Valmiki Gives Rama's Army Five Days to Build Ram Setu, and Surveys Have Spent Decades Measuring the Limestone Shoals Where Devotees Place It

Ram Setu is the causeway that Rama’s vanara army lays across the sea to Lanka in five days, according to Valmiki’s Ramayana. The name is also given to a chain of limestone shoals that runs about 48 km between Pamban (Rameswaram) Island in Tamil Nadu and Mannar Island off Sri Lanka, the length that Britannica and a NASA image caption both give.

Devotees hold that the shoals are what remains of that causeway. Surveyors, satellites, a government corporation, the courts and Parliament have since examined the same stretch of sea. This article keeps the two accounts apart, first the tradition as the text and the shrines tell it, then the measurements, and it does not claim that either one proves or disproves the other.

Five days and a hundred yojanas in the Yuddha Kanda

Hanuman has already crossed the sea in a single leap, but an army cannot leap. In the Yuddha Kanda, the war book of the Ramayana, Rama spreads kusha grass, a sacred grass, on the shore, faces east and lies down to wait for the Ocean. He waits three nights. The Ocean does not appear, Rama’s eyes redden with anger, and he takes up his bow and sends arrows that agitate the sea while sages in the sky cry out in alarm (Sarga 21).

In the next sarga, with Rama readying a missile, the Ocean appears and tells him to have Nala build the bridge. Nala is the son of Vishvakarma, the divine craftsman. Hundreds of thousands of vanaras do the work under Rama’s command. In K. M. K. Murthy’s word-for-word English translation the bridge grows by 14 yojanas on the first day, 20 on the second, 21 on the third, 22 on the fourth and 23 on the fifth, when it reaches the far shore. Verse 74 gives its size as 100 yojanas long and 10 wide. A yojana is an old Indian unit of distance, and this article does not convert it.

The builders use trees, among them sala, bamboo, palmyra, mango and asoka, together with rocks and mountain peaks, some lifted by machines, and long cords to keep the stones in a line. The war that follows, and what the poem asks of Rama afterwards, is told in Rama and the price of being the ideal man.

Where devotees place the bridge today

The Ministry of Tourism’s Incredible India site says Rama broke the bridge with his bow at Dhanushkodi, which is how the place got its name. Dhanushkodi lies at the southern tip of Rameswaram island. At the Kothandaramar temple there, the site says, Vibhishana, Ravana’s brother, is believed to have sought refuge with Rama, and Rama performed his coronation as ruler of Lanka. The Ramanathapuram district administration records that a cyclone washed Dhanushkodi away in 1964 and that the temple remained intact.

At Rameswaram itself, the same site says that after the war Rama wished to atone for the killings, bathed at Jada Teertham and worshipped Shiva. The lingam in the sanctum is believed to be the one Sita made from sand when Hanuman was late bringing one from the Himalayas.

What a survey finds: length, depth and rock

What follows is what instruments, surveys and courts have recorded on the same stretch of sea. Britannica and NASA’s Jet Propulsion Laboratory both give a length of 48 km. A team from the Indian Space Research Organisation’s National Remote Sensing Centre, whose lead author is Giribabu Dandabathula, built a seabed model from the green laser of NASA’s ICESat-2 satellite and reported in Scientific Reports on 28 June 2024 that the ridge runs about 29 km from Dhanushkodi to Talaimannar. In Parliament in December 2022, Minister of State Jitendra Singh gave 56 km for the bridge “if you go by the history”, referring to the Ramayana, according to Scroll. None of these sources reconciles the three figures.

Depth also varies with the method. Britannica says many of the shoals are less than 1 metre deep and some sandbanks are dry. Ashis Kumar Paul, in the Journal of Indian Geomorphology in 2021, puts the bridge at 2 to 3 metres with living corals and sand banks, and notes that the sand banks show at low tide in February and March. The ISRO team found it mostly under 10 metres, with narrow channels between sand banks 2 to 3 metres deep. It calculated that 99.98 per cent of the structure’s volume, about 1 cubic km, lies below mean sea level. The shallows are why ships moving between India’s east and west coasts go around Sri Lanka, the Sethusamudram Corporation’s chairman writes.

Borings made by British surveyors in the 19th century, the ISRO paper says, found sand to a depth of 7 to 9 metres in places. Below it lay either Holocene conglomerate or calcareous sandstone, a rock made of cemented lime-rich sand, and at some drillings the base held coral reefs in all stages of decay. The earliest known dredging at the shoals dates to 1838, Britannica reports.

How old the shoals are, and what each date covers

No study the editors could open dates the shoals directly. Britannica gives two figures and cites the work behind neither. Studies by the Geological Survey of India dated coral on Rameswaram Island to 125,000 years ago, it says, while other studies it does not name put the formation of the bridge at only about 3,500 years ago. NASA’s caption states that the geologic origin of the bridge “is still controversial”.

Most dated material belongs to the ground around it. Paul’s paper gives the sea level at the last glacial low stand as about 130 metres below today’s on India’s east coast, citing Loveson and Nigam (2019), and says the shape of the sea floor points to a land link across Palk Bay and the Gulf of Mannar at that time. Older reef terraces on Rameswaram island date to 21,000 to 32,000 years before present, Paul writes, citing Stoddart and Pillai (1972). Paul reads today’s landform as a “double tombolo”, sand built up during the Holocene as the Dhanushkodi spit grew southeast over submerged coral banks toward Mannar Island.

