Indo-Brahma river
Also called: Shiwalik river · Topic: Drainage System of India: Rivers, Basins and Patterns · NCERT: Class 11, Ch 3 "Drainage System"
Meaning
The Indo-Brahma river, also called the Shiwalik river, is an idea about the past. It says that in the Miocene period, about 5–24 million years ago, one huge river flowed along the foot of the Himalayas. It ran from Assam to Punjab and Sind and emptied into the Gulf of Sind. The evidence is the unbroken line of Shiwalik deposits: lake and river sands, silt, clay, boulders and conglomerates (rock made of pebbles cemented together). The river later split into three systems: the Indus in the west, the Ganga in the centre and the Brahmaputra in the east.
Example
Two events caused the split. In the Pleistocene, uplift in the western Himalayas, including the Potwar plateau (now in Pakistan's Punjab), raised the Indus–Ganga divide. Later, in the middle Pleistocene, the Malda gap between the Rajmahal hills and the Meghalaya plateau sank. This turned the Ganga and Brahmaputra towards the Bay of Bengal.
Don't confuse with
- Antecedent river: a real river that is older than the mountains it cuts through, such as the Satluj. The Indo-Brahma is a hypothetical river that no longer exists.
Related concepts
- Himalayan drainage system
- Antecedent river
- Indus-Ganga water divide
- Water tower of Asia
- Mansarovar and Rakas Tal