"Why does one volcano blow its top while another merely oozes lava? How do eruptions affect the ozone layer and global climate? Find out by plunging into descriptive volcanology at How Volcanoes Work.
Writing for teachers and college and graduate students, geologist Vic Camp of San Diego State University methodically explains volcano taxonomy and terminology. The site describes what happens during an eruption and tells why some eruptions are explosive and others aren't. (Magma viscosity and temperature are key.) Spectacular illustrations include photographs, maps, and animations of eruptions that take you into the belly of a volcano. Also worth a look are the vivid descriptons of historical eruptions, spiced by first-hand accounts from survivors.
Another section ventures off our planet to explore extra-terrestrial volcanoes, such as the sulfur-spurting "pimples" on the pockmarked face of Io, one of Jupiter's moons. Links to webcams allow you to keep tabs on active volcanoes such as Mount St. Helens and Mount Etna." -- Science, vol 292, April 13, 2001