Glaciers can also pluck or lift large chunks of rock. These rocks are then frozen into the glacier and also abrade the rock over which the glacier travels. Mountain glaciers create U-shaped valleys by plucking and scouring. To learn more about glaciers, check out the glacier knowledge center in Views of the National Parks. Glaciers never existed in or near Grand Canyon, however they have existed and may still exist today in other National Parks. Many examples of U-shaped glacial valleys can be seen in the National Parks, such as Yosemite National Park in California.