A long time ago, the outer layer of the Earth was broken into pieces, what we now call tectonic plates. In a new study, scientists investigated the origins of plate tectonics and found its history rooted on Earth.
About 4.5 billion years ago, our home planet was formed, and not too soon, about 3.2 billion years ago, the shell of Earth broke on these plates. Now, while scientists know how Earth’s tectonic plates move and move, exactly how they started has remained a mystery.
In a new study, led by planetary scientist Alexander Webb of the University of Hong Kong, in collaboration with an international team of researchers, scientists have come up with a new idea to explain why the Earth’s crust broke apart.
Related: Plate tectonics may have started a billion years after Earth was born.
According to the study, the Earth’s first outer layer, or lithosphere, heated up, causing it to expand and crack. This may seem like a simple explanation, but it contradicts many previous theories.
Previous studies have estimated that thermal expansion would be less likely to crack the Earth’s surface than thermal contraction, the opposite process by which the Earth’s outer layer shrinks as it cools. Because much of the Earth’s internal heat comes from radioactivityRadioactive decay would cause the planet’s interior to cool over time, those studies have suggested.
But, according to Webb, the answer to Earth’s tectonic origins “lies in considering the main heat loss mechanisms that could have occurred during Earth’s early periods.” he said in a statement. “If volcanic advection, which carried hot material from deep to the surface, was the primary mode of early heat loss, that changes everything.”
Here, Webb referred to a method of heat loss that involves volcanic advection, or the transfer of heat or matter through the movement of the fluid. In this process, the hot volcanic material would erupt and fall back to Earth as heat escaped into space and the material would cool and press against Earth’s young crust, creating a cooling effect. According to the statement, the cooled lithosphere “would have become increasingly heated through the conduction of the deep, hot material below.”
Webb’s team used 3D spherical models to simulate how Earth’s outer shell may have fractured in response to thermal expansion amidst variable heating and cooling in Earth’s early years. They found that while there was global cooling in Earth’s early years, the outer shell was heating up at the same time, which is the most likely cause of our planet’s crust breaking.
This work was published on July 17 in the journal Nature Communications.
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