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73-489: Chaitén is a volcanic caldera 3 kilometres (2 mi) in diameter, 17 kilometres (11 mi) west of the elongated ice-capped Michinmahuida volcano and 10 kilometres (6 mi) northeast of the town of Chaitén , near the Gulf of Corcovado in southern Chile . The most recent eruptive phase of the volcano erupted on 2008. Originally, radiocarbon dating of older tephra from the volcano suggested that its last previous eruption

146-458: A caldera are sometimes described as "caldera volcanoes". The term caldera comes from Spanish caldera , and Latin caldaria , meaning "cooking pot". In some texts the English term cauldron is also used, though in more recent work the term cauldron refers to a caldera that has been deeply eroded to expose the beds under the caldera floor. The term caldera was introduced into

219-409: A caldera, possibly an ash-flow caldera. 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. Mars has the tallest volcano in

292-776: A day to Buenos Aires, and to many locations in the Santa Cruz Province . Short range buses to towns in Chubut run at least once a day. There are also daily summer buses on the route #25. The Trelew airport ( IATA REL ) serves regular flights to/from Buenos Aires and El Calafate . Airports are also maintained at Comodoro Rivadavia ( General Enrique Mosconi International Airport ), Rawson and Esquel. Major highways include: Four other roads travel west to Chile's Aysén region, including Balmaceda and Coihaique Alto, and two to Chile's Los Lagos region from Corcovado to Palena and from Esquel via Trevelin to Futaleufu. The provincial government

365-400: 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. 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

438-403: 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 120 metres (390 ft) high lava dome. Earthquakes were felt at the summit. The lava dome was loudly degassing, and avalanches of lava boulders fell from

511-412: 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) 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

584-456: A lot across the province and the contrast is not that large. In the coastal areas, the mean relative humidity is about 70% while in the rest of the province, it is around 50%–60%. The exception is in the higher altitude areas in the Andes in the colder regions where humidity levels are considerably higher. During the summer months, humidity levels are relatively low. Because the Andes block most of

657-627: A national central office. The provincial government runs a TV network that covers the province. In Trelew, Comodoro Rivadavia, Esquel, Puerto Madryn and in some small towns there are other local TV stations producing local programming to supplement the programming received from the Buenos Aires networks. Tourism is also a growing industry. The main attractions are Peninsula Valdés and other marine wildlife reservoirs such as Punta Tombo and Punta Ninfas , with right whales , eared seals , elephant seals , penguins , orcas and many other animals. At

730-537: 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 3,000 metres (9,800 ft), and

803-692: A single event, it can cause catastrophic environmental effects. 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. The ecological effects of the eruption of a large caldera can be seen in the record of the Lake Toba eruption in Indonesia . 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

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876-585: A substantial part of North America in up to two metres of debris. Eruptions forming even larger calderas are known, such as the 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. The caldera produced by such eruptions is typically filled in with tuff, rhyolite , and other igneous rocks . The caldera

949-459: A west to east direction are moderated as they pass over the Pacific Ocean. As such, cold temperatures are not as extreme as they are in the northern hemisphere. Similar to the rest of Patagonia the climate is characterized by strong winds throughout the year, which also leads to higher evapotranspiration , another factor in the province being mostly dry. The western parts of the province are

1022-550: Is Comodoro Rivadavia in the south of the province; it has 180,000 inhabitants. The administrative capital is Rawson (40,000). Other important cities are Puerto Madryn , Trelew , Esquel and Sarmiento . Gaiman is a cultural and demographic centre of the region known as " Y Wladfa " in which Welsh-Argentines are concentrated. Before the Spaniards arrived in the Americas , nomadic indigenous Tehuelche people had inhabited

1095-686: Is Infochubut.com, a recent publication that works with audio, video, text and photographs for its news and offers forums for public participation. Some radio stations in northwest Chubut began to publish online some of the interviews made in their radio studies. The most populous cities are served by AM radio stations, such as Chubut Radio and Three Radio in Trelew, Golfo Nuevo's Radio in Puerto Madryn, National Radio in Comodoro, Rivadavia and Esquel. There are also several FM radio stations which broadcast programs from

