A sequence of images shows Mount St. Helens before, during, and after its eruption on May 18, 1980. The massive eruption blew the top 1,300 feet off the top of the mountain. It was one of the most powerful and destructive volcanic eruptions in American history. The image at left shows the mountain the day before the eruption, while the image at right shows a smaller outburst, in 1980. [USGS (3)]