Is Ram Setu man-made? What the geology actually says

In 2002, a satellite image began to circulate, and with it a claim that would not die. The image, taken from space, showed a faint chain of pale shapes stretching across the blue water between the tip of southern India and the island of Sri Lanka, like a dotted line drawn by a careful hand. And the caption said: NASA has photographed an ancient man-made bridge, thousands of years old, exactly where the Ramayana says Rama’s army built one to cross to Lanka. Science, it seemed, had confirmed scripture.

It is a beautiful story, and almost every part of the claim attached to that image is wrong. Not the existence of the feature, which is entirely real, but the reasoning wrapped around it. Untangling it is a small masterclass in how a question gets muddled, because the popular framing, “is Ram Setu man-made or natural?”, is actually three different questions jammed into one. Pull them apart and the confusion clears.

The first question: is there a real, ancient, striking feature there? Yes, beyond any dispute. The second: what does geology say formed it? That has a clear mainstream answer. The third: did Rama build it? That is a matter of the Ramayana and of faith, and it belongs to a different register than the other two. The poem itself, and how it came to be told in a hundred versions across Asia, is the subject of The First Poem. The trouble comes entirely from fusing the three, so that a geological claim gets dressed as scriptural proof, or a satellite photo gets read as a verdict on an ancient king. This piece takes them one at a time.

The bridge in the poem

Begin with the scripture, on its own terms. In Valmiki’s Ramayana, in the Yuddha Kanda, the Book of War, Rama stands at the ocean’s edge with his army of vanaras, the forest-people, and no way across to Lanka where Sita is held. The Ocean itself, personified, tells him the task must be given to Nala, the son of the divine architect Vishvakarma, who has inherited a share of his father’s craft. Nala accepts, and the army builds. In Griffith’s public-domain translation:

“O’er the deep sea where monsters play / A bridge, O Ráma, will I lay.”

And the construction, over five days, rock by rock:

“With mighty engines piles of stone / And seated hills were overthrown… / Then the great bridge of wondrous strength / Was built, a hundred leagues in length. / Rocks huge as autumn clouds bound fast / With cordage from the shore were cast.”

Notice what the poem actually describes, because a later tradition has half-buried it. Valmiki’s stones are not floating. They are hills and boulders “bound fast with cordage” and cast into the sea, an engineered causeway of rock and timber. The famous image of stones that float on water, so beloved that people still test pumice in temple courtyards, is a later devotional flowering, prominent in the regional Rama-bhakti retellings but not in Valmiki’s own words. It is worth being exact about this, not to diminish the tradition but to know which claim belongs to which age. The setu, the “bound bridge,” is Valmiki’s. The floating stones are the tradition’s later love speaking.

What the feature actually is

Now the geography, which is not in dispute by anyone. Adam’s Bridge, Ram Setu, Nala Setu: the names change, the feature is one. It is a chain of shoals, sandbanks and limestone shoals running roughly forty-eight kilometres across the sea between Pamban Island, near the great pilgrimage town of Rameswaram in Tamil Nadu, and Mannar Island off northwest Sri Lanka. It separates the Gulf of Mannar to the southwest from the Palk Strait to the northeast. Many of its shoals lie in water less than a metre deep, which is why no ship can cross here and why the sailors of every age had to go around.

A 2024 study by scientists at the Indian Space Research Organisation, using the laser bathymetry of the ICESat-2 satellite, mapped the ridge in fine detail and found that about 99.98 percent of it now lies below the surface, with only the barest fraction breaking the water. Borings into it, going back to the nineteenth century, found sand down to seven or nine metres, and beneath the sand a foundation of conglomerate, calcareous sandstone, and beds of limestone and coral in every stage of decay, from living forms to structureless rock. The mainstream reading of all this is a natural one: the bridge marks a former land connection between India and Sri Lanka, a shallow ridge on which coral grew and along which currents laid down sand, built up and reworked across the long sea-level swings of the recent geological ages.

