Mountains come under the second order of relief features. This is a portion of land surface rising considerably above the surrounding country, either as a single eminence or in a range or chain.
Types of Mountains
Folded Mountains (Geosynclines)
- Most of the Fold Mountains are the youngest mountains in the world.
- The main examples are the Himalayas, the Alps, Rockies, and the Andes.
- The fold mountains are formed by compression when two horizontal forces act towards a common point that compresses the intervening rock strata to produce fold mountains.
- The fold consists of two inclined parts called limbs, the upper portion is called anticlines, while the lower portion is called synclines. On the basis of the period of origin folded mountains are divided into:
(i) Old Folded Mountains: All the folded mountains originating before the tertiary period come under the category of old folded mountains, e.g., the old folded mountains of Calledonian and Hercynian periods, such as the Aravalis, Appalachians etc.
(ii) New Folded Mountains: In this category come the Alpine folded moun-tains of the tertiary period, e.g. the Alps, Himalayas, Rockies, Andes etc.
- These are gigantic mountains characterised by glacier-capped high peaks, intense erosion, complex folding and faulting, volcanism etc.
Volcanic mountains are formed by the extrusion of lavas and pyroclastic materials, which, if continued long enough, produces gigantic volcanic piles.
- The Kilimanjaro (Africa), Cotapaxi (Andes), Mount Acancagua (the highest volcanic mountain) etc., are some of examples.
These are the result of faulting caused by tensile and compressive forces.
- Examples are Vosges and Black forest mountains bordering the Rhine Rift Valley, Salt Range of Pakistan, Siera Nevada (USA) etc.
- Siera Neveda mountain of California is considered to be the most extensive block mountain of the world.
When mountains, plateau, or high plains take the form of mountains by continued erosion over a long period of time they are known as Relict mountains.
- Examples are Aravali, Satpura, Vindhyachal in India, mountains of Scot-land and Penine range of Europe.