Mark Wilson July 17th, 2010
DOWNEY, IDAHO–Lake Bonneville has been one of the geological themes of my short visit to northern Utah this summer. The remnant wave-cut platforms of its shorelines dominate the geomorphology of the Logan area, and the lake sediments are the basis for the rich soils of the Cache Valley. Today my parents and I visited Red Rock Pass in southern Idaho where this massive lake breached a weak area of limestones and shales 14,500 years ago and then catastrophically flooded the land to the north. The Bonneville Flood was not as large as the Missoula Floods of geological legend, but it left a very similar record of scoured land, scattered boulders, huge waterfalls, and thick gravel bars.