Syllabus: General Studies Paper 1 (World Geography)
Explain the mechanism behind formation of Fold Mountains. Why they are mostly found along the margins of continents?
Fold Mountains are those which are formed as a result of the compression of tectonic plates, which leads to the formation of large fold-like structures on the earth’s crust. The Himalayas, Andes, and Alps are some of the active fold mountains.
Mechanism of formation:
- They are formed by large scale earth movements when stresses are set up in the earth’s crust.
- These stresses may be caused due to increased load of overlying rocks, flow movements in the mantle, magmatic intrusions into the crust or expansion/contraction of some part of the earth.
- When such stresses are initiated, rocks are subjected to compressive forces that produce wrinkling or folding along the lines of weakness.
- This folding creates a series of upfolded & downfolded waves called anticlines and synclines respectively.
- The complexity of compressional forces furthermore leads to different types of fold mountains being created.
- In simple folded mountains, folds are arranged in waves like pattern with a well-developed system of anticlines and synclines.
- While in complex folded mountains, folds are complex in nature due to extreme compressional forces like overfold, recumbent fold and nappe.
Reasons for presence of fold mountains along the margins of continents:
- Fold Mountains are commonly associated with continental crust. They are formed due to convergence between two continental plates or between an oceanic and a continental plate.
- This convergence happens at the convergent plate boundaries, also called as continental collision zones or compression zones.
- The convergence of two continental plates causes sediments between them to get squeezed and thrusted upward leading to the formation of fold mountains along the plate boundary.
- Similarly, when oceanic-continental convergence takes place, the denser oceanic plate submerges and continental plate is thrusted upward to form fold mountains along the continental plate margin.
- For this reason, most of the fold mountains are found on the edge or former edge of the continental plate boundaries, as shown in the map below.
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