The formation was discovered in 1987<\/a> by diving instructor Kihachiro Aratake, and quickly attracted the attention of geologists. It was, in a nutshell, unlike many other geological formations familiar to scientists, especially in its scale and unusually ordered appearance.<\/p>\n It consists of large slabs of stone, arranged in a way that resembles steps or terraces, with crisply squared edges and corners \u2013 shapes that are uncommon in natural settings at this scale, which have invited comparisons to stepped pyramids or ziggurats.<\/p>\n So striking was the appearance up close that geologist Masaaki Kimura of the University of the Ryukyus spent several years compiling a detailed argument<\/a> that the structure had been modified or constructed by human hands, before being submerged by rising seas around 10,000 years ago.<\/p>\n This view is highly controversial among his fellow geologists.<\/p>\n While relatively few peer-reviewed studies have focused directly on the Yonaguni formation, a broader body of geological evidence suggests that its strange, structured appearance can be explained by natural processes acting over thousands of years.<\/p>\n We know that our planet can make some remarkably geometric rocks.<\/p>\n The hexagonal columns of Ireland’s Giant’s Causeway<\/a> and Scotland’s Fingal’s Cave<\/a> are, literally, the stuff of legend<\/a>.<\/p>\n The Tessellated Pavement<\/a> of Tasmania, Australia, looks like neatly laid paving stones at the edge of the ocean, while the Al Naslaa rock<\/a> of Saudi Arabia is split by an astonishingly clean, straight fracture.<\/p>\n Meanwhile, Preikestolen<\/a> in Norway \u2013 Pulpit Rock \u2013 is famed for its sheer, flat geometry.<\/p>\n There are several natural geological features and processes relevant to the Yonaguni formation.<\/p>\n A bedding plane<\/a> is a natural layer in sedimentary rocks like sandstone and mudstone, the boundary where two deposition epochs meet, separating layers of rock with different properties. These are often flat planes and a natural point of weakness in a rock formation.<\/p>\n Perpendicular to these, rock formations can develop joint sets<\/a>. These are fractures in the formation, often parallel to one another<\/a>, that split open when the rock is stressed \u2013 under tremors, for example \u2013 separating the rock into surprisingly neat blocks<\/a>.<\/p>\n As noted<\/a> by geologist Robert Schoch of Boston University, who dived at the site in 1997, “Yonaguni lies in an earthquake-prone region; such earthquakes tend to fracture the rocks in a regular manner.”<\/p>\n Because Yonaguni lies in a fault zone<\/a>, it experiences significant tremor activity that could easily explain both the regularity of the fractures and the stepped formation.<\/p>\n When the ground shakes under the formation, the rocks break and slip away from each other at these natural weakness points \u2013 activity that can produce the shape of the Yonaguni Monument.<\/p>\n Meanwhile, the constantly moving ocean currents erode the fractures, separating the rocks from each other and scouring the surfaces flat.<\/p>\n Schoch also noted that nearby rock formations on Yonaguni Island, although rounded and more strongly eroded, were arranged in a similar manner to the underwater formation.<\/p>\n “Though the slope itself, now a tumult of ragged, fractured planes,” wrote the late author John Anthony West,<\/a> who explored with Schoch, “did not much look like the underwater formation we’d been studying, it was clear enough that it was basically the same geomorphology \u2013 just that the slope, exposed only to wind and rain, had taken on a very different and ragged appearance over thousands of years.”<\/p>\n![\"\"](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/01\/yonakuni-blocks.jpg\")
Some of the sandstone blocks at Yonaguni Monument. (Melkov\/Wikimedia Commons<\/a>, CC 1.0 Universal<\/a>)<\/p>\n![\"\"](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/01\/yonaguni-render.jpg\")
A render of the Yonaguni formation. (\u660e\u667a\u5149\u79c0\/YouTube<\/a>)<\/p>\n![\"Subscribe](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2025\/11\/Generic-Health-Promo-Final-642x273.jpg\")
<\/a><\/p>\n![\"\"](\"https:\/\/www.europesays.com\/us\/wp-content\/uploads\/2026\/01\/sunninadai.jpg\")
Rock formations at Sanninudai, Yonaguni Island. (Melkov\/Wikimedia Commons<\/a>, CC 1.0 Universal<\/a>)<\/p>\n