Ring of Fire
Mount St. Helens and the Cascade Range are a small part of the Ring of Fire, a zone of intense volcanic and seismic activity that surrounds the Pacific Ocean, stretching from the west coast of South America, northward through Central and North America to Alaska and the Aleutian Islands.
The Ring of Fire continues over to the east coast of Asia (including eastern Siberia and Japan) and encompasses islands in Oceania and the Pacific Ocean as far south as New Zealand.
According to the U.S. Geological Survey (USGS), Mount St. Helens began growing before the end of the Ice Age; its oldest ash deposits date to at least 40,000 years ago. Yet the visible portion of the volcano—the cone—is much younger. Geologist believe it formed over the last 2,200 years.
Mount St. Helens had nine main eruptions prior to the 1980 eruption. Each “pulse” of eruptions lasted less than 100 years to up to 5,000 years, with long intervals of dormancy between them.
Between 1800 and 1857, a large explosion followed by a series of smaller eruptions created the Goat Rocks lava dome, a geologic feature that was later annihilated by the 1980 blast.
A Volcanic Giant Rouses
Modern-day scientists and geologists were concerned about Mount St. Helens years before 1980. Some felt it was the most likely volcano to become active before the end of the twentieth century. They were right.
Beginning on March 16, 1980, a series of thousands of earthquakes and hundreds of steam explosions (known as phreatic explosions) began at Mount St. Helens, causing its outward north side to grow over 260 feet. One earthquake on March 20 measured 4.2 on the Richter Scale, causing snow avalanches but little additional damage.
On March 27, Mount St. Helens emitted at least one booming explosion and spewed a 6,000-foot ash cloud into the sky. The volcano continued to spit ash through the end of April, forming two large craters which eventually merged into one.
Volcanic activity took a brief respite at the end of April but resumed on May 7. As magma from deep within the earth’s crust pushed upward into the volcano, Mount St. Helens changed shape and grew about five feet daily.
Earthquakes and persistent steam explosions continued, and it became clear a massive eruption was inevitable, yet no one knew when.
Earthquakes and Landslides
Early in the morning on Sunday, May 18, 1980, volcanologist David Johnston took measurements of Mount St. Helens from a nearby observation post. There were no red flags to predict the catastrophe about to happen.
At 8:32 Pacific Daylight Time, a magnitude 5.1 earthquake struck one mile under Mount St. Helens, triggering the largest debris landslide in recent history. Johnston managed to radio the information—but sadly, he wouldn’t survive the day.
The debris landslide and mudflows took out the volcano’s summit and bulge and traveled down the North Fork of the Toutle River, filling the basin up to 600 feet in some areas. The USGS estimates the volume of the debris landslide was equal to 1 million Olympic-size swimming pools.
Mount St. Helens Erupts
The debris landslide took the pressure off the volcano’s magma structure, which caused massive lateral explosions and spewed tons of ash, rock, volcanic gas and steam. As the lateral blast accelerated, it reached a velocity of up to 670 miles per hour and covered a 230-square-mile area north of the volcano with searing debris.
It’s estimated the blast reached or surpassed supersonic speed in some areas. Strangely, although the thunderous blast was heard hundreds of miles away, it wasn’t loudly heard in the immediate area around Mount St. Helens, where there was a so-called quiet zone.
The lateral blast tore off the top 1,300 feet of the volcano, leaving a new crater behind. It demolished every tree within a six-mile inner radius and scorched others. It’s estimated that four billion board feet of lumber was destroyed.
The lateral explosion also triggered pyroclastic flows, fast-moving blasts of deadly superheated volcanic gas and pumice.
Ash Cloud Circles the Globe
After the lateral blast, a massive ash cloud mushroomed vertically into the air at least 12 miles, producing lightning and sparking forest fires. The cloud traveled 60 miles per hour and darkened the daylight skies in Spokane, Washington. Intense ash emissions continued until about 5:30 p.m. and began to weaken by the next day.
