Photograph by J.W. Ewert on 5 October 1998

Vulcanian eruption

A vulcanian eruption is a type of explosive eruption that ejects new lava fragments that do not take on a rounded shape during their flight through the air. This may be because the lava is too viscous or already solidified. These moderate-sized explosive eruptions commonly eject a large proportion of volcanic ash and also breadcrust bombs and blocks. Andesitic and dacitic magmas are most often associated with vulcanian eruptions, because their high viscosity (resistance to flow) makes it difficult for the dissolved volcanic gases to escape except under extreme pressure, which leads to explosive behavior.

Photo: Eruption column caused by a vulcanian-type explosive eruption rises above Tavurvur Volcano in Rabaul Caldera, Papua New Guinea.

Did you know?

• Vulcanian eruptions are named for Vulcano, one of the Aeolian Islands north of Sicily. In fact, the word volcano itself comes from this island, home to the Greek god of fire, Hephaestus (called Vulcan by the Romans).
• Other volcanoes that have recently shown vulcanian behavior include Sakurajima in Japan (ongoing) and Irazu in Costa Rica (1965).