Stunning megastructure discovered hidden beneath the Pacific

There's a strange slice of Planet Earth deep below the Pacific Ocean near Easter Island which may explain the East Pacific Rise, the world's fastest spreading ocean ridge, according to scientists.

There are ancient ocean slabs at this site hiding deep in the planet's interior which could be contributing to the spread and dates back to the time when dinosaurs roamed the planet.

University of Maryland geologist Jingchuan Wang and his team have been able to work this out using seismic data, reports Science Alert.

The scientists managed to identify an odd blob of mantle moving unexpectedly slow beneath the Nazca Plate that borders South America's continental plate by sending bouncing sound waves deep into the ground to form seismic maps.

The mantle makes most of Earth's volume and is made up of heated silicate rocks which are sandwiched together between a cool, thin outer crust and the core.

This layer flows in cycles over tens of millions of years due to the extreme difference in temperature at opposite edges with denser, cooler material drawn into the warmer interior.

This is called subduction and the Nazca Plate is currently subducting beneath South America, recycling surface material back into the mantle.

An illustration of how subduction works / Christoph Burgstedt, iStock

But on the other side of that plate underneath Easter Island is an ocean ridge that's growing rapidly and there's also a mysterious structural gap between the central and eastern Pacific.

Wang said: "Our discovery opens up new questions about how the deep Earth is influences what we see on the surface across vast distances and timescales.

"We found that in this region, the material was sinking at about half the speed we expected, which suggests the mantle transition zone can act like a barrier and slow down the movement of material through the Earth.

"This thickened area is like a fossilised fingerprint of an ancient piece of seafloor that subducted into the Earth approximately 250 million years ago.

"It's giving us a glimpse into Earth's past that we've never had before."

Wang and other scientists are improving their models of how tectonic plates have moved throughout Earth's history.

"This is just the beginning," he said.

"We believe there are many more ancient structures waiting to be discovered in Earth's deep interior. Each one has the potential to reveal many new insights about our planet's complex past - and even lead to a better understanding of other planets beyond ours."

This research was published in Science Advances.

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