Collaborative Research: Toward an Erosion Rule for Glacial Quarrying: Modeling and Measurements

对冰川采石侵蚀规律的合作研究：建模和测量Denis Cohen和Neal Iverson爱荷华州州立大学Thomas Hooyer威斯康星州地质调查局摘要冰川对岩石的侵蚀导致了壮观的地貌，如角峰和U形山谷，也可以对山区岩石隆起的速率以及风化速率、CO2产生和气候的相关变化产生巨大影响。采石，冰川使下面的岩石破裂并移走由此产生的岩石碎片的过程，被认为是冰川侵蚀最重要的过程。然而，目前还没有一个全面的采石定量模型，将冰川学变量（如滑动速度和基底水压）与采石率完全联系起来。因此，冰川侵蚀模型的结果适用于广泛的地区（例如，通过这项研究，将构建一个通用的采石理论模型，然后通过对冰川下基岩裂缝增长的实时测量和对最近因冰川退缩而暴露的基岩裂缝模式的测绘进行测试。冰流将在由倾斜台阶组成的基岩上进行建模，方法是将这些台阶背风处空腔中的水压与稳态和瞬态情况下的滑动速度和空腔尺寸完全耦合。结果将用于计算岩石床中的应力分布以及随之而来的裂缝速度和路径，因为它们缓慢延伸并隔离可以被冰川轻易提取的岩石块。将在挪威北方的一个温带冰川Engelzen的210米滑动冰下安装倾斜的岩石台阶，对该模型进行测试，Svartisen冰川观测站为人类提供了进入冰川-岩石界面的机会。台阶中裂缝生长产生的声波将用于确定冰川学变量与台阶中裂缝生长速度和路径之间的关系。为了进一步测试采石模型的各个方面，将在阿尔伯塔卡斯特加德冰川前的阶梯状基岩上绘制前冰下洞穴的大小以及相关冰川引起的裂缝的分布和方向，并与模型预测进行比较。这项工作的总体结果将是一个采石规则，可以作为大规模冰川侵蚀模型的基础。

Collaborative research toward an erosion rule for glacial quarrying: Modeling and measurementsDenis Cohen and Neal Iverson EAR-0229692 Iowa State UniversityThomas Hooyer EAR-0229526 Wisconsin Geological SurveyAbstractErosion of rock by glaciers results in spectacular landforms, such as horn peaks and U-shaped valleys, and can also have a dramatic effect on rates of rock uplift in mountain belts and associated changes in weathering rates, CO2 production, and climate. Quarrying, the process in which glaciers crack underlying rock and remove resultant rock fragments is thought to be the most important process of glacial erosion. There is at present, however, no comprehensive quantitative model of quarrying that fully links glaciological variables, such as sliding speed and basal water pressure, to quarrying rate. Thus, results of models of glacial erosion applied over broad areas (e.g., mountain belts) and long periods (10^5-10^6 years) are uncertain, both quantitatively and conceptually.With this research, a versatile theoretical model of quarrying will be constructed and then tested, both with real-time measurements of crack growth in bedrock beneath a glacier and with mapping of crack patterns in bedrock recently exposed by glacier retreat. Ice flow will be modeled over bedrock consisting of inclined steps by fully coupling water pressure in cavities in the lee of these steps with sliding speed and cavity size for both steady and transient cases. Results will be used to calculate the stress distribution in the rock bed and the consequent speeds and paths of cracks, as they slowly extend and isolate rock blocks that can be extracted easily by the glacier. The model will be tested by installing inclined rock steps beneath 210 m of sliding ice at Engabreen, a temperate glacier in northern Norway, where the Svartisen Glaciological Observatory provides human access to the glacier-rock interface. Sound waves generated by growth of cracks in the steps will be used to determine the relation between glaciological variables and crack-growth speeds and paths in the steps. To further test aspects of the quarrying model, sizes of former subglacial cavities and distributions and orientations of associated glacially-induced cracks will be mapped on stepped bedrock in front of Castelguard Glacier, Alberta, and compared with model predictions. The overall result of this work will be a quarrying rule that can serve as the basis for large-scale models of glacial erosion.