Physiographic Divisions of the Himalaya

In this article we will discuss Physiographic Divisions of the Himalaya

In this article, we will discuss Physiographic Divisions of the Himalaya. So, let’s get started.

Physiograpic Divisions of the Himalaya

For a systemeyic study of the physiography and relief, the Himalaya may be divided into the following four divisions from north to south :

The Trans-Himalaya
The Trans-Himalayas are about 40 km wide. They contain the Tathys sediments.  The rocks of this region contain fossils bearing marine sediments which are underlain by “Tertiary granite”, it has partly metamorphosed sediments and constitutes the core of the Himalayan axis. it has a great accumulation of debris in the valleys of defeated streams which could not maintain their southerly course across the rising barrier of the Himalaya.

The Greater Himalaya
The Greater Himalaya rise abruptly like a wall north of the Lesser Himalaya. The MCT separates
the Greater Himalaya from the Lesser Himalaya The Greater Himalaya are about 25 km wide
with an average height above 6100 m (Wadia, D.N.). Almost all the lofty peaks of the Himalaya,
Mt Everest Kanchanjunga. Nanga Parbat. Gasherbrum, Manaslu, Dhaulagiri, Annapurna,
Gosainthan, Cho-Cyu, Nanda-Devi, Kamet. Badrinath Nanda Devi, etc., lie in this zone. The
Greater Himalaya are composed of crystalline, igneous or metamorphic rocks (granite, schists,
and geneiss). The basal complex of the Himalaya is Archaean. At places, due to heavy thrust, older rocks are found overlying the newer rocks The Greater Himalaya are almost a contiguous range. The range has very few gaps mainly provided by the antecedent rivers. The Greater Himalaya receive less rainfall as compared to the Lesser Himalaya and the Shiwaliks. Physical weathering is pronounced. Erosion is, however, less effective over the Greater Himalaya as compared to the Lesser Himalaya. Being lofty, they have very little forest area.                        

The Lesser Himalaya
The width of the Lesser Himalaya is about 80 km with an average height of 1300-4600 m.
It consists, generally, of unfossiliferous sediments or metamorphosed crystalline. The main
rocks are slate, limestone and quartzites. Along the southern margin of the Lesser Himalaya
lies the autochthonous belt of highly compressed Upper Palaeozoic to Eocene rocks, often
containing volcanic material. Examples of autochthonous belts are found between Murree
and Panjal thrust in Kashmir, Giri thrusts in the Shimla region and Krol and MBT in Garhwal
region. This region is subjected to extensive erosion due to heavy rainfall, deforestation, and
urbanisation

The Shiwaliks or Outer Himalaya/Sub-Himalaya
The Shiwaliks extend from Jammu Division of Jammu and Kashmir territory to Assam. In width,
Shiwaliks vary from 8 km in the east to 45 km in the west with an average elevation of about
900–1500 m above sea level. It is not a continuous range. It is broader in the west and narrows
down in the east. Between the Shiwaliks and the Lesser Himalaya are longitudinal valleys called
Doons/Duns. Some of the important Duns are Dehra Dun, Potli, Kothri, Kathmandu, Chumbi, and Kyarda. The Shiwaliks are mainly composed of sandstones, sand-rocks, clay, conglomerates and limestones, mostly belonging to the Upper Tertiary Period.

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