How Are Mountains Created? - Orogenesis Mountain Formation

After many scientific observations and investigations, by the 1970s the theory of plate tectonics made it possible to explain how mountains originate. This theory was an initial link that allowed the elaboration of a coherent explanation about the process of formation of the terrestrial mountain ranges. These mountain ranges are present on the lithosphere, i.e. the earth's crust and upper mantle.

In order to understand the formation of mountains, we must understand what happens below them, under the surface of the earth. Mountains originate through a complex geological process called orogenesis (also known as orogeny) in which a large area of the earth's crust is shortened and thickened. This process occurs due to deformation and fracturing through the movement of large plates called tectonic plates.

The shifting of tectonic plates leads to mountain formation thanks to endogenous factors (i.e. factors from the plates themselves):

1. Orogeny takes place from the increase in temperature that comes from the gravitational tension of the Earth and the disintegration of the atoms that compose it. As the tectonic plates move, the heat from underneath the crust has an effect on the terrestrial material above it.
   
   
2. This heat is transferred from the warmer internal areas to the colder areas of the earth's lithosphere, producing a convergent movement in which the continental plates come together.
   
   
3. The final part of the formation of the mountains is due to the rising warm material passing up above the earth's surface. This marks the end of the movements and the union of the two mobile plates. From this instance, the mountains behave as stable structures that can remain for millions of years.

Once the uplift has produced the mountain ranges, these are shaped by exogenous factors. Such factors include erosion caused by ice, wind, and rain. It is these processes which give the mountains their shape and structure, for example, mountain peaks and cliff edges.

Exogenous factors are critical in the ongoing evolution of mountain landscapes. Erosion, for example, gradually wears down mountain surfaces, contributing to their eventual transformation into hills and plains over geological time spans. Additionally, the impact of glaciers carving through rock can create unique valley shapes that define certain mountain ranges.

Mountains can be found in various parts of the world. Learn more with our article explaining the different types of natural regions with examples.

Each mountain presents particular characteristics that define them. Many of their characteristics are defined by their height and the weather systems of their geographical locations. These characteristics lead to different flora and fauna being able to exist in these often difficult habitats.

Mountain weather

In mountain ranges, the climate is generally more humid and cold compared to the lowlands. The average temperatures are low and these decrease as the altitude increases. It is said that every 100 meters in height, the air temperature decreases from 0.5 °C to 1 °C (32.9 to 33.8 ºF).

When the air masses coming from the oceans loaded with moisture collide with these mountain ranges, they rise above them. When they do so they cool and condense, giving rise to precipitation, generally in the form of snow. When this snow accumulates and compacts as the years go by, glaciers are formed, large freshwater reservoirs present at the top of many mountains.

Climatic variations can lead to severe weather conditions, including intense storms and avalanches, which can dramatically alter the landscape. The presence of glaciers also influences the hydrology of mountain regions, impacting river flows and water availability downstream.

Mountain vegetation

Factors such as temperature, humidity, soil characteristics, and solar radiation determine the different vegetation floors that exist on a given mountain. These territories are made up of different plant communities.

In the lower regions, i.e. those at a lower altitude, the plant species that develop are similar to the flat environment. As the height increases, the species present adaptations to be able to face adverse conditions, such as freezing temperatures, harsh rain, and very strong winds. As we advance even further upwards, the richness of species decreases. Plant species vary depending on the continent and latitude of a given mountain.

For instance, in the Andes, you'll find species such as the Polylepis tree, which can survive at higher altitudes than most other trees. In contrast, the Himalayas host a variety of rhododendron species, adapted to the cold and wind.

Mountain wildlife

There are animals that can live at high altitudes. Although mountains are a challenging environment for these species, many can adapt and survive against these conditions. Let's get to know some of them now:

• Guanaco (Lama guanicoe)
• Llama (Lama glama)
• Vicuna (Vicugna vicugna)
• Deer such as the South Andean deer (Hippocamelus bisulcus) and the taruca (Hippocamelus antisensis)
• Bears such as the Himalayan black bear (Ursus thibetanus laniger)
• Foxes such as the culpeo (Lycalopex culpaeus) and the South American gray fox (Lycalopex griseus)
• Wolves such as the Iberian wolf (Canis lupus signatus) and the Himalayan wolf (Canis himalayensis)
• Cougar (Puma concolor) and many other felines, such as the kodkod (Leopardus guigna) and the snow leopard (Panthera uncia)
• Armadillos like the pichi (Zaedyus pichiy)
• Andean condor (Vultur gryphus) which glides in the air and nests in holes or caves present in rocks at high altitudes
• Darwin's rhea (Rhea pennata)
• Condors or New World vultures of the family Cathartidae
• Eagles such as the black-chested buzzard-eagle (Geranoaetus melanoleucus)
• Toucans such as the Plate-billed mountain toucan (Andigena laminirostris)
• Falcons such as the peregrine falcon (Falco peregrinus)
• Blackbirds or thrushes of the genus Turdus

It should be noted that the species that inhabit the mountains around the world are very numerous and we can only mention a few of them here. High-altitude animals have developed unique adaptations, such as increased lung capacity and efficient circulatory systems, allowing them to thrive in environments with lower oxygen levels.

Although all orogenesis mountain creation is due to tectonic movement, there are different types of mountain formation within this process. For this reason, geologists and volcanologists have classified different types of mountains into the following categories:

• Volcanic mountains: volcanic mountains are those that rise during volcanic eruptions due to the accumulation and hardening of magma and by rocks that have solidified at depths below the earth's crust.
  
  
• Folded or folding mountains: folding mountains are those that are formed by the collision of tectonic plates in which the rocks that make them up are compressed and folded. It is this way that the extensive mountain ranges that we know today have originated.
  
  
• Fractured or block mountains: block mountains are those that are formed by geological faults, i.e. by breaks that occur in the earth's crust. The separation of the surface causes powerful forces to separate tectonic plates and the center block to fall. The result is the formation of a mountain within the fault.
  
  
• Warped, residual or denudation mountains: these types of mountains are formed as a result of the erosion of an area that was formerly elevated. Erosion is mainly caused by climatic factors, whether by water, wind, or glacial erosion.

These classifications help geologists understand the complex history and transformation of the Earth's crust. The Himalayas, for example, are classic folded mountains, formed by the collision of the Indian Plate with the Eurasian Plate. In contrast, the Sierra Nevada in the United States exemplifies block mountains, shaped by faulting and uplifting processes.

One of the world's most famous mountain ranges is the Andes of South America. Take a look at our related article to see the plants and animals of the Andean Mountains.

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