Relating the impact of hazards from volcanic eruptions to the type of volcano

Abstract

This study has attempted to compare and contrast both primary and secondary hazards from two distinct types of volcanoes; shield and composite volcanoes. A specific example of each type of volcano: Kilauea, in Hawaii (a shield volcano) and Mount Etna, Sicily (a composite volcano) was used in this study and their eruption statistics summarised from the online database in the Global Volcanism Programme (Smithsonian Institute). The formation and structure of both types of volcano are shown to be closely linked to the local chemistry of magma. Also, it is shown that the magma chemistry has an important bearing on the energy density of the magma for eruptions in terms of a specific difference in the volume of dissolved gases, found to be lower in rock type basalt (shield volcanoes) and higher in rock type rhyolite (statovolcanoes). This is shown to relate closely to the Volcanic Explosivity Index (VEI), with Kilauea, a basalt shield volcano, having a typical VEI of 0, whilst the Mount Etna rhyolite volcano has a typical VEI of 2-3. A survey of the primary hazards (lava, ash fall and pyroclastic flow) and secondary hazards (tsunami, atmospheric effects of ash and dust, lahars and landslides) from both types of volcanoes is undertaken and also related to the chemistry of the magna. The impacts of the hazards have been categorised as one of three classes; either local (close to the source volcano), regional (in the same continent as the volcano) or global.