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Scientists discover 4 billion year old giant rocky continents near Earth’s mantle

Indian Express 2019-09-25 01:41:42
The image shows the divisions between Earth’s layers. The ancient, continent-sized rock regions encircle the liquid outer core. (Image source: Lawrence Livermore National Laboratory)

The underground rocky continents which are deep inside the Earth might have formed from an ancient magma ocean which got solidified during the starting of the formation of the Earth approximately 4.5 billion years ago, according to a new study.

The findings of the study were provided in a detailed article on the American Geophysical Union’s (AGU) GeoSpace blog.

The report said that the seismic waves of the earthquakes reverberate through the rest of the mantle which suggests they have distinct physical properties from the surrounding mantle. But the pattern changes when they reverberate through the massive giant stones. These different and peculiar patterns of the seismic activity aided the researchers to discover the continents that are located at the border of the mantle and the outer core of our planet. However, scientists still do not have any idea of how these rocky structures emerged.

A new analysis of volcanic rock provides a new picture. It says that these underground continents may be as old as our planet itself, and they most likely have survived the planet-rocking impact which formed the Moon, the study reported in the journal Geochemistry, Geophysics, Geosystems.

“It’s amazing that these regions have survived most of Earth’s volcanic history relatively untouched,” the GeoSpace report said quoting Curtis Williams, a geologist at University of California, Davis and the lead author of the study.

The researchers compiled new geological samples and used existing data of old samples taken from Hawaii and Iceland, and also from the Balleny Islands in Antarctica where insanely hot rock bubbles up from the planet’s core all the way to the surface. The samples break through the crust as lava, and cool into igneous rocks.

The rock samples that are from the Earth’s interior have isotopes such as helium-3, which means they were created during the Big Bang. The team identified samples which were having the primordial isotopes and then they attempted to retrace the path of the rocks to the surface.

Many geological models in the past assumed that the rock columns from the mantle known as deep mantle plumes had risen to the Earth’s surface in straight lines. However, these plumes have been known to change their path during their journey to the planet’s crust. the scientists have now developed a model which notes the deflecting nature of the deep mantle plumes and they were even able to trace some samples back to the giant underground continent masses near the core-mantle boundary.

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“It’s a more robust framework to try and answer these questions in terms of not making these assumptions of vertically rising material but rather to take into account how much deflection these plumes have seen,” the report said quoting Williams.