A tombolo is a landform that connects an island to the mainland or another island through a narrow strip of land, often made of sand or gravel. This formation occurs due to the accumulation of sediment, which is shaped by the action of waves and currents. Tombolos typically form in coastal areas where the conditions are right, such as calm waters and a steady supply of sediment. A well-known example of a tombolo is the Chesil Beach in Dorset, England, which connects the island of Portland to the mainland.