Aravalli Range: Oldest Fold Mountains of India, Geology, Geography, and Ecological Significance

The Aravalli Range is the oldest fold mountain system on Earth and one of the most studied geological structures in the Indian subcontinent. Stretching roughly 692 kilometres in a north-east to south-west arc from the Raisina Hill in Delhi through Haryana and Rajasthan and ending near Palanpur in Gujarat, the Aravalli Range predates the Himalayas by more than a billion years. Geologists place its principal orogeny in the Pre-Cambrian era, between 2.5 billion and 1.7 billion years ago, making the Aravalli Range a fossil record of plate tectonics from the time when the Indian craton was still being assembled. Today the Aravalli Range survives as a worn-down stub of its former self, but it continues to shape the climate, hydrology, biodiversity, and demography of north-western India in ways that no other physical feature can match.

Geological Origin and Age

The Aravalli Range was formed by the collision of the Aravalli and Bundelkhand cratons during the Aravalli–Delhi orogeny. The folding event closed an ancient ocean basin and uplifted thick sequences of sediments that had accumulated on the continental margins. The resulting fold belt was once estimated to have stood as tall as the present-day Himalayas, possibly exceeding 7,000 metres. Over the next 1.5 billion years, weathering and erosion stripped away most of that elevation, leaving behind the resistant quartzite, schist, and gneiss ridges that we see today.

The rocks of the Aravalli Range belong to three main groups in stratigraphic order: the Bhilwara Supergroup at the base (Archaean), the Aravalli Supergroup in the middle (Palaeo-Proterozoic), and the Delhi Supergroup at the top (Meso-Proterozoic). Each group records a distinct cycle of sedimentation, volcanism, and metamorphism. The presence of stromatolite-bearing dolomites in the Aravalli Supergroup is one of the earliest pieces of evidence for life on the Indian subcontinent.

Geomorphological Character

The Aravalli Range is classified as a relict mountain. Its peaks are rounded, its slopes are gentle, and its drainage is mature. Three main physiographic divisions are recognised. The southern Aravalli rises from the Gujarat plain near Palanpur and includes the Mount Abu massif. The middle Aravalli, between Ajmer and Alwar, has the most discontinuous topography. The northern Aravalli, north of Delhi, has been reduced to low ridges that finally disappear beneath the alluvium of the Yamuna plain.

Extent and Spread Across Four States

The Aravalli Range passes through four states and one union territory: Gujarat (in the Banaskantha and Sabarkantha districts), Rajasthan (where the range is broadest and highest), Haryana (Mahendragarh, Rewari, Gurugram, Faridabad), and Delhi (the Delhi Ridge). The Rajasthan stretch accounts for roughly 80 per cent of the total length, and it is here that the Aravalli Range achieves its greatest width of around 100 kilometres and its highest elevations.

The total area covered by the Aravalli Range is approximately 65,000 square kilometres. The range acts as a watershed: rivers that rise on its western flank drain into the Arabian Sea or disappear into the desert (the Luni and the Banas–Sabarmati systems), while those rising on its eastern flank flow into the Bay of Bengal through the Chambal and the Yamuna.

Major Peaks

Guru Shikhar (1,722 m), located in the Mount Abu massif of Rajasthan, is the highest peak of the Aravalli Range. It is named after the Hindu sage Dattatreya. Other significant peaks include Ser (1,597 m), Doli (1,442 m), Achalgarh (1,380 m), Kumbhalgarh (1,224 m), Tarakgarh (1,055 m), and Raghunathgarh (1,055 m). Most of these peaks lie within Rajasthan.

Mount Abu: The Hill Station

Mount Abu is the only hill station in Rajasthan and the highest point in the Aravalli Range. Sitting on an isolated granitic plateau, it stays markedly cooler than the surrounding plains and supports a distinct vegetation that includes evergreen and semi-evergreen forests. Mount Abu is also a major pilgrimage centre, home to the Dilwara Jain temples built between the 11th and 13th centuries, and the Achaleshwar Mahadev temple. The Mount Abu Wildlife Sanctuary, declared in 1980, protects an area of 288 square kilometres and harbours leopard, sloth bear, and the endemic Indian grey wolf.

Ecological Role as a Barrier to the Thar Desert

The single most important ecological function of the Aravalli Range is acting as a physical barrier between the Thar Desert to its west and the fertile Gangetic plains to its east. The ridge intercepts dust storms from the west and prevents the eastward advance of the desert. Studies by the Forest Survey of India have shown that wherever the Aravalli Range has been breached by mining or quarrying, the rate of desertification on the eastern side has measurably increased. The Aravalli Range also feeds groundwater into the Yamuna basin and recharges aquifers across Haryana and Delhi.

