The hot mantle of the early Earth contributed to a larger volume of oceans

(4-3.2 billion years ago) were larger than they are now. The hot mantle of the early Earth contributed to a larger volume of oceans.

The hot mantle of the early Earth contributed to a larger volume of oceans
The hot mantle of the early Earth contributed to a larger volume of oceans

The researchers calculated the storage capacity of water in the Earth's solid mantle depending on its temperature. Because the early mantle was hotter, scientists conclude that the Earth's oceans of the early Archean eon (4-3.2 billion years ago) were larger than they are now. The hot mantle of the early Earth contributed to a larger volume of oceans.

How have the volumes of the Earth's oceans changed?

Water was delivered to Earth by meteorites and comets, even when it was in the process of increasing its material or shortly thereafter. Then there was an energetic volcanic degassing, and water was released from the early mantle of the Earth, which may have led to the formation of primitive oceans. Sometime after the beginning of plate tectonics, the mantle became saturated with water again and began to change the relative water content on the surface. There is evidence that the level of elevation of the continents above the sea was approximately constant throughout the Phanerozoic (from 541 million years ago to the present). However, the proportions of water and land on Earth could have been completely different earlier, especially in the early Archaea (4“3.2 billion years ago). Rare isotopic records of the early Archean eon can be used to indirectly limit the size of the early oceans. So scientists were able to learn that these oceans were larger than modern ones.

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What did the scientists analyze?

Previous studies have shown that surface water could be constantly transported to deep areas of the mantle, where there is potentially a reservoir of water in the form of hydrogen and oxygen included in the minerals. Exactly how much water can be stored there is unknown. To find out, the researchers conducted experiments with the main rock-forming materials: olivine, wadsleyite and ringwoodite, and quantified the effects of pressure and temperature on them. The team also calculated the possible storage capacity of water in bridgemanite at different temperatures depending on the depth. Thus, scientists have been able to establish a model of water storage capacity for the Earth's solid mantle as a function of temperature.

What did the results show?

The water storage capacity of the Earth's solid mantle was significantly affected by cooling due to the fact that the temperature determines which minerals are part of it. The current mantle water storage capacity, according to the team's estimates, is 1.86-4.41 oceans mass. This value is consistent with geochemical estimates of current water content. For the solid mantle of the early Earth, whose temperature was higher, the capacity was lower and was only 0.52“1.69 ocean mass.Thus, the surface of the early Earth was more covered with water than now. Moreover, geological records from the early Archean eon point to a global surface ocean with little or no land. Significantly water-covered early surface of the Earth would have a lower albedo than now, which could affect surface temperatures during this period of reduced solar flux, when the first life may have appeared on the planet.