F. Sigmundsson

Crustal‐stored magma reservoirs contain exsolved volatiles which accumulate in the reservoir roof, exerting a buoyancy force on the crust. This produces surface uplift and sudden loss of volatiles through eruption results in syn‐eruptive subsidence. Here, we present three‐dimensional, visco‐elasto‐plastic, numerical modeling results which quantify the ground deformation arising from the growth and release of a volatile reservoir. Deformation is mostly independent of crustal thermal distribution and volatile reservoir shape, but is a function of volatile volume, density and depth and crustal rigidity. We present a scaling law for the volatiles' contribution to syn‐eruptive subsidence and show this contributes ∼20% of the observed subsidence associated with the 2015 Calbuco eruption. Our results highlight the key role that volatile‐driven buoyancy can have in volcano deformation, show a new link between syn‐eruptive degassing and deflation, and highlight that shallow volatile accumulation and release may have a significant impact on ground deformation of volcanoes.