is made up of new alluvium, and here the Kalindi River joins the Mahananda River. The area north of the Kalindi River is a lowland covered with swamps and beels (small water bodies) and is known as tal. In contrast, the area south of the Kalindi is a very fertile land and is known as diara. The plain south of Jalpaiguri, Alipurduar, and Cooch Behar district is also made of new alluvium deposited by numerous rivers including the Teesta, Torsa, Raidak, Jaldhaka, Sankosh, Balason, Punarbhaba, and Atrai. Rarh region Rarh is the region that intervenes between the Vajjabhumi and the Ganges Delta. This region is composed of parts of the districts Murshidabad, Birbhum, Bankura, Purba Bardhaman, Paschim Bardhaman, Purba Medinipur, and Paschim Medinipur. The region is about 50–100 m above sea level, and is believed to consist of soil from the Deccan plateau. The area is formed by the silt brought by the tributaries of the Bhagirathi, Mayurakshi River, Ajay River, Damodar, and Rupnarayan rivers, which flow through the red laterite soil of the western plateau region. The land is sloped from west to southeast, and the formation of natural levees along the riverbanks is a common phenomenon. Coastal plain A small coastal region is on the extreme south of the state. A part of the district of Purba Medinipur along the Bay of Bengal constitutes the coastal plain. This emergent coastal plain is made up of sand and mud deposited by rivers and wind. Parallel to the coast are areas of sand dunes and marsh. The Digha dunes lie nearest to the Bay of Bengal, while the Kanthi dunes are the farthest from it. In some areas, dunes occur at a distance of 15–16 km from the coast and are 11–12 m high. Western plateau and high lands The western part of Purulia, Bankura, Birbhum, Bardhaman, and Paschim Medinipur districts constitute the western plateau and highlands, which form the eastern fringes of the Chota Nagpur Plateau. Geologically, this area is made of igneous rocks of the Archaean era as well as coal-bearing mudstone and quartzite rocks of Carboniferous period. Because of long and continuous erosion, the whole region has been transformed into an undulating peneplain. This area is interspersed by small monadnocks locally known as tila. Some of the important hills in the area include Ajodhya Hills (677 m), Panchet (643 m), and Baghmundi in Purulia, and Biharinath (452