Coropuna
Coropuna is a dormant compound volcano located in the Andes mountains of southeast-central Peru. The upper reaches of Coropuna consist of several perennially snowbound conical summits, lending it the name Nevado Coropuna in Spanish. The complex extends over an area of and its highest summit reaches an altitude of above sea level. This makes the Coropuna complex the third-highest of Peru. Its thick ice cap is the most extensive in Earth's tropical zone, with several outlet glaciers stretching out to lower altitudes. Below an elevation of, there are various vegetation belts which include trees, peat bogs, grasses and also agricultural areas and pastures.
The Coropuna complex consists of several stratovolcanoes. These are composed chiefly of ignimbrites and lava flows on a basement formed by Middle Miocene ignimbrites and lava flows. The Coropuna complex has been active for at least five million years, with the bulk of the current cone having been formed during the Quaternary. Coropuna has had two or three Holocene eruptions and either or ago which generated lava flows, plus an additional eruption which may have taken place some 6,000 years ago. Current activity occurs exclusively in the form of hot springs.
Coropuna is located northwest of the city of Arequipa. People have lived on the slopes of Coropuna for millennia. The mountain was regarded as sacred by the Inca, and several archaeological sites have been discovered there, including the Inca sites of Maucallacta and Acchaymarca. The mountain was considered one of the most important Inca religious sites in their realm; human sacrifices were performed on its slopes, Coropuna forms part of many local legends and the mountain is worshiped to the present day.
The ice cap of Coropuna, which during the Last Glacial Maximum had expanded to over, has been in retreat since at least 1850. Estimates published in 2018 imply that the ice cap will persist until about 2120. The retreat of the Coropuna glaciers threatens the water supply of tens of thousands of people relying upon its watershed, and interaction between volcanic activity and glacial effects has generated mudflows that could be hazardous to surrounding populations. Because of this, the Peruvian geological agency, INGEMMET, monitors Coropuna and has published a hazard map for the volcano.
Name and etymology
In Quechua, puna means "plateau", and coro is a common component of toponyms such as with Coro Coro, Bolivia, its etymology is unclear but may relate to Puquina language coro "round" but may also refer to "world". The name may mean Qoripuna, "Puna of Gold", "golden mountain", "cold, snowy" or "cut off at the top". believed it was originally the name of the high plateau around the mountain. The name is also spelled Qhuru Puna. The mountain is also called Nevado Coropuna; "Nevado" is the Spanish word for "snowy". There is another volcano in the Andahua volcanic field which has the same name, but is completely separate.Geography and geomorphology
Coropuna lies in the Andes of Peru, on the border between the Castilla and Condesuyos Provinces of the Arequipa Department. Towns around the volcano belong to the Chuquibamba, Machaguay, Pampacolca and Viraco Districts. The volcano can be reached on paved roads through the town of Andahua, either from Arequipa or through Aplao from the Pan-American Highway. Roads also pass along the northern and western sides of the volcano.Regional
The Andes stretch along the western coast of South America from Tierra del Fuego northwards to Venezuela, forming the longest mountain chain in the world. More regionally, the volcano is in the, a mountain range which lies at an average of from the Pacific coastline, and contains nearly one hundred glaciers.Coropuna is in the Central Volcanic Zone of the Andes, which contains 44 stratovolcanoesincluding many of the world's highestand several glaciated volcanoes. Besides Coropuna, some of the latter are Sara Sara, Solimana, Mismi, Ampato, Hualca Hualca, Sabancaya, Chachani, Misti, Ubinas, Huaynaputina, Tutupaca, Yucamane and Casiri. Also found nearby are Neogene-age calderas. Sixteen volcanoes in Peru are active or potentially active.
There is no habitation on Coropuna above, but numerous villages dot the lower slopes. Agriculture and animal husbandry are the most common economic activities; there are copper and gold mines as well. The city of Arequipa lies to the southeast.
Local
General outline
Seen from above, Coropuna has a pear-shaped outline and is a eastwest ridge that features four summits that are separated by broad saddles. In addition, there is another summit north of the eastwest trend. A high subsidiary peak named Cerro Cuncaicha lies east of Coropuna; it is an extinct stratovolcano. Coropuna covers a surface area of and its various main summits rise about above the surrounding plateau.The volcano is formed from alternating layers of ignimbrite and lava, and consists of coalesced stratovolcanoes and seven separate coulees. Ice cover makes discerning its structure difficult, but about six separate peaks as well as six not readily recognisable summit craters have been counted. Additional lava domes form a southeastward trending line on the southwestern side of the volcano and dikes crop out close to Lake Pallarcocha. Coropuna overlies the margin of a buried caldera.
