Force, Flight and Fallout: Progress on Modelling Hydrothermal Eruptions

Abstract

McKibbin (1989) began development of a mathematical model for hydrothermal eruptions. Early work concentrated on modelling the underground process, while lately some attempts have been made to model the eruption jet and the flight and deposit of ejected material. Conceptually, the model is that of a boiling and expanding two-phase fluid rising through porous rock near the ground surface, with a vertical high-speed jet, dominated volumetrically by the gas phase, ejecting rock particles that are then deposited on the ground near the eruption site. Reported field observations of eruptions in progress and experimental results from a laboratory-sized model have confirmed the conceptual model. The quantitative models for all parts of the process are based on the fundamental conservation equations of motion and thermodynamics, using a continuum approximation for each of the components. The three main zones of interest (underground flow, eruption jet and plume dispersion) may be connected to form an approximate, but complete, quantitative model of a hydrothermal eruption.