Fold mountains

Fold mountains are formed by the effects of folding on layers within the upper part of the Earth's crust. Before the development of the theory of plate tectonics and before the internal architecture of thrust belts became well understood, the term was used to describe most mountain belts, e.g. the Himalayas. The term is still fairly common in the literature of physical geography but has otherwise fallen out of use.
Formation.
Fold mountains form when two tectonic plates move towards each other at convergent plate boundary. When plates and the continents riding on them collide, the accumulated layers of rock may crumple and fold like a tablecloth that is pushed across a table, particularly if there is a mechanically weak layer such as salt. The mountains such formed are usually more in length instead of breadth.