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Peninsular Plateau - Overview

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Introduction

The Peninsular Plateau constitutes the oldest and most stable landmass of the Indian subcontinent, representing the ancient Gondwanaland basement that has remained above sea level since the Precambrian era. Covering approximately 16 lakh square kilometers — roughly half of India’s total land area — this triangular-shaped plateau extends from the Aravalli Range in the northwest to the Nilgiri Hills in the south, bounded by the Western and Eastern Ghats on its flanks. The plateau’s geological stability, mineral wealth, and ancient landforms distinguish it fundamentally from the geologically young Himalayan system.

Geological Antiquity and Composition

The Peninsular Plateau forms part of the Indian Shield, a stable cratonic block composed predominantly of Archean gneisses, schists, and granites that are 2.5 to 3.8 billion years old. These basement rocks — among the oldest on Earth — outcrop in the Dharwar, Bastar, Singhbhum, and Aravalli cratons. The plateau has experienced episodic marine transgressions, sedimentation, volcanism, and uplift over geological time, but unlike the Himalayas, its deformation has been primarily epeirogenic (broad vertical movements) rather than orogenic (mountain-building compression).

Key geological formations include:

  • The Dharwar System: Highly metamorphosed sedimentary and volcanic rocks from the Archean-Proterozoic transition, containing economically significant deposits of iron ore, manganese, and gold (Kolar Gold Fields).
  • The Cuddapah and Vindhyan Systems: Proterozoic sedimentary formations — sandstones, shales, and limestones — deposited in epicontinental basins. The Vindhyan rocks in the Son-Narmada region preserve stromatolite fossils, representing some of India’s earliest life forms.
  • The Gondwana System: Permian-Carboniferous fluvial and lacustrine sediments deposited in rift valleys along major fault lines, containing India’s major coal reserves in the Damodar, Son, Mahanadi, and Godavari valleys.
  • The Deccan Traps: Vast flood basalt provinces covering approximately 5 lakh square kilometers in west-central India, erupted during the Cretaceous-Paleogene transition (65-66 million years ago) through fissure volcanism. The Deccan volcanism is linked to the Réunion hotspot and may have contributed to the Cretaceous-Paleogene mass extinction.

Major Physiographic Components

The Peninsular Plateau presents a west-to-east tilt, as evidenced by the generally eastward drainage of its major rivers. The average elevation ranges from 600 to 900 meters, with local relief created by residual hills, linear ridges, and deeply incised river valleys.

The Deccan Plateau: The largest component, bounded by the Western Ghats in the west, the Eastern Ghats in the east, and the Satpura Range in the north. This extensive lava plateau slopes eastward, drained by the Godavari, Krishna, and Penner river systems.

The Central Highlands: The northern part of the plateau, bounded by the Aravalli Range in the northwest and the Vindhyan scarp in the south. This region includes the Malwa Plateau, the Bundelkhand Upland, and the Baghelkhand region.

The Chota Nagpur Plateau: In the northeastern part of the peninsula, this dissected plateau composed of Precambrian rocks is India’s richest mineral province — the “Ruhr of India” — containing iron ore, coal, manganese, bauxite, mica, copper, and limestone.

The Meghalaya Plateau (Shillong Plateau): Structurally part of the Peninsular shield but separated by the Rajmahal-Garo gap (an extension of the Bengal Basin), this plateau was uplifted along the Dauki Fault and receives world-record rainfall on its southern escarpment.

The Western and Eastern Ghats

The Western Ghats (Sahyadri) extend approximately 1,600 km from the Tapti River mouth in Gujarat to Kanyakumari. They form a continuous but uneven escarpment with an average elevation of 900-1,100 meters, rising to 2,695 meters at Anamudi in Kerala. The Ghats’ steep western face intercepts moisture-laden monsoon winds, creating a pronounced orographic rainfall gradient — the windward slopes receive over 4,000 mm annually while the leeward Deccan lies in a rain shadow receiving 600-800 mm. The Palghat Gap (30 km wide), the Bhor Ghat, and the Thal Ghat are major passes traversing the Western Ghats.

The Eastern Ghats comprise a discontinuous chain of hills extending from the Mahanadi River in Odisha to the Nilgiri Hills in Tamil Nadu, approximately 1,500 km in length. Lower (average 600 m) and more fragmented than the Western Ghats, they have been dissected by the east-flowing rivers — Mahanadi, Godavari, Krishna, and Kaveri — that have carved wide gaps. The highest peaks include Mahendragiri (1,501 m) in Odisha and Jindhagada Peak (1,690 m) in Andhra Pradesh. The Eastern Ghats are composed predominantly of charnockites, khondalites, and other Precambrian metamorphic rocks with rich bauxite deposits.

Where the Western and Eastern Ghats converge in the south, the Nilgiri Hills (Tamil Nadu), Anaimalai Hills, Palani Hills, and Cardamom Hills form a highland massif known as the Southern Hill Complex, with elevations exceeding 2,500 meters. These ranges harbor the Shola-grassland mosaic ecosystem — unique to the high-altitude Western Ghats — and several important hill stations including Ooty (Udhagamandalam), Kodaikanal, and Munnar.