A bridge between geology and myth
Adam's Bridge, also known as Rama Setu, is a 48-kilometer (30-mile) chain of limestone shoals connecting Pamban Island in southeastern India with Mannar Island in northwestern Sri Lanka. This structure separates the Gulf of Mannar from the Palk Strait. The water in this area is extremely shallow, often just 1 to 10 meters (3 to 30 feet) deep, which makes navigation for large ships impossible. Some of the sandbanks remain dry above the water. The entire formation consists of 103 small, parallel patch reefs.
The origin of the bridge is a subject of scientific and historical debate. Geological evidence strongly suggests it is a natural formation that is a former land connection between India and Sri Lanka. One theory proposes that longshore currents deposited sand in a linear pattern, over which coral began to grow. Another theory points to tectonic movements shaping the land, creating a favorable environment for coral to trap sand and build the discontinuous shoreline. During the last glacial period, from about 115,000 to 11,700 years ago, sea levels were up to 120 meters lower than they are today, exposing the entire Palk Strait as a land connection. As sea levels rose, the strait became submerged around 7,000 years ago. A subsequent minor fall in sea levels around 5,000 years ago may have re-exposed the highest points of this landform, making it periodically walkable.
Reading the rocks and satellite images
Determining a definitive age for the structure is complex. Studies by the Geological Survey of India have dated the coral at Rameswaram Island to 125,000 years ago. Other research suggests the current formation of Adam's Bridge is more recent, possibly forming only about 3,500 to 4,300 years ago. Records suggest the bridge may have been largely intact and passable on foot until a major storm breached it in the year 1480.
The debate over its origin intensified with the advent of satellite imagery. Some observers interpreted the linear arrangement of the shoals as evidence of an artificial, or human-modified, causeway, aligning with its description in the Hindu epic Ramayana as a bridge built by the god Rama. However, geologists and organizations like the Archaeological Survey of India have concluded that there is no proof of human construction, and the features are consistent with natural geological processes like sedimentation, coral growth, and tectonic activity. The rectangular shapes seen in some images are common in natural limestone formations.
The name "Adam's Bridge" is thought to have originated with early Islamic scholars around the 11th century, based on the legend that Adam used it to cross from Sri Lanka to India after being expelled from the Garden of Eden.