Ice Age Coastlines and the Lost Plains Around the Yonaguni Monument

Vast coastal plains once surrounded what is now open ocean.

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🤯 Did You Know (click to read)

At the height of the Ice Age, the Japanese archipelago was more connected to the Asian mainland due to lower sea levels.

During the Last Glacial Maximum, global sea levels were approximately 120 meters lower than today. The shallow continental shelf around Yonaguni Island would have been exposed as dry land. This transformation converted present-day seafloor into habitable plains potentially traversed by Paleolithic populations. Geological reconstructions show that land bridges and expanded shorelines were common across East Asia. The Yonaguni Monument lies well within this formerly exposed zone. If human modification occurred, it would have taken place on a terrestrial landscape rather than underwater. This Ice Age context fuels speculation about lost coastal settlements.

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💥 Impact (click to read)

The idea that entire landscapes vanished beneath rising seas destabilizes modern geographic intuition. What divers now explore as submerged stone may once have overlooked grassy plains or river valleys. The scale of transformation is continental, not local. Yonaguni’s depth aligns precisely with the drowned margins of the Ice Age world, placing it within a global narrative of submerged prehistory.

As researchers map other drowned shelves worldwide, similar debates emerge about early human occupation. Coastal archaeology increasingly acknowledges that some of humanity’s earliest settlements may now lie underwater. Yonaguni thus symbolizes a broader methodological challenge: reconstructing civilizations from terrain that no longer exists above sea level.

Source

NOAA Ocean Service

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