A sequence of numerous parallel or converging mountain ranges characterises this region. These ranges are divided by profound valleys, resulting in a terrain with intricate and rugged features. The southern slopes exhibit steep gradients, creating a challenging topography, while the northern slopes have relatively gentle inclines. Predominantly situated within the borders of India, Nepal, and Bhutan, most of the Himalayan ranges are present in these countries. The northern slopes extend partially into Tibet, particularly the trans-Himalayan region, and the western extremity spans across Pakistan, Afghanistan, and Central Asia. The stretch of the Himalayas between Tibet and the Ganga Plain comprises three successive parallel ranges, forming a distinctive geological feature.

Division of the Himalayas

1. The Trans-Himalayas – Tibetan Himalayas.
2. The Greater Himalayas
3. Shiwaliks or outer Himalayas
4. Lesser or Middle Himalayas
5. The Eastern Hills – Purvanchal: A chain of hills in North-East India.

THE TRANS HIMALAYAS

• The Himalayan ranges immediately to the north of the Great Himalayan range are commonly referred to as the Tibetan Himalaya, primarily because a significant portion of this region is situated in Tibet. 
• The main ranges within this expanse include the Zaskar, Ladakh, Kailas, and Karakoram. Extending approximately 1,000 km in the east-west direction, this area boasts an average elevation of 3,000 metres above mean sea level.
• The width of the Tibetan Himalaya averages about 40 km at its extremities and widens to approximately 225 km in the central part. 
• The Zanskar Range is notable for hosting the significant Nanga Parbat, which stands at 8,126 metres and is a prominent feature of this range.
• Running parallel to the Zaskar Range to the north is the Ladakh Range. 
• While this range primarily consists of peaks below 6,000 metres, it contributes to the diverse topography of the region. 
• The Kailas Range, also known as Gangdise in Chinese nomenclature, is an extension of the Ladakh Range in western Tibet. 
• Mount Kailas, the highest peak in this range, reaches an elevation of 6,714 metres. Importantly, the northern slopes of the Kailas Range serve as the origin of the River Indus.
• The northernmost range within the Trans-Himalayan Ranges in India is the Great Karakoram Range, also known as the Krishnagiri range. 
• Extending eastwards from the Pamir for around 800 km, the Karakoram Range is distinguished by its lofty peaks, with elevations exceeding 5,500 metres. 
• Some of the world's most significant glaciers outside the polar regions are located in this range.

Noteworthy peaks in the Karakoram include some surpassing 8,000 metres above sea level. K2, also known as Godwin Austen or Qogir, stands as the second-highest peak globally and the highest within the Indian Union. 

To the northeast of the Karakoram Range lies the Ladakh Plateau, which has undergone extensive dissection, resulting in various plains and mountains such as Soda Plains, Aksai Chin, Lingzi Tang, Depsang Plains, and Chang Chenmo.

THE GREAT HIMALAYA

• This mountain range, known as Inner Himalaya, Central Himalaya, or Himadri, stands as a significant geological feature with an average elevation of 6,100 metres above sea level and an average width of approximately 25 km. 
• Comprising central crystallines, including granites and gneisses, overlaid by metamorphosed sediments such as limestone, it represents a distinct geological composition.
• The folds in this range exhibit asymmetry, featuring steep south slopes and gentle north slopes, resulting in a distinctive 'hogback' topography—an extended, steep hill or mountain ridge. 
• Similar to the other two Himalayan ranges, this mountain arc convexes to the south.
• The termination of the range is marked by abrupt endings at the syntaxial bends, with one situated in the northwest at Nanga Parbat and the other in the northeast at Namcha Barwa. 
• Notably, this mountain range proudly hosts some of the world's tallest peaks, many of which remain perpetually snow-covered, contributing to the breathtaking and formidable landscape of the region.

THE MIDDLE HIMALAYA

• Nestled between the Shiwaliks in the south and the Greater Himalayas in the north, the Middle Himalayan range, also known as Himachal or Lower Himalaya, runs almost parallel to both these prominent mountainous formations. 
• Stretching across a length of about 2400 km, this range is approximately 60-80 km wide.
• With elevations ranging from 3,500 to 4,500 meters above sea level, the Lower Himalayas boast numerous peaks exceeding 5,050 meters, perpetually covered in snow. 
• The southern slopes are characterized by steep, barren terrain, inhibiting soil formation, while the northern slopes feature gentler gradients adorned with dense forests.
• In Uttarakhand, the Middle Himalayas showcase notable ranges such as Mussoorie and Nag Tibba. 
• The Mahabharat Lekh in southern Nepal seamlessly continues the Mussoorie Range. 
• To the east of the Kosi River, the lower Himalayas encompass regions like Sapt Kosi, Sikkim, Bhutan, Miri, Abor, and Mishmi hills.
• These Middle Himalayan ranges are more accessible to human habitation and have become home to several popular hill resorts. 
• Destinations like Shimla, Mussoorie, Ranikhet, Nainital, Almora, and Darjeeling, among others, are nestled within this region, providing picturesque landscapes and pleasant climates that attract tourists and serve as popular retreats.

