In News
- Scientists have found sandstones in Singhbhum with geological signatures of ancient river channels, tidal plains and beaches over 3.2 billion years old, representing the earliest crust exposed to air.
Major Findings
- Jharkhand’s Singhbhum region: The Singhbhum district of Jharkhand, famous for its mica mines all over the world, can change the perspective of understanding the whole world.
- A new study has challenged the widely accepted view that the continents rose from the oceans about 2.5 billion years ago.
- It suggests this happened 700 million years earlier about 3.2 billion years ago and that the earliest continental landmass to emerge may have been Jharkhand’s Singhbhum region.
- Sandstones of Singhbhum: Scientists have found sandstones in Singhbhum with geological signatures of ancient river channels, tidal plains and beaches over 3.2 billion years old, representing the earliest crust exposed to air.
- The age was found by analysing the uranium and lead contents of tiny minerals.
- These rocks are 3.1 billion years old and were formed in ancient rivers, beaches, and shallow seas.
- All these water bodies could have only existed if there was continental land.
- Thus, it is been inferred that the Singhbhum region was above the ocean before 3.1 billion years ago
- Patches of the earliest continental land, however, exist in Australia and South Africa.
- Formation theory: The researchers studied the granites that form the continental crust of the Singhbhum region and found that these granites are 3.5 to 3.1 billion years old and formed through extensive volcanism that happened about 35-45 km deep inside the Earth.
- They continued on and off for hundreds of millions of years until all the magma solidified to form a thick continental crust in the area.
- Due to the thickness and less density, the continental crust emerged above the surrounding oceanic crust owing to buoyancy.
- Other findings: The researchers believe the earliest emergence of continents would have contributed to a proliferation of photosynthetic organisms, which would have increased oxygen levels in the atmosphere.
Significance of the study
- Understanding the existence: At a time when the entire world was debating about changes in climate, it is very important to understand how our atmosphere, oceans and climate came into existence and how they interacted with geological processes operating deep inside Earth to make our planet habitable.
- Link: It allows us to link the interior of Earth to its exterior in deep time.
- Making future studies easy: India has three other ancient continental fragments known as Dharwar, Bastar and Bundelkhand regions.
- The research also tends to break another well-accepted notion: continents rose above the ocean due to plate tectonics, which is the major driver today for increases in the elevation of landmasses.
Formation of the Earth’s Continents
- Initially, more than 4.6-billion years ago, the world was a ball of burning gas, spinning through space.
- At first, superheated gases were able to escape into outer space, but as the Earth cooled, they were held by gravity to form the early atmosphere.
- Clouds began to develop as water vapour collected in the air and then it began to pour with rain, causing the early oceans to rise up.
- It took hundreds of millions of years for the first landmasses to emerge.
- About 250-million years ago, long, long after the Earth had formed, all the continents of the time had joined together to form a supercontinent called Pangaea.
- This supercontinent broke up about 200-million years ago to form two giant continents, Gondwana and Laurasia.
- Gondwana comprised what is now Africa, South America, Australia, Antarctica and India. The Indian sub-continent lay off the east coast of Africa before it broke off and moved north rapidly.
- It collided with Asia, creating one of the world’s greatest mountain ranges, which extends for more than 2,500 kilometres – the Himalayas.
- The amazing process of plate tectonics, in which the Earth’s landmasses move slowly across the Earth’s crust, is still continuing.
- Far in the future, some scientists have predicted that the present continents will converge again, to form a new supercontinent.
Source: IE
