Stalactites and stalagmites are types of mineral deposits found in caves that accrue through the processes of solution and deposition. Stalactites hang downwards from the ceiling of caves, whereas stalagmites rise upwards from the floor of a cave.
Both stalactites and stalagmites are types of speleothems, mineral deposits that form on the insides of caves through the deposition of soluble minerals such as calcium carbonate, which forms limestone.
Stalactites form exclusively on ceilings as dissolved minerals drip down in the form of mineralized water, whereas stalagmites form where the dripping mineralized water touches the floor and deposits its minerals.
Because they are formed as two parts of the same process, stalactites and stalagmites can grow to the point where they connect with one another. Such connected formations are called columns.
Soluble minerals like calcium carbonate (which forms limestone) drip from the ceiling of a cave and deposit themselves on the floor. This quick video depicts the formation of stalactites and slatagmites through an animated diagram:
The most common form of stalactites and stalagmites appear in limestone caves, formed of calcium carbonate by dripping water. These limestone formations build up over a long period of time, often spanning thousands of years.
Another form of stalactites and stalagmites are formed in lava tubes while lava is still actively flowing. The flowing lava takes on the role of mineralized water in limestone caves, depositing material on the ceiling and floor of the lava tube as gravity affects its flow. Unlike limestone formations, lava stalactites and stalagmites are formed in a matter of hours, days, or weeks.
Ice stalactites and stalagmites are formed where freezing temperatures solidify dripping water into formations of ice. Like lava formations, ice stalactites and stalagmites can form within hours or days. Due to rising hot air, that water is more likely to form ice stalagmites than ice stalactites.
Stalactites and stalagmites have also been known to form on concrete ceilings and floors.
Around the World
The world's largest stalactite is located in the White Chamber of the Jeita Grotto, Lebanon. Jeita Grotto, a set of 2 interconnected limestone caves is the pride of Lebanon and the longest cave in the Middle East. It has been featured as a finalist in the New 7 Wonders of Nature.
The world's largest stalagmite is 62.2 meters tall located in the Cueva Martin Inferno, Cuba. The Martin Inferno Cave has unique compound calcium formations called gypsum flowers. It is an irreplaceable natural refuge for a colony of butterfly bats, the smallest in the world.
In China, you will find a rare instance of beautiful, multicolored stalactite and stalagmite formations in the Reed Flute Cave located in Guilin, Guangxi. The cave is famous as the "Palace of Natural Arts." The natural rock formations, illuminated with artificial light, make it one of the most extraordinary underground scenes in all of China.
Just in the United States, there are beautiful caves with very interesting history as part of some national parks or otherwise. Here is a glimpse of the Top 10 US Caves with details of history and formations.