The first continents appeared 700 million years earlier than we thought

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The formation of the first stable landscape, known as the Croton, began about 2.5 billion years ago, and is believed to have been driven by the motion of tectonic plates. But a recent analysis of the sediments found in eastern India indicates that they actually appeared 3.3 to 3.2 billion years ago, 700 million years earlier than expected.

The appearance of continents has had a major impact on the atmosphere, climate, marine formation and especially the distribution of life on Earth. In fact, land erosion was the main source of nutrients for the first organisms to settle in coastal environments. ” Providing these nutrients to the Earth’s early oceans is essential for creating and preserving the first forms of life. Priyadarshi Chaudhary, a geographer and co-professor of research at Monash University in Melbourne, said.

In addition, the oxygen provided by these primitive organisms in photosynthesis eventually helped to create the oxygen-rich atmosphere we live in today. The origin of the continents was a turning point in the history of our planet. ” It is important to understand when and how the subtropical crust first formed, as it plays an important role in establishing the Earth’s habitat. “The researchers focused on the ancient continents found in India, Australia and South Africa,” he said.

The elevation technique is different from the current process

As the continents rise, they begin to erode under the influence of rain and wind; The rocks turn into sand particles carried by rivers and eventually accumulate on the shores, forming beaches. It has been like that for millions of years. Therefore, by examining the rock records of ancient sand deposits, geologists can study earlier periods of continental formation.

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Singbum Groton, an ancient part of the Continental crust in India, has many ancient sandstone formations. These various layers of sand were glazed over beaches, estuaries and rivers, buried in rock and pressed. Scientists have determined the age of these deposits by dating them to zirconium and lead – there are traces of uranium in the zircon grains in the sandstone center, which will lead over time.

However, the analysis found that the sedimentary rocks were deposited about 3 billion years ago, at the same time suggesting the creation of a landscape at the level of present-day India. Accurate team Sedimentary rocks of the same age are also found in the oldest crotons of Australia (Bilbara velcorn crotons) and South Africa (cupwall crotons); So, at this time many landscapes around the world may have appeared.

What are the mechanisms by which these crotons escape from the water, by what means? Today it is very different from the processes that cause the appearance of the subtropical overlay Jacob Mulder, a geologist at the University of Queensland and co-author of the study, confirms. Chaudhry argues that while plate tectonics is now the main driver of continental blade exposure, Croton formed before the lithosphere plates began to move. ” When two continents [les plaques] They collide, forming the Himalayas and forming the Alps. This was not 3 billion years ago “” he said?.

An essential process for the reproduction of organisms

The continents have a thick crust (usually over 45 km) that allows them to ‘float’ like a plug in the water above the earth’s surface; On the other hand, continental masses with crusts less than 40 km are underwater. So the secret of the height of the earth lies in its thickness. So, the team tried to understand how and why Haroun started breeding.

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Granite – which is the result of the slow cooling of large volumes of magma – forms the Singhboom croton at depths 3.5 to 3 billion years ago, meaning the crust may have thickened during this period. Volcanic eruption over time. Granite is one of the least dense rocks. Singapore, for example, became more buoyant as the crust of the croton became stronger. The researchers concluded that it was about 50 km thick about 3 billion years ago; So that it was thick enough to float like an iceberg in water.

The Earth, which produces oxygen in both the atmosphere and the oceans, is not only capable of producing life, but is said to have contributed to the formation of local cold climate pockets by retaining carbon dioxide in the corrosive atmosphere of the early continents. Formation of glaciers. In fact, the first glacier deposits appeared in geological records about 3 billion years ago, shortly after the formation of the first oceanic continents.

However, scientists have not been able to determine how many continents the primitive earth currently has, which will provide a better understanding of the evolution of the various geochemical cycles operating on the planet. There is still uncertainty about the relief of the first continents. These questions will undoubtedly be the subject of future research.

Source: PNAS, P. Chaudhary et al.

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