Geology for Kids

Caves have a fascinating history – millions of years of in the making!

Caves don’t start as caves; they form in rocks over millions of years! Most caves are formed in limestone, dolomite, gypsum, and marble – rocks that can be easily dissolved over time. Cave of the Winds is made up of limestone formations.

A cave begins to form when water seeps through cracks in the rock. Rainwater absorbs carbon dioxide in the ground and forms a weak acid called carbonic acid. This acidic water moves through the limestone towards the water table, dissolving the limestone and developing an underground channel. This channel is like an underground river. Water begins to fill every open crack in the rocks below the water table, and when the water table drops, the upper passageways fill with air and the limestone dissolves quickly due to the large amount of carbonic acid in the cave.

Now the fun begins: cave decorations or “speleothems” begin to form. These speleothems are the shapes you see in caves: stalactites, stalagmites, and more. Speleothems form as the minerals in the water build up, one on top of the other, as the water drips and drizzles throughout the cave. It can take between 1-1,000 years for one cubic inch of a speleothem to form!

The color of speleothems is determined by the mineral content. Pure calcite (crystallized limestone) is white or almost colorless. In Cave of the Winds, other minerals such as iron combine with the calcite, and the color can go to red, orange, and even black.