The storybook "What Is a Volcano?" comprehensively overviews volcanoes. It describes how volcanoes form when hot magma breaks through the Earth's crust. The narrative highlights various types of volcanoes, such as those formed by plate collisions, hot spots, and separating plates. It discusses significant volcanic sites like Mt. St. Helens and Hawaii's volcanoes. It explains the process of magma cooling into igneous rock, citing the Pacific Ring of Fire as a hotspot for volcanic activity. The story also touches on ancient beliefs about volcanoes and underscores their powerful presence throughout Earth's history.