The Injection of Volcanic Ash into the Atmosphere

In this paper, we present some physical models that can describe the ascent of volcanic ash into the atmosphere during a volcanic eruption. We consider both sustained volcanic eruption columns and discrete volcanic thermal clouds. To test the modeling approach, we compare our predictions of the ascent rate of a model cloud with some observations of the ascent of the ash cloud during the April 15, 1990, eruption of Redoubt Volcano, Alaska. We also consider the radial spreading of ash as a gravity current following emplacement by the column and compare our theory with the observations from the April 21, 1990, eruption of Redoubt, Alaska. Both styles of eruption behavior are hazardous for aircraft.