Earth’s continents first emerged from oceans 700 million years earlier than thought

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The first continents emerged from Earth’s oceans 700 million years earlier than previously thought, according to a new study that sheds more light on the evolution of the planet’s habitability.

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Although widely debated, the rise of the continents is believed to have been driven by plate tectonics some 2.5 billion years ago.

However, new research, Published on Monday in the magazine PNAS, suggested that “continental landmass began to emerge above sea level between 3.3 and 3.2 billion years ago,” 700 million years earlier than most models predicted.

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The new findings shed more light on the formation of Earth’s early continents – or cratons – and how they may have affected the planet’s atmosphere, oceans and climate.

In the research, scientists including Priyadarshi Choudhury of Australia’s Monash University assessed the igneous and sedimentary record of the Singhbhum Craton in India from 3.6 billion to 2.8 billion years ago. They also estimated the age of some of the planet’s oldest rocks from continental fragments in India, Australia, and South Africa, which may have formed from the world’s first coastlines.

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The researchers specifically analyzed zircon grains in the Singhbhum sandstones, and found that these were deposited about 3 billion years ago – making them the oldest beach deposits in the world.

Based on this analysis, researchers say that a continental landmass emerged in India at least 3 billion years ago.

They found that the Singhbhum Craton in eastern India rose above the sea about 3.3 billion to 3.2 billion years ago, ahead of previous estimates of 2.5 billion years ago.

Sedimentary rocks of this era are also present in the oldest cratons in Australia (Pilbara and Yilgarn cratons) and in South Africa (Kapval cratons), with scientists noting that several continental landmasses may have emerged during this period around the world.

However, the study found that the processes of plate tectonics, as observed on present-day Earth, were not necessary for the first continent to emerge from the ocean.

Instead, the scientists found that the emergence of the Singhbhum craton from the ocean was influenced by the thickening of volcanic magma beneath the ocean, which was buoyant due to its silica-rich composition and floated “like a cork in the water” above Earth’s mantle. “

“Like icebergs, the tops of continents with a thick crust (usually thicker than 45 km) stick out over the water, while continental blocks with a crust thinner than about 40 km remain submerged,” explained the scientists. Conversation,

The emergence of this continental crust may have contributed to the spread of early life on land, as well as weathering and nutrient runoff, the study said.

These nutrients may have helped early photosynthetic life flourish and produce abundant oxygen which eventually helped make it oxygen rich environment We live in the present, the scientists said.

The blooming photosynthetic lifeforms also seized atmospheric carbon dioxide and caused the global cooling of the early Earth, he said.

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Credit: www.independent.co.uk /

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