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

要了解山坡的长期演变，需要了解基岩如何转化为移动的风化层，以及风化层如何沿山坡向下迁移。 在许多情况下，基岩转化为风化层的速度不仅控制着景观的下降速度，还控制着景观的形状。 虽然风化层产生的概念模型已经建立，但支持这些概念模型所需的经验观测却很少。 对风化层形成过程的机械论理解仍然是一个推测问题。 同样，很少有实证研究提供了足够的约束过程为基础的理解风化层运输。 一个首要的问题，是什么样的风化层的生产率对风化层厚度的依赖？反映了主导范式，其中风化层厚度是控制参数。 显然，厚度是其他变量的代表，如水接触时间和化学饱和状态，以及冻融循环频率。 机械和化学过程的相互作用，产生和运输风化层将探讨在一个简单的景观：在科罗拉多前山脉的高山高表面。 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状态的地貌，风化层很薄，容易接近，是从花岗岩类岩石中产生的，容易表征的霜冻过程预计将占主导地位的机械过程。 所使用的方法是记录岩石和风化层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;所有强烈约束景观演化的概念和数值模型。 目前的化学和物理过程将监测土壤水采样器，水分探头，温度串，冻胀传感器和应变计。 采样点将沿抛物线稳定状态山坡的横断面沿着排列。 将详细记录地形（使用激光测高仪）和积雪，并调查风化层厚度和化学演变的变化。 长期的风化生产率和它的运动下坡将记录使用宇宙成因的10 Be在基岩和风化剖面的浓度，分别。 现有的风化层生产模型将通过纳入本研究中记录的特定过程进行改进。 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，水文和化学过程。 该模型将作为对从实地数据中得出的过程理解的一种测试。 这项工作将用于在CU教学，推广到公众，并在研究中培养研究生和本科生。 一名研究生和两名本科生将接触到表面过程的研究，包括激光测高分析，宇宙成因核素测年，现场监测和数值模拟。 由于该网站是接近CU，讲座，实验室练习和实地考察将是可能的。 数据将通过PI的网站和尼沃特岭LTER的网站提供。 PI致力于将他们的科学带给更广泛的公众。 景观演变的模拟正在共享（见http：//instaar.colorado.edu/rmnp上冰川和托星罗棋布的山脊的模拟样本）。 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。

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.