Fold mountains

How are mountains formed? – World Atlas

Mountains are formed by movement within the earth’s crust. The crust itself is made up of several large plates, called tectonic plates, which float freely. These huge pieces of the earth’s crust move through molten rock called magma, allowing them to move and collide over time. Even though humans live on the crust, they don’t often feel these movements because they are very slow and the sheer size of each plate is so large. Nonetheless, these changes still have great impacts on human life as the movement of the plates is what creates changes in the geographic structure of the earth’s surface. In this way, mountains are created over time. When these plates collide, there is a lot of mass and pressure that suddenly stops, and it is this movement that forces the Earth to form loops or protrusions called mountains. Depending on how these plates move or collide, one of three types of mountains can be formed. The three types of mountains or mountain ranges are: volcanic mountains, folded mountains, and boulder mountains, each formed in a different way.

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Formation of volcanic mountains

Volcanic mountains form in areas where there is volcanic activity. This means that there is a place in the earth’s crust where there is a volcanic fissure or vent. Magma, or molten rock, is lighter than the solid rock around it. As a result, it tends to rise to the surface. Likewise, pressure and heat can build up underground and force an eruption of lava out of volcanic areas. This magma spurts out of the ground and creates lava flows that cool and harden in the open. Likewise, ash and magma can be thrown high into the air, where it cools and falls to the earth as debris. Lava flows and debris accumulate around the opening of the volcano, creating volcanic mountains. In many cases of larger mountains, this process has occurred over the centuries, with multiple eruptions, slowly building the mountain higher and higher. These two different ways in which volcanoes form mountains are described as cones or shield mountains.

Ash cones

An ash cone volcano. Image Credit: VectorMine / Shutterstock.com

Cinder Cone Mountains are volcanic mountains that build up when debris is ejected from a volcanic vent, then rains to the surface. The nature of the build-up of molten rock and ash also means that these mountains generally have a more jagged or rough texture.

Cinder cones exist all over the world, in areas of volcanic activity and plate cracks. They include: Kula and Karapina cones in Turkey, Taal mountain in the Philippines, Hverfjall in Iceland, Paricutin and Pinacate in Mexico, Luera, Fox and Elephant mountains in Australia, Manda-Inakir, which is on the Ethiopia / Djibouti border and a number of smaller cones on the west coast of North America, British Columbia, Oregon and California. Nicaragua is home to the most active ash cone volcano, called Cerro Negro.

Shield Mountains

Formation of the shield volcano. Image Credit: VectorMine / Shutterstock.com

The other type of volcanic mountain is known as a shield mountain. Shield volcanoes are made up of stratovolcanoes or composite volcanoes. In these cases, mountains build slowly over time. Like all volcanic mountains, these are also produced when magma escapes to the Earth’s surface through vents or cracks, but this is usually a slower process, because rather than expelling violently magma, these volcanoes produce oozing lava flows. Liquid rock flows ooze from cracks in viscous lava rivers, then solidify and cool on the surface. Sometimes they are fast flows, and sometimes they move slowly, but in both cases they build up layers of rock over time. A number of famous mountains on earth have been created in this way. Volcanic mountains can be found all over the world, and many island chains are actually volcanic rocks, like much of Hawaii. Mauna Kea is a well-known rock shield in the region, which is surrounded by almost 100 cones of ash.

Examples of shield mountains can also be found in many different countries including: Santorini, Greece, Pantelleria in Italy, Fukue-jima in Japan, in a wide variety of cities across Kamchatka, Upolu in Samoa and Socorro, and San Martin in Mexico.

Folded mountain formation

Like all mountains, fold-type mountains are created in areas where tectonic plates meet. These areas are called converging plate boundaries. Because these are areas where two plates meet, there is often a lot of friction or pressure that builds up along the edges of the plates as they move and move against each other. Mountains of folds are created when the plates push against each other in such a way that the earth’s crust bends, bends, or deforms. This process can create large, rolling mountain ranges or sheer mountains, but typically occurs over thousands or even millions of years. The plates will continue to push against each other and the earth will begin to slowly bend and warp as the pressure is maintained.

Folded Mountains are the most common mountains on earth and include some of the most famous mountain ranges. The longest mountain range in the world, the Andes of South America, are folded mountains, created at the meeting point of the Nazca Plate and the South American Plate. Likewise, the impressive Himalayan mountains form where the Indian Plate hits the Eurasian Plate, and the Alps exist for the same reason in Europe. Even the Appalachians are folded mountains, once taller than any other range on earth, that have been worn away and eroded over time. Folded Mountains can be further categorized, based on their shape and fold types, although most Folded Mountains have a variety of folds within their range. The folds of the mountains can be concave or convex, which means that they are respectively inclined inwards or bulging outwards. Likewise, folded mountains can have anticlines or synclines, two types of top-down ripples in compressed rock. The anticlines are domed upwards, with the middle of the ripple being the highest point, as well as the area where the oldest rock is located. Conversely, the synclinal folds create more shape at, and have the youngest rock in their center. These formations are very similar to domes and basins, which look and act the same in a folded mountain range. If the rock layers all tilt in the same direction, it is called a monocline, which means that it does not tilt or dome, but progresses tilting one point upward.

Other types of patterns in folded rocks include chevron shapes, which describe a zigzag edge of straight, crisp folds; sag folds, where the folds collapse on themselves due to soft rock types – usually sedimentary; ptygmatic where dikes form due to viscous materials; or disharmonic where a variety of rock formation types are present.

Mountain boulder formation

Illustration showing the formation of the mountain as a block.

Boulder mountains also exist at fault locations or along the edges of tectonic plates. Unlike folded mountains, which warp and ripple under pressure, boulder mountains break into large chunks, or boulders, as cracks in the crust are created from fault lines all the way to the surface. The extreme pressure caused by tectonic plates pushing against each other, or the gap when they pull apart, forces one block of earth up and the other down. This type of movement often results in geological formations known as rift valleys, where an area, near a fault, collapses, creating large valleys with steep walls on either side. The greatest example of this phenomenon is the Great Rift Valley which stretches from Lebanon to Mozambique.

Due to the way boulder mountains are formed, they tend to have a characteristic boulder shape and appearance. These large chunks of soil come out of the ground, in solid pieces with relatively straight edges. These can be classified into one of two main types of folded rocks: tilted and raised.

Survey

Mountains of raised boulders are the type that has been primarily described above. These mountains are created when blocks of the earth’s crust are pushed upward in a relatively straight motion. This means that the resulting shape is usually flat on top, or tabular, with straight, sharp sides. These sides clearly show the faults or cracks along which the earth shattered. These mountains can also be called horst mountains.

Inclined

The other main type of block mountain is called a sloping mountain and is made in the same way with one major difference. As the earth continues to crack and split along a fault due to compression, a tilted rock, as the name suggests, appears to have a tilted angle to it. This is caused by an imbalance in the cracks on either side of the block. Usually one side, the steeper, indicates the fault, while the other side is a much gentler slope. When a crack only occurs on one side of a large piece of land, that side juts out, while the other stays, forcing a sloping sloping top. There are a number of well-known boulder mountains on Earth. The Sierra Nevada mountain in California, United States is known as the largest boulder mountain on Earth. Other examples include: the Vosges and Black Forest mountains along the Rhine Fault in Europe, the Pakistan Salt Range, and areas of the Steen Mountain District in Oregon.


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