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Yonaguni Monument

Its origin is still disputed and that should be reported honestly: the marine geologist Masaaki Kimura, of the University of the Ryukyus, maintains after two decades of study that it was carved when the area was above water, around 10,000 years ago. Other specialists, such as Robert Schoch and Patrick D. Nunn, hold that it is entirely natural: the sandstone is crossed by parallel vertical joints that fracture the rock into rectangular blocks, and Yonaguni lies in a seismic region. There are similar stepped formations on land, at Sanninudai.