How many times has Mt St Helens erupted?
How many times has Mt St Helens erupted? Helens has been the most active Cascade Range volcano, with about 20 eruptive periods. Over the millennia, debris avalanches, pyroclastic flows, lava flows, and mudflows have built, torn apart, and rebuilt the volcano. From the May 18, 1980, eruption to 1986, the volcano erupted an additional 21 […]