The Peninsular Block of India

Where did the Peninsular Block come from?

The Peninsular Block is a fragment of Gondwanaland. It is one of the oldest and most stable landmasses on Earth, largely untouched by the folding that built the Himalayas. Millions of years of erosion wore down its original highlands. What remains are residual mountains, not active fold mountains.

Which ranges count as residual mountains?

The Aravalli Range, the Veliconda Hills, and the Mahendragiri Hills are all residual mountains of this ancient landmass. The Aravalli Range is considered India’s oldest mountain range, older than the Himalayas by hundreds of millions of years.

Why does the west coast have natural harbours, not deltas?

The Konkan and Malabar coasts show clear submergence. Faulting and tectonic subsidence drowned the lower reaches of west-flowing rivers. This drowning created natural harbours, like Mumbai, and estuaries, rather than deltas.

What about the east coast?

Parts of the east coast instead show features of emergence, where land has risen or sea level has fallen, exposing former sea floor. This emergence, combined with sediment from major rivers, is why the east coast has broad deltas, unlike the west coast’s estuaries.

What are the Central Highlands?

The Central Highlands sit between the Aravalli Range and the Chotanagpur Plateau. The Vindhya Range forms their southern edge. Most of the region sits 700-1,000m above sea level, sloping down towards the north and northeast. The Vindhya and Kaimur ranges form step-like plateaus on the region’s south. Most streams that feed the Yamuna rise here. The Banas river is the exception: it rises in the Aravallis and flows east, the only major Chambal tributary coming from the west.

What makes the Chotanagpur Plateau India’s mineral heartland?

The Chotanagpur Plateau is the eastern part of the Central Highlands. It lies south of the Rajmahal Hills, mostly in Jharkhand. It holds large reserves of coal, iron ore, mica, bauxite, and copper, feeding India’s steel and power industries directly. The Damodar Valley coalfields, including Jharia, hold most of India’s coking coal, the specific coal type used to make steel. This eastern stretch is really a series of smaller, flat-topped plateaus, like the Hazaribagh, Ranchi, and Palamu plateaus.

What shape do Peninsular river valleys take?

Peninsular rivers are old and mature. They flow over a stable, worn-down landmass, and form broad, shallow valleys. Deep, V-shaped valleys are a Himalayan feature instead. Young, fast-flowing, snow-fed rivers cut them into the still-rising fold mountains.

What makes black soil good for cotton?

Weathered basalt across the Deccan Trap breaks down into black soil, also called regur. It holds moisture well, so it stays fertile through the dry season without much irrigation. This is India’s main cotton belt, covering Maharashtra, Madhya Pradesh, and Gujarat.

What grows on red and laterite soil?

Older crystalline rocks across the rest of the plateau, in states like Karnataka, Tamil Nadu, and Odisha, weather into red and laterite soil instead. It drains fast and holds far less moisture, so it needs irrigation to farm intensively. Farmers here mostly grow millets and pulses, crops suited to low, uneven moisture. Much of the Deccan Plateau sits in the rain shadow of the Western Ghats, so it gets far less rainfall than the coast just to its west. That is exactly why the black-soil cotton belt is largely rain-fed, and drought-prone in weak monsoon years.

What triggered the Koyna earthquake?

The Koyna-Warna zone sits in Maharashtra’s Western Ghats, near the western fault-edge of the Peninsular Block. It is a textbook case of reservoir-triggered seismicity. Filling the Koyna Dam’s reservoir, completed in 1962, raised pore pressure on nearby faults and set off earthquakes.

How big was the 1967 quake?

A magnitude 6.3 quake struck on 10 December 1967, the largest known reservoir-induced earthquake anywhere. Thousands of smaller quakes have followed since. Koyna shows that even a largely stable landmass can have locally active zones, especially near its fault-bound western edge.

How much of India’s coastline is eroding?

The National Centre for Coastal Research’s 2022 Shoreline Change Assessment Atlas found about 34% of India’s coastline eroding. Parts of the west coast are eroding at roughly 2.5 metres a year, on top of the older, natural submergence that shaped this coast. NCCR’s shoreline-change mapping feeds into coastal-zone planning, helping states manage the most vulnerable stretches.

2025-26 update: on 24 December 2025, the Union Ministry of Environment, Forest and Climate Change ordered a complete ban on new mining leases across the entire Aravalli Range, from Delhi to Gujarat (source: Deccan Herald).

• A boundary dispute: on 26 February 2026, the Supreme Court extended its interim mining freeze, saying “no one yet knows” the exact boundaries of the range.
• Why it matters: a November 2025 ruling had defined “Aravalli Hills” narrowly, by elevation. Critics said this would leave over 90% of the range unprotected. The Court has now ordered an expert panel to fix this definition.