1. What is a Cave?
Remember those aquifers? Well limestone erosion occurs in the aquifers that creates large empty pockets. These pockets are filled with water and minerals.
If the water table were to drop below these pockets they would become filled with air.
An underground opening created in this fashion is a cave.

2. What is a Cave? Erosion continues after the cave is created.
Water continues to move from the surface through the cave to the water table.
With that water comes dissolved minerals that get deposited in the caves.
Stalactites, Stalagmites and Columns are the results of that deposition

3. What are Stalactites?
Stalactites form when mineral rich water forms droplets on the ceiling of the cave.
As the water evaporates the minerals get left behind forming stalactites.

4. What are Stalagmites?
When the unevaporated water drips down from the stalactite it carries many minerals with it.
When that water then evaporates, the minerals left behind form stalagmites.

5. What is a Column
When a stalactite and a stalagmite finally reach each other they form a solid deposition of minerals called a column.
Columns can continue to grow as ground water continues to bring more minerals.
Many columns found in US caves are estimated to be many thousands of years old.

7. What happens when caves collapse?
A sinkhole occurs when the limestone surrounding the cave is weakened by acid in the water and can no longer support the surface above
Sinkholes can happen when a water filled cave is drained quickly.
Sinkholes often occur in areas with very permeable rock, and fast development such as in Florida suburban areas.

8. Tropical Storm Agatha caused a sinkhole to open in Guatemala City, Guatemala, in May 2010.

9. Water Erosion and Deposition
Both above the ground and below, water is the main force behind erosion and deposition on our Earth.
Our soil is both depleted and renewed by the sediments brought by surface water erosion.
Our fresh water supply comes from the underground aquifers from many miles away.
Our caves are leftover evidence of the size and power of groundwater erosion.

10. Discussion
Think of times when you have been to local parks or maybe Lake Michigan. Can you remember any evidence of surface water erosion?
Have you been to a cave? If not would you like to someday?
What would be some of the things you would look for in a cave?