Incahuasi (; possibly from

Quechua Quechua may refer to: *Quechua people, several indigenous ethnic groups in South America, especially in Peru *Quechuan languages, a Native South American language family spoken primarily in the Andes, derived from a common ancestral language **So ...

: ''inka''

Inca The Inca Empire (also known as the Incan Empire and the Inka Empire), called ''Tawantinsuyu'' by its subjects, ( Quechua for the "Realm of the Four Parts", "four parts together" ) was the largest empire in pre-Columbian America. The adm ...

, ''wasi'' house) is a

volcanic A volcano 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. On Earth, volcanoes are most often found where tectonic plat ...

mountain in the

Andes The Andes, Andes Mountains or Andean Mountains (; ) are the longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range is long, wide (widest between 18°S – 20°S ...

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 sou ...

. It lies on the border of the

Catamarca Province Catamarca () is a province of Argentina, located in the northwest of the country. The province had a population of 334,568 as per the , and covers an area of 102,602 km2. Its literacy rate is 95.5%. Neighbouring provinces are (clockwise, fr ...

Argentina Argentina (), officially the Argentine Republic ( es, link=no, República Argentina), is a country in the southern half of South America. Argentina covers an area of , making it the List of South American countries by area, second-largest ...

and the Atacama Region of

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 ...

. Incahuasi has a summit elevation of above sea level. The volcano consists of a

caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcano eruption. When large volumes of magma are erupted over a short time, structural support for the rock above the magma chamber is ...

and two

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 peri ...

es. Four

pyroclastic cone Volcanic cones are among the simplest volcanic landforms. They are built by ejecta from a volcanic vent, piling up around the vent in the shape of a cone with a central crater. Volcanic cones are of different types, depending upon the nature and s ...

s located to the northeast have produced

basalt Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron (mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90 ...

andesite 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 predo ...

lava Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or ...

flows that cover an area of .

Geography and geology

Incahuasi lies on the border between

and

, close to Paso San Francisco. A major road crosses the border there.

Regional

Incahuasi is part of 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 America ...

of the

, together with about 110 other

Quaternary The 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 2.58 million year ...

volcanoes, and lies in the southern sector of this zone; other volcanic zones in the Andes are the

Northern 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 America ...

, the

Southern 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 America ...

, and the

Austral 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 America ...

. The history of volcanic activity of most of these volcanoes is poorly understood owing to the lack of dating; only a few historical eruptions have been recorded, such as an eruption at

Ojos del Salado Nevado Ojos del Salado is a dormant complex volcano in the Andes on the Argentina–Chile border. It is the highest volcano on Earth and the highest peak in Chile. The upper reaches of Ojos del Salado consist of several overlapping lava domes, ...

in 1993. Incahuasi is located northeast of

, the highest volcano in the world. Both volcanoes are found at the southern end of the Central Volcanic Zone. Together with El Fraile,

Cerro El Muerto Location Cerro el Muerto (sometimes El Muerto fully translated as ''The Dead One'' ") is a range or area at the border of Argentina and Chile. It has a height of . It's located at Atacama Region, Copiapó Province, at the Puna de Atacama. It o ...

, Nevado Tres Cruces, and

El Solo Cerro Solo is a large stratovolcano on the border between Argentina and Chile, west of Ojos del Salado with an elevation of metres. It consists of nine eruptive centers and is covered in light-colored rhyodacite pyroclastic flow deposits. Its ...

, they form a volcanic chain. The area is dominated by volcanoes that were active after 1.5 million years ago. Also located close to Incahuasi are

Falso Azufre Falso Azufre is a complex volcano at the border of Argentina and Chile. Falso Azufre is elongated in east–west direction and contains craters and lava domes; most craters have diameters of with the exception of the main crater, which is wid ...

and

Nevado San Francisco Nevado San Francisco, or Cerro San Francisco (), is a stratovolcano on the border between Argentina and Chile, located just southeast of San Francisco Pass. It is considered extinct and is one of the several peaks in the area, of which the chi ...

, as well as the

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 recen ...

Cerro Morocho and Cerro Ojo de Las Lozas volcanoes. It has been suggested that a perpendicular chain of volcanoes including Ojos del Salado may be the consequence of the

Juan Fernández Ridge The Juan Fernández Ridge is a volcanic island and seamount chain on the Nazca Plate. It runs in a west–east direction from the Juan Fernández hotspot to the Peru–Chile Trench at a latitude of 33° S near Valparaíso. The Juan Fernández I ...

subducting in the

Peru–Chile Trench The Peru–Chile Trench, also known as the Atacama Trench, is an oceanic trench in the eastern Pacific Ocean, about off the coast of Peru and Chile. It reaches a maximum depth of below sea level in Richards Deep () and is approximately long; ...

