Cerro Azul (Chile volcano)

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Cerro Azul
Cerro Azul.jpg
Aerial view of Cerro Azul from the west.
Highest point
Elevation 3,788 m (12,428 ft) [1]
Coordinates 35°39.2′S70°45.65′W / 35.6533°S 70.76083°W / -35.6533; -70.76083 Coordinates: 35°39.2′S70°45.65′W / 35.6533°S 70.76083°W / -35.6533; -70.76083
Geography
Relief Map of Chile.jpg
Red triangle with thick white border.svg
Cerro Azul
Chile and adjacent lands, showing the location of Cerro Azul
Location Chile
Parent range Andes
Geology
Age of rock Quaternary
Mountain type Stratovolcano
Volcanic arc/belt South Volcanic Zone
Last eruption August 1967

Cerro Azul (Spanish pronunciation:  [ˈsero aˈsul] , blue hill in Spanish), 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.

Spanish language Romance language

Spanish or Castilian, is a Romance language that originated in the Iberian Peninsula and today has over 450 million native speakers in Spain and in the Americas. It is a global language and the world's second-most spoken native language, after Mandarin Chinese.

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).

Maule Region Region of Chile

The Maule Region is one of Chile's 16 first order administrative divisions. Its capital is Talca. The region derives its name from the Maule River which, running westward from the Andes, bisects the region and spans a basin of about 20,600 km2. The Maule river is of considerable historic interest because, among other reasons, it marked the southern limits of the Inca Empire.

Contents

Cerro Azul is responsible for several of South America's largest recorded eruptions, in 1846 and 1932. In 1846, an effusive eruption formed the vent at the site of present-day Quizapu crater on the northern flank of Cerro Azul and sent lava flowing down the sides of the volcano, creating a lava field 8–9 square kilometres (3–3.5 square miles) in area. Phreatic and Strombolian volcanism between 1907 and 1932 excavated this crater. In 1932, one of the largest explosive eruptions of the 20th century occurred at Quizapu Crater and sent 9.5 cubic kilometers (2.3 cu mi) of ash into the atmosphere. The volcano's most recent eruption was in 1967.

Effusive eruption Type of volcanic eruption in which lava steadily flows

An effusive eruption is a type of volcanic eruption in which lava steadily flows out of a volcano onto the ground. There are two major groupings of eruptions: effusive and explosive. Effusive eruption differs from explosive eruption, wherein magma is violently fragmented and rapidly expelled from a volcano. Effusive eruptions are most common in basaltic magmas, but they also occur in intermediate and felsic magmas. These eruptions form lava flows and lava domes, each of which vary in shape, length, and width. Deep in the crust, gasses are dissolved into the magma because of high pressures, but upon ascent and eruption, pressure drops rapidly, and these gasses begin to exsolve out of the melt. A volcanic eruption is effusive when the erupting magma is volatile poor, which suppresses fragmentation, creating an oozing magma which spills out of the volcanic vent and out into the surrounding area. The shape of effusive lava flows is governed by the type of lava, rate and duration of eruption, and topography of the surrounding landscape.

Lava field large expanse of nearly flat-lying lava flows

A lava field, also called a lava plain or lava bed, is a large expanse of nearly flat-lying lava flows. Such features are generally composed of highly fluid basalt lava, and can extend for tens or even hundreds of miles across the underlying terrain. The extent of large lava fields is most readily grasped from the air or in satellite photos, where their typically dark, nearly black color contrasts sharply with the rest of the landscape.

Phreatic is a term used in hydrology to refer to aquifers, in speleology to refer to cave passages, and in volcanology to refer to eruption type.

The South Volcanic Zone has a long history of eruptions and poses a threat to the surrounding region. Any volcanic hazard—ranging from minor ashfalls to pyroclastic flows—could pose a significant risk to humans and wildlife. Despite its inactivity, Cerro Azul could again produce a major eruption; if this were to happen, relief efforts would probably be quickly organized. Teams such as the Volcano Disaster Assistance Program (VDAP) are prepared to effectively evacuate, assist, and rescue people threatened by volcanic eruptions.

