The Clearwaters are formed mostly of Idaho Batholith granite, covered in places by scattered deposits of older sedimentary and metamorphic rocks that have yet to erode away. During the Pleistocene ice age alpine glaciers carved cirques and lake basins into the sides of higher Clearwater peaks. The effects of the glaciers are most readily visible in the Mallard-Larkins and Selway Crags areas of the range. Although the Clearwater terrain is somewhat uniform in its overall appearance, several distinct ridges within the range have been singled out by topographers as subranges. These include the Selway Crags, the Moose Mountains, the Sheep Mountain Range, and the Little Goat Mountains.