The Peninsular Plateau represents the oldest and most stable landmass of the Indian subcontinent. Geologically, it is an elevated shield mainly composed of highly metamorphosed and deformed rocks dating back to the Archean and Protirozoic eras.
Origin and Formation
- Gondwanaland Fragment: The plateau was formed due to the breaking and drifting of the Gondwana landmass during the Mesozoic era, making it one of the ancient landforms on Earth.
- Rock Composition: The basement complex consists of Archean gneisses and schists. Major portions are covered by subsequent formations like the Dharwar, Cuddapah, and Vindhyan systems, capped by the Cretaceous-Eocene volcanic basalt in the northwest.
- Tectonic Stability: Known for its structural rigidity, this region has remained largely exempt from folding forces, experiencing primarily vertical movements, fracturing, and faulting.
Major Geological Formations
| Formation System | Geological Age | Key Rock Types | Major Mineral Wealth |
| Archean System | Pre-Cambrian | Gneiss, Granites, Schists | Iron ore, Manganese, Copper |
| Dharwar System | Lower Proterozoic | Metamorphosed Sediments | Gold (Kolar), Manganese, Iron |
| Cuddapah System | Purana Era | Quartzites, Slates, Limestones | Bauxite, Asbestos, Clay |
| Vindhyan System | Upper Proterozoic | Sandstones, Shales, Limestones | Diamond (Panna), Building stones |
| Deccan Trap | Cretaceous-Eocene | Basaltic Lava | Regur Soil (Black Soil) |
Physiographic Boundaries and Extent
The Peninsular Plateau rises to a general elevation ranging between 600 and 900 meters above sea level. It forms an irregular triangle with its apex at Kanyakumari and its base running parallel to the Ganga-Yamuna plains.
Geographic Limits
- North-Western Boundary: Marked by the Aravalli Range extending from Gujarat to Delhi.
- Northern and North-Eastern Boundary: Defined by the Bundelkhand uplands, Kaimur hills, Rajmahal Hills, and the Shillong/Karbi-Anglong Plateau.
- Western Boundary: Formed by the continuous wall of the Western Ghats (Sahyadris).
- Eastern Boundary: Formed by the discontinuous and eroded Eastern Ghats.
Regional Divisions of the Peninsular Plateau
The Narmada rift valley divides the plateau into two broad distinct regions: the Central Highlands to the north and the Deccan Plateau to the south.
The Central Highlands
- Malwa Plateau: Situated between the Aravallis and the Vindhyas. It features a rolling surface dissected by deep trench-like valleys formed by the Chambal, Kali Sindh, and Parbati rivers, creating a distinct “ravine topography” (Chambal Badlands).
- Bundelkhand and Baghelkhand: Located to the east of the Malwa plateau. Bundelkhand is characterized by an old dissected upland made of Bundelkhand Gneiss, marked by senile topography and massive quartz reefs.
- Chota Nagpur Plateau: Represents the north-eastern projection. Drained by the Damodar, Subarnarekha, and Barakar rivers, it features “pat lands” (laterite-capped high plateaus). It is known as the “Ruhr of India” due to its immense mineral wealth.
- Meghalaya (Shillong) and Karbi-Anglong Plateau: An extension of the main Peninsular block separated by the Malda Fault (Garo-Rajmahal Gap). It includes the Garo, Khasi, and Jaintia Hills.
The Deccan Plateau
- Deccan Trap (Maharashtra Plateau): A basaltic lava plateau formed by fissure eruptions. The lava sheets have a thickness of over 2,000 meters in the west and thin out towards the east.
- Karnataka Plateau (Mysore Plateau): Divided into Malnad (hilly, forested region) and Maidan (rolling plains). It features the highest point of Karnataka at Mullayanagiri (Baba Budan Hills).
- Telangana Plateau: Comprises an undulating surface with a senile topography featuring monadnocks, tors, and balanced rocks resulting from long periods of weathering.
Hill Ranges of the Peninsular Block
The Aravalli Range
- Type: Relict/Residual fold mountains of the Pre-Cambrian era.