Volcanic hazards

A volcanic hazard is the probability that a volcanic eruption or related geophysical event will occur in a given geographic area and within a specified window of time. The risk that can be associated with a volcanic hazard depends on the proximity and vulnerability of an asset or a population of people near to where a volcanic event might occur.

Pyroclastic flow Fast-moving current of hot gas and volcanic matter that moves away from a volcano

A pyroclastic flow is a fast-moving current of hot gas and volcanic matter that moves away from a volcano about 100 km/h (62 mph) on average but is capable of reaching speeds up to 700 km/h (430 mph). The gases can reach temperatures of about 1,000 °C (1,830 °F).

The Volcano Disaster Assistance Program (VDAP) was developed by the U.S. Geological Survey and the United States Agency for International Development's Office of U.S. Foreign Disaster Assistance after the eruption of Nevado del Ruiz (Colombia) in 1985. The volcanic eruption melted a glacier triggering a lahar that killed 25,000 people. It was determined that increased monitoring and enhanced communications between scientists and civil authorities would make it easier to evacuate local populations and save lives. Today the program responds to volcanic crises around the world. The aim of the program is to assist in saving lives and property, to reduce economic losses, and to prevent a natural hazard becoming a natural disaster. VDAP staff members are based at the USGS Cascades Volcano Observatory, in Vancouver, Washington. VDAP channels its energy into four main activities: response to natural disaster, capacity building, training, and volcanological research.

Geography and geology

Regional setting

Volcanism in the Chilean Andes is caused by subduction of the Nazca and Antarctic tectonic plates under the South American Plate. Volcanoes in Chile occur in the Central (CVZ), South (SVZ), and Austral Volcanic Zones (AVZ). The gap that separates the Central and South Volcanic Zones is caused by shallow-angle subduction in the Pampean flat-slab segment where the more buoyant Juan Fernández Ridge subducts under the South American continent. [2] [3] This buoyant region prevents the slab (subducting tectonic plate) from diving deep into the mantle, [2] where the heat and pressure would destabilize the mineral chlorite, releasing water that would in turn cause melting and volcanism. [4] The Patagonian Volcanic Gap, which separates the South and Austral Volcanic Zones, is caused by the subduction of the Chile Ridge, [5] though it is less clear whether this gap also is due to flat-slab subduction; it may instead arise because melting of the subducting slab there produced felsic igneous rocks instead of volcanoes. [6]

Andean Volcanic Belt Volcanic belt in South America

The Andean Volcanic Belt is a major volcanic belt along the Andean cordillera in Argentina, Bolivia, Chile, Colombia, Ecuador, and Peru. It is formed as a result of subduction of the Nazca Plate and Antarctic Plate underneath the South American Plate. The belt is subdivided into four main volcanic zones that are separated from each other by volcanic gaps. The volcanoes of the belt are diverse in terms of activity style, products, and morphology. While some differences can be explained by which volcanic zone a volcano belongs to, there are significant differences within volcanic zones and even between neighboring volcanoes. Despite being a type location for calc-alkalic and subduction volcanism, the Andean Volcanic Belt has a broad range of volcano-tectonic settings, as it is a rift systems and extensional zones, transpressional faults, subduction of mid-ocean ridges and seamount chains apart from a large range on crustal thicknesses and magma ascent paths, and different amount of crustal assimilations.

Subduction A geological process at convergent tectonic plate boundaries where one plate moves under the other

Subduction is a geological process that takes place at convergent boundaries of tectonic plates where one plate moves under another and is forced to sink due to gravity into the mantle. Regions where this process occurs are known as subduction zones. Rates of subduction are typically in centimeters per year, with the average rate of convergence being approximately two to eight centimeters per year along most plate boundaries.

Nazca Plate Oceanic tectonic plate in the eastern Pacific Ocean basin

The Nazca Plate, named after the Nazca region of southern Peru, is an oceanic tectonic plate in the eastern Pacific Ocean basin off the west coast of South America. The ongoing subduction, along the Peru–Chile Trench, of the Nazca Plate under the South American Plate is largely responsible for the Andean orogeny. The Nazca Plate is bounded on the west by the Pacific Plate and to the south by the Antarctic Plate through the East Pacific Rise and the Chile Rise respectively. The movement of the Nazca Plate over several hotspots has created some volcanic islands as well as east-west running seamount chains that subduct under South America. Nazca is a relatively young plate both in terms of the age of its rocks and its existence as an independent plate having been formed from the break-up of the Farallon Plate about 23 million years ago. The oldest rocks of the plate are about 50 million years old.

