I was with friends trying out a new canoe at Lake Como that Sunday, May 18, 1980. It looked like a huge thunderstorm was coming from the west over the Bitterroots, so we cut the "test float" short and headed back to Hamilton. The storm didn't seem to get any closer; it just got blacker. Back home, on a cable TV channel, I saw a news crawl across the bottom of the screen that Mount St. Helens had erupted. The Weather Service told KLYQ that the ash cloud would drift to the south and miss us. However, at 4 p.m. Hamilton's street lights came on in the thickening grey dust. Another memory of the Washington State volcano eruption 40 years ago was a visit by some of the guys from the Rocky Mountain Laboratories with microscopic visions of the jagged little dust particles that we were breathing in. There was a darn good reason for face masks.

St Helens is a stratovolcano, which is made up of layers of lava and other material from previous eruptions. NOAA's description of the 1980 eruption labeled it "the deadliest and most economically destructive volcanic event in the history of the United States." Of course, The mountain has been around for long time. Its first eruption is estimated 12,000 years ago, with large eruptions in 1800, another in 1855 and five small eruptions in the 20th century, according to NOAA. By the way, there was a small eruption in 2008. The May 18, 1980 eruption killed 57 people, thousands of animals and took out tons of trees. The explosions blew off a bulge on the north face and took off the top 1,000 feet of the mountain. St. Helens is only one of several volcanoes in the Pacific Northwest along the Cascadia Subduction Zone, where deep under the Earth's surface the continental plates are colliding. Other volcanoes you might know - Mt. Baker, Mt. Adams and, of course, Mt. Rainier.