A common fate to all silicic eruptions?

Thomas Giachetti

University of Oregon 

Crater of Cordón Caulle, Chile, January 2025 (Credit: Thomas Giachetti)

Silicic magmas have produced some of the most voluminous and intense eruptions of the Holocene (e.g., Taupo, Mount Mazama, Novarupta). However, the first and only observations of rhyolitic eruptions at Chilean volcanoes Chaitén and Cordón Caulle are just fifteen-year-old. These two VEI 4-5 eruptions both progressed from explosive, (sub-)Plinian events to a less stable phase, with observations of hybrid activity where the eruption was simultaneously explosive and effusive. Both eruptions ended with the emplacement of a rhyolitic lava dome/flow. Through detailed field work and laboratory analyses of the explosive deposits of three other VEI 4-5 silicic eruptions in the United States Cascades (Newberry Volcano, Medicine Lake Volcano, Mount Mazama), I will try to disentangle the different eruptive phases of these eruptions and convince you that this progression is common to most, if not all, silicic eruptions of that size.

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In the Hop Mahal Room

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7:00 pm presentation

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