Land-forms resulting from folding
Several landforms are formed during the folding process including:
- Nappe fold
- Fold mountains
- 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“
- 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“
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.
- Occurs when one fold is pushed over the adjoining limb due to increasing compressional forces.
- They are also known as overturned folds.
- 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.
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.
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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