With reference to the theory of plate tectonics, explain the origin of fold mountains. (10 marks)

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With reference to the theory of plate tectonics, explain the origin of fold mountains. (10 marks)

Approach:

  • Introduce with brief explanation of plate tectonics theory and how it forms the basis for explaining formation of fold mountains
  • Explain the origin of fold mountaints through plate convergence as per the plate tectonics theory – both continental-oceanic and continental-continental
  • Conclude how theory explains more than just formation of fold mountains
Model Answer :

The theory of plate tectonics identifies 7 major and 20 minor types of lithospheric plates. These plates are continuously in motion with respect to each other. Continents are part of a plate and what moves is the plate. Tectonically plate margins or plate boundaries are most important as all tectonic activities occur along the plate margins. The plate tectonic theory provides the basis for the explanation of the origin and growth of the young fold mountain.

 

Origin of fold mountains:

Continental- Oceanic Plate Convergence:  On convergence, the heavier plate, usually the oceanic plate subsides under the lighter continental plate. This zone of subduction is called benioff zone. This subduction of heavy plate under the lighter plate cause tremendous compressional force. This compressional force compresses the sedimentary material and pushes them upwards. Thus Fold Mountains are formed. Ex: The Andes and Rockies are formed by convergence of the Pacific plate with the south American and north American plates respectively.

Continental- Continental plate convergence yet again the denser plate amongst the two subsides and in the process exerts high compressional force on the other continental plate. In case of such interaction fold mountain are formed on both plates – the denser plate which subducts and well as the lighter plate. The subductedplate melts under tremendous heat and the voluminous expansion in form of magma tend to push the new formed fold mountain upwards ex: Himalayas formed due to convergence of Indian plate and the Eurassian plate.

Theory of  Plate Tectonics is a comprehensive theory which explains many other phenomenon like Mountain building, Folding and Faulting, Continental Drift, Vulcanicity, Seismic events  (earthquakes)  etc. It thus throws light on the genesis of various landforms.

Subjects : Geography – Physical