The Ice Age Floods National Geologic Trail is a network of routes connecting natural sites and facilities that provide interpretation of the geological consequences of the Glacial Lake Missoula floods
Glacial Lake Columbia (west) and Glacial Lake Missoula (east) are shown south of the Cordilleran Ice Sheet. The areas inundated in the Columbia and Missoula floods are shown in red.
Glacial Lake Missoula high-water mark, 4200 ft.
Illustration of the glacial flows leading to formation of several parts of the trail
Moses Coulee at mid canyon
Lake Lewis
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Lake Lewis was a large transient lake in the Pacific Northwest region of North America, formed by periodic Missoula Floods along the Columbia River paleocourse between 21,000 and 16,000 years ago.
This figure shows four profiles of Lake Lewis at various flood levels. It illustrates that the lake back flooded several valleys in which the Touchet Beds were found.
Looking to the West across the Wallula Gap.
Touchet beds in the "Little Grand Canyon" near Lowden in the Walla Walla valley. Note distinct layers.
Cluster of erratics on Red Mountain shown in the foreground; these were trapped in glacial ice and "rafted in" on the flood of Lake Lewis. In the background the native basalt, which covers the rest of the mountain ridge, is visible.