Introduction:

Fold Mountains are formed due to the folding of crustal rocks by compressive forces generated by endogenetic forces coming from within the earth. These are the highest and most extensive mountains in the world and are found on all the continents. The distributional patterns of the fold mountains over the globe denote the fact that they are generally found in a north-south direction or east-west direction. Rockies, Andes, Alps, Himalayas, Atlas, etc. are examples of Fold Mountain. Folded mountains are classified on various bases as follows:

(i) Fold Mountains are divided into 2 broad categories based on the nature of the folds. Simple Fold Mountains with Open Folds- Such fold mountains are characterized by well-developed systems of anticlines and synclines wherein folds are arranged d in wave-like patterns. These mountains have open and relatively simple folds. The complex folded mountain represents the very complex structure of tensely compressed folds. Such a complex structure of folds is called ‘nappe’.

(ii) Folded mountains are classified into Young folded mountains which are least affected by the denudation process and mature folded mountains. It may be pointed out that it is difficult to find true young folded mountains because the process of mountain building is exceedingly slow and thus denudation process starts denuding the mountains right from the beginning of their origin.

(iii) Based on the period of origin, folded mountains are divided into old-fold mountains and new-fold mountains. All the old folded mountains originated before the Tertiary period. These mountains have been greatly denuded that they have now become relict mountains, for example, Aravalito, Vindhyachal, etc. The Alpine folded mountains of the Tertiary period are grouped under the category of new folded mountains. For example, the Rockies, Andes, Alps, and Himalayas.

Characteristics of Folded Mountains

⦁ Folded Mountains are the youngest mountains on the earth’s surface.

⦁ The lithological characteristics of folded mountains reveal that these have been found due to the folding of the sedimentary rocks by strong compressive forces. The fossils found in the rocks of folded mountains denote the fact that the sedimentary rocks of these mountains were formed due to the deposition and consolidation of sediments in water bodies mainly in the oceanic environment because the argillaceous rocks of folded mountains contain marine fossils.

⦁ Sediments are found up to greater depths, thousands of meters (more than 12,000 meters). Based on this fact some scientists have opined that the sediments involved in the formation of sedimentary rocks folded mountains might have the marine fossils found in the rocks belonging to marine organisms which can survive in shallow water.
⦁ Fold mountains extend for greater lengths but their widths are far smaller than their lengths. For example, the Himalayas extend from west to east for a length of 2400 km but their north-south width is only 400 km. it means that folded mountains have been formed in long, narrow, and shallow seas.

⦁ Fold mountains are generally found along the margins of the continents facing oceans. For example, the Rockies and Andes are located along the western margin of North and South America respectively, and face the Pacific Ocean. They are located in two directions e.g. north-south and west-east directions (e.g. the Himalayas). The Alpine mountain of Europe is located in the southern margins facing the Mediterranean Sea.