- Extent: Extends for nearly 800 km from Ahmedabad to Delhi in a South-West to North-East direction.
- Highest Peak: Guru Shikhar (1,722 meters) located on Mount Abu.
The Vindhyan Range
- Type: Block mountains formed due to faulting.
- Extent: Runs parallel to the Narmada Rift Valley from Gujarat to Bihar (Sasaram) as the Bharner and Kaimur hills.
- Significance: Acts as the primary watershed between the Ganga river system and the peninsular river systems.
The Satpura Range
- Type: A horst mountain system flanked by the Narmada rift valley in the north and the Tapi rift valley in the south.
- Components: Comprises the Rajpipla hills, Mahadeo hills, and the Maikal range.
- Highest Peak: Dhupgarh (1,350 meters) near Pachmarhi on the Mahadeo hills. Astamba Dongar is another significant peak.
The Western and Eastern Ghats: A Comparative Analysis
Relief, Continuity, and Drainage
| Parameter | Western Ghats (Sahyadris) | Eastern Ghats |
| Continuity | Continuous wall; can be crossed only through specific passes (Thal Ghat, Bhor Ghat, Pal Ghat). | Discontinuous, highly dissected by east-flowing rivers. |
| Average Elevation | 900 to 1,600 meters. Increases from North to South. | 600 to 650 meters. Decreases from North to South. |
| Highest Peak | Anamudi (2,695 meters) in the Anaimalai Hills. | Jindhagada Peak (1,690 meters) / Arma Konda in Andhra Pradesh. |
| Geological Origin | Escarpment of the Peninsular faulting block. | True residual mountains formed by denudation. |
| Rainfall Type | Orographic rainfall on the western slopes during South-West Monsoons. | Receives seasonal rain majorly from North-East Monsoons and cyclonic depressions. |
Major Mountain Passes of the Western Ghats
- Thal Ghat: Connects Mumbai to Nashik/Kolkata.
- Bhor Ghat: Connects Mumbai to Pune/Chennai.
- Pal Ghat (Palakkad Gap): Connects Palakkad (Kerala) to Coimbatore (Tamil Nadu) between the Nilgiri and Anaimalai hills.
- Senkota Pass: Connects Kollam (Kerala) to Madurai (Tamil Nadu) between the Cardamom and Varushanad hills.
Drainage Systems and River Anomalies
The general slope of the Peninsular Plateau is from West to East, which dictates the flow of the majority of its perennial and seasonal rivers into the Bay of Bengal.
East-Flowing Rivers
- Rivers like the Mahanadi, Godavari, Krishna, and Cauvery flow eastward into the Bay of Bengal, developing extensive deltaic deposits at their mouths.
West-Flowing Rivers and Fault Trough Drainage
- Narmada and Tapi: These rivers present a major drainage anomaly by flowing from East to West into the Arabian Sea. They do not form deltas but create estuaries because they flow through structural rift valleys (fault troughs) created during the Himalayan mountain-building process.
Economic Significance and Mineral Endowments
The Peninsular Plateau serves as the mineral storehouse of India, driving the core industrial sectors of the nation.
Mineral Distributions
- Metallic Minerals: The Chota Nagpur Plateau and the Dharwar rock system contain nearly all of India’s iron ore, manganese, bauxite, and mica reserves.
- Non-Metallic Minerals: The Gondwana rock formations along the Damodar, Mahanadi, and Godavari troughs contain over 98% of India’s coal reserves.
Agricultural and Forest Resources
- Black Soil (Regur): The weathering of the basaltic Deccan Trap has produced highly fertile black cotton soil, making it ideal for cultivating cotton, sugarcane, and oilseeds.
- Forestry: The Western Ghats, Nilgiris, and parts of Central India harbor tropical moist deciduous and evergreen forests, providing high-value timber like teak, sal, and sandalwood.
- Hydroelectric Potential: High falls such as the Jog Falls (Sharavati river), Shivasamudram Falls (Cauvery river), and Hundru Falls (Subarnarekha river) provide significant potential for hydroelectric power generation.