Types of volcanic eruption. Artwork showing three different types of volcanic eruption: Vulcanian (upper left), phreato-Plinian (lower left) and sub-Plinian (lower right). A Vulcanian eruption is a short, explosive eruption that can produce a large ash cloud. A phreatic (or steam-blast) eruption occurs when a volcanic eruption is mixed with water (in this case, an underwater volcano), producing a violent explosion. A Plinian eruption is a very large volcanic eruption that sends a column of ash high into the atmosphere. If the ash column rises into the stratosphere (around 11 kilometres high), it spreads out to form this mushroom-shaped cloud. Sub-Plinian eruptions fail to reach the stratosphere.