Lastarria

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Lastarria
Casualidad C 10.jpg
Lastarria seen from Mina La Casualidad
Highest point
Elevation 5,706 m (18,720 ft) [1]
Coordinates 25°10′S68°31′W / 25.167°S 68.517°W / -25.167; -68.517 Coordinates: 25°10′S68°31′W / 25.167°S 68.517°W / -25.167; -68.517 [1]
Geography
Relief Map of Chile.jpg
Red triangle with thick white border.svg
Lastarria
Region, Province Antofagasta Region Salta Province
Parent range Central Andes
Geology
Age of rock Pleistocene-Holocene (900,000 to 2400 years BP)
Mountain type Stratovolcano
Volcanic belt Central Volcanic Zone
Last eruption 2460 ± 50/60 years BP

Lastarria is a stratovolcano that lies on the border between Chile and Argentina. It is part of the Central Volcanic Zone, one of the four segments of the volcanic arc of the Andes. Several volcanoes are located in this chain of volcanoes, which is formed by subduction of the Nazca Plate beneath the South American Plate.

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).

Chile Republic in South America

Chile, officially the Republic of Chile, is a South American country occupying a long, narrow strip of land between the Andes to the east and the Pacific Ocean to the west. It borders Peru to the north, Bolivia to the northeast, Argentina to the east, and the Drake Passage in the far south. Chilean territory includes the Pacific islands of Juan Fernández, Salas y Gómez, Desventuradas, and Easter Island in Oceania. Chile also claims about 1,250,000 square kilometres (480,000 sq mi) of Antarctica, although all claims are suspended under the Antarctic Treaty.

Argentina Federal republic in South America

Argentina, officially the Argentine Republic, is a country located mostly in the southern half of South America. Sharing the bulk of the Southern Cone with Chile to the west, the country is also bordered by Bolivia and Paraguay to the north, Brazil to the northeast, Uruguay and the South Atlantic Ocean to the east, and the Drake Passage to the south. With a mainland area of 2,780,400 km2 (1,073,500 sq mi), Argentina is the eighth-largest country in the world, the fourth largest in the Americas, and the largest Spanish-speaking nation. The sovereign state is subdivided into twenty-three provinces and one autonomous city, Buenos Aires, which is the federal capital of the nation as decided by Congress. The provinces and the capital have their own constitutions, but exist under a federal system. Argentina claims sovereignty over part of Antarctica, the Falkland Islands, and South Georgia and the South Sandwich Islands.

Contents

Lastarria is formed by two volcanic edifices and one subsidiary lava flow field. There is no recorded eruptive activity, but the volcano displays vigorous fumarolic activity. It is located on top of older volcanic rocks and features both andesite and dacite.

Andesite An intermediate volcanic rock

Andesite ( or ) is an extrusive igneous, volcanic rock, of intermediate composition, with aphanitic to porphyritic texture. In a general sense, it is the intermediate type between basalt and rhyolite, and ranges from 57 to 63% silicon dioxide (SiO2) as illustrated in TAS diagrams. The mineral assemblage is typically dominated by plagioclase plus pyroxene or hornblende. Magnetite, zircon, apatite, ilmenite, biotite, and garnet are common accessory minerals. Alkali feldspar may be present in minor amounts. The quartz-feldspar abundances in andesite and other volcanic rocks are illustrated in QAPF diagrams.

Dacite Volcanic rock intermediate in composition between andesite and rhyolite

Dacite is an igneous, volcanic rock. It has an aphanitic to porphyritic texture and is intermediate in composition between andesite and rhyolite. The word dacite comes from Dacia, a province of the Roman Empire which lay between the Danube River and Carpathian Mountains where the rock was first described.

Lastarria has produced a large landslide deposit as well as flows of molten sulfur. A progressive uplift of the terrain around Lastarria and farther south has been recognized.

Landslide type of natural disaster, geological phenomenon

The term landslide or less frequently, landslip, refers to several forms of mass wasting that include a wide range of ground movements, such as rockfalls, deep-seated slope failures, mudflows, and debris flows. Landslides occur in a variety of environments, characterized by either steep or gentle slope gradients, from mountain ranges to coastal cliffs or even underwater, in which case they are called submarine landslides. Gravity is the primary driving force for a landslide to occur, but there are other factors affecting slope stability that produce specific conditions that make a slope prone to failure. In many cases, the landslide is triggered by a specific event, although this is not always identifiable.

