Limestone caves are an interesting geological feature. They form because the limestone deposits located under the ground are chemically dissolved by moving ground water. The ground water contains minerals that make the water slightly acidic. When an acid comes into contact with a rock that is composed of calcium carbonate a chemical reaction takes place. The acid "eats" the limestone. The calcium carbonate then goes into the ground water which moves down farther into the cave. The water will find its way into small crack and crevasses. The dripping water will create formations called stalactites and stalagmites.

Stalactites (they grow from the ceiling)and stalagmites (they grow from the floor) are not technically limestone. They form in caves because as the limestone is dissolved calcium carbonate is put into solution in the ground water. This solution drips through crack and slowly forms stalactites and stalagmites.

The photo to your right shows both stalactites and stalagmites growing together in Jewel Cave National Park in South Dakota.

Click on the "Next" button to learn about a rock made from many rounded rocks.