Stalagmites and Stalactites

One sticks up from the cave floor, the other hangs down from the ceiling...but which is which!

Try this:

  • 1/2 fill two 250 mL beakers with saturated sodium bicarbonate solution.
  • Run a wet piece of string from one beaker into the other and allow the string to sag a little in the middle.
  • Leave overnight.


You will find that the bicarb has saturated the string and dripped from the sagging portion onto the bench forming a recognisable geological formation!


  1. Find out if there are any local caves you could visit. Been to Waitomo to see the Glow Worms?
  2. How do the stalagmites and stalactites form in caves?
  3. What kinds of creatures can you find living in caves?
  4. Investigate using other saturated solutions to grow a crystal garden, watch crsytals under a microsocope

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