Offshore volcanism also occurs in Chile. Intraplate volcanism generated from the Easter and Juan Fernández hotspots has formed many Chilean islands, including Isla Salas y Gómez, Easter Island, and the Juan Fernández Islands. Underwater volcanism occurs due to seafloor spreading along the Chile Ridge. [3]

Easter hotspot

The Easter hotspot is a volcanic hotspot located in the southeastern Pacific Ocean. The hotspot created the Sala y Gómez Ridge which includes Easter Island and the Pukao Seamount which is at the ridge's young western edge. Easter Island, because of its tectonomagmatic features, represents an end-member type of hotspot volcano in this chain.

Juan Fernández hotspot

The Juan Fernández hotspot is a volcanic hotspot located in the southeastern Pacific Ocean. The hotspot created the Juan Fernández Ridge which includes the Juan Fernández Archipelago and a long seamount chain that is being subducted in the Peru–Chile Trench at the site of Papudo giving origin to the Norte Chico Volcanic Gap.

Hotspot (geology) Volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle

In geology, the places known as hotspots or hot spots are volcanic regions thought to be fed by underlying mantle that is anomalously hot compared with the surrounding mantle. Their position on the Earth's surface is independent of tectonic plate boundaries. There are two hypotheses that attempt to explain their origins. One suggests that hotspots are due to mantle plumes that rise as thermal diapirs from the core–mantle boundary. The other hypothesis is that lithospheric extension permits the passive rising of melt from shallow depths. This hypothesis considers the term "hotspot" to be a misnomer, asserting that the mantle source beneath them is, in fact, not anomalously hot at all. Well-known examples include the Hawaii, Iceland and Yellowstone hotspots.

Nearly 100 Quaternary (Pleistocene- or Holocene-age) independent volcanoes exist in the country, in addition to 60 volcanic complexes and caldera systems. [3] Of the 200 historically active volcanoes in the Andean Range, 36 are found in Chile. [7]

Quaternary is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS). It follows the Neogene Period and spans from 2.588 ± 0.005 million years ago to the present. The Quaternary Period is divided into two epochs: the Pleistocene and the Holocene. The informal term "Late Quaternary" refers to the past 0.5–1.0 million years.

The Pleistocene is the geological epoch which lasted from about 2,588,000 to 11,700 years ago, spanning the world's most recent period of repeated glaciations. The end of the Pleistocene corresponds with the end of the last glacial period and also with the end of the Paleolithic age used in archaeology.

Holocene The current geological epoch, covering the last 11,700 years

The Holocene is the current geological epoch. It began approximately 11,650 cal years before present, after the last glacial period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene together form the Quaternary period. The Holocene has been identified with the current warm period, known as MIS 1. It is considered by some to be an interglacial period within the Pleistocene Epoch.

Local setting

The mountain with the appearance of a truncated cone, at the centre of the image, is Descabezado Grande volcano, and close to it is the pyramidal Cerro Azul. Descabezado Grande y Cerro Azul.jpg
The mountain with the appearance of a truncated cone, at the centre of the image, is Descabezado Grande volcano, and close to it is the pyramidal Cerro Azul.

Cerro Azul is part of the South Volcanic Zone, which runs through central and western Chile and extends south to Argentina. This range includes at least nine caldera complexes, more than 70 of Chile's stratovolcanoes and volcanic fields that have been active in the Quaternary, and hundreds of minor eruptive centres. The South Volcanic Zone is the most volcanically active region in Chile, and produces around one eruption per year. Its largest historical eruption was at Quizapu Crater, located on the north side of Cerro Azul's summit (see below), and its most active volcanoes are Llaima and Villarrica. [8]

