Natural Features & Ecosystems

Geology and Ice Age Floods

 

 

Lake Roosevelt National Recreation Area spans three distinct geologic provinces: the Okanogan Highlands, the Kootenay Arc, and the Columbia Plateau. The landscape has been shaped by gradual forces of uplift and erosion, and by sudden cataclysmic events. Over millions of years, intermittent lava flows created the Columbia Basin. Tectonic action later uplifted these volcanic basalt layers. The Cascade Mountains rose and created a rain shadow, reducing the amount of precipitation in the Columbia Basin and Okanogan highlands. During the last Ice Age, a series of massive floods scoured the coulees and created the channels scablands.

 

Ecosystems

 

 

Lake Roosevelt marks a transition zone between the desert-like Columbia Basin to the south and the slightly wetter Okanogan Highland to the north.

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.

Much of the shoreline around Lake Roosevelt supports conifer forests, grasslands, and scrublands that provide habitat for an estimated 75 species of mammals, 200 species of birds, 15 species of reptiles and 10 species of amphibians.

The area's plant and animal species have changed and continue to change overtime, adapting to climate transitions that vary from location to location.