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85-711: Puyehue ( / p ʊ ˈ j eɪ w eɪ / ; Spanish pronunciation: [puˈʝewe] ) and Cordón Caulle / k ɔːr ˈ d oʊ n ˈ k aʊ j eɪ / are two coalesced volcanic edifices that form a major mountain massif in Puyehue National Park in the Andes of Ranco Province , in the South of Chile. In volcanology this group is known as the Puyehue-Cordón Caulle Volcanic Complex ( PCCVC ). Four volcanoes constitute

170-645: A ghost town ) and Fourpeaked Mountain in Alaska, which, before its September 2006 eruption, had not erupted since before 8000 BCE. Puyehue Lake Puyehue is a lake of glacial origin. Several times during the Pleistocene glaciations , the lake depression was occupied by a large glacial lobe of the Patagonian Ice Sheet , which formed a series of moraines along its western shore. The lake has an east–west elongated shape with Fresia Island in

255-886: A mid-ocean ridge , such as the Mid-Atlantic Ridge , has volcanoes caused by divergent tectonic plates whereas the Pacific Ring of Fire has volcanoes caused by convergent tectonic plates. Volcanoes can also form where there is stretching and thinning of the crust's plates, such as in the East African Rift , the Wells Gray-Clearwater volcanic field , and the Rio Grande rift in North America. Volcanism away from plate boundaries has been postulated to arise from upwelling diapirs from

340-545: A sub-plinian style creating a column of volcanic gas , pyroclasts and ash about 8 km in height. The erupting N135° trending fissure had two craters of major activity emplaced at each end; the Gris Crater and El Azufral Crater. Volcanic vents of Cordón Caulle that were not in eruption produced visible steam emissions. After this explosive phase the eruption changed character to a more effusive one marked by rhyodacitic blocky and Aa type lava flows emitted from

425-437: A graduated spectrum, with much overlap between categories, and does not always fit neatly into only one of these three separate categories. The USGS defines a volcano as "erupting" whenever the ejection of magma from any point on the volcano is visible, including visible magma still contained within the walls of the summit crater. While there is no international consensus among volcanologists on how to define an active volcano,

510-504: A more superficial steam heated aquifer . The temperatures of the vapour systems range from 260 to 340 °C (500 to 644 °F) and 150–180 °C (302–356 °F) for the aquifer. The uppermost part of the geothermal system, at 1,500–2,000 m (4,900–6,600 ft), is characterized by fumaroles and acid- sulfate springs. Cordón Caulle is considered one of the main sites of geothermal exploration in Chile. Volcano A volcano

595-443: A paper was published suggesting a new definition for the word 'volcano' that includes processes such as cryovolcanism . It suggested that a volcano be defined as 'an opening on a planet or moon's surface from which magma , as defined for that body, and/or magmatic gas is erupted.' This article mainly covers volcanoes on Earth. See § Volcanoes on other celestial bodies and cryovolcano for more information. The word volcano

680-543: A sequence of strong eruptions that were part of an explosive eruptive cycle. These last eruptions were likely of phreatomagmatic and sub-plinian type and occurred around 1,100 years ago (~850 CE). Eruptive records in Cordón Caulle, the only active centre in the Puyehue-Cordón Caulle system in historical times, are relatively scarce. This is explained by the geographical position of Cordón Caulle and

765-579: A time meltwater from the Rupanco glacier flowed north into Puyehue Lake. The 2011 Puyehue Volcano eruption polluted the Golgol River , a source of the lake, killing fish. Pyroclastic material reached Puyehue Lake through river transport, which resulted in the deposition of a layer of volcanic ash at the bottom of the lake. In the 16th century the lake was known to the Spanish as Llobén , from

850-632: A volcano is largely determined by the composition of the lava it erupts. The viscosity (how fluid the lava is) and the amount of dissolved gas are the most important characteristics of magma, and both are largely determined by the amount of silica in the magma. Magma rich in silica is much more viscous than silica-poor magma, and silica-rich magma also tends to contain more dissolved gases. Lava can be broadly classified into four different compositions: Mafic lava flows show two varieties of surface texture: ʻAʻa (pronounced [ˈʔaʔa] ) and pāhoehoe ( [paːˈho.eˈho.e] ), both Hawaiian words. ʻAʻa

