Great Indian Plateau
The Great Indian Plateau lies to the South of the Great Northern Plains. This is the largest physiographic division of our country.
The topography consists of a series of plateaus and hill ranges interspersed with river valleys. Aravalli hills mark the north-western boundary of the plateau region. Its northern and north-eastern boundary is marked by the northern edge of the Bundelkhand Plateau, Kaimur and Rajmahal Hills. The Western Ghats (Sahyadry) and the Eastern Ghats mark the western and eastern boundaries respectively of this Great Plateau. Most of the area of the plateau has a height of more than 400 metres above sea level. The highest point of plateau region is the Anaimudi peak (2965 m). The general slope of this plateau is towards east.
The Great Plateau is the part of very ancient landmass, called Gondwana land. Because of their old age, all the rivers have almost attained their base level and have built up broad and shallow valleys.
River Narmada divides the peninsular block of India into two parts. The region lying to the north of the Narmada is called the Central Highlands and the region lying to the south of Narmada is called the penninsular plateau, more commonly referred to as the Deccan Plateau.
Barring Narmada and Tapti all the major rivers lying to the south of the Vindhyas flow eastwards to fall into the Bay of Bengal. The westward flow of Narmada and Tapi is assigned to the fact that they have been flowing through faults or rifts which were probably caused when the Himalayas began to emerge from the Tethys Sea of the olden times.
The Central Highlands
It extends between river Narmada and Great Northern Plains. The Aravallis form the west-northwestern edge of the Central Highlands. These hills extend from Gujarat, through Rajasthan to Delhi in the northeasterly direction for a distance of about 700 km. The height of these hills is about 1500 metres in southwest while near Delhi they are hardly 400 metres high. The highest peak of the Aravalli hills is Gurushikhar (1722m) near Mt. Abu.
Malwa plateau forms the dominant part of the Central Highlands. It lies to the southeast of Aravallis and to the north of Vindhyachal Range. River Chambal, Betwa and Ken drain the Malwa Plateau before they join Yamuna. The part of the Central Highlands which extends to the east of Malwa Plateau is known as Bundelkhand and is further followed by Baghelkhand and the well known Chhotanagpur Plateau. Vindhyachal Range forms the southern edge of Malwa Plateau. The Mahadeo Hills, Kaimur Hills and Maikal Range lie towards further east.
The valley of Narmada is situated between the Satpuras and the Vindhyas. River Narmada flows from east to west in this valley and falls into the Arabian Sea. This valley has been formed due to the subsidence of the land mass between the Vindhyas and the Satpuras.
The Peninsular Plateau (Deccan Plateau)
The shape of this plateau is triangular. One of the sides of this triangle is marked by the line joining Kanya Kumari with Rajmahal Hills and this line passes through the Eastern Ghats. The second arm is marked by the Satpura Range, Mahadeo Hills, Maikal Range and the Rajmahal Hills. The third arm is marked by the Sahyadris (Western Ghats). The area of this Penninsular Plateau is about 7 lakh square km and the height ranges from 500 to 1000 metres above sea level.
The Sahyadri Range forms the sharp edge of the Penninsular Plateau. Due to its location on the western margin of the Penninsular Plateau, the Sahyadri Range is also called Western Ghats.
The height of the Sahyadris increases from north to south. Anaimudi peak (2695 m) situated in Kerala is the highest peak of southern India. Anaimudi is a sort of tri-junction of the Annamalai Range, the Cardamom Hills and the Palani Hills.
Eastern Ghats running from southwest to northeast form the eastern edge of the Penninsular Plateau. This range is known as poorvadri also. The Eastern Ghats joins the Sahyadris at the Nilgiri Hills.
The Eastern Ghats are not continuous like the Sahyadris. Mahanadi, Godavari, Krishna, Pennar and Kaveri rivers have dissected this range at many places.