Formations in Limestone Caves Most caves are formed in limestone, a type of rock that easily dissolves over time. Caves form when rainwater seeps through cracks in the limestone. Sometimes, the water drips down through cracks. Other times, the woater gushes. Over a long period of time, the limestone wears away, leaving a large empty space called a cave. As water drips from the ceiling of a limestone cave, formations that look like icicles may appear. These formations are called stalactites. The stalactites grow in size and continue to drip water down to the ground of the cave. On the ground, a cone-shaped piece of rock begins to form. This formation is called a stalagmite. Sometimes a stalactite and stalagmite grow together. They form a kind of post called a pillar. Limestone pillars are a beautiful rock formation. How does one remember which formation hangs down from the ceiling and which grows up from the ground? Note that the word stalactite includes the letter c. Think of c as standing for ceiling. The word stalagmite contains the letter g. Think of g as standing for ground. Thus, a stalactite hangs from the ceiling and a stalagmite grows from the ground.

Which statement about limestone caves is an opinion?

1.Limestone pillars are a beautiful rock formation.

2.Limestone is a type of rock that dissolves over time.

3.Cracks in limestone allow rainwater to seep through.

4.Limestone caves have formations called stalactites.