, the force of which decreased as it advanced upwards, or the cloud itself being pressed back again by its own weight, expanded in the manner I have mentioned; it appeared sometimes bright and sometimes dark and spotted, according as it was either more or less impregnated with earth and cinders. This phenomenon seemed to a man of such learning and research as my uncle extraordinary and worth further looking into.

Sixth Book of Letters, Letter 16, translation by William Melmoth

Pliny the Elder set out to rescue the victims from their perilous position on the shore of the Bay of Naples, and launched his galleys, crossing the bay to Stabiae (near the modern town of Castellammare di Stabia). Pliny the Younger provided an account of his death, and suggested that he collapsed and died through inhaling poisonous gases emitted from the volcano. His body was found interred under the ashes of the eruption with no apparent injuries on 26 August, after the plume had dispersed, confirming asphyxiation or poisoning.

Examples

Ultra-Plinian

According to the Volcanic Explosivity Index, a VEI of 6 to 8 is classified as "ultra-Plinian". Eruptions of this type are defined by ash plumes over 25 km (16 mi) high and a volume of erupted material 10 km3 (2 cu mi) to 1,000 km3 (200 cu mi) in size. Eruptions in the ultra-Plinian category include the Lava Creek eruption of the Yellowstone Caldera (c. 640,000 years ago, VEI 8), Lake Toba (c. 74,000 years ago, VEI 8), Tambora (1815, VEI 7), Krakatoa (1883, VEI 6), Akahoya eruption of Kikai Caldera, Japan and the 1991 Mount Pinatubo eruption in the Philippines (VEI 6). [4] [5]

See also

Related Research Articles

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Mount Vesuvius Stratovolcano in the Gulf of Naples, Italy

Mount Vesuvius is a somma-stratovolcano located on the Gulf of Naples in Campania, Italy, about 9 km (5.6 mi) east of Naples and a short distance from the shore. It is one of several volcanoes which form the Campanian volcanic arc. Vesuvius consists of a large cone partially encircled by the steep rim of a summit caldera caused by the collapse of an earlier and originally much higher structure.

Mount Tambora stratovolcano of Indonesia

Mount Tambora, or Tomboro, is an active stratovolcano in the northern part of Sumbawa, one of the Lesser Sunda Islands of Indonesia. It was formed due to the active subduction zones beneath it, and before its 1815 eruption, it was more than 4,300 metres high, making it one of the tallest peaks in the Indonesian archipelago.

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).

Novarupta mountain

Novarupta is a volcano that was formed in 1912, located on the Alaska Peninsula in Katmai National Park and Preserve, about 290 miles (470 km) southwest of Anchorage. Formed during the largest volcanic eruption of the 20th century, Novarupta released 30 times the volume of magma of the 1980 eruption of Mount St. Helens.

Katla (volcano) volcano in Iceland

Katla is a large volcano in southern Iceland. It is very active; twenty eruptions have been documented between 930 and 1918, at intervals of 20–90 years. It has not erupted violently for 102 years, although there may have been small eruptions that did not break the ice cover, including ones in 1955, 1999, and 2011.

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.

Cerro Negro mountain

Cerro Negro is an active volcano in the Cordillera de los Maribios mountain range in Nicaragua, about 10 km (6.2 mi) from the village of Malpaisillo. It is a very new volcano, the youngest in Central America, having first appeared in April 1850. It consists of a gravelly basaltic cinder cone, which contrasts greatly with the surrounding verdant hillsides, and gives rise to its name, which means Black Hill. Cerro Negro has erupted frequently since its first eruption. One unusual aspect of several eruptions has been the emission of ash from the top of the cone, while lava erupts from fractures at the base.

Mount Rinjani mountain in Indonesia

Mount Rinjani is an active volcano in Indonesia on the island of Lombok. Administratively the mountain is in the Regency of North Lombok, West Nusa Tenggara. It rises to 3,726 metres (12,224 ft), making it the second highest volcano in Indonesia.

Cerro Azul (Chile volcano) mountain in Curicó Province Chile

Cerro Azul, sometimes referred to as Quizapu, is an active stratovolcano in the Maule Region of central Chile, immediately south of Descabezado Grande. Part of the South Volcanic Zone of the Andes, its summit is 3,788 meters (12,428 ft) above sea level, and is capped by a summit crater that is 500 meters (1,600 ft) wide and opens to the north. Beneath the summit, the volcano features numerous scoria cones and flank vents.

