Aravalli Range: Stretching across Rajasthan like an ancient stone spine, the Aravalli Range is one of the oldest fold mountains on Earth, older than the Himalayas themselves. Formed nearly 2,500 million years ago during the Precambrian era, it splits the state into two worlds: the parched Thar Desert in the west and the fertile plains in the east. For RAS and RPSC aspirants, this range isn't just geography-it's the key to understanding Rajasthan's climate, rivers, minerals, and history.
 

The Aravalli Range is one of the oldest fold mountain systems in the world and forms the most important physiographic feature of Rajasthan. Stretching across four Indian states, this ancient mountain range divides Rajasthan into two distinct geographical regions and plays a critical role in shaping the state's climate, drainage, and ecology. For any RAS or RPSC aspirant, understanding the Aravalli Range is essential, as it forms the foundation for almost every other topic in Rajasthan's physical geography.

What is the Aravalli Range?

The Aravalli Range is a chain of hills that runs in a north-east to south-west direction across northern and western India. It is considered one of the oldest fold mountain ranges in the world, older even than the Himalayas. In Rajasthan, the Aravalli Range acts as a natural backbone, separating the arid western desert from the fertile eastern plains.

Origin of Aravalli Range

The origin of the Aravalli Range dates back to the Precambrian era, making it one of the oldest geological formations on Earth.

• The Aravalli Range was formed due to intense folding and tectonic movements during the Aravalli-Delhi orogeny, one of the earliest mountain-building events in geological history.
• Geologists estimate the age of the Aravalli Range to be around 1,800 to 2,500 million years old.
• Due to prolonged weathering and erosion over millions of years, the range has lost its original height and now exists mostly as a series of low, rounded, and broken hills rather than tall, sharp peaks like younger mountain ranges.
• The rocks of the Aravalli system mainly consist of quartzite, schist, gneiss, and marble, which indicates their metamorphic origin.
• Because of its extreme age, the Aravalli Range is often called a "relict mountain" or a mountain in its old age stage of the geographical cycle.

Extent of Aravalli Range

The Aravalli Range has a vast geographical spread across northern and western India.

• In Rajasthan, the Aravalli Range enters from Sirohi district near Khedbrahma and continues in a north-easterly direction, finally fading out near Khetri in Jhunjhunu district.
• The width of the range is not uniform - it is widest around Mount Abu and becomes narrower as it moves towards Delhi.
• The range gradually decreases in height from south to north, with isolated hillocks visible near Delhi.

Division of Rajasthan by Aravalli Range

One of the most important functions of the Aravalli Range is dividing Rajasthan into two major physiographic regions:

1. Western Region – Covers the Thar Desert, characterized by arid climate, sand dunes, and scanty rainfall.
2. Eastern Region – Covers the fertile plains and plateau areas, receiving comparatively higher rainfall and supporting agriculture.

This division has a direct impact on the climate, vegetation, agriculture, and population distribution of the entire state.

Significance of Aravalli Range

The Aravalli Range holds immense geographical, ecological, and economic importance for Rajasthan and the surrounding region.

1. Climatic Significance

• Acts as a climatic divide, blocking monsoon winds and influencing rainfall patterns differently on either side.
• Prevents the eastward expansion of the Thar Desert to a large extent.

2. Water Divide

• The Aravalli Range functions as a major water divide, separating rivers that flow towards the Arabian Sea from those flowing towards the Bay of Bengal basin.
• Rivers like Banas, Berach, and Sabarmati originate from different parts of this range.

3. Ecological Significance

• Home to important wildlife sanctuaries and forest cover, including Sariska and parts of Mount Abu Wildlife Sanctuary.
• Supports unique flora and fauna adapted to rocky and semi-arid conditions.

4. Mineral Wealth

• Rich in minerals such as copper, zinc, marble, granite, and mica.
• The Khetri copper belt, located at the northern end of the range, is a major mining hub of India.

5. Agricultural and Economic Importance

• The hills influence the fertility of adjoining plains through weathering and soil deposition.
• Acts as a natural barrier that protects eastern agricultural lands from desert winds.

6. Defence and Strategic Importance

• Historically, the Aravalli hills served as a natural defence system for Rajput kingdoms, protecting forts like Chittorgarh, Kumbhalgarh, and Ranthambore.

Quick Revision Table: Aravalli Range at a Glance

Important Points for RAS Mains

• The Aravalli Range is a textbook example of residual mountains, formed by prolonged denudation of an older, taller mountain system.
• It represents the final stage of the geographical cycle of erosion, often compared to old-age topography.
• Aspirants should be able to explain both origin (geological) and significance (functional) aspects for descriptive answers.
• Comparative questions often ask about the Aravalli vs Himalayas in terms of age and formation - remember, the Aravalli is older but structurally weaker due to erosion.

Conclusion

The Aravalli Range is far more than just a mountain system - it is the geographical backbone of Rajasthan that has shaped the state's climate, economy, culture, and history for millions of years. From its ancient Precambrian origin to its role as a modern-day water divide and mineral belt, the Aravalli Range remains one of the most important and frequently asked topics in RAS and RPSC examinations. A clear understanding of its origin, extent, and significance will help aspirants confidently tackle both prelims and mains-level questions.

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