Seismic imaging uncovers ancient ocean floor around Earth's core.

Seismic imaging has revealed that a thin, dense layer of ancient ocean floor likely surrounds much, if not all, of the Earth's core. This layer is lodged roughly 2,000 miles below the Earth's surface, between the core and the mantle, and may encompass the entire core-mantle boundary. The layer likely developed when Earth's tectonic plates shifted, causing oceanic material to be carried into the planet's interior at subduction zones. The ULVZs are essentially "underground mountains" that allow heat to escape from Earth's molten core and could buffer heat flow across the core-mantle boundary, which is important because the temperature conditions in this portion of the Earth have been shown to strongly impact the planet's magnetic field.