Remember Mount St. Helens, 1980
May 15 • 7:00 pm - 8:00 pm• Free
Where were you on May 18, 1980? If you lived in Oregon, Washington, and even as far as Colorado to the north and east, you have a vivid memory of the powerful explosive eruption that created a large crater, and spread massive clouds of ash over the landscape. Within 15 to 20 seconds of a magnitude 5.1 earthquake at 8:32 a.m., the volcano’s bulge and summit slid away in a huge landslide—the largest on Earth in recorded history. The landslide depressurized the volcano’s magma system, triggering powerful explosions that ripped through the sliding debris. Rocks, ash, volcanic gas, and steam were blasted upward and outward to the north. This lateral blast of hot material accelerated to at least 300 miles per hour, then slowed as the rocks and ash fell to the ground and spread away from the volcano. Several people escaping the blast on its western edge were able to keep ahead of the advancing cloud by driving 65 to 100 miles an hour!**
Joeseph Bard, Geographer with the U. S. Geological Survey, Cascades Volcano Observatory (CVO), Vancouver, Washington, has been at the CVO since 2012 where the main themes of his work include creating digital map products, geospatial analysis, geographic visualization and cartography for the purposes of communicating scientific information about volcanic processes and volcano hazards.
He will discuss the May 18, 1980 eruption of Mount St. Helens and how and why we monitor the volcano currently.
** U.S. Geological Survey Fact Sheet; https://pubs.usgs.gov/fs/2000/fs036-00/