National Geographic: Ancient Seafloor from the Age of Dinosaurs Is Slowly Sinking into the Pacific Mantle

Beneath the vast Pacific Ocean, a hidden geological process is quietly erasing history: enormous slabs of seafloor that formed during the Jurᴀssic and Cretaceous Periods — the very era when dinosaurs ruled the land — are plunging deep into Earth’s mantle at subduction zones.

Seismic imaging and ocean-drilling data now show that the oldest Pacific crust, some of it 140–180 million years old, is being pulled beneath the Ring of Fire at rates of 5–10 cm per year. Trenches such as the Mariana, Tonga, and Kuril-Kamchatka are the final destinations for this ancient lithosphere. As the slabs descend more than 1,000 km into the mantle, they dehydrate and partially melt, powering the region’s violent volcanoes.

This process is not new, but advanced tomography has revealed it in unprecedented detail. The Pacific Plate acts as a giant conveyor belt: new crust is created at mid-ocean ridges while old crust is consumed at the edges. Much of the seafloor now disappearing was formed when dinosaurs still walked the Earth, and any rare terrestrial fossils it once carried — such as isolated Jurᴀssic theropod bones dredged from the Shatsky Rise — are being carried toward oblivion.

The implications extend beyond palaeontology. Subducted carbon and water influence long-term atmospheric CO₂ levels, while the disappearance of this ancient crust helps explain why the Pacific basin contains almost no pre-Cretaceous continental fragments.

From the deep trenches of the Pacific, the seafloor that witnessed the Age of Dinosaurs is vanishing — a dramatic reminder that Earth’s surface is in constant motion, recycling the very record of ancient life.