Aracar is a large conical stratovolcano in northwestern Argentina, just east of the Chilean border. It has a main summit crater about Template:Convert in diameter and sometimes contains crater lakes and a secondary crater. The volcano has formed, starting during the Pliocene, on top of a lava platform and an older basement. Constructed on a base with an altitude of Template:Convert, it covers a surface area of Template:Convert and has a volume of Template:Convert. The only observed volcanic activity was a possible steam or ash plume on March 28, 1993, seen from the village of Tolar Grande about Template:Convert southeast of the volcano, but with no evidence of deformation of the volcano from satellite observations. Inca archeological sites are found on the volcano.
GeologyEdit
Aracar is located in the Salta province, north of the Salar de Taca Taca and Arizaro and east of the Salar de Incahuasi and the Sierra de Taca Taca,<ref name="Ceruti" /><ref name="Maisonnave1997" /> close to the Chilean border.<ref name="KoukharskyEtcheverria1997" /> Volcanoes in the territory rise above the endorheic sinks and landscape.<ref name="Ceruti" /> Cerro Arizaro (9.0 ± 1.3 mya) is another volcano southeast of Aracar.<ref name="KoukharskyEtcheverria1997" />
The basement consists of Paleozoic granites.<ref name="Maisonnave1997" /> The Laguna de Aracar Formation north of Aracar was formed by Gondwana volcanism and has been dated by K-Ar methods to be 266 ± 28 Ma old; it is associated with the Llullaillaco Unit.<ref name="PonaZappettini2014" /> Tertiary sedimentary rocks in the east and arenites in the south form the rest of the basement. The volcano's height over the surrounding terrain is between Template:Convert from north to south.<ref name="KoukharskyEtcheverria1997" />
Aracar is a polygenetic volcanic cone with a diameter of Template:Convert<ref name="Maisonnave1997" /> and a rectangular basis of Template:Convert,<ref name="KoukharskyEtcheverria1997" /> covering a surface area of Template:Convert.<ref name="KaratsonTelbisz2012" /> Four lava domes extend southeast from the volcano.<ref name="KoukharskyEtcheverria1997" /> Grey basaltic lava flows descend from its summit, forming a gentle western flank and much steeper eastern, northern, and southern flanks.<ref name="Ceruti" /> West of the main summit, a Template:Convert wide and several hundred meters deep crater forms Aracar's main crater. Snowmelt occasionally forms small ephemeral lakes in the main crater. A Template:Convert shallow Template:Convert deep secondary crater is surmounted by a flat semilunar Template:Convert wide surface.<ref name="Ceruti" /><ref name="GVP" /> Small southbound andesitic lava flows are associated with the main crater.<ref name="KoukharskyEtcheverria1997" /> There are traces of a sector collapse.<ref name="BustosNorini2024" /> Some deep gorges cut into the volcano,<ref name="GVP" /> and erosion has removed Template:Convert of rock.<ref name="KaratsonTelbisz2012" /> Moraines, mainly occurring on the volcano's eastern side, descend to Template:Convert.<ref name="Heine2019" />
A lava field is found beneath the Aracar volcano. It is constructed by lava flows that range in composition from basaltic andesite bordering on trachyandesite over dacite and smaller flows of partially silicic magma. Basal lava flows are heavily eroded and reach Template:Convert in length and width in the south, decreasing from Template:Convert to Template:Convert. They have cancelled out the prior landscape.<ref name="Maisonnave1997" /> These lower lava flows reach the Salar de Taca Taca and extend south-southeast. The main andesitic cone is Template:Convert high and Template:Convert wide, forming on top of older dacitic lava flows. The dacite flows which form the edifice's bulk are covered with debris and have flow fronts Template:Convert high. The lava field formed over a north-south slope.<ref name="KoukharskyEtcheverria1997" />
Lavas have gray-black porphyric and in some places, vesicular textures. Andesine-labradorite plagioclase and pyroxene phenocrysts are found in the lavas, which have a fine-grained groundmass. Apatite, augite, and opaque mineral inclusions are also seen. Some lava flows display very small-scale flow bands with feldspat and plagioclase inclusions. Xenoliths containing quartz and gabbro nodules also play a part in the rock composition. The overall rock composition is calc-alkaline, similar to other magmas in the Central Volcanic Zone, with some intraplate and crustal components, with the magmas forming in an open magma chamber.<ref name="Maisonnave1997" /> Later magmas may have been influenced by the entry of basic magmas from the depth. The total volume of the edifice is about Template:Convert.<ref name="KoukharskyEtcheverria1997" />
The volcanic history of Aracar is poorly understood. The bottom lava flows have ages of 3.4 ± 1.2 to 2.6 ± 0.4 mya,<ref name="Maisonnave1997" /> but an age of 100,000 years has also been given.<ref name="Heine2019" /> Presumably, at first, fluid basaltic lavas were erupted. Subsequently, dacite lavas erupted, accompanied by the formation of a strong slope in the edifice and hydrothermal activity at a northwestern lava dome. Finally, the central crater and andesite lava flows were erupted.<ref name="KoukharskyEtcheverria1997" /> Beneath Template:Convert altitude, lava flows are well conserved. No historical activity is recorded but in March 1993, inhabitants of Tolar Grande Template:Convert southeast of Aracar observed a high ash or steam column rising from Aracar, which may be either an eruption or the result of landslides.<ref name="GVP" /> Satellite images did not detect edifice deformation during this episode, probably due to aliasing.<ref name="FourierPritchard2010" /> Aracar is considered Argentina's 17th most dangerous volcano out of 38.<ref name="GarciaBadi2021" />
History and human interactionEdit
The mountain was climbed in 1958 by European climbers, including Mathias Rebitsch, who found an archeological site in the summit area. Minefield are present on the northeastern flanks of Aracar, making exploration from that side impossible. A major Inca archeological site is found in Aracar. Two separate places exist on the summit and secondary crater. The summit place is formed by a stone circle and low stone walls which are placed just above the slopes down into the main crater. A terrace-shaped stone structure forms the secondary crater, which is placed on its slopes. A smaller terrace is located on its northeastern side. Timber and wood are found around the stone structures. All these sites have no more than Template:Convert dimensions. These structures may be sanctuary sites that could be accessed by a bystanding public during ceremonies, with the sites themselves located within wind protected areas.<ref name="Ceruti" />
NotesEdit
See alsoEdit
ReferencesEdit
External linksEdit
- "Cerro Aracar, Argentina" on Peakbagger
- Template:Cite book (in Spanish; also includes volcanoes of Argentina)