1168-484: Is a transition between the more temperate climates to the north and the colder climates in the south. Summers tend to be much warmer than Santa Cruz province to the south, particularly in the summer since subtropical air from the north and a branch of the warm Brazil Current can reach the province up until 46°. Because there is little land masses in the Southern hemisphere, most of the cold fronts , which usually move in

1241-461: Is an additional factor that makes most of the province dry since it favors evaporation of moisture. Most of the wind comes from either the west, southwest or northwest but in coastal areas during the summer months, a sea breeze can form when westerly winds are weak, forming easterly winds that can penetrate up to 10 kilometres (6.2 mi) from the coast. The mean wind speed is 6 metres per second (20 ft/s) with higher wind speeds being recorded in

1314-530: Is divided into the usual three branches: the executive, headed by a popularly elected governor, who appoint the cabinet; the legislative; and the judiciary, headed by the Supreme Court and completed by several inferior tribunals. The Constitution of Chubut Province forms the formal law of the province. In Argentina, the most important law enforcement organization is the Argentine Federal Police but

1387-446: Is formed through subsidence and collapse rather than an explosion or impact. Compared to the thousands of volcanic eruptions that occur over the course of a century, the formation of a caldera is a rare event, occurring only a few times within a given window of 100 years. Only eight caldera-forming collapses are known to have occurred between 1911 and 2018, with a caldera collapse at Kīlauea , Hawaii in 2018. Volcanoes that have formed

1460-469: Is found in the area between the Andean region to the west and the dry steppes to the east. Although precipitation can widely vary among the province, in all locations, precipitation is higher during the winter months. Thunderstorms are rare and occur exclusively during the summer. One defining characteristic of the climate in Chubut province is the strong wind that is observed throughout the province. The wind

1533-463: Is generated by mining and petroleum. This sector's contribution (mostly centered around Comodoro Rivadavia ) helped give Chubut the nation's fourth-highest per capita output in 2011, US$ 25,250. Petroleum refining is the main economic activity of the province; it generates 13% of Argentine oil production (mostly off-shore). On May 21, 2014, Miguel Galuccio of YPF and Chubut Governor Martin Buzzi announced

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1606-558: 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. Chubut Province The largest city

1679-521: Is slowly recovering. Its current population is about 900 people. This eruption is known as the first major explosive eruption of rhyolite magma in nearly a century, since the 1912 eruption of Novarupta , in Alaska . 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

1752-586: Is surrounded by an outflow sheet of ash flow tuff (also called an ash flow sheet ). If magma continues to be injected into the collapsed magma chamber, the center of the caldera may be uplifted in the form of a resurgent dome such as is seen at the Valles Caldera , Lake Toba , the San Juan volcanic field, Cerro Galán , Yellowstone , and many other calderas. Because a silicic caldera may erupt hundreds or even thousands of cubic kilometers of material in

1825-517: The Comodoro Rivadavia Military Zone . The zone was dissolved in 1955, and Chubut was declared a province. Studies in the 1950s revealed mineral wealth in the province, which the government has tried to develop. Population shifts of the late 20th century, especially from Buenos Aires , raised the population steadily from 190,000 (1970), to 357,000 (1991) and 413,237 (2001). The government has encouraged people to resettle here. Most of

1898-751: The Eocene Rum Complex of Scotland, 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). For their 1968 paper that first introduced the concept of a resurgent caldera to geology, R.L. Smith and R.A. Bailey chose the Valles caldera as their model. Although

1971-628: The Patagonia region for thousands of years. They lived as hunter-gatherers and covered territory in seasonal cycles as they followed game. In the 17th and 18th centuries, Spanish missionaries came to the area, and founded the San José Fort on Península Valdés . The indigenous people later destroyed it. In 1865, Welsh people came to Chubut on the Mimosa and settled in the Chubut Valley . The region

2044-473: The eruption column to a height of perhaps 30,000 metres (98,000 ft). 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 800 metres (2,600 ft) across. OVDAS warned of possible major pyroclastic incidents, and

