page_title: Formation of rocks
hierarchical_section_title: Formation of rocks
caption_attribution_description: English: Two-parts stoneРусский: Камень из двух половинок
context_page_description: The three main ways terrestrial rocks are formed:
  Sedimentary rocks are formed through the gradual accumulation of sediments: for example, sand on a beach or mud on a river bed. As the sediments are buried they get compacted as more and more material is deposited on top. Eventually the sediments will become so dense that they would essentially form a rock. This process is known as lithification.
  Igneous rocks are rocks which have crystallised from a melt or magma. The melt is made up of various components of pre-existing rocks which have been subjected to melting either at subduction zones or within the Earth's mantle. The melt is hot and so passes upward through cooler country rock. As it moves, it cools and various rock types will form through a process known as fractional crystallisation. Igneous rocks can be seen at mid ocean ridges, areas of island arc volcanism or in intra-plate hotspots.
  Metamorphic rocks are rocks which once existed as igneous or sedimentary rocks but have been subjected to varying degrees of pressure and heat within the Earth's crust.
context_section_description: The three main ways terrestrial rocks are formed:
  Sedimentary rocks are formed through the gradual accumulation of sediments: for example, sand on a beach or mud on a river bed. As the sediments are buried they get   compacted as more and more material is deposited on top. Eventually the sediments will become so dense that they would  essentially form a rock. This process is known as lithification.
  Igneous rocks are rocks which have crystallised from a melt or magma. The melt is made up of various components of pre-existing rocks which have been subjected to melting either at subduction zones or within the Earth's mantle. The melt is hot and so passes upward through cooler country rock. As it moves, it cools and various rock types will form through a process known as fractional crystallisation. Igneous rocks can be seen at mid ocean ridges, areas of island arc volcanism or in intra-plate hotspots.
  Metamorphic rocks are rocks which once existed as igneous or sedimentary rocks but have been subjected to varying degrees of pressure and heat within the Earth's crust. The processes involved will change the composition and fabric of the rock and their original nature is often hard to distinguish. Metamorphic rocks are typically found in areas of mountain building.
  Rock can also form in the absence of a substantial pressure gradient as material that condensed from a protoplanetary disk, without ever undergoing any transformations in the interior of a large object such as a planet or moon.  Astrophysicists classify this as a fourth type of rock:  Primitive rock.  Primitive rock is common in asteroids and meteorites.
caption: Stone
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