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A new study suggests that plate tectonics – a scientific theory that divides the Earth into chunks of crust that move slowly over the viscous hot mantle – could have been active from the beginning of the planet. The new discoveries challenge earlier beliefs that tectonic plates have been developed over billions of years.
The paper, published in Scientific letters of the Earth and planets, has important implications in the fields of geochemistry and geophysics. For example, a better understanding of plate tectonics could help predict whether planets beyond our solar system could be inviting for life.
"Plate tectonics sets the conditions for life," said Nick Dygert, assistant professor of petrology and geochemistry at UT's Department of Earth and Planet Sciences and co-author of the study. "The more we know about ancient plate tectonics, the better we can understand how Earth has become as it is now."
For his research, Dygert and his team studied the distribution of two very specific isotopes of rare gases: helium-3 and neon-22. Noble gases are those that do not react to any other chemical element.
The previous models explained the current ratio of helium 3 / neon 22 of the Earth arguing that a series of large-scale impacts (like the one that produced our moon) resulted in oceans of massive magma, which degassed and gradually increased the ratio.
Dygert believes however that the scenario is unlikely.
"Although there is no conclusive evidence that this has not occurred," he said, "he could have only increased the ratio Helium-3 / Neon- 22 of the Earth under very specific conditions ".
Instead, Dygert and his team believe that the Helium-3 / Neon-22 ratio is increased in a different way.
As the earth's crust forms, the ratio of helium to neon in the mantle below the crust increases. By calculating this ratio in the crustal mantle and considering how this process would affect the bulk of the Earth over long periods of time, a rough chronology of Earth's tectonic plate cycle can be established.
"Helium 3 and neon 22 were produced during the formation of the solar system and not by any other means," Dygert said. "As such, they provide valuable information on the earliest conditions of the Earth and on subsequent geological activity."
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Material provided by University of Tennessee at Knoxville. Note: Content can be changed for style and length.
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