Жапония жағалауындағы батқан тас құрылымдар

Submerged rock formation off the coast of Japan

The Yonaguni Monument (与那国島海底地形), also known as "Yonaguni (Island) Submarine Ruins", is a submerged rock formation off the coast of Yonaguni, the southernmost of the Ryukyu Islands, in Japan. It lies approximately east of Taiwan. Marine geologist Masaaki Kimura claims that the formations are man made stepped monoliths. These claims have been described as pseudoarchaeological. Neither the Japanese Agency for Cultural Affairs nor the government of Okinawa Prefecture recognise the features as important cultural artifacts and neither government agency has carried out research or preservation work on the site.

The sea off Yonaguni is a popular diving location during the winter months because of its large population of hammerhead sharks. In 1986, while seeking to observe the sharks, Kihachiro Aratake, a director of the Yonaguni Cho Tourism Association, noticed some seabed formations resembling architectural structures. Shortly thereafter, a group of scientists directed by Masaaki Kimura of the University of the Ryūkyūs visited the formations. The formation has since become a relatively popular attraction for divers despite strong currents.

The formations are located below Arakawabana (新川鼻; Yonaguni: Araga bana) cliff which is the southern tip of Yonaguni island, with its main face oriented south southeast. It is composed of medium to very fine sandstones and mudstones of the Lower Miocene Yaeyama Group believed to have been deposited about 20 million years ago. Most of the rocks in the formations are connected to the underlying rock mass (as opposed to being assembled out of freestanding rocks).

Geologist Robert Schoch believes that it is most likely natural. John Anthony West visited the formation with Schoch and agreed that it was a natural formation and that Kimura "had not looked carefully enough at the natural processes at work." At Sanninudai, there are onshore step like sandstone formations similar to those of the Yonaguni. Robert Schoch, as well as Patrick D. Nunn, Professor of Oceanic Geoscience at the University of the South Pacific, note that the formations are purely natural. In 2019, Takayuki Ogata and other researchers conducted a topographical analysis of Yonaguni Island using a digital elevation model and geological field investigations of the strata, rocks, and microtopography of outcrops at three locations, known as "geosites", Tindabana, Kube Ryofurishi, and Sanninudai. As a result of their research, they noted that although Yonaguni Monument may look like an artificial construction, it is a natural feature formed by the weathering and erosional processes acting on bedding and linear joints in sandstone. They noted that similar features can be found at Sanninudai geosite and commonly observed on the south coast of Yonaguni Island.

Kimura first estimated that the formation must be at least 10,000 years old, dating it to a period when it would have been above water, and therefore surmised that the site may be a remnant of the mythical lost continent of Mu. In a report given to the 21st Pacific Science Congress in 2007, he revised this estimate and dated it to 2,000 to 3,000 years ago because the sea level then was close to current levels. He suggested that after construction, tectonic activity caused it to be submerged below sea level. Archaeologist Richard J. Pearson believes this to be unlikely.