Cerro Azul, just 7 kilometers (4.3 mi) south of Descabezado Grande volcano, is part of the Descabezado Grande–Cerro Azul eruptive system, [9] a volcanic field that comprises its two large namesake volcanic edifices and several smaller vents, [10] including 12 Holocene calderas. [11] Both volcanoes lie on top of the Casitas Shield, a plateau built of over 100 lava flows that erupted in at least 12 volcanic episodes during the Quaternary period. The upper lava layers are dated at 340,000 years. [10] [11]

As with the majority of the Andean volcanoes, Cerro Azul is a stratovolcano, meaning that it consists of layers, or strata, of volcanic ash and lava flows. [12] The cone of Cerro Azul has a total volume of about 11 cubic kilometers (3 cu mi), and is a young feature, formed in the Holocene. [11] It is made of agglutinated pyroclasts and some daciteandesine lavas. [11] The cone has a few volcanic craters; [9] the majority of its eruptions in recorded history have originated from Quizapu Crater on the northern flank of Cerro Azul's cone. [11] Other craters lying on the flanks of the main cone are Caracol ("Snail"), Crater los Quillayes, Crater la Resolana, and Crater sin Nombre ("Nameless Crater"). All of the craters lie between 2,000 and 3,000 meters (6,600 and 9,800 ft) in elevation, except Quizapu, which is 3,292 meters (10,801 ft) up the volcano. [9] The summit of Cerro Azul is crowned by an asymmetric crater about 500 meters (1,640 ft) in diameter. [11] Pleistocene glacial activity is evident in the form of 500 meter (1,640 ft) deep struts in the volcanoes' sides. These deep cuts have revealed strata of older rock. [11]

Major Chilean volcanoes are marked by red triangles on this map. Map chile volcanoes.gif
Major Chilean volcanoes are marked by red triangles on this map.

Quizapu Crater

Quizapu, which formed during the 1846 eruption, is the most prominent crater. [13] It is also known as Cerro del Medio ("Middle Hill") or Volcan Nuevo ("New Volcano"). [9] The volcanic vent formed during an effusive eruption involving hornblende–dacite flows accompanied by tephra, and the crater was excavated by phreatic and Strombolian eruptions between 1907 and 1932. Pent-up pressure within the volcano spawned an enormous Plinian eruption in 1932. The volume of lava ejected during this single event is roughly equal to that ejected during the rest of the eruptive history at Quizapu, since its formation in 1846. Although 9.5 cubic kilometers (2.3 cu mi) of material was ejected, no subsidence was detected from the removal of magma. [13] Because of aerodynamic drag, a Plinian eruption excavates a circular crater. As the earlier eruptions had already formed an approximately circular caldera, the Plinian eruption was able to proceed efficiently, with minimal drag and minimal reshaping of the crater. [14]

The Quizapu Crater is almost perfectly circular, and rises to a prominence of 150 to 250 meters (490 to 820 ft) above the surrounding portions of the volcano. [13] Cresting at 3,292 meters (10,801 ft) in elevation, [9] Quizapu is one of the highest known Plinian craters. The radius of the crater floor, which is the current inner vent, is around 150 meters (500 ft), while the radius of its rim is 300–350 meters (980–1,150 ft). The crater floor lies at 2,928 meters (9,606 ft), and the rim lies 150–300 meters (500–1,000 ft) above that, giving the walls an average slope of 34–35 degrees (close to the angle of repose). The western wall is cut by two long, dacitic lava flows: probably the remnants of a dome or an eruption. [13] The crater is surrounded by debris from its 1932 eruption, and topped by layers—50 meters (160 ft) thick—of mafic scoria and ash. [15]

Climate and vegetation

Cerro Azul is situated in a Mediterranean climate zone, characterized by hot and dry summers but mild and wet winters. The temperatures and precipitation are strongly dependent on topography. In the Andes the annual average maximum temperatures lie in the range 20 to 25 °C (68 to 77 °F), while minimum temperatures are below 0 °C (32 °F). Annual precipitation is up to 800 mm (31.5 inches). [16]

Vegetation in the Andes varies with elevation. Above 1,600 meters (5,249 ft) the slopes of mountains are covered by Alpine-like steppe, while below there are zones of Nothofagus forest, Hygrophilous forest, Sclerophylous forest, and matorral. The number of plant species is likely to exceed 2,000, although no comprehensive study of the flora of Central Chile has been undertaken. [16]

