The tiny Japanese island of Yonaguni, near Taiwan, has become famous for the huge submerged rock structures found near its shores 鈥� the ancient city of a lost civilisation, some claim.
Imposing sets of steps and terraces rise up through the clear water from around 25 metres depth. The structures, with their flat surfaces and near right angles, certainly look deliberately carved (pictured left). Masaaki Kimura, a geologist at the University of the Ryukyus in Okinawa, claims he has identified a huge pyramid, along with castles, monuments and a big stadium, all connected by roads. He says he has also found walls and water channels, as well as quarry marks, stone tools and a stone tablet carved with ancient lettering.
Though popular, Kimura鈥檚 claims about Yonaguni are disputed. Robert Schoch, a geologist at the University of Boston who has dived at Yonaguni many times, thinks the formations are mostly natural. They are made of bedrock, rather than built with separate blocks, and Schoch points out that the rock is sedimentary, with horizontal layers that break along parallel lines as they erode. The region鈥檚 tectonic activity also splits the rock along vertical fault lines. So the strong currents that sweep the area would erode rock along these lines, carving out platforms and steps, he says. 鈥淵ou get a regular blocky structure quite naturally.鈥�
Advertisement
Kimura鈥檚 walls could be horizontal platforms that fell into a vertical position when the rock beneath them eroded. And Schoch says the 鈥渞oads鈥� are just channels swept clean of debris by the currents.
What鈥檚 more, Kimura initially thought the structures were created more than 6000 years ago, when the area would have been above sea level. But his own recent dating work, reported at the 21st Pacific Science Congress in 2007, show they could only have been 鈥渃onstructed鈥� between 3000 and 2000 years before present, when sea level was close to 20th century levels.
Kimura speculates that tectonic activity caused the land to sink tens of metres after this time, but it would be very surprising if this was the case, says Richard Pearson, a specialist in the archaeology of east Asia who spent most of his career at the University of British Columbia, Vancouver, Canada.
On Yonaguni Island, archaeologists have unearthed the remains of small camps behind the sand dunes, including large fireplaces, stone tools and thick brown pottery, dating to 2000 to 2500 BC. But the communities on the island were small. 鈥淭hey are not likely to have had extra energy for building stone monuments,鈥� says Pearson.
And while people in nearby Taiwan at this time were building with stone, there鈥檚 no evidence for anything like the stepped monoliths at Yonaguni. However, the rock formations, which are visible without specialised diving equipment even today, may still have been important to the locals. It is possible that they 鈥渢ouched up鈥� parts of the rock close to the shoreline, says Schoch, making them appear artificial.