文档介绍：prisesthreeprincipallayers:thedense,iron-richcore,themantlemadeofsilicate(硅酸盐)thataresemi-moltenatdepth,andthethin,solid-surfacecrustTherearetwokindsofcrust,rustandanupp,erlightercontinentalcrustfoundoveronlyabout40percentoftheEarth',000millionyearsold,,solidpartofthemantle,totalingabout70to100kilometersinthickness,atpresentappeartoconsistofabout15rigidplates,-moltenlowermantletoproduceallofthemajortopographical(地形学的),:spreadingcontactswhereplatesmoveapart,convergingcontactswhereplatesmovetowardseachother,'scrust,forexample,byvolcaniceruptions(爆发)oflava(火山熔岩)atmid-,tsarift(裂缝)-,thecontinentalblocks,toolighttobedrawndown,continuetofloatandthereforebuckle起(褶皱):Choosecorrectanswerstothequestion:’--,theformationofth