Plate tectonics: The engine of Earth’s dynamics

The theory of plate tectonics is one of the most fundamental concepts in physical geography and geology, explaining the movement and interaction of Earth’s lithospheric plates. The lithosphere (comprising the crust and upper mantle) is divided into several rigid plates that float over the semi-molten asthenosphere.

According to the theory, proposed in the 1960s by scientists like Alfred Wegener, Harry Hess and others, these plates move due to convection currents generated by heat from the Earth’s interior. The movement occurs at different types of plate boundaries:

1. Divergent boundaries – Plates move apart, forming mid-ocean ridges and new crust (e.g., Mid-Atlantic Ridge).

2. Convergent boundaries – Plates collide, leading to subduction zones, mountain formation and volcanic activity (e.g., Himalayas, Andes).

3. Transform boundaries – Plates slide past each other, causing earthquakes (e.g., San Andreas Fault).

The theory unified earlier concepts like continental drift and seafloor spreading, explaining the distribution of earthquakes, volcanoes, oceanic trenches and mountain ranges.

For the UPSC exam, key points include

• Evidence: Paleomagnetism, distribution of fossils and fit of continental margins.

• Implications: Explains formation of landforms, seismic activity and plate movements influencing Earth’s evolution.

• Current relevance: Helps in disaster preparedness, resource exploration and understanding climate-geological interactions.

In essence, plate tectonics provides a dynamic framework for understanding Earth’s geological processes and their impact on the planet’s surface over geological time scales.