Give background information on volcanoes to the fourth graders: what is a volcano, what does it look like and the types of volcanoes. The fourth graders will understand the demonstration better when they learn that molten rock, gases and pyroclastic debris erupt through the earth's crust and make volcanoes that vary in their structure -- cracks, domes, shields, or mountain-like structures with a crater at the summit. Familiarize them with related terms such as "magma'', the molten rock within the Earth's crust, which erupts to form "lava" that is thick and slow-moving or thin and fast-moving. The demonstrations will help the fourth graders understand the earth science lessons better.
Place an empty pop bottle on a paper plate and use modeling clay to make volcano around the bottle except the top mouth area of the bottle. Put 3 -4 spoons of baking soda, a few drops of liquid dishwashing detergent and half a cup of water into the bottle. Add red food coloring to one-half of a cup of vinegar. Use a funnel to pour the vinegar mixture into the bottle and quickly remove the funnel. See the volcano erupt; vinegar reacts with baking soda to form carbon dioxide gas that pushes the "lava" out of the "volcano." The chemical reaction gives the physical volcano eruption appearance.
To make your volcano, you need a one-pound coffee can with both top and bottom ends cut out. Insert it through a hard flat cardboard such that one-fourth of the can is below the cardboard. Tape the edges of the cardboard that comes into contact with the can. Use sturdy paper plates around the coffee can to make a volcano shape and tape it to the coffee can and cardboard base. Have two students hold up the setup and insert a toothpaste tube through the bottom end of the can. Press slowly to see that paste goes up without moving to the sides of the tube. This models the "plug dome volcano," in which the thick magma moves slowly up through the volcano to form lava that pushes up as a large mass forming a dome. Replace the toothpaste with a well-shaken can of shaving cream. Press to notice a large volume of lava coming out; this large broad-based volcano is a model of a shield volcano. To demonstrate a cinder cone volcano, you will use a funnel with sugar pops or rice crispies on top of the volcano, and insert an extended tube connected to an air pump under and up through the model of the funnel opening (in place of the toothpaste or shaving cream). Press the air pump to blow out the cereal, a model of a cinder cone eruption.
Name some examples of the four types of volcano for better comprehension in students; Lassen Peak, Chaos Crags, and Bumpass Mountain in the Lassen Volcanic National Park are examples of plug dome; Mount Harkness and Prospect Peak (in the Lassen Volcanic National Park), Mauna Loa, and Mauna Kea (in Hawaii) are some famous shield volcanoes; Hat Mountain, Cinder Cone (near Butte Lake), and Fairfield Peak are examples of cinder cones in the Lassen Volcanic National Park; examples of composite volcanoes include Mount Tehama in the Lassen Volcanic National Park, Mount Shasta, Mount St. Helens, and Mount Rainier. Explain that rock comes from volcanic eruptions, also in other forms such as ash, cinders and pumice. Fourth graders learn that volcanic eruptions require heat and pressure and can cause severe damage to life and property.