Guallatiri

Guallatiri is a high volcano in Chile. It is located southwest of the Nevados de Quimsachata volcanic group and is sometimes considered to be part of that group. It is a stratovolcano with numerous fumaroles around the summit. The summit may be composed of either a lava dome or a pyroclastic cone, 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.
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 elevation. Guallatiri, along with several other volcanoes, is part of Lauca National Park.
Geography.
Guallatiri is located in the Putre commune of Parinacota province in the Arica y Parinacota Region of Chile. The nearest populated centers are Guallatire, Ancuta and Chiriguaya; other nearby communities include Ancuta, Chachacomani, Chiriguaya, Jancoaque and Uncaliri. The city of Arica lies west of the volcano. The name of the volcano comes from Aymara , meaning "place of the ", with meaning Andean goose. The volcano is also known as Huallatiri, Huallatire, Guallatire and Punata.
The volcano is located in the Lauca National Park, along with the two higher Pomerape and Parinacota volcanoes; the volcanoes Parinacota, Quisiquisini, Guallatiri and Poquentica form the eastern limit of the Lauca basin. Sometimes Guallatiri is considered to be part of the Nevados de Quimsachata volcanic chain, a long chain of volcanoes.
Other volcanoes with historical phreatic-phreatomagmatic activity in northern Chile include Irruputuncu, Isluga, Lascar and San Pedro. Further, fumarolic activity has been reported at Alitar, Lastarria, Olca, Ollague, Putana and Tacora.
Geology.
Guallatiri is a high complex volcano formed mainly by lava flows but also featuring dacitic or andesitic lava domes, such as Domo Tinto on the southern flank. The volcano is wide and rises about over the surrounding terrain. A volume of has been estimated. The volcano's foot covers a surface of about . The summit is formed by a pyroclastic cone; alternative interpretations see it as a lava dome or a hydrothermally altered, scree-covered lava plug. The vent lies south of the summit and the summit crater is breached westwards and northwards.
Lava flows radiate from the summit and lava domes dot its flanks. Some lava flows are up to long and high and thick lava flows are particularly noticeable on the western and northern slope of the volcano. "Breadcrust" lava bombs are found on the northern flanks, probably carried there by glaciers. Other eruption products include ash flows and tephra layers. The former are particularly developed on the south-southwest flank and the tephras particularly on the southern-eastern flanks.
Guallatiri is underpinned by the rocks of the Lauca Formation, which has an age of 10–0.5 million years. An older basement domain known as the Lupica Formation is exposed north, west and south of the volcano and contains sediments and volcanic rocks. It is of Oligocene-Miocene age. Like other volcanoes in the area, it formed on top of the Chilean Altiplano.
Guallatiri may have formed during the Pliocene, with a second stage of volcanic activity recommencing during the Pleistocene; the volcano started forming about 710,000 years ago. Two stages of volcanic activity in the Pleistocene-Holocene have been identified, although a three-stage chronology of volcanic activity has been proposed as well; this proposal envisages two earlier lavic stages and a third stage characterized by the emission of pyroclastics and lava domes. Volcanic activity in the Quimsachata volcanic chain migrated south from the now deeply eroded Acotango and Humarata volcano to the more recent Capurata and Guallatiri volcanoes. There is evidence indicating that lava flows forming Stage I of volcanic activity were erupted during the middle Pleistocene and the lava domes forming Stage II were erupted in the Pleistocene-Holocene. The lava bombs on the northern flank suggest that eruptions which produced small amounts of rocks occurred in recent times.
Glaciation and hydrology.
Guallatiri has glaciers, including one on the summit and an ice cap above elevation. It is the most southern volcano in the Central Andes with an ice cap as south of Guallatiri tropical summer precipitation is insufficient to support glaciation; only south of 27° does winter precipitation become sufficient to support glaciers again. The glacier area shrunk at a rate of 2.69% per year between 1987 and 2016. Fumaroles have melted holes in the glaciers. Thin moraines are preserved on the flanks at altitudes of and in the summit area.
These glaciers drain towards the Chungara river. A number of streams and dry valleys originate on Guallatiri. Parts of the western and southern flank drain into the Rio Lauca. The Patulas and Caullatiri rivers descend the southwestern flank and the Chirigualla and Captalia rivers the northwestern one.
Petrology.
