Nevado San Francisco

Last updated
Nevado San Francisco
Vegas de San Francisco.jpg
Highest point
Elevation 6,016 m (19,738 ft) [1]
Coordinates 26°55′S68°15′W / 26.917°S 68.250°W / -26.917; -68.250
Geography
Location Argentina-Chile
Parent range Andes
Geology
Age of rock 1.34 - 1.32 million years ago
Mountain type Stratovolcano
Last eruption Unknown

Nevado San Francisco, or Cerro San Francisco (Spanish pronunciation:  [saɱ fɾanˈθisko] ), 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 6,000 m (19,700 ft) peaks in the area, of which the chief is the Ojos del Salado.

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).

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.

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.

The volcano is part of the Central Volcanic Zone of the Andes. [2] It is composed from andesite with the exception of basaltic cones and lava flows on the eastern side. These cones are part of the Peinado lineament and a sample was dated 200,000 years ago by argon chronology. [3] :74-75 They are noteworthy for their olivine phenocrysts. [2] One lava flow less than one million years old reaches a length of 11 kilometres (6.8 mi). [4] The western slopes contain dacitic lava domes. [5] On the summit lie two circle-shaped constructs, of Inca or Formative period ages. [3] :351, 432

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.

Olivine Magnesium iron silicate solid solution series mineral

The mineral olivine is a magnesium iron silicate with the formula (Mg2+, Fe2+)2SiO4. Thus it is a type of nesosilicate or orthosilicate. It is a common mineral in Earth's subsurface but weathers quickly on the surface.

Phenocryst

A phenocryst is an early forming, relatively large and usually conspicuous crystal distinctly larger than the grains of the rock groundmass of an igneous rock. Such rocks that have a distinct difference in the size of the crystals are called porphyries, and the adjective porphyritic is used to describe them. Phenocrysts often have euhedral forms, either due to early growth within a magma, or by post-emplacement recrystallization. Normally the term phenocryst is not used unless the crystals are directly observable, which is sometimes stated as greater than .5 millimeter in diameter. Phenocrysts below this level, but still larger than the groundmass crystals, are termed microphenocrysts. Very large phenocrysts are termed megaphenocrysts. Some rocks contain both microphenocrysts and megaphenocrysts. In metamorphic rocks, crystals similar to phenocrysts are called porphyroblasts.

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Incahuasi mountain in Argentina

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Quetrupillán mountain in Cautín Province Chile

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Tacora

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Nevado Tres Cruces mountain

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Los Patos mountain in Argentina

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Lastarria mountain in Argentina

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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.

Wheelwright caldera is a caldera in Chile. It is variously described as being between 11 kilometres (6.8 mi) and 22 kilometres (14 mi) wide and lies in the Central Volcanic Zone of the Andes. A lake lies within the caldera, which is among the largest of the Central Andes. The caldera lies in the region of Ojos del Salado, the world's tallest volcano.

References

  1. Difrol Archived 2007-09-27 at the Wayback Machine.
  2. 1 2 Kay, Suzanne Mahlburg; Mpodozis, Constantino; Gardeweg, Moyra (2014-01-01). "Magma sources and tectonic setting of Central Andean andesites (25.5–28°S) related to crustal thickening, forearc subduction erosion and delamination". Geological Society, London, Special Publications. 385 (1): 310. doi:10.1144/SP385.11. ISSN   0305-8719.
  3. 1 2 Nevado de Incahuasi: The Archaeological Anatomy of a Sacred Mountain in the Andes. ProQuest. 2008. ISBN   978-1-109-06242-7.
  4. "Comunicación | Conicet". www.conicet.gov.ar (in Spanish). Retrieved 2017-07-07.
  5. Baker, P. E.; Gonzalez-Ferran, O.; Rex, D. C. (1987-02-01). "Geology and geochemistry of the Ojos del Salado volcanic region, Chile". Journal of the Geological Society. 144 (1): 89. doi:10.1144/gsjgs.144.1.0085. ISSN   0016-7649.

See also

"San Francisco". Global Volcanism Program . Smithsonian Institution.

Global Volcanism Program American research program

The Smithsonian Institution's Global Volcanism Program (GVP) documents Earth's volcanoes and their eruptive history over the past 10,000 years. The GVP reports on current eruptions from around the world as well as maintaining a database repository on active volcanoes and their eruptions. In this way, a global context for the planet's active volcanism is presented. Smithsonian reporting on current volcanic activity dates back to 1968, with the Center for Short-Lived Phenomena (CSLP). The GVP is housed in the Department of Mineral Sciences, part of the National Museum of Natural History, on the National Mall in Washington, D.C.

Smithsonian Institution Group of museums and research centers administered by the United States government

The Smithsonian Institution, also known simply as the Smithsonian, is a group of museums and research centers administered by the Government of the United States. It was founded on August 10, 1846 "for the increase and diffusion of knowledge". The institution is named after its founding donor, British scientist James Smithson. Originally organized as the "United States National Museum," that name ceased to exist as an administrative entity in 1967.