Isluga () is a

stratovolcano A stratovolcano, also known as a composite volcano, is a conical volcano built up by many layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with a summit crater and p ...

located in Colchane, west of the

Chile Chile, officially the Republic of Chile, is a country in the western part of South America. It is the southernmost country in the world, and the closest to Antarctica, occupying a long and narrow strip of land between the Andes to the eas ...

Bolivia , image_flag = Bandera de Bolivia (Estado).svg , flag_alt = Horizontal tricolor (red, yellow, and green from top to bottom) with the coat of arms of Bolivia in the center , flag_alt2 = 7 × 7 square p ...

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 The Tarapacá Region ( es, Región de Tarapacá, ) is one of Chile's 16 first-order administrative divisions. It comprises two provinces, Iquique and Tamarugal. It borders the Chilean Arica and Parinacota Region to the north, Bolivia's Orur ...

Geography

Isluga lies in the commune of Colchane,

Iquique Province Iquique Province ( es, Provincia de Iquique) is one of two provinces in the northern Chilean region of Tarapacá. Its capital is the port city of Iquique. History Until October 2007, the Province of Iquique was composed of 7 communes: Alto Hospi ...

of the Tarapaca Region, Chile. The volcano is part of the Volcán Isluga National Park, which was created in 1985. The volcano can be accessed through the International Route 55. Cabaray

Isluga is part of the Andean Volcanic Belt, the volcanic zone on the western side of

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere at the northern tip of the continent. It can also be described as the souther ...

where the

Nazca plate The Nazca Plate or Nasca 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 ...

is subducted beneath the

South American plate The South American Plate is a major tectonic plate which includes the continent of South America as well as a sizable region of the Atlantic Ocean seabed extending eastward to the African Plate, with which it forms the southern part of the Mi ...

. Isluga is part of the segment named the

Central Volcanic Zone 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 Americ ...

. In the Tarapaca region other volcanoes have been active in the

Holocene 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 togeth ...

, such as Guallatiri,

Parinacota Parinacota (in hispanicized spelling), Parina Quta or Parinaquta ( Aymara, ''parina'' flamingo, ''quta'' lake, "flamingo lake", other hispanicized spellings ''Parinaccota, Parinajota'') may refer to: Lakes * Parinaquta (Carabaya), in Peru, Puno ...

and Taapaca. There are several volcanic units in the Isluga area. A pre-Isluga unit containing Cabay volcano, northeastern Carcanchuni and southern Cerro Blanco are not stratigraphically controlled. The Enquelga unit is the first Isluga unit proper. Further, Isluga and Tata Sabaya and some other volcanoes form a lineament which may coincide with the suture between the Chilenia terrane and the Arequipa-Antofalla block. Being about high over its base, Isluga has five craters, a main crater wide at the end of snowcovered summit ridge and underwent caldera collapse. The volcano itself is constructed from

lava dome In volcanology, a lava dome is a circular mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruption ...

s and flows on top of

Miocene The Miocene ( ) is the first geological epoch of the Neogene Period and extends from about (Ma). The Miocene was named by Scottish geologist Charles Lyell; the name comes from the Greek words (', "less") and (', "new") and means "less recent" ...

ignimbrite Ignimbrite is a type of volcanic rock, consisting of hardened tuff. Ignimbrites form from the deposits of pyroclastic flows, which are a hot suspension of particles and gases flowing rapidly from a volcano, driven by being denser than the surro ...

s. Several stages of eruptive activity are recognized, some of them exposed through erosion. A northwestern

debris avalanche Debris flows are geological phenomena in which water-laden masses of soil and fragmented rock rush down mountainsides, funnel into stream channels, entrain objects in their paths, and form thick, muddy deposits on valley floors. They generall ...

has been found on Isluga, on top of which the recent volcano is constructed. The fumarolically active crater region has been buried with surge deposits from

phreatomagmatic Phreatomagmatic eruptions are volcanic eruptions resulting from interaction between magma and water. They differ from exclusively magmatic eruptions and phreatic eruptions. Unlike phreatic eruptions, the products of phreatomagmatic eruptions conta ...

activity, and the northern ridge is covered by Holocene lavas. A glaciated dacitic lava flow is dated 0.096±0.006 Ma by K-Ar analysis. North of Isluga lies the dissected Quimsachatas volcano, which has been dated at 0.566±0.017 Ma. Both the summit crater and the area below the crater on the southern flank are faintly fumarolically active, with yellow

sulfur Sulfur (or sulphur in British English) 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 formul ...

deposits observed. The fumaroles appear to produce water vapour.

