This trim overview gives young readers an excellent grounding on volcanoes in an efficient few words. Branley starts out strong with direct, one-page descriptions of how Mount Vesuvius buried Pompeii, Mount Tabora made 1816 the year without a summer, and Mount St. Helens "covered fields and ponds" and "buried animals, houses, and people" in mud. There follows a succinct and easily readable explanation of how volcanoes are caused by magma pushing up between (or through) moving plates in the earth's crust. Then comes a pair of snappy maps, with bright little bursts of color denoting the Pacific Ring of Fire and other volcano locations throughout the world. Simont's varied illustrations--be they maps, diagrams, turbulent scenes, or pictures of people--are as vigorous and telling as the text.