Physical constraints for effective magma-water interaction along volcanic conduits during silicic explosive eruptions

Aravena et al. (2018) breathed fresh air into understanding the role of external water in silicic phreatomagmatic eruptions with their hypothesis that significant involvement of external water is only feasible above the level of primary fragmentation of the magma. We discuss here strong supporting evidence that primary fragmentation does not involve external water from the microtextures of the pyroclasts erupted from the two ‘type’ examples of large-scale interaction of silicic magma with external water.