Describe the structure and evolution of the Himalayan mountain system.
Introduction
The Himalayas are the youngest and highest fold mountain range in the world. Stretching across 2,400 km from the Indus to the Brahmaputra, they represent a complex tectonic history resulting from the collision of two massive continental plates.
Evolution of the Himalayas
- Tethys Geosyncline: Around 200 million years ago, the supercontinent Pangea broke apart. Between the Laurasia (Eurasia) and Gondwanaland (India) lay the Tethys Sea.
- Plate Movement: The Indian plate began drifting northward. As it approached Eurasia, the sediments deposited in the Tethys Sea were squeezed and folded.
- Phases of Upliftment: The Himalayas did not rise all at once. They evolved in three major phases:
- Oligocene Phase: Formation of the Great Himalayas.
- Miocene Phase: Formation of the Lesser Himalayas.
- Post-Pliocene Phase: Formation of the Shiwaliks.
Geological Structure
The Himalayas consist of three longitudinal parallel ranges, separated by major fault lines (thrusts):
- The Himadri (Great Himalayas): The innermost and highest range with an average height of 6,000m. It contains peaks like Mt. Everest and Kanchenjunga. It is composed of archean rocks (granite and gneiss).
- The Himachal (Lesser Himalayas): Located south of Himadri, it is highly compressed and altered. It is famous for hill stations and contains ranges like Pir Panjal and Dhauladhar.
- The Shiwaliks (Outer Himalayas): The southernmost range made of unconsolidated sediments. It is known for its Duns (longitudinal valleys) like Dehradun.
Conclusion
The Himalayas are geologically unstable and tectonically active, as evidenced by frequent earthquakes and landslides. Their evolution is an ongoing process, making them a unique physiographic feature that regulates the Indian climate and provides perennial water to millions.