Subduction is defined as the downward movement of the edge of a tectonic plate – immense pieces of rock that interact with each other and form earth’s crust – into the mantle beneath another tectonic plate. The area in which this takes place is known as a plate boundary. There are three types of plate boundaries: convergent, divergent, and transform. Subduction is one of the possible outcomes of convergent plate boundaries, in which the tectonic plates move into each other. There are two basic types of convergence, which are both determined by the density of the tectonic plates involved. The first is when you have plates of different densities, in which the more dense plate will be forced under the less dense plate in the process of subduction.
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However, it is vastly different with mountains formed from subduction. Some are formed from the less dense tectonic plate crushing into the more dense subducting tectonic plate and creating ripples, much like the effect of a soda can or a car. Mountains made this way tend to have many folds and therefore be high in metamorphic rocks such as schist, “a coarse-grained metamorphic rock that consists of layers of different minerals and can be split into thin irregular plates”, and gneiss, “a metamorphic rock with a banded or foliated structure, typically coarse-grained and consisting mainly of feldspar, quartz, and mica” (Oxford, 2015). Many mountains are formed from the magma floating up off of the melting tectonic plate, which expands the rock above, turning some into volcanoes. The center of the mountain is continuously melted and cooled due to the flux of magma being produced. Because they are made this way, the crustal roots, or the center of the mountains, are highly metamorphosed, having high concentrates of metamorphic rocks such as migmatite (Marshak, 2013). Migmatite is “a rock that is composed of two or more intermingled but distinguishable components, typically a granitic rock within a metamorphic host rock” (Oxford, 2015), and is formed from the partial melting and cooling of different types of rocks. Large batholithic intrusions can also be a product of this type of mountain-building, and can be found under a mountain as a product of the partial melting. The process that creates batholithic intrusions and migmatite rocks is also responsible for the thickening of the continental crust under mountain belts. The constant melting of the subducting tectonic plate produces excess magma that makes the mountain grow while simultaneously adding thickness to the underlying continental crust. Subsequently, as a mountain
However, it is vastly different with mountains formed from subduction. Some are formed from the less dense tectonic plate crushing into the more dense subducting tectonic plate and creating ripples, much like the effect of a soda can or a car. Mountains made this way tend to have many folds and therefore be high in metamorphic rocks such as schist, “a coarse-grained metamorphic rock that consists of layers of different minerals and can be split into thin irregular plates”, and gneiss, “a metamorphic rock with a banded or foliated structure, typically coarse-grained and consisting mainly of feldspar, quartz, and mica” (Oxford, 2015). Many mountains are formed from the magma floating up off of the melting tectonic plate, which expands the rock above, turning some into volcanoes. The center of the mountain is continuously melted and cooled due to the flux of magma being produced. Because they are made this way, the crustal roots, or the center of the mountains, are highly metamorphosed, having high concentrates of metamorphic rocks such as migmatite (Marshak, 2013). Migmatite is “a rock that is composed of two or more intermingled but distinguishable components, typically a granitic rock within a metamorphic host rock” (Oxford, 2015), and is formed from the partial melting and cooling of different types of rocks. Large batholithic intrusions can also be a product of this type of mountain-building, and can be found under a mountain as a product of the partial melting. The process that creates batholithic intrusions and migmatite rocks is also responsible for the thickening of the continental crust under mountain belts. The constant melting of the subducting tectonic plate produces excess magma that makes the mountain grow while simultaneously adding thickness to the underlying continental crust. Subsequently, as a mountain