oceans may shrink , science newsMarch 10, 1973
The world’s oceans are slowly shrinking, slowly seeping into the Earth’s mantle…. However the oceans are being continually enlarged slowly by water brought up from the Earth’s interior by volcanic activity… some process such as sea level spreading allows the water to seep in more rapidly than it can be replaced.
The scientists traced the ocean leak to subduction zones, regions where tectonic plates collide and the heavier mantle sinks into the two. It is still unclear how much water has cycled between the deep ocean and the mantle over the eons. A 2019 analysis shows that sea level is dropped by an average of 130 meters Over the last 230 million years, the breakup of Pangea led to the formation of new subduction zones. Meanwhile, molten rock that rises from the mantle as the continents drift apart “rain” water drains back into the oceanScientists reported in 2022. but since Earth’s mantle can hold more water as it cools (Sn: 6/13/14), the mass of the oceans could decrease by as much as 20 percent every billion years.