Metamorphic rocks begin as one kind of absent and—with pressure, heat, and time—gradually readjust into a new form of rock.
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Metamorphic rock Isua
Metamorphic rock, estimated to be together old together 3.8 exchange rate years, situated near Isua in ~ Qorqut Sound, Greenland.
Photograph by James L. Amos
The ax “metamorphosis” is most frequently used in recommendation to the process of a caterpillar changing into a butterfly. However, words “metamorphosis” is a wide term that shows a change from one point to another. Even rocks, a seemingly consistent substance, can adjust into a new kind of rock. Rocks the undergo a adjust to kind a new rock are described as metamorphic rocks.
In the absent cycle, there room three different varieties of rocks: sedimentary, igneous, and metamorphic. Sedimentary and igneous rocks started as something various other than rock. Sedimentary rocks were originally sediments, which to be compacted under high pressure. Igneous rocks formed when fluid magma or lava—magma that has arised onto the surface ar of the Earth—cooled and also hardened. A metamorphic rock, top top the various other hand, started as a rock—either a sedimentary, igneous, or even a different sort the metamorphic rock. Then, due to various conditions within the Earth, the existing rock was adjusted into a new kind that metamorphic rock.
The conditions required to type a metamorphic rock are an extremely specific. The currently rock must be exposed to high heat, high pressure, or come a hot, mineral-rich fluid. Usually, all 3 of these situations are met. These problems are most often uncovered either deep in Earth’s crust or in ~ plate boundaries where tectonic bowl collide. In order to develop metamorphic rock, that is critical that the currently rock stay solid and also not melt. If over there is too much warm or pressure, the rock will certainly melt and also become magma. This will an outcome in the formation of one igneous rock, no a metamorphic rock.
Consider just how granite changes form. Granite is an igneous rock that develops when magma cools fairly slowly underground. The is commonly composed generally of the minerals quartz, feldspar, and also mica. Once granite is based on intense heat and pressure, it changes into a metamorphic rock called gneiss.
Slate is an additional common metamorphic rock that forms from shale. Limestone, a sedimentary rock, will adjust into the metamorphic absent marble if the right problems are met.
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Although metamorphic rocks typically form deep in the planet’s crust, castle are regularly exposed on the surface of the Earth. This happens due to geologic uplift and the erosion the the rock and also soil above them. In ~ the surface, metamorphic rocks will certainly be exposed come weathering processes and also may breakdown into sediment. This sediments could then it is in compressed to kind sedimentary rocks, i beg your pardon would start the entire cycle anew.