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.
|Eruption column caused by a vulcanian-type explosive
eruption rises above Tavurvur Volcano in Rabaul Caldera, Papua New
Guinea. Credit: J. W. Ewert / U.S. Geological Survey
AND PLANETARY SCIENCE
Source: U.S. Geological Survey