Insular Erosion, Isostasy, and Subsidence
Insular Erosion, Isostasy, and Subsidence
复制标题
岛礁侵蚀、均衡和沉降
作者：
H. W. Menard
有机礁和海岸侵蚀记录了海平面与岛屿的交汇情况。从这份记录中，有可能重建岛屿以及相邻深海海底（包括板块内部隆起）的垂直运动历史。从珊瑚厚度判断，有堡礁的岛屿下沉，就好像它们位于热年轻地壳上一样，无论其实际年龄如何。无礁岛屿直到被侵蚀截断才下沉。显然，热沉降被因侵蚀产生的均衡隆升所平衡。堡礁防止了环绕火山的波浪侵蚀，并截留了河流侵蚀的产物，从而消除了均衡隆升。岛架最初以每百万年0.6到1.7公里的速度加宽；该速度随时间降低。因此，岛屿的沉降取决于岛屿的大小和礁的存在，并且它可能并不总是与周围的大洋地壳相同。
Organic reefs and shore erosion record the intersection of sea level with islands. From this record it is possible to reconstruct the history of vertical movement of the islands and the adjacent deep sea floor, including midplate swells. As judged by coral thickness, islands with barrier reefs sink as though they were on thermally youthful crust regardless of the actual age. Reefless islands do not sink until truncated by erosion. Apparently, thermal subsidence is balanced by isostatic uplift in response to erosion. Barrier reefs prevent wave erosion of encircled volcanoes and capture products of stream erosion so that isostatic uplift is eliminated. Insular shelves widen initially at rates of 0.6 to 1.7 kilometers per million years; the rates decrease with time. Thus the subsidence of islands depends on the size of the is land and the presence of reefs, and it may not always be the same as that of the surrounding oceanic crust.