We recently visited Carlsbad Caverns National Park in New Mexico, and were awe-struck by the beauty of the caves' stalactites and stalagmites. In case you need a refresher– stalactites grow from the cave ceiling and "hold on tight", while stalagmites grow from the ground and "are big and mighty." The word stalactite comes from the Greek stalasso which means "to drip".
The official description of Carlsbad Caverns on Wikipedia states: "Erosion above ground created the natural entrance to the Carlsbad Caverns within the last million years. Exposure to the surface has allowed for the influx of air into the cavern. Rainwater and snowmelt percolating downward into the ground pick up carbon dioxide; once this water reaches a cavern ceiling, it precipitates and evaporates, leaving behind a small calcium carbonate deposit. Growths from the roof downward formed through this process are known as stalactites. Additionally, water on the floor of the caverns can contain carbonic acid and generate mineral deposits by evaporation. Growth from the floor upward through this process are known as stalagmites.
Here is a great, easy science experiment you can do at home with common materials!
Gather these items:
Sturdy box • Large cup or glass • String or yarn • 4 washers or nuts • Epsom salt • Scissors
Cut the string or yarn into four pieces, about 18 inches long.
Tie the washers, nuts, or other small heavy object to the ends of your string.
Trace the bottom of your glass on the top of the cardboard box.
Inside that circle, trace the top of the glass.
Cut out the circle in between the two traced circles so your glass will fit snugly in the hole.
Carefully punch four holes around your circle cutout.
Measure about a cup of epsom salt into two cups of warm water.
Stir until completely dissolved.
Pour this mixture into your glass (we used a tall paper coffee cup).
Soak your strings in the epsom mixture.
Place a piece of aluminum foil, parchment, or other water resistant item inside your box on the bottom, underneath the glass/cup and holes.
Leaving the washers in the bottom of the cup,
carefully pull each string out and through the holes you cut out.
Pull them through a few inches into your "cave" which is the inside of the box.
Your strings will start to drip immediately.
Within hours, your stalactites will begin to form. Check back every day for new growth!