Geology and Ice Age Floods
Granite, basalt, and large coulees make the complex puzzle that is Lake Roosevelt.
Ice Age Floods National Geologic Trail
At the end of the last Ice Age, great floods crashed through the landscape, sculpting the northwestern United States.
Fish inhabiting Lake Roosevelt continue to adapt to an altered environment: dams have stopped salmon and sturgeon runs, the lake's depth fluctuates seasonally because of snowmelt runoff, the water temperature varies at different locations, and human-introduced species like kokanee and walleye compete with native fish populations for food and habitat.
Last updated: April 17, 2023