Coral islands

From GeoClasses

Coral barrier reefs surrounding Raiatea (lower) and Tahaa (upper) lie in the Society Islands of the South Pacific between Tahiti and Bora-Bora.

In tropical oceans where corals can survive in the warm ocean waters, coral reef can form a fringe around the island.

A barrier reef protects both islands and their shared lagoon from the large swells of the open ocean. These swells break and expend their energy along the fore reef and reef crest, and the resulting bubbles show up as a white outline in this Landsat-7 image. The white carbonate sediments of the back reef zone appear as a turquoise band because the overlying shallow water absorbs more red than blue of the incoming sunlight before it is reflected back to space. - from NASA

Coral reef viewed from the beach on Fiji.

The barrier reef protects the shore from the force of the waves. Note the line of breakers in the distance of this image.