. Geological evidence suggests that volcanism in the area dates back to the

Oligocene The Oligocene ( ) is a geologic epoch of the Paleogene Period and extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that define the epoch are well identified but t ...

and

, when the main volcanic arc was located west in the Maricunga Belt. Between 9 and 6 million years ago, volcanic activity in the Maricunga Belt decreased and eventually ceased. Simultaneously, the

back-arc A back-arc basin is a type of geologic basin, found at some convergent plate boundaries. Presently all back-arc basins are submarine features associated with island arcs and subduction zones, with many found in the western Pacific Ocean. Most of ...

experienced increased volcanic activity. Beginning 8.3 million years ago, there was a change in tectonic regime from an east-west compression to a north-south stretching, which led to a change in the alignments of the volcanoes.

Local

Incahuasi is formed by a

wide. Two coalesced

es formed within the caldera and have a diameter of . A

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 eruptions ...

is located on the eastern flank. The volcano has a volume of about and covers a surface area of about . With a height of , Incahuasi is the 12th-highest mountain in

and one of the world's highest volcanoes. Incahuasi has two

crater Crater may refer to: Landforms * Impact crater, a depression caused by two celestial bodies impacting each other, such as a meteorite hitting a planet * Explosion crater, a hole formed in the ground produced by an explosion near or below the surf ...

s, a summit crater and an arcuate crater on the eastern slope that contains a lava dome. The summit crater has dimensions of and is embedded within a summit plateau. Subsidiary vents conversely are associated with

fissure vent A fissure vent, also known as a volcanic fissure, eruption fissure or simply a fissure, is a linear volcanic vent through which lava erupts, usually without any explosive activity. The vent is often a few metres wide and may be many kilo ...

s. The edifice appears to consist of two overlapping volcanoes. The western and southwestern slopes of Incahuasi are dotted with lava domes, which are more subdued than on other volcanoes in the region.

Lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a moon onto its surface. Lava may be erupted at a volcano or through a fracture in the crust, on land or un ...

s less than wide and long extend down the volcano. They reach the Las Coladas salar east of Incahuasi. Two

coulees Coulee, or coulée ( or ) is a term applied rather loosely to different landforms, all of which refer to a kind of valley or drainage zone. The word ''coulee'' comes from the Canadian French ''coulée'', from French ''couler'' 'to flow'. The ...

extend north and east of the main crater. northeast of Incahuasi, four

s can be found. They have covered with lava but they are probably an independent volcanic system, similar to other regional

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 in ...

volcanoes. On Incahuasi's eastern flank lies a major lava dome and a field of lava flows. Incahuasi rises over a surface with elevations of . The volcano is surrounded by a field of small volcanoes that is known as the Incahuasi field; it contains 19 small volcanoes with a total rock volume of , which were active during the last 1 million years. File:Incahuasi and el fraile plus laguna verde chile.jpg, Incahuasi is the volcano at the left and El Fraile immediately right. The green lake is Laguna Verde File:Volcán Incahuasi edit.jpg, Incahuasi from Las Grutas. The eastern lava domes and the northeastern monogenetic volcanoes are clearly visible.

Composition

Like many Andean volcanoes, Incahuasi has erupted

containing

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 rock ...

and

pyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe I ...

, but also

trachyandesite Trachyandesite is an extrusive igneous rock with a composition between trachyte and andesite. It has little or no free quartz, but is dominated by sodic plagioclase and alkali feldspar. It is formed from the cooling of lava enriched i ...

and trachydacite. Lava flows on the main stratovolcano are

dacitic Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyol ...

. The four cones northeast of the principal volcano have erupted

basaltic andesite Basaltic andesite is a volcanic rock that is intermediate in composition between basalt and andesite. It is composed predominantly of augite and plagioclase. Basaltic andesite can be found in volcanoes around the world, including in Central Am ...

. Likewise, parasitic cones have erupted magnesium-rich basaltic andesite. Minerals contained in these rocks include

clinopyroxene The pyroxenes (commonly abbreviated to ''Px'') are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents calcium (Ca), sodium (Na), iron (Fe I ...

and

olivine The mineral olivine () is a magnesium iron silicate with the chemical formula . It is a type of nesosilicate or orthosilicate. The primary component of the Earth's upper mantle, it is a common mineral in Earth's subsurface, but weathers qui ...

. The occurrence of such basic magmas in a volcanic setting dominated by dacites appears to be a consequence of local tectonics, which involve the extension of the crust compared to the compressional regime farther west. Originating in the

mantle A mantle is a piece of clothing, a type of cloak. Several other meanings are derived from that. Mantle may refer to: *Mantle (clothing), a cloak-like garment worn mainly by women as fashionable outerwear **Mantle (vesture), an Eastern Orthodox ve ...

