For centuries, humanity believed Earth's water was confined to its surface. But new research has unveiled a groundbreaking revelation: a vast hidden ocean lies buried 700 kilometres beneath the Earth’s surface, deep within the mantle. This discovery, led by a team from Northwestern University, raises questions about the planet’s water cycle and challenges long-held assumptions about the origins of Earth’s water.

Ringwoodite: The Key to Earth’s Mantle Water

Scientists estimate this underground reservoir could be three times larger than all the oceans combined. However, unlike surface oceans, this "hidden ocean" isn't made up of liquid water. Instead, the water is locked within the crystal structure of a rare blue rock known as ringwoodite, found deep within the mantle.

The research team, led by Steven Jacobsen, used over 2,000 seismographs stationed across the U.S. to track seismic waves from more than 500 earthquakes. These seismic waves slowed down significantly at certain depths, signalling the presence of water-rich rocks. By measuring the speed of these waves at different depths, the scientists could infer the existence of water trapped inside the mantle.

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Implications for Earth's Water Cycle and Origins

This seismic discovery suggests Earth’s water cycle might have deeper origins than previously thought. Traditionally, it was believed that water came from comets striking the Earth. Now, scientists are considering that water could have seeped up from Earth's interior over millions of years.

The implications of this finding are far-reaching. This underground ocean may play a crucial role in regulating the long-term stability of Earth’s surface water, potentially cycling water between the planet's surface and its interior. Further studies are now planned to determine whether similar water reservoirs exist elsewhere in the world, which could reshape our understanding of the planet’s water distribution.

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