Vulcanian Eruptions

Vulcanian eruptions, however, are more complex to classify. Vulcanian eruptions were first distinguished by Mercalli and Silvestri (1891) who noticed that the 1888-1890 eruption of Vulcano in the Aeolian Islands was somewhat different from eruptions of nearby Stromboli volcano. Both volcanoes produced small to moderate scale, short-lived intermittent explosions, but explosions of Vulcano were louder, perhaps due to shock waves, eruption clouds were darker in color (almost black due to the presence of abundant ash), and ejected material had lower temperatures (few or no glowing ejecta were visible during daytime). The morphology of the juvenile products indicated higher viscosity and lower vesicularitymagma at Vulcano; ballistics ranged from “bread-crust bombs” to dense, angular, glassy blocks. Mercalli thus suggested that Vulcanian activity is typical for magmas of intermediate composition.