Research Article

Bulletin of Volcanology

, Volume 70, Issue 10, pp 1249-1268

Pyroclastic density currents resulting from the interaction of basaltic magma with hydrothermally altered rock: an example from the 2006 summit eruptions of Mount Etna, Italy

  • B. BehnckeAffiliated withIstituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania Email author 
  • , S. CalvariAffiliated withIstituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania
  • , S. GiammancoAffiliated withIstituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania
  • , M. NeriAffiliated withIstituto Nazionale di Geofisica e Vulcanologia, Sezione di Catania
  • , H. PinkertonAffiliated withDepartment of Environmental Science, Lancaster Environment Centre, Lancaster University

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Abstract

After 16 months of quiescence, Mount Etna began to erupt again in mid-July 2006. The activity was concentrated at and around the Southeast Crater (SEC), one of the four craters on the summit of Etna, and eruptive activity continued intermittently for 5 months. During this period, numerous vents displayed a wide range of eruptive styles at different times. Virtually all explosive activities took place at vents at the summit of the SEC and on its flanks. Eruptive episodes, which lasted from 1 day to 2 weeks, became shorter and more violent with time. Volcanic activity at these vents was often accompanied by dramatic mass-wasting processes such as collapse of parts of the cone, highly unusual flowage processes involving both old rocks and fresh magmatic material, and magma–water interaction. The most dramatic events took place on 16 November, when numerous rockfalls and pyroclastic density currents (PDCs) were generated during the opening of a large fracture on the SE flank of the SEC cone. The largest PDCs were clearly triggered explosively, and there is evidence that much of the energy was generated during the interaction of intruding magma with wet rocks on the cone’s flanks. The most mobile PDCs traveled up to 1 km from their source. This previously unknown process on Etna may not be unique on this volcano and is likely to have taken place on other volcanoes. It represents a newly recognized hazard to those who visit and work in the vicinity of the summit of Etna.

Keywords

Mount Etna Pyroclastic density currents Lava–water interaction Hydrothermal alteration Hazards Volcano instability 2006 eruption