Seismic work by K. M. Dubey, A. K. Chaubey, A. S. Gaur and M. V. Joglekar of the CSIR-National Institute of Oceanography, published online in Quaternary Research on 2 September 2022, found buried channels that began in the Palk Strait and drained into the Gulf of Mannar. The youngest were fully buried by about 7,000 years ago. The authors conclude that the strait held fresh water through the last glacial period, that seawater began to enter about 8,500 years ago, and that since about 7,000 years ago crossing has generally needed boats, except during minor falls in sea level. Their abstract adds that foragers in the early to mid Holocene, the period since the last ice age, would have needed rafts, floats or artificial structures such as a bandh or bridge to cross shallow estuarine patches. It reports no discovery of such a structure.

The ISRO paper says sea levels have repeatedly drowned and exposed the land link between India and Sri Lanka, and that the bridge may result from conditions tied to sea-level changes since the last deglaciation. It gives no age of its own for the bridge. The 2021 NIO proposal described below plans radiometric and thermoluminescence dating of sediment from the site.

The 1480 storm and the walk across

Records suggest the bridge may have been whole and passable on foot until 1480, when a storm breached it, and later storms made further breaches, Britannica writes. NASA’s caption for an image taken on 25 March 2020 says the bridge was reportedly passable until the 15th century, when storms destroyed its integrity. Neither source names the record or says where it is kept, and the editors could not find a published edition of it. The ISRO paper does describe sandbanks that appear at irregular intervals along the ridge and generally shift with the seasons, in a zone of wave attack from both sides.

What NASA’s images show and what NASA said

In 2002, according to Down To Earth, websites run by non-resident Indians claimed that a 30-km bridge of shoals in NASA’s images resembled a structure in the Ramayana and that its curvature and composition showed human construction. NASA official Mark Hess replied that remote sensing images from orbit “cannot provide direct information about the origin or age of a chain of islands” and cannot show whether humans were involved. DNA India quotes Hess as also calling it a naturally occurring chain of sandbanks about 30 km long. His statement concerns what a photograph can establish.

The question came back in September 2007, during the affidavit dispute described below. NASA spokesman Michael Braukus rejected claims by Bharatiya Janata Party leaders that NASA had carbon-dated the bridge to 1.7 million years, saying “I am not aware of any carbon dating either”. He added that no position could be taken on the basis of the astronaut photographs. NASA’s current caption for its ASTER satellite image repeats the 48 km length and says the structure was formerly a land bridge.

A canal, a stay order and a 2007 affidavit

Proposals to cut a ship canal here go back to 1860, the Sethusamudram Corporation’s chairman writes. The Government of India formed the corporation as a special purpose company on 2 September 2004, and Britannica says the Sethusamudram Shipping Canal Project was approved in 2005. LiveLaw describes it as an 83 km channel dredged between Mannar and the Palk Strait. The corporation’s litigation table lists Madras High Court petitions from 2004 and 2005 over the public hearing and the environmental clearance. It also lists two petitions Subramanian Swamy filed in 2007, now transfer cases in the Supreme Court. One asks for the project to follow another route without destroying Ram Sethu. Another asks for an investigation into the origin and history of the structure and for its declaration as a monument of national importance.

In mid-September 2007 the Centre filed an affidavit in the Supreme Court whose drafting was blamed on the Archaeological Survey of India (ASI), IANS reported. It said the Valmiki Ramayana, the Ramcharitmanas and other texts, which it called part of ancient Indian literature, could not be treated as historical records that incontrovertibly prove the persons or events they describe. It also said the shoals are a natural formation of sand bars shaped over several millennia by wave action and sedimentation. After protests by the Bharatiya Janata Party and the Vishwa Hindu Parishad, the government withdrew the affidavit and apologised for the remarks, and the ASI suspended two senior officials. The corporation’s annual report dates the Supreme Court’s interim order suspending dredging at Adam’s Bridge to 14 September 2007. A Centre affidavit of 2008, as Moneylife reported in 2012, said the government “should not be called upon to respond to the issues of faith, except in recognising their existence”. All dredging in the Palk Bay and Palk Strait stopped in July 2009, the report says.

On 16 March 2018 the Centre told the court it intends to explore an alternative to the earlier alignment of the project “without affecting / damaging the Adam’s Bridge / Ram Sethu in the interest of the nation”.

Underwater study, a Rajya Sabha reply and the case today

The Central Advisory Board on Archaeology, which sits under the ASI, approved in December 2020 a proposal for underwater exploration by CSIR-NIO, the Sentinel reported on 25 January 2021. The proposal speaks of scientific and underwater archaeological studies to understand the nature and formation of Ram Setu and the area around it. NIO’s director said the work would use radiometric and thermoluminescence dating, with the research vessels Sindhu Sadhana or Sindhu Sankalp collecting sediment from 35 to 40 metres below the water. No published result from this study turned up in any source the editors could open.

On Thursday 22 December 2022, answering a question in the Rajya Sabha, Singh said Indian satellites had taken high-resolution images of the Ram Setu region, and that such images cannot give direct information about the origin and age of the structure. He said space technology had found “some kind of limestone shoals” that cannot be accurately called remnants of parts of a bridge but show continuity in location, from which surmises can be drawn. Chhattisgarh Chief Minister Bhupesh Baghel, of the Congress, demanded an apology from the government, and BJP members accused the Congress of twisting the reply, Scroll reported.

In January 2023 the Centre told the Supreme Court that the Ministry of Culture was considering a proposal on national heritage status. The corporation’s report lists hearings on 11 December 2023 and 3 March 2025 and says the company “is awaiting further hearing and final judgment”. On 29 August 2025 a bench of Justices Vikram Nath and Sandeep Mehta issued notice on a new petition by Swamy, which asks for a time-bound decision on national monument status and for a survey of Ram Setu by the Geological Survey of India and the ASI.