The Holocene syneruptive volcaniclastic debris flows in the Vesuvian area: Geological data as a guide for hazard assessment
Published:January 01, 2006
Roberto Sulpizio, Giovanni Zanchetta, Federica Demi, Mauro A. Di Vito, Maria T. Pareschi, Roberto Santacroce, 2006. "The Holocene syneruptive volcaniclastic debris flows in the Vesuvian area: Geological data as a guide for hazard assessment", Neogene-Quaternary Continental Margin Volcanism: A perspective from Me´xico, Claus Siebe, José Luis MacíasGerardo, J. Aguirre-Díaz
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Volcaniclastic debris flows generated in drainage basins of the Apennine mountains of southern Campania in response to pyroclastic fall deposition from four Holocene eruptions of Somma-Vesuvius: Avellino (3.8 ka), A.D. 79, A.D. 472, and A.D. 1631. These syneruptive debris flows are lithologically homogeneous and contain more than 90% of material from the parental eruption. They differ from inter-eruptive debris flows recognized in the area, which contain mixed lithologies of juvenile material (i.e., volcanic material from different eruptions). Diffuse rill erosion generated fines-rich volcaniclastic flows (mudflows), whereas partial saturation of coarse ash and lapilli generated coarser-grained debris flows. Lithofacies analysis shows that debris flows predominate versus hyperconcentrated flows and normal stream-flow deposits. Debris-flow deposits are massive, matrix supported, and have a gravelly-sandy texture. Large blocks are scarce due to their absence in the pyroclastic source material. Lithofacies association indicates that volcaniclastic debris-flow deposits aggraded rapidly by superimposition of different surges that spontaneously developed within the flow. Bulk-flow density ranges from 1840 to 2260 kg/m3 (mean 2035 ± 207 kg/m3).
Geological data supported some considerations of hazard assessment in the study area and indicate that the syneruptive volcaniclastic flows stopped distally on active alluvial fans.