Sicily (HDW) November 26, 2002 - The
2002 Mt. Etna flank eruption that began on 27th October is continuing,
after almost a month of activity. During this period several distinct
phases of eruptive style have been observed. The first phase of the eruption
ended on 5th November, when lava flows from the northern fissure stopped.
Strombolian and fire-fountaining activity continued at the southern fissure,
localised within the 2750 m elevation cinder cone that formed during early
November. Lava jets reached heights of over 300 m above the crater, forming
an ash column that spread mostly N, due to the strong wind, and reached
an elevation of 4.7 km a.s.l.
The second phase of activity started on 12th November, when strong jets
and continuous emission of ash gave way suddenly to mild Strombolian activity.
Lava flows began to spread SW from the 2750 m vent on the 13th November.
These flows ran parallel to the October flows towards Monte Nero and achieved
a maximum length of 4 km on 19th November, stopping just 300 m before
Casa Santa Barbara, at 1770 m a.s.l.. Lava output from the main vent then
declined, and overflows covered the previous flow channel. As of 25th
November the most advanced active flow fronts were located within 1 km
from the vent.
Between 20th and 21st November another new vent opened on the SSE base
of the 2750 m cinder cone. This vent produced a new lava flow that spread
south towards Rifugio Sapienza. The flow length reached 1.9 km on the
22nd, and 2.7 km on the 23rd, covering the Rifugio K. The Rifugio Sapienza
was threatened by the flow, and Civil Protection soon built up two earth
barriers to divert the lava towards the east of buildings, as in the 2001
eruption. This diversion was once again successful, and the flow eventually
stopped on 24th, a few metres before reaching the SP92 road connecting
Zafferana to Rifugio Sapienza, after having travelled 3.6 km from the
main vent.
Early on the 25th November, two new explosive vents opened to the N and
SSE of the 2750 m cinder cone. This caused a shift in explosive activity
from the crater of the previous cone to the newly formed vents, which
produced fire fountaining activity and an ash plume rising to 4.7 km elevation
and spreading north. Immediately afterwards the effusion rate of the south
lava flow (towards Rifugio Sapienza) significantly decreased, and slightly
increased in the southwest flow (towards Casa Santa Barbara). This caused
new overflows above the previous flow channel on the lava flows directed
to Casa Santa Barbara. The low effusion rate did not allow these flows
to reach previous flow lengths, and they were less than 1 km long when
last observed on 25th November. Observation of the flow field was impossible
on the 26 November due to poor weather conditions.
SO2 emission from the volcano is still very high and fluctuating, keeping
within the range of 20,000 to 7,000 tons per day. Taken together, the
high amount of gas released by the volcano, the still high volcanic tremor,
and the explosive activity still ongoing at the south vent, rather suggest
that the eruption may continue for some time.
