Fallout and distribution of volcanic ash over Argentina following the May 2008 explosive eruption of Chaitén, Chile

摘要: [1] The major explosive eruption of Chaiten volcano, Chile, in May 2008 provided a rare opportunity to track the long-range dispersal and deposition fine volcanic ash. The followed ∼10,000 years quiescence, was largest globally since Hudson, 1991, first rhyolitic Novarupta, Alaska, 1912. Field examination distal ashfall indicates that ∼1.6 × 1011 kg ash (dense rock equivalent volume ∼0.07 km3) deposited over ∼2 105 km2 Argentina during week eruption. minimum magnitude, estimated from mass tephra deposit, is 4.2. Several discrete units are identifiable their distribution grain size characteristics, with more energetic phases showing bimodal evidence cloud aggregation processes. Ash chemistry uniform throughout early stages consistent magma storage prior at depths 3–6 km. Deposition continental region allowed tracking development demonstrates potential complexity single eruption, which this case comprised several week-long period intense activity.