Water creates, shapes, and destroys rocks as it cycles among land, sea, and air. When a river like the Mississippi dumps sediment into the sea, sand and clay settle in layers on the bottom, where they slowly turn into sandstone and shale. Meanwhile, the ocean water steadily evaporates into the atmosphere...then falls as rain or snow...which replenishes groundwater and the river...whose erosive energy carves away rock...creating new sediments that the river transports to the sea.....completing the cycle.