A vulcanian explosion producing a dense cloud of ash and rock fragments ejected from the crater. Blocks impacting on the upper slope leave dust trails. (Photo: Tom Pfeiffer)
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Volcanic Ash Advisory Centres
: Much current eruption news is provided by the 9 Volcanic Ash Advisory Centres (VAAC) distributed around the globe. The VAACs provide a vital service for aviation safety.
: A third tectonic setting where volcanism occurs is believed to be the result of mantle plumes and not directly related to plate boundaries. So called hot spot volcanoes fall into this category.