The trees to a level of about 50 feet above the present surface of Earthquake lake were once inundated for about 30 days while the Corps of Engineers constructed a new spillway across the Madison slide. The water was then let down to its present level. During this time the trees below the water level died and the water mark is clearly visible as a dark gray line. Small longitudinal step fault scarps formed along the trace of Hebgen fault. View is northward, and these small step faults are along the south flank of Mount Hebgen, about half a mile northeast of Hebgen Dam.
All scarps are in colluvium.
Gallatin County, Montana. Earthquake Lake showing both its present level, and its former level marked by a zone of dead needles. Partly submerged house still shows in center. Photos from the Earth Science Photographs from the U.S. Geological Survey Library , by Joseph K. McGregor and Carl Abston, U.S. Geological Survey Digital Data Series DDS-21, 1995.