distinguish between old fold mountain and young fold mountain
The Fold Mountains are of two types:
- New or Young Fold Mountains - The Alps, the Himalayas, the Circum-Pacific oceanic mountains, etc., are worth mentioning. The main characteristics of these mountains are the complex folding of the rocks, faulting, Volcanic, activities, cordillera form, the erosion and weathering caused by running water, ice, winds, etc., the existence of glacier-capped high peaks, etc.
- Old Fold Mountains - This type includes the Caledonian and Hercynian mountains of Central Europe, the Pennines, the highlands of Scotland, etc. These mountains were folded in very ancient times. They were, then, subjected to denudation and uplift, many faults were formed and the layers of the rock were wrapped. Many mountains exist as relics, due to erosion. The presence of monadnocks, accordant summits, sculptured domes, the irregular forms of peaks, relics plateaus, etc., are some of the important characteristics of these mountains.
- (b) Lacolith Mountains - The outrushing magma forms the fissures, the crust of the earth at a place into a dome, mountains formed in such a way are called Lacolith Mountains.
- (c) Block Mountains - These Mountains were formed on the crust due to tension. Faults are formed due to tensional forces. A part of the land block is depressed so that the remaining block stands conspicuously above the surroundings. Mountains formed in this way are called block mountains and the depressed portion is known as rift valley.
The Block Mountains have a steep and small slope towards the rift valley but the slope on the other side is long and gentle. The layers of the mountain are parallel to the gentler slope. There are many block mountains in Oregon (U.S.A.) whose crest line has not been much deformed by erosion. The Block Mountains of Nevada and Utah have been eroded down.
- (d) Mountains of Accumulation - These Mountains have been formed by the emission and deposition of lava. The slope of the mountains becomes steep and height increases due to the development of the cones. The mountains formed by cones, for example are Papocatepetl in Mexico, Mount Raineer in Washington, the Vesuvius in Italy, the Fujiyama in Japan, the Aconagua in Chile, etc. The Aconagua is 7,000 meters high.
- (e) Relict or Residual Mountains - The mountains which are subjected to weathering and erosion for a long time, are lowered down and are called Relief or Residual mountains. The mountains of the Western Ghats, the Aravalli Mountain and the Parasnath mountain of Bihar belong to this type.
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