It is worthwhile to remember that coral reefs are almost entirely confined to the tropical seas in a zone between 30° N and 30°S, latitudes. However, within this zone from lat. 30°N and 30°S, true coral reefs are not found on the western shores of the continents.

In this zone of the trade winds, the western side of the continents is in fact the leeward side characterized by an upwelling of cold water from the bottom of the oceans and the seas. Even though masses of coral may be present but they do not build true and typical reefs on the western coast of North or South America, Africa, or Australia.

On the contrary, on the eastern shores of all these continents there are certain areas with typical coral reefs. However, the upwelling of cold water cannot be the sole cause of the absence of coral reefs on the west coast of the continents, because in the vicinity of the equator even on these shores the water is warm enough for the corals to thrive.

Let us remember that coral reefs form around the edges of continents and around the shores of large islands and of volcanic peaks. Coral reefs are most widespread in the western and central Pacific Ocean.

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They are also found in the tropical zone of the Indian Ocean, as in the Laccadives and Maldives, the Andamans, Seychelles and Mauritius. Besides, coral reefs in the Atlantic Ocean are entirely confined to the West Indies. They are also found off the coast of Brazil. In the mid-Atlantic only the Bermudas are encircled by coral reefs.

The largest of all coral reefs are the Great Barrier Reefs of Australia which are found along the coast of Queensland for more than 1600 km.