A simplified equation of state for the density of silicate hydrous magmas: An application to the Popocatépetl buoyancy-driven dome growth process

We present a simplified equation of state (EOS) for calculating the density of hydrous siliceous magmas in a range of pressures, temperatures and dissolved water content of interest to study several magma conduit processes. A simpler linear form and a more precise non-linear, yet simple form of the equation, both valid in the range 0 to 0.25 GPa, 800 to 1000 K, and 0 to 7 wt.% H2O are proposed for the dacitic and andesitic Popocatépetl magma melt compositions. We apply these equations to explain some aspects of the dome-forming effusive activity that has been observed at Popocatépetl volcano since 1996. This model poses a density reduction dependent mainly on the volatile contents of the magma filling the volcano conduit system as the driving buoyancy force causing magma extrusions and dome growth.