Fold Mountains are the mountains formed from the folding of the earth’s crust. These movements are caused due to various factors like movements in the mantle, expansion and contraction of some parts of the Earth. They are formed when two tectonic plates move towards each other leading to the folding of the layers of the Earth. The up folds are called anticlines and the down folds are called synclines.
- The Himalayas in Asia, the Andes Mountains in South America and the Alps Mountains in Europe are some examples of Fold Mountains.
- Orogenesis is the process of building new mountain ranges by the convergence of tectonic plates.
- 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.
Types of folds
- In geology, it is an area of ground where layers of rock in the earth’s surface have been folded into an arch.
- A typical anticline is convex up, with the hinge or crest being the point of greatest curvature, and the limbs being the sides of the fold that dip away from the hinge.
- A syncline is a fold with younger layers closer to the structure’s center.
- It is a downward fold; however, synclines that point upwards, or perched, can be found when strata have been overturned and folded (an antiformal syncline).
A monocline (or, less commonly, a mono form) is a step-like fold in rock strata that consists of a zone of steeper dip within an otherwise horizontal or gently dipping sequence.
- A symmetrical fold is one in which the axial plane is vertical.
- In a symmetrical fold both the limbs are equal and inclined at the same angle.
- An asymmetrical fold is one where one limb in an old structure is steeper than the other.
- An asymmetrical fold is one in which the axial plane is inclined.
- An overturned fold is formed when one limb occupies the normal position, while the other bends more than 90 degrees.
- An overturned fold has a highly inclined axial plane such that the strata on one limb are overturned.
- An isocline fold results from the continued lateral compression upon an overturned fold and crowing it upon the adjacent overfold. Here both the limbs dip at equal angles in the same direction.
- An isoclinal fold has limbs that are essentially parallel to each other and thus approximately parallel to the axial plane.
- A recumbent fold is literally a fold lying down, resulting from the continuation of pressure. The axial plane and both limbs of a fold lie roughly and horizontally.
- A recumbent fold has an essentially horizontal axial plane.
- Nappe results when the pressure exerted upon a recumbent fold is sufficiently great to cause it to be torn at its roots and to be thrust forward.
- Nappes are large-scale recumbent folds formed by predominantly ductile deformation.
Types Of Folds
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