The products of primary magma fragmentation finally revealed by pumice agglomerates

Abstract Following rapid decompression in the conduit of a volcano, magma breaks into ash- to block-sized fragments, powering explosive sub-Plinian and Plinian eruptions that may generate destructive pyroclastic falls flows. It is thus crucial assess how up fragments. This task difficult, however, because subterranean nature entire process original size pristine fragments modified by secondary fragmentation expansion. New textural observations pumice lapilli reveal some primary products survive sintering together within seconds break-up. Their distributions reflect energetics fragmentation, consistent with experiments. Pumice aggregates offer unique window previously inaccessible could be used determine potential energy fragmentation.