Sulfur Chemical element with atomic number 16

Sulfur (in non-scientific British use also sulphur) is a chemical element with the symbol S and atomic number 16. It is abundant, multivalent, and nonmetallic. Under normal conditions, sulfur atoms form cyclic octatomic molecules with a chemical formula S8. Elemental sulfur is a bright yellow, crystalline solid at room temperature.

Geography and structure

Lastarria is situated in the Central Andes, in the Antofagasta Region of Chile, and straddles the border with Argentina. [2] [3] The city of Antofagasta lies 250 kilometres (160 mi) northwest of Lastarria. [4] The area of the Central Andes is difficult to access and its volcanoes are usually poorly monitored. [5] There are no human populations within 150 kilometres (93 mi) of Lastarria. [6] From the former Catalina railway station 120 kilometres (75 mi) west, an unpaved road leads to Lastarria. [7]

Antofagasta Region Region of Chile

The Antofagasta Region is one of Chile's sixteen first-order administrative divisions. It comprises three provinces, Antofagasta, El Loa and Tocopilla. It is bordered to the north by Tarapacá and by Atacama to the south and is the second-largest region of Chile. To the east it borders Bolivia and Argentina. The capital of the region is the port city of Antofagasta, another important city being Calama. The main economic activity is copper mining in the giant porphyry copper systems located inland.

Lastarria is part of the Andean Central Volcanic Zone, [3] which extends over 1,500 kilometres (930 mi) from Peru to Chile. [5] Over 1,000 volcanic edifices have been identified in this zone, [8] of which about 50 volcanoes are active or potentially active, [5] with many exceeding 6,000 metres (20,000 ft) in altitude. [9] In addition, the zone features 18 monogenetic volcanoes and about 6 caldera/ignimbrite systems. [10]

Peru Republic in South America

Peru, officially the Republic of Peru, is a country in western South America. It is bordered in the north by Ecuador and Colombia, in the east by Brazil, in the southeast by Bolivia, in the south by Chile, and in the west by the Pacific Ocean. Peru is a megadiverse country with habitats ranging from the arid plains of the Pacific coastal region in the west to the peaks of the Andes mountains vertically extending from the north to the southeast of the country to the tropical Amazon Basin rainforest in the east with the Amazon river.

A monogenetic volcanic field is a type of volcanic field consisting of a group of small monogenetic volcanoes, each of which erupts only once, as opposed to polygenetic volcanoes, which erupt repeatedly over a period of time. Many monogenetic volcanoes are cinder cones, often with lava flows, such as Parícutin in the Michoacán-Guanajuato volcanic field, which erupted from 1943 to 1952. Some monogenetic volcanoes are small lava shields, such as Rangitoto Island in the Auckland volcanic field. Other monogenetic volcanoes are tuff rings or maars. A monogenetic field typically contains between ten and a hundred volcanoes. The Michoacán-Guanajuato field in Mexico contains more than a thousand volcanoes and is much larger than usual.

A caldera is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber/reservoir in a volcanic eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is lost. The ground surface then collapses downward into the emptied or partially emptied magma chamber, leaving a massive depression at the surface. Although sometimes described as a crater, the feature is actually a type of sinkhole, as it is formed through subsidence and collapse rather than an explosion or impact. Only seven caldera-forming collapses are known to have occurred since 1900, most recently at Bárðarbunga volcano, Iceland in 2014.

Edifice proper

Lastarria is formed by two coalesced edifices, the main cone and the older South Spur (Espolón Sur), [11] which are joined at an altitude of about 5,500 metres (18,000 ft) [12] and form a 10-kilometre (6.2 mi) long ridge. [13] The main cone comprises lava domes, lava flows, pyroclastic flows, and scoria, [11] [1] with most of the volcano covered by pyroclastic material, [14] some of which extends to the southeastern margin of the Salar de Aguas Calientes . [15] Lava flows are exposed mainly on the northwestern slope, [14] where they reach thicknesses of 40 metres (130 ft). [16] The South Spur has also generated lava flows. [11] The volcano covers a surface area of about 156 square kilometres (60 sq mi). [15]

Lava dome Roughly circular protrusion from slowly extruded viscous volcanic lava

In volcanology, a lava dome or volcanic dome is a roughly circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions on earth are lava dome forming. The geochemistry of lava domes can vary from basalt to rhyolite although the majority are of intermediate composition The characteristic dome shape is attributed to high viscosity that prevents the lava from flowing very far. This high viscosity can be obtained in two ways: by high levels of silica in the magma, or by degassing of fluid magma. Since viscous basaltic and andesitic domes weather fast and easily break apart by further input of fluid lava, most of the preserved domes have high silica content and consist of rhyolite or dacite.

