Fold (geology)
Folding is one of the endogenetic processes.
When two forces act towards each other from opposite sides, the rock layers will be bent into "folds". The process by which folds are formed due to compressional force is known as folding.
There are large-scale and small-scale folds. Large-scale folds are found mainly along destructive plate boundaries.
Structure of a fold.
The upfold is called an anticline. The downfold is called a syncline.
The imaginary line joining the highest points along the upfold is called the crest line.
The flanks of a fold are known as the limbs.
The central line from which the rock strata dip away in opposing directions is called the axis of fold.
According to the degree of folding of the layers, folds can be classified into five main types.
Formation of a fold mountain.
Large depressions called geosynclines form between plates. Seas filled the geosynclines and rivers flowing into them carried sediments (sand and silt) which build up on the sea bed.
Over millions of years the sediments were compressed, by their own weight, into sedimentary rocks, e.g. sandstone, limestone etc.
Landforms formed by folding.
Large-scale folding will develop parallel ranges of round-top mountains along destructive plate boundaries. These mountains are known as fold mountains.
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