The Geological and geophysical survey of the Sethu-samudram Project clearly reveal that Rama'sbridge appears to be a major
Geological feature. The surveys reveal that to the north of Ram Sethu on the Palk Bay side, the formation have undergone down faulting and the Ram Sethu came up as an up thrown block. This geomorphic feature is seem to be continuous and verified both by bathymetry survey and NASA land image.
One could clearly see that this is but a continuous feature with minor depressions upto about 100m width. In consonance with these things there are inter tidal marine sandy islands. These depressions and the islands appear to be neotectonic feature resulting in changes in bathymetry.
It is a well established scientific phenomenon that there has been a major glaciation period (ice age) with glacial maxima at about 18,000 years BP. This feature has been observed and studied in several parts of the world with the help of submerged Corals. During the glacial Maxima, the sea level was about 130m lower than what is today. This is evidenced both on the east
and west coast of India, where submerged Corals occur around 1 to 2m water depths and they are clear indicators of near coastal zone.
The Ram Sethu ridge is a major marine divide. It separates the furious Bay of Bengal sea and sediments in the Palk bay and the very calm placid waters of the Gulf of Mannar. This ridge like feature is similar to the ?Allaband? that was formed after a major earthquake in Arabian Sea in the early 19th century. In the Allaband, a long stretch of about 90km length and about 0.5 to 4km wide zone got uplifted because of a major tectonic event that was responsible for the earthquake. Since this event occurred in the recent past and such huge track of land was raised, people called that it is happened due to the will of Allah and named it Allaband.
The Ram Sethu is a similar feature but formed much earlier due to tectonic causes that were prevalent in these areas. However, during the last ice age (18,000 year BP) the entire area from India to Sri Lanka and further south and southeast were contagious land due to the highly lowered sea level. As and when there were major melting of glaciers both from the mountains as well as from the Antarctic area, the sea level was rising. These features were well recorded and studied by several submerged Coral formations all over the world. About 7,300 years BP the sea level in the southern part of India was about 3.5 m above the present level. This has been deciphered by Dr. P.K. Banerjee, who studied Corals that found in the land part as of Pamban, Rameswaram, and Tuticorin etc. Subsequently the sea level went down and rose +2m above than what is today between 5000 to 4000 years B.P.
The Geological logging of the bore holes drilled by NIOT in the inter tidal areas of Ram Sethu reveals very interesting details. In all the bore holes the top portion is seen to be occupied by recent marine sands. In almost of all the boreholes between 4.5 and 7.5m the borehole intersected hard formations, which have been found to be calcareous sand stones and corals. It is to be pointed out here that Corals are comparatively less dense, compact and somewhat easy to carry. The Corals normally grow atop compact to hard formations for the purpose of stability, and as the sea level rises, the Coral colony grows up vertically to maintain water depth of 1 to 2 m, which is essential for their survival. It is always observed that these Corals have continuous vertical growth like Lakshadweep, Andaman?s, and Gulf of Mannar Natural Park. These have always been found to grow on hard rock bottom. In the case of Ram Sethu area, we observe that the Coral formations hardly occur 1 to 2.5m in length and resting on loose marine sands. Most of these coral rock pieces are seem to be rounded pebbles of corals. These things appear to point these coral rock pieces and pebbles have been transported and placed in these areas.
Since the calcareous sand stones and Corals are less dense than normal hard rock and quite compact, probably these were used by the ancients to form a connecting link to Sri Lanka, on the higher elevations of the Ram Sethu ridge and this is analogous to modern day causeway.
In support of these observations there are many archaeological and geoarchaeological evidences on the south east coast of India around Rameswaram, Tuticorin and the western coast of Sri Lanka. There are raised Teri formations that supported a rich assemblage of mesolithic?microlithic tools indicating the presence of strong human habitation and activity in these areas as early as 8000 to 9000 years B.P and as recent as 4000 years B.P. On Sri Lanka side there are indications of human habitation extending to late Pleistocene (about 13,000 B.P) based on bone and fossils of human and animal form.
All these point to a flourishing human activity on both side of Adams Bridge and probably when the sea levels were just right the link between India and Sri Lanka could have been established.
Source: Dept. of Earth Sciences, Government of India (March, 2007)