SILS Information Bulletin

Number: 06-14 Rebuilding Mount St. Helens

By: Steve P. Schilling, David W. Ramsey,

James A. Messerich, and Ren A. Thompson

Date: August 15, 2006

Stock # 206599 (Scientific Investigations Map 2928)

Price: $7.00 for the map, plus $5.00 handling

On May 18, 1980 Mount St. Helens, Washington exploded in a devastating eruption that shocked the world. The eruption, one of the most powerful in the history of the United States, removed 2.7 kilometers of rock from the volcano’s edifice, the bulk of which had been constructed by nearly 4,000 years of lava-dome-building eruptions. In seconds, the mountains summit elevation was lowered from 2,950 meters to 2,549 meters, leaving a north-facing horseshoe shaped crater over 2 kilometers wide.

Following the 1980 eruption, Mount St. Helens experienced two decades of dome building in the

center of the volcano’s empty crater. Long the most active volcano in the Cascade Range with a complex 300,000 year history, Mount St. Helens erupted again in the fall of 2004 as a new period

of dome building began within the crater.

Vertical aerial photographs document dome growth and glacier deformation. These photographs enabled photogrammetric construction of a series of high-resolution digital elevation models (DEMs) showing changes from October 4, 2004 to February 9, 2006. From the DEMs, Geographic Information Systems (GIS) applications were used to estimate extruded volumes and growth rates of the new lava dome. The DEMs were also used to quantify dome height variations, size of the magma conduit opening, and the mechanics of dome emplacement.

Previous lava-dome-building eruptions at the volcano have persisted intermittently for years to decades. Over time, such events constructed much of the cone shaped mountain seen prior to the May 1980 eruption. Someday, episodic dome growth may eventually rebuild Mount St Helens to its pre-1980 form.

This map measures approximately 25x38 inches and is available from USGS Science Information and Library Services (SILS). To place an order, call the SILS offices at 1-888-ASK-USGS, or visit:

http://www.usgs.gov. Orders may also be placed through the USGS Store at: http://store.usgs.gov May be viewed or downloaded online at: http://pubs.usgs.gov/sim/2006/2928

Sheryle Girk-Jackson 303 202 4176, FAX 303 202 4633, email: sjjackson@usgs.gov