New study suggests gigantic masses in Earth's mantle untouched for more than 4 billion years

phys.org | 9/16/2019 | Staff
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Ancient, distinct, continent-sized regions of rocks, isolated since before the collision that created the Moon 4.5 billion years ago, exist hundreds of miles below the Earth's crust, offering a window into the building blocks of our planet, according to new research.

The new study in the AGU journal Geochemistry, Geophysics, Geosystems used models to trace the location and origin of volcanic rock samples found throughout the world back to two solid continents in the deep mantle. The new research suggests the specific giant rock regions have existed for 4.5 billion years, since Earth's beginning.

Scientists - Continents - Mantle - Plates - Study

Previously, scientists theorized that separated continents in the deep mantle came from subducted oceanic plates. But the new study indicates these distinct regions may have been formed from an ancient magma ocean that solidified during the beginning of Earth's formation and may have survived the massive Moon-creating impact.

Determining the masses' origin reveals more details about their evolution and composition, as well as clues about primordial Earth's history in the early Solar System, according to the study's authors.

Regions - Earth - History - Curtis - Williams

It's amazing that these regions have survived most of Earth's volcanic history relatively untouched, said Curtis Williams, a geologist at the University of California, Davis, in Davis, California and lead author of the study.

The mantle is a layer of rock, stretching 2,900 kilometers (1,802 miles) down inside the Earth. Earth's molten, liquid, metallic core lies beneath the mantle. The core-mantle boundary is where the solid mantle meets the metallic liquid core.

Scientists - Imaging - Studies - Rock - Bodies

Scientists knew from past seismic imaging studies that two individual rock bodies existed near the core-mantle boundary. One solid rock body is under Africa and the other is under the Pacific Ocean.

Seismic waves, the vibrations produced by earthquakes, move differently through these masses than the rest of the mantle, suggesting they have distinct physical properties from the surrounding mantle. But geologists couldn't...
(Excerpt) Read more at: phys.org
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