Application of an advection-diffusion model for volcanic ash dispersion: The Hudson volcano eruption (1991) in Chile

To be able to estimate the thicknesses of the volcanic ash which is deposit ed at the ground level, a numerical model of advection-diffusion type is ap plied to the second eruptive phase of the Hudson volcano (45 degrees 54'S-7 2 degrees 58'W), Chile, initiated August 12, 1991. The eruption of plinian character came from a crater of 800 m of diameter, producing columns of gas es and ashes which reached a heights up to 18 Km. The application of a mode l which considers processes of horizontal advection, turbulent diffusion, v ertical deposition and the topography of the ground allows us to obtain the spatial distribution of the isopachs which comparatively presents a simila r disposition to those observed. The results obtained indicate a porce ntua l relative error which vary from a 6% for ash thicknesses of about 150 cm t o about a 30% for ash thicknesses of 10 cm.