The Pir Panjal Range

• The Pir Panjal Range, situated in Kashmir, stands out as the longest and most significant mountain range in the region. 
• Stretching over 300 km, it extends from the Jhelum River to the upper Beas River. 
• The elevation of this imposing range reaches up to 5,000 meters, and it is predominantly composed of volcanic rocks.

Passes in Pir Panjal

• Several notable passes traverse the Pir Panjal Range, providing crucial connections across the landscape. 
• These include the Pir Panjal Pass (3,480 m), Bidil (4,270 m), Gulabgarh Pass (3,812 m), and Banihal Pass (2,835 m). The Banihal Pass is particularly vital, serving as a key route for the Jammu-Srinagar highway and the Jammu-Baramulla railway.
• Major rivers like the Kishanganga, Jhelum, and Chenab cut through the Pir Panjal Range, shaping the terrain.

Extension as Dhauladhar Range

• To the southeast of the Ravi River, the Pir Panjal seamlessly transitions into the Dhaola Dhar Range. 
• This extension passes through notable locations such as Dalhousie, Dharmshala, and Shimla, contributing to the diverse geological features of the region.

Important Valleys

The Pir Panjal Range plays a pivotal role in defining the topography of the surrounding valleys. Notably:

• Kashmir Valley: Nestled between the Pir Panjal and the Zaskar Range of the main Himalayas, the valley of Kashmir forms a synclinal basin. 
• It features diverse deposits such as alluvial, lacustrine (lake deposits), fluvial (river action), and glacial deposits. 
• The Jhelum River meanders through these formations, cutting a deep gorge in Pir Panjal as it drains the valley.
• Kangra Valley: In Himachal Pradesh, the Kangra Valley, extending from the foot of the Dhauladhar Range to the south of Beas, is characterised as a strike valley.
• Kulu Valley: Positioned in the upper course of the Ravi River, the Kulu Valley represents a transverse valley, offering a unique geological landscape in the region.

SHIWALIK RANGE  :The Outer Himalayas

Also referred to as the Outer Himalayas, the Shiwalik Range is strategically positioned between the expansive Great Plains and the Lesser Himalayas. Spanning a distance of approximately 2,400 km, this range extends from the Potwar Plateau to the Brahmaputra Valley.

Key Characteristics:

• Altitude Variation: The altitude within the Shiwalik Range exhibits a range from 600 to 1500 metres, contributing to its diverse topography.
• Slopes and Width: The southern slopes of the Shiwaliks are notably steep, creating a dramatic contrast with the gentler northern slopes. The width of the range varies, from 50 km in Himachal Pradesh to less than 15 km in Arunachal Pradesh, forming an almost continuous chain of low hills.
• Geographical Extent: Extending from North-East India to Nepal, the Shiwaliks present an extensive and almost unbroken chain of hills. However, a distinct gap of 80-90 km accommodates the valleys of the Tista River and Raidak River.
• Forest Cover: The Shiwalik Range, particularly in North-East India up to Nepal, is characterised by dense forest cover. However, as one moves westward from Nepal, the forest cover gradually decreases due to a reduction in rainfall. The southern slopes in Punjab and Himachal Pradesh, in particular, have limited forest cover.
• Dissection by Seasonal Streams: The southern slopes of the Shiwalik Range in Punjab and Himachal Pradesh experience significant dissection by seasonal streams known as Chos.
• Valleys and Hills: The valleys within the Shiwalik Range are integral parts of synclines, while the hills form components of anticlines or antisynclines, contributing to the geological complexity of the region.

DUNS OR DUARS

Beyond DehraDun, the Shivalik Hills boast other significant duns contributing to the diverse topography. Noteworthy examples include Kotah, Patli Kothri, Chumbi, Kyarda, Chaukhamba, Udhampur, and Kotli. Each of these duns stands as a testament to the enduring impact of geological processes on the Shivalik Hills' formation.

PURVANCHAL HILLS

The Eastern Hills, also known as the Purvanchals, unfold as the southward extensions of the majestic Himalayas, tracing the northeastern border of India. Their geological narrative takes shape as follows:

• Origins at Dihang Gorge: The Himalayas, marked by the Dihang gorge, undergo a dramatic southward shift, giving rise to a series of comparatively lower hills collectively termed the Poorvanchal. Notably, these hills exhibit a westward convexity.
• Geographical Extent: Stretching along the India-Myanmar Border, the Purvanchal hills span from Arunachal Pradesh in the north to Mizoram in the south. This expansive range is characterized by diverse topography and geological features.
• Patkai Bum Hills: Dominated by robust sandstone formations, the Patkai Bum hills feature elevations ranging from 2,000 to 3,000 meters. They seamlessly merge into the Naga Hills, where the pinnacle is marked by Saramati, standing at an impressive 3,826 meters.
• Watershed Division: The Patkai Bum and Naga Hills collectively serve as a watershed, demarcating the boundary between India and Myanmar. This region plays a crucial role in the hydrological dynamics of the surrounding areas.
• Manipur Hills: Situated south of the Naga Hills, the Manipur Hills exhibit elevations generally below 2,500 meters. The Barail Range acts as a separator between the Naga and Manipur Hills, contributing to the diverse landscape.
• Barail Range and Beyond: Extending southward, the Barail Range takes a westward swing, giving rise to the Jaintia, Khasi, and Garo hills. These hills represent an eastward continuation of the Indian peninsular block, marked by the Ganga and Brahmaputra rivers.
• Mizo Hills (Lushai Hills): To the south of Manipur Hills lie the Mizo Hills, previously known as the Lushai Hills. With elevations below 1,500 meters, the highest peak, the Blue Mountain, reaches 2,157 meters in the southern expanse.

