Scientists have assembled the most accurate map of the geology beneath Earth’s southern hemisphere, revealing something never-before-seen: An ancient ocean floor may have curled around the center.

About 2,900 kilometers (1,800 miles) below the surface lies this thin, dense layer, the molten metallic outer core and the overlying rocky mantle, the core-mantle boundary (CMB).

In order to study everything from volcanic eruptions that protect us from solar radiation in space to variations in Earth’s magnetic field, understanding what lies beneath our feet in as much detail as possible is essential, according to Science Alert.

“Seismic studies like ours provide very high-resolution imaging of our planet’s internal structure, and we’re finding that the structure is much more complex than previously thought,” says Samantha Hansen, a geologist at the University of Alabama.

Hansen and his colleagues used 15 observatories buried in Antarctica’s ice to map seismic waves from earthquakes over a three-year period.

“By analyzing thousands of seismic records from Antarctica, our high-resolution imaging method has found thin, anomalous regions in the CMB everywhere we look,” says geophysicist Edward Carnero of Arizona State University. “Thickness of the material varies from a few. Kilometers to tens of kilometers.” This means that in some places we see mountains five times higher than Mount Everest.”

According to the researchers, this ULVZ is oceanic crust that has been buried for millions of years and is not near recognized subduction zones on the subducting crust surface, which are areas where moving tectonic plates push rocks down into the Earth. In the interior, the incoming simulations show how convection currents can move the ancient sea floor to where it is today.

It is difficult to make inferences about the types of rocks and their movement based on the movement of seismic waves, and researchers have not ruled out other options. However, the sea floor hypothesis is the most likely explanation for these ULVZs at this time

It is also thought that this ancient oceanic crust may have surrounded the entire core, although it is so thin that it is difficult to know for sure. Future seismic surveys can add more to the overall picture

One way the discovery could help geologists is to figure out how heat escapes from the hot, dense core into the crust. The differences in composition between these two layers are greater than between the solid surface rock in the region where we live and the air above.