Deep sea explosive eruptions may be not so different from subaerial eruptions

Gianluca Iezzi,Guido Ventura,Salvatore Passaro,Patrizio Signanini,Stella Tamburrino,Gabriele Lanzafame,Lucia Mancini,Harald Behrens,Mattia Vallefuoco

doi:10.1038/s41598-020-63737-7

Abstract

The dynamics of deep sea explosive eruptions, the dispersion of the pyroclasts, and how submarine eruptions differ from the subaerial ones are still poorly known due to the limited access to sea environments. Here, we analyze two ash layers representative of the proximal and distal deposits of two submarine eruptions from a 500 to 800 m deep cones of the Marsili Seamount (Italy). Fall deposits occur at a distance of more than 1.5 km from the vent, while volcanoclastic flows are close to the flanks of the cone. Ash shows textures indicative of poor magma-water interaction and a gas-rich environment. X-ray microtomography data on ash morphology and bubbles, along with gas solubility and ash dispersion models suggest 200–400 m high eruptive columns and a sea current velocity <5 cm/s. In deep sea environments, Strombolian-like eruptions are similar to the subaerial ones provided that a gas cloud occurs around the vent.

Highlights

MS represents the axial ridge of the 2 Ma old Marsili back-arc oceanic basin, which is associated to the Calabrian Arc-Ionian Sea subduction system[19] (Fig. 1a)
A general decrease in grainsize occurs in MS1 and MS2 moving from CORE02 to Marsili[1]
The MS1 and MS2 ashes show very similar 3D bubble textural parameters. These parameters include the number of bubbles per unit volume (#/vol.), average volume of www.nature.com/scientificreports bubbles (AV), average aspect ratio (AAR), average sphericity (AS), specific surface area (SSA), integral of mean curvature (IMC), elongation index (EI) and isotropy index (I)

Summary

Introduction

MS (volcanic activity: 1 Ma to 2–3 ka BP) represents the axial ridge of the 2 Ma old Marsili back-arc oceanic basin, which is associated to the Calabrian Arc-Ionian Sea subduction system[19] (Fig. 1a). The sources of the MS1 and MS2 eruptions are represented by three NNE-SSW aligned cones having summits around 670 m b.s.l. and located at a distance of about 700 and 1600 m from the proximal (CORE02) and distal (Marsili1) sites, respectively[17] (Fig. 1c). This stratigraphic appraisal is unprecedented for deposits of deep submarine eruptions, and allows us to analyze the spatial variation of two tephra layers at different distance from the source(s) This stratigraphic appraisal is unprecedented for deposits of deep submarine eruptions, and allows us to analyze the spatial variation of two tephra layers at different distance from the source(s) (Figs. 1c and 2)

Objectives

Methods

Results

Conclusion