Using compaction and cementation explain why sedimentary rocks are not just a loose pile of sand and rocks.​

Compaction and Cementation They are compacted, reducing the available pore space and expelling much of the pore-water. Dissolved minerals in the ground water precipitate (crystallize) from water in the pore spaces forming mineral crusts on the sedimentary grains, gradually cementing the sediments, thus forming a rock.

it takes hundreds of years to become stable.

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in 1859, charles darwin set out his theory of evolution by natural selection as an explanation for adaptation and speciation. he defined natural selection as the "principle by which each slight variation [of a trait], if useful, is preserved".