Major Landforms of the Earth: Mountains and Plateaus << Learner Hobby

RELIEF
    The relief of India has been shaped by both internal and external forces operating in the earth. It is often on account of variations and inequalities in shapes and forms of mountains, basis of altitudes.
LANDFORM PROCESSES
    The relief on the surface of the earth is shaped by internal and external processes described earlier.
    The internal processes lead to uplifting and sinking of the Earth's surface at plate margins. The process leads to earthquakes and volcanoes. The ground on which we stand is constantly on the move.
    The external processes wear down and rebuild the land surface. Weathering and erosion work on landforms over a long period of time to bring about a noticeable change. Weathering causes rocks to crack, crumble or degrade, which they do due to chemical, physical or biological interactions. The agents of erosion loosen and carry away rock debris formed by weathering. Rivers, winds, glaciers and moisture are the most powerful agents of weathering and erosion. The rebuilding process takes place through deposition by these very agents.
    It may be mentioned that internal processes rebuilding the uneven surface of the earth whereas external processes result in levelling off.
WEATHERING
    The disintegration of rocks on account of atmospheric and other processes is known as weathering. It is of three types - physical, chemical and biological. For example, water flowing in rivers strikes against rocks on the bed and banks of rivers. It shatters the rock and causes its physical break up also known as mechanical weathering. IT is not pure water itself by sediments in the river that cause this action. Similarly, winds blow up sand and other particles, when they strike against the rocks. They produce cracks leading to disintegration.
EFFECT
Weathering as already stated is on account of weather, as such its effects on rocks can be of many types depending on the type of rock. It is best depicted by pictures below:


                                     
                                                                                                 MOUNTAINS

ELEVATION
    A mountain is any natural elevation on the surface of the earth. The rise of the elevation in proportion to its base differs from region to region and place to place on the earth. Therefore, a uniform classification with respect to elevation of a hill differs from a mountain and so does plateau. A hill (610 m) is lower than a mountain (8000 m) but higher than plateau. Mountains like Himalayas and Andes are arranged in rows and hence are called Ranges.
TYPES
    Based on the mode of formation, mountains are generally classified into three types-fold, block and volcanic. The fold mountains are subdivided into young fold and old fold mountains.  Mountains like the Himalayas which are still rising are called 'Young Fold Mountains'. They were formed when the Earth's crust folded because of its internal movements. This convergence took place millions of years ago and is still continuing. As a result Himalayas is still rising.
    Old mountain ranges like the Aravallis of India, and Urals of Russia are low in height and have rounded peaks. They are termed as old fold mountains because the process of mountain building has stopped and external processes have taken place.
BLOCK AND VOLCANIC

    Block mountains are created when large areas of the Earth are fractured into huge blocks and displaced. The uplifted blocks are called Horsts and the lowered blocks are called Grabens.
    The Rhine valley and Vosges in Europe are examples of block mountains. In  these valleys like in the case of fold mountain range many rivers flow.
    The volcanic mountains are made by the solidification of lava on the surface of the Earth. After sometime, layers are accumulated to give rise to mountains Mountains such as Kilimanjaro in Africa and Fujiyama in Japan are volcanic mountains.
MOUNTAINS ON SEAFLOOR
   Mountains are also found under the oceans. Andaman and Nicobar Islands are actually summits of mountains in the sea. Mauna Kea in the Pacific Ocean is an under-sea mountain. It is 1000m beneath the ocean's surface.
                                                                                                     PLATEAUS

DIFFERENT ELEVATION
    Plateau is an elevated flat land. It is also called Tableland because it is flat-topped, have one or more sides with steep slopes. The elevation may differ according to general elevation may differ according to general elevation of the land. In the American continent, an elevation of 6000 m above sea level may be termed as a mountain. But in Asia some plateaus are even above this height generally the plateaus are made by internal processes alongside mountains. Some plateaus are even made by solidfication of lava or by external processes.
TYPES
    Based on the mode of formation, Plateaus are of different types like Basalt Plateau and Plateau Gravel. However two types of plateaus need to be distinguished as given below:
    Piedmont:  A plateau at the foot of a mountain is termed as a piedmont plateau. Plateaus are generally found near the mountain but some may even exist separately e.g. in the American continent and N.W. Italy.
    Intermontane: Intermontane refers to any features lying between two mountain or mountain ranges. The Plateau of Tibet, north of Himalayas, is the fine example intermontane plateau. It is known as the 'Roof of the World'. There are also similar plateaus between the east and west ranges of Andes mountains.
STOREHOUSE OF MINERALS
    Plateaus are the richest mining areas. Plateaus also have fertile soils. Examples include the Chhotanagpur Plateau in India and the African Plateau, which is famous for gold and diamond deposits. Waterfalls are also found in plateau areas.
    In the Chhotanagpur Plateau, Hundru falls on river Subernarekha adds to the exquisite beauty of the region.
    Jog falls in Karnataka is the highest waterfall in India. All these are a part of a whole tableland known as the Deccan Plateau.
RIVER VALLEYS
    India has many large rivers. The northern rivers originate from glaciers in the Himalayas and flow throughout the year. The rivers of South India depend on rainfall and flow during parts of the year. All the rivers usually have their mouth near the sea and make beautiful valleys in the upper course.