Eruptive and emplacement mechanisms of widespread fine-grained pyroclastic deposits on Vulcano Island (Italy) |
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Authors: | G De Astis P Dellino R De Rosa L La Volpe |
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Institution: | (1) Dipartimento Geomineralogico, Università di Bari Campus, Via E. Orabona 4, I-70125 Bari, Italy Fax: +39 80 544 2591 e-mail: lavolpe@mbox.vol.it, IT |
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Abstract: | Tufi di Grotte dei Rossi Inferiori are thick ash deposits, representing the most voluminous stratigraphic unit on Vulcano
Island. The deposits are related to hydromagmatic eruption which occurred under shallow water inside a caldera depression.
Grain-size data and results of SEM investigation allow the character of the transporting medium, solid material concentration
in the cloud during the lateral expansion, and the nature and role of the fluids present at the time of deposition to be constrained.
We suggest that the eruption was characterized by closely timed hydromagmatic pulses giving rise to eruption clouds rich in
water vapor and steam. The coarser material was not significantly transported in the eruptive cloud and it probably deposited
in the caldera depression area. The finer material was extensively transported in the cloud, creating turbulent flows which
surmounted the caldera rim barrier and dispersed in a southward direction, forming widespread deposits in the Piano area.
Lower concentrated flows produced laminated deposits of more limited dispersion, whereas higher concentrated flows formed
more dispersed thicker massive layers.
Received: 26 February 1996 / Accepted: 17 June 1997 |
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Keywords: | Explosive hydromagmatic eruptions Fine-grained massive layers Turbulent flows Vulcano |
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