Reply to the comment by Mike R. James et al. on “It takes three to tango: 2. Bubble dynamics in basaltic volcanoes and ramifications for modeling normal Strombolian activity”

摘要

The current paradigm for normal eruptions at Stromboli volcano and Strombolian‐type activity more generally posits that each eruption represents the burst of a large pocket of gas, commonly referred to as slug, at the free surface of the magma column. This slug model has been investigated and refined primarily through analog fluid dynamical experiments at the laboratory scale. There is no doubt that these studies have advanced our understanding of Strombolian eruptions considerably. However, given the very fundamental status of the slug model for our current thinking about Strombolian‐type eruptions, it is paramount to carefully assess all underlying assumptions of the model. One important uncertainty lies in the scaling behavior of the observed slug dynamics in the laboratory. Scale invariance requires all nondimensional numbers to be identical, but it is generally not feasible to match all of the nondimensional numbers characterizing the volcanic conduit exactly in a laboratory experiment. Numerical computations offer a means of directly comparing slug dynamics at drastically different scales [Suckale et al., 2010b]. We find that the very large slugs in volcanic conduits are more prone to dynamic instabilities and breakup than the comparatively small slugs in laboratory settings. This finding in itself does of course not ‘disprove’ the slug model: it merely points to potentially important differences in slug stability at volcanic scales as opposed to laboratory scales.