By

David W. Ramsey, Carolyn L. Driedger, and Steve P. Schilling

2008

Mount St. Helens has erupted more frequently than any other volcano in the 

Cascade Range during the past 4,000 years. The volcano has exhibited a variety of 

eruption styles—explosive eruptions of pumice and ash, slow but continuous 

extrusions of viscous lava, and eruptions of fluid lava. Evidence of the volcano’s 

older eruptions is recorded in the rocks that build and the deposits that flank the 

mountain. 

Eruptions at Mount St. Helens over the past three decades serve as reminders of 

the powerful geologic forces that are reshaping the landscape of the Pacific 

Northwest. On May 18, 1980, a massive landslide and catastrophic explosive 

eruption tore away 2.7 cubic kilometers of the mountain and opened a gaping, 

north-facing crater. Lahars flowed more than 120 kilometers downstream, 

destroying bridges, roads, and buildings. Ash from the eruption fell as far away as 

western South Dakota.

Reconstruction of the volcano began almost immediately. Between 1980 and 1986, 

80 million cubic meters of viscous lava extruded episodically onto the crater floor, 

sometimes accompanied by minor explosions and small lahars. A lava dome grew 

to a height of 267 meters, taller than the highest buildings in the nearby city of 

Portland, Oregon. Crater Glacier formed in the deeply shaded niche between the 

1980-86 lava dome and the south crater wall. Its tongues of ice flowed around the 

east and west sides of the dome. 

Between 1989 and 1991, multiple explosions of steam and ash rocked the volcano, 

possibly a result of infiltrating rainfall being heated in the still-hot interior of the dome 

and underlying crater floor.

In September 2004, rising magma caused earthquake swarms and deformation of 

the crater floor and glacier, which indicated that Mount St. Helens might erupt again 

soon. On October 1, 2004, a steam and ash explosion signaled the beginning of a 

new phase of eruptive activity at the volcano. On October 11, hot rock reached the 

surface and began building a new lava dome immediately south of the 1980-86 lava 

dome. The erupting lava cleaved Crater Glacier in half and bulldozed it aside, 

causing thickening, crevassing, and rapid northward advance of the glacier’s east 

and west arms. Intermittent steam and ash explosions, some generating plumes 

that rose up to 11 kilometers, preceded and accompanied extrusion of the new lava 

dome, but ceased by early 2005.

As the new dome grew, a series of large fins or spines of hot lava rose, some more 

than 100 meters high, and then crumbled producing sometimes spectacular rock 

falls. The largest of these rock falls generated dust or steam plumes that rose high 

above the crater rim. By February 2006, the new dome had grown to a volume 

similar to that of the 1980-86 lava dome; and by July 2007, the new dome had grown 

to a volume of 93 million cubic meters, exceeding the volume of the 1980-86 lava 

dome. The height of the new dome also exceeded that of the 1980-86 lava dome, 

and at its highest point (before collapse in 2005) reached to within 2 meters of the 

lowest point on the south crater rim. At this height, the new dome was taller than the 

Empire State Building in New York City.

The new lava dome initially grew very quickly, at rates of 2 to 3 cubic meters (one 

small dump truck load) per second. If it had continued to grow at these rates for 

about 100 years, it would have replaced the volume of rock removed from the 

volcano during the May 18, 1980, eruption. However, the lava extrusion rate slowed 

throughout the eruption, and, by July 2007, it was oozing at a rate of 0.1 cubic 

meters per second. At that rate, it would take over 700 years to replace the volume 

of rock lost in 1980. Lava dome extrusion has continued into early 2008.

U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Map 3008

Mount St. Helens, Washington

SELECTED REFERENCES

Clynne, M. A., Ramsey, D. W., and Wolfe, E. W., 2005, Pre-1980 eruptive history of Mount St.

 Helens, Washington: U.S. Geological Survey Fact Sheet 2005-3045, 4 p.,

 http://pubs.usgs.gov/fs/2005/3045

Major, J. J., Scott, W. E., Driedger, Carolyn, and Dzurisin, Dan, 2005, Mount St. Helens erupts

 again; Activity from September 2004 through March 2005: U.S. Geological Survey Fact

 Sheet 2005-3036, 4 p., http://pubs.usgs.gov/fs/2005/3036

Moore, J. G., and Albee, W. C., 1981, Topographic and structural changes, March-July 1980-

 Photogrammetric data, in Lipman, P. W. and Mullineaux, D. R., eds., The 1980 eruptions

 of Mount St. Helens, Washington: U.S. Geological Survey Professional Paper 1250, p.

