Дэлхийн гүнд асар их хэмжээний ус агуулсан чулуулгийн давхарга илэрлээ

A layer of rock roughly 700 kilometers below Earth’s surface contains water locked inside minerals under extreme pressure and heat. The material is not a liquid ocean flowing through open caverns. Instead, hydrogen and oxygen are incorporated into the crystal structure of deep mantle minerals, creating a vast reservoir within solid rock.

Evidence for this deep water reservoir comes from earthquake measurements, high-pressure laboratory experiments, and a tiny mineral sample carried to the surface inside a diamond. A study published in Science connected unusual melting near the top of the lower mantle with water released from ringwoodite, a mineral found in a layer known as the mantle transition zone.

Ringwoodite Holds Water Inside Solid Rock

Ringwoodite is a high-pressure form of olivine, one of the main minerals in Earth’s upper mantle. It forms at depths of about 410 to 660 kilometers, where pressure forces atoms into a denser arrangement. Its crystal structure can hold hydroxyl, a chemical group made from hydrogen and oxygen, within the solid mineral.

Steven Jacobsen, a geophysicist at Northwestern University, compared the mineral to a sponge because of its ability to take in hydrogen. “The ringwoodite is like a sponge, soaking up water,” he said in a Northwestern University account of the research. “There is something very special about the crystal structure of ringwoodite that allows it to attract hydrogen and trap water.”

The term “water” can be misleading in this setting. The reservoir contains no underground shoreline or freely moving sea. Under mantle conditions, water molecules split, and hydroxyl becomes chemically bound within the mineral. The rock remains solid until changing pressure and temperature cause some of the stored water to escape.

Laboratory samples show that ringwoodite can contain more than one percent water by weight. If rock throughout the transition zone held that concentration, the total would be comparable to nearly three times the water in Earth’s surface oceans. That figure describes the possible storage capacity of a vast layer of mantle rock, not the discovery of a single liquid body beneath the planet.

Earthquake Waves Detected Deep Mantle Melting

The Science research combined laboratory work with seismic observations from the USArray, a network of more than 2,000 instruments spread across the United States. The team examined seismic waves produced by earthquakes as they traveled through different layers of Earth.

Seismic waves change speed when they pass through rock with different temperatures, densities, or amounts of melt. The researchers detected signs of partial melting near the boundary between the transition zone and the lower mantle. The pattern occurred in areas where mantle material appeared to be moving downward.

Jacobsen recreated those conditions by compressing synthetic ringwoodite between small diamonds and heating it to temperatures found deep inside Earth. The experiments produced small amounts of melt at pressures corresponding to the lower edge of the transition zone. These laboratory results matched the type of seismic signal detected beneath North America.

The process is called dehydration melting. When ringwoodite moves deeper, it changes into minerals that cannot retain as much water. The excess water leaves the crystal structure and lowers the temperature at which nearby rock begins to melt.

“When a rock with a lot of H2O moves from the transition zone to the lower mantle it needs to get rid of the H2O somehow, so it melts a little bit,” University of New Mexico seismologist Brandon Schmandt explained in the Northwestern report. “This is called dehydration melting.”

Only a small fraction of the rock needs to melt for instruments to detect it. According to the research account, about one percent melt can slow seismic waves enough to produce a measurable signal. The observations covered a broad region beneath the United States and identified melting at depths where water-bearing ringwoodite would transform into lower-mantle minerals.

A Diamond Carried Ringwoodite to the Surface

A separate discovery provided a physical sample of water-bearing ringwoodite from the mantle. A team led by Graham Pearson of the University of Alberta examined a small diamond from Juína, Brazil. Inside it, researchers found a microscopic piece of ringwoodite.

The diamond formed deep underground and later reached the surface in volcanic material. Its strong crystal structure protected the inclusion during the journey upward. Without that protection, ringwoodite would normally change into another mineral as pressure decreased, leaving no intact sample for scientists to study.

Analysis showed that the inclusion contained about 1.5 percent water by weight. The sample offered direct evidence that natural ringwoodite in the transition zone can store water. The research appeared in Nature shortly before the seismic and laboratory study reported in Science.

Pearson later said that researchers had identified another water-bearing ringwoodite crystal. “Since our initial report of hydrous ringwoodite, we’ve found another ringwoodite crystal, also containing water, so the evidence is now very strong,” he said.

Frank Brenker, a geoscientist at Goethe University Frankfurt, was part of the diamond research team. Work on mineral inclusions in diamonds allows scientists to examine materials formed far deeper than conventional drilling can reach. These tiny trapped samples preserve information about the chemistry and mineral structure of Earth’s interior.

The combined findings place water within the mantle transition zone, the layer between the upper and lower mantle. Seismic measurements identified melting near its lower boundary, laboratory experiments reproduced the process, and the diamond inclusion showed that naturally formed ringwoodite can carry water inside its crystal structure.

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