In news– A new study has suggested that the earliest continental landmass emerged from Jharkhand’s Singhbhum region.
Key highlights of the study–
- Researchers 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.
- Patches of the earliest continental land, however, exist in Australia and South Africa, too.
- They have found the age by analysing the uranium and lead contents of tiny minerals and studied the granites that form the continental crust of Singhbhum region.
- According to them, 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.
- 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.
- This study was conducted by researchers from India, Australia and the US.
- The researchers also aim to understand the evolution of India’s three other ancient continental fragments — Dharwar, Bastar and Bundelkhand regions.
Theories of landmass evolution–
- Continental Drift theory- It is the hypothesis that the Earth’s continents have moved over geologic time relative to each other, thus appearing to have “drifted” across the ocean bed. It is associated with Alfred Wegener.
- Convectional Current theory- According to this theory, the intense heat generated by radioactive substances in the mantle seeks a path to escape, giving rise to the formation of convection currents in the mantle. It was proposed by Arthur Holmes in the 1930s.
- Seafloor spreading theory- This theory, introduced by Harry Hess & Robert Dietz, was proven as patterns of magnetic field polarity preserved in seafloor basalt and by age dating of the rocks.Polar wandering theory- This theory is similar to Continental Drift theory. It is the relative movement of the earth’s crust and upper mantle with respect to the rotational poles of the earth.