[Geography Notes] on Coral Island Pdf for Exam

Coral islands are kinds of islands, and they are formed from coral detritus as well as connected organic materials. A coral island happens in subtropical and tropical areas, commonly in the form of a portion of a coral reef. Coral islands begin in the form of the volcanic island on a hot spot. When the volcano does emerge from the sea, then a fringing reef enlarges on the volcano’s outskirts. Eventually, the volcano shifts to the hot spot via a process that is called plate tectonics. When this happens, the volcano finds it incapable of keeping up with the erosion of the wave, and so, it undergoes subsidence.

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What is a Coral Island in India?

A coral island in India is considered one of the most dynamic and earlier ecosystems of India. A coral reef does not only propose a sanctuary to countless marine life but turns important for shielding the coastline from wearing away. In India, there is nearly 7517km of coastline, and it includes islands though the mainland coast happens to be 6100 km.

Some popular Indian coral reefs remain confined to the Gulf of Manner, Andaman & Nicobar Islands, Palk Strait, the Lakshadweep Islands, and the Gulf of Kutch. All these reefs happen to be Fringing reefs, excluding Lakshadweep as they are Atolls. You will also come across some Patchy corals that remain present all along the inter-tidal zones. 

Some Features of Coral Islands

Though many people know what is coral island, they aren’t aware of its features. A coral island is acknowledged as a tropical island that is built of some organic materials that are derived from the corals’ skeletons and various other plants and animals connected with corals. The coral islands comprise low land but only some metres above sea level, commonly with coconut palms. They remain surrounded by many white coral sand beaches.

The coral islands extend to many kilometres, and they comprise nearly all the tropical limestone islands whose structures are a portion of the living coral reefs. The building of reef takes place below the level of high tide, and a common coral island surmounts the comparatively flat peak of the entire reef system. 

The coral island examples are The American territories of Baker, Jarvis, and Howland Islands etc. Some Indian examples are-

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Gulf of Mannar

The Gulf of Mannar happens to be a huge shallow bay that forms a portion of the Laccadive Sea and it has an average depth of 19 feet or 5.8 meters. This part lies between the Sri Lankan west coast and India’s southeastern tips. The chain of some low islands, as well as reefs, is called Adam’s Bridge or Ram Sethu and it comprises Mannar Island.

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Palk Bay

This is a fifteen thousand square kilometer biodiversity conglomeration that is nestled between India’s South East Peninsula and Sri Lankan. It has a coastal length of two hundred and fifty kilometers. 

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Gulf of Kutch

The Gulf of Kutch happens to be the bay of the Arabian Sea besides the Indian west coast located in Gujarat. It is well-known for its huge daily tides.

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How are Coral Islands Formed?

The formation of coral islands happens to be a dynamic process, and it takes many thousands of years to form a coral island. A coral island is formed with a freshly-formed volcanic island, and it rises above the ocean’s surface. When the island stabilises and magma no longer flows into the ocean, a coral begins to grow. This process happens in the shallow water all across the volcanic island.

Coral reef islands comprise rocks, and they emerge from coral skeletons. They are biologically formed calcium carbonate compounds that are the derivatives of the adjacent coral reefs. The sizes of coral reef islands range from some sq. metres to many sq. km. Again, you will find them in all proportions and shapes. The soils of a coral reef island comprise calcareous algae, coral fragments, various other limestone detritus, and guano that is found from sea birds, various amounts of humus, drifted pumice, and volcanic ash.

Coral reef islands become capable of developing only when ideal conditions maintain coral growth with passing the time. These conditions comprise some favourable physical factors, like high salinity, high temperature, low nutrients, and excellent penetration of light, besides some biological factors in a tropical region. 

Types of Coral Islands 

Coral Atoll

An atoll is acknowledged as a coral reef that is ring-shaped. At times, it emerges as a series of islets and sometimes islands too. The atolls surround bodies of water known as lagoons. Most of the time, lagoons and atolls shield a core island. A channel between islets connects a lagoon to a sea or an open ocean. Atolls form with underwater volcanoes, known as seamounts. At first, a volcano erupts, and it piles up lava. When the volcanoes continue to erupt, then the elevation of the seamount becomes higher, and it finally breaks the water surface. This way, the topmost part of the volcano turns into an oceanic island.

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Fringing Reef

A fringing reef is considered one of the different kinds of coral reefs. These reefs grow closer to the shore on a high island or mainland coasts. Commonly, a fringing reef is shore-attached. Some examples of fringing reefs are Timor-Leste, Indonesia, Philippines, Red Sea, East Africa, The Caribbean and the Australian western coast.

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Barrier Reef

A barrier reef gets featured by a reef and it is separated from the chief coast through a lagoon or deep channel. The initial formation happens on the edge of an open edge. Afterwards, it grows towards the coast or subsequent growth in parallel. The largest and renowned barrier reef example is the Great Barrier Reef of Australia. Some other examples are the New Caledonian Barrier Reef and the Belize Barrier Reef.

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Patch Reefs

These are the isolated little reefs which grow at the bottom of the platform island or even in continental shelf. It is present in between fringing and barrier reefs. They almost never reach the water surface. Patch reefs vary in size.

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Conclusion

A coral island is a low island that is produced in warm waters by very small sea animals known as corals. The corals build up the hard exterior skeletons of calcium carbonate. It is called limestone, and it has huge similarities to the shells of some sea creatures such as mussels and clams.