Earth’s internal structure continues to reveal details that reshape established scientific explanations about the planet’s formation. One such development concerns the origin and distribution of water.
For decades, the prevailing explanation was that water reached Earth via icy comets during its early history. However, geological and seismic research presents a more complex picture. Current evidence suggests that a significant amount of water may be present deep within the Earth’s mantle, well below the Earth’s crust. Located about 700 kilometers beneath the Earth’s crust, this body of water is not in a liquid state but is instead trapped within minerals, according to Brookhaven National Laboratory.
Its potential size is large, and even exceeds the size of all the oceans on the Earth’s crust, which revitalizes research related to the water cycle on Earth.
Why Earth’s ‘hidden ocean’ isn’t liquid: Water trapped in ringwoodite explained
The term ocean is often used informally to describe this reservoir, although it is quite different from bodies of surface water. According to BNL reports, the water is contained within a high-pressure mineral known as ringwoodite, which forms under extreme conditions in the mantle.
In this case, the water is chemically bound within the crystalline structure of the mineral rather than existing as a free flowing liquid.Laboratory experiments simulating mantle conditions have confirmed that ringwoodite can contain significant amounts of water. When extrapolated across, the total size becomes large. This type of storage represents a stable, long-term component of the Earth’s internal system.
Reconsidering the origin of Earth’s water
The presence of water in the deep mantle supports the theory that the Earth has retained its water since its formation. The theory suggests that instead of getting water from external sources such as comets, it has been part of the planet since its formation. It is possible that inland waters may have moved toward the surface over time through volcanic activity. The theory is consistent with observations that the volume of water in the oceans has remained constant over time.
Seismic evidence reveals water in the Earth’s mantle
Direct exploration to depths approaching 700 km still exceeds current technological capabilities. As a result, scientists rely on indirect methods, especially seismic analysis. Waves from earthquakes travel through the planet and change their speed depending on the materials they encounter. In some areas, seismic waves have been observed to slow down, a property often associated with the presence of water within minerals.
These observations, collected through large-scale seismic networks, provided initial evidence for the presence of water in the mantle.According to Schmandt and Jacobsen’s findings, which are based on a discovery published in the journal Nature, further support comes from laboratory experiments and analysis of ringwoodite samples found inside diamonds brought to the surface by volcanic eruptions. These samples contained measurable amounts of water, confirming theoretical predictions.