means Volcanoes are openings in a planet's crust where molten rock, ash, and gases erupt from deep below, often building mountains over time.

from From the Italian and Latin name Vulcanus — Vulcan, the Roman god of fire and the forge. Sailors and scholars looked at the smoking, glowing island of Vulcano off Sicily and imagined the god hammering away at his underground furnace, sparks and smoke escaping through the mountaintop. The name spread to every fire-mountain on Earth, and Vulcan's smithy gave us 'volcano.'