The Ocean Is Sinking into Earth’s Mantle, and a Dead Supercontinent Is Partly to Blame

Live Science | 6/10/2019 | Staff
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The ocean is a big bathtub full of 326 million cubic miles (1.3 billion cubic kilometers) of water, and somebody has unplugged the drain.

It's not a perfect system; scientists think there's currently a lot more water plunging into the mantle than spewing out of it — but that's OK. Overall, this cycle is just one cog in the machine that determines whether the world's oceans rise or fall.

Study - May - Journal - Geochemistry - Geophysics

Now, in a study published May 17 in the journal Geochemistry, Geophysics and Geosystems, researchers report that this cog may be more improtant than previously thought. By modeling the fluxes in the deep water cycle over the last 230 million years, the study authors found that there were times in Earth's history when the gargantuan amount of water sinking into the mantle played an outsize role in sea level; during those times, the deep water cycle alone may have contributed to 430 feet (130 meters) of sea-level loss, thanks to one world-changing event: the breakup of the supercontinent Pangaea.

"The breakup of Pangaea was associated with a time of very rapid tectonic plate subduction," lead study author Krister Karlsen, a researcher at the Centre for Earth Evolution and Dynamics at the University of Oslo, told Live Science. "This led to a period of large water transport into the Earth, causing associated sea-level drop."

Years - Supercontinent - Pangaea - Landmass - Consisting

About 200 million years ago, the supercontinent Pangaea (a landmass consisting of all seven continents we know today) started to split, sending massive slabs of land careening in all directions.

As these continental plates spread apart, new oceans appeared (beginning with the Atlantic, roughly 175 million years ago), huge rifts in the seabed cracked open and ancient slabs of underwater crust plunged into the fresh voids. Gargantuan...
(Excerpt) Read more at: Live Science
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