Interpretation of data from the monitoring thermal camera of Stromboli volcano (Aeolian Islands, Italy)

Twenty eruptive events from the Northeast Crater of Stromboli volcano recorded by a
thermal monitoring camera in early 2004 were analysed in order to understand the eruptive dynamics.
Selected eventswere chosen to be typical of explosions that characterize the steady activity of Stromboli
in terms of jet height and duration. Most of the explosions consisted of clast-rich single bursts,
originating from the same vent inside the Northeast Crater. Conspicuous ash emission was scarce.
Eruptions were preceded by the flashing of a perturbation wave characterized by low temperatures and
an average propagation velocity of about 35–100 m s−1. This perturbation was thought to be caused
by the bursting of the gas slug at the bottom of the crater and is interpreted as an air wave. This was
immediately followed by the expansion of a jet of ‘hot’ gas and particles, at a velocity of 35–75 m s−1.
Ejecta coarser than 138 cm appeared ∼1.6–2 s after the onset of the explosion, moving at a variable
velocity (30–60 m s−1). Eruptive events were either vertical or inclined 7–13◦ towards the NNW. This
inclination is thought to be a consequence either of the morphology of the conduit, following modest
rock falls that partially obstructed the uppermost part of the crater, or of the displacement of the
internal conduit due to the explosive activity of the volcano. The instability of the summit area is a
further possible cause of the deformation of the conduit.

This work was partially funded by
the Istituto Nazionale di Geofisica e Vulcanologia and the
Dipartimento della Protezione Civile, Italy, project INGVDPC
V2

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