During and before the Pleistocene, the upper portion of the watershed was heavily glaciated during successive ice ages, with valley glaciers flowing as much as down the river's three forks, carving the V-shaped river canyons into the U-shaped gorges of Kings Canyon, Tehipite Valley and others. The Sierra is composed mainly of granitic igneous rock; however, in the foothill area the Kings River flows through roof pendant formations of older sedimentary and metamorphic rock which were accreted to the Sierra Nevada crustal block as it rose above the surrounding landscape.: