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 but a large prehistorical eruption took place 2,600 years ago. 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 that has shrunk and fragmented during the course of the 20th-21st century. Guallatiri, along with several other volcanoes, is part of Lauca National Park and is monitored by SERNAGEOMIN.
Name and ascents
The term means "abundance of the Andean goose" in Aymara and refers to its frequent occurrence in the area. Other names are Punata which is also Aymara, Huallatiri and Huallatire. It was first climbed by the German-Bolivian geologist in 1926. The volcano is considered to be an easy ascent but toxic gases constitute a hazard in the summit region.
Geography and geomorphology
The volcano lies in the Putre municipality in the Arica and Parinacota Region. It is located south of Lake Chungara
and west of Cerro Capurata. The latter is part of the Nevados de Quimsachata volcano chain which also includes Humurata and Acotango; sometimes Guallatiri is considered to be part of the Nevados de Quimsachata. Guallatiri is part of the larger Western Cordillera which is 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; it features a cemetery, a 17th-century church and a refuge of the National Forest Corporation. Other 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 Arica lies on the Pacific Ocean. Economic activity in the area include the Tambo Quemado border crossing, agriculture, animal husbandry as well as tourism and mountaineering, including ascents to the summit of Guallatiri. The frontier between Bolivia and Chile runs along the Nevados de Quimsachata northeast of Guallatiri and is not far from the volcano. The volcano is remote and thus poorly known.
The volcano
Guallatiri is , or high. It is a composite volcano or stratovolcano with a symmetric cone surmounted by a lava dome or lava complex and a vent just south of it. The summit area has also been interpreted as an eroded volcanic plug or as a lava dome.
Lava domes, lava flows, tephra and volcanic ash make up the volcano. Guallatiri rises about above the surrounding terrain and covers a surface of about ; the total volume is about . Thick lava flows emanate in all directions but are primarily noted on the northern and western flanks and reach lengths of . The lava flows have a lobate appearance even when they are heavily eroded, and displays levees, ogives, polygonal cracks and blocky surfaces. Older flows have been eroded into hills. They reach thicknesses of . Fans of block-and-ash flows occur 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 latter 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. These domes form a northwest–southeast line and are apart. 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 Chungara and the Rio Lauca.
Ice
Above - elevation the volcano is covered with ice. , a small ice cap on Guallatiri covered an area of with of ice. Ice area has been retreating at a rate of , leading to the breakup of the ice cap in several separate ice bodies. 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 . Unlike the global last glacial maximum which peaked between 21,000 and 19,000 years ago, in the area of Guallatiri glaciers reached their maximum extent between 13,500 and 8,900 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. Some glaciers were still present during the Holocene, as the Domo Tinto lava dome bears traces of glacial erosion and is partially covered by moraines.
Volcanic units overlie glacial deposits, or inversely glacial deposits such as various types of moraines overlie older volcanic rocks. 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 America Plate at a rate of about . The subduction process is responsible for the volcanism of the Northern Volcanic Zone (NVZ), Central Volcanic Zone (CVZ) and Southern Volcanic Zone (SVZ) 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 volcanoes which are potentially active or active, 33 of which are located within Chile. The most active of these 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 glacially overprinted. The basement consists of Archean to Precambrian-Paleozoic rocks. There is evidence that the terrain was tectonically active during the Quaternary.
Composition
The composition of volcanic rocks ranges from andesite 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. The occurrence of obsidian has been reported. 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 are reported from its southern flank, and according to the first Panamerican Congress on Mine Engineering and Geology, in 1942 the volcano featured about 800,000 tonnes sulfur ore with a grade of about 55% sulfur. The volcano may be an important source of arsenic pollution in the region.
Flora, fauna and climate
The volcano is inside the Lauca National Park and the wetlands - bofedales - 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 features a tundra climate. Most precipitation falls during the summer months and amounts to about . Moisture mainly originates in the Atlantic Ocean and the Amazon and arrives on the Altiplano mainly during the summer months, 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.
Eruptive history
Volcanic activity at Guallatiri commenced about 710,000 or 262,000-130,000 years ago and the volcano subsequently grew during the Pleistocene and Holocene. The older Humurata and Acotango volcanoes are heavily eroded while Capurata is better preserved. Total magma supply at Guallatiri amounts to , less than at Parinacota but higher than Lascar.
During an initial stage, "Guallatiri I" grew in the form of andesitic and dacitic lava flows as well as heavily eroded pyroclastic deposits, which crop out around the volcano. Then the dacitic "Guallatiri II" developed in close proximity to the central vent; unlike "Guallatiri I" units it has not been eroded by glaciation and flows preserve flow structures. The central sector of the volcano is mainly of Holocene age while the peripheral parts date to the Pleistocene. Later research subdivided the growth of the volcano into seven separate stages, of which 1-4 crop out mainly at the periphery of the volcano and 5-6 in its central sector. All these units were erupted by the central vent of Guallatiri. Some lava flows are well preserved, others have been glaciated.
Evidence indicates that large eruptions similar to the one of Lascar in 1993 may have occurred at Guallatiri. The largest Holocene event at the volcano was a Plinian or sub-Plinian eruption that deposited tephra and pumice southwest of the volcano, reaching thicknesses of at distance, approximately 2,600 years ago. Non-explosive eruptions also took place, such as the Domo Tinto eruption 5,000±3,000 years ago. The eruption emplaced lobes of lava over a flat surface.