2117-590: The Chilean border. The Andes are not that high in Chubut, with most peaks averaging around 1,500 and 2,000 metres (4,900 and 6,600 ft), which becomes smaller in altitude in the southern parts. The highest peak is Cerro Dos Picos , located east of Lago Cholila with a height of 2,515 metres (8,251 ft). The Andes in this province are of tertiary origin and are separated by wide, deep transverse valleys that are oriented in an east–west direction. These valleys are occupied by glacial lakes and rivers flowing east from

2190-465: The Earth's volcanic activity (the other 40% is attributed to hotspot volcanism). 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

2263-510: The Moon have been well preserved through time and were once thought to have been the result of extreme volcanic activity, but are currently believed to have been 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

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2336-754: The Punta Tombo site there is one of the largest breeding areas for the Magellanic penguin . Further south, on the sparsely populated beaches of the Golfo San Jorge , is the only place in the world where the peculiar, flightless Chubut steamer duck can be observed. In the Andean region, the Los Alerces National Park , impressive lakes and hikes near Esquel are also visited every year by many tourists. The ' Old Patagonian Express ' (also known as La Trochita ),

2409-720: 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. 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. Io, unusually,

2482-526: The Valles caldera is not unusually large, it is relatively young (1.25 million years old) and unusually well preserved, and it remains one of the best studied examples of a resurgent caldera. The ash flow tuffs of the Valles caldera, such as the Bandelier Tuff , were among the first to be thoroughly characterized. About 74,000 years ago, this Indonesian volcano released about 2,800 cubic kilometres (670 cu mi) dense-rock equivalent of ejecta. This

2555-721: The additional work is carried out by the Chubut Provincial Police . The province is divided into 15 departments (Spanish: departamentos ), listed below with their Number (on map), area and populations at the Censuses of November 2000 and October 2010: Chubut is covered by the Roman Catholic Diocese of Comodoro Rivadavia . The cathedral, dedicated to San Juan Bosco is in Comodoro Rivadavia. The university, Universidad Nacional de la Patagonia San Juan Bosco ,

2628-411: 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. 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

2701-577: The caldera atop Fernandina Island collapsed in 1968 when parts of the caldera floor dropped 350 metres (1,150 ft). 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 crewed and uncrewed 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

2774-458: The caldera floor on the west and north sides of the lava dome. The translucent grey obsidian which had erupted from the volcano was used by pre-Columbian cultures as a raw material for artifacts and has been found as far away as 400 kilometres (250 mi) to the south and north, for example in Chan-Chan . The Chaitén volcano entered a new eruptive phase for the first time since around 1640 on

2847-593: The caldera, forming hydrothermal ore deposits of metals such as lead, silver, gold, mercury, lithium, and uranium. One of the world's best-preserved mineralized calderas is the Sturgeon Lake Caldera in northwestern Ontario , Canada, which formed during the Neoarchean era about 2.7 billion years ago. In the San Juan volcanic field , ore veins were emplaced in fractures associated with several calderas, with

2920-404: The coldest with an annual mean temperature of 8 °C (46.4 °F) owing to the higher elevations while the coastal areas are the warmest with an annual mean temperature of 12 to 14 °C (53.6 to 57.2 °F). The central parts of the province have an annual mean temperature of 10 to 12 °C (50.0 to 53.6 °F) since they have a higher elevation than the coastal areas. During winter,

2993-542: 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 5 kilometres (3 mi) from the town of Chaitén. The ash once again reached Futaleufú and parts of Chubut province in neighboring Argentina . 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. Forests near

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3066-581: 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 of square kilometers. Some calderas are known to host rich ore deposits . Metal-rich fluids can circulate through

3139-565: The eruption column is unable to entrain enough air to remain buoyant, and the eruption column collapses into a tephra fountain that falls back to the surface to form pyroclastic flows . Eruptions of this type can spread ash over vast areas, so that ash flow tuffs emplaced by silicic caldera eruptions are the only volcanic product with volumes rivaling those of flood basalts . For example, when Yellowstone Caldera last erupted some 650,000 years ago, it released about 1,000 km of material (as measured in dense rock equivalent (DRE)), covering

3212-544: The first unconventional oil and gas discovery in Chubut from a fracked well in the Early Cretaceous D-129 formation of the Golfo San Jorge basin. Chubut produces 21% of the nation's fish catch. Sheep ranching, though less than half as productive in the 21st century compared to as recently as 1990, remains important at the local level. The advent of synthetic replacements to wool after World War II battered

