Fold Mountains

Fold mountains are created when two or more of the Earth’s tectonic plates collide. After the collision, compressing boundaries are formed where rocks and debris are warped and folded into rocky outcrops, hills, mountains, and entire mountain ranges.

Fold mountains are the resulting landforms from the upward movement of the tectonic plates when lateral compression forces are present.

Fold mountains are created through a process called orogeny.

Periods of Fold Mountains:

In the history of the Earth, several mountain-building periods are recorded. For instance, the three most recent ones are known as the Caledonians, the Hercynians and the Alpine which took place 310, 240, and 30 million years ago respectively.

This Caledonian period produced extensive mountain ranges. They were subsequently lowered due to the influence of agents of denudation. The mountain stumps of Scandinavia and the Scottish Caledonian mountains are remains of the Caledonian mountains.

The Cape range of South Africa, the Ural of Asia and the Appalachians in North America are of the Hercynian Mountains.

The ones that are most recently formed are the Alpine period like the Alps, Atlas Mountains, the Rockies, the Andes and the Himalayas. They are the most impressive and the highest of all the mountains. They are like other mountains formed by or developed by the collision of continent-carrying plates which made the continental crust rocks where a great amount of sediment derived from these rocks, get interwoven and folded.

Characteristics of Fold Mountains:

Fold mountains have the following characteristics:

• They belong to the group of the youngest mountains on the Earth.
• Due to their mode of formation, their folds form distinct peaks.
• Fold mountains extend to great heights and form the highest mountain ranges.
• Sedimentary rocks are formed due to deposition and consoli­dation of sediments. Therefore, Fold mountains are layered in structure and contain fossils.
• Due to its mode of formation, fold mountains shorten the Earth’s Crust.
• Fold mountains are the most widespread type of mountain on Earth.
• Fold mountains have active volcanoes.
• They are rich in mineral resources such as tin, copper, gold etc.
• Fold mountain ranges are often subject to extensive glaciation and erosion, which shape the landscapeA landscape is the visible features of an area of land, its landforms, and how they integrate with natural or man-made features, often considered in terms of their aesthetic appeal. A... More and expose the underlying geological structures.

Examples and Locations of Fold Mountains:

Some of the prominent fold mountains include some that are single isolated mountains while some in ranges;

Africa:

Africa has fewer fold mountain ranges compared to other continents and they include:

• Atlas Mountains (North Africa) – Extends through Morocco, Algeria, and Tunisia.
• Cape Fold Mountains (South Africa) – They run along the southwestern and southern coastlines of South Africa.
• Drakensberg Mountains (Southern Africa) – Extends through South Africa and Lesotho.
• Akwapim-Togo Ranges – It stretches across the central region of the West African country of Togo and across the eastern and western borders of that country into Ghana and Benin. In Ghana, the range is also known as the Akwapim Hills, and in Benin, it is also known as the Atakora Mountains.

Other parts of the world:

• The Himalayas is a mountain range in Asia.
• The Alps are one of the highest and most extensive mountain ranges in Europe.
• The Rocky Mountains is a mountain range in North America.
• The Andes in South America.
• The Sierra Madre Oriental is a mountain range in northeastern Mexico.

Note: Cordillera is a chain of mountain ranges (cordilleras) that consists of an almost continuous sequence of mountain ranges stretching from Alaska in North America to the southern tip of South America. In North America, the Cordillera includes the Rocky Mountains, Cascade Mountains, Sierra Nevada Mountains, Sierra Madre Occidental & Sierra Madre Oriental, Yukon Mountains, Alaska Range, Brooks Range, Columbia Mountains, and the Coast Range. In South America, the Cordillera includes all the mountain ranges of the Andes. See your Atlas.

Formation of Fold Mountains:

Fold Mountains are formed from large-scale horizontal movement of the Earth’s tectonic plates, this movement is due to stress and compressional forces. This causes the expansion and contraction of different areas on the Earth’s surface. These compressional forces also produce the folding of the Earth’s crust.

The folding of the Earth’s crust creates two major parts in Fold Mountains, the upfolds of the fold mountains are anticlines, the anticline folds upwards to form a ridge while the downfolds are called syncline, the syncline arches downwards to form a trough.

Types of Fold Mountains:

Types of Fold Mountains are:

1. Simple Fold Mountains: These mountains are formed where the rocks that folded and are not broken or torn by the movement. They are formed by simple, unilateral compressional forces so the resulting fold mountain is simple in structure.
2. Asymmetrical Fold Mountains: In this type of fold mountain the two limbs ( or sides) of the fold mountain are not mirror images of each other. One limb (or side) of the fold is steeper than the other limb (or side).
3. Overfold Fold Mountains: Here, the fold is such that it is tilted past the vertical (90°) to such an extent that the layers on the anticline (the top of the fold) are close to the syncline.
4. Recumbent Fold Mountains: Here, intense compressional forces cause the rock layers to fold over themselves. The anticline (the top of the fold) is nearly horizontal to the syncline or has a very low angle to the syncline.
5. Overthrust Mountains: Here, due to the high compressional pressure the fold breaks so a crack or fault occurs in the fold and one limb (or side) is pushed forward over the other limb (or side).