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).

Scoria Dark vesicular volcanic rock

Scoria is a highly vesicular, dark colored volcanic rock that may or may not contain crystals (phenocrysts). It is typically dark in color, and basaltic or andesitic in composition. Scoria is relatively low in density as a result of its numerous macroscopic ellipsoidal vesicles, but in contrast to pumice, all scoria has a specific gravity greater than 1, and sinks in water. The holes or vesicles form when gases that were dissolved in the magma come out of solution as it erupts, creating bubbles in the molten rock, some of which are frozen in place as the rock cools and solidifies. Scoria may form as part of a lava flow, typically near its surface, or as fragmental ejecta, for instance in Strombolian eruptions that form steep-sided scoria cones. Chemical analysis of scoria found in Yemen showed that it was mainly composed of volcanic glass with a few zeolites. Most scoria is composed of glassy fragments, and may contain phenocrysts. The word scoria comes from the Greek σκωρία, skōria, rust. A colloquial term for scoria is cinder.

Five overlapping craters are aligned in a north-south line on Lastarria's main cone. [17] [18] Volcanic activity has migrated north during the history of Lastarria, and the most recent eruption products are found on the northern and western slopes. [2] A lava dome sits on the northernmost crater rim. [12] The South Spur has two craters. [11]

The volcano rises from a terrain of about 4,200 metres (13,800 ft) altitude [19] and has fairly steep slopes. [20] Much of the surface, including the Southern Spur, is covered by deposits left by volcanic ash fall. [2] Some parts of the Southern Spur display evidence of hydrothermal alteration. [14] The total volume of the edifice is about 10.1 cubic kilometres (2.4 cu mi). [16]

The Negriales del Lastarria (also known as Big Joe [17] ) lava flow complex lies southwest of the Lastarria volcano and covers an extensive surface. [1] It is formed by several massive flows erupted from a single vent during three or eight pulses; [11] [12] the longest reaches a length of 10 kilometres (6.2 mi). [13] These lavas are block lavas with flow ridges and levees. [11] The total volume of the lava field is about 5.4 cubic kilometres (1.3 cu mi). [12]

Neighbouring mountains include the 4,709-metre (15,449 ft) high Cerro Bayo northwest and the 5,214-metre (17,106 ft) high Cerro Piramide close to Negriales de Lastarria in the southwest. Almost due north of Lastarria lies the Laguna de la Azufrera, [14] a salt pan with a waterbody that is almost a lake, its name is a reference to the sulfur deposits of Lastarria. [21] This waterbody may be a source of water for the fumarolic system [22] Water levels in the lake were higher in the past, as evidenced by two recognizable shorelines, [23] and the lake's surface area reached 18 square kilometres (7 sq mi). [24]

Landslide scar

A major sector collapse occurred on Lastarria's southeastern flank, leaving a clearly defined north-south scarp in the volcano that opens to the east-southeast. On the northern side, this scarp is 65 metres (213 ft) high; [2] it becomes less pronounced at its southern end. The highest point of the scarp lies at an altitude of 5,575 metres (18,291 ft). [25]

The debris avalanche deposit is 8 kilometres (5.0 mi) long and well preserved. [26] [2] After exiting the collapse scar over its northern opening, it overrode an older scoria cone before coming to rest. [25] The slide, bordered by levee-like structures reaching a height of 20 metres (66 ft), formed 500-metre (1,600 ft) wide and 40-metre (130 ft) high lobes. Unlike many debris avalanche deposits, the Lastarria debris avalanche lacks large blocks and has only a few hummocks. [27] The velocity of the avalanche has been estimated to have been over 84 metres per second (280 ft/s), [28] a fairly high velocity for a volcanic debris avalanche. It is possible that air was entrained in the debris, which thus assumed properties similar to an ignimbrite. [29]

