Abstract
The 2008 eruption of Chaiten Volcano was widely cited as the first activity at the volcano for over 9000 years. However, we have identified evidence from proximal pyroclastic deposits for three additional explosive eruptions of Chaiten within the past 5000 years. Chaiten has therefore produced at least five explosive eruptions in the Holocene, making it among the most active volcanoes, in terms of explosive output, in the southern part of the Andean Southern Volcanic Zone. All of the five identified Holocene explosive eruptions produced homogeneous high-silica rhyolite, with near identical compositions. Based on our pyroclastic sequence, we suggest that the largest-volume Holocene eruption of Chaiten occurred at ~4.95 ka, and we correlate this with the Mic2 deposit, which was previously thought to originate from the nearby Michinmahuida Volcano.
Highlights
Little was known about the Holocene eruption history of Chaitén Volcano before its most recent eruption in 2008
Based on our pyroclastic sequence, we suggest that the largest-volume Holocene eruption of Chaitén occurred at ~4.95 ka, and we correlate this with the Mic2 deposit, which was previously thought to originate from the nearby Michinmahuida Volcano
Chaitén is situated in a remote forested region of southern Chile (42.8°S, 72.6°W), in the southern part of the Andean southern volcanic zone (SVZ; Stern, 2004)
Summary
Little was known about the Holocene eruption history of Chaitén Volcano before its most recent eruption in 2008. Chaitén is situated in a remote forested region of southern Chile (42.8°S, 72.6°W), in the southern part of the Andean southern volcanic zone (SVZ; Stern, 2004) Tephrochronological investigations in this region have focussed primarily on deposits from the largest explosive eruptions (Naranjo and Stern, 2004; Watt et al, 2011a). Previous work by Naranjo and Stern (2004) recognised a pyroclastic surge and rhyolitic tephra fall deposit from Chaitén, named Cha, dispersed northwards and dated at ~9.75 ka (based on calibrated radiocarbon ages; Watt et al, 2011a). An additional rhyolitic tephra deposit, named Mic, was identified and dated by Naranjo and Stern (2004) ~100 km east of Chaitén, in Argentina. We report on a proximal sequence of pyroclastic deposits, which provides potential evidence for mid- to late-Holocene eruptions at Chaitén and the opportunity for correlation with previously identified distal tephra deposits such as Mic
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