Oceans could also be shrinking — Science News, March 10, 1973
The oceans of the world could also be regularly shrinking, leaking slowly away into the Earth’s mantle…. Though the oceans are continually being slowly augmented by water carried up from Earth’s inside by volcanic exercise … some course of corresponding to sea-floor spreading appears to be letting the water seep away extra quickly than it’s changed.
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Scientists traced the ocean’s leak to subduction zones, areas the place tectonic plates collide and the heavier of the 2 sinks into the mantle. It’s nonetheless unclear how a lot water has cycled between the deep ocean and mantle by way of the ages. A 2019 evaluation means that sea ranges have dropped by an average of up to 130 meters over the past 230 million years, partly on account of Pangea’s breakup creating new subduction zones. In the meantime, molten rock that bubbles up from the mantle as continents drift aside could “rain” water back into the ocean, scientists reported in 2022. However since Earth’s mantle can hold more water because it cools (SN: 6/13/14), the oceans’ mass may shrink by 20 p.c each billion years.