Refiner of Gold Creations

Mount St. Helens Facts

Photo: Peter Frenzen, 1982
From the
Mount St. Helens website

  • Mount St. Helens is the youngest of 15 stratovolcanoes of the Cascade Range from British Columbia to California.
  • Mount St. Helens is about 40,000 years old; by contrast, Mount Rainier is about 1 million years old.
  • The Mount St. Helens National Volcanic Monument was dedicated in 1982 and is 110,000 acres in size.
  • Previous Mount St. Helens eruptive periods:
    • 1500 C.E.
    • 1800 C.E.
    • 1831-1837 C.E.
  • Captain George Vancouver named Mount St. Helens in 1792 after Baron St. Helens, an English Diplomat.

View from Clearwater Ridge October 1999
Photo: EMC

Eruption Facts for May 18, 1980

Triggered by5.1 magnitude earthquake at 8:32 am
Original Height9,677 ft / 2950 m
Present Height8,363 ft / 2550 m
Total volume removed2/3 cu mi / 2.76 cu km
Debris Avalanche
Speed180 mph / 290 km/h (max)
Temperature160-212°F / 70-100°C
Distance Traveled 14 mi / 22 km West (Toutle River) (approx.)
5 mi / 8 km North (approx)

640 ft / 195 m (in North Fork Toutle R.) (max)
150 ft / 45 m (average)
Volume removed0.6 cu mi / 2.5 cu km
Lateral Blast
Speed Range: 225-730 mph / 60-1180 km/h
Average: 450 mph / 724 km/h
Temperature (singed zone) 120-390°F / 50-200°C
Blast Zone575-750°F / 300-400°C
Blast Area230 sq mi / 600 sq km
Vertical Plume
Height15 mi / 24 km (approx.)
Duration9 hours (approx.)
Pyroclastic Flows
Speed50-80 mph / 80-130 km/h
Temperature Near Crater: 1380-1560°F / 750-850°C
Most Flows: 570-1350°F / 300-730°C (average)
Distance Traveled5 mi / 8 km
Depth130 ft / 40 m (cumulative)
North Fork Toutle River65.4 million cu yds / 50 million cu mi
Upper Muddy River17 million cu yds / 13 million cu mi
SpeedUp to 90 mph / 145 km/h
Volume 0.0288 cu mi / 0.12 cu km
Mount Saint Helens Before 1980

Photo: J. Hughes, USDA Forest Service
From the Mount St. Helens website

Quick Facts

Coldwater Ridge3110 feet948 meters
Johnston Ridge4300 feet1311 meters
Windy Ridge4170 feet1271 meters
Mount St. Helens (prior)9677 feet2950 meters
Mount St. Helens (after)8363 feet2550 meters
Crater Dimensions
East to West1.2 miles2 kilometers
North to South1.8 miles4 kilometers
Depth2100 feet671 meters
Dome Dimensions
Height1000 feet305 meters
Width3450 feet1.1 kilometers
From Coldwater Ridge
Lava Dome8 miles12.8 kilometers
Base of Mountain6.3 miles10 kilometers
From Johnston Ridge
Lava Dome5.5 miles8.8 kilometers
Base of Mountain4.5 miles7.2 kilometers
From Windy Ridge
Lava Dome4.5 miles7.2 kilometers
Base of Mountain2.5 miles4 kilometers
Coldwater Lake
Length4.5 miles7.2 kilometers
Elevation2472 feet753 meters
Area800 acres324 hectares
Maximum Depth203 feet62 meters
Castle Lake
Length1.5 miles2.4 kilometers
Elevation2558 feet780 meters
Area200 acres81 hectares
Maximum Depth105 feet32 meters
Spirit Lake
Length3.2 miles5.2 kilometers
Elevation3475 feet1060 meters
Area3098 acres1254 hectares
Maximum Depth151 feet46 meters

  • Quick Fact Sheet supplied by the U.S. Forestry Service and Coldwater Ridge Visitor Center at the Mount St. Helens National Volcanic Monument. (as updated by Ed K. of USGS on 04/98)

View from Johnston Ridge October 1999
Photo: EMC

Forest Learning Center Facts

The May 18, 1980, eruption of Mount St. Helens sent more than 1,300 feet of the mountain's top cascading into the North Fork Toutle River Valley. Seconds later, a laterally directed blast devastated the surrounding 150,000 acres.
  • Nearly 68,000 acres of Weyerhaeuser's St. Helens Tree Farm was located within the eruption blast zone.
  • By the fall of 1982, Weyerhaeuser has salvaged 850 million board feet of dead timber. This was enough to build 85,000 three-bedroom homes.
  • Weyerhaeuser hand planted 18.4 million Douglas-fir (Pseudotsuga menziesii), noble fir (Abies procera), cottonwood (Populus balsamifera ssp. trichocarpa) and lodgepole pine(Pinus contorta var. latifolia) seedlings on over 45,500 acres in the devastated blast zone.


  • Celebrating the Return of the Forest Bookmark from the Charles W. Bingham Forest Learning Center at Mount St. Helens.
For more information on Mount St. Helens, visit:
Sunset on the Mountain October 1999
Photo: EMC