The internal structure of Earth continues to reveal details that reshape established scientific explanations about the planet’s formation. One such development relates to the origin and distribution of water. For decades, the dominant explanation held that water was delivered to Earth by icy comets during its early history. However, geological and seismic research presents a more complex picture. Current evidence suggests that a large amount of water may reside within the Earth’s mantle, far below the Earth’s crust. According to Brookhaven National Laboratory, located about 700 kilometers below the Earth’s crust, this store of water is not in a liquid state, but is locked within minerals. Its potential volume is enormous, even greater than all the oceans on the Earth’s crust combined, which has reinvigorated research on the Earth’s water cycle.
Why Earth’s ‘hidden ocean’ isn’t liquid: Water trapped in ringwoodite explained
The term ocean is often used informally to describe this body of water, although it is entirely distinct from surface bodies of water. As BNL reports, the water exists within a high-pressure mineral known as ringwoodite, which forms under extreme conditions in the mantle. In this state, water is chemically bound within the crystal structure of the mineral rather than existing as a free-flowing liquid.Laboratory experiments simulating mantle conditions have confirmed that ringwoodite may contain significant amounts of water. When extrapolated, the total amount becomes substantial. This form of storage represents a stable and long-term component of the Earth’s internal system.
Revisiting the origins 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 implies that rather than acquiring water from external sources such as comets, it has been part of the planet since its formation. Internal water may rise to the surface over time through volcanic activity. This theory is consistent with the observation that the amount of water in the oceans remains constant over time.
Seismic evidence shows there is water in the Earth’s mantle
Direct exploration of depths up to 700 kilometers is beyond current technical capabilities. As a result, scientists rely on indirect methods, especially seismic analysis. Waves generated by earthquakes travel through the planet and change speed depending on the materials they encounter. In some areas, seismic waves have been observed to slow down, a characteristic often associated with the presence of water within minerals. These observations, collected through an extensive seismometer network, provided the initial evidence for water in the mantle.That’s according to Schmandt and Jacobsen’s findings, which are based on a finding reported in the journal NatureFurther support comes from laboratory experiments and analysis of ringwoodite samples found within diamonds brought to the surface by volcanic eruptions. These samples contained measurable amounts of water, confirming theoretical predictions.
