Karst caves that produce stalagmites and stalactites are made of limestone. The main component of limestone is calcium carbonate, which can react with water and carbon dioxide to produce water-soluble calcium bicarbonate. Calcium bicarbonate penetrates from the crack at the top of the cave and adheres to the top of the cave. Then, due to water evaporation, pressure reduction or temperature change, part of the carbon dioxide in calcium bicarbonate decomposes and precipitates calcium carbonate, forming a small protrusion, and then gradually becomes larger and extends downward. Over time, a bell shaped stalactite is formed.
The growth rate of stalactite is very slow, and it takes about hundreds of years to grow by 1 cm.
Stalagmites are formed by water droplets on the top of the cave. Is a close partner of stalactite. When the water drops on the top of the cave fall, the calcium carbonate contained in it is deposited on the ground, gradually forming stalagmites in the shape of bamboo shoots. Stalagmite is relatively firm, so its growth speed is faster than stalactite. Sometimes it can form a stone tower more than 30 meters high.