Evolution of volcanic eruption columns

Abstract

The classical steady state model for Plinian eruption columns is extended to allow the source conditions at the volcanic vent to change in time. It is shown that when the source conditions change rapidly, over time scales typically less than approximately 3-4 min, this new time-dependent volcano model becomes appropriate. Differences between changes in source velocity and source temperature are also considered. Qualitatively similar structures are formed when either the source velocity or source temperature is reduced. A transient region is formed, characterized by a narrowing of the "top hat" eruption column radius. A first attempt to a model a Plinian eruption column, from its dynamic initiation in a volcanic eruption, is made. It is shown that the velocity at the front of the eruption column is significantly slower than the velocity at the same height in an established eruption column. Copyright 2009 by the American Geophysical Union.