A Model for Dispersal of Eruption Ejecta

Abstract

Solid and liquid particulate materials that are ejected by hydrothermal or volcanic eruptions are subsequently dispersed by atmospheric wind currents while falling under gravity to the Earth's surface. Particle sizes are not uniform and may indeed change during flight owing to coalescence and/or fragmentation. Wind conditions (speed, direction and turbulence) may also change with elevation (and with time).
In an attempt to determine the most important physical factors, a quantitative model that reflects the above influences on particle dispersal is outlined. Analytic solutions to the mathematical model are sought wherever possible, since an analysis of the sensitivity of the predicted distributions to the numerous parameters involved is then more readily undertaken. Numerical simulations have also been made. Some example calculation results are compared with measured eruption deposit patterns published in the geological literature; these comparisons indicate that the proposed model reflects various characteristics of the measured data well.