Question

how did the nothern plains formed ncert 9

Answer 1

The northern plains have been formed by the interplay of the three major river systems the Indus, the Ganga and the Brahmaputra along with their tributaries.
The Himalayan uplift out of the Tethy’s sea and subsidence of the northern flank of the Peninsular plateau resulted in the formation of a large basin. In due course of time, this depression gradually got filled with the deposition of the sediments by the rivers flowing from mountains in the north. A flat land with extensive alluvial deposits by these rivers led to the formation of the Northern Plains of India.
With a rich soil cover, combined with adequate water supply and favourable climate, it is agriculturally a very productive part of India..
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Answer 2

1)The Northern Plain was formed by the deposits brought in by the three major rivers and their tributaries. (i) The Indus (ii) The Ganga (iii) The Brahmaputra 2)Alluvium was deposited at the foot–hills of the Himalayas for millions of years. These deposits are now the fertile Northern Plains. 3)Alluvium is soil or sediments deposited by a river or other running water. Alluvium is typically made up of a variety of materials, like fine particles of silt and clay and larger particles of sand and gravel. The Indo-Gangetic belt is the world's most extensive expanse of uninterrupted alluvium. The plains are flat and mostly treeless, making it conducive for irrigation through canals. The area is also rich in ground water sources. I hope this it will be helpful for you Please mark as brainliest