The avalanche deposit consists mostly of loose material such as ash, lapilli, pumice, with only a few lithic blocks. [30] This loose consistency may explain the lack of megablocks. [31] Its total volume is about 0.091 cubic kilometres (0.022 cu mi), less than the volume of the Mount St. Helens and Socompa deposits. It is comparable to the volume of the landslide that the Ancash earthquake triggered on Huascarán in Peru in 1970, resulting in more than 20,000 fatalities. [25] Evidence points to previous flank collapses at Lastarria. [26]

Sulfur

The fumaroles on Lastarria have created widespread deposits of sulfur. The sulfur has also formed flows, of which the two largest are 350 metres (1,150 ft) and 250 metres (820 ft) long. The longer flow is partly buried by the shorter one and has already lost part of its surface structure. No vents have been found; sulfur flows appear to emerge from the fumarolic terrain. One andesite lava flow has generated several subsidiary sulfur flows that resemble pahoehoe flows and have widths of 1 to 2.5 metres (3 ft 3 in to 8 ft 2 in). [19] [32] It is likely that sulfur deposited by fumaroles formed such flows. [33] Some fumaroles currently release centimetre-long sulfur flows. [32] Flows of sulfur are highly fragile constructs that can easily be destroyed. [34]

The conditions surrounding the emplacement of the sulfur have caused the sulfur to assume various colours, [19] including black, brown-orange, orange, red, yellow, and yellow-orange. [35] These colours vary along the length of the flows and between various flows, [19] indicating that temperatures varied between one flow and another. Liquid sulfur has different viscosity and rheomorphic properties at different temperatures, and some variation occurred at Lastarria's flows as well. [36]

Such sulfur flows are rare on Earth; they may be more common on the Jupiter moon Io. On Earth, they have been found at Kawah Ijen in Indonesia, Mount Iō (Shiretoko) in Japan, Mauna Loa on Hawaii, Momotombo in Nicaragua, and Sierra Negra on the Galapagos Islands. [19] [37]

Internal structure

The internal structure of a volcano can be visualized with a technique known as seismic wave tomography. [38] An inverted funnel-shaped low velocity anomaly with a width of 4 by 9 kilometres (2.5 by 5.6 mi) extends to a depth of 1 kilometre (0.62 mi) beneath the volcano and appears to be associated with areas of high fumarolic activity; it may be the hydrothermal system. [39] An even stronger anomaly at depths of 3 to 6 kilometres (1.9 to 3.7 mi) may be the magma chamber of the volcano and an associated fluid-filled system. [40] Magnetotelluric imaging showed structures similar to those revealed using seismic imaging. [41]

Geology

Volcanism in the Andes occurs in four distinct regions: the Northern Volcanic Zone, the Central Volcanic Zone, the Southern Volcanic Zone, and the Austral Volcanic Zone. [3] All but the last are geographically associated with the subduction of the Nazca Plate beneath the South American Plate; the Austral Volcanic Zone involves the subduction of the Antarctic Plate beneath the South American Plate. [12]

Magmatic processes important in the Central Andes include the partial melting of the subducting plate and its sediments and of mantle peridotite, and fractional crystallization in the crust. Large scale assimilation of the crust has not been reported at Lastarria. [3] [10]

The earliest volcanic activity on the west coast of South America goes back to the Jurassic, when the South Atlantic started to open. [10] During the late Cenozoic, a volcanic chain was formed on top of Mesozoic and Paleozoic rocks and reached a width of 100 to 150 kilometres (62 to 93 mi) in the area of Lastarria. This volcanism began 25 million years ago, and the rocks are mostly acidic rocks. [3]

Local

Lastarria is located on a basement formed by andesite–dacite volcanic rocks in the form of ignimbrites, lava flows, and lava domes. They are of Miocene to Pleistocene age. [17] [11]

Lastarria and Cordón del Azufre form a group of volcanoes on the Altiplano, on the border between Chile and Argentina. They were active during the Quaternary. [1] [4] Lastarria and Cordón del Azufre, together with some more local volcanic centres, may be part of a larger silicic volcanic complex that has not yet formed a caldera. This complex is characterized by a 500-metre (1,600 ft) high doming with a central depression. [6]

