What forms when a spit grows to connect the mainland with a near-shore island?

A tombolo forms when a spit extends to connect the mainland to an offshore island, creating a land bridge. This geographic feature results from the accumulation of sediment as waves and currents transport materials along the coast. The spit acts as a barrier that slows down water movement, allowing sediment to settle and grow, eventually linking the island with the mainland. This phenomenon illustrates the dynamic nature of coastal processes, showcasing how sediment transport and deposition can significantly alter coastlines over time.

In contrast, an estuary is a partially enclosed coastal body of water where fresh and saltwater mix, typically located between rivers and seas. A baymouth bar is a barrier that forms across the mouth of a bay, which can occur due to similar sedimentary processes but does not link to an offshore island. Lastly, a spit is a narrow landform extending from the coast into a body of water, but on its own does not create a connection to an island like a tombolo does.