Classification of Volcanic Eruptions » Vulcanian Eruptions

In a Vulcanian-type eruption, the high viscosity of the magma makes it difficult for the dissolved volcanic gases to escape except under extreme pressure. This leads to the characteristic behavior where a dense cloud of ash-laden gas explodes from the crater and rises high above the peak. Steaming ash forms a whitish cloud near the upper level of the cone. These moderate-sized explosive eruptions commonly eject a large portion of volcanic ash as well as bombs and blocks (see for more information).

Houses buried in volcanic ash up to their first-floor windows in a town near the Chaiten volcano. The volcano plume is in the background.

International Space Station view of Sarychev Volcano (Kuril Islands, northeast of Japan) in an early stage of eruption on June 12, 2009. Ash from the multi-day eruption was detected along the main air routes between East Asia and North America, and commercial airline flights were diverted away from the region to minimize the danger of engine failures from ash intake. (NASA)