Holocene record of large explosive eruptions from Chaitén and Michinmahuida Volcanoes, Chile

摘要: Tephra fall deposits and one large ignimbrite close to Chaiten Michinmahuida Volcanoes were analyzed for chemistry radiocarbon dated correlate the eruptive units establish timing of eruptions. These data suggest that both volcanoes source (VEI ≥5) small moderate <5) explosive eruptions throughout Holocene. Four are associated with volcanic activity from Volcano, two Plinian at 9.9-9.5 5.3-4.9 (cal) ka BP also generated pyroclastic density currents. The last event recognized (prior 2008) occurred a few hundred years ago, producing similar those 2008 eruption. All products high-silica rhyolites; whole-rock compositions indistinguishable but glass subtly different some units. Seven related including deposit 7.6-7.3 10.5-10.2 BP. chemical these range andesite dacite. substantial eruption Volcano appears have been 0.5-0.3 sub-Plinian eruption, although younger scoria likely derived local cones found. Both pose wide variety potential hazards region ranging ignimbrite-forming pyroclastic-cone formation. Valleys adjacent areas most heavily affected by activity, because they inundated currents lahars. However, even regions located tens kilometers east north experienced accumulations tephra, which could harm agriculture infrastructure if events today.