What is a mountain? Based on the general definition of the mountain is a higher part of the Earth's surface than the surrounding area. The implication of this definition is that the mountain can be located anywhere. However, in geography, the location of the mountain has its own rules of play. Mountains are generally only on the border of the moving plate.
In the science of earth known plate tectonic theory. According to this theory, the Earth consists of plates that are constantly moving. The plate is a combination of two layers of Earth's skin. The earth, as seen in the image below, consists of a core layer, a mantle, and a crust.
Earth Plates, red color indicates mountain and volcano paths
The Earth's core is divided into an inner core of solid iron and a liquid outer core. The temperature at the core is estimated at 4300 ° C with a depth of 2900-5200 km. On top of it is a mantle coating that lies at a depth of about 2900 km, whose temperature ranges from 1000-3700 ° C. This layer is also liquid but more viscous than the outer core. In the mantle layer, there is a convection current that moves the crust on it.
In the outermost part of the Earth, there is a relatively cold, dense, and thin layer of crust (the thickest 30 km). The crust is subdivided into continental crust and oceanic crust. The density of the oceanic crust is higher than that of the continental crust. However, the continent's crust is relatively richer than the oceanic crust. This top and crust coat forms the plates.
On Earth, there are about 5 large plates and several small plates. The five large plates are the Pacific Plate, the African Plate, the Indo-Australian Plate, the Eurasian Plate and the Antarctic Plate. The plates throughout the year continue to move and interact on the border. This interaction can be either convergent, diverging or transforming.
In the convergent interaction, there is a collision between the plates and then one of the plates dip (dip) down the other plate. If a collision occurs at sea, a trough will form along the boundary between the two plates. The plunger is a heavier plate (higher density), which is usually an oceanic plate. When it reaches the mantle, the plunging plate is partial melting. The melt of this plate is the raw material of magma.
In the divergent interactions that generally occur in the middle of the ocean floor, the plates are mutually excited by the impulse of magma material from within the mantle. The magma that drives the partial plate appears to the surface, freezes and produces new plates. The boundary between the plates in divergent interactions is marked by the mid-oceanic ridge. This ridge is actually a series of volcanoes where the magma exit that forms a new plate. But these volcanoes are relatively harmless because they are far from human settlements.
While in the interaction of intersections, the plates rub against each other without forming division or subduction. No melting of old plates nor the appearance of new plates.
In the convergent and touching interactions, the plates collide or rub together. These crashes and frictions create tension on the two plates, similar to what happens to a tense piece of steel ruler because it is bent. If the steel ruler returns to its original position, there will be a vibration accompanied by a loud enough sound.
If brought into the context of the Earth, one of the plates will be bent by the pressure of the other plate. If the bent plates return to their original position, the vibrations that humans will experience as tectonic earthquakes, accompanied by the breaking of the plates. Strong weak earthquake vibration, among others, depends on the depth of the occurrence of fracture, or in other words the depth of the epicenter. In addition to fractures, collisions and friction also create cracks/fractures, especially at the edges of each plate.
The fractures that arise will be the channel through which the magma from within the mantle. Magma then out to the surface, frozen, collected and buried to form a volcano. This is one of the mechanisms of the formation of mountains in plate boundaries. Another mechanism is the plates that do not sink folded or clumped upward to form a mountainous bulge. This condition is similar to the occurrence of a folded carpet upward when the edge "hit" the wall or cabinet.
The mounts formed at the boundaries of the convergent plates are divided into three types, namely the type of Himalaya, the type of volcanic arc and archipelagic type.
Himalayan type is a series of mountains that formed due to a collision of continental plates with continental plates. One of the plates is folded and protrudes upward. The other continental plate dipped downwards. Because of its thickness, the continental plates melt at considerable depth. The magma thus formed is so deep that it is unable to reach the surface. Examples of this type are the Himalayas.
1. Himalayan Mountains
Type volcanic arc is a series of volcanoes that formed due to the collision of oceanic plates with the continent. The oceanic plate dips under the continental plate. Because it is relatively thin, the oceanic plate melts at shallow depths. The magma produces so easily surfaces.
2. Mountains of volcanic arc type
An archipelago is a series of volcanoes that make up the archipelago. Formation of archipelagic arches is similar to the type of volcanic arc. The difference, the two plates that collide on this type is the oceanic plate.
3. Island archipelago mountains type
Based on the above description, it appears that mountains are generally formed and are in the boundary area between the plates are constantly moving, especially in the boundaries of convergent and divergent interactions. At the boundary of convergent interactions (Himalaya type, volcanic arc and archipelago arc), the mountains are able to reduce shocks due to a collision between the plates. This ability arises because the mountain has mass and a very large thickness.
As mentioned above, the plates that fall into these two types are generally thin. Because thin, in addition to more easily melt, the plate is also more easily broken at shallow depths. As a result, In these areas, the seismic centers are generally shallow (depth <33 and="" br="" dangerous="" energy="" human="" is="" km="" large="" life.="" relatively="" shock="" so="" that="" the="" to="" very="">
Therefore, mountainous areas are dangerous areas for settlement. A relatively safe place is the area behind the mountain, which is far from the interaction zone between the plates. Despite the shock, its strength has been greatly reduced by being muffled by the mountain.
Beyond the boundaries of convergent or divergent plates, volcanoes actually appear in other locations as well. These locations do not lie on any plate boundary, instead, are located in the middle of the plate. An example is in the heart of the African continent, or in a series of Hawaiian Islands. The volcanoes there are close to human settlements, but far from any plate boundaries (convergent, divergent, or intersect). Being far from the plate boundaries, the mountains simply do not dampen the shocks.
The mountains in the heart of Africa and the Hawaiian Islands emerged as a result of the hotspot phenomenon. There l.k. 40 hotspots across the surface of the Earth. One growing theory suggests that hotspots arise due to the presence of narrow channels that pass the hot material from the border of the earth's core and the mantle. Another theory explains that the hotspot is nothing else because of the convection flow of mantle material, the flow that also causes the movement of the plates. Until now scientists have not been able to fully explain this phenomenon. https://blogeducationforstudents.blogspot.com/2018/03/why-sea-water-is-salt.html
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