The vegetation of the Aravalli Range varies with rainfall and elevation. The southern Aravalli supports tropical dry deciduous forest dominated by teak, dhok, salai, and khair. The middle and northern Aravalli are dominated by thorn scrub of acacia and ber. Above 1,200 metres on Mount Abu, sub-tropical broadleaf forest takes over.

Biodiversity

The Aravalli Range hosts the Sariska Tiger Reserve and the Ranthambore National Park, two of the most important tiger habitats in north-western India. Other protected areas include the Kumbhalgarh Wildlife Sanctuary, the Phulwari ki Nal Sanctuary, the Asola Bhatti Wildlife Sanctuary near Delhi, and the Sita Mata Wildlife Sanctuary. The range is also a major flyway for migratory birds and is part of the larger Indo-Burma biodiversity hotspot.

Mineral Wealth

The Aravalli Range is one of the most mineralised geological provinces in India. It hosts the country’s only producing zinc and lead mines at Zawar, Rampura-Agucha, and Rajpura-Dariba, all operated by Hindustan Zinc. The range also produces copper at Khetri (Rajasthan), marble at Makrana (the source of the marble used in the Taj Mahal), granite, soapstone, dolomite, calcite, and a wide variety of dimension stones. Rajasthan accounts for nearly 90 per cent of India’s marble production, almost all of it from the Aravalli Range.

The Mining Crisis and Legal Response

Unregulated mining has devastated large stretches of the Aravalli Range. Satellite imagery and reports by the Central Empowered Committee of the Supreme Court have documented the disappearance of 31 of the 128 named hills in the Rajasthan Aravalli between 1968 and 2019. In Haryana, the legally protected Aravalli area shrank by more than 50 per cent over the same period.

The Supreme Court has intervened repeatedly. In 2002, the court banned mining within 5 kilometres of designated forest areas in the Aravalli Range. In 2018, it ordered a complete halt to all mining in the Aravalli hills of Rajasthan until the state could demonstrate compliance with environmental safeguards. In 2024, the court widened the definition of “Aravalli” to include all hills with a slope of more than 100 metres above ground, bringing thousands of additional hectares under protection.

Aravalli Green Wall Project

In 2023 the central government announced the Aravalli Green Wall Project, modelled loosely on the African Great Green Wall. The project aims to create a 1,400-kilometre, 5-kilometre-wide green corridor along the entire Aravalli Range, covering Gujarat, Rajasthan, Haryana, and Delhi. The plan includes afforestation, restoration of degraded mines, revival of water bodies, and the planting of native species such as dhok, khair, and ber.

The Delhi Ridge

The northern tip of the Aravalli Range enters Delhi as the Delhi Ridge, a 35-kilometre-long quartzite escarpment that runs from Tughlakabad in the south to Wazirabad in the north. The Delhi Ridge is divided into four segments: the Northern Ridge (Civil Lines), the Central Ridge (between Sadar Bazar and Dhaula Kuan), the South-Central Ridge (Mahipalpur), and the Southern Ridge (the largest, near Asola Bhatti). The Delhi Ridge is the city’s primary green lung and a critical aquifer recharge zone. Encroachment, dumping of construction waste, and proliferation of the invasive Prosopis juliflora (vilayati kikar) have severely degraded the ridge.

Rivers Originating in the Aravalli

Several important rivers originate from the Aravalli Range. The Banas, the largest river entirely within Rajasthan, rises near Kumbhalgarh and joins the Chambal. The Luni rises in the Pushkar valley near Ajmer and flows south-west into the Rann of Kachchh, becoming progressively saltier as it crosses the desert. The Sabarmati and the Mahi rise on the western flank and flow south through Gujarat to the Arabian Sea. The Sahibi, a tributary of the Yamuna, rises near Sewar in Alwar. Smaller streams from the Delhi Ridge once fed natural baolis and tanks across the city and supported pre-modern Delhi’s water economy.

Strategic and Cultural Significance

Historically the Aravalli Range has served as a natural fortification. Rajput kingdoms built hill forts along its peaks, the most famous being Kumbhalgarh (a UNESCO World Heritage Site since 2013), Chittorgarh, Ranthambore, and Achalgarh. These forts controlled key passes and trade routes between the desert and the plains. The cities of Udaipur, Ajmer, Jaipur, and Alwar all owe their location and water supply to the Aravalli foothills.

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