Landforms of the Earth

  • A mountain is a natural elevation of the earth’s surface rising more or less abruptly from the surrounding level. Mountains are formed by the slow but gigantic movement of the earth’s crust.
  • Most of the mountain building takes place along the plate boundaries.
  • Based on the mode of formation, mountains are classified as Fold Mountains, block mountains, volcanic mountains, and dome mountains.
  • Fold Mountains are formed when two continental plates collide and their edge crumbles.
  • Different parts of the folds are anticline and syncline. Folds take much more complicated forms due to the complexity of the compression forces. Different types of folds are over folds, recumbent folds and over thrust fold.
  • Young Fold Mountains are formed during the last few million years ago and are still growing. Old Fold Mountains are formed hundreds of millions years ago.
  • Internal forces cause cracks or fissures on surface, forming blocks of earth's crust. These blocks are displaced vertically creating block mountains. In a block mountain, the uplifted blocks are called horsts and the lowered blocks are called graben.
  • The stressed earth’s crust tends to break and form faults. Different types of faults are reverse faults, normal fault and tear faults.
  • Rift valleys are elongated, deep valley with two high blocks at the sides. They are caused by compression or tension.
  • Volcanic mountains are formed due to years of accumulation of magma in successive layers during volcanic eruptions.
  • Dome Mountains are formed when magma pushes the curst up but harden before erupting into the surface.
  • Plateaus are table lands. Plateaus have steep slides and flat tops.
  • A large section of the earth’s crust is uplifted due to vertical movements.
  • Uplifted portions form plateaus and the depressed sections are called basins.
  • Undersea mountains are mountains, under the sea. Underwater mountain built from volcanic lava.
  • Mountains have a lot of relevance and importance. Mountains are important because they provide building material. They are source of fuel and chemicals, minerals and precious stones, forest and agricultural products, and hydro-electric power. They also have Influence on climate and facilitate tourism.

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  • Q1

    The major orogenic period that is the Alpine period took place of about -

    Marks:1
    Answer:

    30 million years ago

    Explanation:

    An orogeny is an event that leads to a large structural deformation of the Earth's lithosphere (crust and uppermost mantle) due to the interaction between tectonic plates.

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  • Q2

    Name the mountains that were formed during the Hercynian period.

    Marks:1
    Answer:

    The Ural Mountains

    Explanation:

    The Ural Mountains formed about 300 million years ago, near the end of the Carboniferous period, when the first reptiles were evolving. This was when the tectonic plates began to form the supercontinent of Pangaea. Variscan orogenic belt, also called Hercynian orogenic belt, series of mountain ranges that developed during a span of time extending from 370 million to 290 million years ago.

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  • Q3

    Name the period when the mountains of Scotland and Scandinavia were raised about 350 million years ago.

    Marks:1
    Answer:

    Caledonian period

    Explanation:

    The Caledonian orogeny was a mountain building era recorded in the northern parts of Ireland and Britain, the Scandinavian Mountains, Svalbard, eastern Greenland and parts of north-central Europe.

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  • Q4

    The meaning of ‘orogeny’ is

    Marks:1
    Answer:

    mountain formation.

    Explanation:

    An orogeny is an event that leads to a large structural deformation of the Earth's lithosphere (crust and uppermost mantle) due to the interaction between tectonic plates.

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  • Q5

    The systematic study of the Earth’s relief features is called

    Marks:1
    Answer:

    Geomorphology

    Explanation:

    Geomorphology is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or near the Earth's surface.

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