Influence of volcanic ash from the May 18, 1980, eruption of Mount St. Helens on the properties of soils

Alan Goldin

ABSTRACT:

Volcanic ash from the May 18, 1980, eruption of Mount St. Helens was deposited to a depth of 3 millimeters (.12 inch) or more across Washington, Idaho, and Montana. Particle size of the ash decreases with increasing distance from the mountain. Amounts of salt and fertilizer elements in the ash generally are small and correlate well with ash depth. The ash is highly permeable and dispersive, with a high infiltration rate and high water-holding capacity. Vegetation, organic matter, and structure in the surface horizons should re-establish within tens of years Weathering of the ash to form allophane and the formation of a spodic horizon will take at least 6,600 years.

Footnotes

Alan Goldin is a soil survey party leader with the Soil Conservation Service, U.S. Department of Agriculture, Bellingham, Washington 98225. This report is based on a paper presented in August 1981 at SCSA's 36th annual meeting in Spokane, Washington. The author thanks Dennis Nettleton for providing most of the technical data used in this study and Jack Rasmussen for his support and encouragement of the research.
Copyright 1982 by the Soil and Water Conservation Society

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