When the water at the top of the cave slowly leaks downward, the calcium bicarbonate in the water reacts as mentioned above, some are deposited at the top of the cave, and some are deposited at the bottom of the cave. Over time, stalactites were formed at the top of the cave and stalagmites were formed at the bottom of the cave.
Extended data:
Reflected climate change:
Stalagmites generally grow every year, unless the dripping water stops at the top of the cave in a particularly dry year. With the change of seasons, the water dripping from the cave top contains different substances, so stalagmites, like tree rings formed by trees, will form their own annual rings, through which the age of stalagmites can be counted.
Many stalagmites were formed a long time ago. Because there was no dripping water, stalagmites stopped growing, so they became "dead" stalagmites. Researchers have a way to accurately determine the growth date of these stalagmites.
With the change of climate, the substances contained in calcareous stalagmites will also change. Scientists can restore past climate change by measuring the changes of these substances. There are many limestone caves in China, in which a large number of stalagmites grow, which have become important materials for paleoclimate research.
For example, Dongge Cave in Guizhou, Hulu Cave in Nanjing and Vientiane Cave in Gansu are all geomantic treasures for studying ancient climate by using stalagmites. Now scientists all over the world are studying these stalagmites. Stalagmites are also considered as another pillar material in paleoclimate research after deep-sea sediments, ice cores and loess because of their accurate dating.
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