Let's Go Caving!

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Updated on Apr 29, 2013

The formation of stalagmites and stalactites happens through the capillary action between porous rocks and water rich in minerals. The rocks attract the water and the moisture accumulates until gravity forces drops to form. The air evaporates some of the droplet, so that mineral deposits collect and build as additional drops form on top.

This project offers an opportunity to observe the gradual formation of stalactites followed by the reverse build up of stalagmites. When heavier droplets fall from the tip of the stalactite to the ground, evaporation causes the upside down pile of minerals.


How are stalagmites and stalactites formed?


  • Epsom salt
  • Black poster board
  • Tape
  • Scissors
  • 4 drinking glasses
  • Black yarn
  • 4 washers
  • A ruler
  • A small pot
  • A spoons
  • Logbook


  1. Cut a 4 ½x 9 inch piece of the poster board, and bend the length of the piece into a semicircle.
  2. Place two drinking glasses at least at the ends of the semicircle on the outside. Make sure that the glasses are at least 1 inch above the poster board (5 ½ inches).
  3. Tape the ends of the semicircle to the outside of the two glasses.
  4. Place the other two glasses at equal distance between the ends, on the outside of the semicircle and tape them to the poster board.
  5. Cut 2 16-inch pieces of black yarn.
  6. Tie the washers to the ends of the yarn.
  7. Stretch the yarn pieces across the glasses in a slightly sagging “X” shape with the washers inside the glasses.
  8. Fill the small saucepan with water, and add Epsom salt, stirring until no more salt dissolves.
  9. Heat the water slowly and continue stirring and adding salt.
  10. Fill each glass with the salt water.
  11. Place in a safe spot where the cave will not be disturbed and observe daily for about two weeks.
  12. This project can be visually chronicled with photographs labeled by day and brief captions.
Jane Frances Healey taught for many years at both the college and high school levels. Currently, she's a freelance writer in the San Francisco area, and she enjoys doing research on a wide variety of topics.

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