Deccan Plateau: Geology and Resources Explained for UPSC SSC

Geological Formation

The Deccan Plateau is a large plateau in Western and Southern India. It rises to 100 metres in the north and to more than 1,000 metres in the south. It is triangular in shape and is bounded by the Western Ghats to the west, the Eastern Ghats to the east, and the Satpura Range, Maikal Range, and Mahadeo Hills to the north. The plateau was formed by massive volcanic eruptions that occurred during the late Cretaceous period, approximately 66 million years ago. These eruptions covered a vast area with layers of basaltic lava, forming what is known as the Deccan Traps. The lava flows were extensive, creating a thick sequence of igneous rocks that are predominantly tholeiitic basalt.

The formation of the Deccan Traps is linked to the Reunion hotspot. As the Indian Plate drifted northward after breaking away from Gondwana, it passed over this hotspot, leading to immense outpourings of lava. This geological event is one of the largest volcanic provinces in the world. The erosion of these volcanic rocks over millions of years has given the plateau its characteristic step-like appearance, especially visible in the Western Ghats. The underlying geology also includes older Precambrian crystalline rocks, which are exposed in parts of the plateau, particularly in the eastern and southern regions.

Physiographic Divisions

The Deccan Plateau can be broadly divided into several physiographic regions. The most prominent are the Deccan Traps region, the Karnataka Plateau, and the Telangana Plateau. The Deccan Traps region, covering parts of Maharashtra, Gujarat, and Madhya Pradesh, is characterized by black soil (Regur soil) derived from basaltic rocks. This soil is highly fertile and suitable for cotton cultivation. The Western Ghats form the sharp western edge of the plateau, acting as a major watershed and receiving heavy rainfall.

The Karnataka Plateau, located south of the Deccan Traps, is an undulating region with an average elevation of 600-900 metres. It is drained by rivers like the Krishna, Tungabhadra, and Cauvery. This region features ancient crystalline rocks and is known for its rich mineral deposits. The Telangana Plateau, to the northeast of the Karnataka Plateau, is also composed of ancient gneisses and granites. It is a semi-arid region with an average elevation of 500-600 metres. The Eastern Ghats, a discontinuous range, mark the eastern boundary, and are much older and more eroded than the Western Ghats.

Mineral Resources

The Deccan Plateau is a storehouse of various valuable mineral resources, making it economically significant. The region is particularly rich in metallic minerals. Iron ore deposits are found in abundance, especially in the Karnataka Plateau (e.g., Bellary-Hospet region) and parts of Telangana. These deposits are crucial for India's steel industry. Manganese ore is another important mineral, with significant reserves in Karnataka and Maharashtra. Bauxite, the primary ore for aluminium, is found in parts of Maharashtra and Karnataka.

Gold mines, such as the Kolar Gold Fields (KGF) in Karnataka, were historically very important, though most are now closed or have reduced operations. Uranium deposits have also been identified in parts of the plateau, particularly in Telangana. In terms of non-metallic minerals, limestone, used in cement production, is widely available. Granite and other building stones are also quarried extensively. The black soils derived from the Deccan Traps are excellent for agriculture, supporting crops like cotton, sugarcane, and oilseeds, which can also be considered a natural resource.

Water Resources and Rivers

The Deccan Plateau is drained by several major peninsular rivers, most of which flow eastward into the Bay of Bengal. The Krishna, Godavari, and Cauvery are the most prominent rivers originating in the Western Ghats and flowing across the plateau. The Godavari River is the largest peninsular river, often called the 'Dakshin Ganga'. It originates near Nashik in Maharashtra and flows through Maharashtra, Telangana, and Andhra Pradesh. The Krishna River originates near Mahabaleshwar in Maharashtra and flows through Maharashtra, Karnataka, and Andhra Pradesh/Telangana. The Cauvery River originates in Talakaveri in Karnataka and flows through Karnataka and Tamil Nadu.

These rivers are rain-fed and experience significant seasonal variations in water flow, with peak flows during the monsoon season. They are vital for irrigation, hydropower generation, and domestic water supply in the region. Numerous dams and irrigation projects have been built on these rivers, such as the Nagarjuna Sagar Dam on the Krishna and the Srisailam Dam. The eastward flow of most rivers is due to the general eastward slope of the plateau. The Narmada and Tapi rivers are exceptions, flowing westward into the Arabian Sea, forming rift valleys along their courses.

Important Keywords Explained

Deccan Trapsplace

A large igneous province located on the Deccan Plateau, formed by massive volcanic eruptions during the late Cretaceous period, around 66 million years ago. It consists of multiple layers of flood basalt, covering an area of approximately 500,000 square kilometres. These formations are responsible for the characteristic black soil (Regur) of the region.

Regur Soilconcept

Also known as Black Soil, it is characteristic of the Deccan Plateau, particularly in the Deccan Traps region. It is formed from the weathering of basaltic lava rocks. This soil is rich in clay content, highly retentive of moisture, and fertile, making it ideal for crops like cotton, sugarcane, and groundnuts. It is self-ploughing due to its expansive and contractile properties.

Western Ghatsplace

A mountain range that runs parallel to the western coast of the Indian peninsula, forming the western edge of the Deccan Plateau. It is a UNESCO World Heritage Site and one of the world's eight 'hottest hotspots' of biological diversity. The range acts as a major watershed for peninsular rivers and influences the monsoon rainfall pattern in India.

Additional Facts & Context

• The Deccan Traps cover an estimated area of 500,000 square kilometres.
• The average thickness of the Deccan Traps lava flows is about 2,000 metres in the west.
• The Godavari River, the largest peninsular river, has a length of approximately 1,465 km.
• The Krishna River is about 1,400 km long.
• The Cauvery River is approximately 800 km long.