I did not teach this in class due to the lack of time and also because it is not covered in the syllabus. I will not test you on the formation of these cave features. BUT I can still test your knowledge of the action of water as an agent of weathering. This is still important.
And now... presenting...
Stalactites...
Limestone caves are made up of calcite (mainly).
Calcite is a mineral.
Calcite molecules are made of calcium and carbonate --> calcium carbonate (CaCO3)
Rainwater falls over a cave and trickles through the rocks.
Rainwater picks up carbon dioxide from the air, and minerals from limestone.
Rainwater + Carbon Dioxide + Calcium Carbonate = Calcium Bicarbonate + water
Water carries Calcium Bicarbonate through the cracks of the roof of the cave.
Once the water passes through the roof and comes in contact with air (inside the cave), some Calcium Bicarbonate transforms back into Calcium Carbonate (Calcite).
Calcite starts to form around around the crack.
Water continues to drip through the crack.
Length and thickness of the calcite grows.
Usually takes about 100 years to grow 0.5 to 2.5cm.
Stalagmites
Water continues to drip from the end of the stalactite, and falls to the ground.
Deposits more calcite into a mound.
Soon stalagmite will form in a conelike shape.
This is why we usually find stalactites and stalagmites in pairs. Sometimes they will even grown to form one big column.
