• Adam’s Bridge, also known as Ram Setu, is a chain of natural limestone shoals connecting Dhanushkodi in India to Talaimannar in Sri Lanka. • The structure is submerged and spans approximately 29 kilometers.
Historical and Cultural Significance:
• Described in the epic Ramayana as a bridge built by the ape army of Ram to reach Sri Lanka. • Named Adam’s Bridge by an East India Company cartographer. • Known as Sethu Bandhai by Persian navigators and was above sea level until a cyclone in 1480.
Recent Mapping Efforts
ISRO’s Detailed Mapping:
• Scientists from ISRO’s National Remote Sensing Centre conducted the most detailed undersea mapping of Adam’s Bridge. • The study utilized NASA’s Ice Cloud and Land Elevation Satellite (ICESat)-2, which uses a laser-borne altimeter to take measurements.
Technological Insights:
• ICESat-2 data from October 2018 through October 2023 was used. • A 10-meter resolution map was created, capturing detailed features of the submerged ridge.
Key Findings from the Study
Geological Structure:
• The ridge is almost entirely submerged, with 99.98% of its volume under shallow waters. • The structure is about 8 meters above the seabed along its entire length, with only 0.02% of it exposed.
Formation of Limestone:
• Limestone forms from the accumulation of marine organism fossils, turning into solid rock over millions of years.
Narrow Channels:
• The study identified 11 narrow channels within the ridge, allowing water exchange between the Gulf of Mannar and the Palk Strait. • These channels help protect the structure from wave action by facilitating water flow.
Environmental and Geological Impact
Wave and Current Dynamics:
• The ridge is continuously exposed to strong waves from both the Gulf of Mannar and the Palk Strait. • Monsoon currents play a significant role in water movement around the bridge, with the southwest monsoon bringing water from the Arabian Sea to the Bay of Bengal, and the northeast monsoon doing the reverse.
Preservation of the Structure:
• The narrow channels within the ridge likely play a crucial role in its preservation by reducing the impact of strong waves.
Conclusion
Scientific and Geological Significance:
• This study provides the first intricate details about the submerged sections of Adam’s Bridge. • It confirms the natural geological origins of the limestone structure, contributing valuable knowledge to both historical and geological studies.
Continued Research and Monitoring:
• Ongoing research and advanced mapping technologies are essential for further understanding and preserving such significant natural structures.
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