Scientists Say: Stalactite and stalagmite | Science News for Students

Scientists Say: Stalactite and stalagmite

These are formations that occur in caves when water evaporates and leaves minerals behind
Aug 27, 2018 — 6:30 am EST
stalactite stalagmite

This is a chamber in Luray Caverns in Virginia. Stalactites hang from the ceiling, and stalagmites grow up from the floor.


Stalactite (noun, “Stah-LACK-tight”)

This is a mineral formation found in a cave. Water in the cave drips down, over and over in the same place. If the water evaporates before the droplet falls, the minerals in the water remain behind on the ceiling of the cave. As they solidify, they form rock. Over many years, the minerals collect into a long icicle made of rock — a stalactite. 

Stalagmite (noun, “Stah-LAG-might”)

This is another mineral formation found in caves. In this case, water drips down onto the floor, over and over on the same spot. The water evaporates, leaving any minerals in it behind. Those minerals pile up over time and solidify into rock. Over many years, they will form a rock mound on the floor — a stalagmite.

How do you remember the difference between a stalagmite and a stalactite? Stalactites cling tight to the ceiling. Stalagmites might hang from the ceiling — but they don’t.

In a sentence

Tiny worms can live inside stalactites, eating bacteria they find there.

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Power Words

(more about Power Words)

bacteria     (singular: bacterium) Single-celled organisms. These dwell nearly everywhere on Earth, from the bottom of the sea to inside other living organisms (such as plants and animals).

evaporate     To turn from liquid into vapor.

mineral     Crystal-forming substances that make up rock, such as quartz, apatite or various carbonates. Most rocks contain several different minerals mish-mashed together. A mineral usually is solid and stable at room temperatures and has a specific formula, or recipe (with atoms occurring in certain proportions) and a specific crystalline structure (meaning that its atoms are organized in regular three-dimensional patterns). (in physiology) The same chemicals that are needed by the body to make and feed tissues to maintain health.

stalactite     A mineral formation found in caves that forms in much the same way that icicles do. Liquid water slowly drips down from a surface. But if the water evaporates before the drop falls to the ground, any minerals in the water may solidify to form rock. Over time, the stalactites may grow to a meter or more across and many, many meters long.

stalagmite     A mineral feature that can develop in moist caves. Water that drips down from the cave ceiling can very slowly evaporate, leaving behind an upward-growing mound of mineral deposits, or rock. Most of these structures, which resemble upside down icicles,have rounded or flattened tips.