Structure of the Himalayas
The Himalayas are a unique mountain range in the form of a folded mountain chain. Due to the structural complexity in different regions and areas, no single perspective can be formed about its framework and structure. However, the general characteristics of its various tectonic units can be described.
Indus-Tsangpo Suture Zone
This region represents a tectonic unit resulting from the compression below the Indian Shield by the Tibetan Massif. It serves as the boundary line between the Indian and Eurasian plates and is characterized by ophiolite and other foreign terranes as well as Flysch-like depressions. The foreign terranes are found in rifts in ophiolites and Flysch depressions, and they are considered responsible for major volcanic eruptions in Tibet. This region extends from the naked mountains in the northwest Himalayas to Namcha Barwa in the far east. It likely extends towards the southwestern parts, reaching the Andaman-Nicobar chain via Pakistan-Afghanistan and Assam-Myanmar in the east. The Tethys Sea lies to the south of this region. While there is not much clarity on its structure, this region has likely undergone several phases of folding and thrusting, resulting in complex structures. The region has experienced folding and thrusting from the Cretaceous to the Pleistocene era.
Main Central Thrust
This separates the higher Himalayas in the north from the lesser Himalayas in the south and has played a significant role in the tectonic history of these mountain ranges. The formation of this narrow thrust region is due to the combination of gneiss, schist, phyllite, quartzite, and limestone. These rocks are highly folded and mixed.
Lesser or Middle Himalayas
This is a complex and highly folded and faulted belt. It has various thrusts that result in large stretches of rock being displaced.
Main Boundary Thrust
This large-scale oblique fault extends from Assam to Punjab and separates the outer or sub-Himalayas from the lesser Himalayas.
Outer or Sub-Himalayas
This region is predominantly constructed with Tertiary structures, including simple folded anticlines and synclines, with axes parallel to the ridges of these mountain ranges. These low-height mountains also have longitudinal valleys, known locally as ‘doons’. The southern boundary of the sub-Himalayas is mostly faulted, with its extension resembling the large wings of alluvial fans.
The Himalayan Divisions
The Himalayan mountain range is divided into three parts:
- Greater or Greater Himalayas
- Lesser or Middle Himalayas
- Shivalik or Outer Himalayas
Greater Himalayas
The Greater Himalayas is a massive mountain range that stretches from the Patkai Bum Mountains in the east to the Nanga Parbat in the west, covering a vast expanse of 2500 km long and 150 to 400 km wide, with an elevation rising towards the south. Most of the mountain ranges are in India, Nepal, and Bhutan, with the northern slopes part of Tibet and the western extent stretching to Pakistan. The Karakoram range in the north-western part is its remotest mountain range. Its farthest north western edge meets with the Hindu Kush, separated by the Gilgit River. To the east of Karakoram lies the Kunlun mountain range, which extends all the way to north of Tibet. The Ladakh, Zaskar, Pir Panjal and Dhauladhar ranges are viewed as parallel chains running in the same direction as the Karakoram, towards the south. The Ladakh mountain range branches off towards western Tibet in the Kailash range. In the Shimla-Kumaon region, there is a similar continuity between the Nag Tibba and Mussoorie ranges, as well as the Mahabharat ranges in Nepal, but this continuity is broken by the Kali River flowing in a perpendicular direction. The Shivalik mountain range, located parallel to the southern slopes of the Great Himalayas, forms a roughly continuous chain of foothills at the base of the mountains. The high mountain ranges of the Great Himalayas are identified by different names in Nepal, Sikkim, Bhutan, and Northeast India, but the names given by the inhabitants are popular for them. The actual geographical boundaries of the Himalayas outside India and Nepal have not yet been determined and are still a subject of dispute. However, there is a general consensus that the Great Himalayas extend from the Karakoram to Arunachal Pradesh in the far northeast, but some geologists consider the Himalayas to extend one end to the mountain ranges of Pakistan and Afghanistan and on the other end to the mountains of Myanmar, based on their geological and physical resemblance. These mountains, which are reservoirs of snow and are therefore called the abode of snow, should not be considered unchangeable due to their internal relationships and essential natural and structural connections. The total length of this mountain system from the Mizoram mountains in the east to the Makran mountain range near the Iran border is about 5,000 km.
