18:21 GMT16 April 2021
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    New findings by the geologists call into question the theory that tectonic plates are driven by the weight of their sinking portions, with an underlying, hot layer serving as no more than a passive lubricant.

    Geologists have revealed the results of a recent study that suggests flows in the softer layer under tectonic plates are stronger and faster than originally believed.

    A team of scientists from the University of Houston are now questioning the long-supported theory that a softer, hot layer, called asthenosphere, hidden underneath tectonic plates that are set into motion under the weight of their sinking portions, serves as a passive lubricant.

    If corroborated, the findings show that the layer in question actually flows vigorously, its movement also fast enough to drive plate motions.

    ​While conducting the research, details of which were published in Nature Communications, the team from the UH College of Natural Sciences and Mathematics considered minute changes in satellite-detected gravitational pull within the Caribbean, as well as scrutinising mantle tomography images of the asthenosphere under the Caribbean.

    ​What they discovered was a hot "river of rocks" being squeezed from the Pacific Ocean through a ‘gateway’. This underground flow stretched under Central America to reach the middle of the Caribbean Sea.

    The "river of rocks" dates eight million years back, when the Central American gateway - a body of water that once separated North America from South America - opened, uplifting the seafloor over it by several hundred feet. In the process, the flow was tilted to the northeast toward the Lesser Antilles.

    "Without the extra support generated by this flow in the asthenosphere, portions of Central America would still be below sea level. The Atlantic and the Pacific Oceans would be connected without a need for the Panama Canal," study co-author Lorenzo Colli, assistant professor of geophysics, geodynamics and mantle structure in the Department of Earth and Atmospheric Sciences, was quoted as saying by Phys.org.

    Furthermore, the asthenosphere is revealed to be moving six inches annually - three times faster than an average plate. The movement can be perceived as independent from the overlying plates, dragging the latter in a different direction.

    "Think of the plates moving like an air hockey puck and being lubricated from below. Instead, what we found is the air hockey table is imposing its own currents on the puck that's moving around, creating a bottom-up movement that has not been well recognised, and that's being quantified here, “ said Jonny Wu, study co-author and assistant professor of structural geology, tectonics and mantle structure.

    He hailed the results of the research, emphasising that the findings challenge the “top-down notion that subduction is always the driver."

    People gather near a collapsed house after a major earthquake in Kathmandu, Nepal April 25, 2015. A shallow earthquake measuring 7.9 magnitude struck west of the ancient Nepali capital of Kathmandu on Saturday, killing more than 100 people, injuring hundreds and leaving a pall over the valley, doctors and witnesses said.
    © REUTERS / Navesh Chitrakar
    Earthquake in Nepal

    As for the overall implications of the research, it is acknowledged as invaluable in further understanding the shape of the Earth's surface, its evolution over time through a pattern of emerging shallows seas, low-lying land bridges and moving tectonic plates that trigger earthquakes

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    Tags:
    University of Houston, Earthquakes, earthquake, earthquake, Caribbean Sea, Caribbean
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