Northward movement of India is still in progress at the velocity of 5cm/year. The collision with the Eurasian plate leads to continuous crumbling of the sediments which in turn is increasing the height of the Himalayas. Youthful nature of rivers, presence of river terraces, similar fossils in Shivalik and Tibetan plateau confirms the fact that Himalayas are still rising.
PLATE TECTONICS & FORMATION OF HIMALAYAS AND TIBETAN PLATEAU
During northward movement of Indian plate, the Tethys Ocean floor subducted. Most of the thick sediments on the Indian margin of the ocean were scraped off and accreted onto the Eurasian continent. Continent-continent convergence (India – Eurasian plate convergence) led to folding and crumbling of these marine sediments. Because of the same nature of both the plates there was not much density difference and hence there was no clear-cut subduction as is generally in case of continent-ocean or ocean-ocean convergence. C-C convergence produced ‘double layering effect’ and hence the thickness of the crust in that area increased. This is the main reason behind tremendous height of Himalayas and Tibetan Plateau.
Further, because the collision is still undergoing, the height of Himalayas is still rising. folding took place in three successive phases giving rise to three layers of Himalayas.
PHYSIOGRAPHIC DIVISION OF HIMALAYAS
The Himalayas consist of a series of parallel mountain ranges like Trans Himalayas, Inner Himalayas, Lesser Himalayas and Shiwalik range.
TRANS HIMALAYAN MOUNTAIN RANGE
These are also known as Tibetan Himalayas and lie north of the Great Himalaya range. The major ranges of Trans Himalayas include Karakoram, Ladakh, Zanskar and Kailash.
- Backbone of high Asia
- Indus river system lies to its south.
- Yarkand river system lies to its north. (Yarkand river is the head stream of the Tarim River.)
- It lies to the south of Karakoram.
- Indus river flows between Ladakh and Zanskar range and creates deepest gorge at a place in Bunji.
- It lies to the south of Ladakh range.
Kailash mountain range
- It begins from the South – East of Ladakh range.
- Kailash Parvat (Sumeru Parbat) is located here
During the collision of the Indian and the Eurasian Plate, three north-dipping, geological fault lines were formed. These structures essentially separate the different rocky formations that characterise the different stages of the Himalayan outcrop—the higher Himalayas, the lesser Himalayas and the sub-Himalayan Shivalik range.
- Main Central Thrust: Dividing line between Great Himalayas and Lesser Himalayas
- Main Boundary Thrust: Dividing line between lesser Himalayas and Shiwaliks
- Main Frontal Thrust: Dividing line between Himalayan foothills and Northern plains.
Note: Similarly there exists a fault line near Aravallis also, named Great Boundary Fault- Place where Aravallis meet Vindhyas