Earth’s first landmass emerged in Singhbhum: study

Last Updated12/11/2021

Earth’s first continents rose out of the ocean 700m years earlier than previously thought, a new analysis of ancient rocks suggests.
Researchers who have studied rock sediments in eastern India believe the discovery could explain an increase in oxygen in the atmosphere, and the formation of glaciers, during that period of Earth’s history.
Analysis of sediments from Singhbhum, near Kolkata, suggests the first stable continents – known as cratons – started to emerge above sea level between 3.3 to 3.2bn years ago.

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 answer to “when the first landmasses were formed lay in the sedimentary rocks of the region”.
Scientists found a particular type of sedimentary rocks, called sandstones.
They then tried to find their age and in which conditions they have formed and found the age by analysing the uranium and lead contents of tiny minerals.
As per scientists, 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, they inferred that the Singhbhum region was above the ocean before 3.1 billion years ago.

The researchers studied the granites that form the continental crust of Singhbhum region.
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 and 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 surrounding oceanic crust owing to buoyancy.
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.