Sinking of Volcanic Ash in Uncompacted Sediment in Williams Lake, Washington

Abstract

Volcanic ash from the eruption of Mount St. Helens on 18 May 1980 fell into Williams Lake in eastern Washington and was temporarily suspended at the sediment-water interface. After several months of compaction, the ash layer broke up and sank into lower density uncompacted lake sediment. Stratigraphic time displacements of several hundred years and a failure to recognize discontinuous ash layers in sediment cores are possible consequences of this process.