page_title: Cerro Azul (Chile volcano)
section_title: Local setting
hierarchical_section_title: Cerro Azul (Chile volcano) / Geography and geology / Local setting
caption_attribution_description: Descabezado Grande and Cerro Azul volcanoes, Chile.
context_page_description: Cerro Azul, sometimes referred to as Quizapu, is an active stratovolcano in the Maule Region of central Chile, immediately south of Descabezado Grande. Part of the South Volcanic Zone of the Andes, its summit is 3,788 meters above sea level, and is capped by a summit crater that is 500 meters wide and opens to the north. Beneath the summit, the volcano features numerous scoria cones and flank vents.
  Cerro Azul is responsible for several of South America's largest recorded eruptions, in 1846 and 1932. In 1846, an effusive eruption formed the vent at the site of present-day Quizapu crater on the northern flank of Cerro Azul and sent lava flowing down the sides of the volcano, creating a lava field 8–9 square kilometres in area. Phreatic and Strombolian volcanism between 1907 and 1932 excavated this crater. In 1932, one of the largest explosive eruptions of the 20th century occurred at Quizapu Crater and sent 9.5 cubic kilometers of ash into the atmosphere. The volcano's most recent eruption was in 1967.
  The South Volcanic Zone has a long history of eruptions and poses a threat to the surrounding region.
context_section_description: Cerro Azul is part of the South Volcanic Zone, which runs through central and western Chile and extends south to Argentina. This range includes at least nine caldera complexes, more than 70 of Chile's stratovolcanoes and volcanic fields that have been active in the Quaternary, and hundreds of minor eruptive centres. The South Volcanic Zone is the most volcanically active region in Chile, and produces around one eruption per year. Its largest historical eruption was at Quizapu Crater, located on the north side of Cerro Azul's summit (see below), and its most active volcanoes are Llaima and Villarrica.
  Cerro Azul, just 7 kilometers (4.3 mi) south of Descabezado Grande volcano, is part of the Descabezado Grande–Cerro Azul eruptive system, a volcanic field that comprises its two large namesake volcanic edifices and several smaller vents, including 12 Holocene calderas. Both volcanoes lie on top of the Casitas Shield, a plateau built of over 100 lava flows that erupted in at least 12 volcanic episodes during the Quaternary period. The upper lava layers are dated at 340,000 years.
  As with the majority of the Andean volcanoes, Cerro Azul is a stratovolcano, meaning that it consists of layers, or strata, of volcanic ash and lava flows. The cone of Cerro Azul has a total volume of about 11 cubic kilometers (3 cu mi), and is a young feature, formed in the Holocene. It is made of agglutinated pyroclasts and some dacite–andesine lavas. The cone has a few volcanic craters; the majority of its eruptions in recorded history have originated from Quizapu Crater on the northern flank of Cerro Azul's cone. Other craters lying on the flanks of the main cone are Caracol ("Snail"), Crater los Quillayes, Crater la Resolana, and Crater sin Nombre ("Nameless Crater"). All of the craters lie between 2,000 and 3,000 meters (6,600 and 9,800 ft) in elevation, except Quizapu, which is 3,292 meters (10,801 ft) up the volcano. The summit of Cerro Azul is crowned by an asymmetric crater about 500 meters (1,640 ft) in diameter. Pleistocene glacial activity is evident in the form of 500 meter (1,640 ft) deep struts in the volcanoes' sides. These deep cuts have revealed strata of older rock.
caption: The mountain with the appearance of a truncated cone, at the centre of the image, is Descabezado Grande volcano, and close to it is the pyramidal Cerro Azul.
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