Abstract
Chaiten Volcano erupted unexpectedly in May 2008 in one of the largest eruptions globally since the 1990s. It was the largest rhyolite eruption since the great eruption of Katmai Volcano in 1912, and the first rhyolite eruption to have at least some of its aspects monitored. The eruption consisted of an approximately 2-week-long explosive phase that generated as much as 1 km3 bulk volume tephra (~0.3 km3 dense rock equivalent) followed by an approximately 20-month-long effusive phase that erupted about 0.8 km3 of high-silica rhyolite lava that formed a new dome within the volcano’s caldera. Prior to its eruption, little was known about the eruptive history of the volcano or the hazards it posed to society. This edition of Andean Geology contains a selection of papers that discuss new insights on the eruptive history of Chaiten Volcano, and the broad impacts of and new insights obtained from analyses of the 2008-2009 eruption. Here, we summarize the geographic, tectonic, and climatic setting of Chaiten Volcano and the pre-2008 state of knowledge of its eruptive history to provide context for the papers in this edition, and we provide a revised chronology of the 2008-2009 eruption.
Highlights
Chaitén Volcano, located near 42.8°S in southern Chile, is a relatively small, remote rhyolitic volcano that sits about 17 km west-southwest of the much larger and heavily glaciated Michinmahuida Volcano (2,400 m elevation)
The eruption consisted of an approximately 2-week-long explosive phase that generated as much as 1 km3 bulk volume tephra (~0.3 km3 dense rock equivalent) followed by an approximately 20-month-long effusive phase that erupted about 0.8 km3 of high-silica rhyolite lava that formed a new dome within the volcano’s caldera
Little was known about the eruptive history of the volcano or the hazards it posed to society
Summary
Chaitén Volcano, located near 42.8°S in southern Chile, is a relatively small, remote rhyolitic volcano that sits about 17 km west-southwest of the much larger and heavily glaciated Michinmahuida Volcano (2,400 m elevation). It consists of a 3-km-wide caldera that, before 2008, contained an approximately 0.5 km lithic-and-obsidian rhyolite lava dome. Subduction of the Nazca and Antarctic plates obliquely beneath the South American plate fuels this volcanic arc, and segregates it into four distinct segments separated by volcanically inactive gaps (Stern, 2004) These segments are the Northern (NVZ; 5°N-2°S), Central (CVZ; 14°-27°S), Southern (SVZ; 33°-46°S), and Austral Volcanic Zones (AVZ; 49°-55°S), respectively. Catastrophic disturbance, whether caused by fire, landslides, volcanism, or severe winds is an important component of stand structure in this forest (Alaback, 1991)
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