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Aravalli Hills: India’s Ancient Shield and Its Uncertain Future - The Deep Talk - Radio Haanji
Season 1 Episode 2726
Stretching from Gujarat through Rajasthan to Haryana and Delhi, the Aravalli Hills are among the oldest surviving mountain systems on Earth, with rocks that began forming almost 2 billion years ago. These worn-down ridges quietly control dust storms, rainfall patterns, groundwater recharge, and even the heat and haze that reach Delhi-NCR.
In November 2025, a new Supreme Court–backed definition declared that only hills rising at least 100 metres above local terrain would be formally recognised as “Aravalli Hills,” triggering a fierce debate about mining, urban expansion, and environmental safeguards. This article follows the journey discussed on Radio Haanji’s “The Deep Talk” with Dr. Sandeep Kaur and Gautam Kapil—linking geology, ecology, law, and lived experience to explain why these ancient hills matter more than ever.
What Makes the Aravalli Hills So Ancient?The Aravalli Hills are part of a Precambrian mountain belt whose rocks date back to roughly 2–3 billion years, making them older than the Himalayas and among the world’s earliest mountain systems. Geologists identify two major Proterozoic rock sequences—the Aravalli Supergroup and the Delhi Supergroup—resting on an even older Archean basement formed about 4 billion years ago.
Over hundreds of millions of years, episodes of rifting, subduction, island-arc formation, and continent–continent collision built and then wore down the Aravalli orogenic belt, leaving today’s rounded ridges instead of sharp snow peaks. Later magmatic events, including the extensive Malani volcanics, mark one of the world’s large igneous provinces, underscoring the range’s global geological significance.
Key takeaway: The Aravallis are not just old hills near Delhi; they are a living archive of early Earth tectonics and continental evolution.
How Do the Aravallis Shape North India’s Climate and Rivers?The Aravalli Range runs roughly southwest–northeast for about 600–700 kilometres, forming a broken but crucial highland between the Thar Desert and the Indo-Gangetic plains. These hills influence local wind patterns, intercept dust, and help modulate the track and intensity of monsoon systems reaching North-West India.
Several rivers rise or are sustained by catchments in the Aravallis, including tributaries of the Yamuna, Luni, and Banas, making the range a key watershed for Rajasthan, Haryana, and Delhi. Forest patches and rocky outcrops create microclimates that cool nearby areas, support rainfall recycling, and buffer settlements against heat waves and dust storms.
What Role Do the Aravalli Hills Play in Stopping Desertification?For decades, scientists and planners have recognised the Aravalli Hills as a natural barrier that slows the eastward spread of the Thar Desert towards Haryana, Delhi, and western Uttar Pradesh. Forest cover, soil, and vegetation on these ridges act as “green walls,” trapping sand, stabilising dunes, and cutting the intensity and frequency of dust storms.
Where deforestation, quarrying, and overgrazing have stripped the slopes, researchers describe a shift toward “rocky desert” conditions, with thin soils, exposed rock, and accelerated erosion. This not only damages biodiversit
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