Folding

The process in which rocks are bent and crumpled due to

compressional forces which form upfolds or ANTICLINES and the

downfold or SYNCLINE

FOLDING PROCESS PRODUCE

FOLD MOUNTAIN

S

Fold mountains are mountains formed by powerful compressional forces in the crust.

These forces cause bending of the rock strata

The anticline/uplifted crust, forms FOLD MOUNTAINS

The young fold mountains are found in three main belts:

1. Along the whole of west coast of North and South America.

2. Stretches from parts of the Mediterranean and South Europe along with the Northern tip of Africa to parts of the middle east, the Himalayas and Bangladesh, and also further down to parts of SEA like Myanmar, Thailand, Malaysia and Indonesia and ending south in New Zealand

3. Stretches from Eastern Russia and Korea to Japan and Northeast China

Why in this region? [2 REASONS]•These areas are found mainly along the boundaries of plates moving towards each other.•Here, great compressional forces causes massive folding of rocks forming the young fold mountains.

EXAMPLE: THE

HIMALAYAS, THE ROCKIES,

THE ANDESTHE ALPS

WHY?

STAGE 1 STAGE 2 STAGE 3 STAGE 4 STAGE 5SYMMETRICAL

FOLDASYMMETRIC

AL FOLDOVERFOLD RECUMBENT

FOLDOVERTHRUST

FOLD

•Both limbs are equal in steepness•Compression from both opposite sides is equal

•One limb is steeper•Compression is greater from one side than the other side

•One fold is pushed over the other limb due to increasing compression

•Limbs are nearly parallel to each other

•One limb is pushed forward•Fracture occurs along the fault plane•This limb overrides the other•It may become detached from the main fold and is then called a nappe

Symmetrical foldASYMMETRICAL

FOLD

OVERFOLD

RECUMBENT FOLD

OVERTHRUST