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An international team of geophysicists has found evidence that the Earth experienced plate tectonics earlier than previously thought. In their , published in the Proceedings of the National Academy of Sciences, the group analyzed zircons from Jack Hills in Australia.

Currently, most scientists believe that plate tectonics began on Earth approximately 3 billion years ago鈥攁round 1.5 billion years after the Earth was formed. In this new effort, the research team found evidence suggesting it may go as far back as more than 4 billion years ago.

The researchers analyzed zircons鈥攁 type of crystal believed to be the oldest material on Earth. Some of those retrieved from Jack Hills have been dated to 4.3 billion years ago. Prior research has shown that zircons can be created in two ways鈥攂y crystalizing out of magma directly, and from the erosion of sedimentary rock that washes into the ocean, which is absorbed back into the mantel and resurfaces in granite. The second type is known as S-type.

The two types of zircons can be distinguished by the mica content in S-type samples鈥攖he mica comes from sedimentary rock. Unfortunately, a single sample does not provide enough information to provide any historical significance鈥攊t is only when many samples are studied and then compared that a story may emerge.

Such work is difficult, however, which is why the team on this new effort built an AI application that could do the work for them. After training on a host of S-type samples, the app showed them that a third of the samples they had in their collection were S-type and they averaged 4.2 billion years old. That finding suggested that land rose above the sea at that time.

The AI app also showed a cycle of changes to the zircons over time that suggested they had experienced continental changes likely associated with plate tectonics.

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