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Chaitén is a volcanic
caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...
in diameter, west of the elongated ice-capped Michinmahuida volcano and northeast of the town of
Chaitén Chaitén (, ) is a Chilean List of towns in Chile, town, Communes of Chile, commune and former capital of the Palena Province in Los Lagos Region. The town is north of the mouth of Yelcho River, on the east coast of the Gulf of Corcovado. The town ...
, near the Gulf of Corcovado in southern
Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
. The most recent eruptive phase of the volcano erupted on 2008. Originally,
radiocarbon dating Radiocarbon dating (also referred to as carbon dating or carbon-14 dating) is a method for Chronological dating, determining the age of an object containing organic material by using the properties of carbon-14, radiocarbon, a radioactive Isotop ...
of older
tephra Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...
from the volcano suggested that its last previous eruption was in 7420 BC ± 75 years. However, recent studies have found that the volcano is more active than thought. According to the
Global Volcanism Program The Smithsonian Institution's Global Volcanism Program (GVP) documents Earth's volcanoes and their eruptive history during the Quaternary Period of Earth's geologic history, with particular emphasis on volcanic activity during the Holocene Epoc ...
, its last eruption was in 2011. The caldera rim reaches above sea level. Before the current eruption, it was mostly filled by a
rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...
obsidian Obsidian ( ) is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Produced from felsic lava, obsidian is rich in the lighter element ...
lava dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...
that reached a height of , partly devoid of vegetation. Two small lakes occupied the caldera floor on the west and north sides of the lava dome. The translucent grey
obsidian Obsidian ( ) is a naturally occurring volcanic glass formed when lava extrusive rock, extruded from a volcano cools rapidly with minimal crystal growth. It is an igneous rock. Produced from felsic lava, obsidian is rich in the lighter element ...
which had erupted from the volcano was used by
pre-Columbian In the history of the Americas, the pre-Columbian era, also known as the pre-contact era, or as the pre-Cabraline era specifically in Brazil, spans from the initial peopling of the Americas in the Upper Paleolithic to the onset of European col ...
cultures as a raw material for artifacts and has been found as far away as to the south and north, for example in Chan-Chan. Pino, Mario and Navarro, Rayen
Geoarqueología del sitio arcaico Chan-Chan 18
Revista Geológica de Chile, 2005.


2008 eruption

The Chaitén volcano entered a new eruptive phase for the first time since around 1640 on the morning of May 3, 2008. The Chilean government began an evacuation of the nearby town of
Chaitén Chaitén (, ) is a Chilean List of towns in Chile, town, Communes of Chile, commune and former capital of the Palena Province in Los Lagos Region. The town is north of the mouth of Yelcho River, on the east coast of the Gulf of Corcovado. The town ...
(population 4,200) and the surrounding area the same day, the main phase of which was completed by May 3, 2008. One elderly person died while at sea en route to
Puerto Montt Puerto Montt (Mapuche: Meli Pulli) is a port city and commune in southern Chile, located at the northern end of the Reloncaví Sound in the Llanquihue Province, Los Lagos Region, 1,055 km to the south of the capital, Santiago. The commune ...
. By the afternoon of May 3, the plume of ash from the eruption had spread across Chile and
Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...
to the
Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...
, contaminating water supplies, and reportedly coating the town of Futaleufú located southeast to a depth of . Ash thickness estimates are often exaggerated during volcanic crises; later field investigations suggest that the average ash thickness deposited across Futaleufú was less than . A team of scientists from the US was dispatched to the area to assess the air quality and the risks from chemicals in the falling ash. 200px, left, The Chaitén Volcano seen from a commercial flight, October 2008. The initial phase of the actual eruption in 2008 was characterised by ash emissions and seismic activity; local seismic measurements in 2005 registered earthquakes up to magnitude 3.6 MW below the Chaitén volcano. On May 6, 2008, the force of eruption increased significantly, producing
pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...
s and possibly some
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 Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
explosions, and raising the
eruption column An eruption column or eruption plume is a cloud of super-heated Volcanic ash, ash and tephra suspended in volcanic gas, gases emitted during an explosive eruption, explosive volcanic eruption. The volcanic materials form a vertical column or Plu ...
to a height of perhaps . The remaining personnel and almost all inhabitants of Chaitén and nearby villages were evacuated, as was Futaleufú. In the early phase of the eruption (May 2, 2008), two separate vents had developed in the old lava dome. An overflight on May 6, 2008, found that these had fused into one vent roughly across. OVDAS warned of possible major pyroclastic incidents, and the likelihood of prolonged activity. On May 8, 2008, the government said it would force the last residents from the danger area, but this was later legally challenged by some residents and left to no effect by the
Supreme Court In most legal jurisdictions, a supreme court, also known as a court of last resort, apex court, high (or final) court of appeal, and court of final appeal, is the highest court within the hierarchy of courts. Broadly speaking, the decisions of ...
. Government personnel later returned to attend to livestock and rescue dogs and other animals. Through the remainder of May and June 2008 the eruption continued as a variable but gradually decreasing emission of ash, with intermittent seismic activity and pyroclastic flows. On May 21, a new lava dome was observed to be forming in the crater, which by May 24 exceeded the height of the old dome. Initially, the dome extended towards the north side of the caldera, but following the emergence of two new vents in the south of the old dome around June 11 and a later one to the west, the expansion moved to the south, eventually blocking the drainage from the caldera floor. As of July 3, 2008, Chaitén continued to erupt, with associated seismic activity, an eruptive column of ash up to , and a growing lava dome. Whether the dome will be stable remains uncertain, and there is an ongoing risk of collapse and explosive pyroclastic eruption. In August 2008, an expedition reached the summit of Chaiten volcano. The summit crater contained a high lava dome. Earthquakes were felt at the summit. The lava dome was loudly degassing, and avalanches of lava boulders fell from the dome side to the crater floor. On February 19, 2009, a partial dome collapse caused pyroclastic flows to descend through the Chaitén river valley reaching down to approximately from the town of Chaitén. The ash once again reached Futaleufú and parts of Chubut province in neighboring
Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...
. The approximately 160 people that were in Chaitén were strongly urged to leave, and all but 25 people who refused to leave were evacuated that day.