935-555: A volcano is of a conical mountain, spewing lava and poisonous gases from a crater at its summit; however, this describes just one of the many types of volcano. The features of volcanoes are varied. The structure and behaviour of volcanoes depend on several factors. Some volcanoes have rugged peaks formed by lava domes rather than a summit crater while others have landscape features such as massive plateaus . Vents that issue volcanic material (including lava and ash ) and gases (mainly steam and magmatic gases) can develop anywhere on

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1020-465: A volcano that has experienced one or more eruptions that produced over 1,000 cubic kilometres (240 cu mi) of volcanic deposits in a single explosive event. Such eruptions occur when a very large magma chamber full of gas-rich, silicic magma is emptied in a catastrophic caldera -forming eruption. Ash flow tuffs emplaced by such eruptions are the only volcanic product with volumes rivalling those of flood basalts . Supervolcano eruptions, while

1105-739: Is a volcanic field of over 60 cinder cones. Based on satellite images, it has been suggested that cinder cones might occur on other terrestrial bodies in the Solar system too; on the surface of Mars and the Moon. Stratovolcanoes (composite volcanoes) are tall conical mountains composed of lava flows and tephra in alternate layers, the strata that gives rise to the name. They are also known as composite volcanoes because they are created from multiple structures during different kinds of eruptions. Classic examples include Mount Fuji in Japan, Mayon Volcano in

1190-445: 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. The process that forms volcanoes is called volcanism . On Earth, volcanoes are most often found where tectonic plates are diverging or converging , and because most of Earth's plate boundaries are underwater, most volcanoes are found underwater. For example,

1275-412: Is characterized by a rough, clinkery surface and is the typical texture of cooler basalt lava flows. Pāhoehoe is characterized by its smooth and often ropey or wrinkly surface and is generally formed from more fluid lava flows. Pāhoehoe flows are sometimes observed to transition to ʻaʻa flows as they move away from the vent, but never the reverse. More silicic lava flows take the form of block lava, where

1360-565: Is derived from the name of Vulcano , a volcanic island in the Aeolian Islands of Italy whose name in turn comes from Vulcan , the god of fire in Roman mythology . The study of volcanoes is called volcanology , sometimes spelled vulcanology . According to the theory of plate tectonics, Earth's lithosphere , its rigid outer shell, is broken into sixteen larger and several smaller plates. These are in slow motion, due to convection in

1445-584: Is expressed using the volcanic explosivity index (VEI), which ranges from 0 for Hawaiian-type eruptions to 8 for supervolcanic eruptions. As of December 2022 , the Smithsonian Institution 's Global Volcanism Program database of volcanic eruptions in the Holocene Epoch (the last 11,700 years) lists 9,901 confirmed eruptions from 859 volcanoes. The database also lists 1,113 uncertain eruptions and 168 discredited eruptions for

1530-437: Is located in the southeast, Cordón Caulle in the center, and Cordillera Nevada, which owes its name to its often snowy appearance from the relatively densely populated Chilean Central Valley , is at the northwestern end. The massif is located between two lakes, Ranco Lake in the north and Puyehue Lake in the south. The fact that Puyehue volcano is named after Puyehue Lake reflects that it is better seen and more accessible from

1615-414: Is mostly made up of Nothofagus pumilio . Above this line lies a volcanic desert and alpine tundras . The main plant species present in these high elevations are Gaultheria mucronata , Empetrum rubrum , Hordeum comosum and Cissus striata . The volcanic complex that comprises Puyehue, Cordón Caulle and Cordillera Nevada has a long record of active history spanning from 300,000 years ago to

1700-537: Is one of the several tuyas in the area of the Tuya River and Tuya Range in northern British Columbia. Tuya Butte was the first such landform analysed and so its name has entered the geological literature for this kind of volcanic formation. The Tuya Mountains Provincial Park was recently established to protect this unusual landscape, which lies north of Tuya Lake and south of the Jennings River near

1785-471: Is typically low in silica, shield volcanoes are more common in oceanic than continental settings. The Hawaiian volcanic chain is a series of shield cones, and they are common in Iceland , as well. Lava domes are built by slow eruptions of highly viscous lava. They are sometimes formed within the crater of a previous volcanic eruption, as in the case of Mount St. Helens , but can also form independently, as in

