关键词: 黄土高原, 古地理演变, 侵蚀历史, 阶段划分, 未来发展

Abstract: Loess Plateau has experienced pre plateau of loess, initial plateau where eroded loess was transported only within the plateau, middle plateau where loess erosion strengthened naturally and eroded loess was transported away partly from the plateau, recent plateau where loess erosion is quickened unnaturally, and future plateau that will be harnessed fast. The pre plateau of loess was consisted of red clay that developed during late Tertiary, when the prevailed climate was warm and semi humid and changed frequently within narrow range. The initial loess plateau developed during 2.5~1.4 Ma B.P., when main rivers did not occur and river erosion did not take place, erosion processes was weak and eroded loess substance did not transport away from the area and moved only from a place to another place within the area. During the period, loess did not deposit beyond the Liupan mountain westward and Wucheng loess covered the eastern area to Liupan mountain; lakes developed, and there was Sangmen large lake in the south of Loess Plateau and some lakes in the middle of Loess Plateau. The climate was more cold and arid than that in pre plateau and it changed with about 100 ka period. Through this period the climate change contained more than 20 stages composing about 10 cycles. The middle loess plateau occured between 1.4 and 0.004 Ma B.P., when lakes became small or disappeared and main rivers appeared. River flow eroded strongly loess and carried loess substance away from the area through Sanmen gorge that was dissected by Yellow River at about 15 ka B.P.. Loess erosion was strengthened in the period, but the process was still much less than deposition process. Loess began to deposit in the areas beyond Liupan mountain westward and all loess strata developed well in the eastern area to Liupan mountain. The change range of climate became greater gradually and reached the greatest in the late period. During the period climate change included about 30 stages composing 15 cycles and the changing period in early stages was 0.04 Ma and 1.0 Ma in late stages. The recent loess plateau has been developed since 4 ka B.P., when the erosion process was sped up. The modern fast erosion of Loess Plateau is not caused naturally by climate change, vegetation change, tectonic uplift and geomorphology development but caused by human being destroying vegetation and this can be tackled by planting trees, conservating vegetation and taking engineering measures, therefore Loess Plateau in the future 200 years will still be a good place for human being living.

Key words: Loess Plateau, evolution of paleogeography, erosion history, stage division, future development