The process of folding formed the Atlas Mountains. They are called Fold Mountains. Their formation is explained in two ways: -

The compressional forces acted on the young and soft Sedimentary rocks which folded. The soft parts are forced to go down forming lowlands called synclines. However, the hard rocks are raised up forming Uplands called Anticlines.

A part from the tension and compressional forces, Fold mountains were also formed by the process of the Geosyncline.

Anticlines are formations that have folded rocks upward.

The process of folding formed the Atlas Mountains. They are called Fold Mountains. Their formation is explained in two ways: -
The compressional forces acted on the young and soft Sedimentary rocks which folded. The soft parts are forced to go down forming lowlands called synclines. However, the hard rocks are raised up forming Uplands called Anticlines.

A part from the tension and compressional forces, Fold mountains were also formed by the process of the Geosyncline.

Geo-syncline theory.

The second theory, which explains the formation of Fold Mountains, is known as the geo-syncline theory. It says that there was a pre-existing huge and extensive water filled depression known as the geo-syncline.

This depression was gradually filled in by wind and water borne deposits of eroded rock materials. Moving ice also deposited some materials to the geosyncline. The geo-syncline and sea creatures died and their bodies sunk to the ocean floor.

After many years the increased weight of these deposits helped to deepen the geo-syncline towards the centre. And this caused the continental plates to move towards each other; the pressure on the sedimentary rocks increased and they slowly crumpled up, folded and raised up of the water high into the atmosphere forming fold mountains.

This theory suggests the Alps Mountains of Europe were formed at the same time. Also what makes us believe that this happened is the existence of sedimentary rocks on the affected mountains. Sedimentary rocks are sediments deposited in lowland areas but not on mountain tops.

However, this is the most acceptable theory that explains the formation of fold mountains world wide.

Diagram showing formation of fold mountains by Geosyncline process