A beach is geographically defined as an area of land covered with shingle, small rocks, and sand positioned along the edge of a body of water, like a lake, ocean, or river. Formed mainly by weathering and erosion, it begins when tides travel to shore, carrying sediments of rocks, shells, and sand along with it. Eventually washing the sediment mixture onto coastlines. Sand forms from eroded rocks in rocky reefs, and nearby cliffs creating sand dunes on beaches.