Land-forms resulting from folding

The fold mountains of the Cape are among the most prominent features of folding. Image via AfricanSky.

Land-forms resulting from folding

Several landforms are formed during the folding process including:

1. Anticlines
2. Nappe fold
3. Overthrust
4. Overfold
5. Recumbent
6. Fold mountains

1. Anticline

A diagram showing a syncline and an anticline. Image via Pinstopin

• An anticline is a fold that is arched upward to form a ridge or mountain.
• It can be defined simply as a highland area/ridge that is formed due to compressional forces.
• It is convex shaped.
• They are formed out of rock units that are folded in the same pattern.
• They are a result of a simple fold.
• Each side of a fold is called a limb.
• The topmost point is called a crest/axial line.
• The axial line acts as a line of symmetry between the two limbs.
• The shape of an anticline is like an inverted letter “U“

Real life anticline in Lebanon. Image via MediaWiki.

2. Syncline

• A syncline is a fold that arches downwards to form a fold.
• Are usually made up of rocks units that are folded in the same pattern.
• Are concave shaped.
• Usually occur in conjunction with anticlines as shown on the diagram below.
• An anticline is shaped like the letter “U“

A diagram showing the formation of anticlines and synclines. Image by Radford University.

3 Over thrust

• If compression forces continue to act on the rock layers a simple fold (from which anticlines and synclines are formed) progresses into an asymmetrical fold, then into an over fold and
• Finally into an over thrust fold.
• An over thrust is actually a fault.
• Older rock is exposed as it covers younger rocks.

4. Over-fold

• Occurs when one fold is pushed over the adjoining limb due to increasing compressional forces.
• They are also known as overturned folds.

An overfold. Image by StudyBlue.

5. Recumbent

• Occurs when the limbs are nearly parallel to each other and the axis of the fold is horizontal.
• The axis of the fold is horizontal.

A recumbent fold. Image by StudyBlue.

6. Fold Mountains.

• Are formed as a result of folding in the upper layers of the earth’s crust
• This is as a direct result of compression forces when tectonic plates move against each other from opposite directions i.e. forces acting against one another
• Acting on rocks that are not brittle but are flexible.
• These mountains are formed by orogenic forces.
• When the two plates collide the crumple and fold in a shape not unlike that of a table cloth.
• A lot of folded mountains are formed in narrow elongated seas called geosynclines.
• Fold mountains typically have a short width but have a longer length which may span several thousand kilometers.
• Examples of fold mountains include the Jura mountains, Himalayas, the Cape Range Mountains and the  Mt Everest in Nepal.

Two continental plates moving towards each other resulting in a trench and fold mountains. Image from Localwiki

Here a diagram showing an oceanic plate and a continental plate moving towards one another leading to the formation of fold mountains.

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