海穴
Grotto
澳洲海岸線綿長，「海穴」是其中一個地理特徵，當水積聚，並慢慢滲透，最終腐蝕地表，形成大坑，就是「海穴」了。
Australia has a beautiful long coast line. ‘Grotto’ is one of the many geographic features.
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Water fills a swampy depression.
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Water seeps through the clay surface to the limestone below.
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Weak acids begin to dissolve the limestone layers.
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A sinkhole is formed which, in time, becomes bigger and shapes the Grotto.
Source: Parks VICTORIA
