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eruptions are not regarded as being very threatening. Stromboli, the volcano off the west coast of Italy
after which the type is named, is known as the ‘lighthouse of the Mediterranean’ because it erupts most of the time, and the glowing lumps of lava – called volcanic or lava bombs – that it thows out can be seen from offshore by night.
Strombolian eruptions, and all of the eruptions listed below, contribute to the steep-sided cones that are called stratovolcanoes.
Vulcanian type
The vulcanian type of eruption is named after the Italian volcano Vulcano. It is more violent than the Strombolian type and is the first type to produce ash. Eruptions occur less often than in Strombolian; and when they occur, they are more violent, with clouds of gas and ash being thrown out in the form of a dark, swirling cloud over the volcano. The ash clouds, however, are not sent high into the atmosphere, and the ash does not travel very far.
Pelean type
The pelean type is a violently explosive eruption in which clouds containing red-hot pieces of lava, together with gases, form a dense fluid that rolls down the side of the volcano, rather like a burning avalanche. The flow can exceed 100 km/hr. The original term used for such fast- moving, ground-hugging clouds was nuée ardente, but the term pyroclastic flow is also widely used by geologists today. The first such eruption to be recorded was on Mount Pelée on the Caribbean island of Martinique in 1902. One of the most recent was the eruption
of Mount Saint Helens in the northwestern United States in 1980 (see page 55).
The majority of material erupted is gas and ash, not runny lava. A nuée ardente can travel for tens of kilometres. The density of the ash cloud is such that it can flatten most things in its path.
Plinian type
(Below) The Pelean type of eruption.
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