▁of ▁rocks ▁has ▁been ▁depos ited , ▁the ▁rock ▁units ▁can ▁be ▁de formed ▁and / or ▁met am orph osed . ▁De formation ▁typically ▁occurs ▁as ▁a ▁result ▁of ▁horizontal ▁short ening , ▁horizontal ▁extension , ▁or ▁side - to - side ▁( st rike - s lip ) ▁motion . ▁These ▁struct ural ▁reg imes ▁broad ly ▁relate ▁to ▁conver gent ▁boundaries , ▁diver gent ▁boundaries , ▁and ▁transform ▁boundaries , ▁respectively , ▁between ▁t ect onic ▁pl ates . ▁ ▁Historical ▁perspective ▁ ▁Earth ▁is ▁estimated ▁to ▁have ▁formed ▁ 4 . 5 4   b ill ion ▁years ▁ago ▁from ▁the ▁solar ▁ne b ula , ▁along ▁with ▁the ▁Sun ▁and ▁other ▁plan ets . ▁The ▁moon ▁formed ▁roughly ▁ 2 0   mill ion ▁years ▁later . ▁Initial ly ▁mol ten , ▁the ▁outer ▁layer ▁of ▁the ▁Earth ▁co o led , ▁resulting ▁in ▁the ▁solid ▁cr ust . ▁Out g ass ing ▁and ▁vol can ic ▁activity ▁produced ▁the ▁prim ord ial ▁atmosphere . ▁Cond ens ing ▁water ▁v apor , ▁most ▁or ▁all ▁of ▁which ▁came ▁from ▁ice ▁delivered ▁by ▁com ets , ▁produced ▁the ▁o ce ans ▁and ▁other ▁water ▁sources . ▁The ▁highly ▁ener get ic ▁chem istry ▁is ▁believed ▁to ▁have ▁produced ▁a ▁self - rep lic ating ▁mole c ule ▁around ▁ 4   b ill ion ▁years ▁ago . ▁ ▁Cont in ents ▁formed , ▁then ▁broke ▁up ▁and ▁reform ed ▁as ▁the ▁surface ▁of ▁Earth ▁res h aped ▁over ▁hundreds