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1870-593: The Carrán crater were found without activity. From accounts of local inhabitants of the area it is inferred that a small pumice cone was formed around 1990. In 1994 a temporarily emplaced seismic network registered tremors north of Puyehue's cone which reached IV and V degrees on the Mercalli intensity scale . This prompted ONEMI to invoke an emergency action committee, however soon afterward unrest ceased. Between 4 and 17 May 2011 seismic activity partly attributed to

1955-617: The Cascade Volcanoes or the Japanese Archipelago , or the eastern islands of Indonesia . Hotspots are volcanic areas thought to be formed by mantle plumes , which are hypothesized to be columns of hot material rising from the core-mantle boundary. As with mid-ocean ridges, the rising mantle rock experiences decompression melting which generates large volumes of magma. Because tectonic plates move across mantle plumes, each volcano becomes inactive as it drifts off

2040-804: The core–mantle boundary , 3,000 kilometres (1,900 mi) deep within Earth. This results in hotspot volcanism , of which the Hawaiian hotspot is an example. Volcanoes are usually not created where two tectonic plates slide past one another. Large eruptions can affect atmospheric temperature as ash and droplets of sulfuric acid obscure the Sun and cool Earth's troposphere . Historically, large volcanic eruptions have been followed by volcanic winters which have caused catastrophic famines. Other planets besides Earth have volcanoes. For example, volcanoes are very numerous on Venus. Mars has significant volcanoes. In 2009,

2125-834: The landform and may give rise to smaller cones such as Puʻu ʻŌʻō on a flank of Kīlauea in Hawaii. Volcanic craters are not always at the top of a mountain or hill and may be filled with lakes such as with Lake Taupō in New Zealand. Some volcanoes can be low-relief landform features, with the potential to be hard to recognize as such and be obscured by geological processes. Other types of volcano include cryovolcanoes (or ice volcanoes), particularly on some moons of Jupiter , Saturn , and Neptune ; and mud volcanoes , which are structures often not associated with known magmatic activity. Active mud volcanoes tend to involve temperatures much lower than those of igneous volcanoes except when

2210-584: The Cordón Caulle area. From the relatively flat Cordón Caulle there is further ca 600 m of ascent over tephra and loose rocks to the summit of Puyehue. In the Nilahue area there are arrieros who offer horseback trips to Cordón Caulle. Puyehue, Cordón del Caulle, and Cordillera Nevada form a northwest trending massif in the Ranco Province of the Andes. The three volcanoes are coalesced . Puyehue

2295-711: The Llanquihue glaciation Puyehue volcano produced some of the most primitive basalts of the Southern Volcanic Zone with a magnesium oxide mass percentage of 14.32, which is in equilibrium with melt from mantle peridotite . Only Puyehue and Cordón Caulle have erupted during the Holocene , and until 2011 only Cordón Caulle had recorded historical eruptions. In the interval between 7,000 and 5,000 years ago Puyehue had rhyolitic eruptions that produced lava domes . The lava domes were later destroyed after

2380-457: The Llanquihue glaciation volcanism occurred on all three vents, Cordillera Nevada, Cordón Caulle and Puyehue volcano. During most of this time the volcano was covered by the Patagonian Ice Sheet , leaving glacial striae on many lava outcrops and affecting the volcanic activity. In Cordillera Nevada this volcanism was expressed from about 117,000 years ago primarily as dacitic lava flows erupted along ring faults . These lava flows partly filled

2465-622: The Philippines, and Mount Vesuvius and Stromboli in Italy. Ash produced by the explosive eruption of stratovolcanoes has historically posed the greatest volcanic hazard to civilizations. The lavas of stratovolcanoes are higher in silica, and therefore much more viscous, than lavas from shield volcanoes. High-silica lavas also tend to contain more dissolved gas. The combination is deadly, promoting explosive eruptions that produce great quantities of ash, as well as pyroclastic surges like

2550-483: The Puyehue-Cordón Caulle. Yet these rocks were imported by humans to the site as nearby rivers have not transported them. From the south, the Cordón Caulle can be approached from Fundo El Caulle on Route 215-CH , which goes from Osorno to Bariloche in Argentina through Samoré Pass . Some 1,000 m up on forested slope there is a campsite and mountain shelter . According to the homepage of Puyehue National Park

