A past-millennium maximum in postglacial activity from Volcán Chaitén, southern Chile

Abstract

Artículo de publicación ISIVolcan Chaitan (southern Chile, similar to 43 degrees S) initiated an historically unprecedented eruption in A.D. 2008, surprising the local inhabitants, Chilean and Argentine authorities, and the geologic community. Available data at the time indicated an absence of explosive eruptions from this rhyolitic volcano since a large-magnitude eruptive event dated at ca. 10,500 yr B.P. We present lake-sediment data from Lago Teo, a small closed-basin lake located in the immediate vicinity of both Chaiten township and the volcano, that spans the past a 10,000 yr and contains 26 pyroclastic fallout deposits. Glass-shard electron microprobe analyses revealed ten rhyolitic tephras indistinguishable in composition from the 2008 Volcan Chaiten eruption, and ten others potentially derived from the Michinmahuida volcanic complex. Among the rhyolites, we detected three closely spaced tephras deposited between ca. 9460 and 9680 yr B.P., followed by two thick tephras dated at ca. 7700 and ca. 5080 yr B.P. Three other closely spaced tephras occur between ca. 600 and 850 yr B.P., the most recent prehistoric event at ca. 420 yr B.P., and a 3-cm-thick tephra deposited during the 2008 event. We calculate a median recurrence of a 310 yr between eruptive events from all sources over the past a 10,000 yr, and a 200 yr between Volcan Chaiten events over the past millennium. Our results not only challenge the notion of an a 10,500-yr-long quiescence for Volcan Chaiten activity, but also suggest that the 2008 eruption was an overdue phenomenon in the context of its postglacial eruptive history, illustrating the advantage and absolute necessity of utilizing lake-sediment archives for developing continuous well-dated time series inventories of explosive volcanic events.Fondecyt 111061

Vegetation and climate change, fire-regime shifts and volcanic disturbance in Chiloé Continental (43°S) during the last 10,000 years

“…The Lago Teo record demonstrates that explosive volcanism has been a frequent phenomenon in the Chait en sector of the southern Andes during the last 10,000 years (Moreno et al, 2015). Our results indicate an average recurrence of~400 years between eruptive events with a background of at least 1 explosive eruption per thousand-year bin and peak frequency of events between 9000 and 10,000 cal yrs BP and during the last 1000 years (Fig.…”

“…5 and Supplementary Figure 4) except in W. trichosperma and Hydrangea. The tree W. trichosperma shows consistent statistically significant increases 100e150 years after the deposition of tephras originating from VC (CL ¼ 95% n ¼ 5), while the vine Hydrangea shows consistent statistically (Moreno et al, 2015). (For interpretation of the references to colour in this figure legend, the reader is referred to the web version of this article.)…”

“…Previous estimates were based on whole-rock geochemistry from the soilforming environments, constrained by limited radiocarbon dating of key horizons. More recently we reported a continuous lake sediment record from Lago Teo, a small closed-basin lake located in the immediate vicinity of Chait en township and volcano, that contains 26 tephras and spans uninterrupted the last 10,000 years (Moreno et al, 2015). This precisely dated record features 10 tephras derived from VC, including the 2008 eruption, 10 from the Michinmahuida Volcanic Complex (MVC) and 6 from as yet unknown eruptive sources (Moreno et al, 2015).…”

“…More recently we reported a continuous lake sediment record from Lago Teo, a small closed-basin lake located in the immediate vicinity of Chait en township and volcano, that contains 26 tephras and spans uninterrupted the last 10,000 years (Moreno et al, 2015). This precisely dated record features 10 tephras derived from VC, including the 2008 eruption, 10 from the Michinmahuida Volcanic Complex (MVC) and 6 from as yet unknown eruptive sources (Moreno et al, 2015). The high frequency of volcanic activity and relatively high sediment-accumulation rates from Lago Teo motivated us to study the effects of volcanic disturbance on past vegetation and fire regime shifts at multidecadal and centennial timescales under different climatic states during the Holocene.…”

Using Lake Sediment Cores to Improve Records of Volcanism at Aluto Volcano in the Main Ethiopian Rift

“…Unlike terrestrial sections, which may be subject to remobilization, erosion, and pedogenesis, lake tephras can record relatively small events (e.g., Kuehn & Negrini, 2010;Moreno et al, 2015) and consequently preserved a good record of Aluto's Holocene eruptive history. Unlike terrestrial sections, which may be subject to remobilization, erosion, and pedogenesis, lake tephras can record relatively small events (e.g., Kuehn & Negrini, 2010;Moreno et al, 2015) and consequently preserved a good record of Aluto's Holocene eruptive history.…”