On the clear morning of May 18, 1980, the active stratovolcano Mt. St. Helens erupted in a violent fury that became the deadliest and most economically destructive volcanic event in United States history. 57 people were killed. 250 homes, 47 bridges, 185 miles of highway, and 15 miles of railroads were destroyed. In 1982, 110,000 acres around the volcano and within Gifford Pinchot National Forest was set aside as Mt. St. Helens National Volcanic Monument to preserve the volcano and allow its aftermath to be studied scientifically.
On that fateful morning, an earthquake measuring 5.1 on the Richter Scale caused a massive debris avalanche that slid down the mountain at 180 miles per hour. The avalanche still had enough momentum to flow over a thousand-foot ridge 4 miles away from the volcano. The avalanche covered 24 square miles and advanced down the North Fork of the Toutle river over 13 miles at an average depth of 150 feet. The debris filled Spirit Lake (shown above), raised its bottom by nearly 300 feet and the water level by another 200 feet. 32 years later, Spirit Lake is still filled with tree trunks that were swept off the volcano in the avalanche.
Within a few seconds of the debris avalanche, the weakened north flank of the volcano triggered a massive lateral blast similar to popping the top of a shaken soda can. Rock, ash and hot gas blasted sideways at speeds up to 670 miles per hour, quickly overtaking the debris avalanche. The devastation extended up to 19 miles away and covered 230 square miles. The innermost “direct blast” or “tree down” zone obliterated nearly everything up to 8 miles from the volcano (top photo). The outer “seared” or “standing dead” zone is where trees remained standing but had their foliage and branches blown or burned off (bottom photo).
Plants and trees within the national monument were left untouched and allowed to recover at the natural rate. 32 years later some vegetation and trees have started to take hold. While we were there, the autumn wildflowers were blooming, and the fireweed stalks had turned a pretty red. Outside the monument and in the surrounding national forest, many trees were replanted, and the forest was thick and lush.
Three days before the eruption, Donald and Natalie Parker and their nephew Rick parked their green 1972 Pontiac Grand Prix about 8-1/2 miles from the volcano and hiked to a nearby cabin to inspect their mining claim. They were in the designated “blue zone,” which was open to businesspeople who signed liability wavers with the state, which the Parkers did. Volcano scientists were not as worried about people in the blue zone because they were expected to survive a typical vertical eruption. But the initial eruption of Mt. St. Helens was lateral (sideways) not vertical. The blast killed the Parkers and flattened and seared their car, which remains as a stark reminder to the 57 people who perished that day.
Mt. St. Helens is located in the Cascade Volcanic Arc, a segment of the Pacific Ring of Fire that includes over 160 active volcanoes. From Mt. St. Helens we could see two other active stratovolcanoes: Mt. Rainier (top) and Mt. Adams (bottom). Mt. Rainier is considered the most dangerous active volcano in the United States due to its proximity to Seattle and its potential for pyroclastic flows. Mt. Adams has not erupted in 1400 years but is still volcanically active.
Lava Canyon’s beauty was hidden beneath an evergreen forest until the 1980 eruption sheared 30 feet of ice off the top of Shoestring Glacier on the side of Mt. St. Helens. A 15-foot wall of ice and mud shot down the canyon, scoured the canyon walls, and exposed a series of beautiful waterfalls and rock formations. There is a swinging suspension bridge across the canyon. (The tiny dots in the top photo are people crossing the bridge. In the bottom photo, Theresa and Shadow are crossing the bridge.) The bridge stands over 100 feet above the canyon floor, and there is a space between each wood slat in the floor, so it can be a bit nerve-wracking to cross the bridge, especially for dogs. But our dogs are (mostly) fearless!
Here is a pretty double-waterfall, one of many waterfalls in Lava Canyon.
The 2-mile-long Ape Cave is the longest lava tube in the continental USA. A lava tube is formed when thick lava develops a hard crust roof above a still-flowing lava stream. Eventually the lava stream drains out, forming a tube or cave-like structure. The top photo shows the “Railroad Tracks” that resulted when a shoulder developed along the edges of the shallow lava stream. The middle photo shows the odd flow stalactites formed by dripping lava. The bottom photo shows the famous “Meatball,” a block of lava that fell from the ceiling while lava was still flowing through the tube.
A tree mold is made when lava flows around a tree. The lava cools when it comes in contact with the tree, forming a mold around the trunk. Fire from the heat of the lava burns through the tree and causes it to topple over and die. Over time, weather erodes away the burned tree to reveal the tree mold.
Theresa crawled through “The Crawl,” a small lava tube.
Mt. St. Helens started erupting about 40,000 years ago and has been erupting ever since. Though it has gone through periods of dormancy, it has been quite active for the past 4,000 years. It had a minor eruption as recently as 2008, though another major eruption is not expected within our lifetimes. In the photo above, we hiked to the southern edge of the restricted zone, where civilians are not allowed without a permit.
We dispersed camped just a few miles south of Mt. St. Helens with a great view of the volcano. Had we been camping here on May 18, 1980, we would have survived the eruption, but our RV would have been blanketed with up to 6 inches of volcanic ash. We also would not have heard the explosion. An odd “cone of silence” extended outward about 60 miles from the volcano. None of the eruption victims or survivors heard the blast, yet people nearly 600 miles away heard a loud bang.
The 1980 eruption blew 1,300 feet of rock off the top of the mountain and created a 1-mile wide horseshoe crater (visible in the very top photo). Then-President Jimmy Carter surveyed the damage and said, “Someone said this area looked like a moonscape. But the moon looks more like a golf course compared to what’s up there.” Today, the monument is a study in the explosive power of nature and its ability to recover from complete devastation.