10. 9 NOTES
What are coral reefs?
Objective: Describe three kinds of coral reefs
Tiny animals called coral live in warm, shallow ocean waters. The coral absorb
calcium from the water and use it to make hard skeletons of limestone, or calcium
carbonate. Coral often attach themselves to other coral, forming a colony. New
coral grow on top of dead ones, forming a coral reef.
Two kinds of coral reefs are fringing reefs and barrier reefs.
A fringing reef is directly attached to a shore, and borders the coastline.
Barrier reefs form around sunken volcanic islands and at one time extended out
from shore. When the island sank, the reef separated from the mainland by a
body of water called a lagoon. The Great Barrier Reef in Australia is the world’s
largest barrier reef. It is more than 2000 km long and almost 200 km wide.
A ring-shaped coral reef around a lagoon is called an atoll. An atoll forms around
a sunken volcanic island. In the center of the atoll is the lagoon. Most atolls are
found in the Pacific Ocean.