Resuspension of volcanic ash from Mount St. Helens

Abstract

Measurements are presented of the size spectra of ash particles, previously deposited on the ground from the May 18, 1980 eruption of Mount St. Helens, that were resuspended into the air in eastern Washington. It is concluded that winds of just a few meters per second were capable of resuspending most of the smaller ash particles and that this caused dramatic reductions in visibility.