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

合作研究：寻找冰川采石的侵蚀规则：建模和测量

• 批准号: 0229526
• 负责人: Thomas Hooyer
• 金额: --
• 依托单位: University of Wisconsin-Extension
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2003
• 资助国家: 美国
• 起止时间: 2003-03-01 至 2006-02-28
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0229526&HistoricalAwards=false
• 关键词: Collaborative; Research; Toward; Erosion; Rule

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.

对冰川采石侵蚀规律的合作研究：建模和测量Denis Cohen和Neal Iverson Ear-0229692爱荷华州立大学Thomas Hooyer Ear-0229526威斯康星州地质调查局摘要冰川侵蚀岩石会导致壮观的地貌，如角峰和U形山谷，还可能对山区岩石抬升速率以及相关风化速率、二氧化碳产生和气候变化产生巨大影响。采石被认为是冰川侵蚀最重要的过程，也就是冰川裂开下面的岩石并清除由此产生的岩石碎片的过程。然而，目前还没有一个全面的定量采石模型来完全将冰川变量，如滑动速度和基本水压，与采石率联系起来。因此，冰川侵蚀模型在大范围(如山脉地带)和长周期(10^5-10^6年)上的应用结果在数量和概念上都是不确定的。随着这项研究，将建立一个通用的采石场理论模型，然后进行检验，既有冰川下基岩裂缝扩展的实时测量，也有最近冰川消退暴露的基岩裂缝模式图。冰流将在由倾斜台阶组成的基岩上模拟，在稳态和瞬变情况下，这些台阶背风处的空穴中的水压力与滑动速度和空穴大小完全耦合。结果将被用来计算岩床中的应力分布以及随后的裂缝速度和路径，因为它们会慢慢延伸并隔离可以很容易被冰川提取的岩石块。该模型将通过在挪威北部温带冰川Engabreen的210米滑动冰下安装倾斜的岩石台阶进行测试，斯瓦蒂森冰川天文台为人类提供进入冰川-岩石界面的通道。台阶中裂纹扩展产生的声波将被用来确定冰川学变量与台阶中裂纹扩展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，将在艾伯塔省卡斯特尔加德冰川前的台阶基岩上绘制以前冰下洞穴的大小以及相关冰川诱发裂缝的分布和方向图，并与模型预测进行比较。这项工作的总体结果将是一条采石规则，可以作为大规模冰川侵蚀模型的基础。