Question

How the northern plains were formed?
A. By the interplay of three river systems Indus, Ganga, and the Brahmaputra
B. By the interplay of two river systems Narmad and Tapi
C. By the interplay of two river systems Godavari and Krishna
D. By the interplay of all these river systems

Answer 1

Hint: The youngest physiographic feature in India is the northern plains. They lie south of the Shivaliks, separated by the Frontal Fault of the Himalayas (HFF). A wavy, irregular line along the northern border of Peninsular India is the southern boundary. The plains are bordered by the Purvanchal hills on the eastern side.

Complete Answer:
The northern portion of the Indian Peninsula has subsided due to the rising of the Himalayas in the Tethys Sea and has formed a large basin. Sediments from the rivers which came from the mountains in the north and from the peninsula in the south filled the basin. The formation of the northern plains of India contributed to these vast alluvial deposits.
The northern plains make up the world's largest alluvial tract. These plains range from west to east for nearly 3200 km. The northern plain of India, along with its tributaries, is created by three river systems, i.e. the Indus, the Ganga, and the Brahmaputra. The average distance of these plains ranges from 150 km to 300 km. The width of the northern plains usually rises from east to west (90-100km in Assam to about 500km in Punjab).
The precise alluvium depth has not been entirely determined yet. The average depth of alluvium on the southern side of the plain ranges between 1300-1400 m, according to recent reports, while the depth of alluvium rises towards the Shiwaliks. In parts of Haryana, a record depth of over 8000 m has been achieved.
Its main feature (200m-291m) is the extreme horizontality of this monotonous plain. A watershed between the Indus system and the Ganga system forms the highest elevation of 291 m above mean sea level near Ambala).
So, the correct answer is Option A.

Note: The rivers descending from the mountains accumulate pebbles in a narrow belt between 8 and 16 km in diameter, parallel to the Shiwaliks' slopes. This area is referred to as bhabar. In this Bhabar belt, all the streams disappear or vanish. The streams and rivers re-emerge in the southern portion of this belt and create a wet, swampy, and marshy area called terai. Once upon a time, this was a thickly forested area full of wildlife.