Good illustration of "ash fountain" after Mount St. Helen July 22, 1980 eruption. Skamania County, Washington.

Typed caption accompanying slides: Approximately 3 seconds after slide no. 11. Good illustration of "ash fountain" feeding material into the advancing pyroclastic flow. Skamania County, Washington. (Tip of wing of aircraft visible) (Photo by J. Valance) Note: Mount St. Helens - List of color transparencies (slides) of the July 22, 1980 eruption. The following slides (1-114) of the July 22, 1980 eruption of Mount St. Helens were taken by Jim Vallance, who was in a U.S. Forest Service fixed wing aircraft and by Mike Doukas, Harry Glicken and Rick Hoblitt, who were in a U.S. Geological Survey helicopter. There were three major eruptive pulses on July 22, 1980. They began at 17:14, 18:30 and 19:02 PDT. Additional note: Slides no. [...]