Processes of Alpine Glacial Erosion in the Sierra Nevada, California, and the Wind River Range, Wyoming

该奖项是根据2009年《美国复苏和再投资法案》(Public Law 111-5)资助的。冰川侵蚀是通过从冰层下粗糙的边缘开采岩石，以及对光滑和抛光冰床的岩石进行磨损来实现的。然而，岩石硬度和岩石破裂程度如何影响采石和磨损过程的量化数据很少。约塞米蒂国家公园花岗岩景观的初步研究表明，冰川景观演变的速度和侵蚀的空间模式受控于岩石中裂隙的间距。这项研究将通过在内华达山脉和怀俄明州的风河山脉进行两个自然实验来提高人们对冰川侵蚀的认识。裂缝间距的变化在约塞米蒂公园的结晶岩体中很常见，而在风河山脉，冰川地形既包括结晶岩性，也包括沉积岩。对沿纵向山谷剖面采集的冰川抛光样品进行宇宙起源的10Be测量将限制冰川侵蚀的深度和冰川消融的历史。野外数据的解释将依赖于一维和二维数值冰川模型。这些模型将模拟纵向河谷剖面的演变，面对测量的基岩侵蚀对比，明确考虑采石和磨损，它们将跟踪基础沉积物含量和粒度分布，允许对照观察到的侵蚀模式和粗沉积物分布进行测试。该项目旨在记录对冰川侵蚀的具体控制。除了少数例外，岩石特性在控制景观中的风格和侵蚀速度方面的重要性在过去没有得到太多关注。研究地点位于冰川特征突出的地区，可以确定岩石性质的影响。这个问题很重要，因为冰川过程塑造了北美大部分现代景观，而气候变化可能会影响冰川侵蚀的程度。约塞米蒂国家公园的研究地点还提供了在外联活动中将科学直接带给公众的机会，这些活动利用了大量游客和与公园工作人员密切的合作关系。

This award is funded under the American Recovery and Reinvestment Act of 2009 (Public Law 111-5).Glacial erosion is accomplished by quarrying of rock from rough edges of the subglacial bed, and abrasion of rock that smoothes and polishes the bed. Yet there is little quantitative data how rock hardness and the degree of rock fracturing govern quarrying and abrasion processes. Preliminary work in the granitic landscape of Yosemite National Park suggests that the pace of glacial landscape evolution and the spatial pattern of erosion are controlled by the spacing of fractures in the rock. This study will improve knowledge of glacial erosion by employing two natural experiments in the Sierra Nevada and the Wind River Range of Wyoming. Variations in fracture spacing are common in the crystalline plutons of Yosemite Park, whereas in the Wind River Range glaciated terrain incudes both crystalline and sedimentary lithologies. Cosmogenic 10Be measurements of glacial polish samples collected along longitudinal valley profiles will constrain the depth of glacial erosion, and the history of deglaciation. Interpretation of field data will rely upon 1D and 2D numerical glacial models. These models will simulate the evolution of the longitudinal valley profile in the face of the measured contrasts in bedrock erodibility, explictly accounting for both quarrying and abrasion, and they will track basal sediment content and size distribution, allowing testing against observed patterns of both erosion and distribution of coarse sediment.This project is designed to document the specific controls on glacial erosion. With few exceptions, the importance of rock properties in controlling styles and rates of erosion in the landscape has not received much attention in the past. The study sites are in areas where glacial features are prominent, and the influence of rock properties can be ascertained. This problem is important because glacial processes have shaped much of the modern landscape of North America, and changing climates may affect the degree of glacial erosion. The study site in Yosemite National Park also provides opportunity to take the science directly to the public in outreach activities that take advantage of the high volume of visitors and strong collaborative ties to park staff.