Science Experiment: Sinkholes in a Cup

Sinkholes in a Cup

Sinkholes are found all over the area here at Cave of the Mounds but don’t be worried, our sinkholes don’t sink very fast. These natural depressions are caused by water removing the underlying subsurface rock and soil. It’s apart of our Karst Landscape.

Sinkholes are common in certain parts of the U.S. and you can usually identify them as a round depression in the earth. Sometimes there can be standing water in them after it rains. We have one sinkhole called “Schools Sink” that often has a disappearing stream in it after it rains. Let’s learn more about sinkholes with this fun activity!

You will need: 1 8 oz. Styrofoam cup, Green rust-free scouring pad or very thin sponge, Empty two-liter bottle, One sheet of paper, Tape (I used scotch because it was the one I had closest to me), Sugar, Sand, Scissors, Writing tool (I prefer sharpie to trace out my circles)

  1. Start by making a hole in the bottom of the Styrofoam cup, roughly about the size of the tip of a pen.
  2.  Cut the green sponge into a circle the size of the cup’s bottom. Place the circle in the bottom of the cup.
  3.  Cut the paper into a strip the height of the Styrofoam cup. Roll it into a tube about one half the diameter of the cup, tape it to size, and place it into the center of the cup.
  4. Fill the inside of your paper tube with sugar and the outside of the tube with sand at equal heights, almost to the lip of the cup (that protruding edge at the top). 
  5. Remove the paper tube. Then place a thin layer of sand over the sugar, at least 1 cm thick.
  6. Cut the bottom off the two-liter soda bottle at about the same height as the Styrofoam cup. Fill the bottom half about halfway with water. This symbolizes the groundwater. 
  7. Place the Styrofoam cup in the center of the water to create a moat around the cup.
  8.  Watch as the water fills into the cup and the sugar dissolves and runs out. A sinkhole will appear in the cup where the sugar dissolved.
  9.   *You may need to remove the cup from the water for the water to drain and the sinkhole to form.