What is a mountain
A mountain is defined as mass of rock considerably very high occupying a vast area of land. This is made up of higher altitude and steep slopes. This altitude may reach to several thousand metres from the sea level. Some of the mountains may be located in isolation. For example, the Kilimanjaro of East Africa. However, some other mountains with several peaks may cover a large area (several thousand kilometres). This type of mountains are folded like the waves. For example, the Himalayan Mountain which extends from Pamir Knot in the east. The Rocky and the Appalachian Mountains of North America, the Andes of South America, the Alps, the Ural, the Caucasus of Europe and the Fujiyama of Asia and others are just few examples.
Several mountain building processes known as Orogenesis work together in the formation of the mountain. Greek word Oros means mountain and Genesis means formation or creation. Tremendous weathering particularly the wind, water and glacier bring substantial changes in the landforms. There are four types of mountains namely: fold mountain, block mountain, volcanic mountain and residual mountain.
Types of mountains
There are four basic types of mountains in the world according to their major characteristics
- Block mountain
- Fold mountain
- Volcanic mountain
- Residual mountain
Block mountain and it’s mode of formation
This is a type of mountain formed by faulting accompanied by tension and compressional forces. Faults on the other hand refer to fracture along line of weakness in rocks.
In the formation of fold mountain, there are usually two parallel faults or lines of weakness developing on the earth surface. The block enclosed by the two parallel faults remain as it is, the land on both sides of the parallel faults subsides, then the enclosed central block now standing up becomes the Horst or Block mountain. However in some part, this displacement may be upward and in another part it may be downward. The upward part along the fault is along the joint line of the two plates and due to lateral pressure, these sediments are folded giving rise to anticlines and synclines. The fold mountains are formed consisting of the synclines and anticlines covering a vast area.
Examples of Block mountains are The Black Forest of Germany, Hunsruck of Germany and the Salt Mountain of Pakistan. In the formation of block mountain, higher blocks are calledHorstsand troughs are calledgrabens. However, there are two valleys associated with the formation of block mountain, they include Horst mountain and Rift Valley or Graben.
Formation of rift valley or Graben
In the formation of Rift valley or graben, there are always two parallel faults forming in the earth crust. When this occurs, the block enclosed by the parallel faults remains as it is. The land on both side of the parallel faults rise while the enclosed central block now relatively low lying becomes the Graben. Typical example of this types of mountain is located in East African Rift valley and Central Valley of Scotland.
Fold mountain and mode of formaton
Fold mountains are usually formed by the earth movement which forces sedimentary rocks to fold in the process. This type of folding can be caused by a large scale horizontal earth movement. Stresses caused by expansion and contraction of some parts of the earth are set up in the earths crust, such stresses therefore subjects the rocks to compressive forces; these compressive forces produce wrinkling of the earth crust of the earth. The up fold of the wrinkles are called anticlines while the down fold are called synclines, they could cover a vast area on the earth surface. A fold mountain may appear simple, but where the compressional forces are complex, it results in over fold, when it is pushed further an over fold becomes a recumbent fold. In some instances, faults may leads to extreme folding to form an overthrust fold. Thesetype of mountains are generally constituted with the union of several vast and high mountain ranges. Examples of the fold mountains are: the Himalayan Mountains in Asia, the Alps in Europe, the Ural mountain in Russia and the Rockies Mountain in North America.
Volcanic mountain and mode of formation
volcanic mountain are formed by the accumulation and solidification of the molten materials ejected through the volcanoes. It is formed from materials ejected through the cracks, materials emitted could be any or all of molten lava, volcanic bombs, cinders, ashes and liquid mud. The material ejected are usually viscous in nature and once they are ejected fall around the vent in layers. Because of the stickiness of the material, they tend to build up cones called the volcanic mountain. Sometimes ,this type of mountain may cover small area with a steep slope and some other case may cover a large area with a gentle slope. Examples of volcanic mountain are mountain Fujiyama in Japan, Mountain Mayon in Philippines, Mountain Kenya, Mouna Loa (Hawaii island).Mount St. Helena of the United States of America, Mountain Elgon and Mountain Kilimanjaro in East Africa.
Residual mountain and mode of formation
Residual mountains are mountain formed by denudations, where the general level of the land has been lowered by agents of denudation. Some of the very resistant areas may be left and these gives rise to residual mountains. Residual mountain may also evolve fromplateau which have been dissected by rivers into hills and valleys. The inselbarges which are ubiquitous features of West African landscape are also examples of residual mountain. The major examples of residual mountain in Nigeria are the Idanre Hills and the Ado ekiti Rock in western parts of Nigeria. Other world examples are the Deccan Plateau and Nilgiri Mountains in India, Scandinavian Mountains in Europe and mountain Monadnock in United States of America.
How are mountains useful to us?
- Climate: mountains modify climate thereby making it ideal for human settlement such mountains include: Kenya mountain, mountain Elgon, Kilimanjaro mountain and Jos plateau in Nigeria.
- Tourism: mountains of the world also serve as tourist attractions or holiday resorts for many who love the sight of them such tourist attractions are the Deccan mountain, Olumo rock, idare hills and the Swiss alps where a lot of people visit yearly..
- Minerals: mountains are usually source of minerals to man. The common minerals from these highlands include tin and columbite as in the case of Jos Plateau, minerals like coal as in the case of Udi Hills and lastly gold from Rockies mountain in North America.
- Source of rivers: mountains do serve as sources of rivers in the world for example, River Niger from Guinea highlands in West Africa. The Blue and White Nile from East Africa highlands.
- Defence: mountains of the world serves as haven against invaders , these used to be important hiding spots especially in the olden days when slavery was the order of the day.
- Pastoralism: the presence of mountains in some parts of the world make possible the practice of transhumance on mountain pasture as in the case of Switzerland and Australia.
- Lumbering: mountains also encourage lumbering activities along their slopes as clearly seen in Scandinavia for timber, paper, pulp and matched industries.
- Construction: rocks from mountains and highlands are commonly used for construction of roads, bridges, culvert, dams and houses. A very good example are the rocks from Shai hill which were used to construct the Tema harbour in Ghana.
- Boundaries: mountains do present as natural boundaries as clearly see in Cameroun mountain between Nigeria and Cameroun.
- Agriculture: mountains do serve as terrace farming; a system of agriculture that uses steps that are built into the side of a mountain or hill. This practice prevents soil erosion and nutrient run-off. For example, this type of farming system is practiced around Asia, Andes in south America,Biu plateau, Jos plateau and Udi Hill in Nigeria.