“The mountain altitude (at the dam the elevation is 6,550 ft.), presented aviation difficulties, too. Smaller helicopters couldn’t make it, and some of the bigger jobs were tricky to fly in the less dense mountain air. “We had difficulty with aerial sightseers. In spite of our announcement that the fields at West Yellowstone and Ennis were closed to all but emergency aircraft, planes flew in from all over. Charter pilots flew in from as far away as Arizona, and did a brisk business in flying the curious over the quake area at $6 a head. Including the Air Force ships, during the first few days the West Yellowstone Airport was as busy as Chicago’s Midway Field, with planes taking off and landing at the rate of one a minute. With all the traffic over the slide area, it was a miracle that we got through that first week without a crash. [Illustration: Fallen trees.] “But as a result of the quake we know that any area which has this kind of emergency will make out OK with the wonderful spirit of people, helping and wanting to help.” AFTERMATH Among the cataclysms of nature, none is more terrifying than an earthquake, and huge slides, like the one triggered by the Madison Canyon earthquake, are perhaps the most dramatic type of geologic change. In one sudden, spectacular moment, changes take place that make us think of the tremendous energy released by atomic fission, the earth’s mass moves in a volume that rocks the imagination, and its effect on the people who are near, or in the path of nature’s huge, impulsive-seeming change helps us to realize how infinitesimal we are before the forces and laws of nature. In 1903, a 40 million cubic yard rock slide crashed down from the crest of Turtle Mountain onto the coal-mining town of Frank, Alberta, killing 70 people. But the consequences of such huge slides aren’t completed when the cliff toppling ceases. Take the case of the famous June 23, 1925, Gros Ventre slide in northwestern Wyoming, 40 miles south of Yellowstone Park. An estimated 50 million cubic yards of rock and debris plunged down the steep canyon wall, shot across the valley floor, and rushed some 350 feet up the opposite wall of the canyon before it settled back, like water sloshing in a huge bowl. Nobody was killed when this slide choked the Gros Ventre River. It covered parts of two ranches and buried six head of cattle. But two years later, in May, 1927, the water dammed by the slide pushed out a big section of the slide and the sudden wave of water and debris washed away the town of Kelly, Wyoming, killing seven people. This kind of possibility was in the mind of Army Corps of Engineers Missouri River Chief Keith R. Barney as he and Lt. Col. Walter W. Holgrefe of the Corps district offices at Garrison Dam in North Dakota, discussed the Montana earthquake’s action. The slide represented a double threat to people in the Madison Valley below.