A THEORETICAL MODEL FOR A VOLCANIC COLUMN-PLUME

A set of simultaneous equations based upon the hydrodynamics and thermodynamics of a volcanic column-plume are derived and cast into the framework of a one-dimensional computer model. These equations were modified to account for the concentration of ash material, the drag forces resulting from larger-than-ash pyroclastic material, and the ratio of carbon dioxide to steam in the gaseous effluent.;Mean flow velocity, differential temperature above the ambient environment, ash fraction, plume composition, plume radius, particulate size distribution, and particle velocities, are given as functions of altitude above the vent. A series of sensitivity tests were run as a validation of the physical basis of the model. Results of these studies revealed the sensitivity of the model to changes in the flow parameters, solid particulate parameters, gaseous constituents, and environmental parameters. The effects of these changes on velocity, radius, differential temperature and maximum plume height are presented. (Abstract shortened with permission of author.).