Quasi‐Steady Evolution of Hillslopes in Layered Landscapes: An Analytic Approach
Quasi‐Steady Evolution of Hillslopes in Layered Landscapes: An Analytic Approach
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DOI：
10.1002/2017jf004466
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发表时间：
2018-01
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影响因子：
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通讯作者：
R. Glade;R. Anderson
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文献类型：
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作者：
R. Glade;R. Anderson
在层状沉积岩或火成岩中形成的景观在地球上很常见，在其他行星上也是如此。拱背、裸露岩脉、陡崖和台地等地貌特征表现出与倾斜、垂直或水平方向的易蚀岩石相邻的抗蚀岩石层。在易侵蚀岩石中发育的山坡通常具有陡峭的线性至凹形斜坡或“斜坡”的特征，斜坡上覆盖着来自抗蚀层的材料，通常为大块。先前对拱背的研究表明，随着时间的推移，块体和下伏软岩的风化和搬运之间的反馈可以产生缓解，并导致在没有钻孔过程的情况下形成上凹的斜坡剖面。在这里，我们采用了一种分析方法，通过数值模拟和现场数据，来描述这种岩石山坡的准稳态行为的全谱抵抗层倾角。我们开始与一个简单的几何分析，结构倾角与侵蚀率。然后，我们探索的机制，我们的数值模型的hogback演变自组织，以满足这些几何期望，包括调整土壤深度，侵蚀速率，和块速度沿着坡道。解析解涉及容易测量的现场量，如坡道长度，坡度，块体大小，和抵抗层倾角的局部切口率，块体速度，块风化率。这些方程为探索分层景观的演变提供了一个框架，并指出了我们需要更深入了解的过程，以预测它们随时间的演变。
Landscapes developed in layered sedimentary or igneous rocks are common on Earth, as well as on other planets. Features such as hogbacks, exposed dikes, escarpments, and mesas exhibit resistant rock layers adjoining more erodible rock in tilted, vertical, or horizontal orientations. Hillslopes developed in the erodible rock are typically characterized by steep, linear‐to‐concave slopes or “ramps” mantled with material derived from the resistant layers, often in the form of large blocks. Previous work on hogbacks has shown that feedbacks between weathering and transport of the blocks and underlying soft rock can create relief over time and lead to the development of concave‐up slope profiles in the absence of rilling processes. Here we employ an analytic approach, informed by numerical modeling and field data, to describe the quasi‐steady state behavior of such rocky hillslopes for the full spectrum of resistant layer dip angles. We begin with a simple geometric analysis that relates structural dip to erosion rates. We then explore the mechanisms by which our numerical model of hogback evolution self‐organizes to meet these geometric expectations, including adjustment of soil depth, erosion rates, and block velocities along the ramp. Analytical solutions relate easily measurable field quantities such as ramp length, slope, block size, and resistant layer dip angle to local incision rate, block velocity, and block weathering rate. These equations provide a framework for exploring the evolution of layered landscapes and pinpoint the processes for which we require a more thorough understanding to predict their evolution over time.