Mountains are landforms made from earth and rock, elevated from the surrounding terrain in a limited area with steep slopes and sharp or round peaks. They are pretty outstanding landmarks that are difficult to miss that account for one-fifth of the world’s land surface and home to one-tenth of the human population.
They rise to heights generally above 300 meters above sea level, with the mountain boasting the highest peak towering at 8.850.1728 m- Mount Everest in the Himalayas. The world’s smallest registered mountain, Mount Wycheproof in Australia, stands at 146 m above sea level. Another interesting fact would be that most mountains occur in oceans than on land, and some islands are, in fact, rounded peaks of mountains coming from the seabed.
How Are Mountains Important?
Mountains may not form the bulk of the landmass, but they considerably affect our environment and our lives as a result. Around 80 percent of the earth’s freshwater originates from mountains, and they are our most significant water catchment areas.
They experience more rainfall than low-lying land because of the nature of the atmosphere. They have lower temperatures when moist winds are passing through them. They lose the moisture because cool air has a lesser capacity to hold moisture.
Hence more rainfall in the mountains and thus our primary source of fresh water from which rivers and streams spring form. However, our recent reckless behaviors that have affected the climate leading to global warming have ignited an opposite effect in recent times.
Due to increased temperatures caused by the greenhouse effect, more melting of glaciers and snow has led to increased sea levels and floods, amongst other unpleasant effects.
On a positive note, however, these landmarks are still excellent sources of livelihoods and leisure activities. Most farming activities are done on mountain slopes, which well produces the bulk of the food we consume on a daily.
Leisure activities are also not left out because of the rich ecosystem that these areas boast. They include mountaineering, paragliding, hiking, and skiing, amongst many others.
How are Mountains Formed?
Mountains appear in different types and sizes and are distributed across land depending on their respective features. The different types of mountains are formed in different ways informed by orogenic processes.
This refers to the processes that lead to mountains that include faulting, folding, volcanic activity, metamorphism, and igneous intrusion. The earth is made up of tectonic plates that fit perfectly together, whose movement, whether it is a collision or subduction, causes the rise in massive landmasses that we call mountains.
Types of Mountains
There are five major types of mountains that differ majorly in the orogenic process that led to their existence and physical appearance. The five major types are:
- Fold Mountains formed due to the folding of rocks in the earth’s crust.
- Fault / Block Mountains formed due to faulting of rocks along fault lines.
- Volcanic Mountains formed due to the eruption of molten rock in the earth’s crust to the surface
- Dome Mountains formed due to the rise in molten material in the earth’s crust.
- Plateau Mountains formed by the erosion of surrounding areas of land
The five types above are formed due to wide-reaching shifts in tectonic plates or earth’s crust, also known as plate tectonics. Before plate tectonics came in the 1970s, geosyncline theory was used to explain the formation of mountains until it was discredited as a reliable geological framework on which to base ideas on geological features.
Other notable types that have only slight variations from the main types would be:
Inselberg – refers to a small mountain that rises instantaneously from a flat or level surrounding area. If the inselberg is dome-shaped, it is called a Bernhardt. Both strongly lean towards the plateau mountains but are generally smaller in size.
Seamount- refers to a mountain that rises from the seafloor but doesn’t get to the water surface. It is volcanic and was once feared to threaten marine life.
These are the most common of the five types globally and are formed when two or more tectonic plates collide with each other like titans crushing against each other. The resulting layers of rock at the destructive boundaries are folded and forced upwards, which is now our fold mountains.
Owing to the process of formation, you will often find these mountains in ranges as the rocks were scrumpled together. For instance, the Himalaya ranges result from the Indian plate colliding with the Eurasian Plate, and the folding process is still not complete.
Most of the Fold Mountains are made up of metamorphic rocks and sedimentary rocks formed under low temperatures and high pressure. Fold Mountains are also defined by a key feature in their appearance called a fold primarily differentiated by their shape, say convex or concave. The most common folds are the anticlines and synclines. The anticline is an up-fold that assumes a shape like a letter n, with the oldest rocks being in the center of the anticline. On the other hand, a syncline is the opposite and assumes a u-shape with the youngest rocks of the fold taking center stage.
