What Makes a ‘Volcano’ Erupt So Violently?

A volcano erupts when pressure builds up inside the Earth like a bottle of soda being shaken and then opened. Imagine you have a bottle full of soda, and you shake it, bubbles form inside. When you open it, the soda fizzes out in a big rush! A volcano is kind of like that bottle: magma (hot liquid rock) builds up pressure underground, and when it finally comes out, it erupts violently.