A stalagmite (UK: /ˈstæl.əɡˌmaɪt/, US: /stəˈlæɡˌmaɪt/; from the Greek σταλαγμίτης – stalagmitês, from σταλαγμίας – stalagmias, "dropping, trickling")

is a type of rock formation that rises from the floor of a cave due to the accumulation of material deposited on the floor from ceiling drippings. Stalagmites are typically composed of calcium carbonate, but may consist of lava, mud, peat, pitch, sand, sinter and amberat (crystallized urine of pack rats).

The corresponding formation hanging down from the ceiling of a cave is a stalactite.

 

Note:   The above text is excerpted from the Wikipedia article Stalagmite, which has been released under the GNU Free Documentation License.