Incahuasi (; possibly from Quechua: ''inka''

Inca The Inca Empire, officially known as the Realm of the Four Parts (, ), was the largest empire in pre-Columbian America. The administrative, political, and military center of the empire was in the city of Cusco. The History of the Incas, Inca ...

, ''wasi'' house) is a

volcanic A volcano is commonly defined as a vent or fissure 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 fo ...

mountain in the

Andes The Andes ( ), Andes Mountains or Andean Mountain Range (; ) are the List of longest mountain chains on Earth, longest continental mountain range in the world, forming a continuous highland along the western edge of South America. The range ...

South America South America is a continent entirely in the Western Hemisphere and mostly in the Southern Hemisphere, with a considerably smaller portion in the Northern Hemisphere. It can also be described as the southern Subregion#Americas, subregion o ...

. 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 429,556 as per the , and covers an area of 102,602 km2. Its literacy rate is 95.5%. Neighbouring provinces are (clockwise, f ...

Argentina Argentina, officially the Argentine Republic, is a country in the southern half of South America. It covers an area of , making it the List of South American countries by area, second-largest country in South America after Brazil, the fourt ...

and the Atacama Region of

Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...

. 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 volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...

and two

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

es. Four pyroclastic cones located to the northeast have produced

basalt Basalt (; ) is an aphanite, 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 planetary surface, surface of a terrestrial ...

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 predomina ...

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 Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

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 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), as well as the current and most recent of the twelve periods of the ...

volcanoes, and lies in the southern sector of this zone; other volcanic zones in the Andes are the Northern Volcanic Zone, the Southern Volcanic Zone, and the Austral Volcanic Zone. 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 volcano, 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 overlapp ...

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, Nevado Tres Cruces, and El Solo, 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 and Nevado San Francisco, as well as the

Miocene The Miocene ( ) is the first epoch (geology), 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 mea ...

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 subducting in the Peru–Chile Trench. Geological evidence suggests that volcanism in the area dates back to the

Oligocene The Oligocene ( ) is a geologic epoch (geology), epoch of the Paleogene Geologic time scale, Period that extends from about 33.9 million to 23 million years before the present ( to ). As with other older geologic periods, the rock beds that defin ...

and

, when the main

volcanic arc A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the 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 The back-arc region is the area behind a volcanic arc. In island arc, island volcanic arcs, it consists of back-arc basins of oceanic crust with abyssal zone, abyssal depths, which may be separated by remnant arcs, similar to island arcs. In conti ...

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 A crater is a landform consisting of a hole or depression (geology), depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described ...

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 Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...

s less than wide and long extend down the volcano. They reach the Las Coladas salar east of Incahuasi. Two coulees extend north and east of the main crater. northeast of Incahuasi, four pyroclastic cones 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 include ...

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 silicate minerals#Inosilicates, 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 ...

and

pyroxene The pyroxenes (commonly abbreviated 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 ions of calcium (Ca), sodium (Na), iron ( ...

, but also trachyandesite and trachydacite. Lava flows on the main stratovolcano are dacitic. The four cones northeast of the principal volcano have erupted basaltic andesite. Likewise, parasitic cones have erupted magnesium-rich basaltic andesite. Minerals contained in these rocks include clinopyroxene and

olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...

. 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, 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 of the lower crust and subduction erosion.

Climate

Incahuasi does not have

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

s, but it does have at least temporary

snowpack Snowpack is an accumulation of snow that compresses with time and melts seasonally, often at high elevation or high latitude. Snowpacks are an important water resource that feed streams and rivers as they melt, sometimes leading to flooding. Snow ...

. 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 body of water, bodies of water (such as oceans and larg ...

effect of the Subandean Ranges, which block moisture from the

Atlantic Ocean The Atlantic Ocean is the second largest of the world's five borders of the oceans, oceanic divisions, with an area of about . It covers approximately 17% of Earth#Surface, Earth's surface and about 24% of its water surface area. During the ...

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 geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...

, 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 Chronological dating, date materials such as Rock (geology), rocks or carbon, in which trace radioactive impurity, impurities were selectively incorporat ...

indicate an

extinct volcano A volcano is commonly defined as a vent or fissure in the Crust (geology), crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and volcanic gas, gases to escape from a magma chamber below the surface. On Earth ...

, although activity at Andean volcanoes is known to occur with long rest phases between eruptions (reaching one million years). There are reports of fumarolic activity. The volcano is considered a potential geological hazard to Argentina and Chile, where the SERNAGEOMIN 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

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External links

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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