The weathering caused by rain water, ice, and the wave action of the sea at the base of cliffs, all require water. The rain water seeps into cracks in the rocks. When the water freezes, the ice expands and forces the cracks wider, even splitting off large portions of the original rock. Then there is the constant wave action of the sea at high tide (especially on spring tides and during a storm) against the base of cliffs, picking up large boulders to hammer at the cliff face, then grinding the fallen rocks until they become rounded pebbles, and then shingle on a beach - even becoming grains of sand.