Geography; Mountains, Plateaus, Plains and Islands

  • Various landforms are mountains, hills, plateaus and plains.
  • Mountains. (based on their mode of formation) –
    • Fold mountains.
      • Formed due to the compressive forces generated by endogenetic forces. (Earthquake, landslide etc.)
      • On the basis of age fold mountains are –
        • Young / New fold mountains.
          • Formed after continental drift.
          • Example: Himalayas, Alps, Andes, Rockies, Atlas etc.
        • Old mountains.
          • Are of pre-drift era, and then subjected to denudation and uplift.
          • Example: Pennines (Europe), Appalachians (USA), Aravallis (India) etc.
    • Block mountains.
      • Huge blocks raised or lowered.
      • Raised part is known as horsts and lowered part rift valley / Graben.
      • Example: Narmada, Tapi and Damodar valley, the Vosges in France and Black forest in Germany (Rhine river flows).
    • Volcanic mountains / Mountains of accumulation.
      • Example: Mount Fiji (Japan), Cotopaxi (Andes), Vesuvius and Etna (Italy), Mount Mayon (Philippines) etc.
    • Residual or Dissected mountains.
      • Result of erosion of plateaus and high planes.
      • Example: Girnar and Rajmahal (India), Catskill (New York), Sierras (Spain) etc.
  • Plateaus (relief of more than 500 ft). According to their mode of formation and their physical appearance –
    • Tectonic plateau.
      • Formed by the earth’s movement which causes uplift and are normally of a considerable size and fairly uniform altitude.
      • Plateau which is enclosed by Fold Mountains is known as intermount plateau.
      • Example: Tibetan plateau (Himalayas), Kunlun and Bolivian plateau.
    • Volcanic plateau.
      • Formed by the accumulation of lava.
      • Example: Deccan plateau of India.
    • Dissected plateau.
      • Formed by the continuous process of weathering and erosion.
      • High extensive plateau are gradually worn out and there surface made irregular.
      • Example: Scottish highlands.
  • Plains –
    • Low lying and flat land surface with least difference between its highest and lowest point.
    • Types of plains.
      • Structural plains.
        • Example: great Plains of USA.
      • Erosion plains.
        • Example: Plains of north Canada.
      • Depositional plains.
        • Indo- Ganga plain.
  • Islands –
    • A grouping of geographically or geologically related islands is called an archipelago.
    • According to the way they are formed they are classified as.
      • Continental Island.
        • Rests on the continental shelf.
        • Water level around is very shallow, typically less than 600 ft.
        • Example: Canadian island, Green land, Great Britain etc.
      • Volcanic Island.
        • When volcanoes deep in the ocean rises, forms a volcanic island.
      • Coral Island.
        • Forms a ring and partially or totally encloses a shallow body of water or lagoon.
        • Have large collection of coral at top rock (usually volcanic) in the ocean.
        • Example: Lakshadweep.
      • Alluvial Island.
        • Are formed by the outward flow of water depositing silt and gravel at the mouth of the river.
        • Example: New Moore Island (West Bengal).
      • Barrier Island.
        • Formed by the waves depositing sand on the shallow ocean bottom as they crash on the shoreline.
      • Tectonic Island.
        • Long island arcs (archipelago) are formed.
        • Example: Indonesia, Philippines, Japan etc.
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