West Bengal has all the three major land forms, viz., mountains, plateaus, and plains including a delta.
1. Young Fold Mountains of the North:
The Middle and Outer Himalayan parts of Darjeeling and Jalpaiguri districts of West Bengal constitute the young fold mountain region.
The mountains rise abruptly from the Tarai plains and reach the eternal snows in Sikkim, dominated by Kanchanjunga. It is a web of lofty knife-edged ridges, steep slopes and often deep gorges. The region has been dissected by the deep gorge of the north-south running Tista.
2. Uplands of the Western plateau Fringe:
The oldest part of West Bengal constitutes this region. It covers the Purulia district and the western parts of Midnapur, Bardwan, Birbhum and Bankura districts. It is an eroded remnant of the adjoining Chota Napur plateau. It presents a landscape of rolling uplands with low isolated grey hillocks (called dungri) here and there. The highest point is Gorgaburu (677 m.) at Ajoclhya Pahar in Purulia. These uplands gradually slope towards the east and south-east.
3. Riverine Plains and Deltas
The riverine plains and delta region of West Bengal stretches from the northern foothills to the southern coasts. In spite of its flat relief, it presents six distinct units:
- Tarai and Duars: a narrow transition belt between the flat plains and the towering mountains. It has a southerly slope which is greater than that of the other plains.
- Northern Plains: the Northern Plains extend from the Ganga to the Tarai through Maldah, West Dinajpur, Cooch-Bihar Districts and the southern parts of Jalpaiguri and Siliguri subdivisions. It is gift of the Ganga and her tributaries. The region can be three types. They are (i) Tal, (ii) Barind, and (iii) Diara. The Diara plain between the Kalindi and the Ganga is the youngest and most fertile. It contains new Gangetic alluvium. The Barind at the centre in Maldah contains alluvium of an ancient Ganga delta, mostly red clay. In the past the Bay of Bengal extended into Maldah. The red clay represents the oxidized off-shore bars of this ancient sea-shore. Its surface rolls down in step-like terraces to furrowed river beds. The rest of the area to the north is a huge lake filled plain called Tal. Tal means lake. It is much lower and flatter that the Tarai to its north and the Barind to its south. The Tal region is flood prone.
- Rarh Plain: the Rarh plain embraces Birbhum and parts of Murshidabad, Burdwan, Bankura, and Midnapur. It is a gift of the plateau streams. From the degraded rolling plateau it laps eastward overlapped by the Bhagirathi plains to the east.
- The Ganga Deltas: A part of the Ganga deltaic plains is in West Bengal. It spreads south from the Ganga-Padma to the Bay, flanked on the west by the Rarh and by Bangladesh to the east. It is a vast, flat plain, covered with a network of distributaries of the Ganga-Padma. The chief distributaries are the Bhagirathi-Hooghly, Jalangi-Bhairab, Kumar, Mathabhanga—Churni—Ichhamati. The land nowhere rises above 20 m. The slope of the country is away from the streams i.e. towards south (Bay of Bengal). A maze of creeks flow from the main streams. The inter stream areas are not high doab but saucer shaped depressions. Swamps and lakes called daha, bil or jhill often fill up these low tracts.
- The Sundarbans: This is the active part of the Ganga delta. It extends between the Hooghli mouth and Bangladesh comprising 15 thanas (police stations) of south 24-Parganas. To its north and east lie the mature and the moribund delta. The Sundarbans is named after the beautiful ‘SUNDARI’ redwood tree of the tidal forests. The region is still a terra incognita of swampy islands, rivers and mysterious tidal creeks. The land gradually declines to the seaboard which is half-land, half-water, rising and falling with the tides.
- The Sandy Coastal Plains: A 15 km. wide coastal strip of Midnapur district extends between the Bengal-Orissa border in the west and the Haldi River and mouths of the Hoogly River in the east. This strip has been built up jointly by riverine sand and silt. The beautiful Digha sandy beach has appeared as the sea has retreated. The sea has also left behind salt creeks and marshes. There is a belt of dunes at the back.