At 8:32am on May 18, 1980, an earthquake measuring 5.1 on the Richter Scale struck directly below the north slope of Mount St. Helens. In those first few seconds, it probably didn’t seem all that abnormal. After all, it had been earthquakes that first testified to the volcano’s stir from slumber back on the Ides of March. And frankly, there had been thousands and thousands of minor (and not so minor) tremors since then. In fact, the U.S. Geological Survey counted more than 10,000 quakes in that 2-month period.
But, in the time it probably took you to read that paragraph, it became abundantly clear that this wasn’t just “quake number 10,001″. Indeed, the earthquake caused an enormous bubble (shown above), which had been building for more than a month, to break free of St. Helens’ grasp. The ensuing landslide was (and still is) the largest in recorded history, displacing 3.7 billion cubic yards of material, much of which was sliding at more than 100 miles per hour.
The landslide then exposed the magma underneath, releasing the pent-up pressure in a massive explosion. At times approaching the speed the sound and reaching temperatures greather than 650° F, the explosion quickly overtook the slide and mowed down everything in its path.
According to the USGS, ash reached 80,000 feet into the air before falling back to earth to clog rivers, air intake systems in vehicles, and lungs in people and animals. Ash fall was reported as far away as western Minnesota. Fifty-seven deaths resulted from the eruption.
I remember the day very well…actually, I might remember the next day better, because it was the first day I started delivering our local paper, and the photo of the eruption was on the front page. Our family had a subscription to National Geographic magazine, and I recall the big issue that devoted most of its pages to Mount St. Helens and the aftermath. I pored through that issue numerous times. I can even vaguely recall the interviews with Harry Truman, the old man who simply refused to leave the mountain and, after the eruption, was never seen again. A family friend that was a truck-driver brought back a little jar of ash he had picked up in Montana, and it was almost like flour…just a bit grittier. Many of you reading this will likely have memories of your own.
Recommended Reading: Mount St. Helens: The Eruption and Recovery of a Volcano