A1.i)According to the “Theory of Plate Tectonics”,the earth’s crust is made up of rigid plates.They comprise the earth’s solid upper crust as well as parts of the denser mantle below. ii)The crust has been formed out of seven major and some minor plates. Q2.The colour of soil various from one place to another .Why? A2.The colour of the soil varies from place to place because soils are formed of different types of rocks. Q3.Discuss the three types of plate movements. A3.1Convergent Movement: i)Convergent movement is caused when two plates come or move towards each other and form convergent boundary. ii)In the event of two plates coming together,they may either collide and crumble or one may slide under the other. 2.Divergent Movement: i)Divergent movement is caused when two plates move away from each other and form divergent boundary. ii)In the event of two plates moving away,they may form a new crust or the sea floor spread. 3.Transform Movement: i)Transform movement is caused when two plates move horizontally past each other and form transform boundary.
ii)When two plates slide past each other,a major tear fault (fracture)results. Q4.Differentiate between converging and diverging plates. A4. Converging Plates When some plates come or move towards each other they are called converging plates. They may collide and crumble or one may slide under the other Diverging Plates When some plates move away from each other they are called diverging plates. They may form new crust or the sea floor spreads. Q5.Which continents of today were part of the Gondwana land? A5.Gondwana land includes Australia,Antarctica and South America,Africa. Q6.Describe how Himalayas were formed? A6.Himalayas were formed due to the following reasons: 1.
The oldest landmass was the part of Gondwana land. 2.
The convectional currents split the crust into number of pieces , thus leading to the drifting of Indo-Australian plate after being separated from the Gondwana land towards north. 3)A piece of Gondwanaland drifted northwards towards the Eurasian plate. 4)The northward drift resulted in the collision of Eurasian plate.5)Due to this collision the sedimentary rocks which were accumulated in the Tethys were folded to form the mountain system of Himalayas. Q7.Describe the features of Himalayas? A7. 1. Himalayas geologically young and structurally fold mountains stretch over the northern borders of India. 2.These mountain ranges run in west-east direction from the Indus to the Brahmaputra.
The Himalayas represent the loftiest and one of the most rugged mountain barriers of the world. 4.
They form an arc which covers the distance of about 2400 kms. 5.
Their width varies from 400 kms in Kashmir to 150kms in Arunachal Pradesh. 6.
The altitudinal variations are greater in the eastern half than those in the western half. 7.
The Himalayas consist of three parallel ranges in its longitudinal extent. Q8.Why Himalayas are called Geologically young and structurally fold mountains? A8.i)The Himalayas are called young fold mountais because they are,in comparison to the Aravallis much younger in age. ii)They are formed by the folding of the sea-bed of the Tethys Sea in the last mountain building (geological)period. iii)They comprise mainly three east-west running ranges:Greater and the Lesser Himalayas and the Shivaliks. iv)Their main characteristics are:high peaks,steep valleys and slopes,gorges,glaciers,etc.They all indicate that the mountains are very young. Q9.Which are the major physiographic divisions of India? A9.The major physiographic divisions of India are as follows: i)The Himalaya Mountains ii)The Northern Plain. iii)The Peninsular Plateau iv)The Indian Desert v)The Coastal Plains vi)The Islands.
Q10.Name the three major divisions of Himalayas from North to South. A10.The three major division of Himalays from north to south are: i)Himadri or Great or Inner Himalayas ii)Himachal or Lesser Himalayas iii)Shiwaliks Q11.Discuss the features of: i)Himadri/Great or Inner Himalayas. ii)Himachal/Lesser Himalayas iii)Shiwalik A11.i)Himadri: a)Northern most range as the great or inner Himalayas b)It is the most continuous range consisting of loftiest peaks with an average height of 6000metre. c)It contains all the prominent peaks which is always perennially snow bound. d)The core of this part of Himalayas is composed of granite. ii)Himachal: a)Lies to the south of Himadri. b)The ranges are mainly composed of highly compressed and altered rocks. c)The altitude varies betweem 3700m and 4500m with average with of 50 Kms.Pir Panjal range forms the longest and the most important range,the Dhaula Dhar and the Mahabharat ranges and prominent once. d)Its is well known for its hill stations like the famous valley of Kashmir ,Kangra and Kullu valley.
iii)Shiwaliks: a)Outer most range of the Himalayas b)They extend over a width of 10-50Kms with an altitude between 900m and 1100m. c)These ranges are composed of unconsolidated sediments brought down by the rivers from the main Himalayan range located further north. d)These valleys are covered with gravel and alluvium. e)The longitudinal valley lying between lesser Himalayas and the Shiwaliks are known as Duns.Dehra Dun,Kotli Dun, and Patli Dun are some of the well known Duns. Q12.The Himalayas have been divided on the basis of regions from west to east.How/Explain. A12.The west-east division of the Himalays are as follow: 1.The Punjab Himalayas. i)This is the wester part of Himalayas that lies between the Indus and the Sutluj rivers.It is also known as the Kashmir and Himachal Himalayas. ii)The Himalayas are much border here and consist of many ranges,valleys and uplands. 2.The Kumayun Himalayas. i)This is the middle part of the Himalayas in India. ii)It lies between the Sutlej and the Kali rivers,mainly in the Uttaranchal. 3.The Nepal Himalayas i)This is the middle part of the Himalayas ii)It lies between the Kali and the Tista rivers.
4.The Assam Himalays i)This is the eastern Himalayas. ii)This part lies between the Tista and the Dhiang rivers.