Abstract

Vulcanian eruptions are a common, and extremely hazardous, form of volcanic activity that produce plumes of hot volcanic gas and ash. Such eruptions can produce significant eruption volumes, as recent VEI3 eruptions at Montserrat and Sakurajima demonstrate. The vent conditions are not well described by approximation to either steady or instantaneous sources. The eruptions are of short duration, typically seconds—mintues, and are characterized by unsteady source conditions.

The classical steady state “plume equations” due to Morton, Taylor & Turner are developed to allow for use in unsteady multiphase flow, including Vulcanian eruptions. New measurement techniques allow field observations from Santiaguito Volcano, Guatemala to be used as input boundary conditions to the developed model enabling comparison with plume rise-height observations. Large errors in eruption parameters are shown to occur if steady models are incorrectly used to invert, for example, deposit measurements to infer source conditions for historic or unobserved eruptions.