Suppose you begin with an island, a volcanic peak in the proverbial middle of the sea. At a certain distance out from the shore, coral begins to grow. If the island begins to subside, the steady growth of the reef would keep the living coral near the surface. In time, the center could disappear altogether, leaving the reef as an islet or atoll. In this way, coral reefs become a lovely demonstration of long-term change due to indiscernible processes.
