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Concept
Hualca Hualca
Résumé
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 . It is located at the Peruvian province of Caylloma.
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 and Yucamane.
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. The volcano has erupted andesitic lava flows; one series of such flows exceeds a thickness of . 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.
The northern flank of Hualca Hualca underwent a large sector collapse between 1.36 and 0.61 million years ago, opening up a collapse amphitheatre and forming 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 generated lava flows which then 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.
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. The glaciers on Hualca Hualca have retreated since then, one was reported to have disappeared by 2000.
Source officielle
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