A major crustal lineament known as the Archibarca lineament intersects the main volcanic arc at Lastarria. Other volcanic centres such as Galán and ore deposits are also found on this lineament. [13] The intersection between this lineament and the arc may act as a weakness zone that focuses the ascent of magma. [42] Farther south lie volcanoes such as Wheelwright Caldera and Cerro Blanco, the last of which shows evidence of recent unrest. [13]

Geologic record

The Altiplano started to form during the Eocene, [43] when subduction of the Nazca Plate beneath the South American Plate caused compression along the plate margin. [44] Strong volcanism and tectonic uplift occurred between 15 and 20 million years ago. [45]

Composition

Lastarria is composed of andesite–dacite, both rich in potassium and characteristic of calc-alkaline magmas of the Central Volcanic Zone. [46] The appearance of Lastarria lavas is porphyritic. [12] Some rocks display "banding" features, implicating the mixing of different magmas during their formation. [47]

Phenocrysts include plagioclase in andesite with smaller amounts of amphibole, biotite, clinopyroxene, and orthopyroxene. Apatite and zircon form accessory minerals. Dacites have similar composition but also contain hornblende. [48] Olivine is found in the andesites and quartz in the dacites. [49]

Some chemical differences exist among the Negriales rocks, the Lastarria lavas, and the Lastarria pyroclastics. The Negriales rocks are the richest in silicon dioxide, and their trace element composition sharply diverges as well. [50] The Negriales rocks may originate from parental magmas that are different from the main Lastarria magmas. [51]

The petrogenesis of Lastarria rocks, like those of other volcanoes in the Central Volcanic Zone, involves the prolonged interaction with crustal rocks in magma chambers as well as the fractionation of certain minerals. Enriched lower crust and upper mantle might also contribute. Finally, the mixing of magma chamber contents with new and more mafic magma shortly before each eruption played an important role in rock genesis. [52] In the case of Lastarria, this mixing occurs in a stratified magma chamber, with active convection occurring between lighter and colder upper contents and hotter and denser lower contents. [53]

A number of alteration products are also present, some of which have been visualized by aerial imagery. Fumarole deposits contain encrustations and sublimates. [11]

Climate and vegetation

Lastarria has a montane climate characterized by extreme aridity as it is located at the intersection between the summer rain region of the Altiplano and the Atacama Desert. [32] Temperatures of −24 °C (−11 °F) [54] and precipitation of 20–50 millimetres per year (0.79–1.97 in/year) have been recorded on Lastarria, although the precipitation may be underestimated. [55]

Low bush vegetation exists in the area. [32]

Eruptive history

The South Spur edifice is the oldest structure found at Lastarria. The Negriales lava field formed later. The five craters of Lastarria proper formed in five different stages. [56] An alternative view holds that Negriales formed before the South Spur, and that the main edifice formed in ten different stages. [11] Block-and-ash flows, hot avalanches, lava domes, lava flows, and pyroclastic flows have all been involved in the activity of Lastarria. [56] Most deposits on the northern slopes were erupted during the last two stages, with the exception of several exposures of the older stages on the northwestern flank and the western "pink pyroclastic flow" deposit. [14] Overall, later and Holocene activity at Lastarria was highly explosive, unlike the more effusive earlier eruptions including the Negriales eruptions. [51] [32]

Potassium–argon dating of Lastarria has yielded ages of 600,000 ± 300,000 and less than 300,000 years ago. [1] The older date refers to the Negriales lava field, [17] which has also been dated at 400,000 116,000 ± 26,000 years ago. The South Spur is dated at 150,000 ± 50,000 years ago. The main edifice started forming 260,000 ± 20,000 years ago. [11] One andesite lava flow was dated at 51,000 ± 13,000 years ago by argon–argon dating. [32]

The lava dome on the northernmost crater rim is the youngest vent of Lastarria. [12] The youngest dated deposit is 2,460 ± 50/60 years old, but at least one younger pyroclastic flow is present. [15] [11] No historical eruptions are known. [1]

Noticeable thermal hotspots are visible from ASTER imagery and are associated with the fumarolic areas. [57] Temperatures observed at the hotspots are around 6 °C (279 K). [58]

Fumarolic activity

Vigorous fumarolic activity on the west slope of Lastarria. Note the yellow sulfur. Volcan Lastarria, Region de Antofagasta.JPG
Vigorous fumarolic activity on the west slope of Lastarria. Note the yellow sulfur.