2635-483: The Southern Hemisphere; scientists expected intensifying eruptions of Puyehue in the following days, and said the volcano showed no signs of slowing down. Cordón Caulle is a major area of geothermal activity , as manifested by the several hot springs , boiling springs, solfataras and fumaroles that develop on it. The geothermal system in Cordón Caulle consists of a vapour dominated system overlain by

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2720-613: The USGS defines a volcano as active whenever subterranean indicators, such as earthquake swarms , ground inflation, or unusually high levels of carbon dioxide or sulfur dioxide are present. The USGS defines a dormant volcano as any volcano that is not showing any signs of unrest such as earthquake swarms, ground swelling, or excessive noxious gas emissions, but which shows signs that it could yet become active again. Many dormant volcanoes have not erupted for thousands of years, but have still shown signs that they may be likely to erupt again in

2805-510: The boundary with the Yukon Territory . Mud volcanoes (mud domes) are formations created by geo-excreted liquids and gases, although several processes may cause such activity. The largest structures are 10 kilometres in diameter and reach 700 meters high. The material that is expelled in a volcanic eruption can be classified into three types: The concentrations of different volcanic gases can vary considerably from one volcano to

2890-523: The caldera and flowed north, out to what is now Nilahue River . In mid or late glacial times cordillera Nevada produced its last lavas which were andesitic to dacitic in composition. Cordón Caulle evolved during this time from being a shield volcano to a graben with fissure vents . This was accompanied by emission of ignimbrites and dacitic lava flows. Puyehue was characterized by eruption of basaltic andesites to dacites until its activity turned bimodal at around 34,000 years ago. The onset of this change

2975-402: The case of Lassen Peak . Like stratovolcanoes, they can produce violent, explosive eruptions, but the lava generally does not flow far from the originating vent. Cryptodomes are formed when viscous lava is forced upward causing the surface to bulge. The 1980 eruption of Mount St. Helens was an example; lava beneath the surface of the mountain created an upward bulge, which later collapsed down

3060-420: The city of Bariloche , Argentina, where the local airport was closed. At approximately 16:30 local time, Neuquén airport further east in Argentina was also closed due to the ash cloud. Airports as far away as Buenos Aires and Melbourne, Australia , had to be closed temporarily due to volcanic ash. By 15 June a dense column of ash was still erupting 10 km into the air, with the ash cloud spreading across

3145-409: The end of the 1960 eruption, Cordón Caulle has remained relatively quiet if compared with the first half of the 20th century. On 2 March 1972 there was a report of an eruption west of Bariloche in Argentina. The Chilean emergency office ONEMI (Oficina Nacional de Emergencia del Ministerio del Interior) organized a flight over the area with two volcanologists aboard. Puyehue and Cordón Caulle as well

3230-799: The enormous area they cover, and subsequent concealment under vegetation and glacial deposits, supervolcanoes can be difficult to identify in the geologic record without careful geologic mapping . Known examples include Yellowstone Caldera in Yellowstone National Park and Valles Caldera in New Mexico (both western United States); Lake Taupō in New Zealand; Lake Toba in Sumatra , Indonesia; and Ngorongoro Crater in Tanzania. Volcanoes that, though large, are not large enough to be called supervolcanoes, may also form calderas in

3315-419: The eruption had few eyewitnesses and received little attention by local media due to the huge damages and losses caused by the main earthquake. The eruption was fed by a 5.5 km (3 mi) long and north west-west (N135°) trending fissure along which 21 individual vents have been found. These vents produced an output of about 0.25 km DRE both in form of lava flows and tephra . The eruption began in

3400-610: The existence of the Little Ice Age in the Southern Hemisphere . A longer sediment core from the same site was used to reconstruct the evolution of the lake and its drainage basin during the last 18,000 years. At the time the glacier occupying the Puyhue basin had retreated during deglaciation as to calv at a proglacial Puyehue Lake the glacier at Rupanco basin (40°49' S) was at its maximum extent. For

3485-431: The flow is covered with angular, vesicle-poor blocks. Rhyolitic flows typically consist largely of obsidian . Tephra is made when magma inside the volcano is blown apart by the rapid expansion of hot volcanic gases. Magma commonly explodes as the gas dissolved in it comes out of solution as the pressure decreases when it flows to the surface . These violent explosions produce particles of material that can then fly from

