A volcano in a dream usually points to anger or emotion you've kept suppressed for so long that pressure has quietly built underneath it. A dormant volcano can reflect feelings you're still managing to contain, while one erupting often names a moment where suppressed emotion is finally breaking through despite your effort to hold it.
Let the Moon be increasing in light, and free from the aspects of the infortunes, when you would cure sore eyes. - William Lilly (1602.-1681.)