The marine vo
lcanic
lastic system extending to 3 km water depth on the northwest
flank o
f Strombo
li vo
lcano has been surveyed using seismo-acoustic pro
fi
ling, mu
ltibeam bathymetry, deep-towed
long-range side-scan sonar imaging and box-core samp
ling. Deposits and sea-
floor topography record repeated
flank co
llapses that have occurred during the
last 13 ka and created the present Sciara de
l Fuoco scar. An extensive (170 km
2) debris-ava
lanche deposit characterized by subdued hummocks (megab
locks) is buried by turbidites
formed
from gravity currents that originated in Sciara de
l Fuoco. The currents were main
ly de
flected a
long the margin o
f the ava
lanche deposit, but a
lso spi
lt over onto it. The turbidites re
flect topographic
flow stripping and their thinning towards s
light
ly steeper s
lopes indicates that some materia
l that sett
led there drained
further downs
lope as secondary higher concentration
flows. The estimated vo
lume o
f the entire
fan-shaped bu
lge amounts to 12 ± 2.5 km
3, about 3.5 km
3 o
f which is attributed to the post-co
llapse sedimentation. The remaining 8.5 ± 2.5 km
3 is in the order o
f the vo
lume computed
for the materia
l removed by the mu
ltip
le sector co
llapses that a
ffected the NW Strombo
li
flank. Two units are identi
fied in the dista
l part o
f the bu
lge, through the recognition o
f their
fronts, and these indicate a
layered structure
for successive debris-ava
lanche deposits.
Granulometric and particle-type characterization of seabed samples shows clast population evolution with sedimentary transport distance, from the main entrance point of debris in Sciara del Fuoco, to the confluence with the Stromboli Canyon, and into the Marsili Basin some 45 km from the island. Changes in particle populations are due to selective sedimentation and also mixing with a wide range of terrigenous detritus brought by currents that descended the main Stromboli Canyon from the continental shelf. Abundant fine sand and silt is produced at the volcano and occurrence of mainly coarse-grained material along the channel to the Marsili Basin indicates that a considerable volume of volcaniclastic material from Stromboli lies in the sedimentary succession accumulating on the distal basin floor, where a deep-sea fan is growing.