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古水文学及其研究方法 总被引：4，自引：0，他引：4
古水文学是近年来发展起来的新学科。本世纪五十年代以来出版的地学教科书中,很少有古水文学(Palaeohydrology)一词,1982年修订的牛津词典中已有古气候学(Palaeoclimatology)、古生态学(Palaeoecology)和古地貌学(Palaeomorphology),但仍未见古水文学。在英文文献中,最早使用此名词的是Leopold和Miller[1]。 相似文献
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曹银真 《中国地理科学(英文版)》1991,1(3):262-271
In the river systems, the environmental change always undergoes a process from quantitative to qualitative change. The upper limit of the qualitative change is called threshold. When the process reaches or goes beyond the limit, the original event series will be replaced by the other event series. Investigations show that the evolution of the Huanghe River alluvial fan and delta has also under gone a process from quantitative to qualitative change. The geometric forms in each process are roughly the same. This threshold of the geometric forms not only provides us a quantitative index for plotting the periodicity of the alluvial fan and delta, but also is of importance for estimation of the trend of natural environmental change.It is shown that there are three periodic alluvial fans of the Huanghe River since the middle Holocene and four periodic delta since 1855 A.D., the thresholds of their geometric forms are from 0.93 to 0.94 and from 1.2 to 1.21 respectively.The changing trend in the past and the na 相似文献
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实际上,地球的任何地方都可以发现第四纪堆积物。在山区,往往覆盖着第四纪残积物,而在斜坡、阶地和谷底,多为崩坍物、滑坍物以及山麓堆积物、冲积砾石层或冰碛物所覆盖。在平原地区,第四纪沉积物常常覆盖了所有地面,而且为海底输送了大量物质。就地质史而论,在短暂的第四纪期间,海陆轮廓变化不大。因此,在现代大陆上,第四纪堆积物占绝对优势。 相似文献
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黄土地区梁峁坡的坡地特征与土壤侵蚀 总被引：14，自引：0，他引：14
本文指出黄土地区梁峁坡的坡角主要分布在14°—28°之间,特征坡角的上限相当于黄土的内摩擦角,下限相当于内摩擦角的0.45倍。黄土地区的坡地形态可分为直形坡、凸形坡、凹形坡、复合形坡和阶梯形坡等五种类型。土壤侵蚀主要受坡地形态和坡度的控制,侵蚀量随着坡度的增大而增加,坡度大于15°时,侵蚀量突增,坡面冲刷加剧,26°达极大值,此后冲刷作用减弱,重力侵蚀逐渐显著,至45°侵蚀达到最大值,以后又趋减弱。 相似文献
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