In April of 2016, the United States Geologic Survey (USGS) stated that a large number of small earthquakes were reported around Mount St. Helens. The swarm of tremors, over 130 of them, had magnitudes of 0.5 or less. The tremors have been increasing since March, but, they were so small and about 1 to 4 miles deep, no one could feel those small quakes even if they were standing directly on the surface directly above them.
There is a correlation between earthquakes and volcanic eruptions. When Mt. St. Helens erupted on May 18, 1980, it began with a magnitude 5.1 earthquake preceded by thousands of smaller quakes. More than 1,000 feet was blown off from the top of the mountain that left a huge crater. The eruption was the deadliest and most expensive volcanic eruption in U.S. history. The event killed 57 people, led a number of forest fires and widespread mudflows due to the melted snow from the mountain.
Prior to the big 1980 eruption, the USGS noticed a huge 450 foot bulge in the mountains northernmost flank. It was expanding at a rate of 6.5 feet per day and volcanologists soon realized that an eruption was imminent.
Despite the recent increase in earthquake activity, scientists at the USGS don’t anticipate a new eruption anytime soon. The new round of earthquake swarms around Mount St. Helens is not new. In the late 1990s, there were more energetic swarms with another series occurring in 2013 and in 2014.
There’s no question that the volcano is still very active as volcanologists believe that the magma chambers are slowly recharging. As I mentioned in an article last month, Mount St. Helens and other volcanoes like Mt. Rainier, Mt. Hood and others, lie within a region of high earthquake and volcanic activity that stretches approximately 25,000 miles called the “Ring of Fire.” This area that looks like a horseshoe which extends from New Zealand, Indonesia, Japan, southern Alaska and along the U.S., Central American and South American West Coasts.
The Pacific “Ring of Fire” is the result of the movement and collisions of the tectonic plates that have led to the creation of over 450 volcanoes, especially along the U.S. West Coast.
At least several years after the eruption, I remember taking a trip to Seattle. While on the plane, the pilot would tell everyone in the cabin that he was taking the plane very close to Mount St. Helens. Many passengers would actually jump from their seats and go to the side of the aircraft to get the best view. I thought it was kind of cool at the time, but I don’t believe we would see a repeat of passengers all jumping to one side of the plane for a photo opportunity of Mount St. Helens or any other feature.