"Relief of Tamil Nadu The state is broadly divided into three physiographic divisions (a) The Hills, (b)The Plateau, and (c)The Plains. The major land forms and relief of Tamil Nadu as shown in Figure a) The Hills The hills of the state have two physical divisions: the Western Ghats and the Eastern Ghats meeting at the Doddabetta on the Nilgiris. The Western Ghats Although the whole length of the western part of the state are the Western Ghats, but only a portion of them is within the state of Tamil Nadu. The hills that are found in the state of Tamil Nadu are the Nilgiris, the Anaimalai, the Palani hills, the Kodaikanal hills, the Kutralam hills, the Mahendragiri/Agathiar hills. The height of The Nilgiris range varies from 1,600 meters MSL to 2,400 meters MSL. Its highest peak is the Doddabetta (2,673 m MSL)which lies on the east of Udhamandalam. It dips down towards the Coimbatore plateau. Udhagamandalam, Coonoor and Kotagiri are considered as the summer resorts on The Nilgiris. Anaimalai and the Palani hills meet at Anaimudi (2,695 m MSL), which was considered as the highest peak in south India. Their flat and undulating summits are havingseveral waterfalls below the summit level which show that they are undergoing the second cycle of normal erosion. The Palghat gap is the only break in the great mountain wall of the Western Ghats and which is the only natural gateway to Kerala. The Palani hills are low hills. Their height ranges from 1,500 meters to 2,000 meters. South of the Palani hills are the cardamom hills. Thekkadi sanctuary which is near the Periyar Lake lies on these hills. The Kodaikanal hills are the continuation of the Palani hills that fall under the Dindigul District. This is also considered as summer hill resort. In this hill only a rare species of flower Kurinji blossoms once in every 12 years. Kutralam hills lie in the district of Tirunelveli. The Mahendragiri is also in Tirunelveli district. Its height is 1,650 meters. This is also called the Agathiar hills. Further, the small hills on the west are the Varushanad hills. The Kambam Valley divides the Varushanad hills and the Andipatti hills. The Eastern Ghats Only a small segment of the Eastern Ghats lies in the state of Tamil Nadu. The line of discontinuous hills in the northern parts of the state is known as the Eastern Ghats.The Eastern Ghats extend in the form of disconnected number of hills such as the Javadhu, the Shevroys, the Kalrayans, the Kollimalais and the Pachaimalais. The Javadhu rises between 1,090 and 1,160 meters. Elagiri hill resort is located here. The Kalrayans are in the district of Viluppuram. The tributaries of the Vellar River are originated in these hills. The Shevroys are in the district of Salem. It is stretched around 160 km. Its height ranges from 1,500 to 1,600 meters. Yercaud on these hills isconsidered as the summer resort. The highest peak here is Solaikadu (1,640 meters). Bauxite is found in abundance here. The Pachaimalais are in Perambalur district. Here, black granite is mined. It is of very high quality and has no matchin the world. The Kollihills are in the district of Namakkal. Bauxite is found here as well. To the east of the Kollihills and the Pachaimalai are the Palamalai hills. Granites are found here as well. The Kanchamalai and the Chalk hills are in Salem district. b) The Plateaus The elevations of plateaus lie between 45 m to 150 m MSL and the general slope is towards east.It is an extensive landscape with a low relief. There is a sharp break in gradient all around its edges, except where the Cauvery breaks through it. There is fairly steep debris slope which rises to the surrounding hills. The topography is, however, undulating.In the west of this region lies the Baramahal Plateau, which is the continuation of the Mysore Plateau. The landscape lying between the Nilgiris and Dharmapuri is called Coimbatore 2 Plateau (150- 450m MSL). This plateau spreads over 2560 km of Salem, Coimbatore, and Erode Districts. Its height is between 1,800 m and 2,900 m MSL. This is separated from the Mysore plateau by the Moyar River in the north. c) The Plains The plains of Tamil Nadu are divided into three parts, (a)the Coromandel coastal plains; (b) the Cauvery Alluvial Plains and (c) the dry southern Coromandel coastal plains. The Coromandel coastal plain stretches to 992 km from Pulicat Lake to Cape Comorin and slopes towards the east. There are the Palar, the Cheyyar, Pennaiar and Velarbasins in these plains. In the south there are several ranges that cut across these plains. The Manimuthar rising from the Kalrayans has its own sub-basins here. The valley of the Vellar has artisan wells. The plateau and the plains are separated by the Chengam Canal in the north and athur Canal in the south. The northern or the Coromandel plains are in the districts of Thiruvarur, Kancheepuram, Vellore and Tiruvannamalai. The Cauvery Plains that ranged at less than 300 m MSL are drained by Cauvery and its tributaries. The plain extends over the districts of Dharmapuri, Salem, Thanjavur, Tiruchirappalli, Thiruvarur, Pudukkottai, Karur, and Nagapattinam. In the north are the Pachaimalai and the Kollihills, while Viralimalai is in the south. This is a fertile plain filled with alluvium. The Dry Southern Plains are seen as highlands which spread over the districts of Madurai, Sivaganga, Ramanathapuram, Virudhunagar, Thoothukkudi and Dindigul. These plains are covered with alluvial and aeolian deposits between the rivers Palar and the Cauvery. The plains are confined mainly between the coastlines and 150 m contour. Typical coral reefs on the east coast occur at about 3 meter above the sea level in the Pamban Island at the head of the Gulf of Mannar. Along the coast, there is a narrow belt of sand dunes, which rise to about 10 m on the Tuticorin coast.Further to south, in Tirunelveli district , the red sand hills, locally known as ‘terries’, rise to over 50 m behind the sands. The rest of the plains are mainly alluvial, formed by the fast-flowing rivers, of which the Cauvery in the north and the Tamiravaruni in the south deserve mention. These rivers have wide deltaic formations at their mouths.Source: Administrative Atlas of Tamil Nadu, Government of Tamil Nadu"