When a large amount of emotions, typically rage, is contained in a volcano. Typically rage is stored in a bottle-like container and then tossed into the owner's volcano. Levels of rage continue to increase until a maximum rage level is reached. When this peak level is reached, the owner of the rage volcano promptly explodes in a fury of uncontrollable rage. The levels of rage volcanoes can vary, and typically is created by douchebags or just general jerks.
Just keep bottling it in your rage volcano, one day you will just go BAM!