| Passes | Characteristics |
|---|---|
| Jelep La Pass | This pass is located in the state of Sikkim. Currently, the trade route from Kalimpong to Lhasa passes through this route. |
| Nathu La Pass | This pass is related to the state of Sikkim. It connects Darjeeling, Chumbi Valley, and Tibet. |
| Burzil Pass | This pass connects the Great Himalayas with Kashmir. It connects Gurez in the Kishanganga Valley with Astor in the Indus Valley. It is an ancient trade route. |
| Shipki La Pass | This pass is located in the Sutlej Valley of the Great Himalayas and connects Himachal Pradesh with Tibet. |
| Baralacha Pass | This pass is located in the Great Himalayas and connects Lahaul in Himachal Pradesh with Leh in Jammu and Kashmir. It is situated on the Manali-Leh road. |
| Jotila Pass | This pass is located in the state of Himachal Pradesh and connects Himachal Pradesh with Tibet. It is an ancient trade route. |
| Lipulekh Pass | This pass is located in the state of Uttarakhand. |
| Bum La Pass | This pass is related to Arunachal Pradesh and connects Arunachal Pradesh with Tibet and China. It is located on the ancient trade route between India and Tibet. |
| Dihang Pass | This pass connects Arunachal Pradesh with Tibet and China. It is located on the ancient trade route between India and China. |
| Mana Pass | This pass is located in the Great Himalayas in Uttarakhand state. |
| Niti Pass | This pass is located in the state of Uttarakhand and is the same route as the ancient Kailash-Mansarovar Yatra. |
Lesser or Middle Himalayas
It is made up of mountain ranges of medium height and is closely related to the inner or higher Himalayas, with heights ranging from about 3,600 to 4,200 meters. It has a complex system of mountain ranges that are approximately 60 to 80 km wide. This region is primarily composed of pre-Cambrian, Paleozoic and Sinzoic structures. It is located south of the Himalayan and north of the Shivalik ranges and is separated by the main boundary thrust. It has several parallel ranges, such as Dhauladhar, Pir Panjal, Nag Tibba, Mahabharat range and Mussoorie range. In this range, Pir Panjal (3,494 meters) and Banihal (2,832 meters) are two major passes. There are several tourist towns in this range, such as Shimla, Chail, Chakrata, Mussoorie, Nainital, Ranikhet, Almora, Darjeeling, etc. There are many valleys here, such as the Pir Panjal Valley and a western range valley of the Himalayas in Kashmir, the Kangra Valley in Himachal Pradesh, which is a structural valley spread from the foothills of the Dhauladhar range to the front, and the Kullu Valley, which is a parallel valley. The southern slope of the Lesser Himalayas is sharp, rugged, and bare, while the northern slope is gentle and densely forested. There are many pasturelands located on these slopes, known as ‘Margs’ in Kashmir and ‘Bugyals’ and ‘Payars’ in Uttarakhand.
The Pir Panjal Range
The Pir Panjal mountain range starts from the Jhelum River in Kashmir-Punjab and extends up to the upper Vyas River for about 300 km. The Kashmir Valley (Valley of Kashmir or MCT) separates it from the Zaskar Range. It is a minor range of the Himalayas.
The Dhauladhar Range
The Dhauladhar is a distant southern range of the Lower Himalayas. Its maximum height is only up to 4,000 m. The range is formed of low-grade Pre-Cambrian tectonic depressions. These structures are continuously present in the Naga Tibba Range and Mussoorie Range of the Garhwal-Kumaun region.
The Mahabharat Range
This is an uninterrupted portion of the Lower Himalayas (Mussoorie Range) in southern Nepal, with peaks reaching up to 3,000 m. The Kathmandu Valley located to its north forms a distinct structure similar to the Srinagar Valley in Kashmir.
The Outer or Sub Himalaya
Also known as the Outer Himalayas, it is the southernmost range of the Himalayas. Its southern slope is relatively steep. This range contains chaur (flat-topped) scarps, abyssal valleys, and distinct peaks. Many flat-topped structures are present in the northern slopes of the Shiwalik and the southern slopes of the Lesser Himalayas, known as ‘Doon’ in the west and ‘Duars’ in the east. This range is known by various local names, such as Jammu Hills in Jammu and Kashmir, Dudhwa Range in Uttarakhand, Churia Hills in Nepal, and Dafala, Miri, Aboor, and Mishimi Hills in Arunachal Pradesh. This range is covered with dense warm temperate moist deciduous forests.
Jammu and Kirana Hills
The northern-western extension of the Shiwalik Range is called the Jammu Hills and Kirana Hills. The Jammu Hills extend to the southwestern boundary of Jammu and Kashmir state. Many tributaries of the Indus River pass through here. The Kirana Hills extend from the southern-eastern part of Jammu Hills in the north-west to the south-east. It has also been highly dissected by rivers of the Indus basin.
Churia Hills
Located on the northeastern border of Uttar Pradesh, this hilly region also extends to the south of Nepal. It is a part of the Shiwalik Range that has been highly dissected by various rivers. The Churia Hills extend from Mechi in the east to Mahakali in the west. This region is characterized by dense forests and a very sparse population. Efforts are being made to conserve the biodiversity and forest resources here.
Sumeshwar Range
This is the name of the Shiwalik Range in Bihar, which is the northernmost range of Bihar. It is approximately 75 km long. The next part of this range is located as the border between Bihar and Nepal. The highest peak is 880 meters. The height increases from south to north, but in West Champaran, the average height is only 457 meters. The northern region has several passes, which have been created due to the flow of rivers. Mentionable among these are Sumeshwar, Bhikhanathor and Makhait. These passes have established the connectivity between the northern plains and the Terai region.
Singalila Range
This range forms the border between Sikkim and West Bengal. It is a water divide between the Ganges and Brahmaputra river systems. The highest peak is Phalut (3,595 meters), and Sandakphu (3,639 meters) is a major tourist spot. The Phalut peak also forms the tri-junction of India, Nepal and Sikkim.
Mizo Hills
This is the local name for the Lushai Hills in Mizoram. It is a part of karst topography. It is located in a tertiary basin situated between the folded chains of the Assam range and the Shiwalik Range.
The Eastern Himalayas or Purvanchal Hills
These hills extend from north to south on the India-Myanmar border, forming a distinct geographical entity from the rest of the Himalayas. The main ranges are the Mishmi Hills, Patkai Bum, Naga Hills, Tripura Hills and Mizo Hills.
The Garo, Khasi and Jaintia Hills
These hills are located in the state of Meghalaya in northeastern India. They are known for heavy rainfall and are home to the Khasi and Garo tribes, who are among the oldest indigenous communities in India.