Most coral reefs were formed after the Last Glacial Period when melting ice caused sea level to rise and flood continental shelves. … See more

Coral reef ecosystems contain distinct zones that host different kinds of habitats. Usually, three major zones are recognized: the fore reef, reef crest, and the back reef (frequently referred to as the reef lagoon).
The three zones … See more

When alive, corals are colonies of small animals embedded in calcium carbonate shells. Coral heads consist of accumulations of individual animals called polyps, arranged in diverse shapes. Polyps are usually tiny, but they can range in size from a … See more

In The Structure and Distribution of Coral Reefs, published in 1842, Darwin described how coral reefs were found in some tropical areas but not others, with no obvious cause. The … See more

Since Darwin's identification of the three classical reef formations – the fringing reef around a volcanic island becoming a barrier reef and then an atoll – scientists have identified further reef types. While some sources find only three, Thomas lists "Four major forms … See more

Coral reefs are estimated to cover 284,300 km (109,800 sq mi), just under 0.1% of the oceans' surface area. The Indo-Pacific region (including the See more

Corals are the most prodigious reef-builders. However many other organisms living in the reef community contribute skeletal calcium carbonate in the same manner as corals. … See more