, the magmas quickly ascended in faults and were contaminated by crustal material. The mantle itself had been modified before by crustal material added by

delamination Delamination is a mode of failure where a material fractures into layers. A variety of materials including laminate composites and concrete can fail by delamination. Processing can create layers in materials such as steel formed by rolling a ...

of the lower crust and subduction erosion.

Climate

Incahuasi does not have

glacier A glacier (; ) is a persistent body of dense ice that is constantly moving under its own weight. A glacier forms where the accumulation of snow exceeds its ablation over many years, often centuries. It acquires distinguishing features, such a ...

s, but it does have at least temporary

snowpack Snowpack forms from layers of snow that accumulate in geographic regions and high elevations where the climate includes cold weather for extended periods during the year. Snowpacks are an important water resource that feed streams and rivers as t ...

. Even the crater does not support the development of glaciers. Average precipitation at Incahuasi is about . The volcano lies south of the so-called "Arid Diagonal", and most precipitation falls during winter. This aridity is caused by the

rain shadow A rain shadow is an area of significantly reduced rainfall behind a mountainous region, on the side facing away from prevailing winds, known as its leeward side. Evaporated moisture from water bodies (such as oceans and large lakes) is ca ...

effect of the Subandean Ranges, which block moisture from the

Atlantic Ocean The Atlantic Ocean is the second-largest of the world's five oceans, with an area of about . It covers approximately 20% of Earth's surface and about 29% of its water surface area. It is known to separate the " Old World" of Africa, Europe ...

Eruption history

One andesitic lava flow on the northwestern slope of Incahuasi has yielded two ages, one of 1.15 ± 0.5 million years ago and another of 710,000 ± 80,000 years ago. Based on their preservations, the lava flows appear to be of roughly comparable ages. Additional ages were obtained on the main edifice, 1.57 ± 0.1 million years ago, 1.14 ± 0.37 million years ago, and 1.00 ± 0.13 million years ago. Parasitic cones were active over 500,000 years ago. These include the lava dome and lava flow fields (760,000 ± 90,000 and 740,000 ± 50,000 years ago, respectively) and a lava flow from the pyroclastic cones, which has been dated to 350,000 ± 30,000 years ago. Volcanic activity at Incahuasi may have continued into 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 ...

, considering the young appearance of its eruption products such as lava flows in the summit region and on the southern slopes; the old ages obtained by

radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon, in which trace radioactive impurities were selectively incorporated when they were formed. The method compares ...

indicate an

extinct volcano A volcano 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. On Earth, volcanoes are most often found where tectonic plates a ...

, although activity at Andean volcanoes is known to occur with long rest phases between eruptions (reaching one million years). There are reports of

fumarolic A fumarole (or fumerole) is a vent in the surface of the Earth or other rocky planet from which hot volcanic gases and vapors are emitted, without any accompanying liquids or solids. Fumaroles are characteristic of the late stages of volc ...

activity. The volcano is considered a potential geological hazard to Argentina and Chile, where the

SERNAGEOMIN 250px, Sernageomin building in Providencia, Santiago. The National Geology and Mining Service ( es, Servicio Nacional de Geología y Minería; SERNAGEOMIN) is a Chilean government agency. Its function is to provide geological information and adv ...

hazard maps identify it as a potential threat. The remoteness of the volcano means that future eruptions are unlikely to impact populated areas, however, other than . It was rated 27th out of 38 Argentine-Chilean volcanoes in dangerousness. File:Volcán Incahuasi.jpg, View from Las Grutas File:Incahuasi, -18 Jan. 2010 a.jpg,

Climbing history

The mountain was first climbed by

people. In 1912, Walter Penck climbed the mountain. Legend has it that a railway engineer named Edward Flint ascended the mountain between 1854 and 1859.

Archaeology

In 1913, an Inca ceremonial structure was found on the summit of Incahuasi. Another archaeological site, "Fiambalá-1", lies at its foot. Other Inca archaeological sites in the region appear to have had functions correlated to that of the Incahuasi site.

References

Sources

* * * * * * * *

External links

*
Incahuasi

"Cerro de Incahuasi, Argentina/Chile" on Peakbagger
{{Andean volcanoes Volcanoes of Atacama Region Mountains of Argentina Mountains of Chile Volcanoes of Catamarca Province Polygenetic volcanoes Argentina–Chile border International mountains of South America Six-thousanders of the Andes Mountains of Atacama Region Mountains of Catamarca Province Pleistocene stratovolcanoes