On March 27, 1980 St. Helens suddenly began to erupt steam and ash. These eruptions continued sporadically for the next seven weeks and Dr. Easterbrook made frequent flights to the mountain to observe the eruptive activity. On May 18, 1980, he flew to St Helens at 5:30 a.m. and flew in tight circles a few hundred feet above the summit crater for 2-1/2 hours, photographing the summit crater and bulging north flank of the mountain. St. Helens was unusually quiet, so a little after8:00 a.m. he headed back to Seattle. About 20 minutes later(8:32 a.m.), the plane experienced a severe jolt when St Helens violently exploded. Shortly thereafter, he flew back to the mountain and photographed the eruptive activity for several hours. In the years following the explosion, Dr. Easterbrook made many flights to St Helens and conducted research from helicopters and on the ground under an NSF research grant. This book is an account of the pre-explosion eruptions, theMay 18 explosion, and the post-May 18 eruptive activity. It contains 149 photos and maps of the eruptions.