Earth is Eating Its Oceans Way Faster Than Originally Thought, Study Finds

At a Glance

• The Earth is eating its oceans far faster than originally thought, a new study says.
• Researchers found three times more ocean water is being sucked into the Earth's interior than estimated.

Three times more ocean water than originally thought is being swallowed by the Earth as the planet's tectonic plates sink below one another, a new study discovered.

Published in the journal Nature, a team of researchers took an estimate of how much water is being sucked into the Earth's interior through subduction zones — where two continental plates meet and one is being drawn downward.

Researchers used data recorded by seismographs along the Mariana Trench — a subduction zone where the Pacific Plate is subducted beneath the Philippine Plate — to analyze a year's worth of measurements that enabled them to draw a better picture of just how much water the rocks inside the plates could hold. The determination was made by recording the speed at which seismic waves travel through the rocks.

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Near the Mariana Trench, at least 4.3 times more ocean water is subducted than previously thought.

This discovery bodes large in understanding the Earth's deep water cycle, said Columbia University's Donna Shillington. A marine geology and geophysics researcher, Shillington said the water beneath the Earth's surface can aid in the development of magma and could lubricate faults, making earthquakes more likely.

Using velocity measurements stretching down to 18 miles below the surface in a combination of known temperatures and pressures, researchers were able to calculate that subduction zones swallow 3 billion teragrams of water into the crust every million years. A teragram is one trillion grams.

Unlike the old adage "what goes up must come down," the opposite applies here. Most of the water being subducted into the Earth is believed to be emitted back into the atmosphere as water vapor in volcanic eruptions, according to a Washington University release.

The amount of ocean water ingested by the Earth and the amount emitted isn't equal. In fact, the amount going in wildly exceeds the amount coming out.

There's no missing water in the oceans, Cai said, so there must be something about the way water moves through the Earth's interior that scientists don't understand.

"Many more studies need to be focused on this aspect," said Cai.

https://weather.com/news/news/2018-11-19-earth-eating-oceans-mariana-trench