Pyroclastic flow deposits extend to distance from Guallatiri. Radiocarbon dating has yielded ages ranging between 6,255±41-140±30 years before present. These flows are unrelated to the lava domes, which show no evidence of collapses that could have formed pyroclastic flows. Lahar deposits are found on the southern flanks of the volcano and do not exceed thickness. They form when volcanic material interacts with water, produced either by the melting of ice or through intense rainfall. Holocene lahar deposits have been found in river valleys.
Historical and seismic activity
Guallatiri is after Lascar the second-most active volcano in northern Chile, with numerous small explosive eruptions since the 19th century which produced thin tephra layers. The eruption history of Guallatiri is poorly known and historical eruptions are poorly documented. Eruptions with a volcanic explosivity index of 2 took place in 1825 ± 25, 1913, July 1959 and December 1960. A further uncertain eruption took place in 1908 and additional poorly documented eruptions are reported from 1862, 1864, 1870, 1902, 1904 and 1987. Radiocarbon dating has yielded evidence of at least one eruption during the past 200 years.
Increased steam emission was observed in December 1985 and initially attributed to Acotango volcano, before it was linked to Guallatiri; it may have been an eruption of the latter. In May 2015 SERNAGEOMIN raised the volcano alert level when seismic activity increased and a high plume appeared over the volcano, only to lower it again in July when activity decreased.
Shallow earthquakes and sporadic seismic swarms are recorded at Guallatiri; one such swarm was induced by the 2001 Peru earthquake. Satellite imaging has not shown any evidence of ongoing deformation of the volcanic edifice.
Fumarolic activity
Guallatiri features fumaroles and solfataras, and mud pools have been reported as well. There are two main areas, one on the western flank below the summit and another on the south-southwestern flank. Fumaroles form alignments, and a long fracture lies in the southern area. Some sources also identify a third area on the upper western flank. The vents of individual fumaroles sometimes form cones that reach heights of and widths of , and there are small explosion craters with widths of in the summit region. Liquid sulfur has formed pahoehoe-like flows which reach lengths of . Other minerals deposited by the fumaroles are sulfates such as baryte and sulfides, including cinnabar, antimony sulfides and arsenic sulfides.
The temperatures of the fumaroles range between . Guallatiri produces gases consisting of carbon dioxide and water vapour, with hydrogen chloride, hydrogen fluoride, hydrogen sulfide, methane and sulfur dioxide as additional components. They appear to originate from a hydrothermal system where intense rock-gas interaction takes place. The water originates in part from the magma and in part from precipitation. Different degrees of interaction with precipitation water may explain why the south-southwestern flank fumarole gases have a different composition than these released in the summit region. The fumarolic activity has produced intense hydrothermal alteration of Guallatiri's rocks east-northeast of the summit and at a lower elevation northwest of it.
Fumarole plume
The fumarole clouds emanating mainly from the summit fumarole are visible from more than distance and also from infrared satellite images. The fumarole cloud influences the perception of volcanic activity by the local population.
Puffing behaviour was noted in 1996 and emissions every half-hour in November 1987, which gave rise to yellow-white plumes up to high. Jet-like noises are heard from the fumaroles. According to a report by mountaineers in 1966, fire emanated from the fumarole vents.
Hazards and monitoring
Future eruptions may consist of the emission of lava domes or lava flows, preceded by explosive activity that could impact the settlements of Ancuta and Guallatiri on the southern and western flanks. Large explosive eruptions could deposit pyroclastics over hundreds of kilometres, with the direction depending on the wind direction at the time of the eruption. Lahars would mainly impact the western and southwestern sectors of the volcano, as the snow cover is concentrated there. Lava flows would also primarily impact this sector of the volcano. Pyroclastic flows may impact areas within from Guallatiri, including the settlements Ancuta and Guallatiri. Apart from Ancuta and Guallatiri in Chile, the volcano may threaten towns in Bolivia and ash clouds from Guallatiri could impact airports in the wider region as far as Paraguay. The vulnerability of the local population reflects both the widespread poverty and marginalization on the one hand, and the low population density on the other hand. Significant eruptions are expected to reoccur on century timescales.
Guallatiri is ranked second in the Chilean scale of dangerous volcanoes and the 30th most dangerous in the country. In 2013, the Southern Andean Volcano Observatory began to monitor the volcano with video surveillance, measurements of seismic activity and deformations of the volcanic edifice. Volcano hazard maps have been published.
Mythology and religious importance
In the oral tradition of Chipaya, cold winds called blow from the Pacific Ocean to the Altiplano and towards Guallatiri. The volcano there is linked with hell. They believed that the waters of the Lauca River originate on Guallatiri and directly from hell.
On the contrary, Guallatiri was also considered to be an apu, a protective mountain spirit. The mountain was and still is worshipped by local inhabitants, and the church in the town of Guallatiri is constructed in a way that it points to the volcano. There are no known archeological sites on the summit of Guallatiri, unlike several other mountains in the region. Either the continuous ice cover or the constant volcanic activity may be the reason.
See also
List of volcanoes in Bolivia
List of volcanoes in Chile
Kuntur Ikiña
Notes
References
Sources
Active volcanoes
Volcanoes of Arica y Parinacota Region
Stratovolcanoes of Chile
Mountains of Chile
Six-thousanders of the Andes
Pleistocene stratovolcanoes
Holocene stratovolcanoes