Consider the following information:

In how many of the above rows is the given information correctly matched?

1. Only one
2. Only two
3. Only three
4. All four

Explanation

Row 1 is incorrect

• Block mountains are created because of faulting on a large scale (when large areas or blocks of earth are broken and displaced vertically or horizontally). The uplifted blocks are termed horsts, and the lowered blocks are called graben. The Great African Rift Valley (valley floor is a graben), the Rhine Valley (graben) and the Vosges mountain (in France) (horst) in Europe are examples.

Row 3 is correct

• Fold mountains are formed when sedimentary rock strata in geosynclines are subjected to compressive forces. They are the loftiest mountains, and they are generally concentrated along continental margins.
  • Geosyncline: a large-scale depression in the Earth’s crust containing very thick deposits. E.g. Tethys geosyncline
• Classification of Fold Mountains:
  • On the Basis of Period of Origin
    • Very Old Fold Mountains: Very old fold mountains are more than 500 million years old. They have rounded features and are of low elevation (due to denudation). E.g. Appalachians in North America and the Ural Mountains in Russia.
    • Old Fold Mountains: The fold mountain systems belonging to the Caledonian and Hercynian mountain-building periods (earlier than 66 million years ago) that occurred before the Tertiary Period falls in this category. Old fold mountains are also called thickening relict fold mountains because of their lightly rounded features and medium elevation. Top layers are worn out due to erosional activity. Example: Aravalli Range (India’s oldest fold mountain system. The range rose in the post-Precambrian event called the Aravalli-Delhi orogeny).

Row 2 is incorrect, and Row 4 is correct

• Alpine or Young Fold Mountains: Alpine fold mountains, belonging to the Tertiary period (66 million years ago to present), can be grouped under the new fold mountains category, as they originated during this period. Examples include the Rockies, the Andes, the Alps, and the Himalayas. They are characterised by rugged relief, imposing height and highly conical peaks

Answer: (b) Only two; Difficulty Level: Easy