This is in response to Kalaignar Karunanidhi’s comments of May 22, 2007 about a possible land-link between Kodiakkarai (Point Calimere) and Jaffna (Yaashpaanam).
It may be seen from the following article by GG Vaz et al., that the formation of Rama Setu was due to subsidence: Current Science, Vol. 92, No. 5, 10 March 2007, pp. 671-675 Subsidence of southern part of erstwhile Dhanushkodi township, Tamil Nadu – evidences from bathymetry, side scan and underwater videography The causes for the formation of Rama Setu from Dhanushkodi are entirely different from the fault lines at work near Kodiakkarai resulting in accumulation of shoals. It is a welcome development that Kalaignar is talking geology. It will be necessary to entrust the review to a team of scientists from many disciplines as recommended by the Ramanathapuram Judge before attempting to damage or destroy Rama Setu.
It should be noted that the Gulf of Mannar is a clearly identified ocean, distinct from the Bay of Bengal because of the existence of Rama Setu (Adam’s bridge). Such a land-bridge does NOT exist between Kodiakkarai and Jaffna. That such a land-bridge may be formed in the future is speculation assuming that the sea regressions and sedimentations will follow a secular pattern. The ocean currents and counter-currents in the Gulf of Mannar are far too complex to make such speculative conjectures.
Kodiakkarai is also called Point Calimere. It is a wild life sanctuary.
The depth of the ocean between Dhanushkodi and Talaimannar is on an average three fathoms, while the depth between Point Calimere and Kanakesanturai is over eight fathoms. Only a lower sea level by over 8 metres would have connected the land between Bharatam and Srilanka through this route. Explanations offered for the existence of a land bridge between Dhanushkodi and Talaimannar are: eustatic changes and rising coastlines occurring concurrently. (Akkaraju Sarma, 1978, Paleoecology of Coastal Tamilnadu, South India: chronology of raised beaches, in: Proceedings, American Philosophical Society, Vol. 122, No. 6, p.416). The conclusions of this study are: “There are several marine terraces in Tamilnadu whose elevations have been mentioned. The younger marine terraces probably are late Pleistocene formations. The higher marine terraces are of marginal archaeological interest. The tectonically derived (uplift-associated) terraces are of extreme archaeological interest. Regions with spot elevations of 3 and 6 m are especially interesting, as the archaeological material in these provided clues to chronology of the uplift. The 3 and 6 m uplifted areas were found to be associated with archaeological sites ranging from the second century B.C. to the first century A.D., and sites extending from the seventh century A.D. to the thirteenth century A.D. These terraces and uplifted areas are all overlain by quaternary deposits in the districts of Kanyakumari, Tirunelveli, and Ramnad. Some of these deposits are composed of corals, limestones mixed with organic debris, and marine shells. In the coastal Tanjore district, these coastal terraces are uniquely different, being mostly alluvial sediments deposited over beach ridges. In South Arcot and Chingleput, beach sands predominate which, as such, obliterate the uplift evidences.” In this study which attempts to study palaeoecology of regressions of the sea in the past, one point stands out: the distinct differences in the coral terraces of the Rama Setu (between Dhanushkodi and Talaimannar) area and the area between Kodiakkarai (Point Calimere) and Jaffna (Yashppaanam).
