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首页> 外文期刊>Earth Surface Processes and Landforms: The journal of the British Geomorphological Research Group >The influence of solar-induced thermal stresses on the mechanical weathering of rocks in humid mid-latitudes
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The influence of solar-induced thermal stresses on the mechanical weathering of rocks in humid mid-latitudes

机译：太阳热应力对湿润中纬度岩石机械风化的影响

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The role of solar-induced thermal stresses in the mechanical breakdown of rock in humid-temperate climates has remained relatively unexplored. In contrast, numerous studies have demonstrated that cracks in rocks found in more arid mid-latitude locations exhibit preferred northeast orientations that are interpreted to be a consequence of insolation-related cracking. Here we hypothesize that similar insolation-related mechanisms may be efficacious in humid temperate climates, possibly in conjunction with other mechanical weathering processes. To test this hypothesis, we collected rock and crack data from a total of 310 rocks at a forested field site in North Carolina (99 rocks, 266 cracks) and at forested and unforested field sites in Pennsylvania (211 rocks, 664 cracks) in the eastern United States. We find that overall, measured cracks exhibit statistically preferred strike orientations (47 degrees +/- 16), as well as dip angles (52 degrees +/- 24 degrees), that are similar in most respects to comparable datasets from mid-latitude deserts. There is less variance in strike orientations for larger cracks suggesting that cracks with certain orientations are preferentially propagated through time. We propose that diurnally repeating geometries of solar-related stresses result in propagation of those cracks whose orientations are favorably oriented with respect to those stresses. We hypothesize that the result is an oriented rock heterogeneity that acts as a zone of weakness much like bedding or foliation that can, in turn, be exploited by other weathering processes. Observed crack orientations vary somewhat by location, consistent with this hypothesis given the different latitude and solar exposure of the field sites. Crack densities vary between field sites and are generally higher on north-facing boulder-faces and in forested sites, suggesting that moisture-availability also plays a role in dictating cracking rates. These data provide evidence that solar-induced thermal stresses facilitate mechanical weathering in environments where other processes are also likely at play. Copyright (c) 2015 John Wiley & Sons, Ltd.
机译：在湿温带气候中，太阳热应力在岩石机械破坏中的作用还没有得到充分的研究。相反，大量研究表明，在更干旱的中纬度地区发现的岩石中的裂缝表现出较好的东北方向，这被认为是与日晒有关的裂缝的结果。在这里，我们假设类似的与日晒有关的机制在潮湿的温带气候中可能是有效的，可能与其他机械风化过程结合在一起。为了检验这一假设，我们从北卡罗莱纳州的一个森林野外现场（99个岩石，266个裂缝）和宾夕法尼亚州的森林和非森林野外现场（211个岩石，664个裂缝）收集了总共310个岩石的岩石和裂缝数据。美国东部。我们发现总体上测量的裂纹在统计学上表现出较好的走向（47度+/- 16度）以及倾角（52度+/- 24度），在大多数方面与中纬度沙漠地区的可比较数据集相似。对于较大的裂纹，冲击取向的变化较小，这表明具有某些取向的裂纹优先随时间传播。我们提出，与太阳有关的应力的昼夜重复几何形状会导致裂纹的扩展，这些裂纹的取向相对于这些应力有利。我们假设结果是定向岩石的异质性，它充当弱化区，很像层理或页岩，反过来又可以被其他风化过程所利用。观察到的裂纹取向随位置的不同而有所不同，这与假设的不同，即现场位置的纬度和日照不同。裂缝密度在田间位置之间有所不同，并且在朝北的巨石面上和森林地区通常更高，这表明水分的利用率也决定了裂缝的发生率。这些数据提供的证据表明，在其他过程也可能发挥作用的环境中，太阳热应力会促进机械风化。版权所有（c）2015 John Wiley＆Sons，Ltd.

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