The different components carry different ages, and conflating them is the source of most of the “how old is the bridge” confusion. The Geological Survey of India dated coral at Rameswaram to around a hundred and twenty-five thousand years, while the sand deposits are far younger, with some studies suggesting the shoal system in its present form is only three to four thousand years old. An old rocky-and-coral substratum with a young sand veneer on top: that is not a contradiction, it is a normal coastal formation. And records suggest the chain was whole enough to walk across until a great storm breached it around 1480, with further storms breaking it since, though that exact date should be held as reported tradition rather than a fact fixed by instruments. The very name “Adam’s Bridge” is not ancient Indian at all: it seems to date from the time of the Persian scholar al-Biruni around the eleventh century, carrying a Muslim legend that Adam crossed here on his way to the peak in Sri Lanka that also bears his name.

What NASA actually said

Which brings us back to the satellite image, and the single most important correction in this whole story.

NASA never said Adam’s Bridge was man-made. When the claim exploded, the office at NASA that curates astronaut and satellite photography addressed it directly, and its words are worth quoting exactly, because they dismantle the myth cleanly. The images, NASA said, show islets that “are real geographical features that have been mapped for centuries.” And then the decisive sentence: “chains of islands form a variety of natural geological processes and their occurrence is not evidence of any human activity.” Finally, on the misreporting itself: to read NASA’s response “as a scientifically rigorous conclusion as to the nature of the Palk Strait islands is both a misinterpretation and misreporting of our response.”

That is the heart of it. A photograph from orbit shows shape, not origin. It can tell you a chain of shoals is there, which everyone has known for centuries. It cannot tell you whether the shoals were laid by longshore currents or by an army of vanaras, because remote imaging carries no information about how far below the water the structure goes, what it is made of, or who, if anyone, made it. The image proves the feature exists. It says nothing at all about who built it, and NASA said so plainly.

There is one dissenting scientific voice worth naming fairly. In 2007, S. Badrinarayanan, a former director of the Geological Survey of India, drilled a series of bore-holes and reported a puzzling sequence, marine sand, then a layer of coral and boulders, then loose sand again, then hard rock. Because coral, he argued, only grows on a hard surface, the coral boulders sitting on loose sand must have been transported and dumped there, which would imply a human hand. It is a real argument from a real geologist, and it should be reported. It is also a minority position, and other geologists have answered that the alternating sequence of sand and coral and rock is exactly what fluctuating sea levels and migrating shoals produce over millennia, with no dumping required. The consensus, from the Geological Survey of India to the recent satellite work, remains that the feature is natural.

The dredge and the canal

For completeness, the feature has a modern political history, which is reported here simply as documented events. In 2005 the government approved the Sethusamudram Shipping Canal Project, a plan to dredge a channel through the shoals so that ships could pass between India’s coasts without the long detour around Sri Lanka. It drew fierce opposition on grounds of ecology and of religious significance. In 2007 the Archaeological Survey of India filed an affidavit in the Supreme Court questioning the historicity of the Ramayana account as a basis for treating the shoals as a monument, and amid public protest the government withdrew that affidavit. These are matters of record and of law, and this piece takes no position on them beyond noting that they happened.

The feature is real; the claims are not

So, is Ram Setu man-made? The scientific answer, held with proper humility about a hard-to-study underwater feature, is that Adam’s Bridge is a natural chain of shoals of great antiquity on a shallow ridge, not an engineered structure, and that the “man-made” and “NASA-confirmed” claims do not survive contact with the evidence. That is what the geology says, and it should be said plainly.

And here the two registers must be kept apart, with respect for both. The feature is real, ancient, and genuinely striking, a line drawn across the sea between two lands, and the Ramayana identifies it as the bridge Rama’s army built to rescue Sita. For countless devotees that identification is a living article of faith, and Rameswaram at its Indian end is one of the holiest pilgrimage sites in the country. Nothing in the geology touches that. NASA’s own words are, in the end, the fairest resting place for the whole question: the satellite image shows a natural-looking chain of islands, and it cannot establish human origin either way, which means it neither proves nor disproves the sacred story. It simply cannot speak to it.

The pseudo-science fails. The scripture stands where scripture stands, on faith, not on a satellite photo. And the shoals lie there under the shallow water, forty-eight kilometres of them, as old as they are, being exactly two things at once to two different kinds of looking: a natural ridge worn by the sea, and the road a god once built to bring his wife home. The mistake was never in holding either. It was only in mistaking one for proof of the other.