Lesson 1/34 min
The three physical regions
Key facts
- Bangladesh is the world's largest delta and lies in the tropical monsoon climate zone
- By physiography the country has three parts: Tertiary hills, Pleistocene terraces and the recent floodplains
- The average height of the hilly area is 2,000 ft (Khandokar)
The three regions at a glance
| Region | Share of the country | Where |
|---|---|---|
| Tertiary hills | about 12% | south-east, north and north-east: Sylhet, Habiganj, Mymensingh, Chattogram, Cox's Bazar, Chattogram Hill Tracts |
| Pleistocene terraces | about 8% | Barind in the north-west; Madhupur and Bhawal in the centre; Lalmai hills in Cumilla |
| Recent floodplains | about 80% | the rest of the country, built by rivers |
Did you know?: The shares (12%, 8%, 80%) match Banglapedia, which uses the same three-part division as the book.
Tertiary hills
- Formed when the European-Asian tectonic plates collided, as the Himalaya rose
- The oldest of the three physical regions
- They are fold mountains
- Related ranges: the Himalaya, the Lushai hills of Assam and the Arakan hills of Myanmar
- The northern hills are locally called tila (no higher than 248 m); the south-eastern hills are called dhibi (average 610 m)
Watch out: The book says the Tertiary hills date from about 130 million years ago and the Pleistocene to about 25,000 years ago. These do not match the geological timescale (the Tertiary began about 66 million years ago), so both numbers are unconfirmed. For exams, the safe fact is that the Tertiary hills are the oldest.
Pleistocene terraces
- Terraces of old alluvium, believed to have formed in the Pleistocene
- ‘Sopan’ region means terrace land (chattar-bhumi)
- Higher than the floodplain; Barind stands 6-12 m above it
Recent floodplains
- About 80% of the land, apart from the Tertiary hills and Pleistocene terraces
- Built from silt of the Padma, Meghna, Jamuna and Brahmaputra
- Area 124,266 sq km (Khandokar book)
- Slopes gently from the north towards the coast; the Sundarbans lie almost at sea level
- The lowlands are floodplain; the feared greenhouse-effect damage is the drowning of low land
Check yourself
Which of the three physical regions is the oldest?
At a glance
- 1
Three parts: Tertiary hills (~12%), Pleistocene terraces (~8%), floodplains (~80%).
- 2
The Tertiary hills are the oldest and are fold mountains; tila in the north, dhibi in the south-east.
- 3
The terrace region means chattar-bhumi, formed in the Pleistocene.
- 4
The floodplain is silt of the Padma, Meghna, Jamuna and Brahmaputra; the Sundarbans are almost at sea level.
- 5
Bangladesh is the world's largest delta, in the tropical monsoon zone.