Eruptive history

Cerro Azul has a history of eruptions dating back to at least 1846. The known events include effusive eruptions (lava flows), which created the Quizapu vent, explosive eruptions, and phreatic eruptions. Pyroclastic flows have also been observed as a result of some of these explosive eruptions. The earliest recorded eruption began on November 26, 1846, while the volcano's last eruption began on August 9, 1967. [9] The volcano has produced two of the largest eruptions in South America in recorded history, in 1846 and 1932. Both released 4–5 cubic kilometers (1.0–1.2 cu mi) of the dacitic magma. [11]

First record of activity, 1846

On November 26, 1846, Cerro Azul erupted. This was the first report of activity at the volcano, and no trace of fumaroles, adjacent vents, or pre-eruptive activity exists. Most descriptions of the eruption come from the backcountry herdsmen (arrieros). One, who was camped in a valley approximately 7 kilometers (4 mi) east of Quizapu, heard "a great noise and a cloud of ash" emanate from the mountain in the late afternoon. No precursor activity was reported, and the herdsman claimed that there were no earthquakes during the late afternoon eruption. [11]

That night, two herdsmen near the site heard a continuous roar, punctuated by loud bangs and crackling sounds "like that of great rockslides". Lightning and thunder accompanied the spectacle. They saw many blue flames, and were choked by sulfurous gas. Observers in Talca 85 kilometers (53 mi) away heard the eruption noises, and the sulfurous odors reached them the day after the eruption. None of the reports mention earthquakes or ash fall, though the crackling and banging sounds could be from block lavas (ʻaʻā). [17]

This first recorded eruption of Cerro Azul was effusive, and formed the volcanic vent at Quizapu. Hornblende–dacite lava erupted with small masses of tephra, which had been degassed shortly before the eruption. [13] Lava flowed over the Estero Barroso Valley and westward into the Río Blanquillo Valley. [9] By November 28, the volcano appeared at rest, and the herdsman returned to the place of first observation. There, they found a blocky lava field. The lava was still hot, fuming and crackling with gas and flame. Fascinated by the volcano, Ignacy Domeyko traveled to Chile to study the field and found its width to be 8–9 square kilometers (3.1–3.5 sq mi). By 1992 the field had grown to twice that size. [18]

Early 20th century

Cerro Azul was quiet from 1846 to the beginning of the 20th century. After a possible precursor explosive event in 1903, Cerro Azul once again erupted in 1907. Between 1907 and 1914, plumes and clouds of ash frequently rose out of the caldera, and at least a few of these events were explosive. On September 8, 1914, an explosive eruption sent a plume 6 or 7 kilometers (about 4 mi) into the air over 8 minutes. By 1916, these eruptions had produced a caldera nearly identical to the one in existence today. [18]

The volcano also erupted phreatically several times, as recorded by Vogel in 1913 and 1920, with its activity increasing from 1916 to 1926. During these years, the eruptions grew more frequent and more violent. A major outburst on November 2, 1927 started a period of nearly continuous violent eruptions that lasted until 1929. During this period, Cerro Azul sometimes erupted daily, sending columns of ash as far as 6 or 7 kilometers (about 4 mi) into the air. Quizapu Crater grew slightly during this eruptive period. [18]

Pre-1932 volcanism was largely phreatic or fumarolic, as evidenced by the lack of tephra generated by these eruptions. Photographs from 1912 show vapor plumes containing little ash, rising 1–2 kilometers (0.6–1.2 mi) above the crater. [18]

Major eruption, 1932

By 1932, Quizapu had produced many phreatic events and one effusive eruption, but no large Plinian eruptions. This frequency of minor eruptive activity proved to be a precursor for a major eruption. On 25 January 1932, observers in Malargue saw a large black cloud over the summit. By 9 April, the volcano emitted green gas and started to "bellow like a bull". [19] On April 10, Cerro Azul finally erupted, releasing a towering column or plume of white gas. After 10 AM, the plume turned black with ash and began to form an umbrella shape. The ash was carried by wind into Puesto El Tristan in Argentina, about 47 kilometers (29 mi) away, where beginning at 1 PM it rained down for hours. At 4 PM, coarser sandy material and some pumice lapilli began to fall. [19]