Lastarria displays vigorous fumarolic activity [1] on the summit and down the northwestern slopes. [19] Such activity has been observed since the European discovery of Lastarria, in the late 19th century. [4] Lastarria is the only volcano in the area with ongoing fumarolic activity. [43] It manifests in fumaroles forming 15-centimetre (5.9 in) high chimneys, small cones reaching heights of 2 metres (6 ft 7 in), and 100 by 50 centimetres (39 by 20 in) fractures, as well as degassing through cracks and fissures on surfaces. Individual fumaroles have been found in the craters, on the crater edges, and on the slopes. A northwest–southeast striking fracture is associated with some of the fumaroles. [19] [17] Four different fumarole fields have been found, one along this fissure on the northwestern slope at altitudes of about 4,950 to 5,140 metres (16,240 to 16,860 ft), two on the rims of the fourth crater, and one in the fifth crater. [56] [32] The fissure field is the largest, covering a surface area of 0.023 square kilometres (0.0089 sq mi). [59]

The fumaroles release gases with temperatures ranging from 80 to 408 °C (176 to 766 °F). Carbon dioxide is the most important non-hydrous component of the gases; other components are hydrogen in variable amounts, hydrogen chloride, hydrogen fluoride, hydrogen sulfide, and variable amounts of nitrogen and sulfur dioxide. Additional components are alkanes, alkenes, argon, carbon monoxide especially in hotter fumaroles, helium, methane, and oxygen. The composition of the fumaroles indicates that most gases are of magmatic origin with little contribution from the atmosphere. [60] Likewise, most water comes from the magma rather than from precipitation, as indicated by the oxygen isotope ratios. [61] It is likely that the arid climate of the region reduces the input of meteoric water to the volcanic system. [62]

Of five volcanoes analyzed in 2012 (Lascar, Lastarria, Ollague, Putana, and San Pedro), Lastarria had the highest flux rates. Individual gas fluxes in tons per day are registered as: [59]

Volcano Carbon dioxide Hydrogen bromide Hydrogen chloride Hydrogen fluoride Hydrogen sulfide Sulfur dioxide Water
Lascar5340.151999.4305545,192
Lastarria9730.63855.817488411,059
Ollague150
Putana68.5
San Pedro161

The composition of Lastarria's gases has changed over time, with an increase in the magmatic component between 2009 and 2012, which may be due either to different measurement methods or to changes in the volcanic activity at Lastarria. [63] Decreased temperatures have been observed after rainfall. [64]

The gases of Lastarria come from a geothermal system and, with temperatures ranging from 280 to 370 °C (536 to 698 °F) and 560 to 680 °C (1,040 to 1,256 °F), supply the colder and hotter fumaroles, respectively. [65] In turn, a magma system at depths of 7 to 15 kilometres (4.3 to 9.3 mi) underpins and feeds this geothermal system. [66] During their rise, the gases interact with the rocks of the surrounding country and with aquifers. [67]

Ground uplift

InSAR observations performed in the years 1998 to 2000 have yielded evidence of a pattern of ground uplift centered between Lastarria and Cordón del Azufre. This pattern, also known as "Lazufre", [68] covers a surface area of 45 by 37 kilometres (28 by 23 mi). [17] This uplift appears to be caused by the injection of magma at depth, with a pattern of progressively increasing flux between 2003 and 2006. [69] The source of this uplift appears to lie at depths of 9 to 17 kilometres (5.6 to 10.6 mi), [43] [13] later recalculated at 2 to 14 kilometres (1.2 to 8.7 mi). [38] This uplift may have been ongoing for about 400,000 years and has influenced the final position of lava flows of Lastarria and other volcanoes in the area. [70]

Ground uplift has been detected at Lastarria itself, [68] amounting to 9 millimetres per year (0.35 in/year). [71] The uplifting region is 6 kilometres (3.7 mi) wide, smaller than Lazufre. [68] The Lastarria uplift started later than the Lazufre uplift and may be influenced by the latter. [71] Possibly, magma injected into a Lazufre magma chamber is influencing the Lastarria hydrothermal system, [6] with changes in fumarole output observed in 2006-2012. [72] Modelling indicates that the source of this uplift lies at a depth of about 1,000 metres (3,300 ft) and has the shape of a sphere. [17] Another estimate places the source inside the volcanic edifice and assumes a size of 230 to 360 metres (750 to 1,180 ft), with the volume increasing by about 8,000 to 18,000 cubic metres per year (280,000 to 640,000 cu ft/a). [20]

