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Deep Earth Water Reservoir Discovered in Mantle Transition Zone

  //science-technology.news-articles.net/content/2 .. ervoir-discovered-in-mantle-transition-zone.html
  Published in Science and Technology on Sunday, April 26th 2026 at 1:23 GMT by AFP
      Locale: UKRAINE

The Architecture of the Deep Earth

The focus of this discovery is the "transition zone," a region of the mantle located between approximately 410 and 660 kilometers below the surface. This zone acts as a buffer between the upper and lower mantle. While the mantle is composed of solid rock, it behaves plastically over geological timescales. Within this specific depth, scientists have identified the presence of ringwoodite, a high-pressure polymorph of olivine.

Ringwoodite possesses a unique chemical property: it acts as a sponge. Under the extreme pressure and temperature conditions of the transition zone, ringwoodite can trap hydrogen and oxygen atoms within its crystal lattice. This is not water in the traditional sense--there are no underground oceans or flowing rivers--but rather water locked into the mineral's structure as hydroxyl groups.

The Evidence: Seismic Waves and Diamonds

Researchers have utilized two primary methods to confirm the existence of this reservoir. The first involves seismic tomography. By analyzing the speed and behavior of seismic waves generated by earthquakes, geologists noticed a significant slowdown in wave velocity within the transition zone. This attenuation is characteristic of materials containing water or volatiles, suggesting a saturated layer of rock.

The second, more direct piece of evidence came from the study of "deep-mantle diamonds." Diamonds are formed under immense pressure and can occasionally trap tiny fragments of the surrounding environment as inclusions. Some diamonds that reached the surface via volcanic eruptions contained microscopic grains of ringwoodite. Upon analysis, these grains were found to be rich in water, providing a physical sample of the chemistry occurring hundreds of kilometers below the crust.

Key Scientific Details

• Location: The reservoir is situated in the transition zone, roughly 410 to 660 kilometers beneath the Earth's surface.
• Mineral Component: The primary agent for water storage is ringwoodite, a mineral that becomes stable only under extreme pressure.
• Physical State: The water is not liquid; it is molecularly bound within the crystal structure of the rock.
• Estimated Volume: Some estimates suggest that if the transition zone is fully saturated, it could contain as much as three times the volume of all the world's surface oceans combined.
• Mechanism of Transport: This water is believed to be part of a "Whole Earth Water Cycle," where water is carried down into the mantle via subducting tectonic plates and eventually returns to the surface through volcanic activity.

Implications for Planetary Science

The existence of this deep-earth reservoir fundamentally alters the understanding of the global water cycle. For years, the prevailing theory was that Earth's water arrived primarily via comet impacts during the planet's early formation. However, the presence of such a vast internal reservoir suggests that a significant portion of the planet's water may have originated from the interior and been released slowly over billions of years.

Furthermore, the presence of water in the mantle influences the viscosity of the rock. Saturated rock is more "slippery" than dry rock, which has direct implications for mantle convection and the movement of tectonic plates. This suggests that the deep-water reservoir is not merely a passive storage tank, but an active participant in the geological processes that shape the Earth's surface, drive volcanic eruptions, and trigger earthquakes.

By shifting the perspective from a surface-centric water model to a holistic planetary model, scientists are beginning to realize that the surface oceans may simply be the visible tip of a much larger, hidden hydrological system.