LANDFORMS OF THE EARTH STD VIII

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Nathaniel Ross
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LANDFORMS OF THE EARTH STD VIII 1) What do you understand by the term geomorphology? A) Geomorphology is the systematic study of the Earth s relief features.

1 LANDFORMS OF THE EARTH STD VIII 1) What do you understand by the term geomorphology? A) Geomorphology is the systematic study of the Earth s relief features. Geo means earth; morph meaning form and ology is science. 2) What are referred to as orogenic movements? A) The word Orogeny has been derived from the Greek word 'Oros' meaning Mountain. The orogenic movements are due to the horizontal forces in the earth s crust that lead to the formation of mountains. 3) Name some of the mountain building periods of the recent times. A) The three most recent orogenics are the: Caledonian Period: It occurred about 320 million years ago. It raised the mountains of Scotland and Scandinavia. Hercynian Period: It occurred about 240 million years ago. It was characterized by ranges such as the Ural Mountains, The Penines and the Welsh Highlands of Britain, the Harz Mountains in Germany and the Appalachians of America. Alpine Period: It took place about 30 million years ago. Being the most recent, these young fold mountains buckled up and were overthrust on a gigantic scale, making the loftiest and most imposing ranges. Their peaks are several thousand metres high. The most recently formed Fold Mountains consist of the Alps, Himalayas, Rockies and Andes and they are termed as Alpine system. 4) What do you understand by the term Fold Mountains? A) The term fold refers to the way in which these mountains were formed. They are formed due to horizontal movements, which cause the Earth s crust to wrinkle or shrink. The upfolds are called the anticlines and the downfolds formed the synclines. 1

2 5) Name and explain the formation of some of the Fold Mountains. A) Some of the examples of the Fold Mountains are: The Alps were formed as a result of the northward drift of the African continent towards the more stable blocks of Central Europe. The uplift of the Alps was accompanied by the trough in which the Mediterranean Sea is located. The Himalayas were formed when the Deccan Plateau was pushed towards the north and the depression of the Indo-Gangetic trough became narrower. Formation of Fold Mountains Formation of Block Mountains or Horsts 6) Name the world s highest and the second largest mountain ranges. A) The Himalayas are the world s highest and the largest mountains, stretching across mid-asia with 281 peaks. The world s second largest range is the Andes. 2

3 7) How are the Old Fold Mountains different from the young fold mountains? A) Old Fold Mountains Young Fold Mountains These have been formed about 250 These have formed in the most recent million years ago. mountain building phase, that is about These mountain ranges have a low altitude and have gentle slopes because they have been subjected to denudation for millions of years. 25 million years ago. They are some of the world s highest mountain ranges with rugged relief features because they have been subjected to denudation for a comparatively short period only. 8) Mention some of the features of the Young Fold Mountains. A) The following are the characteristics of the young fold mountains: They have series of parallel ranges with deep valleys between and high peaks covered with snow. They have intermontane plateaus in some places. As they are areas of crustal instability, they are liable to earthquakes and volcanic eruptions. They have several glaciers and attract tourists. 9) Account for the distribution of Fold Mountains in the world. A) The Fold Mountains are concentrated in two belts of the world: 1) Circum-Pacific Mountain Belt: It is found along the margins of the Pacific Ocean. These include the Andes ranges of South America, the Rockies of North America and the series of the island arcs off the coast of North America. 2) Mid-World Mountain Belt: These include the Alps and the associated ranges in Europe, the Caucasus and other ranges in Asian Russia, the mountain ranges in Turkey and Iran which converge on the Pamir knot. They are continued by the Himalayas and the associated ranges and merge with the mountain ranges in the Indonesian islands. 10) State the role of mountains. A) The Mountain ranges have the following significance: Mountains are effective climatic barriers that protect countries from bitterly cold winds, e.g. Himalayas. They have great economic significance, as swift flowing rivers can be harnessed for generating HEP, lumbering can be carried out as done in British Columbia and cattle rearing can be done as done in Switzerland and Scandinavia. 3

4 High mountain ranges are barriers to communication and thus crossing it was a great difficulty and could be done only by constructing tunnels. E.g. Alps. 11) How are Block Mountains and Rift Valleys formed? A) Block Mountains or Horsts are formed when tectonic plates move away causing the surface of the Earth to crack apart. These cracks cause faulting and may result in a mas of land being pushed up between parallel cracks to form a block or by sinking of land on either side of the block of higher land. 12) a) State the characteristics of Block Mountains or Horsts? A) These Mountain blocks are generally steep-sided and flat-topped. b) Provide a few examples of the same. A) The Black Forest and the Vosages of the Rhineland in Germany. The Vindhya and the Satpura ranges in India 13) a) How are Rift Valleys formed? A) When tensional forces cause the central portion to be let down between two adjacent fault blocks. Then a graben or a rift valley is formed. They have steep sides. b) Provide a few examples of Rift Valleys. A) The Rift Valley of Rhine lies between the Black forest and the Vosges Rifts. The Rift Valley of Narmada lies between Vindhya and the Satpura. 14) What are volcanic mountains? What are they also referred to as? A) These mountains are the result of the accumulation of volcanic material ejected from the fissures of the Earth s crust. They are also referred to as mountains of accumulation. 15) Provide a few examples of volcanic mountains. A) Most of the mountains in the Circum-Pacific belt, such as Fujiyama in Japan, Mt. Mayon in Philippines, Mt. Merapi in Sumatra, and Mt. Cotopaxi in Ecuador etc. 16) Name the various types of plateaus and provide a few examples for the same. A) The following are the various types of plateaus: Tectonic Plateau: These types of plateaus are formed due to Earth movements. For e.g. Meseta of Iberia. 4

Intermont Plateau: They are enclosed by Fold Mountains. They are usually very high, for e.g. the Tibetan Plateau lying between the Kunluns and the Himalayas.

5 Intermont Plateau: They are enclosed by Fold Mountains. They are usually very high, for e.g. the Tibetan Plateau lying between the Kunluns and the Himalayas. The Anatolian Plateau between the Pontic and Taurus mountains, the Plateau of Bolivia and Peru surrounded by the Great Andes Mountains. Volcanic Plateau: These are formed when successive sheets of lava solidify on it. For e.g. Columbia-Snake Plateau and the Deccan Plateau. Dissected Plateau: These plateaus, due to steam action, volcanic ejection of lava, corrosion by rivers and abrasion by winds, are dissected into steep sided tabular masses. For e.g. Brazilian Plateau and Colorado Plateau. 17) What do you understand by the term plain? A) A plain is comparatively level surface of land at low elevation from the sea, less than 150 m above the sea level. 18) Name and explain the various types of plains found on the surface of the Earth. A) Various types of plains are: Coastal plains: Western Coastal Plain Eastern Coastal Plains 5

6 These are found along the coastal areas. For e.g. The Great Plains of USA, the Eastern and the Western Coastal Plains of India. Loess Plains: These are formed by material brought by winds and deposited. For e.g. The Loess plains in China. Alluvial Plains: These are formed by deposits brought down and deposited by rivers. For e.g. the Indo-Gangetic Plains. ****************** 6

not to be republished NCERT MAJOR LANDFORMS OF THE EARTH

not to be republished NCERT MAJOR LANDFORMS OF THE EARTH 6 You must have seen some of the landform features as shown in the Figure 6.1 below. You will notice that the surface of the earth is not the same everywhere. The earth has an infinite variety of landforms.