The final product will be a model volcano with a cutaway view exposing transparent plastic tubes in the volcano's vents. The flat, cutaway side is decorated with a representation of the strata and internal structure of the volcano. A small bottle, such as a hotel shampoo or conditioner bottle, is connected to the base of the tubing and holds a vinegar-based mixture to react with baking soda and simulate an eruption through the vents.
You can mold the volcano out of salt dough, a type of modeling clay that dries on its own and is easy to make from common household ingredients. To create salt dough, thoroughly mix two parts salt, two parts flour and one part water in a large bowl. Add water until the dough is at the consistency you want. It should be easy to mold but firm enough to hold its shape. A salt dough model will dry over the course of a few days, depending on its thickness.
You can build a model in the shape of a major style of volcano you are studying, such as shield, cinder cone or composite. Form salt dough into half of the characteristic shape you have chosen, with a vertical flat surface representing the cross-section of the volcano. While the dough is still wet, press transparent plastic tubing into the central vent of the volcano and attach the small bottle to the bottom with electrical or duct tape.
The style and detail of decorations depend on the scope and style of your project. Use tempera paints to indicate areas of grass, rock, snow and lava on the outside and to show the volcano's strata on the flat cross-section. To create an eruption, fill the bottle 3/4 full with a mixture of vinegar, liquid dish soap and red-orange food coloring. Wrap a tablespoon of baking soda in a square of tissue and drop it through the main tube into the bottle. The resulting reaction should cause the mixture to foam and fill the clear plastic vents.