添加答案,寒冷和密度板,把它分解成背后的海洋地壳地幔可能扯掉,让人堕落,导致“突然”无论如何改变浮力的密度较低覆盖大陆地壳。这样我们有山脉,很好马克的主要地球上俯冲带。编辑:好的,扩大一点浮力的东西:原则上,大陆地壳的密度³~ 2.7克/厘米,海洋地壳~ 3。搜索“大陆裂谷作用”,开始“威尔逊循环”将阐明海洋如何开始。从一个大陆边缘海洋山脊,海洋地壳冷却,致密,下沉到部分熔融和韧性上地幔软流层”。因此海底深度是年龄的函数,达到5.5公里,在特殊的情况下。海洋地壳保持焊接到邻近的大陆,直到它冷却下来,强化使得它从字面上被撕掉,(*),开始陷入软流层。虽然它,它拖着其余的海洋地壳,和最终厚层的沉积物沉积形成的从欧洲大陆得到剪掉一个“增生楔”。沉积物层可以相当厚,许多公里例如侏罗纪(很旧,深)海底下兰萨罗特岛和Fuerteventura非洲海岸,当然和其他地方。大洋板块下沉保持凉爽,通过地幔密度而沉没。这样的区域发现了地震学在几个山脉。 Eventually, the weight of the "dangling" cold and dense ex-ocean floor gets too high so that it rips off. The overlying continental crust, suddenly released from an enormous weight, starts to rise quickly, sediments become exposed, erosion kicks in, and voila, valleys deep & mountains high form, with pretty picturesque sediment packages and their contents, today whale bones, in future plastic :-/ Examples for slabs: several stages of detached slabs under the Alps, fragmented slabs under the Himalaya, under the Cordilleres, Andes, ... (*) This explains also why oceanic crust has a maximum age, best consumed before :-) Oh, and in some cases, fragments of the ocean floor can be deposited between sediments and stay afloat. When it is exposed, this is called an "ophiolite". Hope that helps :-)