Guallatiri
Guallatiri is a volcano in Chile with an elevation of. It is located southwest of the Nevados de Quimsachata volcanic group; some sources classify Guallatiri as a member. Guallatiri is a stratovolcano with numerous fumaroles around the summit. The summit may be a lava dome or volcanic plug, while the lower flanks of the volcano are covered by lava flows and lava domes. The volcano's eruptions have produced mostly dacite along with andesite and rhyolite. Past glaciation has left moraines on Guallatiri.
A large eruption took place approximately 2,600 years ago. Guallatiri has been active in historical times with a number of eruptions, the latest in 1960. Fumarolic and seismic activity is ongoing and has resulted in the deposition of sulfur and other minerals on the volcano. The volcano is covered by an ice cap above that has shrunk and fragmented during the course of the 20th and 21st centuries. Guallatiri, along with several other volcanoes, is part of Lauca National Park and is monitored by the Chilean National Geology and Mining Service.
Name and ascents
The term Guallatiri is derived from wallatiri, which means in Aymara, referring to the birds' frequent occurrence in the area. Other names are Punata, Huallatiri, Huallatire and Guallatire. It was first climbed in 1926 by the geologist. The volcano is considered to be easy to ascend but toxic gases constitute a hazard in the summit region.Geography and geomorphology
The volcano lies in the Putre municipality, Arica y Parinacota Region. It is located south of Lake Chungaráand west of Cerro Capurata. The latter is part of the Nevados de Quimsachata volcano chain which includes Umurata, Acotango and Capurata; sometimes Guallatiri is considered to be part of the Nevados de Quimsachata. The older Umurata and Acotango volcanoes are heavily eroded; Capurata is better preserved. Guallatiri is part of the larger Western Cordillera, the western boundary of the Altiplano high plateau.
The small town of Guallatiri is southwest of the volcano and is the settlement closest to it; the town has a 17th-century church and a refuge of the National Forest Corporation. Other nearby towns include Ancuta, Carbonire and Churiguaya. each had a population of less than 25 people. The provincial capital Putre is north of the volcano, and farther west, on the Pacific coast, is Arica. Economic activity in the area includes the Tambo Quemado border crossing, agriculture, animal husbandry, tourism and mountaineering, including ascents to the summit of Guallatiri. There are no known archeological sites on the summit of Guallatiri, unlike several other mountains in the region. Possible reasons are the continuous ice cover and the constant volcanic activity. The frontier between Bolivia and Chile runs along the Nevados de Quimsachata northeast of Guallatiri, not far from the volcano. The volcano is remote and thus poorly known.
The volcano
Guallatiri is or high; claims of even higher elevations appeared in past and some recent publications. It is a composite volcano or stratovolcano with a symmetric cone surmounted by a lava dome, lava complex or volcanic plug and a vent just south of it.Lava domes, lava flows, tephra and volcanic ash make up the mountain. Guallatiri rises about above the surrounding terrain and covers an area of about ; the total volume is about. Thick lava flows emanate in all directions but are primarily noted on the northern and western flanks. The flows reach thicknesses of and lengths of. The lava flows have a lobate appearance even when they are heavily eroded, and display levees, ogives, polygonal cracks and blocky surfaces. Older flows have been eroded into hills. Block-and-ash flows form fans on the southern and southwestern flanks. Tephra deposits are mainly located on the eastern and southern side of Guallatiri. Tuffs and pyroclastic flow deposits occur both in the summit region and in radial valleys that emanate from Guallatiri, although some of the deposits southwest of the volcano have been reinterpreted as being reworked sediments. Apart from volcanic rocks, glacial deposits cover large parts of the volcano, and there are traces of mass failures.
On the southern flank, there are two lava domes named Domo Tinto and Domo Sur; other than these Guallatiri has no lateral vents. Domo Tinto is wide and high while Domo Sur is thick and wide. Domo Tinto has a hummocky surface and resembles a pancake.
There are both cold springs and hot springs on Guallatiri, indicating that groundwater interacts with the magmatic system. One hot spring is located at Chiriguaya on the northwestern foot of Guallatiri, where temperatures of were measured in bubbling pools, and sinter deposition takes place. Several streams run off the mountain; they eventually enter Lake Chungará and the Lauca River.