Guallatiri has erupted andesite, dacite and rhyolite, with dacite dominating. Pyroxene andesites are found up to of altitude. Analysis of lava at Domo Tinto lava dome has indicated that phenocrysts include amphibole, biotite, pyroxene and some apatite. Mafic inclusions have also been found in Domo Tinto rocks. The Domo Tinto eruption may have been triggered by the injection of basaltic andesite into two magma chambers containing crystalline andesite. Native deposits of sulfur are also found and sometimes form flows similar to but smaller than the sulfur flows at Lastarria. Sulfur is the most common mineral in fumarolic deposits; but arsenic, boron, calcium and silicon are also found. Such fumarolic deposits at Guallatiri and the other Andean volcano Lastarria aside from pure sulfur also consist of anhydrite, auripigment, baryte, burkeite, cristobalite, galena, gypsum, magnetite, pyrite, quartz and sassolite.
Domo Tinto rocks have been analyzed for isotope and chemical composition studies. They are potassium-rich calc-alkaline rocks as is typical for Andean volcanism in this area. On the basis of petrology, magma temperatures of the Tinto rocks have been estimated at for the andesitic component and for the basaltic andesite component. SiO2 contents range from 58 to 75%, with dacites having a content of 63–70%.
Eruptive activity.
Solfataric activity is ongoing. In 1985 and 1987 yellow (sulfur-bearing) steam clouds were reported, reaching heights of above the summit. The fumaroles cluster in two places, in the crater and on the southern flank where they reach over down. They have forms like cones and jets. The fumaroles are reported to make "jet"-like noises and temperatures range from - ASTER imaging has indicated temperature anomalies of up to 8 kelvins. Water vapour and carbon dioxide making up the bulk of the gases, other components are hydrogen chloride, hydrogen fluoride, hydrogen sulfide, methane and sulfur dioxide. The volcano produces about of sulfur dioxide. Most of the fumarolic gases originate in deep magma, but interactions with country rock and shallow aquifers do take place. Bubbling pools occur in the Chirigualla geothermal area northwest of the summit. Cold springs around the volcano also show volcanic influence in the form of an enrichment with sulfate and carbonate.
Likewise, the volcano features ongoing seismic activity, including about two earthquakes per day and three seismic swarms in 2011–2012. Another earthquake swarm was associated with the 2001 Peru earthquake. No deformation of the edifice has been observed, however.
The lava dome Domo Tinto was K-Ar dated at 5,000 ± 3000 BP. Its eruption was probably a relatively tranquil effusive eruption. Present day volcanic activity is generally poorly documented, with minor phreatic eruptions recorded. Ash eruptions are reported in the first half of the 19th century. In 1913 and 1959, glow was observed in the summit crater, and a phreatic eruption was reported in 1960. Activity is also reported for 1779, 1802, 1826–1831, 1850, 1859, 1864, 1864, 1870, 1902, 1904, 1908, 1912 and 1959. Guallatiri is the second-most active volcano in northern Chile after Lascar. In 2015 volcano alert levels on Guallatiri was temporarily raised due to deformation of the edifice and changes in the seismic activity.
Threats and preparedness.
The Chilean National Geology and Mining Service keeps a record of regular reports of the activity status of Guallatiri, which is considered to be Chile's 27th most dangerous volcano. A hazard map exists of Guallatiri with three areas of different risk. The red zone occupies the areas interested by late activity of the volcano and river valleys, in total most of the upper parts of the volcano. The orange and yellow zones are areas threatened in the case of medium-large and large scale eruptive activity, respectively.
Ash falls, flank eruptions, lahars and pyroclastic flows are hazards associated with Guallatiri. The town of Guallatiri on its southern flank is especially threatened - pyroclastic flow deposits have been found next to the town - as are the southern and eastern flanks in general. Explosive activity with eruption columns of height may result in ashfall in Arica and Putre depending on the season. There are villages with hundreds of people, including small villages in western Bolivia that may be impacted by Guallatiri tephra. In addition to volcanic hazards, Guallatiri is a regionally important arsenic source; arsenic is a common pollutant in Chilean waters.
Religious and archeological importance.
Unlike on several other Andean summits, no Inka archeological sites are visible on Guallatiri, perhaps discouraged by the persistent volcanic activity. Nevertheless, the mountain was considered an "apu" by the surrounding populace. It is said that townsfolk living in the town of Guallatire worshipped the mountain from Capurata, a nearby mountain. Even today, churches in Ancuta and Guallatire point towards the volcano.