CAVES:  THE GREAT DETECTIVE STORY

GEOLOGISTS are scientists who study the earth and how it was formed.  Geologists are like detectives looking for clues as too how something happened and sometimes they look for clues that are millions of years old.   Whenever they see a river, a mountain or even a cave these scientists begin to search around to see what made them.

CAVES are natural holes or passageways in the earth.  A geologist would probably wonder two things about a cave, what made the tunnel and what kind of rock is the cave found in.  This scientist looks around at the rock and she notices some FOSSIL shells.  Fossils are the evidence of past life like a bone, foot print or shells.  Not all rocks have fossils in them but this does.   These fossils are the remains of ancient sea creatures and tell geologists that a shallow ocean used to be where she now stands.  She imagines all the animals that at one time swam in that sea and when they died their bodies floated down on top of each other.  Eventually, these layers of shells and dirt were squeezed into a rock called LIMESTONE.

This geologist has tested limestone in her laboratory before and she knows that it can be dissolved by ACIDS.  Acids are chemicals that dissolve or eat away at rocks, metal, and other things.

Some acids are very dangerous and should only be handled by an adult, but some acids are harmless and can be found in juices, soda pop, or even water.

A stream flows out of the cave entrance and the scientist wonders where the water comes from.  She knows limestone often has cracks in it and that rain water has an easy time going through it.  Because of this, she decides that when it rains on the rock layers above the cave, some of that water must flow out the entrance in front of the geologist.  This researcher also remembers that rain water often picks up CARBON DIOXIDE when it hits the earth and goes through the soil as it travels downward.  Carbon dioxide is a type of gas and this is the gas that makes soda pop bubble.  As water and carbon dioxide mix they make a very weak acid called CARBONIC ACID.  Carbonic acid can dissolve away limestone but it takes thousands of years.

So the geologist believes after putting together all the clues, that this cave was carved out of solid rock by carbonic acid in the ground water as the water flowed down through the layers of limestone.