When a powerful earthquake on May 18, 1980 triggered the colossal volcano explosion on Mount St. Helens, the explosion wiped out every object within a radius of ten kilometers. It remains the most powerful and fifth-most destructive volcanic event in the world in recent history. Here you can find more facts about the 40th anniversary of the eruption of Mount St. Helens.
1. Mount St. Helens is part of the Pacific Ring of Fire.
Mount St. Helens is part of the chain of 160 active volcanoes around the Pacific Rim known as the Ring of Fire. It is located on the subduction zone in which the tectonic plate of the oceanic Juan de Fuca slides under the North American plate. It is a stratovolcano, also known as a compound volcano: a steep volcano with a cone made up of layers of lava, ash and debris. Stratovolcanoes are considered more dangerous than shield volcanoes, which arise from slow lava flows and have gentler slopes. (The Hawaiian Islands are a chain of shield volcanoes.) Stratovolcanoes tend to explode, and their steep sides are prone to landslides, avalanches, and sometimes even collapse.
2. Mount St. Helens was named after a British diplomat.
Mount St. Helens is not named after a saint ̵
3. Mount St. Helens has been erupting for a long, long time.
Mount St. Helens has undergone a series of eruptions throughout its life that began 275,000 years ago. This is relatively young for a volcano – a number of volcanoes formed by the Hawaiian hot spot are tens of millions of years old. However, volcanoes change drastically over the course of their lifespan: According to the US Geological Survey, the majority of the modern Mount St. Helens cone that is visible has formed over the past 3000 years.
4. Mount St. Helens is the most active volcano in the Cascade Range.
Mount Baker, Mount Shasta, Mount Rainier, Mount Hood, Glacier Peak, and Lassen Peak are also active volcanoes in the Cascades, but recent activity among them was at Lassen Peak in the early 1900s. Mount St. Helens is also the youngest of the Cascade volcanoes, which is why it shows fewer signs of erosion than neighbors like Mount Rainier or Mount Hood.
5. The catastrophic explosion of Mount St. Helens in 1980 was the first major eruption in the volcano in more than 100 years.
Before 1980, the last major explosive eruption of Mount St. Helens occurred in 1800. There were several minor explosions from the early 19th century to 1857 when the volcano stopped. This period of volcanic activity created the so-called Goat Rocks Dome, which was part of the characteristic silhouette of Mount St. Helens until it was destroyed in the 1980 eruption.
6. The eruption of Mount St. Helens in 1980 is still the strongest volcanic eruption in the history of the United States.
On the morning of May 18, 1980, a 5.1 magnitude earthquake in the north caused a massive landslide – the largest avalanche of ruins in the face of Mount St. Helens. In the subsequent volcanic eruption, the side explosion destroyed every living and non-living thing within six miles of the volcano. The deadly pyroclastic wave – a fast-moving, super-hot cloud of ash, rock, and volcanic gas – was up to 18 miles from the explosion. The hot lava, gas, and debris mingled with melting snow and ice, forming massive volcanic mud flows that entered valleys with enough force to tear trees off the ground, plate houses, and completely destroy roads and bridges. Rivers rose quickly and flooded the surrounding valleys. Ash fell from the sky to the Great Plains. Ash covered Spokane, Washington, two hundred and fifty miles away in complete darkness.
7. A Mount St. Helens volcanologist has probably saved hundreds of lives.
Fifty-seven people died as a result of the outbreak, although the number could have been much higher. Volcanologist David Johnston was in favor of restricting access to the volcano when an increase in seismic activity in early 1980 signaled that an eruption could be imminent. Johnston died when the observation post from which he monitored Mount St. Helens was destroyed. "The efforts to monitor the volcano, in which Dave was involved, have helped to persuade the authorities to first restrict access to the area around the volcano and then to resist the intense pressure to reopen it, reducing the number the death toll on May 18 was limited to a few tens instead of hundreds, or thousands, ”said the authors of the 1982 US Geological Survey report on the disaster.
8. The eruption changed the appearance of Mount St. Helens forever.
Before the 1980 eruption, Mount St. Helens had a symmetrical, snow-covered cone that gave it the nickname "Mount Fuji of America". The summit was 9677 feet high. The side explosion, however, changed its appearance significantly: the top 1300 feet of the summit were destroyed by the eruption and landslide. Now the volcano has a north-facing, horseshoe-shaped crater that contains a lava dome and a glacier.
9. Mount St. Helens was converted into a national volcanic monument in 1982.
Two years after the devastating eruption, Congress transformed the area around Mount St. Helens into a 110,000 acre national volcanic monument for research and recreation. It is located in the Gifford Pinchot National Forest and is managed by the U.S. Forest Service. Visitors can hike, camp, fish and much more. However, hikers need a special permit to climb the summit. (This is of course not allowed if the volcano has unusually high activity.) You can also visit the Johnston Ridge volcano observatory and the Ape Cave, a lava tube that was formed almost 2000 years ago.
10. Mount St. Helens has shrunk.
In a 1982 investigation, the volcano's summit was measured at 8,365 feet. As of 2009, it measured 8,330 feet. The shrinkage is likely the result of erosion and collapse of the crater walls.
11. The eruption of Mount St. Helens is not yet complete.
The United States Geological Survey still rates the potential threat to Mount St. Helens as "very high" due to the eruption potential and the number of nearby communities affected by these outbreaks. The volcano is just over 80 km from Portland, Oregon, and less than 100 km from Seattle. The 1980 eruption destroyed all of the buildings around the nearby tourist destination Spirit Lake, including more than 200 houses and cottages. The most recent volcanic activity on Mount St. Helens was from 2004 to 2008, when the volcano added a new lava dome and released steam and ash clouds regularly. There were few significant explosions before volcanic activity ceased in 2008.
While the US Geological Survey warns that Mount St. Helens is likely to explode again during our lifetime, the agency predicts an explosion of the magnitude of the 1980 eruption is unlikely. However, scientists from the U.S. Geological Survey Cascades Volcano Observatory and the Pacific Northwest Seismic Network carefully monitor seismic data, gas emissions, surface changes, and other factors around Mount St. Helens to predict possible volcanic activity.