The Eastern Hills of Purvanchal, with their varied elevations, geological compositions, and expansive reach, contribute significantly to the geographical and ecological richness of the northeastern region of India.

FAQs - Himalayan Geological Structures

1. What defines the geological features of the Himalayan region?

Ans. The Himalayan region is characterised by a sequence of parallel or converging mountain ranges, separated by deep valleys, resulting in intricate and rugged terrain. Steep gradients mark the southern slopes, creating challenging topography, while the northern slopes have gentler inclines.

2. In which countries are the Himalayan ranges primarily located?

Ans. The Himalayan ranges are predominantly situated within the borders of India, Nepal, and Bhutan. The northern slopes extend into Tibet, particularly the trans-Himalayan region, and the western extremity spans across Pakistan, Afghanistan, and Central Asia.

3. How is the Himalayan region divided geologically?

Ans. The Himalayan region is divided into distinct geological divisions, including the Trans-Himalayas, Greater Himalayas, Shiwaliks (Outer Himalayas), Lesser or Middle Himalayas, and the Eastern Hills (Purvanchal).

4. What characterises the Trans-Himalayan Ranges or Tibetan Himalayas?

Ans. The Trans-Himalayan Ranges, often termed Tibetan Himalayas, include the Zaskar, Ladakh, Kailas, and Karakoram ranges. Extending approximately 1,000 km, this region boasts an average elevation of 3,000 meters above sea level and plays a significant role in river origins, including the Indus.

5. Which is the highest peak in the Trans-Himalayan Ranges?

Ans. Mount Kailash, standing at an elevation of 6,714 meters, is the highest peak in the Trans-Himalayan Ranges.

6. What is the significance of the Great Himalaya or Inner Himalaya?

Ans. The Great Himalaya, also known as Inner Himalaya or Himadri, features an average elevation of 6,100 meters. This range is characterized by asymmetrical folds, steep south slopes, and gentle north slopes, hosting some of the world's tallest peaks.

7. How is the Middle Himalaya, or Lesser Himalayas, described?

Ans. The Middle Himalaya, positioned between the Shiwaliks and Greater Himalayas, runs parallel to both ranges. It covers about 2400 km, with elevations ranging from 3,500 to 4,500 meters. Popular hill resorts like Shimla, Mussoorie, and Nainital are located in this region.

8. What is the Pir Panjal Range known for?

Ans. The Pir Panjal Range, the longest in Kashmir, extends over 300 km and rises to 5,000 meters. Composed mainly of volcanic rocks, it features crucial passes like Banihal Pass and shapes important valleys like Kashmir Valley.

9. What are the characteristics of the Shiwalik Range or Outer Himalayas?

Ans. The Shiwalik Range, positioned between the Great Plains and Lesser Himalayas, spans 2,400 km with altitudes from 600 to 1500 meters. It has steep southern slopes, gentler northern slopes, and is known for its forest cover and seasonal streams called Chos.

10. How were duns formed in the Shivalik Hills?

Ans. Duns, such as DehraDun, were formed in the Shivalik Hills due to the accumulation of conglomerates in temporary lakes. When rivers cut through these lakes, they left behind plains known as 'duns' or 'duars.'

11. What characterizes the Eastern Hills of Purvanchals?

Ans. The Eastern Hills, or Purvanchals, are the southward extensions of the Himalayas. Originating at the Dihang gorge, they run along the India-Myanmar Border, featuring hills like Patkai Bum, Naga Hills, Manipur Hills, and Mizo Hills.

12. What is the geological significance of the Purvanchals?

Ans. The Purvanchals play a vital role as a watershed, separating India and Myanmar. The Patkai Bum hills, Naga Hills, and Manipur Hills contribute to the diverse topography of this region.

13. How do the Shiwalik Hills contribute to the formation of duns?

Ans. The Shiwalik Hills were formed by conglomerate accumulation, initially obstructing rivers to create temporary lakes. When rivers cut through, duns like Dehra Dun were left behind.

14. What are some important valleys formed by the Pir Panjal Range?

Ans. The Pir Panjal Range contributes to valleys like the Kashmir Valley, known for its synclinal basin with diverse deposits, and the Kangra Valley in Himachal Pradesh, characterized as a strike valley.

15. How do the Shiwalik Range and Eastern Hills contribute to India's topographical diversity?

Ans. The Shiwalik Range and Eastern Hills contribute to India's topographical diversity by forming distinct geological features, including low hills, valleys, plateaus, and plains, creating a visually striking and ecologically diverse landscape.