Important Questions (1 mark): Physical Features Of India - Class 9

The soil is one of the important components of the sustainability of an ecosystem because it is the vitally important natural medium for the growth of vegetation. It can be defined as, the upper layer of earth in which plants grow, a black or dark brown material typically consisting of a mixture of organic remains, clay, and rock particles.  Here, we are giving brief note on the major factors which are responsible for the formation of the Soil.

India's relief features are meant to be as the natural features of India. Geological formation, weathering, erosion & deposition are the natural phenomena which are causes of creation & modification of natural features. but population density is a sort of which is caused by humans.humans or human made resources can never create / modify the natural features like mountains, rivers,valleys etc naturally

A plausible theory presented by earth scientists to explain the formation of continents and ocean basins and the various land forms is the ‘Theory of Plate Tectonics’. According to the theory, the crust of the earth has been formed out of seven major and some minor tectonic plates.

According to the earth scientists, millions of years ago, the world comprised of a supercontinent ‘Pangaea’ surrounded by the primeval ocean ‘Panthalasa’. The present continents and intervening oceans were formed due to splitting of the crust into plates due to convection currents and drifting of these plates.

The lithosphere, which is the rigid outermost shell of a planet (the crust and upper mantle), is broken into tectonic plates. The Earth's lithosphere is composed of seven or eight major plates (depending on how they are defined) and many minor plates.

Glaciation- It is the process of being counted by glaciers or ice sheets. 
Whereas faulting , folding and volcanic activity occur due to movement in tectonic plates. 

If two tectonic plates collide, they form a convergent plate boundary. Usually, one of the converging plates will move beneath the other, which is known as subduction. Deep trenches are often formed where tectonic plates are being subducted and earthquakes are common. As the sinking plate moves deeper into the mantle, fluids are released from the rock causing the overlying mantle to partially melt. The new magma (molten rock) rises and may erupt violently to form volcanoes, often building arcs of islands along the convergent boundary. These island arcs are always landward of the neighboring trenches.

According to the theory of plate tectonics, the earth’s lithosphere is broken into distinct plates which are floating on a ductile layer called asthenosphere (upper mantle). Plates move horizontally over the asthenosphere as rigid units.

The lithosphere includes the crust and top mantle with its thickness range varying between 5-100 km in oceanic parts and about 200 km in the continental areas.

The oceanic plates contain mainly the Simatic crust and are relatively thinner, while the continental plates contain Sialic material and are relatively thicker.

Lithospheric plates (sometimes called crustal plates, tectonic plates) vary from minor plates to major plates, continental plates (Arabian plate) to oceanic plates (Pacific plate), sometime a combination of both continental and oceanic plates (Indo-Australian plate).

The movement of these crustal plates causes the formation of various landforms and is the principal cause of all earth movements.

These extend from the east of the Bhutan Himalayas upto the Diphu pass in the east. The general direction of the mountain range is from southwest to northeast. Some of the important mountain peaks of the region are Kangtu and Namcha Barwa. These rangers are dissected by fast-flowing rivers from the north to the south, forming deep gorges. Brahmaputra flows through a deep gorge after crossing Namcha Barwa. Some of the important rivers are the Kameng, the Subansiri, the Dihang and the Lohit. These are perennial with the high rate of fall, thus, having the highest hydro-electric power potential in the country. An important aspect of the Arunachal Himalayas is the numerous ethnic tribal community inhabiting in these areas.

The theory of plate tectonics states that there are a large number of plates under the earth’s crust which are in continuous motion.

This theory is widely acclaimed and accepted by people worldwide. 

When these plate overlap, we have an earthquake. 

The movement of these tectonic plates cannot be predicted in advance.

It is believed that millions of years ago, India was the part of a big continent, known as the Gondwana land. The Peninsular part of the Gondwana land was the oldest landmass. The Gondwana land included India, Australia, south Africa, South America and Antartica as one single landmass. The convectional currents split the crust into a number of pieces, thus leading to the drifting of the Indo-Australian plate after being separated from the Gondwana land, towards north. 

Lakshadweep, in the Arabian Sea, is a part of the Indian subcontinent and is recognised as the smallest union territory of India. Lakshadweep means "hundred thousand islands" in Malayalam and Sanskrit. True to its name, these islands are very picturesque and provide a true vacation for those who love beaches, water sports and sea food.The whole of Lakshadweep is nothing but a set of small islands situated near each other. It comprises a total of twelve coral atolls, five banks, three coral reefs, and several islets. The location is near the Kerala coast and falls under the jurisdiction of Kerala state and Kerala High Court. Kavaratti is its capital and it is considered one of the most beautiful places in the Indian subcontinent.

Greater Himalayas or Himadri or Himagiri comprises all major mountain ranges of the Himalayas. Greater Himalayas is also known as “Mahaan Himalaya”in Hindi.

Among the four parallel ranges of the Himalayas, the Greater Himalaya appears highest, largest and longest. The Main Central Thrust divides the Greater Himalayas and the Lower Himalayas.

