The first continents were recycled in the Earth’s mantle


An international research team has discovered that the first continents were not stable and were recycled inside the Earth, in the mantle

The study, published in Proceedings of the National Academy of Sciences (PNAS), it is important because it provides important clues about how the planets formed.

“The rocks at the core of the continents, called cratons, are more than three billion years old,” he explains. it’s a statement the study’s lead author, Associate Professor Fabio Capitanio from Monash University’s School of Earth, Atmosphere and Environment. “They formed on early Earth and hold the secret of how the continents and the planet changed over time.”

The researchers used high-performance computational models to simulate the evolution of the first billion years of the Earth. They discovered that the first continents were unstable and recycled in the Earth’s mantle.

Once the first continental blocks were in the mantle, they melted, churned, and mixed until they disappeared.

The researchers discovered that some pieces of the original rocks can remain in the mantle for billions of years, but eventually they reappear.

“Our work is important in two ways,” Capitanio said. “First, cratons are where important metals and other minerals are stored or found. And second, they tell us how the planets formed and changed in the pastincluding how the continents formed and how they supported life, and how the atmosphere formed and changed as a result of the tectonics of the planets.”

Over time, the recycled pieces of the continent can accumulate under the new lithosphere, making it more buoyant and strong enough to stop further recycling.

Study is unique because it explains how continents come together, authors say. Many observations of ancient continental cores, called cratons, show that they are much more complex and heterogeneous than today’s lithosphere. However, scientists did not know what caused the differences or how they formed.

The study shows that parts of the lithospheric cratonic mantle (CLM) still exist in the mantle as diffuse, depleted heterogeneities on multiple scales. that can last billions of years.

Relamination works best with high degrees of depletion and mantle temperatures that are similar to those of the early Earth. This leads to the upwelling and sublayering of large amounts of submerged CLM, which is known as massive regional relamination (MRR).

MRR accounts for the complex heterogeneities of origin, age, and depletion found in old CLM. This suggests that this it may have been a key part of building continents on early Earth.

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