What is meant By Coral Reef?
First of all, we must understand the exact meaning of coral. A chunk of coral comes into existence from the skeletons of tiny marine animals known as coral polyps.
In fact, the skeleton of polyp generally grows outside its body. When we look at a glance, it is cup-shaped and moreover it also helps in protecting and supporting the polyp’s body and have the tendency to grow as the animal grows. Only the skeleton is left when the polyp dies. Hence, coral reefs and islands are formed in multi-billions of these tiny skeletons.
Coral colonies consist of living corals and are generally found more or less in all seas. Each coral colony is attached to a solid base e.g. a rock or the skeletons of earlier generations of corals.As far as reef-building coral polyps are concerned, they are found wily in warm, shallow waters. It is observed that the water level hear about 150 feet is considered to be the most suitable for them. It is noticed that in certain cases, coral reefs rise from great ocean depths in different parts of the world.
Charles Darwin, the famous naturalist, was, perhaps, the first person who focused his attention as to how formation of coral reefs take place and ultimately he got success in solving the mystery. He knew it very well that the surface of the earth changes. Mountains are forced up in one place; in another, the crust of the earth sinks.
Above all, when he studied the whole story and background of coral reefs in depth, he ultimately came to conclusion that there were three kinds of coral reefs, namely fringing reefs, barrier reefs and atolls (rings of coral).
When Darwin gathered the entire information and combined it’ together, he evolved the following theory: the formation of volcanic islands take place when an undersea volcano rises above the level of surface of the water. Corals build a fringing reef in the shallow waters of the island shores. With the passage of time, the volcano becomes cold and dead, it starts sinking back into sea as a result of which the fringing reef now becomes separated from the island by a wider channel of voter, which allows it to grow further. Hence, it has become a kind of coral reef i.e. barrier reef. Suppose, the volcano sinks and vanishes completely, only the coral reef is left; it has become an atoll (ring of coral surrounding a lagoon). Besides this we all know that island shores may rise or sink and the levels of ocean may rise or fall (wide fluctuations). All these changes help us in explaining as to how the formation of coral reefs take place.