It can burst into action several times each year.
Sicily's Mount Etna continued to rumble for hours after its first eruption in more than a year.
Etna's last major eruption took place in 1992, where lava streams endangered the Zafferana village nearby. The lava flows started Monday night.
The volcano's eruptions have been known to last anywhere from days to weeks.
Giant fountains of lava could be seen sprouting from the volcano, located on the isle of Sicily, as far away as Catania, around 30 kilometres away, and the resort town of Taormina.
By Tuesday evening, the eruption was easing.
Plumes of smoke and ash erupt from Mount Etna on October 30, 2002.
Authorities said that towns along the mountain's slopes are not threatened by the explosion. A team of USA marines lent a hand during the aptly named Operation Volcano Buster, dropping concrete blocks at the edge of the lava tunnel to plug the hole.
Catania airport was operating normally today, even though volcanic ash clouds can cause flight disruptions, as much of Europe learnt when Iceland's Eyjafjallajökull erupted in 2010.