Classification, landing distribution, and associated flight parameters for a bomb field emplaced during a single major explosion at Stromboli, Italy

We propose a novel approach to studying a ballistic bomb deposit. Favorable circumstances,
a unique dispersal axis, an operational thermal video camera, and application of an innovative
methodology allowed estimates of volume and mass erupted, and defi nition of mass partitioning
between bombs of various sizes. This allowed the creation of a multidisciplinary database
for a single major explosion at Stromboli volcano (Italy), the type locality of Strombolian
eruptions. The dispersion and direction of the deposit were consistent with a major explosion
on 21 January 2010. Field data comprised 780 mapped bomb locations and sizes, and were
organized into a GIS with a lidar-derived digital elevation model as its base. This allowed us
to defi ne the landing distribution and fl ight parameters for erupted bombs. The data defi ned
discontinuous deposition to build a cluster-dominated bomb fi eld, with a total deposit volume
of ~10 m3, a mass of ~2 × 104 kg, and a grain size dominated by large bombs (1 m in diameter).
The parameters defi ned here for a major eruption at Stromboli show that the Strombolian
style of volcanism, and its deposits, need to be treated carefully, and a different approach
is needed in the future to truly characterize and classify such small (but globally common)
explosive eruptions. The recognition that sedimentation from such eruptions will be uneven
leads to the important conclusion that isopachs and isopleths cannot be used to estimate eruption
volumes for such explosions.

U.S. National Science Foundation grant
EAR-0738106

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