The higher elevations of Coropuna consist of an ice cap and glaciated terrain but old lava flows with gentle slopes and blocky lava crop out from underneath the ice. Regions of hydrothermally altered rocks, lava flows, pyroclastic flows and areas covered by volcanic ash occur all around the mountain. Glacial activity has eroded these volcanic rocks, carving valleys into them or removing them altogether. This process created U-shaped valleys such as Buenavista, Cospanja and Tuilaqui on the southern flank, and glacial valleys such as Chaque, Mapa Mayo, Río Blanco, Torcom and Ullulo on the northern slopes. Glacial valleys of Coropuna are up to deep and long.
There are several collapse scarps on the mountain, especially around its central sector. A sector collapse took place on the southwestern flank and formed a landslide deposit as well as a horseshoe-shaped valley that was later filled by glaciers. Also on the southern side, mud-water flow deposits have been found in the Capiza River valley and appear to relate to Coropuna; at least eight such debris flows have been identified. Lahars have reached the Colca River valley. Lahars are dangerous phenomena owing to their high speed and density, causing large scale destruction and fatalities, and can be generated both by volcanic and meteorological processes. Such lahars occurred in 2016 and 2023, causing damage to agricultural land and irrigation infrastructure.
Lakes, rivers and groundwater
Lakes lie on the flanks of the volcano. These include Lake Pallarcocha on the southwestern flank on formerly glaciated terrain, Laguna Pucaylla on Coropuna's northeastern side and Laguna Caracara on the southeastern side. A number of streams and rivers originate on the mountain. Clockwise around Coropuna, these include Quebrada Chauqui-Huayco, Rio Amayani on the northern side, Quebrada Chinchina/Infernillo, Quebrada Jollpa, Quebrada Caspanja with the lake Laguna Caracara, Quebrada Buena Vista, Quebrada Tuallqui, Rio Testane on the southern flank, Rio de Huayllaura on the southwestern flank, Quebrada del Apacheta, Quebrada Sigue Chico and Quebrada Sepulturayoc on the western flank. The Rio Blanco and Rio Amayani eventually form the Rio Arma, while the Rio Capiza discharges water from Coropuna to the Colca River. During the winter dry season, most of these rivers do not carry substantial discharge.The volcano is situated on a drainage divide. Most of Coropuna drains to the Rio Arma west of the volcano, a tributary of the Ocoña River, while to the east, the Colca River is part of the Majes River watershed. An endorheic area that receives meltwater from the volcano also exists northeast from Coropuna, on Pampa Pucaylla where the lake of the same name lies.
Glacial meltwater seldom forms streams. The Quebrada Ullulo on the northern side is the largest such meltwater stream. Glacial input is more significant to groundwater; especially on the northern flank glacial meltwater makes up a large fraction of local river discharge. The andesites of Coropuna and its glacial sediments host aquifers that convey glacial meltwater to springs and rivers. Some aquifers on the eastern side are influenced by sulfur-containing rocks.
Surrounding terrain
Coropuna rises above the surrounding terrain from a base elevation of, and about on the southern side where the Rio Llacllaja has incised the underlying basement almost to the foot of the volcano, forming sharp, amphitheatre-like valleys. In general, many deep valleys cut into the flanks of the volcano and give the mountain an "impressive topographic relief".The region is characterised by high plateaus separated by deep canyons, including some of the world's deepest gorges that reach depths of. Apart from river erosion, giant landslides have affected the Altiplano below Coropuna, such as the Chuquibamba landslide, which took place over the last 120,000years in the form of multiple collapse events within a fault-controlled basin.
Geomorphologically, Coropuna lies at the edge of the Altiplano high plateau on the Western Cordillera mountain range; in the Central Andes this mountain chain is split into two rangesthe western and the eastern Cordilleraseparated by the Altiplano. The Pucuncho Basin and Firura volcano lie north of Coropuna, while Solimana volcano is northwest from Coropuna. Sara Sara is another volcano in the area. A large lava dome lies northwest of Coropuna while Cerro Pumaranra, a eroded volcano, is to the northeast. west-southwest from Coropuna lies the high Antapuna, while the Andahua "Valley of the Volcanoes" is east-northeast of Coropuna.