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Yonaguni Monument: The Japanese Atlantis

A look at a massive stone structure off the coast of Japan, said to be a manmade pyramid.  

by Brian Dunning

Filed under Ancient Mysteries, Natural History, Urban Legends

Skeptoid Podcast #220
August 24, 2010
Podcast transcript | Listen | Subscribe


Yonaguni Monument
The Yonaguni formation called
"The Turtle"
(Public credit: Wikimedia)

About 25 meters beneath the waters off Japan lies a stepped pyramid. We don't know who built it, or when; but there it is, plain as day, available for anyone to go down and inspect. Even now at this very minute, the current washes past sharply squared stone blocks standing dark and forbidding, rising nearly high enough to break the surface. It is called the Yonaguni Monument.

The Japanese archipelago stretches for nearly 4,000 kilometers, from Russia's Kamchatka Peninsula to the island of Taiwain, off the coast of mainland China. At its extreme southwestern tip is the small island of Yonaguni, Japan's most western point, just a scant 100 kilometers from Taiwan. It's quite small, less than thirty square kilometers, with only 1700 residents, but it's famous for something found in its waters: Hammerhead sharks.

Lots of hammerhead sharks. They're so ubiquitous that divers come from all over the world to swim with them. And wherever you have a lot of divers, things under the water tend to be found. And that's just what happened in 1986, when a representative from the Yonaguni tourism board was out exploring off the southernmost tip of the island, looking for a hammerhead diving spot to promote. What he came across was not what he set out to look for, though.

As you're probably aware, Japan is in a region of great tectonic instability, the Pacific Ring of Fire. It lies just beside the convergence of the Pacific Plate and the Philippine Sea Plate, and as a result, it's home to ten percent of the world's active volcanoes. Severe earthquakes are a familiar event there. The layered sandstone bedrock around Yonaguni is therefore deeply fractured. As the tourism rep swam, he passed over this cracked and piled terrain, until he came to a particular formation that stood out. He named the area Iseki Point, or Ruins Point.

He passed the word that he'd found something that looked like a manmade castle. A professor of marine geology, Masaaki Kimura, came to have a look for himself, and what he saw has dominated his life ever since. Kimura founded the Marine Science and Cultural Heritage Research Association, an organization devoted to proving that the Yonaguni Monument is not merely the natural formation it would appear to be, but rather a manmade structure, consisting of a huge network of buildings, castles, monuments, a stadium, and other structures, all connected by an elaborate system of roads and waterways.

It's exactly the kind of story that the public loves. Headlines trumpeted Kimura's discovery with such cliche phrases as "Scholars mystified", "underwater city", and "Japanese Atlantis" (as I so cleverly titled this episode). History's Mysteries on the History Channel produced an episode called "Japan's Mysterious Pyramids" which promoted the idea with little critique; and again on Ancient Discoveries with an episode called "Lost Cities of the Deep". The BBC and the Discovery Channel have also produced documentaries promoting the Yonaguni Monument's manmade past.

Web forums and conspiracy sites love to exaggerate such stories as this one. Among the formations identified by Dr. Kimura is one that he has named "Jacques' Eyes", after Jacques Mayol who used to freedive the site. It's a big roundish rock with two depressions near where eyes might be, but it certainly does not look like a carved head and Kimura does not presume to identify it as one. He has a photograph of it on his web site that he took personally. He contends that the eyes were carved, but that the rest of the rock is natural. However, there's a completely different photograph floating around the Internet showing three divers swimming around a tremendous stone head that is very obviously manmade, including what looks to be a feathered headdress. Whatever the source of this photograph is, it bears no resemblance at all to the rock at Yonaguni, despite its being so identified on every web site I found it.

I've studied Dr. Kimura's photograph of the Jacques' Eyes formation and I'm far from convinced the eyes were carved. They're large concave depressions without distinct edges, not eye shaped, not symmetrical, and not convex like an eyeball. I believe that even incompetent artists would have done a far better job of representing human eyes. Although the underwater lighting is from directly above and the shadows can make them resemble eyes, they wouldn't have looked anything like that in the open sunlight.

And open sunlight is the key to Dr. Kimura's hypothesis, which is that this formation was on dry land when ocean levels were lower during the last ice age. 8-10,000 years ago, the Yonaguni Monument was dry; and for tens of thousands of years before that, it was high and dry.

As you can guess, I'm not the only one who is skeptical of Dr. Kimura's interpretation of the bedrock formations. Virtually all marine geologists who have seen the pictures are satisfied that it's perfectly consistent with other formations of fractured sandstones. Everyone grants that it is unusually dramatic and has a lot of interesting features, but there's nothing there that's not seen anywhere else. The work of Kimura's own foundation, which researches many similar formations off the surrounding islands, is evidence that Yonaguni is not especially unique.

This dispute plays right into the hands of the documentary filmmakers, who are looking for the conflict angle in order to promote the idea of controversy, trying to convince us that scientists are somehow torn or debating over this. They're not. Kimura has a few supporters, but the consensus is resoundingly against him. Dr. Robert Schoch, a geologist at Boston University, is the most often quoted scientist taking the opposing position. Dr. Schoch is probably best known for his work on assigning Egypt's Sphinx and Great Pyramid dates that are much earlier than previously believed, based on his analysis of weathering (you may have seen him discuss this on science channel documentaries). So Schoch is, himself, a bit of a maverick; apparently very few other geologists or archaeologists have found Kimura's photographs and interpretations to be compelling enough to work on.

