Facts that Matter | Extra Documents & Tests for Class 9 PDF Download

• India is a large landmass formed during different geological periods which has influenced her relief. Other processes such as weathering, erosion and deposition have also influenced her relief.
• According to the Theory of Plate Tectonics, the crust or the upper part of the earth has been formed out of seven major and some minor plates.
• The movement of the plates results in the building up of stresses within the plates and the continental rocks above leading to folding, faulting and volcanic activity.
• These plate movements are of three types — convergent boundary, divergent boundary and transform boundary.
• The movement of these plates has influenced the evolution of the present landform features of India.
• The oldest landmass was a part of the Gondwana land which included India, Australia, South Africa, South America and Antarctica as one single landmass.
• The land of India displays great physical variations. The physical features of India can be grouped under the following physiographic divisions:

(i)    The Himalayas stretch over the northern borders of India. These mountain ranges run in a 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. They consist of three parallel ranges in its longitudinal extent:
– The northernmost range is known as the Great or Inner Himalayas or the Himadri. It contains all the prominent Himalayan peaks.
– The range lying to the south of the Himadri is known as Himachal or lesser Himalayas. This range consists of the famous valley of Kashmir, the Kangra and Kullu Valley in Himachal Pradesh.
– The outermost range of the Himalayas is called the Shiwaliks. These valleys are covered with thick gravel and alluvium.
– Besides the longitudinal divisions, the Himalayas have been divided on the basis of regions from west to east. These divisions have been demarcated by river valley.
(ii)    The Northern Plains have been formed by the interplay of three major river systems – the Indus, the Ganga and the Brahmaputra. This plain is formed of alluvial soil. It is agriculturally a very productive part of India.
•    This plain is broadly divided into three main regions:
– The Punjab Plain, formed by the Indus and its tributaries. The larger part of this plain lies in Pakistan.
– The Ganga Plain extends between Ghaggar and Teesta rivers.
– The Brahmaputra Plain extends between Patkai Bum, Purvanchal hills, Naga hills in the east, and Mikir hills, Garo-Khasi-Jaintia hills and Meghalaya Plateau in the south.
•    The Northern Plains also have diverse relief features. According to the variations in relief features, these plains can be divided into four regions:
– The rivers, after descending from the mountains deposit pebbles in a narrow belt lying parallel to the slopes of the Shiwaliks. It is known as Bhabhar. All the streams disappear in this bhabhar belt.
– South of this belt, the streams and rivers re-emerge and create a wet, swampy and marshy region known as Terai.
– The largest part of the northern plain is formed of older alluvium and is known as Bhangar.
– The newer, younger deposits of flood plains are called Khadar. This is ideal for agriculture.
(iii)    The Peninsular Plateau is a tableland and has broad and shallow valleys and rounded hills. This plateau consists of two broad divisions – the Central Highland and the Deccan Plateau.
•    The part of the peninsular plateau lying to the north of the Narmada river covering a major area of the Malwa Plateau is known as the Central Highlands. These are wider in the west but narrower in the east.
•    The Deccan Plateau is a triangular landmass that lies to the south of the river Narmada. This plateau is higher in the west and slopes gently eastwards.
(iv)    The Western Ghats and the Eastern Ghats mark the western and the eastern edges of the Deccan Plateau respectively.
•    The Western Ghats are higher than the Eastern Ghats. Their average elevation is 900-1600 metres as against 600 metres of the Eastern Ghats.
•    Western Ghats lie parallel to the western coast. They are continuous and can be crossed through passes only. The Eastern Ghats are discontinuous and irregular and dissected by rivers draining into the Bay of Bengal.
•    The black soil area of the peninsular plateau is known as Deccan Trap.
(v)    The Indian Desert lies towards the western margins of the Aravali Hills. It is an undulating sandy plain covered with sand dunes. This region receives very low rainfall. It has arid climate with low vegetation cover.
(vi)    The Coastal Plains extend in the form of a strip along the Bay of Bengal on the east and the Arabian Sea on the west.
•    The western coast, sandwiched between the Western Ghats and the Arabian Sea, is a narrow plain. It consists of three sections:
— The northern part of the coast is called the Konkan.
— The central stretch is called the Kannad Plain.
— The southern stretch is called the Malabar Coast.
— Lake Chilka lies along the eastern coast.
(vii)    The Islands consist of the Lakshadweep Islands group and the Andaman and Nicobar Islands.
– The Lakshadweep Islands group lie close to the Malabar Coast of Kerala. This group of islands is composed of small coral islands.
– It covers small area of 32 sq km. Kavaratti Island is the administrative headquarters of Lakshadweep.
– The elongated chain of islands located in the Bay of Bengal is Andaman and Nicobar Islands. They extend from north to south. They are bigger in size and are more numerous and scattered.
– The entire group of islands is divided into two broad categories — the Andaman in the north and the Nicobar in the south.
– These island groups are of great strategic importance for the country.

Words that Matter

• Gondwana land: It is the southern part of the ancient super continent Pangea with Angara Land in the northern part.
• Tethys: The narrow and elongated oceanic trough lying between the Eurasian plate and Gondwana land.
• Himadri: The northernmost range of the Himalayas.
• Himachal or lesser Himalayas: The range lying to the south of the Himadri forms the most rugged mountain system.
• Shiwaliks: The outermost range of the Himalayas.
• Duns: The longitudinal valley lying between lesser Himalayas and the Shiwaliks.
• Distributaries: The rivers in their lower course split into numerous channels due to the deposition of silt. These channels are known as distributaries.
• Doab: It is made up of two words – ‘do’  meaning ‘two’ and ‘ab’ meaning ‘water’. It refers to the area between two rivers.
• Punjab: It is made up of two words – ‘Punj’ meaning ‘five’ and ‘ab’ meaning ‘water’. The land made up by five rivers such as Jhelum, Chenab, Ravi, Beas and Satluj.
• Bhabar: A narrow belt covered with pebbles lying parallel to the slopes of the Shiwaliks.
• Terai: It is a wet, swampy and marshy region lying south of Bhabar.
• Bhangar: It is a part of the northern plain formed of older alluvium.
• Khadar: The newer, younger deposits of the flood plains.
• Kankar: The soil in the northern plain contains calcareous deposits which is locally known as Kankar.
• Barchans: Crescent-shaped dunes.
• Coral polyps: They are short-lived microscopic organisms and live in colonies.
• Atolls: They are circular or horse shoe-shaped coral reefs.