Rock formed at or near the surface of the Earth or other planetary body from compacted sediments. Such sediments consist of solid rock or mineral fragments transported and deposited by wind, water, gravity, or ice; precipitated by chemical reactions; or secreted by organisms; accumulated as layers in loose, unconsolidated form.
Sedimentary rocks are often deposited in layers (strata) and hardened by natural cements, and include shale, sandstone, and limestone. The other main types of rock are metamorphic and igneous.
Related category GEOLOGY AND PLANETARY SCIENCE
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