An exploding model volcano creates a dramatic science project or home learning activity. The explosion, called a volcanic eruption, comes from pressurised gasses within the volcano. The build-up of gasses causes the volcano to erupt, spewing molten lava---rock so hot it becomes burning, moving liquid---to flow out of the volcano, along with ash, smoke and debris. The National Aeronautics and Space Administration (NASA) Earthwatch website provides photos from space of recent volcanic activity all over the earth. Add to the model volcano learning experience by using books and websites on volcanology, the study of volcanoes.
Place layers of newspaper over the work surface to protect it from the volcano.
Use scissors to cut the top off the bottle where it widens below the opening. Angle the cut so that one side of the remaining part of the bottle is an inch higher than the other. The University of Montana's Montana Bureau of Mines and Geology website advises cutting the bottle at an angle to make it look like the opening of a real volcano.
Apply a dot of glue the size of a quarter to the cardboard base for your volcano model. Press the bottom of the bottle on the glue and hold it there for a slow count of 10. Allow the glue to dry for an hour---it may take longer on a rainy day or in humid conditions.
Put a half cup of vinegar, six drops of dish soap and two drops of red food colouring into the bottle. Don't add the baking soda until you want the volcano explosion.
Build the volcano model around the bottle of your volcano eruption mixture. The Montana Bureau of Mines and Geology website recommends using three batches of modelling clay to create a volcano around a 473ml bottle.
Measure four tbsp of baking soda into a half sheet of facial tissue and squeeze the corners together. Twist to hold the packet together. Put it in the bottle to start the eruption. It takes part of a minute for the packet to explode, so stand back and don't look into the volcano.
Create more eruptions by mixing all the ingredients except the baking soda in a pitcher. Pour the mixture into the volcano's bottle, and add the baking soda packet when you're ready to make the model volcano explode.
For a classroom project, or for repeated model volcano eruptions, put a tarp over the table and have sponges nearby for clean up. Make a clay volcano model. Paper mache will get soggy from eruptions.