What is Coral Island?
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-
The Lakshadweep Islands
The Lakshadweep Islands are considered a big chain of coral islands of India besides some minor banks and islets.
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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.
FAQs on Coral Island
1. What exactly is a coral island and how is it formed?
A coral island is a type of island formed from the skeletons of tiny marine animals called coral polyps. These polyps secrete hard, cup-like skeletons of calcium carbonate. Over thousands of years, as old polyps die, new ones grow on top, creating a massive underwater structure. Eventually, this structure can break the surface of the water, and with the accumulation of sand and other debris, it becomes a low-lying island.
2. What are the main types of coral reefs that create islands?
There are three main types of coral reefs that can lead to the formation of islands:
- Fringing Reefs: These grow directly from the shore of a continent or volcanic island, forming a border along the coastline.
- Barrier Reefs: These are similar to fringing reefs but are separated from the coastline by a wide, deep lagoon. Australia's Great Barrier Reef is the most famous example.
- Atolls: These are ring-shaped reefs that enclose a central lagoon. They typically form on top of submerged volcanic islands.
3. Where in the world are most coral islands located?
Most coral islands are found in the warm, shallow, clear waters of the tropics and subtropics, generally between 30° N and 30° S of the equator. The vast majority are located in the Indo-Pacific region, which includes the Pacific and Indian Oceans. The Caribbean Sea also has a significant number of coral reefs and islands.
4. Which island groups in India are known as coral islands?
In India, the Lakshadweep Islands are the most prominent example of coral islands. They are a group of atolls built up from coral reefs. The Andaman and Nicobar Islands also feature beautiful fringing reefs, although the islands themselves are primarily volcanic in origin.
5. Why are coral reefs often called the 'rainforests of the sea'?
This comparison is made because of their incredible biodiversity. Just as rainforests on land are home to a huge variety of plants and animals, coral reefs support an enormous number of marine species. They provide essential food, shelter, and breeding grounds for about 25% of all marine life, despite covering less than 1% of the ocean floor.
6. What is the main difference between a coral island and a volcanic island?
The main difference lies in their origin. A coral island is biological, built up from the accumulated skeletons of marine organisms. In contrast, a volcanic island is geological, formed when molten rock (lava) from an underwater volcano erupts, cools, and builds up above the sea level. As a result, coral islands are typically low and flat, while volcanic islands can be very mountainous.
7. What is coral bleaching and why is it so dangerous for coral reefs?
Coral bleaching is a process where corals turn white. It happens when corals are stressed by changes in conditions, such as a rise in water temperature. This stress causes them to expel the symbiotic algae (zooxanthellae) living in their tissues, which provide them with most of their food and colour. Bleaching is dangerous because if the warm conditions persist, the corals will starve and die, leading to the collapse of the entire reef ecosystem that depends on them.
8. How do human activities specifically threaten the survival of coral islands?
Human activities pose a major threat in several ways:
- Climate Change: Burning fossil fuels raises global temperatures, leading to warmer oceans and causing widespread coral bleaching.
- Ocean Acidification: Increased carbon dioxide in the atmosphere is absorbed by the ocean, making it more acidic. This acidity makes it difficult for corals to build their calcium carbonate skeletons.
- Pollution: Runoff from agriculture and coastal cities can introduce harmful chemicals and sediments that smother reefs.
- Destructive Fishing: Practices like dynamite or cyanide fishing physically destroy the reef structure.