Eruptive activity

Isluga erupted in February 1878 following the 1878 Tarapaca earthquake. Voluminous lava emissions destroyed the towns of Carima, Cariquima, Chiapa, Libiza and Sotoca, and the eruption was accompanied with strong earthquake activity in Cariquima. Other eruptions have been reported in August 1863, a major eruption in 1868 and August 1869, 1877 and 1878 and minor eruptions in 1863 and 1885. Isluga last erupted in 1913, but ongoing volcanic earthquake activity has been observed. The volcano hosts some of the Andes' largest thermal anomalies in satellite images and increased fumarolic activity in 2002–2003 was reported. Some earthquake activity may be associated with neighbouring hydrothermal fields. A

phreatic eruption A phreatic eruption, also called a phreatic explosion, ultravulcanian eruption or steam-blast eruption, occurs when magma heats ground water or surface water. The extreme temperature of the magma (anywhere from ) causes near-instantaneous evapo ...

was observed in 2005; whether it was related to the

2005 Tarapacá earthquake The 2005 Tarapacá earthquake occurred on June 13 at 22:44:33 UTC (18:44:33 local time). Its epicenter was located near Mamiña, in northern Chile about 125 km east-northeast of Iquique, affecting the Tarapacá Region and adjacent parts of ...

half a year earlier is unclear.

Petrology

Isluga's lavas are

andesitic Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained ( aphanitic) to porphyritic in texture, and is composed predomi ...

to trachyandesitic in composition with SiO₂ contents between 56-61%. The andesites are porphyritic with more than half

phenocrysts 300px, Swiss side of the Mont Blanc massif, has large white plagioclase phenocrysts, triclinic minerals that give trapezoid shapes when cut through). 1 euro coins, 1 euro coin (diameter 2.3 cm) for scale. A phenocryst is an early forming, relativ ...

and high

potassium Potassium is the chemical element with the symbol K (from Neo-Latin '' kalium'') and atomic number19. Potassium is a silvery-white metal that is soft enough to be cut with a knife with little force. Potassium metal reacts rapidly with atmosp ...

content (2.7-3.6%), moderate

aluminium Aluminium (aluminum in AmE, American and CanE, Canadian English) is a chemical element with the Symbol (chemistry), symbol Al and atomic number 13. Aluminium has a density lower than those of other common metals, at approximately o ...

and high

magnesium Magnesium is a chemical element with the symbol Mg and atomic number 12. It is a shiny gray metal having a low density, low melting point and high chemical reactivity. Like the other alkaline earth metals (group 2 of the periodic ...

, although some

hornblende Hornblende is a complex inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common in igneous and metamorphic ro ...

s have high Na/K ratios. The petrology of the Isluga lineament lavas indicates an origin either in 3-5% partial melting of the mantle, or by a 15% partial melting of a

granite Granite () is a coarse-grained ( phaneritic) intrusive igneous rock composed mostly of quartz, alkali feldspar, and plagioclase. It forms from magma with a high content of silica and alkali metal oxides that slowly cools and solidifies und ...

-containing mantle with subsequent fractionation of

mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks includ ...

components.

Climate

The climate of the region varies by altitude; between lies a borderline desert area with temperatures ranging from below to , with most precipitation () falling in summer. A similar climate lies on the eastern part of the mountains between , with precipitation. Above lies a region of steppe vegetation with temperatures of and about precipitation also during summer, and above lies perennial snow.

Mythology and archeology

Also named Laram Qhawani, the volcano dominating the village of Enquelca is a sacred mountain, responsible for health, wealth and rain. It is considered a female spirit married to Cabarray. While no archeological remains have been found on its summit, a triangular stone structure resembles the patterns drawn when making offerings to spirits. One of the ends of the triangular structure points to

Cerro Cariquima Cerro Cariquima is a high volcano in the Andes. It is a sacred mountain of the territory, featuring a mountain sanctuary. The edifice presently has a volume of and based on erosion an age of 4.6 million years has been inferred. The true age o ...

, another sacred mountain. Another archeological place was found at ca. 5,200 m (17,056') on the southern ridge, probably serving as protection against wind and with a niche in the walls that probably served ritual purposes.

Threats