Ice
Above – elevation the volcano is covered with ice in the form of glaciers., an ice cap on Guallatiri covered an area of and had a volume of. Ice area has been retreating at a rate of , leading to the breakup of the ice cap into several separate ice bodies. According to a 2005 study by Rivera et al., heat emitted by fumaroles may have contributed to the enhanced melting of the ice.Glacial deposits on Guallatiri cover an area of about above elevation, with lateral moraines reaching lengths of and thicknesses of. Glaciers reached their maximum extent between 13,500 and 8,900 years ago. This is unlike the global Last Glacial Maximum, which peaked between 21,000 and 19,000 years ago. This is a consequence of the climate in the region, where glacier extent was more sensitive to increased moisture supply than to decreasing temperatures; presumably the global LGM was too dry to allow glacier formation. Some glaciers were still present during the Holocene, evidenced by Holocene-age Domo Tinto lava dome which bears traces of glacial erosion and is partially covered by moraines.
Volcanic units are found both overlying and underlying glacial deposits such as moraines. Older volcanic rocks bear glacial striations, and volcanic bombs on the lower flanks may have been transported there by glaciers.
Geology
Off the western coast of South America, the Nazca Plate subducts beneath the South American Plate at a rate of about. The subduction process is responsible for the volcanism of the Northern Volcanic Zone, Central Volcanic Zone and Southern Volcanic Zone, and has also driven the formation of the Altiplano during the last 25 million years.The CVZ is a long chain of volcanoes spanning southern Peru, northern Chile, western Bolivia and northwestern Argentina. It contains about 58 active or potentially active volcanoes, 33 of which are located within Chile. The most active CVZ volcano is Lascar, which in 1993 produced the largest historical eruption of northern Chile.
Guallatiri rises above Oligocene to Pliocene age volcanic and sedimentary rocks, which define the Lupica and Lauca Formations. The Lupica Formation is older and consists mainly of volcanic rocks, while the Lauca Formation is formed by volcanic and sedimentary rocks that were deposited within the basin and in part altered by glaciers. Archean to Precambrian-Paleozoic rocks make up the basement. There is evidence that the terrain was tectonically active during the Quaternary.
Composition
The composition of Guallatiri's rocks ranges from andesite over dacite to rhyolite, with dacites being predominant. The summit dome is formed by dacite and most outcrops are trachyandesite and trachydacite. The rocks define a potassium-rich calc-alkaline suite and contain amphibole, apatite, biotite, clinopyroxene, olivine and plagioclase phenocrysts, similar to other volcanoes in the region. A single lava bomb made out of obsidian has been found. Mafic rock enclaves have been observed in Domo Tinto rocks, which indicate that mafic magmas were injected into the magma chamber and mixed with already present magma. Fractional crystallization and magma mixing processes gave rise to Guallatiri's magmas.Fumaroles have deposited minerals such as anhydrite, baryte, cristobalite, gypsum, quartz, sassolite and sulfur. Less common are galena, orpiment and pyrite. Sulfur deposits have yellow, orange or red colours and are sometimes accompanied by arsenic-sulfur compounds that also contain iodine, mercury, selenium and tellurium. Sulfur deposits occur on Guallatiri's southern flank; according to the first Panamerican Congress on Mine Engineering and Geology, in 1942 the volcano had about of sulfur ore with a grade of about 55% sulfur. The volcano may be an important cause of arsenic pollution in the region.
Flora, fauna and climate
The volcano is inside the Lauca National Park and the wetlands in the area of Guallatiri have regional importance. Vegetation there include Arenaria rivularis, Calandrinia compacta, Deyeuxia curvula, Distichlis humilis, Lobelia oligophylla and Oxychloe andina. Animal species include birds such as the Andean flamingo, Andean gull, Andean goose, buff-winged cinclodes, Chilean flamingo, condor, giant coot, James's flamingo, mountain parakeet, Puna ibis, Puna tinamou and torrent duck. Among the mammals are the alpaca, Altiplano chinchilla mouse, Andean swamp rat, lesser grison, llama, mountain degu, Osgood's leaf-eared mouse, short-tailed chinchilla and vicuña. Woodlands formed by the tree Polylepis tarapacana occur on Guallatiri; this tree forms the world's highest woodlands. The upper parts of the mountain are covered with rocks and pioneer vegetation to about elevation.The region has a tundra climate. Most precipitation falls during the summer months, amounting to about per year, averaged between 1997 and 2017. Moisture mainly originates in the Atlantic Ocean and the Amazon, especially during cold events of the El Niño–Southern Oscillation when moisture supply increases. Tree ring chronologies from Polylepis tarapacana trees growing at Guallatiri have been used for climate reconstructions.