The following volcano model is a great way to show your class how it erupts, and is also very fun! You can have students make this for extra credit, or you could do it for your class to see.
lampshade (that you won't be able to reuse!)
cup to fit in the smaller lampshade hole
plastic or board for volcano to sit on
Paint (to make lampshade look like volcano)
IF YOU WANT TO MAKE LAMPSHADE MORE REALISTIC:
PUT THE FOLLOWING "PLAY DOUGH" MIXTURE OVER VOLCANOE BEFORE YOU LET IT ERUPT, LET DRY FOR HOURS, THEN PAINT OVER THE PLAYDOUGH TO MAKE IT COLORFUL.
Play Dough mixture:
Mix in medium pot:
1 C flour
1/2 C salt
1 Tbsp oil
2 teasp. cream of tartar
1 C of water
2 teasp. food coloring
Cook over medium or medium high hear and stir (3-5 min.) It will look like a "globby" mess. Store in air tight container until ready to spread over lampshade.
Now, this has sounded difficult but it really is not bad. If you choose to use the play dough, spread it evenly over your lampshade and let it dry 24 hours. Either if you chose to use the play dough or not, paint either the lampshade or dried play dough to the colors of a not-yet-erupted volcanoe. Then, place the cup in the lampshade hole (it is ok if there is some cup sticking out). Let paint completely dry and you are ready for an eruption! Fill the cup halfway with baking soda. Then when the carpeting is protected and your audience is ready, begin pouring 3 parts vinegar and 1 part red paint (mix together before hand) into the cup with baking soda and watch the eruption. It should last until the baking soda in the cup has run out, or you have ran out of vinegar.
This activity is very enjoyable. If you have any questions, feel free to contact me at firstname.lastname@example.org