How Do Stalactites & Stalagmites Form in Caves?

Stalactites and stalagmites are both forms of speleothems, which comes from the Greek words “spelaion,” which means “cave,” and “thema,” which means “deposit.” Stalactites grow from the ceilings of caves, whereas stalagmites grow from the floors.

Speleothems are formed by water. When rainwater comes through the cracks in rock formations, it bonds with carbon dioxide to form carbonic acid. The carbonic acid then goes through joints and cracks in the limestone. Following that, calcite, a mineral, dissolves from the limestone of caves. When the water carrying the dissolved limestone is exposed to the air in the cave, it releases carbon dioxide. It’s a similar effect to the “fizz” when opening a bottle of Coke. The carbon dioxide releases the calcite, which redeposits on the ceilings and floors of caves, forming stalactites and stalagmites.

There are several factors that contribute to the growth rate of stalactites and stalagmites. They include the following:

• Outside temperature
• Rainfall amount

The shapes of stalactites and stalagmites are mostly due to the acidity level in the water that comes into the cave. Finally, it is the general scientific consensus that the color of stalactites and stalagmites are determined by mineral content. Calcite, in its purest form, is white, almost colorless. But iron and other minerals can bond with it, which creates the different colors seen.