The Linkage of Chemical and Mechanical Processes in the Evolution of High Surfaces of the Front Range Crest, Colorado

科罗拉多州前岭山顶高地表面演化过程中化学和机械过程的联系

• 批准号: 0519060
• 负责人: Suzanne Anderson
• 金额: --
• 依托单位: University of Colorado at Boulder
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-09-15 至 2008-08-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0519060&HistoricalAwards=false
• 关键词: Linkage; Chemical; Mechanical; Processes; Evolution

An understanding of the long-term evolution of hillslopes requires knowledge of how bedrock is converted to mobile regolith, and how regolith is transported downslope. In many cases, the rate of conversion of bedrock to regolith controls not only the rate of lowering of the landscape, but its shape as well. While conceptual models of regolith production are well established, the empirical observations needed to support these conceptual models are few. A mechanistic understanding of the process of regolith formation remains a matter of conjecture. Similarly, few empirical studies provide sufficient constraint on a process-based understanding of regolith transport. An overarching question, What is the dependence of regolith production rate on regolith thickness? reflects the reigning paradigm, in which regolith thickness is the controlling parameter. Clearly, thickness is a proxy for other variables, such as water contact time and chemical saturation state, and freeze-thaw cycle frequency. The interaction of mechanical and chemical processes that produce and transport regolith will be explored in a simple landscape: the alpine high surfaces in the Front Range of Colorado. These high surfaces are an ideal laboratory because their parabolic shape implies that they are steady state landforms, the regolith is thin and accessible and is generated from granitoid rock, and easily characterized frost processes are expected to dominate the mechanical processes. The approach used is to document the chemical development and mechanical properties in the rock and regolith, paying particular attention to the interface between these materials. Modern and several-thousand year process rates will be documented; all strongly constrain conceptual and numerical models of landscape evolution. Current chemical and physical processes will be monitored with soil water samplers, moisture probes, temperature strings, frost-heave sensors, and strain gauges. Sampling sites will be arrayed along a transect down a parabolic, steady state hillslope. Topography (using laser altimetry) and snow cover will be documented in detail, and variations in regolith thickness and chemical evolution surveyed. Long-term rates of regolith production and its motion down slope will be documented using the concentration of cosmogenic 10Be in bedrock and regolith profiles, respectively. An existing model of regolith production will be refined by incorporation of the specific processes documented in this study. The development of this model will integrate the field measurements outlined, and the information gleaned from modern and long-term process data. This will require attention to thermal, hydrologic, and chemical processes. The model will serve as a test of the process understanding developed from the field data.Broader Impacts. This work will be used in teaching at CU, outreach to the public, and training graduate and undergraduate students in research. One graduate student and 2 undergraduate students will be exposed to surface processes research, including analysis of laser altimetry, cosmogenic nuclide dating, field monitoring, and numerical modeling. As the site is close to CU, lectures, lab exercises and field trips will be possible. Data will be made available through the web sites of the PIs and through that of the Niwot Ridge LTER. The PIs are committed to taking their science to the broader public. Simulations of landscape evolution are being shared (see sample simulations of both glaciers and tor-dotted ridges at http://instaar.colorado.edu/rmnp). The model of alpine hillslopes produced will add understanding of the interactions of chemical and physical processes in eroding landscapes.

要了解山坡的长期演变，需要了解基岩如何转化为可流动的复盖层，以及复盖层是如何向下输送的。在许多情况下，基岩向风化层的转化速度不仅控制着地貌的下降速度，而且还控制着它的形状。虽然风化层生产的概念模型已经建立得很好，但支持这些概念模型所需的经验观察却很少。对风化层形成过程的机械理解仍然是一种猜测。同样，很少有实证研究对基于过程的风化层迁移的理解提供足够的限制。一个最重要的问题是，风化速率与风化厚度的关系如何？反映了以风化层厚度为控制参数的统治范式。显然，厚度可以替代其他变量，如水接触时间、化学饱和状态和冻融循环频率。我们将在一个简单的景观中探索产生和运输浮冰的机械和化学过程的相互作用：科罗拉多州前缘山脉的高山高地。这些高表面是一个理想的实验室，因为它们的抛物线形状意味着它们是稳定的地貌，风化层很薄，可以接触到，并且是由花岗岩类岩石产生的，而且容易表征的霜冻过程预计将主导机械过程。所采用的方法是记录岩石和风化层中的化学发展和机械性能，特别注意这些材料之间的界面。现代和几千年的过程速率将被记录下来；所有这些都强烈限制了景观演变的概念和数字模型。目前的化学和物理过程将用土壤水采样器、湿度探头、温度串、冻胀传感器和应变计进行监测。采样点将沿着沿抛物线稳定状态的山坡下的横断面排列。将详细记录地形(使用激光测高)和积雪，并调查风土层厚度和化学演化的变化。将分别使用基岩和风化岩剖面中的宇宙成因10Be浓度来记录风化岩的长期产生率及其向下移动的速度。现有的风化岩层生产模型将通过结合本研究中记录的特定工艺进行改进。该模型的开发将整合概述的现场测量以及从现代和长期过程数据中收集的信息。这将需要注意热力、水文和化学过程。该模型将作为对从现场数据发展而来的过程理解的测试。这项工作将用于CU的教学，面向公众的推广，以及对研究生和本科生的研究培训。一名研究生和两名本科生将学习表面过程研究，包括激光测高分析、宇宙核素测年、野外监测和数值模拟。由于该地点靠近哥伦比亚大学，因此可以进行讲座、实验室练习和实地考察。数据将通过私人投资机构的网站和尼沃特岭长期热核研究中心的网站提供。私人情报员致力于将他们的科学带给更广泛的公众。地貌演变的模拟正在共享(参见http://instaar.colorado.edu/rmnp).上的冰川和圆点状山脊的模拟样本制作的高山山坡模型将增加对侵蚀景观中化学和物理过程相互作用的理解。