Coral Reefs, Emerged

Corals and other reef-building organisms such as algae live within the photic zone, rarely deeper than 100 m and are limited upwards by intertidal exposure. However, well-preserved reefs emerged up to hundreds of meters above modern sea level are found in many parts of the world. All types of reefs are found emerged although the most common are fringing reefs occurring as terraces built over volcanic or other non-carbonate foundations (Fig. 1). Emerged barrier reefs appear to be rare, even in Indonesia which has both extensive, modern barrier reefs and numerous emerged fringing reefs (Tomascik et al. 1997). However, a section of the very long (2,000 km) Papua New Guinea barrier reef is emerged in Sabari Island (Fig. 2) to the north of the Louisiade Islands, and in the Trobriand and Lusancay Islands to the north. Many emerged atolls occur in the Pacific (e.g., Henderson, Makatea, Mataiva, Nauru, Walpole) and in Indonesia (Maratua, Kakaban). Detailed descriptions of the geology and...