Physiography of Rajasthan
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Rajasthan is India’s largest state by area (3,42,239 sq km), located in the northwestern part of the Indian subcontinent. Its physiography is remarkably diverse — from the Thar Desert in the west to the rugged Aravalli range in the centre, and from the fertile eastern plains to the wetlands of the Nainwa basin.
Key Facts for RPSC RAS:
- Rajasthan accounts for 10.4% of India’s total area.
- The Aravalli Range is one of the oldest mountain ranges in the world (approximately 3.5 billion years old) — older than the Himalayas.
- The Marusthali (Thar Desert region) covers about 62% of the state’s total area.
- The highest peak in Rajasthan is Guru Shikhar (1,722m) in the Aravalli range, near Mount Abu.
- Major geographic divisions: Western Desert, Aravalli Hills, Eastern Plains, and Southeastern Hills.
⚡ Exam tip: Questions on the Aravalli range’s role in blocking monsoon winds and creating the Thar Desert, and the identification of specific peaks/dunes, frequently appear in RAS Prelims and Mains.
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Major Physiographic Divisions
Rajasthan can be divided into four major physiographic divisions, each with distinct characteristics:
1. The Western Sandy Plains (Marusthali)
This region covers the western part of Rajasthan, bounded by the Aravalli in the east and the Pakistan border in the west. It is characterised by:
- ** sand dunes** — active and stabilised dunes of various shapes (longitudinal, transverse, barchan)
- Dharma (inter-dunal flat) areas — used for cultivation
- Rainfall: Less than 25 cm annually — among the driest areas in India
- Major cities: Jodhpur (Marwar region), Bikaner (Bikaner region), Jaisalmer, Barmer
The Thar Desert: The Marusthali is the eastern extension of the Thar Desert. The desert is not completely barren — it has oasis areas where groundwater is accessible. The sand dunes in this region are among the highest in the world, reaching heights of up to 150 metres.
Sub-regions of the Thar Desert:
- Sabsaili Dune Area — characterised by longitudinal dunes
- Barchan Dune Area — crescent-shaped dunes prevalent near Jaisalmer
- Dhrian Dune Area — stabilised dunes with vegetation
2. The Aravalli Range and Hill Region
The Aravalli Range runs from Gurgaon (Haryana) in the northeast through Rajasthan to Gujarat in the southwest — approximately 692 km, of which 550 km lies in Rajasthan.
Significance of the Aravalli:
- Acts as a natural barrier separating the Thar Desert (west) from the eastern plains
- Blocks the southwest monsoon winds, causing orographic rainfall on its eastern slopes and creating a rain shadow on its western side
- Contains rich mineral deposits — mica, feldspar, gemstone, marble
- The name “Aravalli” derives from “Ara” (dividing line) and “Vali” (the hills)
Major Peaks in Rajasthan:
| Peak | Height | Location |
|---|---|---|
| Guru Shikhar | 1,722m | Mount Abu (Sirohi) — highest in Rajasthan |
| Dilwara Hills | 1,502m | Near Mount Abu |
| Achalgarh | 1,381m | Mount Abu |
| Kumbhalgarh | 1,377m | Rajsamand — famous for its wall |
| Gorakh | 1,321m | Near Jodhpur |
The Aravalli is geologically ancient: Composed primarily of Archaean granite and gneiss, it represents the remnants of an ancient fold mountain system. Its rocks contain some of the oldest fossils on Earth.
3. The Eastern Plains (Banganga and Chambal Basin)
The eastern part of Rajasthan features alluvial plains formed by the Banganga, Chambal, and their tributaries. This region:
- Is the most fertile part of Rajasthan
- Receives moderate rainfall (50-80 cm annually)
- Is extensively irrigated through canals and tube wells
- Contains the Hadoti plateau region
Key features:
- Chambal River — the most important tributary of the Yamuna, flows through the ravine-rich Dholpur and Karauli areas
- Banas River — flows through the fertile plateau region, joins Chambal near Kot
- Banganga River — flows through the Jaipur and Bharatpur region
- The Duns (Daharas) — depression areas between sand dunes in the east, often fertile
4. The Southeastern Plateau and Hills
The southeastern region includes the Mewar and Dhundhar areas, characterised by:
- Hilly terrain of the eastern Aravalli extensions
- Vindhyan rocks (sandstone, limestone) in the eastern parts
- Kota stone — a famous building material from the Kota region
- Dense forests in the Bundi and Jhalawar areas
Sub-regions:
- Mewar Hills — rolling hills near Udaipur with the famous Nainwa basin
- Kota-Bundi Hills — characterised by steep, forested scarps
- Bhamaria Hills — near Bhilwara
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Detailed Analysis of Rajasthan’s Physiography
Geological Formation
Rajasthan’s geology reveals a complex history spanning over 3.5 billion years:
Pre-Cambrian Era (Archaean):
- The Aravalli rocks formed during this period — one of the oldest mountain systems on Earth
- Composed of ancient gneiss, schist, and granite
- The Bhilwara Supergroup of rocks contains important mineral deposits
Paleozoic to Mesozoic Eras:
- Sedimentary formations in the western Rajasthan area
- The Jaisalmer basin contains fossil evidence of marine life from this era
- Significant oil and gas potential in the western region
Tertiary and Quaternary Periods:
- The Thar Desert formed primarily during the Quaternary period
- Fluvial (river) deposits created the extensive alluvial plains of the east
- Wind-blown sand created the dune systems of the Marusthali
The Thar Desert — Formation and Characteristics
The Thar Desert (also known as the Great Indian Desert) covers approximately 77,000 sq km in Rajasthan, representing the most densely populated desert in the world.
