Marcie Sillman talks to Carolyn Driedger, a hydrologist and outreach coordinator for the U.S. Geological Survey, about what volcanologists have learned since Mount St. Helen's erupted 35 years ago and what other risks we face from Northwest volcanos.
Lessons From Mount St. Helen's 35 Years Later
Flickr Photo/Washington DNR (CC-BY-NC-ND)
