Class 9th

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Answer the following questions briefly.
(i) What are tectonic plates?
(ii) Which continents of today were part of the Gondwana land? (iii) What is the bhabar?
(iv) Name the three major divisions of the Himalayas from north to south. (v) Which plateau lies between the Aravali and the Vindhyan ranges? (vi) Name the island group of India having coral origin.

Answer 2:
(i) The convectional currents present below the solid layer of Earth’s crust split the crust or the lithosphere into a number of large fragments. These fragments are called tectonic or lithospheric plates. (ii) The continents that were part of Gondwana land are Australia, Antarctica and South America. (iii) The bhabhar is that part of the Northern Plains where the rivers, after descending from the mountains, deposit pebbles. It is a narrow belt, having a width of about 8 to 16 km and lying parallel to the slopes of the Shiwaliks. (iv) The three major divisions of the Himalayas from north to south are the Great Himalayas/Inner Himalayas/Himadri (Northernmost division), the Lesser Himalayas/Himachal and the Shiwaliks(Southernmost division). (v) Malwa plateau lies between the Aravali and the Vindhyan ranges. (vi) Lakshadweep Islands are composed of small coral islands.

Distinguish between
(i) Converging and diverging tectonic plates
(ii) Bhangar and Khadar
(iii) Western Ghats and Eastern Ghats
Answer 3:
(i)The Earth’s crust is broken up into several lithospheric or tectonic plates. These plates are constantly moving atop the Earth’s mantle (semi-solid layer of molten rocks). Based upon their motion, tectonic plates are referred to as converging or diverging. Converging tectonic plates move towards each other and form convergent boundary. Diverging tectonic plates move away from each other and form divergent boundary. (ii) Bhangar is the terrace-like feature present above the flood plains of the rivers. It is composed of older alluvium. It is the largest part of the Northern Plain. The soil of this region contains calcerous deposits locally known as kankar. The newer, younger deposits of the flood plains are called khadar. This region is very fertile as it gets renewed almost every year. Hence, it is ideal for intensive agriculture. (iii)

Western Ghats| Eastern Ghats|
Mark the western edge of the Deccan Plateau| Mark the eastern edge of the Deccan Plateau| Continuous| Discontinuous and irregular|
Higher; average elevation is 900−1600 metres| Lower; average elevation is 600 metres| Lie parallel to the western coast along the Arabian Sea| Lie parallel to the eastern coast along the Bay of Bengal|

Describe how the Himalayas were formed.
Answer 4:
According to the Theory of Plate Tectonics, the Earth’s crust was initially a single, giant super-continent called Pangea. Its northern part was the Angara land and the southern part was the Gondwana land. The movement of the molten material below the Earth’s crust caused the crust or the lithosphere to break up into a number of large fragments called lithospheric or tectonic plates. Another important feature of the Earth’s crust at the time was the geosyncline—a narrow, shallow, elongated basin with a sinking bottom in which a considerable thickness of sediments were deposited by the rivers coming from Angara land and Gondwana land—called the Tethys. After separating from the Gondwana land, the Indo-Australian Plate drifted towards the north in the direction of the Eurasian Plate. This resulted in the collision of the two plates, and due to this collision, the sedimentary rocks in the Tethys got folded to form the mountain system of western Asia and the Himalayas.

Which are the major physiographic divisions of India? Contrast the relief of the Himalayan region with that of the Peninsular plateau. Answer 5:
The major physiographic divisions of India are:
(i) The Himalayan Mountains
(ii) The Northern Plains
(iii) The Peninsular Plateau
(iv) The Indian Desert
(v) The Coastal Plains...
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