Types of Mountains:
Different movements of the Earth’s crust cause mountains to form. As the plates move together or apart, four main types of mountain are created – dome, volcanic, block and fold mountains.
1. Fold Mountains:
The formation of fold mountains
- Where an area of sea separates two plates, sediments settle on the sea floor in depressions called geosynclines. These sediments gradually become compressed into sedimentary rock.
- When the two plates move towards each other again, the layers of sedimentary rock on the sea floor become crumpled and folded.
- Eventually the sedimentary rock appears above sea level as a range of fold mountains.
Where the rocks are folded upwards, they are called anticlines. Where the rocks are folded downwards, they are called synclines. Severely folded and faulted rocks are called nappes.
Fold mountains are created through a process called orogeny. An orogenic event takes millions of years to create a fold mountain. When a tectonic plate gets pressure from two sides, it gets folded. Some of its portion becomes elevated and forms the mountains.
The depressions form the valleys. The Himalayas, The Andes and the Alps are examples of Fold Mountain. They are the young mountains of the world and hence they have some of the highest peaks of the world.
2. Block Mountains:
When large areas are broken and displaced vertically, Block Mountains are formed. In this case, the uplifted blocks are called horsts. On the other hand, the lowered blocks are called graben.
Examples of Block Mountains are; the Rhine Valley and the Vosges mountain in Europe.
3. Volcanic Mountains:
A mountain formed due to volcanic activity is called Volcanic Mountain. Examples of Volcanic Mountains are; Mt. Kilimanjaro and Mt. Fujiyama.
Andaman and Nicobar islands in India are the tip of the volcanic mountains which rise from the ocean floor.
4. Dome Mountains:
Dome mountains form when large globs of magma float up from beneath the crust and push up surface rocks, creating a rounded swelling in the crust. Once the magma cools, it creates a large dome of harder rock under the surface, which erosion sometimes reveals.
Dome Mountains are rounded, while Plateau Mountains have flat tops.
Dome Mountains form when hot runny rock (magma) under the Earth pushes up and bulges out. Plateau Mountains have steep slopes rising to a large area of flat land. They can form in different ways — when plates push together or magma is pushed to the surface.
The Sierra Nevada Mountains in the USA are Block Mountains.
When the Earth’s rocky plates pull apart, the outer surface of the Earth cracks. Massive chunks of rock collapse leaving blocks of mountains on either side. Block Mountains have flatter peaks than Fold Mountains.
The Andes in South America are Fold Mountains.
Fold Mountains are formed when one plate bumps into another and keeps moving, causing layers of rock to crunch together and lift upwards. Fold Mountains are mainly made from softer rocks, like limestone. The Himalayas in Asia and the Alps in Switzerland are also Fold Mountains.
Picture Credit : Google
