Place a plastic bottle in the center of a large cookie sheet or shallow plastic container. Secure the cup to the cookie sheet by rolling a piece of masking tape with the sticky side up and placing it under the cup. Add a few small rocks in the bottom of the cup for added stability.
Tear off large pieces of aluminum foil and drape them from the edge of the bottle and down the sides to create the shape of a mountain. You may need several sheets of foil to cover the edges of the bottle all the way around. Allow the children to help fold and bend the aluminum foil until they've created the shape of the mountain.
Use a rolling pin to roll out enough modeling clay to place on top of the aluminum foil. Instruct the students to mash different colors of modeling clay together before rolling it out to create a unique mountain color.
Press the sheet of rolled modeling clay around the aluminum foil mountain, smoothing it around the top edges of the bottle and against the bottom edges on the cookie sheet.
Instruct the students to decorate the mountain with modeling-clay flowers, trees and small animals. Add blue modeling clay around the base of the mountain to represent water. Include small plastic figures to represent people. When the students have completed the mountain scene, move the cookie sheet with the mountain onto a table covered with newspaper.
Add 3 teaspoons of baking soda to the bottle in the center of the volcano. In a plastic cup, mix together a few drops of red food coloring with 1 cup of white vinegar.
Slowly pour the colored vinegar into the volcano cup and watch the eruption. Keep pouring colored vinegar into the cup until all of the baking soda is gone and the volcano is no longer "active."