Ground uplift is still underway but with a slowdown between 2006 and 2016. [73] At other volcanoes, such uplift has been associated with changes in fumarolic activity or even the start of an eruption. [74]

Threats

The volcano is in a remote area and thus constitutes little risk to human settlements. [67] The closest populations are at Mina Vaquillas, Mina El Guanaco, and Campamento Pajonales. [15]

The Chilean SERNAGEOMIN published a volcano alert rating for Lastarria. [75] A permanent seismometer was installed on the volcano in late 2013. [73] It is considered the 45th most dangerous volcano in Chile. [15]

See also

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Socompa is a large stratovolcano at the border of Argentina and Chile. Part of the Chilean and Argentine Andean Volcanic Belt (AVB), it is part of the Central Volcanic Zone, one of the various segments of the AVB. This part of the Andean volcanic arc begins in Peru and runs first through Bolivia and Chile, and then through Argentina and Chile, and contains about 44 active volcanoes. Socompa lies close to the pass of the same name, where the Salta-Antofagasta railway crosses the border.

Lascar (volcano) volcano (stratovolcano)

Lascar is a stratovolcano within the Central Volcanic Zone of the Andes, a volcanic arc that spans the countries of Peru, Bolivia, Argentina and Chile. It is the most active volcano in the region, with records of eruptions going back to 1848. It is composed of two separate cones with several summit craters. The westernmost crater of the eastern cone is presently active. Volcanic activity is characterized by constant release of volcanic gas and occasional vulcanian eruptions.

Nevado de Longaví mountain in Chile

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.

Aucanquilcha mountain in Antofagasta Region Chile

Aucanquilcha(pronounced: OW-kahn-KEEL-chuh) is a massive stratovolcano located in the Antofagasta Region of northern Chile, just west of the border with Bolivia and within the Alto Loa National Reserve. Part of the Central Volcanic Zone of the Andes, the stratovolcano has the form of a ridge with a maximum height of 6,176 metres (20,262 ft). The volcano is embedded in a larger cluster of volcanoes known as the Aucanquilcha cluster. This cluster of volcanoes was formed in stages over eleven million years of activity with varying magma output, including lava domes and lava flows. Aucanquilcha volcano proper is formed from four units that erupted between 1.04–0.23 million years ago. During the ice ages, both the principal Aucanquilcha complex and the other volcanoes of the cluster were subject to glaciation, resulting in the formation of moraines and cirques.

Ollagüe mountain shared by Bolivia and Chile

Ollagüe or Ullawi is a massive andesite stratovolcano in the Andes on the border between Bolivia and Chile, within the Antofagasta Region of Chile and the Potosi Department of Bolivia. Part of the Central Volcanic Zone of the Andes, its highest summit is 5,868 metres (19,252 ft) above sea level and features a summit crater that opens to the south. The western rim of the summit crater is formed by a compound of lava domes, the youngest of which features a vigorous fumarole that is visible from afar.

Tacora mountain in Parinacota Province, Chile; geonames ID = 3868151

Tacora is a stratovolcano located in the Andes of the Arica y Parinacota Region of Chile. Bordering Peru, it is the northernmost volcano of Chile. It is part of the Central Volcanic Zone in Chile, one of the four volcanic belts of the Andes. The Central Volcanic Zone has several of the highest volcanoes in the world. Tacora itself is a stratovolcano with a caldera and a crater. The youngest radiometric age is 50,000 years ago and it is heavily eroded by glacial activity.

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.

Uturunku stratovolcano

Uturunku is a dormant volcano in the Cordillera de Lípez in Potosí Department, Bolivia. It is located in the Sur Lípez Province, San Pablo de Lípez Municipality. It is in the Central Volcanic Zone of the Andes, and its highest summit is 6,008 metres (19,711 ft) above sea level. The volcano has two summits, with a fumarole field between them. The volcano's landforms include lava domes and lava flows.

