Geysers are heated by volcanic activity too. Visit Yellowstone National Park's site for a great interactive about geysers. Yellowstone also has a history of volcanic activity – learn about it – great image of convection in the mantle too.
Teachers will find great materials at NeoK12 where it will give you lots of resources online, videos and quizzes for your volcano unit.
Volcanic vocabulary can be an entirely new language. Do your best to keep up with this alphabetic glossary.
Volcano World is a great place to visit for additional knowledge, lesson plans and more.
The USGS has a great site with multiple volcano resources for teachers. You will find details about volcanic science, animations, current status on active volcanoes, maps, photos, lesson plans, webcams, and lots and lots more.
NASA keeps tabs on volcanoes all around the earth. Visit this site to get updates on current volcanoes, animation for your instruction and lots more.
The best interactives on volcanoes -- you will want to explore these!! Show your class how rocks melt, how volcanoes erupt, plate tectonics and so much more – from Annenberg.