海岸线是怎么变动的?

2025-03-15 14:25:50
推荐回答(1个)
回答1:

距我们最近一次的大海退,海水在距今大约7万年前开始下落,直至离现在两三万年前,海面才达到最低点,持续时间达四五万年之久。当时的海平面要比现在的海平面低100多米,那时地球表面的海陆分布是什么局面呢?

就拿我国沿海地区来说,现在渤海平均水深只有21米;福建和台湾之间的台湾海峡,广东雷州半岛与海南岛之间的琼州海峡,水深都不足100米。

因此,当海平面下降100米的时候,渤海消失了,台湾岛和海南岛与我国大陆连成一块完整的大陆。

同样,由于我国东部的黄海海底大部分露出水面,朝鲜、日本和我国大陆之间没有海水阻隔也连接起来。

世界海陆分布形势当然也会发生惊人的变化:白令海峡的消失导致亚洲和北美洲相连;马六甲海峡和其他海峡的消失使现在散布在海洋中的群岛连成一片陆地,从而使亚洲和澳大利亚大陆也连接了起来。世界其他地方凡是海水水深小于100米的海区都变成了陆地。

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