Geography of Himalayas: Terai, Bhabar, Shivalik, Lesser and Greater Himalayas
Himalayas can be divided into several geographical regions, which are distinct in flora and fauna also. These different regions, demarcated at various thrust and faults, make the climate of Himalayas diverse. The climate ranges from tropical at the base of the mountains to permanent ice and snow at the highest elevations. The amount of yearly rainfall increases generally from west to east along the front of the range. This diversity of climate, altitude, rainfall and soil conditions generates enormous biodiversity region making it one of the Biodiversity Hotspots of the world.
The main geographical regions of Himalaya include Terai belt, Bhabhar belt, Shiwalik Hills & Inner Terai, Lesser Himalayas, Midlands, Greater Himalaya and Trans-Himalaya.
Terai belt is the zone of sand and clay soils at the junction of northern plains and Himalayas. As the name suggests, Terai region gets higher rainfall than the plains. The speed of the Himalayan Rivers is slowed down in the Terai region and these rivers deposit fertile silt during the monsoons. The water table in this region is high and vegetation is largely savannah in a mosaic of deciduous and evergreen forests called Terai-Duar forests.
Bhabar belt is located above the Terai belt, also sometimes known as Himalayan foothills. It is made up of porous and rocky soils that get made of the debris washed down from the higher ranges. The climate here is subtropical and vegetation is Himalayan subtropical pine forests and Himalayan subtropical broadleaf forests. The Himalayan subtropical pine forests are dominated by Chir trees and Himalayan subtropical broadleaf forests are dominated by the sal tree (Shorea robusta).
Shivalik Hills & Inner Terai
Shivaliks or Churia or Margalla Hills are the outermost range of foothills extending across the Himalayan region through Pakistan, India, Nepal and Bhutan. This is mainly located along a Himalayan Frontal Thrust (HFT).
The vegetation here is dominated by Himalayan subtropical pine and broadleaf forests. The Inner Terai valleys are open valleys north of Shiwalik Hills or nestled between Shiwalik sub ranges. Examples include Dehra Dun in India and Chitwan in Nepal.
Lesser Himalaya is also known as Mahabharat Zone. The hills here range 2000 to 3000 meters and are located along the Main Boundary Thrust (MBT) fault zone. This zone is home to some of the deepest canyons in the world. The vegetation here is Himalayan subtropical forests.
This region is located north of the Mahabharata range or Lesser Himalaya. It is located along the Main Central Thrust fault zone, where the Greater Himalaya begin. Here the vegetation is along with coniferous forests along with broadleaf forests.
The Great Himalayas which is a single range and the oldest of the three ranges with a height above 6,000 m including Mount Everest, K2 and Kanchendzonga and nine of the 14 highest peaks in the world. Greater Himalayas is located north of the Main Central Thrust. Here the highest ranges rise abruptly into the realm of perpetual snow and ice. The vegetation here is Himalayan alpine shrub and meadows. The shrublands are composed of junipers as well as a wide variety of rhododendrons. They also possess a remarkable variety of wildflowers. Valley of Flowers National Park in the western Himalayan alpine shrub and meadows contains hundreds of species. The upper limit of the grasslands increases from west to east, rising from 3,500 meters to 5,500 meters.
The trans-Himalaya is the rain-shadow region just behind the main peaks of the towering Himalayan Mountains. Notable places of the trans-Himalayas include the Tibetan Plateau, the Ladakh area of the Northern Indian Himalayas (Indus Valley) along with the Lahaul-Kinnaur-Spiti region and in north-western Nepal the Dolpo/Dolpa, Mustang, Manang, Humla and Mugu areas. The Trans-Himalayas, mainly composed of granites and volcanic rocks of Neogene and Paleogene age are bounded by the Kailas (southwest), Nganglong Kangri (north), and Nyainqêntanglha (southeast) mountain ranges and by the Brahmaputra River.