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3570-610: The formation of a submarine volcano off the coast of Mayotte . Subglacial volcanoes develop underneath ice caps . They are made up of lava plateaus capping extensive pillow lavas and palagonite . These volcanoes are also called table mountains, tuyas , or (in Iceland) mobergs. Very good examples of this type of volcano can be seen in Iceland and in British Columbia . The origin of the term comes from Tuya Butte , which

3655-585: The future. In an article justifying the re-classification of Alaska's Mount Edgecumbe volcano from "dormant" to "active", volcanologists at the Alaska Volcano Observatory pointed out that the term "dormant" in reference to volcanoes has been deprecated over the past few decades and that "[t]he term "dormant volcano" is so little used and undefined in modern volcanology that the Encyclopedia of Volcanoes (2000) does not contain it in

3740-466: The glossaries or index", however the USGS still widely employs the term. Previously a volcano was often considered to be extinct if there were no written records of its activity. Such a generalization is inconsistent with observation and deeper study, as has occurred recently with the unexpected eruption of the Chaitén volcano in 2008. Modern volcanic activity monitoring techniques, and improvements in

3825-405: The history of Spanish and Chilean settlement in southern Chile. After a failed attempt in 1553, governor García Hurtado de Mendoza founded the city of Osorno in 1558, the only Spanish settlement in the zone, 80 km (50 mi) west of Cordón Caulle. This settlements had to be abandoned in 1602 due to conflicts with native Huilliches . No eruption record is known from this era. From 1602 to

3910-492: The interior of a continent and lead to rifting. Early stages of rifting are characterized by flood basalts and may progress to the point where a tectonic plate is completely split. A divergent plate boundary then develops between the two halves of the split plate. However, rifting often fails to completely split the continental lithosphere (such as in an aulacogen ), and failed rifts are characterized by volcanoes that erupt unusual alkali lava or carbonatites . Examples include

3995-494: The largest recorded earthquake in history. Apart from this, the Puyehue-Cordón Caulle area is one of the main sites of exploration for geothermal power in Chile. Geothermal activity is manifested on the surface of Puyehue and Cordón Caulle as several boiling springs and fumaroles . Most of the stone artifacts found in Pilauco Bajo (dated to c. 12.5 to 13.5 ka BP) are made of dacite , rhyodacite and rhyolite from

4080-564: The local landscape and produced a huge variety of volcanic landforms and products over the last 300,000 years. Cinder cones , lava domes , calderas and craters can be found in the area apart from the widest variety of volcanic rocks in all the Southern Zone, for example both primitive basalts and rhyolites . Cordón Caulle erupted shortly after the Great Chilean Earthquake . With a magnitude of 9.5, it remains

4165-554: The main fault of the Liquiñe-Ofqui Fault Zone . Its cone hosts a 2.4 km (1.5 mi) wide crater, and products of Puyehue volcanism cover an approximate area of 160 km (62 sq mi). The lower parts of the mountains are covered by an alpine plant association of Valdivian temperate rainforest , where plant species such as Chusquea coleou and Nothofagus dombeyi are common. The tree line , lying around 1,500 m (4,921 ft) elevation,

4250-400: The main shock of the 1960 Valdivia earthquake , the largest earthquake recorded in history, Cordón Caulle erupted . The eruption was believed to have been caused by the earthquake. The earthquake had struck the whole of Chile between Talca (30°S) and Chiloé (43°S) and had an estimated moment magnitude of 9.5. Being located between two sparsely populated and by then isolated Andean valleys

4335-583: The mid-18th century there were no Spanish settlements within a radius of 100 km (62 mi). The closest were Valdivia and the sporadic missions of Nahuel Huapi all of them out of sight of the volcano. In 1759 an eruption was noticed in the Cordillera, although this is mainly attributed to Mocho . By the end of the 19th century most of the Central Valley west of Cordón Caulle had been settled by Chileans and European immigrants and an eruption

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4420-419: The mid-oceanic ridge is above sea level, volcanic islands are formed, such as Iceland . Subduction zones are places where two plates, usually an oceanic plate and a continental plate, collide. The oceanic plate subducts (dives beneath the continental plate), forming a deep ocean trench just offshore. In a process called flux melting , water released from the subducting plate lowers the melting temperature of

