Topic– Important Geophysical phenomena such as earthquakes, Tsunami, Volcanic activity,
1) Why are the world’s fold mountain systems located along the margins of continents? Bring out the association between the global distribution of Fold Mountains and the earthquakes and volcanoes.(250 words)
Key demand of the question
The question is quite straightforward in its demand. In the second part of the answer we have to separately bring out the relation between the global distribution of fold mountains and volcanoes and earthquakes with examples.
Structure of the answer
Introduction – Explain what fold mountains are. You can draw a diagram to show how they are formed.
- Explain why fold mountains are formed at the margins of continents – fold mountains are formed from the folding of crust and uprising of the sediments accumulated by rivers along the margins of the continents by the collision of two continental plates or a continental plate and an oceanic plate. An example of fold mountains formed by converging of two continental plates are Himalayas mountains and fold mountains formed by convergence of a continental plate and an oceanic plate are Andes mountains, Appalachians mountains etc.
- Explain the relation between fold mountains and Earthquakes – with the passage of long time the folding continues and crust becomes over folded and strata(layers) of rock develop. It is called Over-thrust fold. Now, further folding leads to fracture in rock called Nappe. Upper layer of rock slides over lower layer leading to release of tremendous amount of energy which causes Earthquakes.
- Explain the relation between fold mountains and volcanoes – As two plates converge, the denser plate subducts under the lighter plate. This subducted plate enters onto the Mantle region of earth which causes melting of rocks to form Magma. Due to high pressure underneath this magma comes out from the up-lying continental plate in the form of Lava, causing the formation of volcanoes at some distance from continental margins.
Conclusion – Give examples.