We typically think of caves forming as rocks are dissolved and the particles
are washed away, leaving hollow spaces behind. This process may
occur when precipitation, such as rainwater or snowmelt, mixes with carbon dioxide from the air and from decaying plants in the soil and
forms carbonic acid. This acidic water then flows through cracks on the earths surface and seeps down into the rocks below. Once the acidic
water reaches carbonate rocks and other rocks that dissolve readily, it enters into the cracks and dissolves away the rock to create the rooms,
passageways, and speleothems (cave formations) of a cave.
This activity simulates how dissolution, a chemical weathering process, leads to the formation of caves.
Per student or small group:
1. Organize the sugar cubes into a half pyramid along the bottom of the bowl, making sure the sugar is pressed against one side of the bowl.
2. Seal the cubes tightly with the modeling clay, making sure there are no gaps. The clay layer should be about 1/8 inch deep.
The sugar cubes that are pressed up against the glass should remain visible. This will act as a window into your cave.
3. Poke holes through the top of the clay with the tooth pick, making
sure that the holes go all the way through to the sugar cubes and are
enough for water to flow through them.
4. Spray the top of the cave with the warm water from the spray bottle. Continue spraying until the sugar cubes are either no longer in their original shape or they have completely dissolved.
5. As the water seeps through the clay and into the sugar cubes, record your observations.
6. Draw a picture or describe what your cave looked like when finished. Discuss: What did the sugar cubes represent? What did the clay represent? Describe in your own words how this activity simulated the formation of caves.
For the full version of this summarized lesson plan, or additional educational resources, visit http://www2.nature.nps.gov/views/.