From the geographical and physiographic point of view, Punjab falls
into two regions: the Shivaliks and the Plain.
This region covers the outer range of the Shivalik Hills
and is approximately 6 to10kms in width. Their height ranges between 400
and 700 metres above sea level. It consists of conglomerates, clays and
silts-all having the character of fluviatile deposits of rivers and stream.
The origin of the Shivalik Hills has been explained
differently by different geologists. One view advanced is that the present
Shivalik Range is the flood plain of a big river to whom pilgrims gave
the name Indo-Brahm and Pascoe- Shivalik. According to another view the
basin of deposition was a continuous lagoon or fore-deep formed in front
of the Himalayan Range.
The low range of the Shivalik Hills separates the Himalayas
from the plains. The Shivalik region covers the eastern most areas of
Ropar, Hoshiarpur and Gudaspur districts and runs like a wall, north-west
to south-east, separating the Sirsa and Una valleys of Himachal Pradesh
from the plain areas towards the west.
The Punjab plain is a part of the great Indo-Gangetic
plain which is a synclinal basin formed by the elevation of the Himalayas.
One group of geologists hold this area to be afore-deep formed in front
of the stable peninsular India at a time when the Tethyan Sediments were
thrust southwards and compressed against that stable block. Another group
assumes the Indo-Gangetic plain to be the site of a rift valley. The rivers
of the region indicate that the plain is the result of recent deposition
and these very rivers have formed the plain.
The Punjab plain lies between 180 and 300 meters above
sea level. It is higher near the Shivalik Hills but slopes away from them.
The tract covering central Punjab ranges between 230 and 270 metres above
sea level while western Bhatinda and Ferozepur districts lie below 230
metres above sea level. The land slopes from east to west. The gradient
is much more in the east than in the west.
The work of the two important agents of mechanical weathering,
wind and running water, is well exemplified in this area. The action
of wind in the western side and the action of running water near the Shivalik
Range have modified the face of this region to impart to the different
tracts a contrasting look.