4505-488: The middle and two minor peninsulas pointing toward the island, one from the north and one from the south. The lake has a remarkably smooth shoreline, with only one inlet of significance: Futacullín Bay on the south. Entre Lagos at the western end is the only town on the lake. As with most other lakes of southern Chile , Puyehue Lake acts as a sediment trap for material from the Andes. Sediment cores taken from Puyehue Lake in 2001 and 2002 have been interpreted as supporting

4590-551: The modelling of the factors that produce eruptions, have helped the understanding of why volcanoes may remain dormant for a long time, and then become unexpectedly active again. The potential for eruptions, and their style, depend mainly upon the state of the magma storage system under the volcano, the eruption trigger mechanism and its timescale. For example, the Yellowstone volcano has a repose/recharge period of around 700,000 years, and Toba of around 380,000 years. Vesuvius

4675-415: The most dangerous type, are very rare; four are known from the last million years , and about 60 historical VEI 8 eruptions have been identified in the geologic record over millions of years. A supervolcano can produce devastation on a continental scale, and severely cool global temperatures for many years after the eruption due to the huge volumes of sulfur and ash released into the atmosphere. Because of

4760-485: The movements of fluids was detected Southern Andean Volcano Observatory (OVDAS). The activity concentrated around and in Cordillera Nevada caldera and on western Cordón Caulle. This prompted SERNAGEOMIN -OVDAS to declare yellow alert. A new eruption started on 4 June 2011. By this time, 3,500 people had been evacuated from nearby areas, while an ash cloud reaching 12,000 m (39,370 ft) blew toward

4845-438: The mud volcano is actually a vent of an igneous volcano. Volcanic fissure vents are flat, linear fractures through which lava emerges. Shield volcanoes, so named for their broad, shield-like profiles, are formed by the eruption of low-viscosity lava that can flow a great distance from a vent. They generally do not explode catastrophically but are characterized by relatively gentle effusive eruptions . Since low-viscosity magma

4930-452: The next. Water vapour is typically the most abundant volcanic gas, followed by carbon dioxide and sulfur dioxide . Other principal volcanic gases include hydrogen sulfide , hydrogen chloride , and hydrogen fluoride . A large number of minor and trace gases are also found in volcanic emissions, for example hydrogen , carbon monoxide , halocarbons , organic compounds, and volatile metal chlorides. The form and style of an eruption of

5015-876: The north side of the mountain. Cinder cones result from eruptions of mostly small pieces of scoria and pyroclastics (both resemble cinders, hence the name of this volcano type) that build up around the vent. These can be relatively short-lived eruptions that produce a cone-shaped hill perhaps 30 to 400 metres (100 to 1,300 ft) high. Most cinder cones erupt only once and some may be found in monogenetic volcanic fields that may include other features that form when magma comes into contact with water such as maar explosion craters and tuff rings . Cinder cones may form as flank vents on larger volcanoes, or occur on their own. Parícutin in Mexico and Sunset Crater in Arizona are examples of cinder cones. In New Mexico , Caja del Rio

5100-549: The ocean surface as new islands or floating pumice rafts . In May and June 2018, a multitude of seismic signals were detected by earthquake monitoring agencies all over the world. They took the form of unusual humming sounds, and some of the signals detected in November of that year had a duration of up to 20 minutes. An oceanographic research campaign in May 2019 showed that the previously mysterious humming noises were caused by

5185-420: The ocean surface, due to the rapid cooling effect and increased buoyancy in water (as compared to air), which often causes volcanic vents to form steep pillars on the ocean floor. Hydrothermal vents are common near these volcanoes, and some support peculiar ecosystems based on chemotrophs feeding on dissolved minerals. Over time, the formations created by submarine volcanoes may become so large that they break

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5270-471: The ocean's surface. In the deep ocean basins, the tremendous weight of the water prevents the explosive release of steam and gases; however, submarine eruptions can be detected by hydrophones and by the discoloration of water because of volcanic gases . Pillow lava is a common eruptive product of submarine volcanoes and is characterized by thick sequences of discontinuous pillow-shaped masses which form underwater. Even large submarine eruptions may not disturb

5355-436: The oldest rocks of PCCVC, those that belong to Sierra Nevada. Sierra Nevada grew over time to form a large shield volcano , during the same time Cordón Caulle was also being built up having rather silicic products compared to coeval Sierra Nevada and Mencheca. The oldest rocks from proper Puyehue volcano are 200,000 years old, representing the youngest possible age for this volcano. It is estimated that some 100,000 years ago in

