I hope experts in the study of corals will explain the existence of coral rocks on Rama Setu in deeper layers, say 10 m. below sea-level according to bathymetry (sea-depth) and geological and geo-technical surveys reported in the government web-site:
The uniqueness of Rama Setu region with coral rocks as building blocks appears to be due to the following:
1. this is the only region in the world, along the coastline of Bharatam, ranging from Makran coast, Gulf of Kutch, Gulf of Khambat, Gulf of Mannar — that turbinella pyrum, called s’ankha flourishes. Nowhere else in the world does such a coral reef exist.
2. on either end of Rama Setu, there was subsidence of the canyon below the ocean, resulting in the rise of the land-link between Dhanushkodi and Talaimannar.
3. ocean currents do NOT form coral blocks, ocean currents can only allow accumulation of limestone or mineral-encrusted-sand aggregates, corals are not indigenous to Rama Setu, blocks of coral rocks should have been brought from outside the region, say the coral reef islands from Tuthukudi to Rameswaram.
4. Rama Setu is a crescendo formed by a huge mountain, almost a canyon, rising in height in a steep slope — from 3000 m. below sea-level near Tuthukudi to almost zero m. between Dhanushkodi and Talaimannar.
5. Is it really possible to keep a 12 m. deep channel dredged, in the mid-ocean, through such a steel slope stable and safe from mountainous land-slides? Won’t the limestone rocks cave into such a channel, given the steep slope? Imagine such a canal in, say, Himalayas. Will the canal stay open given the dynamic state of the mountains — due to plate tectonics — and the recurrences of avalanches? Has any study been done on the state of the canyon topped by the Rama Setu where people had lived and where trees grew (according to a 1799 eye-witness report in Asiatic Researches, Asiatic Society)?
See William Vestal1 and Allen Lowrie1 (1) Geology and Geophysics Branch-Code 7220, U.S. Naval Oceanographic Office NSTL Station, 39522, MS Abstract Two suites of slumps from opposite margins of the Gulf of Mannar, between Sri Lanka and southern India, have met and coalesced. The “Eastern Comorin” Slump is the more coherent of the two with a length of 70 to 100 km. The “Colombo” side slump consists of two to four blocks 15 to 35 km in length. Both slump-suites decrease to the south. A paleoslump underlies the western toe of the East Comorin Slump at a depth of some 800 meters. To the south, an enlarging and deepening submarine canyon marks the area of slump coalescence.
How coral reefs are formed
coral reefs, limestone formations produced by living organisms, found in shallow, tropical marine waters. In most reefs, the predominant organisms are stony corals, colonial cnidarians that secrete an exoskeleton of calcium carbonate (limestone). The accumulation of skeletal material, broken and piled up by wave action, produces a massive calcareous formation that supports the living corals and a great variety of other animal and plant life. Although corals are found both in temperate and tropical waters, reefs are formed only in a zone extending at most from 30°N to 30°S of the equator; the reef-forming corals do not grow at depths of over 100 ft (30 m) or where the water temperature falls below 72°F (22°C). Corals are not the only, and in some cases not even the major, reef-forming organisms. Calcium carbonate is also deposited by coralline algae, the protozoan foraminiferans, some mollusks, echinoderms, and tube-building annelid worms. However, any reef formed by a biological community is usually called a coral reef.
Geologically, coral reefs are classified into three main types. Fringing reefs are coral platforms that are more or less continuous with the shore and exposed at low tide. Barrier reefs are separated from the shore by a wide, deep lagoon or surround a lagoon that has a central island. An atoll is a reef surrounding a lagoon that has no central island, with passages through the reef to the sea. It is generally believed that fringing reefs formed as a result of upward and outward growth of corals that became established on rocks near shore; there is disagreement about the nature of barrier reef and atoll formation. Charles Darwin postulated a progression from fringing reef to barrier reef to atoll, as a result of a slow, steady sinking of the seafloor that creates a lagoon and a simultaneous upward and outward growth of coral. Where entire volcanic islands sink, only the reef remains above water, forming an atoll. Not all scientists accept Darwin’s proposal, but most current theories involve subsidence of the seafloor, although changes of the ocean level may also be involved.
Sediments accumulate on the lagoon side of atolls and support vegetation; in time the entire lagoon may fill, creating an island. Many such atolls and islands, common in the Pacific and Indian oceans, are inhabited. The Great Barrier Reef of NE Australia is the largest known complex of coral reefs. It is 10 to 90 mi (16–145 km) wide and about 1250 mi (2010 km) long, and is separated from the shore by a lagoon 10 to 150 mi (16–240 km) wide.
Reefs are under numerous environmental pressures, including damage from increased coastal development, water pollution, tourism, runoff containing agricultural chemicals, abrasion by ships’ hulls and anchors, and smothering by upstream sedimentation. Coral reefs are sometimes destroyed in fishing when poison or dynamite are used to catch fish and by the harvesting of coral for use in jewelry. During the 1990s, many previously unknown diseases began attacking coral reefs worldwide, causing rapidly spreading damage.
See A. Emery, The Coral Reef (1981); J. A. Fagerstrom, The Evolution of Reef Communities (1987).
The Columbia Electronic Encyclopedia, 6th ed.