The ancient ocean floor surrounds the Earth’s core

A vast ocean floor likely surrounds much — if not all — of Earth’s core, according to a study is published In the journal “Science Advances”. This thin, dense layer lies about 3,200 kilometers below Earth’s surface, between the core and mantle, the middle layer of our planet. This layer may cover the entire core-mantle boundary, according to researchers led by Samantha Hansen, a professor in the Department of Geosciences at the University of Alabama.

To study Earth’s interior, seismologists measure seismic waves that are amplified as they travel through the planet and then return to its surface. By seeing how these waves change after they pass through various structures within the Earth, researchers can map the Earth’s interior even in its deepest depths. Previous research has identified a handful of isolated pockets of dense oceanic crust near the core. These pockets are called ultra-low velocity zone structures (ULVZs) because seismic waves travel through them very slowly. “Only 20% of the UVLZs were examined, and this non-smooth material appears to cover the entire core,” says Hansen.

This ancient ocean layer likely developed when Earth’s tectonic plates shifted, causing oceanic material to be transported into the planet’s interior at subduction zones, areas where two plates collide and cause one to sink under the other. Over time, the researchers report, “accumulations of submerged oceanic material build up along core-mantle boundaries and are pushed upwards by slowly flowing mantle rocks.” Researchers believe that the newly discovered ULVZs are essentially “underground mountains” that allow heat to escape from Earth’s molten core.

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