5440-468: The one that destroyed the city of Saint-Pierre in Martinique in 1902. They are also steeper than shield volcanoes, with slopes of 30–35° compared to slopes of generally 5–10°, and their loose tephra are material for dangerous lahars . Large pieces of tephra are called volcanic bombs . Big bombs can measure more than 1.2 metres (4 ft) across and weigh several tons. A supervolcano is defined as

5525-425: The overlying mantle wedge, thus creating magma . This magma tends to be extremely viscous because of its high silica content, so it often does not reach the surface but cools and solidifies at depth . When it does reach the surface, however, a volcano is formed. Thus subduction zones are bordered by chains of volcanoes called volcanic arcs . Typical examples are the volcanoes in the Pacific Ring of Fire , such as

5610-643: The period between Río Llico and Llanquihue glaciation a large ignimbrite called San Pablo was produced. This ignimbrite covers an estimated area of 1,500 km (370,658 acres) immediately west of Cordillera Nevada, stretching across the Chilean Central Valley almost reaching the Chilean Coast Range . The San Pablo ignimbrite has been associated with the formation of the Cordillera Nevada Caldera. During

5695-619: The plume, and new volcanoes are created where the plate advances over the plume. The Hawaiian Islands are thought to have been formed in such a manner, as has the Snake River Plain , with the Yellowstone Caldera being part of the North American plate currently above the Yellowstone hotspot . However, the mantle plume hypothesis has been questioned. Sustained upwelling of hot mantle rock can develop under

5780-568: The present. The older parts of the Cordillera Nevada caldera and Mencheca volcano reflect even older activity from the Pliocene or the early Pleistocene . In the past 300,000 years, there have been a series of changes in magmatic composition, locus of volcanic activity, magma output rates and eruptive styles. Some 300,000 years ago, important changes occurred in the area of Puyehue. The old Pliocene volcano Mencheca, currently exposed just northeast of Puyehue's cone, declined in activity. This decline

5865-435: The same time interval. Volcanoes vary greatly in their level of activity, with individual volcanic systems having an eruption recurrence ranging from several times a year to once in tens of thousands of years. Volcanoes are informally described as erupting , active , dormant , or extinct , but the definitions of these terms are not entirely uniform among volcanologists. The level of activity of most volcanoes falls upon

5950-492: The same way; they are often described as "caldera volcanoes". Submarine volcanoes are common features of the ocean floor. Volcanic activity during the Holocene Epoch has been documented at only 119 submarine volcanoes, but there may be more than one million geologically young submarine volcanoes on the ocean floor. In shallow water, active volcanoes disclose their presence by blasting steam and rocky debris high above

6035-417: The shelter can be reached after four hours walking. The access through El Caulle is not public as it is not inside Puyehue National Park ; and an entrance fee of 10,000 CLP , as of 2009, has to be paid, of which 3,000 are refunded if visitor packs out his garbage. From the north, there are tracks from the vicinities of Nilahue Valley near Ranco Lake . The track ascends ca 1,000 m through dense forest to

6120-622: The solidified erupted material that makes up the mantle of a volcano may be stripped away that its inner anatomy becomes apparent. Using the metaphor of biological anatomy , such a process is called "dissection". Cinder Hill , a feature of Mount Bird on Ross Island , Antarctica , is a prominent example of a dissected volcano. Volcanoes that were, on a geological timescale, recently active, such as for example Mount Kaimon in southern Kyūshū , Japan , tend to be undissected. Eruption styles are broadly divided into magmatic, phreatomagmatic, and phreatic eruptions. The intensity of explosive volcanism

6205-436: The south. Cordillera Nevada is a 9 km (6 mi) wide semicircular caldera and corresponds to the remnants of a collapsed volcano. Cordillera Nevada covers an area of 700 km (270 sq mi). Cordón Caulle is a northwest trending ridge that hosts a volcanic- tectonic graben in which a fissure vent is developed. Puyehue Volcano is a stratovolcano located on the southeastern end of Cordón Caulle, just east of

6290-406: The surrounding areas, and initially not seismically monitored before its unanticipated and catastrophic eruption of 1991. Two other examples of volcanoes that were once thought to be extinct, before springing back into eruptive activity were the long-dormant Soufrière Hills volcano on the island of Montserrat , thought to be extinct until activity resumed in 1995 (turning its capital Plymouth into

