The Deccan Plateau

The Deccan Plateau is one of the oldest and most stable landmasses in India, a vast triangular tableland that forms the core of the southern peninsula. Its character is shaped not by the young, crumpled mountains of the north, but by ancient crystalline rocks, horizontal lava sheets, and a gentle eastward tilt. Understanding it means seeing how geology, drainage, and relief combine to create a distinct physiographic unit.

The plateau is bounded on the west by the Western Ghats and on the east by the Eastern Ghats, giving it a clear structural identity. Its northern boundary is marked by the Satpura and Vindhya ranges, which separate it from the northern plains. The entire plateau slopes gently from west to east, a fact that dictates the direction of its major rivers — most of them rise in the Western Ghats and flow eastward to empty into the Bay of Bengal.

Geologically, the Deccan Plateau is built of very old crystalline, igneous, and metamorphic rocks. These are hard and resistant, which is why the plateau has remained a stable block for millions of years, largely unaffected by the mountain-building movements that shaped the Himalayas. Over parts of the northwestern Deccan, however, the ancient rocks are covered by a thick layer of basaltic lava flows, known as the Deccan Traps. These lava sheets are nearly horizontal and have given rise to a distinctive stepped or terraced landscape, locally called bhagar or bhat.

The plateau is not a single uniform surface. It is broadly divided into three major sections based on relief and geological history. The Maharashtra Plateau in the west is the largest of these, composed mainly of the Deccan Traps. Its western edge is formed by the Western Ghats, which rise steeply from the narrow coastal plain. The plateau surface here is uneven, dissected by rivers into flat-topped hills and valleys. The Karnataka Plateau lies to the south, built largely of ancient crystalline rocks rather than lava. Its western margin is also the Western Ghats, but here the plateau is higher and more rugged, with the famous hill stations of the Nilgiris and the Palni hills marking its southern extension. The Telangana Plateau in the east is a drier, more undulating region, bounded by the Eastern Ghats on its eastern side and merging gradually with the Maharashtra and Karnataka plateaus to the west.

The Western Ghats themselves are not a single continuous range but a faulted escarpment, running almost parallel to the west coast. They rise abruptly from the coastal plain, reaching average heights of 900 to 1,100 metres, with some peaks exceeding 2,400 metres. The Eastern Ghats, by contrast, are lower and discontinuous, broken by the broad deltas of rivers like the Godavari, Krishna, and Kaveri. Because the plateau tilts eastward, the Western Ghats form the main water divide; almost all the peninsula's rivers originate there and cut across the Eastern Ghats to reach the sea.

The plateau's drainage is therefore trellis-like in the west, where rivers follow the joints and fractures of the basaltic rocks, and dendritic in the east, where the softer, older rocks allow a more branching pattern. The rivers have carved deep valleys and gorges in the Western Ghats, but in their lower courses, across the Telangana and coastal regions, they have built wide, fertile deltas.

The Deccan Plateau is also marked by a number of distinct hill ranges and isolated peaks. The Satpura range forms its northern rampart, while the Vindhyas lie further north, separated from the Satpuras by the Narmada valley. Within the plateau itself, the Mahadeo and Maikal hills rise in the central part, and the Ajanta and Satmala ranges run across the Maharashtra plateau. The Nilgiri hills, where the Western and Eastern Ghats meet, are a prominent highland, and the Anaimalai and Cardamom hills continue southward into the Western Ghats.

Climatically, the plateau experiences a range of conditions. The western edge, facing the Arabian Sea, receives heavy monsoon rainfall, supporting dense forests. The interior, especially the Telangana region, lies in the rain shadow of the Western Ghats and is considerably drier. This rainfall gradient is reflected in the natural vegetation — from tropical evergreen and semi-evergreen forests in the west to dry deciduous and thorn forests in the east.

The soils of the plateau are as varied as its rocks. The black cotton soil, or regur, derived from the weathering of the Deccan Traps, is the most famous, covering much of Maharashtra and parts of Karnataka and Telangana. It is highly moisture-retentive and ideal for cotton cultivation. The Karnataka plateau, on the older crystalline rocks, has red and laterite soils, which are less fertile and more prone to erosion. …