Satellite-based evidence for a large hydrothermal system at Piton de la Fournaise volcano (Reunion Island)

Abstract

[1] Hydrothermal systems are active structures present at many volcanoes. Their characterization is essential as they reveal the evolution of the magmatic source and may play a role in the eruptive style. Many studies have already suggested the existence of a shallow hydrothermal system beneath the summit craters at Piton de la Fournaise volcano (La Reunion), although there is still no clear evidence. Here we present new arguments on the basis of satellite-based data acquired during April 2007 eruption suggesting the existence of a large hydrothermal system beneath the Dolomieu crater at Piton de la Fournaise. SO2 released during the collapse phase of the Dolomieu crater (∼April 6–13) has been estimated at 935 ± 244 kilotons whereas erupted SO2 calculated from lava effusion rates was found to be clearly insufficient (179 ± 89 kilotons). We suggest that the excess of SO2 originated from a large hydrothermal system suddenly opened by the collapse.