6375-434: The theory of plate tectonics. For example, some volcanoes are polygenetic with more than one period of activity during their history; other volcanoes that become extinct after erupting exactly once are monogenetic (meaning "one life") and such volcanoes are often grouped together in a geographical region. At the mid-ocean ridges , two tectonic plates diverge from one another as hot mantle rock creeps upwards beneath

6460-444: The thinned oceanic crust . The decrease of pressure in the rising mantle rock leads to adiabatic expansion and the partial melting of the rock, causing volcanism and creating new oceanic crust. Most divergent plate boundaries are at the bottom of the oceans, and so most volcanic activity on Earth is submarine, forming new seafloor . Black smokers (also known as deep sea vents) are evidence of this kind of volcanic activity. Where

6545-431: The underlying ductile mantle , and most volcanic activity on Earth takes place along plate boundaries, where plates are converging (and lithosphere is being destroyed) or are diverging (and new lithosphere is being created). During the development of geological theory, certain concepts that allowed the grouping of volcanoes in time, place, structure and composition have developed that ultimately have had to be explained in

6630-522: The vents along the N135° trending fissure. A third phase followed with the appearance of short north-north west (N165°) oriented vents transverse to the main fissure which also erupted rhyodacitic lava. The third phase ended temporarily with viscous lava obstructing the vents, but continued soon with explosive activity restricted to the Gris and El Azufral craters. The eruption came to an end on 22 July. Following

6715-678: The volcanic group or complex, the Cordillera Nevada caldera , the Pliocene Mencheca volcano, Cordón Caulle fissure vents and the Puyehue stratovolcano . Like most stratovolcanoes in the Southern Volcanic Zone of the Andean Volcanic Belt , Puyehue and Cordón Caulle are along the intersection of a traverse fracture with the larger north–south Liquiñe-Ofqui Fault . The volcanic complex has shaped

6800-492: The volcano. Solid particles smaller than 2 mm in diameter ( sand-sized or smaller) are called volcanic ash. Tephra and other volcaniclastics (shattered volcanic material) make up more of the volume of many volcanoes than do lava flows. Volcaniclastics may have contributed as much as a third of all sedimentation in the geologic record. The production of large volumes of tephra is characteristic of explosive volcanism. Through natural processes, mainly erosion , so much of

6885-424: The volcanoes of the East African Rift . A volcano needs a reservoir of molten magma (e.g. a magma chamber), a conduit to allow magma to rise through the crust, and a vent to allow the magma to escape above the surface as lava. The erupted volcanic material (lava and tephra) that is deposited around the vent is known as a volcanic edifice , typically a volcanic cone or mountain. The most common perception of

6970-421: Was described by Roman writers as having been covered with gardens and vineyards before its unexpected eruption of 79 CE , which destroyed the towns of Herculaneum and Pompeii . Accordingly, it can sometimes be difficult to distinguish between an extinct volcano and a dormant (inactive) one. Long volcano dormancy is known to decrease awareness. Pinatubo was an inconspicuous volcano, unknown to most people in

7055-444: Was marked by the eruption of rhyodacite mingled with basaltic andesite rich in magnesium oxide (MgO). The bimodal activity continued with a small hiatus around 30,000 years ago until around 19,000 years ago when Puyehues started to produce lava domes and flows of dacitic to rhyolitic composition, a trend that lasted until 12,000 years before present . Between 15,000 and 12,000 years ago Puyehue also erupted basaltic andesite. During

7140-413: Was probably due a regional change in the location of the active front of the Southern Volcanic Zone that also affected other volcanoes such as Tronador and Lanín . The relocation of the active front gave rise to new volcanoes further westward or increased their activity. The formerly broad magmatic belt narrowed, retaining vigorous activity only in its westernmost parts. Associated with these changes are

7225-550: Was reported in 1893. The next report came in 1905, but the eruption of 8 February 1914 is the first one certain to have occurred. On 13 December 1921, Cordón Caulle began a sub- plinian eruption , with a 6.2 km (4 mi) high plume, periodic explosions and seismicity . The eruption had a Volcanic Explosivity Index of 3 and ended in February 1922. In 1929 and 1934 the Cordón Caulle had fissure eruptions, both with an estimated Volcanic Explosivity Index of 2. Two days after

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