3285-620: The geological vocabulary by the German geologist Leopold von Buch when he published his memoirs of his 1815 visit to the Canary Islands , where he first saw the Las Cañadas caldera on Tenerife , with Mount Teide dominating the landscape, and then the Caldera de Taburiente on La Palma . A collapse is triggered by the emptying of the magma chamber beneath the volcano, sometimes as the result of

3358-430: The greatest mineralization taking place near the youngest and most silicic intrusions associated with each caldera. Explosive caldera eruptions are produced by a magma chamber whose magma is rich in silica . Silica-rich magma has a high viscosity , and therefore does not flow easily like basalt . The magma typically also contains a large amount of dissolved gases, up to 7 wt% for the most silica-rich magmas. When

3431-463: The human species was reduced to approximately 5,000–10,000 people. 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. There is evidence that human habitation continued in India after the eruption. Some volcanoes, such as the large shield volcanoes Kīlauea and Mauna Loa on

3504-514: The inhabitants are in the main cities. They have also settled along the Chubut River . Most areas have a population density of less than 1 inhabitant per square kilometer. Chubut's economy, for a long time one of the most prosperous in Argentina, is one of the country's least diversified. Nearly one-quarter of its 2006 output, estimated at US$ 4.652 billion (or a per capita income of US$ 11,256),

3577-429: 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,

3650-575: 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 . 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,

3723-401: The magma approaches the surface of the Earth, the drop in confining pressure causes the trapped gases to rapidly bubble out of the magma, fragmenting the magma to produce a mixture of volcanic ash and other tephra with the very hot gases. The mixture of ash and volcanic gases initially rises into the atmosphere as an eruption column . However, as the volume of erupted material increases,

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3796-446: The magnitude of Chaitén. Articles Scientific Papers on the Chaitén eruption Photography Webcams Caldera A caldera ( / k ɔː l ˈ d ɛr ə , k æ l -/ kawl- DERR -ə, kal- ) 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

3869-515: The mean temperature in the coldest months ranges from 6 to 7 °C (42.8 to 44.6 °F) in the northern parts of the province to 4 to 7 °C (39.2 to 44.6 °F) in the southern parts. In the Andes, the mean temperature can be close to 0 °C (32.0 °F). Unlike the northern hemisphere, most of the cold air masses originate from the Pacific Ocean, which moderates the cold air and as such, extreme cold temperatures are rare. Occasionally, cold air masses from Antarctica are not moderated by

3942-594: The moisture from the Pacific Ocean from coming in, causing it to release most of the precipitation on its western slopes, most of the province is dry, averaging less than 200 mm (7.9 in) a year. In the central parts of the province, some areas receive less than 100 mm (3.9 in) of precipitation a year. In the Andean part, precipitation increases towards the Chilean border and precipitation ranges from 700 mm (28 in) to over 3,000 mm (120 in). A Mediterranean like precipitation pattern, similar to central Chile with dry summers and wet winters

4015-465: The moisture precipitates on the western side of the Andes, leaving all except the Andean portion of the province dry. In the Andean region, the climate is cold for its latitude owing to the higher elevations there and the influence of winds from the Pacific Ocean. The peaks are usually snow covered throughout the year. In this region, precipitation ranges from 700 mm (28 in) to over 2,500 mm (98 in) in some areas. The central parts of

4088-518: The morning of May 3, 2008. The Chilean government began an evacuation of the nearby town of Chaitén (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 . By the afternoon of May 3, the plume of ash from the eruption had spread across Chile and Argentina to the Atlantic Ocean , contaminating water supplies, and reportedly coating

4161-422: The mountains. Most of these valleys existed before the Andes were formed. The lakes, which are mostly located in the western parts of the province are of glacial origin because during the last ice age , the movement of the glaciers lead to the formation of extensive areas of depressions that were filled up with water to form the lakes today. The Andes cause humid winds from the Pacific Ocean to rise so most of

4234-507: The north. The westernmost parts of the province are the coolest during the summer, averaging only 14 °C (57.2 °F). The central parts of the province have the most extreme temperatures which can reach over 40 °C (104.0 °F) during the summer and below −20 °C (−4.0 °F) in the winter. The lowest temperature recorded in Chubut was −33 °C (−27.4 °F) in Sarmiento. In general, relative humidity values do not vary

