Robots Mapped Alaska's Drowned First-American Caves

The Location

West of Prince of Wales Island in Southeast Alaska, the continental shelf was dry land when sea level was lower. Caves and rock shelters along that lost coast may have offered protection to people, animals and sediments more than 10,600 years ago. Today, their entrances lie underwater.

NOAA's Our Submerged Past final report documents a search through that drowned landscape. The project targeted places where evidence of early Indigenous presence and the Pacific coastal route into the Americas might have survived rising seas.

The coastline disappeared. The caves kept their address.

What's Down There

The expedition combined several tools because no single machine could move from open shelf to tight submerged chamber. Side-scan sonar searched wide areas, a small remotely operated vehicle inspected targets, and the hovering SUNFISH autonomous underwater vehicle entered and mapped complex spaces.

• Sonar identified possible caves and rock shelters.
• Robotic vehicles reduced the risk of exploring confined flooded passages.
• The team mapped interiors rather than stopping at the entrances.
• Sediment samples were recovered for archaeological and environmental analysis.

The project did not announce a confirmed settlement. Its achievement was to locate, enter and sample environments capable of preserving evidence that ordinary terrestrial archaeology cannot reach.

The History Above the Waterline

During the Late Pleistocene, lower sea level exposed parts of the shelf as a coastal landscape. That matters to the Pacific Coast Route hypothesis, which proposes that some early migrations into the Americas followed shores that were later submerged.

A drowned-site problem sits at the centre of that research: if people travelled along the ancient coast, many of their camps are now beyond the modern beach. Caves offer unusually protected targets where sediment, animal remains or cultural material could persist.

The Mystery

The maps narrow a huge search area, but sediment analysis must decide what the chambers preserved. Natural material can reconstruct the vanished environment; securely dated artefacts or human traces would be needed to establish occupation. Until then, these are promising archives, not proof of a migration route.

The oldest American coast is not missing from the planet. It is simply underneath the newer one.