Internal structure of two alpine rock glaciers investigated by quasi-3-D electrical resistivity imaging
Internal structure of two alpine rock glaciers investigated by quasi-3-D electrical resistivity imaging
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DOI：
10.5194/tc-11-841-2017
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发表时间：
2016-07
期刊：
影响因子：
--
通讯作者：
A. Emmert;C. Kneisel
中科院分区：
文献类型：
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作者：
A. Emmert;C. Kneisel
抽象。不同形成过程之间的相互作用反映在岩石冰川的内部结构中。因此，地下条件的探测有助于提高我们对地形发展的认识。对于地下条件的评估，我们提出了一个分析的空间变异性的活动层厚度，地面冰含量和霜冻表地形为两个不同的岩石冰川在瑞士东部阿尔卑斯山的准3-D电阻率成像（ERI）。这种方法可以广泛地绘制地下结构图，并在特定场地的表面和地下特征之间进行空间叠加。在Nair岩石冰川，我们发现了一个逐渐下降的霜表在下坡方向和冰含量的不断减少，以下所观察到的表面地形。这是由于从嵌入的雪堆或从重塑永久冻土层的地下冰补丁再冻结融水形成冰。Uertsch岩石冰川的不均匀分布表明，在不同的时间域上的多个过程参与的发展。代表冻结条件的电阻率值在很大范围内变化，并表明一个连续的形成，其中包括几个进步，过去的冰川覆盖和岩石冰川表面的蠕变过程。结合所观察到的地形，准三维ERI使我们能够界定广泛的和压缩流在附近的地区。出色的数据质量提供了一个良好的耦合电极到地面的卵石材料的研究岩石冰川。结果表明，准三维ERI方法的价值，但建议应用补充地球物理方法解释的结果。
Abstract. Interactions between different formative processes are reflected in the internal structure of rock glaciers. Therefore, the detection of subsurface conditions can help to enhance our understanding of landform development. For an assessment of subsurface conditions, we present an analysis of the spatial variability of active layer thickness, ground ice content and frost table topography for two different rock glaciers in the Eastern Swiss Alps by means of quasi-3-D electrical resistivity imaging (ERI). This approach enables an extensive mapping of subsurface structures and a spatial overlay between site-specific surface and subsurface characteristics. At Nair rock glacier, we discovered a gradual descent of the frost table in a downslope direction and a constant decrease of ice content which follows the observed surface topography. This is attributed to ice formation by refreezing meltwater from an embedded snow bank or from a subsurface ice patch which reshapes the permafrost layer. The heterogeneous ground ice distribution at Uertsch rock glacier indicates that multiple processes on different time domains were involved in the development. Resistivity values which represent frozen conditions vary within a wide range and indicate a successive formation which includes several advances, past glacial overrides and creep processes on the rock glacier surface. In combination with the observed topography, quasi-3-D ERI enables us to delimit areas of extensive and compressive flow in close proximity. Excellent data quality was provided by a good coupling of electrodes to the ground in the pebbly material of the investigated rock glaciers. Results show the value of the quasi-3-D ERI approach but advise the application of complementary geophysical methods for interpreting the results.