Cerro Azul's April 1932 eruption was one of the largest of the 20th century. Releasing 9.5 cubic kilometers (2 cu mi) of lava, the volcano ejected primarily dacitic tephra, [9] accompanied by rhyodacite, andesite, [20] and minuscule amounts of andesitic and basaltic scoria. At least one eruptive period lasted for 18  hours, creating an "exceptionally uniform" deposit. [13] Eruption columns, extending 27–30 kilometers (17–19 mi) into the air, were sighted. Phenocrysts were similar to the effusive eruption in 1846. [13] Soon after, both the Tinguiririca and Descabezado Grande volcanoes began erupting, sending clouds of ash 800 kilometers (500 mi) into Argentina. [21] The eruption had a Volcanic Explosivity Index (VEI) of at least 5. [9]

Since the eruption of 1932 Quizapu has been quiet. In 1949 and 1967 small ash clouds were reported, while in the 1980s there were no signs of activity other than fumaroles. [22]

Threats and preparedness

Cerro Azul is in the South Volcanic Zone, where many volcanoes pose a threat to human life. Among the other active volcanoes of the South Volcanic Zone are Mount Hudson, Llaima, and Villarrica. [23] Villarrica and Llaima together have more than 80 reported episodes of volcanism since 1558, and at least 40 South Volcanic Zone volcanoes have had Holocene-age eruptions. [24]

Every known type of eruption (Hawaiian, Strombolian, Plinian, subplinian, phreatic, phreatomagmatic, and Vulcanian) has occurred at some point in the range. [8] Cerro Azul itself has experienced phreatic, Strombolian, and Plinian activity in human history. [13] The type of eruption tends to correspond with lava composition. Strombolian eruptions at Llaima, Antuco, Villarrica, and elsewhere have been produced by basaltic to basaltic–andesitic activity. Dacitic to rhyolitic lavas have been linked to subplinian and Plinian eruptions, such as those at Quizapu (1932) and Hudson (1991). Because of this variability, volcanic hazards from Cerro Azul and the surrounding region could come in many different forms. Historical eruptions typically have produced lahars, lava flows, and ashfalls. Lava flows and lahars could wipe out entire cities or towns. Ashfall produced by explosive eruptions could interfere with air traffic. Most threatening of all is the risk of pyroclastic flows or avalanches, which have historically traversed as far as 100 kilometers (62 mi) in the region. [8]

Mount Hudson, an active volcano in the SVZ, shortly after an eruption in 1991. The volcano has produced eruptions as powerful as Volcanic Explosivity Index degree six. Cerro hudson.jpg
Mount Hudson, an active volcano in the SVZ, shortly after an eruption in 1991. The volcano has produced eruptions as powerful as Volcanic Explosivity Index degree six.

Past eruptions of Quizapu Crater ejected enormous amounts of ash that traveled as far as Brazil. After the 1932 eruption, the local vegetation was devastated, and the area remained barren until the 1990s, though human life was not impacted. [26] Despite the extent of its eruptions, the threat to humans from Quizapu is relatively small because of the remote location of Cerro Azul. Nevertheless, the size of past eruptions is large enough for scientists to be worried. Evidence of a potentially deadly threat lies in a lahar at Descabezado Grande. [19] Historically, lahars have killed thousands in the Andes. [27] [28] There is, however, a possibility that a large reservoir of rhyodacite magma may exist under the Azul–Descabezado complex. If this is the case, all previous eruptions in 1846–1967 were only preliminary, preclimactic leaks from the large magma chamber beneath, and a large caldera-forming eruption may be expected in the future. [29]

If Cerro Azul were to erupt, relief efforts could be orchestrated. The Volcanic Disaster Assistance Program (VDAP) formed in response to the famous eruption of Nevado del Ruiz in Colombia, and responded to the 1991 eruption of Mount Hudson in Chile. [30] The team's stated aim is to "reduce eruption-caused fatalities and economic losses in developing countries". Made up of various USGS offices (such as the Cascades Volcano Observatory; CVO that are responsible for monitoring Mount St. Helens), the team is outfitted with equipment capable of monitoring any volcano. This equipment allows them to predict volcanic eruptions effectively and rapidly, and to evacuate nearby homes. [30]

