Apparently, there are myriad ways in which rocks are broken by nature. Just when we think we have it covered, the brilliant scientist hits us with another of nature's methods. Do you remember when we had projects which explored erosion? This writer made a comment that plants are a part of erosion. Well, check it out!

Cut one side from a milk carton, and half-fill it with moist soil. Plant some soaked corn or lima beans just under the surface of the soil, and pour about 1/4 inch of plaster of
Paris on top of the soil. Set the carton aside, and examine it daily. You will soon see germinating seeds push up under the plaster with enough force to break it.

Similarly, you can plant seeds and place a sheet of glass over them.

You will soon see that the germinating seeds raise the glass. We've used glass because it allows you to observe the process directly.

Germinating seeds can either cause rocks to move out of their way or crack them into smaller pieces.

The first part of this is that the wind deposits tiny amounts of soil into little cracks and pockets in the rock. The rain moistens it. Rain, wind, and animals (including birds) bring seeds to the little soil deposits.

You might explore the school grounds and the areas around your house, to find places where plants have broken through asphalt or concrete.