A Strombolian eruption is a type of volcanic eruption characterized by a moderate to high explosive discharge of viscous lava and gas. This unique eruption style is named after the Italian volcanologist, Giuseppe Stromboli, who first described it during his observations of the eponymous volcano in the early 19th century.
Since then, numerous other volcanoes have been found to display this eruptive behavior, including Mount Etna in Italy, Mount Yasur in Vanuatu, and Kilauea on Hawaii’s Big Island. While each Strombolian volcano has its own distinct characteristics, they all share certain commonalities that make them easily recognizable as belonging to this class of eruptions.
The most distinguishing feature of a Strombolian eruption is the presence of voluminous amounts of gas bubbles within the molten lava. As these gases escape from the magma column, they create an explosive force that propels fragments of hot rock and ash high into the air. The resulting plume can often be seen for many kilometers around the vent and may even reach altitudes approaching 10 km (32,800 ft).
Another key aspect to consider when identifying a Strombolian eruption is the relatively short duration over which it takes place. Unlike other types of eruptions that can go on for hours or even days at a time, Strombolian activity tends to be much more sporadic and briefer in nature. It is not uncommon for several individual explosions to occur within minutes or even seconds of one another.
The size and intensity of these blasts can also vary considerably from one event to the next. Some may only expel small rocks and ash while others can hurl large boulders several meters into the air. The largest known example occurred at Italy’s Mt. Vesuvius in AD 79 when an estimated 100 million tons (91 million metric tons) of material was ejected from the crater over just two days!
The vast majority of Strombolian eruptions are classified as “low-viscosity” events due to their relatively low silica content (<52%). This makes them less sticky than other types of lava flows and allows them to readily fragment when exposed to heat and pressure release (as opposed to solidifying into a single mass). The result is an eruption composed mostly (80-95%)of fragmented rock debris with only a minor component (<20%)of fluid lava being expelled from the vent.