Formation theories:
- Climate Change Theory: Monsoon failure over millennia transformed what may have been a semi-arid region into a desert
- Tectonic Theory: Uplift of the Aravalli mountains blocked moisture-bearing winds, creating a rain shadow
- Wind Pattern Theory: Prevailing southwest winds from the Arabian Sea deposited sand in the region due to topographic blocking
Types of Sand Dunes in Rajasthan:
| Dune Type | Description | Location |
|---|---|---|
| Barchan | Crescent-shaped, open end faces wind direction | Jaisalmer, Barmer |
| Longitudinal (Seif dunes) | Elongated parallel to wind direction | Bikaner, Jodhpur |
| Transverse | Perpendicular to wind direction | Along Jodhpur-Bikaner road |
| Star dunes | Pyramid-shaped, multiple wind directions | Extreme western border |
| Dome dunes | Circular, low-lying | Inter-dunal areas |
The Aravalli — Ecological and Economic Significance
The Aravalli range is not just a geographic feature — it is ecologically and economically critical:
Ecological:
- Creates a distinct dry sub-humid to semi-arid climate divide in Rajasthan
- The eastern slopes receive more rainfall and support tropical thorn and dry deciduous forests
- Acts as a watershed divide — rivers to its east flow into the Bay of Bengal; to the west, they either form inland lakes or dry up
Economic:
- Mica mines in the Bhilwara-Ajmer area — one of the most important mica belts in the world
- ** marble quarries** at Makrana (Nagaur) — the white Makrana marble was used in the Taj Mahal
- ** granite and stone** for construction
- Gemstones — the Aravalli region produces agate, quartz, and feldspar
Rajasthan’s Spatial Divisions
| Division | Area (approx.) | Characteristics |
|---|---|---|
| Western Desert | 1,10,000 sq km | Sandy, arid, low population density |
| Aravalli Region | 70,000 sq km | Hilly, mineral-rich, moderate rainfall |
| Eastern Plains | 85,000 sq km | Fertile, alluvial, highest agricultural productivity |
| Southeastern Plateau | 77,000 sq km | Forested, hilly, Vidhyanchal influence |
Mountains and Peaks — Detailed Notes
Mount Abu: The only major hill station in Rajasthan, located at the southwestern end of the Aravalli range in Sirohi district. It rises to 1,229m above sea level at the town, but Guru Shikhar nearby reaches 1,722m — the highest point in Rajasthan.
Guru Shikhar: A peak near Mount Abu named after the sage Atri. It has a temple dedicated to him. The spot offers panoramic views of the desert and the Aravalli valley. It is also significant from a geological perspective — the rocks here date to approximately 3.5 billion years.
Kumbhalgarh: Famous for its massive wall (36 km), the second longest wall after the Great Wall of China. The wall was built by Rana Kumbha in the 15th century and encloses a large area of the Aravalli hills.
The Nakki Lake Mystery
Nakki Lake at Mount Abu is unusual — it is cut into the hillside rather than being a natural depression, and is considered sacred by both Hindus and Jains. Local tradition holds that the lake was created by the gods using their nails (nakh). Geologically, it may be a landslide dam.
Practice Questions for RPSC RAS
- How does the Aravalli range influence the climate and vegetation of Rajasthan?
- Distinguish between barchan and longitudinal sand dunes with examples from Rajasthan.
- Explain the geological age of the Aravalli range and its significance for mineral deposits.
- Which are the major rivers of Rajasthan and how do they differ in their origin and flow patterns?
- Why is the Thar Desert considered the most densely populated desert in the world?
Common Mistakes to Avoid
- Confusing the Aravalli with the Vindhyas — they are separate mountain systems; the Vindhyas are further east in Madhya Pradesh.
- Forgetting that Rajasthan has three distinct river systems — the Yamuna basin (eastern), the Arabian Sea drainage (western rivers that don’t reach the sea), and the Indus system in the far west.
- Assuming the desert has no water — there are significant groundwater resources and the Indira Gandhi Canal has transformed large areas.
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