How does underlying geology affect coastline change? An initial modeling investigation
How does underlying geology affect coastline change? An initial modeling investigation
复制标题
底层地质如何影响海岸线变化？
DOI：
10.1029/2005jf000340
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发表时间：
2006
影响因子：
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通讯作者：
A. Ashton
中科院分区：
文献类型：
--
作者：
Lisa M. Valvo;A. B. Murray;A. Ashton
[1] 概念地质框架模型预测，位于较弱或非常细粒度岩性下方的海岸区域比邻近的、更具抵抗力或较粗粒度的岩性部分向陆地退缩得更快。这些看似常识性的预测似乎与异质岩性下的沙质海岸线仍然相当光滑的观察结果不一致。我们开发了一个数值模型来探索岸面岩性效应与大于年和公里尺度的沿岸输送过程之间的相互作用。海岸线凹痕或海岸部分稍微向陆地倾斜的部分，往往会在模型中形成，其中海岸面风化更快或由更细粒的材料组成。然而，沿海运输往往会填充这些凹痕，减缓那里的风化速度，同时增加优先清除流动沉积物的邻近区域的风化速度。从长远来看，这会导致沿岸统一的撤退率。模型中存在反映异质地质框架的微妙海岸线波动，但其幅度达到稳定状态而不是随时间增加。成分的异质性决定了海岸的形态，而风化速率的异质性则控制着岸面沉积物的厚度。因此，如果岩石的颗粒较细，则由较硬（不易腐蚀）的岩石组成的部分可能会形成压痕。
[1] Conceptual geologic framework models predict that areas of the coast underlain by a weak or very fine grained lithology retreat landward faster than adjacent, more resistant or coarser-grained segments. These apparently commonsense predictions seem inconsistent with observations that sandy coastlines underlain by heterogeneous lithology remain fairly smooth. We have developed a numerical model to explore the interaction between shoreface lithology effects and alongshore transport processes on scales greater than years and kilometers. Shoreline indentations, or sections of the coast that are slightly landward of adjacent sections, tend to form in the model where the shoreface weathers more rapidly or is composed of finer-grained material. However, alongshore transport tends to fill in these indentations, slowing the weathering rates there while increasing them in adjacent areas where mobile sediment is preferentially removed. Over the long term this leads to an alongshore uniform retreat rate. Subtle shoreline undulations reflecting the heterogeneous geologic framework exist in the model, but their amplitude reaches a steady state rather than increasing with time. Compositional heterogeneities determine the morphology of the coast while weathering rate heterogeneities control the thickness of sediment on the shoreface. Thus indentations can form in sections composed of harder (less erodible) rocks if they are finer grained.