Himalayan Mountain System: Formation, Divisions, and Significance Explained

Formation and Tectonic Activity

The Himalayan mountain system is the youngest and highest mountain range in the world. Its formation began approximately 50 to 60 million years ago. This occurred due to the collision of the Indian Plate with the Eurasian Plate. The Indian Plate, moving northward, subducted beneath the Eurasian Plate. This immense pressure caused the Tethys Sea, which once lay between these two landmasses, to uplift and fold. The sediments accumulated in the Tethys geosyncline were compressed and folded to form the mighty Himalayas. This ongoing tectonic activity is why the region is seismically active, experiencing frequent earthquakes. The rate of uplift is still significant, making the Himalayas a dynamic geological feature. The process continues today, with the Indian Plate still moving northwards at a rate of about 5 cm per year.

Major Longitudinal Divisions

The Himalayas are divided into three parallel ranges, running from west to east. The Great Himalayas, or Himadri, is the northernmost and highest range, with an average height of over 6,000 meters. It contains the world's highest peaks, including Mount Everest (8,848.86 meters) and Kanchenjunga (8,586 meters). The Lesser Himalayas, or Himachal, lies south of the Himadri. Its average elevation ranges from 3,700 to 4,500 meters. This range is famous for hill stations like Shimla, Manali, and Darjeeling. The outermost range is the Shiwaliks, or Outer Himalayas. These are the youngest and lowest ranges, with an average elevation between 900 and 1,100 meters. They are composed of unconsolidated sediments brought down by rivers from the northern ranges. The valleys between the Himachal and Shiwaliks are known as 'Duns' in the west (e.g., Dehradun) and 'Duars' in the east.

Regional Divisions and Features

Besides longitudinal divisions, the Himalayas are also divided regionally based on river valleys. The Punjab Himalayas lie between the Indus and Satluj rivers, stretching for about 560 km. The Kumaon Himalayas are situated between the Satluj and Kali rivers, extending for approximately 320 km. Nanda Devi is a prominent peak in this section. The Nepal Himalayas, the longest section, are located between the Kali and Tista rivers, covering about 800 km. This section hosts many of the highest peaks. Finally, the Assam Himalayas lie between the Tista and Dihang rivers, extending for about 720 km. This regional classification helps in understanding the varied characteristics and local names of different parts of the mountain range. Each section has distinct geological and ecological features, influenced by the rivers that carve through them.

Significance for India

The Himalayas play a crucial role in shaping India's climate and geography. They act as a formidable barrier, preventing cold Siberian winds from entering India in winter, thus keeping North India warm. Conversely, they trap the monsoon winds, causing heavy rainfall in the subcontinent. The Himalayas are the source of perennial rivers like the Ganga, Yamuna, and Brahmaputra, which are lifelines for millions. They are also rich in biodiversity, hosting numerous species of flora and fauna, many of which are endemic. Strategically, they form a natural northern frontier, providing defense. Economically, they support tourism, hydroelectric power generation, and agriculture in their valleys. The unique cultural diversity found in the Himalayan states further highlights their profound impact on the nation. The mountains also influence the distribution of mineral resources and forest wealth.

Important Keywords Explained

Tethys Seaplace

An ancient ocean that existed between the supercontinents of Laurasia and Gondwana. Its closure and the subsequent collision of the Indian and Eurasian plates led to the formation of the Himalayan mountain range. Sediments accumulated in this geosyncline were folded and uplifted.

Geosynclineconcept

A large, elongated, subsiding basin in which a thick sequence of sediments accumulates. The Tethys Geosyncline was a crucial feature in the geological history of the Himalayas, providing the material that was later compressed and uplifted into mountains.

Subductionconcept

A geological process where one tectonic plate moves under another and sinks into the mantle as the plates converge. In the case of the Himalayas, the Indian Plate subducted beneath the Eurasian Plate, causing immense pressure and uplift.

Duns and Duarsplace

These are longitudinal valleys found between the Lesser Himalayas (Himachal) and the Shiwaliks (Outer Himalayas). 'Duns' are common in the western part (e.g., Dehradun), while 'Duars' are found in the eastern part (e.g., Haridwar, though often associated with the eastern Himalayas).

Additional Facts & Context

• The average width of the Himalayas varies from 400 km in Kashmir to 150 km in Arunachal Pradesh.
• There are over 100 peaks in the Himalayas that exceed 7,200 meters (23,600 ft) in elevation.
• The Karakoram Range, though often associated, is technically part of the Trans-Himalayan system, not the main Himalayan range.
• The Siachen Glacier, located in the eastern Karakoram range, is the second-longest non-polar glacier in the world.
• The Himalayas are home to approximately 10,000 species of plants, 300 mammals, and 1,000 birds.