Science
How do volcanoes erupt?
A volcano erupts when molten rock (magma) deep underground rises toward the surface. Trapped gases and immense pressure push the magma up through a weak spot in the crust, where it bursts out as lava, ash, and gas.
See it in motion.
Watch a 2-minute animated lesson that shows exactly how volcanoes works.
Step by step
- 1Heat deep inside Earth melts rock into magma.
- 2Magma is lighter than surrounding rock, so it rises.
- 3Dissolved gases build pressure as it nears the surface.
- 4When pressure overcomes the crust, magma erupts as lava and ash.
Frequently asked questions
- What causes a volcano to erupt?
- Rising magma and the pressure of trapped gases force molten rock up through a weak point in Earth's crust.
- Where do volcanoes usually form?
- Mostly along the edges of tectonic plates, where the crust is cracked and magma can rise.
- What's the difference between magma and lava?
- Magma is molten rock underground; once it erupts onto the surface, it's called lava.