Schoch has made a few dives on Yonaguni; Kimura has made over a hundred. Nevertheless, Schoch noted what is, I think, the single most damning point against the idea that Yonaguni is manmade:

"...The structure is, as far as I could determine, composed entirely of solid 'living' bedrock. No part of the monument is constructed of separate blocks of rock that have been placed into position. This is an important point, for carved and arranged rock blocks would definitively indicate a man-made origin for the structure - yet I could find no such evidence."

The paleogeology of the region is well known, and Schoch brought samples of the Yonaguni rock to the surface for analysis. He found that they were, as suspected, mudstone and sandstone of the formation called the Lower Miocene Yaeyama Group, which was deposited some 20 million years ago.

"These rocks contain numerous well-defined, parallel bedding planes along which the layers easily separate. The rocks of this group are also criss-crossed by numerous sets of parallel and vertical ... joints and fractures. Yonaguni lies in an earthquake-prone region; such earthquakes tend to fracture the rocks in a regular manner... The more I compared the natural, but highly regular, weathering and erosional features observed on the modern coast of the island with the structural characteristics of the Yonaguni Monument, the more I became convinced that the Yonaguni Monument is primarily the result of natural geological and geomorphological processes at work. On the surface I also found depressions and cavities forming naturally that look exactly like the supposed 'post holes' that some researchers have noticed on the underwater Yonaguni Monument."

In recent years, Dr. Kimura has acknowledged that the basic structure of the Monument is probably natural, but asserts that it has been "terraformed" by humans, thus creating the specific details such as Jacques' Eyes and the roads. He has also found and identified what he believes to be quarry marks and writing. To my eye, these don't look anything like quarry marks or writing. It's not a testable claim; the analysis simply comes down to personal opinion and interpretation. But it's certainly possible. Were there people living there 8-10,000 years ago?

From everything we know so far, the answer is no. Yonaguni is one of the Ryukyu Islands, of which Okinawa is the largest, and the earliest archaelogical evidence is that of the Late Shellmound phase which began only as recently as 300 BCE. The Ryukyu Islands are in deep water, at least 500m deep on all sides, and at no time during the last glacial age were the islands accessible by land bridge. This means that if any people were there when Yonaguni was on dry land, they did not stay, and they would have to have arrived by boat. This is something else we can check.

Nearby Taiwan has probably been populated since paleolithic times, tens of thousands of years ago, but the earliest population for which we have any evidence was the Dapendeng Culture which began 7,000 years ago. This is about the time that fishermen began to use canoes for coastal travel, about 5000 BCE. If the Dapendeng colonized Yonaguni, they would have had to have done so by boat. This cuts the timing very, very close. Yonaguni was probably already awash when the first Dapendeng canoes put to sea as glacial melt brought sea levels up. Of course, the studies which give us those dates could be wrong. But we do know that if the Dapendeng ever did colonize Yonaguni or the Ryukyus, they did not stay. Genetic studies have shown that the founding Ryukyu populations migrated southward from Japan, not from Taiwan.

So taking everything into account, the likelihood that prehistoric human hands ever had the opportunity to touch the stones of the Yonaguni Monument appears vanishingly small. The only evidence that they did is personal assessment of some fairly ambiguous undersea formations, none of which are geologically surprising, and all of which have analogs at known natural sites around the world. If the Yonaguni Monument is truly a Japanese Atlantis, it is a highly improbable one indeed.

By Brian Dunning

Please contact us with any corrections or feedback.


Cite this article:
Dunning, B. "Yonaguni Monument: The Japanese Atlantis." Skeptoid Podcast. Skeptoid Media, 24 Aug 2010. Web. 25 Nov 2015. <>


References & Further Reading

Chang, K. "The Formosa Strait in the Neolithic Period." Kaogu. 1 Jun. 1989, Number 6: 541-550, 569.

Hudson, M., Takamiya, H. "Dental pathology and subsistence change in late prehistoric Okinawa." Bulletin of the Indo-Pacific Prehistory Association. 1 Jan. 2001, Volume 21: 68-76.

Jiao, T. Lost Maritime Cultures: China and the Pacific. Honolulu: Bishop Museum Press, 2007.

Kimura, M. "Yonaguni." Marine Science and Cultural Heritage Research Association. Dr. Masaaki Kimura, 24 Oct. 2007. Web. 20 Aug. 2010. <>

Milne, G., Long, A., Bassett, S. "Modelling Holocene relative sea-level observations from the Caribbean and South America." Quaternary Science Reviews. 1 Jan. 2005, Volume 24, Numbers 10-11: 1183-1202.

Schoch, R. "An Enigmatic Ancient Underwater Structure off the Coast of Yonaguni Island, Japan." Circular Times. Dr. Colette M. Dowell, 19 Apr. 2006. Web. 20 Aug. 2010. <>


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