4307-412: The ocean, resulting in very cold temperatures. During summer, the temperature gradient is greater than in the winter. The northern parts of the province, have a mean temperature greater than 20 °C (68.0 °F) in the warmest months while in the southern parts, the mean temperature in the warmest month ranges from 17 to 19 °C (62.6 to 66.2 °F) owing to the influence of subtropical air from

4380-557: The old steam train made famous by Paul Theroux , attracts many to Esquel , as does the La Hoya ski center. The petrified forest near Sarmiento is a 150 km park with some of the largest fossilised trees in the world. The Ruta Nacional 3 runs along the coast line up to Buenos Aires , and down to Tierra del Fuego . The Ruta Nacional 25 crosses Chubut from East to West, connecting Trelew and Esquel , but half of it has not yet been paved. Regular long-distance buses run several times

4453-421: The province can receive 10 hours of sunshine/day while southern parts receive 8 hours of sunshine/day. During winter months, the province receives 4–5 hours of sunshine/day. Print newspapers include: Online journalism has a small, growing presence in Chubut. The six print newspapers have online editions; these are updated every 24 hours. Some new digital proposals make a better use of web's potential. One case

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4526-420: The province have an arid climate with hot, sunny summers but cold winters and only average 200 mm (7.9 in) of precipitation a year. The central parts of the province are very windy throughout the year. The coast has an arid or semi-arid climate with hot, but short summers and cold winters. It is the mildest region in the province with the warmest annual mean temperatures. The coast region's climate

4599-402: The risks from chemicals in the falling ash. 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 flows and possibly some lava explosions, and raising

4672-459: The sector. It declined further because of Argentina's political instability and damage from natural disasters. Wool production has risen since 2002, however, and totaled 71,000 tons in 2006. Chubut stretches from the Atlantic to the Andes with 3 distinct environmental regions: The Andes, the central plains and the coastal regions. The Andes in the westernmost parts of the province mostly extend along

4745-420: The south where the average is more than 9 metres per second (30 ft/s). Higher altitude areas are more windy than lower altitude areas, resulting in the Andean region being windier than the coastal areas. As in much of Patagonia, summers tend to be windier than winters. Sunshine in the province follows a north–south gradient (decreases from north to south), particularly during summer where northern parts of

4818-416: The structural integrity of such a chamber, greatly diminishing its capacity to support its own roof, and any substrate or rock resting above. The ground surface then collapses into the emptied or partially emptied magma chamber, leaving a large 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

4891-453: The town of Futaleufú located 75 kilometres (47 mi) southeast to a depth of 30 centimetres (12 in). Ash thickness estimates are often exaggerated during volcanic crises; later field investigations suggest that the average ash thickness deposited across Futaleufú was less than 5–10 cm (2–4 in). A team of scientists from the US was dispatched to the area to assess the air quality and

4964-562: 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 10 kilometres (6 mi) north but these have not been concluded as yet. The town of Chaiten

5037-413: 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

5110-694: Was disputed between Chile and Argentina until 1881. Chile renounced its claim in order to prevent Argentina from entering into the War of the Pacific , in which it was already fighting against Peru and Bolivia. As part of the Conquista del Desierto (Conquest of the Desert), Argentina organized the National Territory of Chubut in 1884, after the last indigenous cacique, Inacayal , surrendered to government forces. Luis Fontana

5183-522: 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 , its last eruption was in 2011. The caldera rim reaches 1,122 metres (3,681 ft) above sea level. Before the current eruption, it was mostly filled by a rhyolite obsidian lava dome that reached a height of 962 metres (3,156 ft), partly devoid of vegetation. Two small lakes occupied

5256-465: Was named governor. At the beginning of the 20th century, after the Boer War , some Boer people settled in the town of Sarmiento and in lesser number in other nearby towns. From 1895 to 1915 hundreds of Spanish and Italian born immigrantes settled in the lower Chubut valley as well a little more than hundred Chileans. In 1944, the southern part of Chubut and northern part of Santa Cruz were designated

5329-464: 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 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

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