Vulcanian eruption

A Vulcanian eruption is a type of volcanic eruption and is named after the eruption pattern of Vulcano in the Aeolian island of the same name followed by Italy. The term was introduced in 1907 by Giuseppe Mercalli in volcanology.

The pattern consists of short, gunfire -like explosions (with appropriate shock waves) that can occur individually or in series of up to several hours. The strength of the eruption lies at the intersection between a strombolian and an explosive eruption, or about two to four written on the VEI.

Volcanoes that show vulcanian eruptions are eg the Ngauruhoe in New Zealand, Galeras in Colombia and Soufriere Hills on Montserrat.

Ejecta

In the main hochfragmentierte volcanic ash is produced which can rise in an eruption column up to 20 km. In addition, volcanic bombs are often ejected, which can go down up to 5 km in radius.

Typical is higher viscous magma of andesitic to dacitischer composition.

Causes

The causes for this type eruption multiple mechanisms of action are:

The hypothesis concludes that due to the great similarity of the deposits with those of a phreatomagmatic eruption on steam explosion by highly heated groundwater. At Ruapehu in New Zealand in 1995 such outbreaks were observed.

The other hypothesis assumes a separation of volcanic gases under pressure at depths of more than three kilometers, then great by the explosion to break higher. As with the current eruptions of Sakurajima on Kyūshū in Japan.