Singhbhum region in Jharkhand may have been the first mainland to rise above the ocean, study finds


Researchers have always been puzzled by when the landmasses we reside on first emerged and until recently it was widely believed that continents emerged from the ocean about 2.5 billion d ‘years. However, a recent study changed this notion.

Recent research has shown that Earth’s first continents may have emerged from the ocean some 700 million years earlier than previously thought. And to the surprise of many, the first mainland land to rise around 3.2 billion years ago may have been the Singhbhum region in Jharkhand. Scientists from India, Australia and the United States have found sandstones at Singhbhum with geological signatures of ancient river channels, tidal plains and beaches over 3.2 billion years old, representing the first crust exposed to air.

When asked how Singhbhum entered the picture of Earth science research, Dr Priyadarshi Chowdhury of Monash University, the lead author of the study, told indianexpress.com that the answer to “when the first land masses formed was in the sedimentary rocks of the region”.

“We found a special type of sedimentary rock called sandstone. We then tried to find their age and under what conditions they were formed. We found the age by analyzing the uranium and lead content of tiny minerals. These rocks are 3.1 billion years old and formed in ancient rivers, beaches and shallow seas. All of these bodies of water could only have existed if there had been continental land. So, we deduced that the Singhbhum region was above the ocean 3.1 billion years ago, ”Chowdhury said.

The Singhbhum region where the research was conducted. (Photo: Special arrangement)

But, Chowdhury said, patches of the early mainland also exist in Australia and South Africa.

Speaking about how they determined that the area rose above the ocean during the time period mentioned above, Chowdhury explained, “We have studied the granites that form the continental crust of the Singhbhum area. These granites are 3.5-3.1 billion years old and formed through extensive volcanism that occurred about 35-45 km deep inside the Earth and continued intermittently for hundreds of millions of years until all of the magma solidified to form a thick continental crust in the area. Due to its thickness and lower density, the continental crust emerged above the surrounding oceanic crust due to buoyancy.

“This is the most direct and clear date yet for the emergence of mainland,” said Chowdhury. The results were published in the Proceedings of the National Academy of Sciences, an American research journal.

Research also tends to shatter another well-accepted notion: continents rose above the ocean due to plate tectonics, which is the main driver of increased mass elevation today. continental.

Two of the researchers during their study in the Singhbhum area. (Photo: Special arrangement)

“Today we have plate tectonics to control elevation. When two continents (plates) collide, you form the Himalayas, you form the Alps, ”he said. “This was not the case 3 billion years ago [ago]. The earliest continents probably rose above sea level as they were inflated by the gradual injection of magma from deep within the Earth.

The researchers believe that the early emergence of the continents would have contributed to the proliferation of photosynthetic organisms, which would have increased oxygen levels in the atmosphere. “Once you create land, you also create shallow seas, like lagoons,” Chowdhury added, accelerating the growth of oxygen-producing life forms that may have boosted oxygen in the atmosphere and l ‘ocean.

Urging on the importance of such studies, Chowdhury said that at a time when the whole world was debating climate change, it is very important to understand how our atmosphere, oceans and climate came into being and how they interacted. with geological processes operating at depth. inside the Earth to make our planet habitable.

“It allows us to connect the interior of the Earth with its exterior in deep time. India has three other ancient continental fragments – the regions of Dharwar, Bastar and Bundelkhand. We need to understand their evolution. What we did in Singhbhum can serve as a model to study these other cratons, ”he added.

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