David Koch, age 14, of San Diego, Calif., for his question:
HOW ARE CORAL REEFS FORMED?
Coral reefs look like beautiful sea gardens because of the many colorful sea animals that live among the corals. You'll find fishes, starfish, mollusks and sea anemones. Coral masses sometimes build up until they rise above the water to actually form a coral island. The grinding, battering sea helps to build the islands. Many Pacific islands were formed this way.
A coral is a limestone growth formed by the sea and millions of tiny animals. Coral formations can look like branching trees or domes. Living coral forming animals color the formations green, orange, yellow, tan and purple. When the animals die, they leave the limestone skeletons that form the foundations of barriers and ridges in the sea called coral reefs.
Coral reefs are found in warm and tropical seas because most coral forming animals cannot live in water that is below 65 degrees Fahrenheit. You'll find reefs throughout the South Pacific, in the East Indies and the Indian Ocean to Sri Lanka, and around Madagascar on the southeastern Africa coast. In addition, coral reefs can be found along the Florida coast, at Bermuda, throughout the West Indies and along the tropical eastern coast of Brazil.
There are three types of coral reefs: fringing reefs, barrier reefs and atolls.
Fringing reefs are platforms of living coral animals that extend from the shore out into the sea. They are usually submerged just below the surface of the water.
Barrier reefs can be found along the shoreline but are separated from the land by water. They actually form a barrier between the open sea and the land. The Great Barrier Reef of Australia is more than 1,250 miles long and is considered to be the most magnificent coral reef in the world. The reef is separated by many channels to the open water.
An atoll is a ring shaped coral island in the open sea. It forms when coral builds up on a submerged mudbank or on the rim of the crater of a sunken volcano. The atoll often surrounds a body of water called a lagoon. One or more channels usually connect the lagoon with the open sea. Many islands of this type can be found in the South Pacific Ocean.
Coral reefs do not develop on the East Coast of North America north of Florida and Bermuda. However, you will find small patches of coral growth as far north as New England. Certain types of coral even grow as far north as the Arctic Cirr1e.
The animals that form coral belong to the same family as jellyfish and sea anemones. Most individualcoral animals, called polyps, are less than an inch long, although some extend to a foot in length. The creature has a cylinder shaped body with a mouth at one end which is surrounded by tiny tentacles. The other end of the animal attaches to hard surfaces on the ocean floor. They live in colonies.