江苏省宜兴县山多洞多,全县已经发现的奇岩异洞共有二十四个。人们进入洞中,有如置身于另一世界,所以有人称这些奇岩异洞为洞天世界。据地质工作者考察研究,有岩洞的山,大多是石灰岩。石灰岩经地下水长期的侵蚀,形成了岩洞,所以称它为石灰岩溶洞。石灰岩是碳酸钙,它遇着水里的碳酸,就成酸性碳酸钙。而酸性碳酸钙是溶解于水的,这就是岩洞形成和逐渐扩大的缘故。水渐渐干的时候,碳酸钙分解成水和二氧化碳跑走,剩下的便是固体的碳酸钙。从洞顶下垂凝成固 Yixing County, Jiangsu Province, Hill more holes, the county has found a total of twenty odd hole abnormalities. People into the hole, as if exposure to another world, so some people call these strange rock holes into the world. According to the study of geological workers, there are cave mountains, mostly limestone. Limestone erosion through long-term groundwater, the formation of caves, so called limestone caves. Limestone is calcium carbonate, which in the case of carbonated water, it becomes acidic calcium carbonate. The acidic calcium carbonate is dissolved in water, which is the reason for the formation and gradual expansion of caves. When the water is getting dry, the calcium carbonate breaks down into water and runs off with carbon dioxide. The rest is solid calcium carbonate. Hang down from the top of the cave into a solid