|Nevado San Francisco|
|Elevation||6,016 m (19,738 ft)|
|Age of rock||1.34 - 1.32 million years ago|
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.
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, 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, 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. 74-75 They are noteworthy for their olivine phenocrysts. One lava flow less than one million years old reaches a length of 11 kilometres (6.8 mi). The western slopes contain dacitic lava domes. On the summit lie two circle-shaped constructs, of Inca or Formative period ages. :351, 432It 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. :
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.
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.
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.
Nevado Ojos del Salado is a stratovolcano in the Andes on the Argentina–Chile border and the highest active volcano in the world at 6,893 m (22,615 ft). It is also the second highest mountain in the Western Hemisphere and Southern Hemisphere and the highest in Chile. It is located about 600 km (370 mi) north of Aconcagua, the highest mountain in the Western Hemisphere, at 6,961 m (22,838 ft).
Pomerape is a stratovolcano lying on the border of northern Chile and Bolivia. It is part of the Payachata complex of volcanoes, together with Parinacota Volcano to the south. The name "Payachata" means "twins" and refers to their appearance. It hosts glaciers down to elevations of 5,300–5,800 metres (17,400–19,000 ft), lower on the northern slope.
Falso Azufre is a complex volcano at the border of Argentina and Chile.
Cerro Tipas is a massive complex volcano in the Andes, located in northwestern Argentina. It is just southwest of Ojos del Salado, the highest volcano in the world. Tipas itself is perhaps the third highest active volcano in the world, and it consists of stratovolcanoes, lava domes, and lava flows. Its summit is 6,668 metres (21,877 ft) above sea level and the complex covers a surface area of 25 square kilometres (9.7 sq mi). There are reports of fumarolic activity, and de Silva and Francis (1991) considered that the volcano was last active in the Holocene. The Tipas-Cerro Bayo complex was active 2.9-1.2 million years ago with dacites and rhyolites. Magma composition is typical for Andean stratovolcanoes. Tomographic studies of the underlying crust indicate a pattern of seismic attenuation beneath Tipas.
Monte Pissis is an extinct volcano on the border of La Rioja and Catamarca provinces, Argentina, 25 km (16 mi) from the Chilean border. The mountain is the third-highest in the Western Hemisphere, and is located about 550 km (340 mi) north of Aconcagua. Monte Pissis is named after Pedro José Amadeo Pissis, a French geologist who worked for the Chilean government. Due to its location in the Atacama Desert, the mountain has very dry conditions but there is an extensive glacier
Incahuasi is a volcanic mountain in the Andes of South America. It lies on the border of the Argentine province of Catamarca, and the Atacama Region of Chile. Incahuasi has a summit elevation of 6,621 metres (21,722 ft) above sea level.
Nevado de Longaví is a volcano in the Andes of central Chile. The 3,242 m (10,636 ft) high volcano lies in the Linares Province, which is part of the Maule Region. It features a summit crater and several parasitic vents. The volcano is constructed principally from lava flows. Two collapses of the edifice have carved collapse scars into the volcano, one on the eastern slope known as Lomas Limpias and another on the southwestern slope known as Los Bueye. The volcano features a glacier and the Achibueno and Blanco rivers originate on the mountain.
Quetrupillán is a stratovolcano located in the La Araucanía Region of Chile. It is situated between Villarrica and Lanín volcanoes, within Villarrica National Park. Geologically, Quetrupillán is located in a tectonic basement block between the main traces of Liquiñe-Ofqui Fault and Reigolil-Pirihueico Fault.
Tacora is a stratovolcano located in the Andes of the Arica y Parinacota Region of Chile. Bordering Peru, it is the northernmost volcano of Chile. It is part of the Central Volcanic Zone in Chile, one of the four volcanic belts of the Andes. The Central Volcanic Zone has several of the highest volcanoes in the world. Tacora itself is a stratovolcano with a caldera and a crater. The youngest radiometric age is 50,000 years ago and it is heavily eroded by glacial activity.
Nevado Tres Cruces is a massif of volcanic origin in the Andes Mountains on the border of Argentina and Chile. It has two main summits, Tres Cruces Sur at 6,748 metres (22,139 ft) and Tres Cruces Centro at 6,629 m (21,749 ft) and a third more minor summit, Tres Cruces Norte 6,206 m (20,361 ft). Tres Cruces Sur is the sixth highest mountain in the Andes. The area was first surveyed in 1883 by Francisco San Román and the Nevado Tres Cruces National Park was established in 1994.
Paniri is a stratovolcano located in El Loa Province, Antofagasta Region, Chile, and near the border with Bolivia. To its northwest lie the twin volcanoes San Pedro and San Pablo, and to its southeast lies Cerro del León, from which it is separated by the huge Chao lava dome.
San Pedro is a Holocene composite volcano in northern Chile and one of the tallest active volcanoes in the world. Part of the Chilean Andes' volcanic segment, it is part of the Central Volcanic Zone of the Andes, one of the four tracts of the Andean Volcanic Belt. This region of volcanism includes the world's two highest volcanoes Ojos del Salado and Llullaillaco. San Pedro, like other Andean volcanoes, was formed by the subduction of the Nazca Plate beneath the South America Plate. It has a neighbouring volcano, San Pablo, and is itself formed by two separate edifices usually known as the Old Cone and the Young Cone. These edifices are formed by rocks ranging from basaltic andesite over andesite to dacite and are emplaced on a basement formed by Miocene volcanic rocks.
Los Patos is a mountain in the Andes mountain range of South America. The peak is located on the international border of the Catamarca Province of Argentina and the Atacama Region of Chile. It has a summit elevation of 6,239 metres (20,469 ft).
Jotabeche is a Miocene-Pliocene caldera in the Atacama Region of Chile. It is part of the volcanic Andes, more specifically of the extreme southern end of the Central Volcanic Zone (CVZ). This sector of the Andean Volcanic Belt contains about 44 volcanic centres and numerous more minor volcanic systems, as well as some caldera and ignimbrite systems. Jotabeche is located in a now inactive segment of the CVZ, the Maricunga Belt.
Leon Muerto is a 4,799 metres (15,745 ft) high volcano in Chile.
Lastarria is a volcano that lies on the border between Chile and Argentina. It is part of the Central Volcanic Zone, one of the four segments of the volcanic arc of the Andes. Several volcanoes are located in this chain of volcanoes, which is formed by subduction of the Nazca Plate beneath the South American Plate.
Ojos de Maricunga is a volcano in the Maricunga Belt of Chile, in the Cordillera Domeyko(Muñoz 1894, p. 51).
Pastillitos is a volcano in the Central Andes of Chile.
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.
"San Francisco". Global Volcanism Program . Smithsonian Institution.
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.
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.
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