What is a volcano?

A volcano is a mountain with an opening. Rock melts because Earth is hot inside. It can push up and spill out. It can boom and make ash.

A volcano is a mountain or hill with a deep opening in it. Far under the ground, rock can get so hot that it melts. When it gets squeezed up, it can come out as red-hot lava, ash, and smoke. It is a bit like a pot of thick soup bubbling over when it gets too hot.

A volcano is a place where melted rock from inside Earth can come out. Deep underground, rock melts into magma, which is liquid rock. Gases in the magma can push it upward through cracks in Earth’s crust, the hard outer shell. When magma reaches the surface, it is called lava. Volcanoes can also blast out ash, rocks, and steam. Fun fact: some lava makes pumice, a rock so full of tiny air holes that it can float on water.