Volcanoes are huge, mountain like shapes that can erupt lavaout.  They can destroy anything that the lava get in the way. Inside of them, there are chambers of magma. If too much magma get inside the chambers, an eruption might happen.
Volcanoes can also spread ash.  Some buried citites found were buried by ash, mummifing some bodies.

Today scrientist watch on volcanoes, trying to predict when they might erupt.