Skip Links

USGS - science for a changing world

Geologic Investigations Series Map I-2463

Geologic Map of the Sasquatch Steps Area, North Flank of Mount St. Helens, Washington

By Brian P. Hausback

Thumbnail of and link to report PDF (2.5 MB)Summary

The 1980 eruption of Mount St. Helens resulted in both new volcanic deposits and deeply incised exposures into pre-1980 deposits. These exposures were produced by excavation of the crater by the 1980 landslides and lateral explosion as well as the subsequent erosion of Step and Loowit creeks by northerly stream flow out of the horseshoe-shaped crater. The map covers the area known as the Sasquatch Steps (commonly called the Steps), which lies between the Pumice Plain on the north and the lowermost portion of the crater on the south. Rapid alluvial aggradation at the base of the Steps is presently burying some of the lowest exposures, and erosion is stripping many of the upland deposits. The stratigraphic sequence exposed in the map area includes deposits from the eruptive periods listed in table 1 (Crandell, 1987). Assignment of deposits to the various eruptive periods is based on lithology and ferromagnesian-mineral suites typical for each of the eruptive periods (Mullineaux and Crandell, 1981; Mullineaux, 1986), as well as three 14 C dates from wood found in the deposits. Faults displayed on the map are largely confined to the older part of the stratigraphic section. These older units are highly shattered, with an extremely complicated fracture pattern, and it is only possible to show the largest and most distinctive of these structures at the map scale. Interpretation of the stratigraphy and structure of this area is given in Hausback and Swanson (1990).

First posted March 30, 2001

  • Map PS (12.5 MB)
    A PostScript version of the map for plotting. This map is approximately 42 inches wide by 53 inches high and, therefore, may not plot correctly on a 36-inch-wide plotter
  • For questions about the content of this report, contact Brian Hausback

For additional information, contact:
National Cooperative Geologic Mapping Program
U.S. Geological Survey
12201 Sunrise Valley Drive, MS 908
Reston, VA 20192

Part or all of this report is presented in Portable Document Format (PDF). For best results viewing and printing PDF documents, it is recommended that you download the documents to your computer and open them with Adobe Reader. PDF documents opened from your browser may not display or print as intended. Download the latest version of Adobe Reader, free of charge.

Suggested citation:

Hausback, Brian P., 2000, Geologic Map of the Sasquatch Steps Area, North Flank of Mount St. Helens, Washington: U.S. Geological Survey Geologic Investigation Series Map I-2463, 1 plate,

Accessibility FOIA Privacy Policies and Notices logo U.S. Department of the Interior | U.S. Geological Survey
Page Contact Information: Contact USGS
Page Last Modified: Wednesday, November 30, 2016, 05:41:06 PM