Conduit processes during the February 11, 2010 Vulcanian eruption of Soufrière Hills, Montserrat

Abstract

Abstract We analyzed pumice from the February 11, 2010 Vulcanian explosion that immediately followed a large dome collapse at Soufriere Hills volcano. We obtained pre-explosive values of porosity, pressure, and depth by combining textural analyses and glass water content determinations. Our data suggest that the February 2010 explosion evacuated the upper 3\u202fkm of the conduit from the dense magma (≤10\u202fvol% porosity) it contained. The low porosity distribution in the volcanic conduit implies that the magma rising from the reservoir had time to extensively degas during emplacement. We use a conduit flow model to characterize the effects of permeability on ascent conditions. Model input parameters were fitted to match our pre-explosive porosity data, which yielded first-order constraints on conduit radius, mass flux, outgassing efficiency, and permeability. This parametric study suggests that efficient lateral gas escape is necessary to explain the low pre-explosive porosities. Steady-state solutions fitting the observed range of dome extrusion rate in the month preceding the February 11 event suggest permeabilities