Making a model of Mount Vesuvius is a great way to get your students to become more engaged in your lesson plan -- especially if it erupts, as everybody loves an explosion. It is a simple project that can be completed even by first-graders, though some assistance may be necessary. All you need is some cardboard and paint for the model. The erupting part of the model is replicated with the classic vinegar and baking soda mixture.
Place a cardboard tube 6 inches high in the middle of a cardboard panel that is a foot wide by a foot long. Glue the cardboard tube to the panel at the base of the tube. Place the plastic bag on the tube and push the bag down so that it forms an internal bladder.
Cut a long strip of cardboard 8 by 20 inches. This strip will form the walls of the volcano. Wrap the strip around the cardboard tube so that it slants at an angle from the top of the tube to the bottom cardboard square. It does not matter at what angle, it just has to look like the slope of a mountain. Ensure that the top of the plastic bag is under the cardboard strip. Glue the base of the cardboard strip, the top where it touches the cardboard tube and where the cardboard strip overlaps itself. Hold the strip steady for a minute to ensure that the glue bonds.
Paint the outside of the volcano in the image of Mount Vesuvius before the eruption. Use white paint on the top to replicate the snow line and muted grays and browns on the bottom. For added effect, put on model trees and Roman villas to really bring the observer into the display.
Pour 1 tsp. of baking soda into the bag inside the center of the volcano. Put several drops of red food coloring in the baking soda to get a red lava effect. Pour 1/2 tsp. of vinegar when you want to trigger the eruption. The plastic bag will allow you to reuse the model multiple times if you clear away the erupting foam promptly enough to ensure that the cardboard is not soaked with vinegar/baking soda solution.