Geology
All of the islands of the Tuamotus are coral "low islands": essentially high sand bars built upon coral reefs. Makatea, southwest of the Palliser Islands, is one of three great phosphate rocks in the Pacific Ocean. The others are Banaba in Kiribati, and the island nation of Nauru. Although geographically part of the Tuamotus, the Gambier Islands, at the southeastern extreme of the archipelago, are geologically and culturally distinct.
In the northwest of the archipelago, the ring-shaped atoll Taiaro provides a rare example of a coral reef with a fully enclosed lagoon. The atoll was officially designated as a UNESCO biosphere reserve in 1977.
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