The famous mountain peaks like Mt. Everest (8,852 m) (Sagarmatha of Nepal and Chomolangma of China), the highest peak of the world, Nanga Parbat (8,126 m) of India, the ninth highest peak of the world, Kanchenjungha (8,598 ) of Nepal and India, the third highest peak of the world, and the Zaskar Range stands in the Greater Himalayan Mountain belt.

The average height of the Greater Himalaya belt is 6000 m.

Landslides happen when gravity overcomes the natural cohesion of a slope—the slope becomes too steep, the material becomes weak, or (usually) a combination of both.

The Brahmaputra River marks the eastern boundary of the Himalayas. Beyond the Dihang gorge, the Himalayas bend sharply towards south and form the Eastern hills or The Purvachal.
Following are the characteristics of Purvachal:
(a) These hills run through the north eastern states of India.
(b) They are mostly composed of sandstones (i.e. Sedimentary rocks).
(c) These hills are covered with dense forest.
(d) These hills are composed of the Patkai Hills, Naga Hills, Manipuri Hills and Mizo Hills.

The most distinct features of the peninsular plateau is the black soil area known as Deccan Trap. The soil is of volcanic origin. The rocks in this region have denuded over a long time and are responsible for the formation of black soil.

The convectional currents split the crust into a number of pieces, thus leading to the drifting of the Indo-Australian plate after being separated from the Gondwana land, towards north. The northward drift resulted in the collision of the plate with the much larger Eurasian Plate. Due to this collision, the sedimentary rocks which were accumulated in the geosyncline known as the Tethys were folded to form the mountain system of western Asia and Himalaya.

Purvachal (Eastern Highlands) are mountain ranges in eastern India. They extend over 37,900 square miles (98,000 square km) in Arunachal Pradesh, Nagaland, Manipur, Mizoram, Tripura, and eastern Assam states.

The Peninsular plateau is flanked by stretch of narrow coastal strips, running along the Arabian Sea on the west and the Bay of Bengal on the east. 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 (Mumbai – Goa), the central stretch is called the Kannad Plain while the southern stretch is referred to as the Malabar coast.

Indira Point is the name of the southernmost point of Republic of India. It is situated on Great Nicobar Island in the Nicobar Islands, which are located in the eastern Indian Ocean at 6°45'10″N and 93°49'36″E. This is not on the Indian mainland, but within the Union Territory of Andaman and Nicobar Islands.

The three types of plate movement are divergent, convergent and transform plate boundaries. Divergent occurs when two tectonic plates move away from the other. A convergent boundary is when two plates collide. A transform plate boundary occurs when two plates slide past each other.

The peninsular plateau was one of the parts of the gondwana landmass which drifted away.Hence,  it is the oldest landmass of the indian subcontinent.

The Greater Himalaya is the northernmost range and is also known as Himadri. Its average height is more than 6000 metres above the sea level. 

This is the highest and the most continuous mountain range in the world. This range ends abruptly in Nanga Parbat in the northwest and in the Namcha Barwa in the northeast. Snow-capped peaks over 8000 metres above the sea level are found in this range.

The Lesser Himalayas or Himachal: The altitude of this range lies between 1000 and 4500 metres and the average width is 50 KM. The Prominent ranges in this are Pir Panjal, Dhaula Dhar and Mahabharata ranges.

It compresses of many famous hill stations like Shimla, Dalhousie Darjeeling, Chakrata, Mussoorie, Nanital etc. It also comprises of famous valleys like Kashmir, Kullu, Kangra etc.

The Kali and Tista rivers divide the Nepal Himalayas and the part lying between Tista and Dihang rivers is known as Assam Himalayas. Therfore, the correct answer is C.

Northern plain is formed of alluvial soil. The deposition of alluvial soil in a vast basin lying at the foothills of himalaya over millions of years formed this fertile plain.

Northern Plain area is about 7 lakh square km.

Northern Plain has length of 2400 km and breadth of 240 km to 320 km.

Terai plain: South of Bhabar, the streams and rivers re-emerge and create a wet, swampy and marshy region known as terai. This was a thickly forested region full of wildlife. The forests have been cleared to create agricultural land and to settle migrants from Pakistan after partition.

The peninsular plateau is a table land composed of the old crystalline, igneous and metamorphic rocks. It was formed due to breaking and drifting of the Gondwana land and thus making it a part of oldest landmass. This plateau has broad and shallow valleys and rounded hills. The peninsular plateau consists of broad divisions, namely, the central highlands and the Deccan plateau.  

The Central Highlands: The Central Highlands lies to the north of the Narmada river. It covers the major portion of the Malwa plateau. The rivers in this region flow from southwest to northeast; which indicates the slope of this region. It is wider in the west and narrower in the east. Bundelkhand and Baghelkhand mark the eastward extension of this plateau. The plateau further extends eastwards into the Chhotanagpur plateau.   

Around 200 million years ago (also known as the Middle Permian Period) , an extensive sea stretched along the latitudinal area presently occupied by the Himalayas. This sea was named the Tethys. Around this period, the super continent Pangea began to gradually split into different land masses and move apart in different directions.

Lakshadweep islands have coral origin.They are a type of coral reefs which are known as Atolls that is circular or Horse shoe shaped reefs.This can be seen by looking at India map. Lakshadweep islands are somewhat horse shoe shaped.