On the basisofthe geomorphology,paleosol,paleoclimate and loessage,majorchangesof the LoessPlateau were studied.There are five majorchangesin the evolution ofthe LoessPlateau in China.Among them,the first,second,third and fourth major changes have taken place since the formation ofthe Loess Plateau,and the fifth majorchange willhappen in 100 years.The firstmajor change,which occurred atabout2.50 M a BP,was a transition from red earth plateau to the Loess Plateau,and reflectsthe climate from the warm-sub-humid to the alteration between cold-and-dry and warm-and-humid.The driving force ofthisfirstmajorchange wasclimate.The second majorchange, which took place atabout1.60 M a BP,was a vitaltransition of the main rivers in this area from non-existence to existence,and represented an importantchange on the Loess Plateau’s neotectonic upliftfrom the slow rising to periodically accelerated rising,and making the river’s erosion go from feeble to strong.The driving force of the second major change is tectonic uplift.The third major change which occurred atabout150 ka,wasa greattransition ofthe Yellow River’sinpouring from a lake outletto a sea outlet.Atthattime,the Yellow Rivercutthe Sanmen Gorge.The transition led to the transformation ofloessmaterialfrom internaltransportation to externaltransportation.The driving force ofthe third majorchange wasrunning watererosion.The fourth one thatoccurred atabout1.1 ka wasa change ofthe LoessPlateau from naturalerosion to erosion accelerated by human influences. Thedriving forceofthefourth majorchangeismainly human activities.Thefifth majorchange,which istheoppositechangeto thefourth one,in which themotivepowerishuman activity,too.
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