Volcano in Peru
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 2,100 ± 200 and either 1,100 ± 100 or 700 ± 200 years 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 (LGM) 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, means "plateau", and is a common component of toponyms such as with Coro Coro, Bolivia, though its etymology is unclear. The name may mean , "Puna of Gold", "golden mountain", "cold, snowy" or "cut off at the top". Ernst Wilhelm Middendorf believed it was originally the name of the high plateau around the mountain. The name is also spelled . 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 Cordillera Ampato, 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 stratovolcanoes – including many of the world's highest – and 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 east–west ridge that features four summits that are separated by broad saddles. In addition, there is another summit north of the east–west 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 (mudflows) 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 ranges – the western and the eastern Cordillera – separated 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.
Elevation and size.
Coropuna is the largest and highest volcano in Peru, the highest peak of the Cordillera Ampato and the third-highest mountain in Peru. The highest point of Coropuna is the northwestern dome named Coropuna Casulla, with elevation. Mountaineering sources also cite an elevation of for the El Toro summit, which would make Coropuna the 22nd highest mountain in the Andes.
Estimates on the height of Coropuna have changed over time. In the 19th century, it was one of the candidates for "highest mountain in Peru", with the Mapa del Perú (Map of Peru) of Antonio Raimondi giving an estimated height of ; other candidates were peaks in the Cordillera Blanca. In 1910 it was believed that the volcano was over high and thus the highest mountain in South America, ahead of Aconcagua, although a North American expedition during the preceding year had determined that Coropuna was not the highest, as they only found an elevation of , and Huascaran is higher than this. Varying snow elevations might also lead to varying height estimates.
Coropuna has several summits (up to ten overall according to one count) which exceed elevation, plus a northern summit. Those with individual names are the northwestern Coropuna Casulla at , El Toro, the western Nevado Pallacocha at , the central Coropuna Central II at , Escalera at in the western sector of the volcano, Paiche at in the central sector, and Coropuna Este and Yana Ranra at in the eastern sector.
Ice cap.
Coropuna features the largest ice cap of the tropics. As of 2014 it was wide and long. It is larger than the Quelccaya Ice Cap farther northeast, which was considered to be the largest, but has since shrunk to a size less than Coropuna's. A subsidiary peak named Cerro Cuncaicha, east of Coropuna, has a small ice cap as well. In general, Peruvian glaciers form the bulk of the world's tropical glaciers. The ice cap consists of three ice domes and many glaciers. Perennial snow fields are present on Coropuna, sometimes making it hard to measure the true extent of glaciation or glacier retreat.
On average, the ice cap of Coropuna is about thick, with maximum thicknesses exceeding . In 2003–2004 the ice cap had a volume of about snow water equivalents. Ice cores have been taken from the Coropuna ice cap and from a summit crater; one of these ice cores covers a timespan beginning from 20,000years ago.
Penitentes reaching heights of and seracs (blocks of ice in glaciers delimited by cracks) occur on the glaciers, while debris cover is rare. The ice of Coropuna's ice cap is mostly temperate. Mudflows (lahars) originated from the ice cap and left deposits at the bottom of valleys. A lahar took place on the southeastern flank on 22 December 2016, causing damage to water infrastructure and pastures below the volcano.
Glaciers and periglacial phenomena.
A number of glaciers flow down from the ice cap, their number variously estimated to be 15, 17 and 23. Some glaciers have been named; on the southwestern flank two glaciers