Block mountains

Block mountains archives – universe today


Seeing the size and majesty of the mountains, the ancient humans couldn’t help but feel that they were standing in the presence of something… divine. And in the belief systems of many ancient cultures, it was generally held that mountains were something spiritual – serving either as a home for the gods, or as a result of their activity, or as a place to draw near to God.

Thanks to modern geology, we now know the true history of mountain formation. Simply put, they are the result of tectonic forces or volcanism. But knowing this did not diminish their awesome and awe-inspiring nature. When a geological formation is created by forces that can only be described as titanic, this is to be expected. But how are mountains formed?

In truth, there are three ways of forming mountains, which correspond to the types of mountains in question. These are known as volcanic mountains, folds and boulders. All of these are the result of plate tectonics, where compressive forces, isostatic uplift, and the intrusion of igneous material force the rock to rise upward, creating a relief that is higher than the surrounding features.

Over millions of years, these uplifted sections are eroded by the elements – wind, rain, ice, and gravity. These gradually wear down the surface of the mountains, making the surface younger than the rocks that form them, and lead to the types of formations and distributions we know today.

The east side of the Matterhorn, a folded mountain that measures 4,478 meters in height, is reflected in Lake Riffelsee. Credit: Wikipedia Commons / Dirk Beyer

Volcanic mountains:

Volcanic mountains form when one tectonic plate is pushed under another (or over a mid-ocean ridge or hot spot) where magma is forced to the surface. When the magma reaches the surface, it often builds a volcanic mountain, such as a shield volcano or a stratovolcano. Examples of this type of mountain include Mount Fuji in Japan, Mauna Kea in Hawaii, Nyamuragira in the Democratic Republic of the Congo, Skjaldbreiður in Iceland, and Mount Etna in Sicily.

At other times, the rising magma solidifies below the surface and forms dome-shaped mountains, where the material is pushed upward by the force of the underlying build-up. Examples of this training include Navajo Mountain in San Juan County, Utah; the lava dome of Chaitén in Chile, Torfajökull in Iceland and Mount St. Helens in Washington state.

Fold the mountains:

As the name suggests, folded mountains occur when two tectonic plates collide with a converging plate boundary, causing the crust to thicken. This process forces the less dense crust to float above the denser rocks of the mantle – the material being forced upward to form hills, plateaus, or mountains – while a greater volume of material is forced upward. down in the coat.

Satellite image of the Himalayan mountain range, illustrated by NASA's Landsat-7 imagery of the Himalayas.  Credit: NASA
Satellite image of the Himalayan mountain range, as taken by NASA’s Landsat-7 satellite. Credit: NASA

The Jura Mountains, a series of subparallel mountain ridges located in the Alps, are an example of folded mountains. Other examples include the “simply folded belt” of the Zagros Mountains, which stretches from northern Syria and southern Turkey to eastern Iran and the Persian Gulf. There are also the Akwapim-Togo ranges in Ghana and the Appalachian Ridge-and-Valley in the eastern United States.

But perhaps the most famous is the Himalayan mountain range, located between northern India and Nepal. This chain was formed as a result of the collision between the Indian subcontinent and Asia about 25 million years ago, and gave rise to the world’s tallest mountain – Mount Everest.

Bouldering mountains:

Boulder mountains are caused by faults in the crust, a layer where rocks can intersect. Also known as rifting, this process occurs when rocks on one side of a fault rise above the other. The uplifted blocks become mountains of boulders (also called horsts) while the intermediate abandoned blocks are called graben (i.e. depressed regions).

Examples of this type of terrain are found in the Haut-Rhin valley, the Vosges in France, the Black Forest in Germany and the horsts of Vindhya and Satpura in India. There is also the East African Rift, an active continental rift zone with several active volcanoes stretching from Eritrea to Mozambique.

Satellite image of the East African Rift, December 18, 2002. Credit: NASA / GSFC / METI / Japan Space Systems, and US / Japan ASTER Science Team
Satellite image of the East African Rift, taken December 18, 2002. Credit: NASA / GSFC / METI / Japan Space Systems / US-Japan ASTER Science Team

Mountain erosion:

As noted, the last way mountains form is through erosion. This happens during and after an uplift, where a newly formed mountainous region is subjected to the effects of wind, water, ice and gravity. These forces actively shape the surface of mountain ranges, wear away exposed surfaces, deposit sediment in alluvial flows and lead to the formation of characteristic landforms.

These include pyramidal peaks, knife-edge ridges, and bowl-shaped circuses that may contain lakes. Plateau mountains, such as the Catskills, are formed by the erosion of a raised plateau. And after millions of years of erosion, mountains may cease to exist altogether.

Considering the size and scale of a mountain, the immense forces involved in their creation, and the immense time it takes to shape and form them, it is no wonder that they are considered so important. Between their religious significance (i.e. Mount Zion, Mount Olympus, Mount Ararat and Mauna Kea, to name a few), their scenic value, the challenge they present and Important to the earth sciences, these geological formations continue to hold a place in our hearts, minds and culture.

As we explored other planets, we also discovered new and impressive mountain formations that taught us a lot about geological activity and the composition of other worlds. For example, there is the volcanic mountain on Mars known as Olympus Mons, which happens to be the largest mountain in the solar system. And that’s just a drop in the bucket. Wherever there is a geologically active planet, there are mountains!

We have written many articles on the mountains here at Universe Today. Here’s one on the Fault-Block Mountains, one on the Volcanic Mountains, one on the Fold Mountains, and one on the Dome Mountains. And here is an article on the clearest sky on earth.

For more information, see NASA’s human spaceflight page, and here Earth visible from NASA.

Astronomy Cast also has a great episode on the subject – Episode 51: Earth.