NCERT CLASS-9 GEOGRAPHY
CHAPTER-2 [PHYSICAL FEATURES OF INDIA]
- India has all major physical features of the earth i.e, mountains, plains, deserts, plateaus and islands.
- Theory of plate tectonics- The crust (upper part) of the earth has been formed out of 7 major and some minor plates.
- Movement of these plates results in building up of stresses within the plates and the continental rocks above leading to folding, faulting and volcanic activity.
- Plate movements- 3 types-
= some plates come towards each other and form convergent boundary.
= some plates move away from each and form divergent boundary.
= some plates move horizontally past each other and form transform boundary.
- Oldest landmass (the peninsular part), was part of the Gondwana land.
- Gondwana land includes India, Australia, South Africa, South America and Antarctica as one single land mass.
- Gondwana land- southern part of ancient super continent Pangea with Angara land int eh northern part.
- The Himalayan uplift out of the Tethys sea and subsidence of the northern flank of the peninsular plateau resulted in the formation of a large basin.
- Peninsular plateau one of the most stable land blocks.
- Himalayan mountains form an unstable zone.
- The peninsular plateau, composed of igneous & metamorphic rocks with gently rising hills and wide valleys.
- Major physiographic divisions of India-
1. The Himalayan mountains
2. The Northern Plains
3. The Peninsular Plateau
4. The Indian Desert
5. The Coastal Plains
6. The Islands
THE HIMALAYAN MOUNTAINS-
- Geologically young, structurally fold mountains.
- Mountains ranges run Ina west-east direction of about 2400 km.
- Width varies from 400 km in Kashmir to 150 km in Arunachal Pradesh.
- Altitudinal variation greater in eastern half than those in the western half.
- Consists of 3 parallel ranges, a no. Of valleys lies between these ranges.
- Northernmost range, know as the Great or Inner Himalayas or the Himadri.
= most continuous range consisting of the loftiest peak with an average height of 6000m.
= folds of great Himalayas are asymmetrical in nature.
= core composed of granite.
= perennially snow bound, and glaciers descend from this range.
- Range lying to the south of Himadri, Himachal or lesser Himalayas.
= composed of highly compressed and altered rocks.
= Altitude varies between 3700 and 4500m, average width of 50km.
= The Pir Panjal range forms the longest and the most important ranges, the Dhaula Dhar and
the Mahabharat ranges are prominent ones.
= consists of the famous valley of Kashmir, the Kangra and Kullu valley in Himachal Pradesh.
= well known for hill stations.
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