Over the course of the next two weeks, the giant ash cloud sent roughly 520 million tons of ash eastward over 22,000 miles. The cloud circled the globe several times until the ash finally fell to the earth.
Death and Destruction
The events that took place at Mount St. Helens in 1980 turned the immediate surrounding area into a wasteland, destroying plants, trees and entire ecosystems. Fifty-seven people were killed including volcanologists, loggers, campers and reporters.
Autopsy reports showed most died of thermal burns or from inhaling hot ash. Some people estimate the death toll may be higher and believe many unknown victims were swallowed by the debris flow.
Spirit Lake, a popular tourist attraction near Mount St. Helens, was entombed under tons of debris and mud. Hundreds of homes, cabins and buildings were wiped out or damaged, along with 185 miles of roads and 15 miles of railways.
Wildlife in the area was particularly hard hit. It’s estimated that all birds and small mammals, and up to 7,000 deer, elk, bear and other big game animals, were killed. Local salmon hatcheries were also destroyed. Burrowing animals, however, fared a little better as they were somewhat protected from the scorching elements.
The traveling ash cloud also left behind a wide path of destruction. It destroyed crops, decreased visibility and grounded airplanes. It clogged filters, pumps and other electrical equipment and caused widespread power failures.
Getting rid of the settled ash was a daunting chore that cost millions of dollars and took over two months to complete. Most of the ash was dumped in idle quarries or landfills. Some was stockpiled for future industrial uses.
National Volcanic Monument
In 1982, Congress set aside 110,000 acres of land around Mount St. Helens and within the Gifford Pinchot National Forest for the National Volcanic Monument. The Monument was established for research, recreation and education.
The environment within the Monument has been largely left alone to naturally revive itself. Visitors can view Mount St. Helen’s volcanic crater, lava domes and other landscape changes.
Decades after the 1980 devastation, the National Volcanic Monument is gradually coming back to life. Spirit Lake has been born-again, although it’s shallower than before. Trees and other forest vegetation are growing, and large and small mammals have re-settled the area, along with some bird species, insects and aquatic life.
After salvaging nearly 200 million board feet of dead timber after the 1980 volcanic eruption, the Forest Service planted around ten million trees to reforest thousands of acres of land, most of which are thriving.
Mount St. Helens Today
Mount St. Helens experienced several more blasts in the summer and autumn following the May 1980 eruption. The blasts caused lava to form in the new crater and create new lava domes; however, later blasts obliterated two of those domes.
Over the next several years, 17 additional blasts took place and by 1986 had formed a new lava dome over 820 feet tall and 3,600 feet in diameter.
In September 2004, after a period of inactivity, hundreds of small earthquakes rumbled beneath the lava dome causing magma to start rising to the surface. Steam and ash explosions happened between October 1 and October 5, creating another lava dome which continues to grow and change shape.
In early 2005, the Mount St. Helens experienced several explosions, mostly small. Between 2005 and 2008, the volcano remained active and dumped enough lava onto the crater floor to fill 36,000 Olympic swimming pools. By 2013, two lava domes created from the continual lava flow had filled about seven percent of the original blast crater.
Geologists observed hundreds of small earthquakes beneath Mount St. Helens throughout 2016 and 2017. Since the beginning of 2018, at least 40 earthquakes in the area have occurred; one earthquake registered 3.9 on the Richter Scale. While the earthquakes don’t point to an imminent eruption, they do indicate the volcano is still active and justifies careful monitoring.
Sources
1980 Cataclysmic Eruption. USGS.
2004-2008 Renewed Volcanic Activity. USGS.
About the Forest. USDA Forest Service: Gifford Pinchot National Forest.
Decades After Catastrophic 1980 Eruption, Mount St. Helens is ‘Recharging.” ABC News.
Eruptions of Mount St. Helens: Past, Present, and Future. USGS.
Life Returns: Frequently Asked Questions About Plant and Animal Recovery Following the 1980 Eruption. USDA Forest Service: Mount St. Helens National Volcanic Monument.
St. Helens. Smithsonian Institution National Museum of Natural History Global Volcanism Program.
