How do storms and waves create coral reef islands?

Coral reef islands, often called cays, are primarily formed through the process of accretion, where geological material accumulates on the flat tops of coral reefs.12

Storms and waves play a critical role in this development by breaking off rubbly reef rock and coral fragments—particularly from windward slopes—and transporting them across the reef platform. This debris, mixed with finer reef detritus, is deposited where water velocity decreases, typically on the protected leeward side of the reef.13

Over time, these accumulations are stabilized through several mechanisms:
* Cementation: Calcium carbonate from the reef material dissolves in rainwater and is redeposited, cementing the loose debris into solid beach rock.13
* Vegetation: The growth of plants helps bind the sediment and contributes organic matter to soil development.13
* Wind Action: Wind can heap finer material into dunes, raising the island above the high-tide mark.13

While these processes create the islands, they remain unstable; severe storms can both build and destroy these features by eroding shorelines or shifting deposited material.143