Scientists from the Indian Space Research Organisation (Isro) have created the most precise undersea map yet of Adam’s Bridge widely known as the Ram Setu, proving the submerged ridge as a “continuity” from Dhanushkodi in India to Talaimannar in Sri Lanka.
The surveying exercise used a US satellite to reflect laser beams off the sea floor, demonstrating that 99.98 percent of the Ram Setu, a 29-kilometer stretch of limestone shoals, is buried in shallow waters.
As per the reports, the research is the first to provide precise details about the underwater sections of Adam’s Bridge. Giribabu Dandabathula, a scientist with Isro’s National Remote Sensing Centre in Jodhpur regional center, and his associates described their findings in an issue of Scientific Reports.
The submerged structure was named Adam’s Bridge by an East India Company mapper. The structure, called by Indians as Ram Setu, is mentioned in the Ramayana as a bridge constructed by Ram’s army in order to help him reach Sri Lanka, Ravana’s kingdom, to get back his wife Goddess Sita.
Further evidence from geology reveals that the now-submerged range was once a land route between India and Sri Lanka. Persian navigators in the ninth century AD referred to the bridge as Sethu Bandhai or a bridge over the sea. Temple records from Rameswaram indicate that the bridge was above sea level until 1480 when it was demolished by a powerful storm.
Earlier satellite-based observations revealed the undersea construction, although they were primarily focused on exposed sections of the bridge. The sea in the area is extremely shallow, ranging from one to ten meters deep in parts, making navigation and ship mapping of the ridge difficult.
The researchers used ICESat-2 data from October 2018 to October 2023 to generate a 10-meter resolution map of the full length of the submerged ridge, which is sufficient to capture details of the size of a train coach.
According to their findings, the ridge is around 8 meters above the seabed over most of its length. However, only around 0.02 percent of the volume is accessible or visible; the rest is submerged. Limestone is formed from the fossils of sea life. Over millions of years, marine animals’ shells and skeletons accumulate on the ocean floor, pushing down on one another to form solid rock.
Their research also discovered 11 narrow passages, only a few meters wide, that allow water to flow or be exchanged between the Gulf of Mannar on the southwest side and the Palk Strait on the northeast side of the hill.
The experts believe that these tiny channels, or gaps along the ridge’s axis, play an important function in shielding or conserving the structure from the force of wave action. The bridge is constantly exposed to the energy of high waves from both sides: the Gulf of Mannar and the Palk Strait.
During the southwest monsoon, summer monsoon currents bring water from the Arabian Sea into the Bay of Bengal, whereas during the northeast monsoon, winter monsoon currents transport Bay of Bengal waters into the Arabian Sea via the Palk Strait and Adam’s Bridge.
According to the Isro team, the shallow canals allow for free flow or interchange of water between the Gulf of Mannar and Palk Strait, which helps to lessen the impact of waves on the ridge.
It is believed that India and Sri Lanka were formerly part of an ancient supercontinent known as Gondwanaland, which separated and drifted northward as an isolated huge island landmass in the Tethys Sea before colliding with the supercontinent Laurasia between 35 million and 55 million years ago. Over millions of years, sea levels have risen and decreased, drowning and exposing the ridge.
