冰川槽谷横剖面定量化研究方法及其影响因素

doi:10.7522/j.issn.1000-0240.2015.0115

摘要/Abstract

摘要： 冰川槽谷(“U”形谷)是冰川与下伏基岩相互作用的结果, 是典型的冰蚀地形, 对其定量化研究是了解冰川作用过程以及冰川槽谷演化过程的重要途径. 二次多项式(y=A+Bx+Cx²)和幂函数(y=ax^b)是定量描述冰川槽谷形态的两种较普遍的方法, 二次多项式可以描述冰川槽谷的整体形态且不需要考虑高程基准面的选择, 但是该方法不能用于槽谷间的比较且其只能较准确地描述接近抛物线的横剖面; 幂函数不但可以反映不同作用过程形成的谷地, 还能在不同横剖面间进行比较, 但幂函数在应用过程过会受到坐标原点选取、对数变化、后期堆积以及横剖面不对称的影响, 其运用过程更加复杂. 此外, 相同的幂函数指数b可能指示不同的槽谷形态, 形态比率FR的引入并与指数b结合起来使对槽谷形态的描述更加全面. 从冰川动力和外部环境方面出发, 影响槽谷形态的因素主要有冰川作用时间、基岩的抗侵蚀能力、岩性的分布以及裂隙、冰量、气候、构造和冰川性质, 后三者对槽谷形态的定量化影响需要进一步进行探讨. 运用不同地区槽谷形态参数所做b~FR图探讨了山地冰川槽谷的发育模式, 发现山地冰川槽谷存在对应于两种不同冰川性质的相反的发育模式, 但是由于岩性、气候等其他因素的影响, 造成了冰川槽谷发育模式有时出现了不对应的情况.

关键词: 冰川槽谷横剖面, 幂函数, 二次多项式, b~FR, 影响因素

Abstract: Glacial trough (U-shaped valley) is the result of the interaction between glacier and its underlying bedrock. It is a typical glacial erosion landform. Quantified description of trough is an important way to understand the process of glaciation and the evolution of the glacial trough. It is also helpful to distinguish the valleys formed by different processes (mainly differentiate V-shaped valleys formed by fluvial process and U-shaped valleys formed by glaciation). The quadratic equation (y=A+Bx+Cx²) and the power function (y=ax^b) are two models widely used to describe the morphology of glacial trough cross-section, of which each has some advantages and limitations. The quadratic equation can describe the overall form of the glacial trough in one function irrespective the altitude-datum, but it can't be used for form comparison and it can just describe the forms close to parabolic. The power function is used more widely than the former, because of that it cannot only reflect trough formed by different processes, but also be used for form comparison. However, it will generate bias due to selecting coordinate origin, logarithmic transformation, post-glacial deposition and the asymmetry of cross-profile, which lead to more complexity in application. In addition, considering the same b value may indicate different valley forms, introduction of a form ratio (FR) is of great importance, and thus FR and b together can comprehensively describe the valley morphology. The major factors influencing the valley morphology include glaciation time, erosion resistance (mainly, rock mass strength (RMS)), distribution and fracture of bedrock, ice volume, climate, tectonic and the properties of glacier. The quantitative impacts of the former three factors on glacial trough are very explicit, whereas the latter three ones need to discuss further. Based on morphological parameters in different regions, a b~FR diagram is drawn to further study the development of mountain glaciers. It is found that the glacial troughs exist roughly two opposite types of cross-profile, corresponding to two different glacier properties. However, sometimes the corresponding relationship does not work due to the impacts of other factors, such as bedrock property, climate, etc.

Key words: glacial trough profile, power function, quadratic equation, b~FR, influential factors

中图分类号:

P931.4

姚盼, 王杰. 冰川槽谷横剖面定量化研究方法及其影响因素[J]. 冰川冻土, 2015, 37(4): 1028-1040.

YAO Pan, WANG Jie. A review of the quantified analysis methods of glacial trough and its influential factors[J]. JOURNAL OF GLACIOLOGY AND GEOCRYOLOGY, 2015, 37(4): 1028-1040.

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