How can a cave form from solid rock? Most caves are found in limestone, a rock made of materials of calcium carbonate. This rock is unusual because the solid minerals it is made of easily dissolve in weak acids. The most common weak acid in the environment is actually water!
Earth processes such as volcanic eruptions, floods, landslides, and glaciers leave behind evidence of their passing in the form of layers known as deposits. By studying deposits of recent geologic events, geologists are able to better understand older deposits and identify the processes that caused them.
Try this activity from the Association of American State Geologists!