The Fold Mountains can also be categorized according to their geological ages. Young Fold Mountains are roughly 10 to 25 million years of age, while old fold mountains are approximately 200 million years of age. Examples of the Fold Mountains are quite a number and include the Himalayas, Andes, and the Alps ranges in Asia, South America, and Europe, respectively.
Fault or Block Mountains
Often described as mountains with steep front sides and sloping backsides, Fault Mountains are just a tweak of Fold Mountains. Instead of the folding that occurs in the latter here, the rocks break up into blocks that are forced up and down due to the tensional forces acting on the earth’s crust.
The tensional forces could either uplift parts of the earth’s crust or by convection forces moving in opposite directions at fault lines, which then cause the displacement of the rocks and subsequent fault mountains. Examples of the Fault Mountains are the Harz Mountains in Germany and the Siera Nevada mountains in North America.
These mountains are formed by volcanoes, just as the name suggests. Perhaps the most hazardous of them all are formed when molten material, also called magma, erupts while deep in the earth’s crust due to pressure through fissures and get to the surface.
When tectonic plates collide with each other, and one is pushed down, the molten material is now released between them through cracks in the earth’s crust (fissures) as it heads to the surface. Upon hitting the surface, magma, which is now called lava, along with debris and ash pile on the surface layer after layer. Once the lava cools, it forms hard cones of rock that form a volcanic mountain when piled up one after another.
Most of the volcanoes are found within a belt around the pacific, called the fire ring. Volcanoes may be categorized according to their propensity to erupt or by their shape. The former gives us three types, namely active, dormant, and extinct.
Active volcanoes are volcanoes that can erupt at any moment or often. There are 1510 active volcanoes in the world, with the largest being the Mauna Loa in Hawaii Island, which has erupted a recorded 33 times since 1843. Dormant volcanoes can equally erupt any time but have not done so in a while. Lastly, Extinct volcanoes are defunct, just as the name would suggest, and have not erupted in a very long while and may never erupt again.
When categorized according to their shapes, we have shield, composite, cinder, and lava domes. The viscosity and thickness of the magma are a major determiner of the shapes of the volcanoes. Shield volcanoes are flat because the magma is runny and escapes easily with no explosion.
Composite volcanoes are tall and thin since the magma is thick and adhesive; hence the gas doesn’t easily escape, thus causing an explosion as it does and a steep-sided volcano as a result.
Cinder cones are circular or oval and result from lava that disintegrates into smaller pieces as it erupts, causing cinders when they cool around the vent. Lava domes are too steep-sided due to the lava being too thick, and it piles next to the vent. Other Examples of volcanoes are Mount Fuji in Japan and Mount Kilimanjaro in Tanzania.
As the relationship between Fault Mountains and fold mountains, Dome Mountains are not very different from volcanoes. They are formed when molten material beneath the earth’s crust pushes up the sedimentary rocks above them but doesn’t get to the surface like in volcanoes. The resultant rocks form a dome shape due to the pressure of the rising magma that cools, forming hardened rock before reaching the surface.
The overlying rocks are pushed upward to look like an inverted bowl hence the dome shape, but the adjacent land remains level and flat. Since the dome is way higher than its surrounding, there is erosion due to rain and wind, further resulting in mountain ranges that are spherical or circular in appearance. Dome Mountains are Navajo, the La Sal, and the Sierra Nevada range, all located in the United States. They are typically not easily spotted.
Unlike the rest, these mountains are not formed by internal activity but by external factors. They are formed purely by erosion acting on the earth’s crust. Plateaus are generally lands that are level tables of land that are significantly raised compared to the surrounding area despite being flat terrain. These lands are always way high above sea level, often having a hill or mountain on one side.
They are mostly a result of forces within the earth or lava that cooled on the surface, thereby raising the surface. They are mostly located near folded mountains. As time passes by, water and wind erode the plateau by creating valleys in the area, thereby leaving mountains erect between the valleys in the process. Examples of Plateau Mountains are the mountains in New Zealand.