Hualca Hualca (possibly from Aymara and Quechua wallqa collar) is an extinct volcano in Arequipa Region in the Andes of Peru. It has a height of 6025 m. It is located at the Peruvian province of Caylloma.

Geography and geology

Hualca Hualca is part of the Central Volcanic Zone of the Andes, a volcanic belt which occurs where the Nazca Plate subducts beneath the South America Plate. Volcanoes in Peru that are part of the Central Volcanic Zone include Ampato, Casiri, Chachani, Coropuna, El Misti, Huaynaputina, Pichu Pichu, Sabancaya, Sara Sara, Solimana, Ticsani, Tutupaca, Ubinas, Yucamane and numerous calderas and monogenetic volcanoes. North of Hualca Hualca lies the Colca Canyon, a geopark and important tourism destination. Outcrops of the Paleozoic and Mesozoic basement occur there. Hualca Hualca forms a volcanic complex with the two southerly volcanoes Sabancaya and Ampato. It is older (Pliocene-Pleistocene) and more heavily eroded than these two volcanoes; they are all constructed on Neogene ignimbrites, one of which was dated to 2.2 ± 1.5 million years ago, and the volcanoes cover a surface area of 620 km2. Hualca Hualca produced two formations of lavas, andesites during the Pliocene and dacite and trachyandesite during the Pleistocene. The volcano has erupted andesitic lava flows; one series of such flows exceeds a thickness of 0.5 km. Volcanic rocks of Hualca Hualca contain phenocrysts of biotite, clinopyroxene, hornblende, orthopyroxene, plagioclase and sphene. The magma probably originated through mixing processes, similar to Sabancaya, and from mantle magmas that underwent metasomatism and assimilation of crustal materials.

Sector collapses

The northern flank of Hualca Hualca underwent two large sector collapses on the northern side, opening up a 14 km wide collapse amphitheatre that cuts into older volcanic formations. No deposits from the main collapse are known. A new edifice formed within the collapse scar between the two collapses. The second, much smaller, collapse formed a lake in the Colca valley which later catastrophically failed. This lake has left lacustrine deposits in the Colca Valley. Eruptions within the collapse amphitheatre built up several lava domes and lava flow fields, including Nevado de Puye, Mirador Cruz del Condor and Cerro Ahuashune and the present-day Hualca Hualca. Lava flows formed volcanic dams in the Colca Valley. Lava domes and pyroclastic flows also originated within the collapse scar. Earthquakes and hydrothermal alteration probably caused the onset of the collapse event.

Climate and glaciation

Temperatures are stable year-round. Precipitation reaches 0.8 - 1 m and occurs mainly during summer, when the intertropical convergence zone migrates south. The volcano was glaciated during the last ice age, between 18,000 and 11,500 years ago. This glaciation has left moraines, rock glaciers and roches moutonees. There are three sets of moraines on all sides of Hualca Hualca. The glaciers on Hualca Hualca have retreated since then, one was reported to have disappeared by 2000. Snowmelt and runoff from Hualca Hualca are sources of water for the Colca Canyon, supporting irrigated agriculture there; the mountain is worshipped by local inhabitants, who according to reports in 1586 believed that their ancestors come from it.

Recent activity

Volcanic activity began 1.6 million years ago in the Pliocene and consisted of eight separate stages. The large collapse took place more than 600,000 years ago, but activity continued until about 164,000 years ago. Hualca Hualca is considered to be an extinct volcano; however at least seven vents on its southwestern flank show evidence of Holocene activity. Satellite images in the early 21st century found that Hualca Hualca is inflating from a depth of 13 - 11 km at a rate of 2 cm/year. This deformation may be associated with the neighbouring volcano Sabancaya which is active; magma chambers of volcanoes are sometimes distant from the actual volcano as was the case with Katmai. The inflation ceased after 1997. At Pinchollo in the collapse scar three geysers were active in the past; one is still active and is named Infiernillo. The activity of the hydrothermal system at Hualca Hualca increased beginning in 2016, an increase linked to eruptions of Sabancaya and earthquakes.

Climbing and first ascent

Hualca Hualca can be climbed in a few days from the village of Pinchollo by the north side. It was first climbed by Richard R. Culbert from Canada on 6 April 1966. Evidence of pre-Columbian ascents possibly from Incans, such as coca leaves and a puma skin, was found near the summit. Some reports show Piero Ghiglione and P. Chavez reaching the summit on 23 August 1950, however this was a secondary summit.