It is fairly universally agreed that the depositional action of rivers from these two landmasses filled a deep depression located between the Peninsular and Himalayan regions, resulting in the formation of this huge plain. Divergent viewpoints have been expressed, however, on the cause of the Great Depression and the process of resolving it. According to Wadia, these plains were formerly a deep depression or furrow that ran between the Peninsula and the mountain ranges. The eminent Austrian geologist Edward Suess proposed that a "foredeep" formed in front of high Himalayan crust-waves when they were slowed in their southerly progress by the Peninsula's inflexible solid terrain. This foredeep resembled a huge syncline, with alluvium deposited from the Himalayan and Peninsular rivers. This was eventually filled with alluvium, resulting in the formation of the Great Plain of North India. It is supported by hard, crystalline rocks that connect the region to the Himalayan and Peninsular blocks. Sir Sydney Burrard, on the other hand, believes that the Indo-Gangetic alluvium hides a deep fissure, or fracture, in the earth's sub-crust that is several thousand metres deep, with trash filling the hollow. Sub-crustal fissures or rifts, he believes, play a crucial role in geotectonics. 'Rift Valleys' are sunken tracts between parallel, vertical dislocations. The rift valley that gave birth to this plain was around 2400 kilometres long and hundreds of metres deep, and it extended between the Himalayan peaks and the Peninsula. His conclusions were based on certain discrepancies in the observations of plumb line deflections and other geodetic considerations. He went on to describe the Narmada and Tapti rift valleys in Peninsular India. Scholars such as Hayden and R.D. Oldham, as well as other Geological Survey of India scientists, have questioned Burrard's interpretation of the Indo-Gangetic depression. The principal criticism to Burrard's theory is that there is no evidence of a rift valley on the Peninsula's northern edge, and that such a large rift valley is impossible to create.

Many geologists and geographers recently expressed the opinion that sediment deposited at the Tethys Sea's bed was folded and distorted due to the Peninsula's northward migration. As a result, the Himalayas were constructed, as well as a trough to the south. This depression or trough, which lies at the foot of the mountain, is almost certainly related to the latter. The infilling of the fore-deep stretched down between the advancing Peninsular Block and the Himalayas is represented by the Great Plain. During a period of high gradational activity, the infilling was done by deposition of mountain detritus transported by numerous rivers issuing from them. The majority of this plain is made up of Pleistocene and Recent geological formations.

As a result, the surface deposits of this tract date from the latest epoch of the earth's history, concealing earlier peninsular and other formations beneath them.