The source of stalactites:
When the water at the top of the cave slowly leaks downward, the calcium bicarbonate in the water will react as mentioned above. Some of them are deposited at the top of the cave, while others 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. When stalactites and stalagmites are connected, they form stone pillars.
Extended data
Formation and type
Stalactites are deposited by calcium carbonate and other minerals. Limestone is a kind of calcium carbonate rock, which is decomposed by water containing carbon dioxide to form calcium bicarbonate solution. The chemical equation of this reaction is:
CaCO？ (s)？ +? h？ O(l)？ +? CO？ (aq)？ →? Ca(HCO？ )? (ask)
The aqueous solution flows down the rock until it reaches the edge. If the rock is at the top of the cave, water will drip down. When the solution comes into contact with air, an inverse chemical reaction occurs and calcium carbonate precipitates. The inverse chemical equation is:
Ca(HCO？ )? (aq)？ →? CaCO？ (s)？ +? h？ O(l)？ +? CO？ (ask)
The average annual growth rate of stalactites is 0.1.3mm. The rapidly growing stalactite aqueous solution is often rich in calcium carbonate and carbon dioxide and flows quickly. This kind of stalactite can grow 3 mm a year.