History of sea arches and remnant stacks of La Jolla, California, and their bearing on similar features elsewhere
History of sea arches and remnant stacks of La Jolla, California, and their bearing on similar features elsewhere
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加利福尼亚州拉霍亚海拱和残存岩堆的历史及其对其他地方类似特征的影响
DOI：
10.1016/0025-3227(83)90094-4
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发表时间：
1983
期刊：
影响因子：
2.9
通讯作者：
G. G. Kuhn
中科院分区：
文献类型：
--
作者：
F. P. Shepard;G. G. Kuhn
在过去，很少有人试图描述和解释在世界沿岸发现的各种类型的海拱。由于我们有一些很好的拱门例子，在南加州拉霍亚角地区的老照片中可以看到，我们希望把这些拱门的历史作为理论研究其他地方发现的拱门的模型。利用过去一百年的优秀照片汇编，我们已经能够对这些拉霍亚拱门做出合理的解释，并发现它们的形成部分是由于最近的块状断层隆起导致不规则海岸线暴露的结果。然而，每种情况的发展都有不同的原因，而不是任何一个过程，如约翰逊（1925年，1938年）对几个拱门提出的在突出点的两面切割。拉霍亚地区唯一完好无损的拱门显然是一系列海岸洞穴西端被淹没的结果，由于陆地和海洋侵蚀，洞穴在其头部相交。19世纪早期的南风大风暴可能会导致出现的土坝被削弱（Dana, 1969），在其他地方，在软质材料的硬层下切割的涌浪通道在拱门的形成中发挥了作用，但只指出了一个点两侧侵蚀的例子。将我们从拉霍亚角获得的资料与其他地区的拱地相比较，我们发现有几个例子表明，突出的陆地点表明最近发生了地壳运动，拱地发育得与拉霍亚的拱地相似，但我们对它们知之甚少。我们同意约翰逊的观点，即许多拱是波浪侵蚀突出点两侧的结果。在浪涌通道中，电流穿过由更强的抵抗地层覆盖的薄弱层，可能形成了同样数量的浪涌通道。虽然我们没有很好的例子，但我们确信一些拱很大程度上是由于溶洞两端暴露的结果。
In the past there has been little attempt made to describe and explain the various types of sea arches that are found along the coasts of the world. Since we have some good examples of arches, shown in old photographs around the Point La Jolla area in southern California, it is desirable to consider the history of these arches as a model for a theoretical study of arches found elsewhere. Using the excellent compilation of photographs of the previous one hundred years, we have been able to make reasonable explanations for these La Jolla arches and have found that they were formed partly as the result of exposure of an irregular coastline due to block-fault uplift of quite recent date. However, a somewhat different cause has accounted for the development of each case, as opposed to any one process such as the cutting on two sides of a projecting point, as suggested by Johnson (1925, 1938) for several arches. The only arch still intact in the La Jolla area is apparently the result of the submergence of the west end of a series of coastal caves where an embayment due to land and sea erosion intersected the cave at its head. Large southerly storms in the early 19th century may account for the undercutting of emergent hogbacks (Dana, 1969), and elsewhere surge channels cutting under hard layers in soft material have played a role in the formation of arches, but only one example of erosion on two sides of a point is indicated.Comparing our information from Point La Jolla to arches in other areas we find that there are several examples where projecting points of land indicate recent diastrophism and arches are developed which are similar to those at La Jolla, but we know little about them. We agree with Johnson that many arches have been the result of wave erosion on the two sides of projecting points. Probably an equal number have formed as the result of surge channels where currents have penetrated weak layers capped by more resistant formations. Although we have no good examples, we feel sure that some arches are largely the result of exposure of both ends of solution caverns.