It is estimated that approximately 50 to 60 volcanoes erupt globally every month. Some volcanoes, such as Kilauea, are almost continually active. Other volcanoes only erupt once every few decades.
Many volcanic eruptions last for hours, though some may go as long as days or weeks. Even when the eruption stops, it is still considered active. It takes approximately 10 years after an initial eruption for the volcanic eruption to be considered completed, though it could take more than 100 years for the volcano to cool. Volcanoes typically have a life span of several thousand years. During an eruption, volcanoes release ash first, followed by lava.