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| The Grotto - Great Ocean Road, Australia |
The Grotto is sinkhole geological formation located along the Great Ocean Road. To further explain what a sinkhole is, let me quote this excerpt from the US Geological Survey site,
Sinkholes are common where the rock below the land surface is limestone, carbonate rock, salt beds, or rocks that can naturally be dissolved by ground water circulating through them. As the rock dissolves, spaces and caverns develop underground. Sinkholes are dramatic because the land usually stays intact for a while until the underground spaces just get too big. If there is not enough support for the land above the spaces then a sudden collapse of the land surface can occur.
