THREE KINDS OF REEFS

There are three kinds of coral reefs: fringing reefs, barrier reefs, and atolls. All three kinds grow in warm places. Coral reefs cannot form in water colder than about 68° Fahrenheit (about 20° Celsius). Reefs form in clear, shallow water. They need sunlight in order for plants and animals to live there.
Fringing reefs are close to shore. There is no lagoon or other body of water between a fringing reef and the shore. Barrier reefs are farther out in the ocean. There is usually a lagoon between a barrier reef and the shore. Barrier reefs can be huge. The largest group of reefs in the world is Australia’s Great Barrier Reef. It covers thousands of square kilometers. Atolls are really the tops of volcanoes that sank below the sea. The reef grows on the rim of the volcano. Inside the reef is a lagoon.