Rise and Collapse of Volcanic Plumes Produced By Explosive Basaltic Fissure Eruptions

Abstract:

Explosive basaltic fissure eruptions, which release large amounts of sulfur gases in the atmosphere, can have a big impact on climate. The effect on climate depends on the rate of gas injection above the tropopause. The key parameter is the height reached by the eruptive plume as a function of mass flux and entrainment rate. We propose a model of entrainment in 2D volcanic plumes based on lab scale experiments on turbulent jets and plumes. In this model, entrainment varies with the Richardson number and we predict that the height of the column critically depends on the source buoyancy flux determined by the eruptive temperature and the amount of gas in the volcanic mixture at the vent. We obtain that “hot” basaltic planar plumes form stable eruptive columns, even for large eruption rates. Only if fragmentation is not efficient enough, the column collapse will prevent the injection of gas in the stratosphere.