El Laco mountain in Chile

El Laco is a volcanic complex in the Antofagasta Region of Chile. It is directly south of the Cordón de Puntas Negras volcanic chain. Part of the Central Volcanic Zone of the Andes, it is a group of seven stratovolcanoes and a caldera. It is about two million years old. The main summit of the volcano is a lava dome called Pico Laco, which is variously reported to be 5,325 metres (17,470 ft) or 5,472 metres (17,953 ft) high. The edifice has been affected by glaciation, and some reports indicate that it is still fumarolically active.

Guallatiri mountain in Parinacota Province Chile

Guallatiri is a 6,071-metre-high (19,918 ft) volcano in Chile. It is located southwest of the Nevados de Quimsachata volcanic group and is sometimes considered to be part of that group. It is a stratovolcano with fumaroles around the summit, which may be either a lava dome or a pyroclastic cone. The lower flanks of the volcano are covered by lava flows and lava domes; the volcano has erupted mainly dacite along with andesite and rhyolite.

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).

Laguna del Maule (volcano) mountain in Chile

Laguna del Maule is a volcanic field in the Andes mountain range of Chile, close to, and partly overlapping, the Chile-Argentina frontier. The bulk of the volcanic field is in the Talca province of Chile's Maule Region. It is a segment of the Southern Volcanic Zone, part of the Andean Volcanic Belt. Many of the volcanic centres in the Laguna del Maule volcanic field formed during postglacial times, after glaciers had retreated from the area. This activity has generated cones, lava domes, lava coulees and lava flows which surround Laguna del Maule lake. The field gets its name from the lake which is also the source of the Maule river. Some of the volcanic centres were active during and before the last glaciation; at least three caldera formation events are associated with the system.

Juan de la Vega is a maar in Chile. It is located in the north-central Andes.

Olca-Paruma geographical object

Olca-Paruma is a volcanic complex in Chile. Lying on the border between Chile and Bolivia, it is formed by an east-west alignment of volcanoes. From west to east, these are Cerro Paruma, Volcan Paruma, Olca, and Mencheca or Michincha. Aside from the mines of Ujina, Rosario, and Quebrada Blanca, the area is sparsely populated.

Sabancaya Peruvian stratovolcano

Sabancaya is an active 5,976-metre-high (19,606 ft) stratovolcano in the Andes of southern Peru, about 70 kilometres (43 mi) northwest of Arequipa. It is considered part of the Central Volcanic Zone of the Andes, one of the three distinct volcanic belts of the Andes. The Central Volcanic Zone includes a number of volcanoes, some of which like Huaynaputina have had large eruptions and others such as Sabancaya and Ubinas have been active in historical time. Sabancaya forms a volcanic complex together with Hualca Hualca to the north and Ampato to the south and has erupted andesite and dacite. It is covered by a small ice cap which leads to a risk of lahars during eruptions.

Apacheta-Aguilucho volcanic complex

Apacheta-Aguilucho volcanic complex is a volcanic complex in Chile. It consists of two volcanoes Cerro Apacheta and Cerro Aguilucho, which are constructed mainly by lava flows and surrounded by outcrops of lava. A sector collapse and its landslide deposit are located on Apacheta's eastern flank. Two lava domes are associated with the volcanic complex, Chac-Inca and Pabellón.

Tata Sabaya mountain

Tata Sabaya is a 5,430-metre (17,810 ft) high volcano in Bolivia. It is part of the Central Volcanic Zone, one of several volcanic belts in the Andes which are separated by gaps without volcanic activity. This section of the Andes was volcanically active since the Jurassic, with an episode of strong ignimbritic volcanism occurring during the Miocene. Tata Sabaya lies in a thinly populated region north of the Salar de Coipasa salt pan.

Ubinas volcano in Peru

Ubinas is a stratovolcano in the Moquegua Region of southern Peru, 60 kilometres (37 mi) east of the city of Arequipa. Part of the Central Volcanic Zone of the Andes, it is 5,672 metres (18,609 ft) above sea level. The volcano's summit is cut by a 1.4-kilometre (0.87 mi) wide and 150-metre (490 ft) deep caldera, which itself contains a smaller crater. Below the summit, Ubinas has the shape of an upwards-steepening cone with a prominent notch on the southern side. The gently sloping lower part of the volcano is also known as Ubinas I and the steeper upper part as Ubinas II; they represent different stages in the geologic history of Ubinas.

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