Geologists conclude Yonaguni's offshore 'steps' follow natural sandstone joints

October 23, 2026

JapanGeneral

Underwater structuresUndated

Source: 10 Ancient "Artifacts" That Turned Out To Be Natural by World of Antiquity

Site mentioned

📍 Yonaguni Monument🗺️ More sites in Japan 🌍 Show on the globe

Wolf Wickman and Robert Schoch both interpreted the Yonaguni Monument's offshore 'steps' as natural. Wickman found that they follow sandstone layers and break at weak points, some 3–16 ft high, and a 2020 regional study agreed — undercutting Masaki Kimura's claimed 10,000-year castle. 🏝️

Key facts

Off the Japanese island of Yonaguni, a submerged sandstone formation has broad terraces, straight edges and sheer faces resembling masonry steps.
Masaki Kimura argued that it is a human-built structure resembling an Okinawan castle, proposed an age of about 10,000 years, and cited purported tools and an engraved stone as evidence.
Geologist Robert M. Schoch made dozens of dives and said horizontal bedding and vertical joints produce the large steps; photographs of onshore bedrock showed similarly clean breaks.
Geologist Wolf Wickman independently concluded that it is natural, finding that the steps follow sandstone layers and coincide with weak points, with some roughly 3–16 feet high.
A regional geological study published in 2020 compared angular island rock with the submerged formation and attributed its shape to weathering and erosion controlled by sandstone layering and straight joints.
Schoch considered the formation predominantly natural. Later human use or modification remains possible, while Kimura's purported tools and engraved stone still require examination.