1. Bring two quarts of moist soil, a cake pan, a sprinkling can of water and a quart of grass clippings to class. 2. Share background material, and introduce the word "erosion." 3. Prepare a small model hill by mounding the soil in the cake pan. Explain that the mound represents a hill and that you will make it rain by pouring water from the sprinkling can. Ask students to observe so they can report when the rain "walks" down the side of the hill and when it "runs."