The Eruption of Mt. St. Helens in 1980
Originally standing as the fifth tallest peak in Washington, Mount Saint Helens is also recognized as the state's most active volcano.
Location of the five stratovolcanoes located in Washington State, with their elevations.
Washington State is home to five major stratovolcanoes, including Mount Rainier (its most famous), Mount Saint Helens, Mount Adams, Mount Baker, and Glacier Peak. These five volcanoes were formed and continue to be active due to the slow collision of two of Earth's tectonic plates, the Juan de Fuca Plate and the Pacific Plate. Each are located with the Cascade Mountain Range, which spans from British Columbia to the state of California. [1]
Within the last 4,000 years, Washington has experienced an average of one to two eruption events per century. [2] Although Mount Saint Helens is the smallest of these five volcanoes, with an original elevation of 9,677' feet, the eruption of the mountain on May 18, 1980 was the largest volcanic event in the state within this century. Following that event, Mount Saint Helens continued its lava dome building from 1980-1986 and again in 2004-2008.
The Cascade Range's Most Active Volcano
Mount Saint Helens sits in the southwestern part of Washington's Cascade Mountain Range. It lies 97 miles south of Seattle, Washington and 52 miles northeast of Portland, Oregon.
On a clear day, the surrounding peaks of Mount Rainier, Mount Adams, Mount Hood, Mount Jefferson, and Three Sisters can be seen from the summit of the mountain.
To this day, Mount Saint Helens continues to hold the highest probability for eruption out of all U.S. volcanoes, with the except of those in Hawaii and Alaska. [3]
One From Whom Smoke Comes
Aptly named, the original indigenous name for the mountain is lawilátɬa (alternatively written as Loowit or Louwala-Clough) which roughly translates to "one from whom smoke comes" or "smoking mountain." [4][5]
Today, Mount Saint Helens has a horseshoe-shaped crater where its dome once stood, which slopes down towards the north. The highest part of the crater rim remains on the southwestern side. [6]
The Path of the May 18th, 1980 Eruption
On the day of May 18th, 1980 a local earthquake with a magnitude of 5.1 created the necessary pressure dynamics allowing for Mount Saint Helens' magma layer to release. [7]
A mixture of magma and groundwater erupted in a lateral blast out of the northern flank of the mountain, which flattened 230 square miles of forest within a matter of minutes. The blast triggered a series of avalanches of gas and pumice ("pyroclastic flows") as well as mudflows created from floodwater that carved through the surrounding valley. [8]
The eruption event lasted approximately 9 hours and released a total of 540 million tons of ash. The USGS has made the comparison that the non-compacted volume released was equal to a football field piled 150-miles high with loose ash. [9]
The remnant ash cloud spread across the United States (detected in northeastern cities within two days of the blast) and ultimately reached the full global atmosphere within two weeks. [10]
Johnston Ridge Observatory
On the day of the May 18th, 1980 eruption, volcanologist David Johnston witnessed the beginning of the event from a spot approximately five miles away and was the first to notify the USGS Vancouver Office of the natural disaster. It is widely recognized that Johnston played a significant role in closing off the area directly surrounding the volcano prior to the eruption due to safety concerns, and as a result saved hundreds of lives. Johnston himself died during the eruption.
The Johnston Ridge Observatory was opened to the public in 1997 and has historically remained a tourist attraction to view the northern flank of Mount Saint Helens in its entirety. [11]
National Volcanic Monument
In 1982, the Mount Saint Helens National Volcanic Monument was created by Congress and continues to be maintained by the U.S. Forest Service (USFS). It covers an area of 110,000 acres total. [8]
Today, the southern side of the mountain remains a popular non-technical climb and is accessed year-round by mountaineers who wish to "summit" the remaining mountain up to the highest point of the crater rim. [12]
"I saw this huge gray cloud in the western sky. Over the next few hours, the sky darkened, street lights came on, and very fine ash started to accumulate. By noon, there was no visible sun, and it was pitch black."
3D Diorama of Mount Saint Helens, Post-1980 Eruption (created by Camille VanSkiver)
The 3D rendering of Mount Saint Helens depicted above provides a detailed view of the resultant local topography of Mount Saint Helens and exemplifies the direction of the lateral blast towards Spirit Lake to the north-northeast.
Mount Saint Helens' summit sat at 9,677' in elevation before the eruption event on May 18th, 1980 and now reaches 8,365' at the highest point on its remaining crater rim. [6] During that eruption event, 3.4 billion cubic yards of material was displaced from the volcano's cone. [8]
Pre-1980 Eruption Elevation of Mount Saint Helens (by Camille VanSkiver)
Post-1980 Eruption Elevation of Mount Saint Helens (by Camille VanSkiver)
The elevation profiles above were created using Digital Elevation Models (DEM) sourced from the U.S. Geological Survey (USGS). A comparison of topographic profiles across an approximate nine mile cross-section of the mountain details the impact of the eruption event, including the relative size of the crater rim.
The pyroclastic flows of the eruption buried 14 miles of the North Fork Toutle River with debris, as deep as 600 feet in some areas. In the years since 1980, the river has continued to carve out a new braided channel throughout the surrounding valley. The ecosystem of the area has also continued to rebound.
The swipe screen below gives a direction comparison of Mount Saint Helen's surrounding area from 1984 (first image) to 2016 (second image). The pumice plain remains the slowest area to rebound in vegetation; however, it has been observed that prairie lupine (Lupinus lepidus var.lepidus, a native perennial wildflower) has taken root in the area as a primary succession species. The wildflower is uniquely adapted to absorb nutrients from the air instead of soil and begins to support further resilience in the area as it starts to collect soil, insects, herbivores, and organic matter. [13]
Images above are sourced from NASA's Earth Observatory and taken from the Space Shuttle. Photo credits included in reference section.
Images above are sourced from the U.S. Geological Survey (USGS), photo credits included in references section.
Video tour created for UCLA MAGIST Program.