 123-134.

Schilling, S. P., Ramsey, D. W., Messerich, J. A., and Thompson, R. A., 2006, Rebuilding Mount

 St. Helens: U.S. Geological Survey Scientific Investigations Map 2928,

 http://pubs.usgs.gov/sim/2006/2928

Swanson, D. A., and Holcomb, R. T., 1990, Regularities in growth of the Mount St. Helens dacite

 dome, 1980-1986, in Fink, John, ed., The mechanics of lava flow emplacement and dome

 growth: International Association of Volcanology and Chemistry of the Earth’s Interior,

 Proceedings in Volcanology, v. 2, Berlin, Springer-Verlag, p. 3-24.

A. Digital perspective view derived from USGS Digital 

Elevation Model (DEM) of Mount St. Helens as seen 

from the northwest prior to the catastrophic eruption of 

May 18, 1980. Created with Geographic Information 

Systems (GIS). 

B. Digital perspective view derived from USGS DEM of 

Mount St. Helens following the catastrophic eruption of 

May 18, 1980. The 1980-86 lava dome has begun 

growing in the center of the crater.

D. Digital perspective view derived from both LIDAR 

DEM and DEM constructed by photogrammetric 

techniques, showing new lava dome, 1980-86 dome, 

and advancing Crater Glacier on July 5, 2007.

C. Light Detection And Ranging (LIDAR)-derived digital 

perspective view of the volcano on September 22, 2003, 

one year before the start of its latest eruption. The 

1980-86 lava dome and Crater Glacier occupy the crater.

Steam and ash plume at Mount St. Helens as viewed from Vancouver, Washington on March 8, 

2005. Top of plume is about 11 kilometers above sea level. (Photograph by Matthew Logan).

Hot fin of lava rising from growing lava dome on May 30, 2006. Forward Looking Infrared (FLIR) 

image shows rock temperature. (Photograph by William E. Scott, FLIR by James W. Vallance).

Avalanche deposits originating from crumbling of lava fin (photo above) on May 29, 2006, sweep 

almost 1.5 kilometers across the east arm of Crater Glacier and the crater floor. (Photograph by 

William E. Scott).

Mount St. Helens is one of 13 active 

volcanic centers in the U.S. Cascade 

Range. All have the capability to 

erupt again. To help protect lives and 

property, scientists with the U.S. 

Geological Survey (USGS) Volcano 

Hazards Program maintain close 

watch on volcanic regions of the U.S. 

This ongoing work enables the USGS 

to detect early signs of volcanic unrest 

and to warn the public of impending 

eruptions.

Plan: Develop a natural hazards

emergency plan with your family

Learn: Learn whether you live, work

or go to school in a volcano hazards

zone

Inquire: Ask officials about your

community’s emergency response

plan

A New Perspective on Mount St. Helens—Dramatic Landform Change and Associated Hazards 

at the Most Active Volcano in the Cascade Range

Printed on recycled paper

Manuscript approved for publication February 6, 2008 Digital image processing by Lisa M. Faust

Any use of trade, product, or firm names in this publication is for descriptive 

purposes only and does not imply endorsement by the U.S. Government.

For sale by U.S. Geological Survey, Information Services, Box 25286, 

Federal Center, Denver, CO, 80225, 1–888–ASK–USGS

Digital files available at http://pubs.usgs.gov/sim/3008

Pre-1980

2003 2007

1980

A B

C D

1980 1985 1990 1995 2000 2005

TIMELINE OF RECENT ACTIVITY AT MOUNT ST. HELENS

May 18, 1980

explosive eruption

1980-86

lava dome extrusion

1989-91

steam and ash explosions

October 1, 2004

steam and ash explosion

Since 2004

lava dome extrusion

photograph by Robert Krimmel photograph by Lyn Topinka photograph by Lyn Topinka photograph by John Pallister photograph by Daniel Dzurisin