A pyroclastic fall is a uniform deposit of material which has been ejected from a volcanic eruption or plume such as an ash fall or tuff. Pyroclastic air fall deposits are a result of:

  1. Ballistic transport of ejecta such as volcanic blocks, volcanic bombs and lapilli from volcanic explosions
  2. Deposition of material from convective clouds associated with pyroclastic flows such as coignimbrite falls
  3. Ejecta carried in gas streaming from a vent. The material under the action of gravity will settle out from an eruption plume or eruption column
  4. Ejecta settling from an eruptive plume or eruption column that is displaced laterally by wind currents and is dispersed over great distances
Lake Ilopango Crater Lake of El Salvador

Lake Ilopango is a crater lake which fills an 8 by 11 km volcanic caldera in central El Salvador, on the borders of the San Salvador, La Paz, and Cuscatlán departments. The caldera, which contains the second largest lake in the country and is immediately east of the capital city, San Salvador, has a scalloped 100 m (330 ft) to 500 m (1,600 ft) high rim. Any surplus drains via the Jiboa River to the Pacific Ocean. An eruption of the Ilopango volcano is considered a possible source for the extreme weather events of 535–536. The local military airbase, Ilopango International Airport, has annual airshows where international pilots from all over the world fly over San Salvador City and Ilopango lake.

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.

Phreatomagmatic eruption Volcanic eruption involving both steam and magma

Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions contain juvenile (magmatic) clasts. It is common for a large explosive eruption to have magmatic and phreatomagmatic components.

Mount Tarumae mountain in Hokkaido, Japan

Mount Tarumae is located in the Shikotsu-Toya National Park in Hokkaidō, Japan. It is located near both Tomakomai and Chitose towns and can be seen clearly from both. It is on the shores of Lake Shikotsu, a caldera lake. Tarumae is a 1,041 metre active andesitic stratovolcano, with a lava dome.

Volcanology of Indonesia

Indonesia is a volcanically active country, containing numerous major volcanoes. It has the most volcanoes of any country in the world, with 76 volcanoes that have erupted at least 1,171 times in total within historical times. The Smithsonian Institution has 141 Indonesian entries in its volcano database. Indonesia has around 130 active volcanoes that are part of the Pacific Ring of Fire, and it has suffered the highest numbers of eruptions resulting in fatalities, damage to arable land, debris flows, tsunamis, lava domes, and pyroclastic flows. Indonesia's most active volcanoes are Kelut and Mount Merapi on the island of Java. The majority of Indonesia's volcano are located on a 3,000 km long chain called the Sunda Arc. Here, the subduction of the Indian Ocean crust underneath the Asian Plate produced most of these volcanoes.

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.

Eruption of Mount Vesuvius in 79 Volcanic eruption in the Roman Empire

Of the many eruptions of Mount Vesuvius in Italy, the most famous is the eruption in 79 AD. This eruption is one of the deadliest in European history.

Bridge River Vent mountain in Canada

The Bridge River Vent is a volcanic crater in the Pacific Ranges of the Coast Mountains in southwestern British Columbia, Canada. It is located 51 km (32 mi) west of Bralorne on the northeastern flank of the Mount Meager massif. With an elevation of 1,524 m (5,000 ft), it lies on the steep northern face of Plinth Peak, a 2,677 m (8,783 ft) high volcanic peak comprising the northern portion of Meager. The vent rises above the western shoulder of the Pemberton Valley and represents the northernmost volcanic feature of the Mount Meager massif.

References

  1. "Okataina Volcanic Centre/ Mt Tarawera Volcano". GNS Science. Retrieved 15 January 2020.
  2. Pliny's Letters. pp. 473–481.
  3. Enlightenment activities for improvement on disasters from Tarumae Volcano, Japan, Cities on Volcanoes 4, 23–27 January 2006
  4. "How Volcanoes Work: Variability of Eruptions". San Diego State University. Retrieved 4 August 2010.
  5. Maeno F, Taniguchi H. (2005). "Eruptive History of Satsuma Iwo-jima Island, Kikai Caldera, after a 6.5ka caldera-forming eruption". Bulletin of the Volcanological Society of Japan. 50(2):71–85. ISSN   0453-4360.