High mountainous areas pass through freezing many days during a year. Strong rays of the sun will warm any exposed rock even in winter and casue small amounts of ice to melt. Water will seep into the cracks and then freeze when the sun sets or is covered by clouds. Freezing temperatures are also reached at night in the middle of summer. This photo at Beartooth Pass in Montana (elev. = 12000 ft.) was taken in July. The jumble of rocks has been produced by freeze-thaw acting on a small peak near the pass the pass.
Here a grante boulder in the Sierra Nevada Mts. of CA has been cracked by the action of water and ice.
Physical weathering also occurs when rocks are
rolled by moving water in streams or along the coast. These rocks have
been washed back and forth by waves grinding out a pot hole along the
coast of Nova Scotia. The rocks have also been rounded and broken by
the wash of the waves.
Breakage can also occur
during a landslide triggered by an earthquake like this one near Hebgen
Dam in SW Montana.