See also

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Nevado de Longaví is a volcano in the Andes of central Chile. The 3,242 m (10,636 ft) high volcano lies in the Linares Province, which is part of the Maule Region. It features a summit crater and several parasitic vents. The volcano is constructed principally from lava flows. Two collapses of the edifice have carved collapse scars into the volcano, one on the eastern slope known as Lomas Limpias and another on the southwestern slope known as Los Bueye. The volcano features a glacier and the Achibueno and Blanco rivers originate on the mountain.

Isluga stratovolcano located in Colchane, near Chile/Bolivia border

Isluga is a stratovolcano located in Colchane, 7 kilometres (4.3 mi) west of the Chile-Bolivia border and at the west end of a group of volcanoes lined up in an east-west direction, which also includes the volcanoes Cabaray and Tata Sabaya. Isluga has an elongated summit area and lies within the borders of Volcán Isluga National Park in Chile's Tarapacá Region.

Descabezado Grande mountain in Curicó Province Chile

Descabezado Grande is a stratovolcano located in the Maule Region of central Chile. It is capped by a 1.4-kilometre-wide (0.9 mi) ice-filled caldera and named for its flat-topped form, as descabezado means "headless" in Spanish. A smaller crater about 500 metres (1,600 ft) wide is found in the northeast part of the caldera, and it has active fumaroles.

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.

Mentolat mountain in Aysén Province Chile

Mentolat is an ice-filled, 6 km (4 mi) wide caldera in the central portion of Magdalena Island, Aisén Province, Chilean Patagonia. This caldera sits on top of a stratovolcano which has generated lava flows and pyroclastic flows. The caldera is filled with a glacier.

Putana (volcano) South American volcano

Putana, sometimes referred to as Jorqencal or Machuca, is a volcano on the border between Bolivia and Chile and close to the Sairecabur volcanic complex. Part of the Central Volcanic Zone of the Andes, its summit is 5,890 metres (19,320 ft) above sea level and contains a summit crater with two smaller craters nested within it. Beneath the summit, the volcano features a number of lava domes and lava flows, some of which originated in flank vents.

Sollipulli mountain

Sollipulli is an ice-filled volcanic caldera and volcanic complex, which lies southeast of the small town of Melipeuco in the La Araucanía Region, Chile. It is part of the Southern Volcanic Zone of the Andes, one of the four volcanic belts in the Andes chain.

Chaitén (volcano) mountain in Palena Province Chile

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 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.

Puyehue-Cordón Caulle Volcanic complex in Chile

Puyehue and Cordón Caulle 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 the volcanic group or complex, the Cordillera Nevada caldera, the Pliocene Mencheca volcano, Cordón Caulle fissure vents and the Puyehue stratovolcano.

Calabozos mountain in Chile

Calabozos is a Holocene caldera in central Chile's Maule Region. Part of the Chilean Andes' volcanic segment, it is considered a member of the Southern Volcanic Zone (SVZ), one of the three distinct volcanic belts of South America. This most active section of the Andes runs along central Chile's western edge, and includes more than 70 of Chile's stratovolcanoes and volcanic fields. Calabozos lies in an extremely remote area of poorly glaciated mountains.

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.

Cerro Chao

Cerro Chao is a lava flow complex associated with the Cerro del León volcano in the Andes. It is the largest known Quaternary silicic volcano body and part of the most recent phase of activity in the Altiplano–Puna volcanic complex.

Irruputuncu mountain shared by Bolivia and Chile

Irruputuncu is a volcano in the commune of Pica, Tamarugal Province, Tarapacá Region, Chile, as well as San Pedro de Quemes Municipality, Nor Lípez Province, Potosí Department, Bolivia. The mountain's summit is 5,163 m (16,939 ft) high and has two summit craters—the southernmost 200 m (660 ft)-wide one has active fumaroles. The volcano also features lava flows, block and ash flows and several lava domes. The volcano is part of the Andean Central Volcanic Zone (CVZ).

References

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Bibliography

Further reading