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Abstract
The July–August 2001 eruption of Mt. Etna stimulated widespread
public and media interest, caused significant damage to tourist facilities,
and for several days threatened the town of Nicolosi on the S flank
of the volcano. Seven eruptive fissures were active, five on the S flank
between 3,050 and 2,100 m altitude, and two on the NE flank between
3,080 and 2,600 m elevation. All produced lava flows over various periods
during the eruption, the most voluminous of which reached a length of
6.9 km. Mineralogically, the 2001 lavas fall into two distinct groups,
indicating that magma was supplied through two different and largely
independent pathways, one extending laterally from the central conduit
system through radial fissures, the other being a vertically ascending
eccentric dike. Furthermore, one of the eccentric vents, at 2,570 m
elevation, was the site of vigorous phreatomagmatic activity as the
dike cut through a shallow aquifer, during both the initial and closing
stages of the eruption. For 6 days the magma column feeding this vent
was more or less effectively sealed from the aquifer, permitting powerful
explosive and effusive magmatic activity. While the eruption was characterized
by a highly dynamic evolution, complex interactions between some of
the eruptive fissures, and changing eruptive styles, its total volume
(~25×106 m3 of lava and 5–10×106 m3 of pyroclastics)
was relatively small in comparison with other recent eruptions of Etna.
Effusion rates were calculated on a daily basis and reached peaks of
14–16 m3 s-1, while the average effusion rate at all fissures
was about 11 m3 s-1, which is not exceptionally high. The eruption
showed a number of peculiar features, but none of these (except the
contemporaneous lateral and eccentric activity) represented a significant
deviation from Etna's eruptive behavior in the long term. However, the
2001 eruption could be but the first in a series of flank eruptions,
some of which might be more voluminous and hazardous. Placed in a long-term
context, the eruption confirms a distinct trend, initiated during the
past 50 years, toward higher production rates and more frequent eruptions,
which might bring Etna back to similar levels of activity as during
the early to mid seventeenth century.
Keywords: Mt.
Etna, 2001 eruption, Lava flow-field evolution, Central-lateral vs.
eccentric activity, Phreatomagmatism, Eruption dynamics
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