Strong waves erode and deposit material on shorelines over time, forming various landforms. These include sea cliffs created as wave-induced cracks in rock expand and break off pieces. Sea caves are also formed as weaker rocks are carved out by wave erosion. When erosion joins cracks close to each other, sea arches form. Further erosion can cause arch roofs to collapse, leaving behind stacks. Beaches are landforms created through the temporary deposition of sand and soil by wave action.