The incredible view
of snow on Etna on the evening of 24 July. The building visible in the
image is the Torre del Filosofo mountain hut (at about 2900 m elevation).
A brilliant rainbow is visible at left; the bay of Catania can be seen
in the background.
Update on the activity on 28
July 1999. Etna's summit craters were visited
today by Boris Behncke, Carmelo Monaco and Angelita Rigano (Dipartimento
di Scienze Geologiche, University of Catania) and others. Deep within
the central pit of the NE Crater there were near continuous detonations,
quite a different sound from the continuous, surf-like sound heard in
the same pit early this month. However, no ejecta were thrown to the
height of the rim of the pit, but a dense plume heavily charged with
sulfur dioxide was emitted, making observations of the pit's interior
impossible and rendering the stay on the crater rim highly unpleasant.
Within Bocca Nuova, explosive activity occurred deep within the
two main vents in the northwestern and southeastern parts of the crater.
While no pyroclastics were seen to rise above the rim of the northwestern
vent, the southeastern vent produced near continuous emissions of brownish
ash which became more forceful when loud roaring explosions occurred
at depth. The most impressive activity occurred at the Voragine
whose central vent produced powerful explosions and at times prolonged
fountains of incandescent bombs, some of them up to one meter across.
Some of the explosions were quite violent, ejecting bombs to about 100
m above the crater rim. No ejecta fell outside the crater, and only
a few fresh bombs, probably ejected a few days ago, were found on the
western crater rim, about 150 m from the active vent. Within the crater,
however, bombs had fallen abundantly, especially in the northern part
of the crater floor, so that any approach to the vents across the crater
floor is absolutely impossible. Many eruptions were accompanied by acute
roaring noises indicating high-pressure gas emission from the top of
the magma column in the vent, which has risen by tens of meters since
last observed directly on 6 July. There was apparently no eruptive activity
within the "diaframma vent". No direct observations were made
at the SE Cone which is believed to be inactive for the moment.
At the 4
February fissure, lava emission continues at low rate. One area
of effusive activity lies on the northeastern side of a large tumulus
that has grown about 100 m downslope from the upper hornito cluster
since late June. One narrow (about 0.5-0.8 m) flow issued from a small
effusive vent and flowed through a channel with unusually high walls
(up to 1 m above the flow surface) while a much larger flow broke through
the southern base of the channel wall, feeding a flow 1.5 m wide that
on 24 July 1999. Boris Behncke (Dipartimento
di Scienze Geologiche of Catania University) and Giuseppe Scarpinati
Européenne, Paris) made
an attempt to reach the summit craters
on the afternoon of 24 July. The visit was severely hampered by adverse
weather conditions, and no direct observations of the activity in the
craters could be made. When arriving at the Torre del Filosofo mountain
hut (which stands about 1 km south of the SE Cone) with a group of about
15 tourists, hail began to fall, followed by severe storms and a true
blizzard (this is possible even in July!) accompanied by lightning flashes,
so that everybody had to take refuge in the small wooden shack of the
mountain guides next to the Torre del Filosofo building. While the tourists
were later brought back with the tourist jeeps, Behncke and Scarpinati
and a group of the French organization "Aventure et Volcans"
stayed at Torre del Filosofo, watching the rare spectacle of a snow
fall in July rather than any volcanic activity (a few glimpses of small
lava flows on the active flow-field only 500 m away could be obtained
anyway). At sunset, the whole landscape of Etna's upper 1000 m was bathed
in an eerie gloom, with a strikingly luminous rainbow, Etna's shadow
cast onto a dark wall of thunderstorm clouds, near-continuous snow falls,
and lightning strokes.
Behncke and Scarpinati decided to leave Torre del Filosofo and to return to Acireale, near Catania, when the weather conditions temporarily improved. On their return to the Catania area later that evening, they noted a vivid glow over the summit as the cloud cover had lifted for a brief period, indicating the presence of active lava within either the Bocca Nuova or the Voragine, or both. This is the first time since early February that such a crater glow has been observed, and yet another confirmation that summit activity is increasing, although it is not yet at the levels of last summer.
Update on the activity between
13 and 24 July 1999. There is more evidence
that Etna's summit craters are progressively increasing their activity,
although this increase is not linear. Lava continues to flow from the
4 February fissure at the southeastern base of the SE Cone, but
the amount of lava is relatively small, and short-lived lava flows extend
only a few hundred meters downslope (to the east and southeast) before
Page set up on 27 May 1997, last modified on 6 August 1999