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Cerro Chao is a lava flow complex associated with the Cerro del León volcano in the Andes. It is the largest known Quaternary silicic volcano body and part of the most recent phase of activity in the Altiplano–Puna volcanic complex. Cerro Chao formed over the course of three eruptions preceded by a pyroclastic stage. Three large lobate lava flows erupted in the col between two volcanoes and advanced for a maximum length of . The eruption that originated the lava flows probably lasted more than one hundred years and occurred before the Holocene. == Geology == Cerro Chao,〔 also named Cerros de Chao, Chao lava or Chao volcano,〔 is located in the volcanic front of the Central Volcanic Zone of the Andes, between the older Paniri and Cerro del León andesitic stratovolcanoes. The Central Volcanic Zone is one of the three volcanic belts in the Andes.〔 The region is dominated by the Altiplano–Puna volcanic complex, where during the Miocene–Pleistocene epoch large ignimbrite eruptions occurred. In the present day, volcanism is of andesitic composition forming volcanic cones. Activity is controlled by fault zones, some of these linked to the Pastos Grandes caldera. Neighbouring volcanoes with similar characteristics to Cerro Chao include Cerro Chanca/Pabellon, Cerro Chascon–Runtu Jarita complex, Cerro Chillahuita and La Torta.〔 Cerro Chao lies within a northwest-running belt of volcanoes, some of them over high, of which San Pedro has historical activity.〔 Cerro Chao is the largest such silicic lava flow known.〔 The eruption is intriguing both in terms of the viscosity of the erupted lavas and its effusive nature. Conventional lava flows increase in viscosity with increasing crystal content; however Chao lava flows were erupted with similar viscosities and yield strengths as silicic domes. The formation of a lava flow instead of a lava dome may have been influenced by the formation of a carapace on the flow and the steep slopes the flows initially formed on; the late Chao III flow formed on the very gentle slope left by the previous Chao I and Chao II flows and shows some lava dome characteristics.〔 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cerro Chao」の詳細全文を読む スポンサード リンク
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