The coast from Pamban gap to Kodiakkarai is in the sandy shallows of Palk Bay. This ancient lighthouse at Kodiakkarai is said to have been built by Chola kings about 1000 years ago. This could be the port from which ships might have sailed towards Indonesia and Straits of Malacca during the days of King Vijaya. This lighthouse was destroyed by the tsunami of 2004. The ancient names for Kodiakkarai on the the shallow waters of Palk Straits were Tirumarai, Vedaranyam Kaadu. The forest (kaadu) commences from ‘Agastiyam Palli’ in Vedaranyam. “The swamp suports a major commercial fishery and also nursery for many marine fishes. It is an important spawning ground for shrimps (Penaeus indicus, P. monodon), crabs (Scylla serrata) and fishes.The site supports the IUCN red-listed birds Pelecanus philippensis, Phoenicopterus minor, Limnodromus semipalmatus, and Eurynorhynchus pygmaeus, the mammal Antilope cervicapra and the reptiles Chelonia mydas, Lepidochelys olivacea, Eretmochelys imbricata. This ecosystem regularly supports about 30,000 flamingos and tens of thousands of other waterbirds and also supports over 1% of the individuals in the south Asia population of Pelecanus philippensis (200-300 individuals).” http://www.casmbenvis.nic.in/sdnp/convention.htm Point Calimere, another name for Kodiakkarai is associated with Ramayana. “The highest point of the cape, at an elevation of 4 m., is Ramarpaadam, meaning, ‘Rama’s feet’ in Tamil. A stone slab which bears the impressions of two feet, and is presumed to be the place where Lord Rama stood and reconnoitered Ravana’s kingdom in Sri Lanka, which lies 48 km. to the south.” http://mycountryonline.com/about/Calimere.htm Mirror: http://en.wikipedia.org/wiki/Calimere
One geomorphological view is that sedimentation explains the accretion of shoals near Kodiakkarai. http://www.geocities.com/sethushipcanal/Geomorphology.htm The tsunami of Dec. 26, 2004 which struck the coast near Nagapattinam has significantly altered the sea-depths near Kodiakkarai. http://www.recoverlanka.net/docs/Ignorance.pdf
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A qualitative assessment of seismic risk along the Peninsular coast of India, south of 19°N
Pronab. K. Banerjee, , a, G. G. Vazb, B. J. Senguptac and A. Bagchic
a C/1, Greenwood, 315B, Upen Banerjee Road, Calcutta 700, 060, India
b Marine Wing, Geological Survey of India, Vishakhapatnam 530023, India
c Marine Wing, Geological Survey of India, Calcutta 700 016, India
Received 12 July 2000; revised 10 May 2001; accepted 10 May 2001. Available online 13 August 2001.
Many earthquakes have been recorded from the coastal margin of the Indian peninsular shield during the last 200 years. Largely made up of Precambrian assemblages with variable cover of Jurassic to Quaternary sedimentary rocks and Cretaceous-Eocene volcanics, the peninsular shield was long held to be aseismic. Recent measurements, however, show that this continental fragment is being pushed northeastward by the Carlsberg and Central Indian ridges; and the Indo-Myanmar subduction zone is exerting vigorous slab pull towards the east. Repeated cycles of sea level change during the Quaternary have also induced continuing hydro-isostatic adjustment due to variable melt water loading in the Bay of Bengal and the Arabian sea. All these forces produce space-time fluctuations of strain around many small to large faults, which occur in the upper crust of the shield. Some of the faults have been intermittently active (during the past 100 kyr); others were active earlier. Although the Shillong plateau and the associated hill ranges of northeastern India and Myanmar are subject to the maximum seismic hazard, the peninsular coast is also vulnerable to intermittent seismicity. We present illustrative evidence of some active faults, which are recognisable (a) on coastal land by displaced Pleistocene weathered cover, hot springs, leakages of native mercury and allochthonous geochemical anomalies of base metals and (b) offshore below the inner shelf by horst-shaped uplifted segments and intra-formational slump folds on and below the top shallow seismic (3.5 kHz) reflector. On the other hand, there are long stretches of the east coast at Vishakhapatnam and Manappad Point, which do not show active faults. Step-like marine terraces, which occur up to+6 m above the low tide level (LTL) preserve records of relative sea level fluctuations during the Holocene and the Last Interglacial. In such sectors, absence of tectonic disturbance during the last 100 ka is also corroborated by lateral continuity of shallow seismic reflectors below the inner shelf over many kilometers. Since authentic historical (200–1000 years B.P.) records of seismicity along the Peninsular coast are virtually unavailable, the likely recurrence interval between earthquakes in each sector cannot be gauged. We, therefore, propose a scale of seismic risk, based on geometry of the mappable faults and available seismic records of the last two centuries. These could be used in combination to rank the densely populated coastal tracts sector-wise.
Journal: Geo-Marine letters, Vol. 2, Nos. 3-4, September 1982, pages 171-177
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.
Bathymetry (sea-depth) map near Rama Setu http://www.ngdc.noaa.gov/mgg/image/2minsurface/1350/45N045E.jpg These images were generated from the ETOPO2v2 (2006) database. ETOPO2v2 was created at NGDC from digital databases of seafloor and land elevations on a 2-minute latitude/longitude grid (1 minute of latitude = 1 nautical mile, or 1.852 km). http://www.ngdc.noaa.gov/mgg/image/2minrelief.html