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Incahuasi (; possibly from Quechua language: inka Inca Empire, wasi house)Diccionario Quechua - Español - Quechua, Academía Mayor de la Lengua Quechua, Gobierno Regional Cusco, Cusco 2005 (Quechua-Spanish dictionary)Teofilo Laime Ajacopa, Diccionario Bilingüe Iskay simipi yuyayk'ancha, La Paz, 2007 (Quechua-Spanish dictionary) is a volcano mountain in the Andes of South America. It lies on the border of the Catamarca Province of Argentina and the Atacama Region of Chile. Incahuasi has a summit elevation of above sea level.
The volcano consists of a caldera and two . Four volcanic cone located to the northeast have produced basalt-andesite lava flows that cover an area of .
Incahuasi is located northeast of Ojos del Salado, 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 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 and Miocene, 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 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.
Incahuasi has two Volcanic crater, 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 . 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. 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 cone]]s can be found. They have covered with lava but they are probably an independent volcanic system, similar to other regional [[mafic]] 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.
The four cones northeast of the principal volcano have erupted basaltic andesite. Likewise, have erupted magnesium-rich basaltic andesite. Minerals contained in these rocks include clinopyroxene and olivine.
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.
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 effect of the Subandean Ranges, which block moisture from the Atlantic Ocean.
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, 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 indicate an extinct volcano, 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.
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