Upper cone of Mount St. Helens before the May 18, 1980 eruption; no...
Although seismic activity began under Mount St. Helens on March 20, this overflight showed no unusual features except numerous tracks of earthquake-triggered snow avalanches. No evidence of fracturing of summit area was detected during careful visual observations on the afternoon of March 24, 1980. On March 25, the first cracks were noted by Bud Kimball, Tacoma, Washington.".