Damage

Forests near the volcano have been burned by pyroclastic flows and lateral explosions. Large parts of southern Argentina and Chile have been coated with ash, with possible longer term consequences for agriculture, although not only negative as ash adds new minerals to the soil. Large amounts of ash have fallen in some areas, posing a risk of lahars for several communities. Beginning on May 12, lahars caused flooding in the town of Chaitén, depositing ash mud to a depth of up to a metre or more, damaging many buildings, and completely filling the original course of the Chaitén River past the town. Over the subsequent weeks, the river excavated a new course through Chaitén, completely destroying a significant part of it by July 2008. Some defensive work has been undertaken by the government. There were plans to move town some north but these have not been concluded as yet. The town of Chaiten is slowly recovering. Its current population is about 900 people.


Rarity

This eruption is known as the first major explosive eruption of rhyolite magma in nearly a century, since the 1912 eruption of
Novarupta Novarupta is a volcano located on the Alaska Peninsula on a slope of Trident Volcano in Katmai National Park and Preserve, about southwest of Anchorage. Novarupta was formed in 1912, during the largest volcanic eruption of the 20th century, in ...
, in
Alaska Alaska ( ) is a non-contiguous U.S. state on the northwest extremity of North America. Part of the Western United States region, it is one of the two non-contiguous U.S. states, alongside Hawaii. Alaska is also considered to be the north ...
. Although there have been rhyolitic eruptions in the southern section of the Southern Volcanic Zone in the past, these are relatively scarce and there is no historic rhyolitic eruption of the magnitude of Chaitén.


References


External links

Articles
BBC News: In pictures: Chile volcano erupts


* ttp://www.dagbladet.no/nyheter/2008/05/07/534627.html Dagbladet: Vulkanen blir sintere
SERNAGEOMIN



The Volcanism Blog – Chaitén



The story of how Chaitén volcano was discovered
Scientific Papers on the Chaitén eruption

* [https://web.archive.org/web/20110707012427/http://www.sernageomin.cl/pdf/revista/36_1/09Lara.pdf LE Lara, 2009, The 2008 eruption of the Chaitén volcano: a preliminary report, Andean Geology 36, 125–129]
SFL Watt et al., 2009, Fallout and distribution of volcanic ash over Argentina following the May 2008 explosive eruption of Chaiten, Chile, Journal of Geophysical Research (Solid Earth) 114, B04207

M Reich et al., 2009, Formation of cristobalite nanofibers during explosive volcanic eruptions, Geology 37, 435–438
Photography
BBC, November 1, 2008, Alert at smoking Chile volcano



Region de los Lagos regional government photographs of the emergency.


Webcams

( Southern Andean Volcano Observatory) {{DEFAULTSORT:Chaiten Volcano Mountains of Chile Active volcanoes Calderas of Chile Volcanic crater lakes Volcanoes of Los Lagos Region South Volcanic Zone 21st-century volcanic events Holocene calderas Lava domes of Chile