The Southeast Crater (SEC) complex seen from south on 14 December 2011. The "old" SEC cone, last active in May 2007, is in the center, showing a conspicuous area of fumarolic activity and yellow sulfur deposits on its upper eastern flank. At left is the low cone of the "Sudestino" ("little southeast"), which grew during several paroxysmal eruptive episodes in the spring of 2000 at the southern base of the "old" SEC cone. The right half of the image is occupied by the New SEC cone, whose has grown entirely during the previous 10 months. The large bombs and blocks in the foreground, with some clasts 3-5 m in diameter, were deposited during the paroxysmal episode of 15 November 2011. Mosaic composed of 3 photos taken by Boris Behncke, INGV-Osservatorio Etneo (Catania)
ETNA
Vapor and ash cloud emitted from the Bocca Nuova during the explosive sequence at 08:07 GMT on 3 December 2011. The Southeast Crater complex is seen below the more advanced, dark, ash-rich portion of the plume, the new cone being at right. Photo taken from south by Giuseppe Distefano and published here with kind permission of the author |
During December 2011, the series of paroxysmal eruptive episodes from the New Southeast Crater (New SEC) was interrupted; a new episode - the first since 15 November 2011 - occurred only on 5 January 2012 (see the January 2012 monthly report). The most significant eruptive event of this month was an explosive sequence at 08:07 GMT (= local time -1) on 3 December, which occurred in the western portion of the Bocca Nuova. This sequence was accompanied by the emission of ash that consisted essentially of pulverized lithic (old) rock, and was deposited on the upper northeast flank of Etna (see report on an analysis of the 3 December 2011 ash - in Italian). Moreover, during the whole month, the usual deep-seated explosions within the conduit of the Northeast Crater have continued, though with fluctuations in their frequency and intensity; this has been accompanied by strong degassing and rumbling sounds audible from the crater rim. |
As part of the work of the Laboratory of Cartography of the INGV-Osservatorio Etneo, a field survey was carried out on 14 December 2011 in the summit area, aiming at obtaining up-to-date topographical data on the New SEC cone and the crater itself, following the sequence of paroxysmal episodes since January 2011. During the survey, two Leica CS10 GPS and one pair of Leica laser binoculars were used for the measurement at distance of volcanic morphologies.
During the survey, the floor of the New SEC was seen to be completely obstructed, and much of the inner crater walls, in particular those toward NW, were cut by numerous fracture systems. GPS measurement were made from a distance near Torre del Filosofo and at Belvedere (1 km south and 0.9 km southeast of the New SEC, respectively), allowing to acquire a series of measurement points along the base and flanks of the new cone, and the rim of the crater. Furthermore, two kinematic GPS (continuous recording) surveys were carried out climbing to the top of the cone and along the southern to eastern base of the cone. These surveys have revealed that the highest point on the crater rim, on its southern side, stood at an elevation of about 3200 m above the sea-level, and thus 200 m above the pre-January 2011 elevation.
A panoramic view taken from the southern rim of the New SEC cone, 14 December 2011. Note the crater floor obstructed with debris, and the fracture systems cutting through the northwestern (opposite) inner wall of the crater. The "old " SEC cone is seen at left. Mosaic composed of 10 photographs taken by Boris Behncke, INGV-Osservatorio Etneo (Catania)
A panoramic view over the New SEC seen from the eastern flank of the "old" SEC cone, 14 December 2011. Note the presence of two conspicuous fumaroles in the northern wall of the crater (in the center), and another fumarole in the southern wall, below the highest point of the cone (3200 m, at right). Mosaic composed of 7 photographs taken by Boris Behncke, INGV-Osservatorio Etneo (Catania)
STROMBOLI
Stromboli volcano is in a state of persistent eruptive activity, normally with explosions of medium to low intensity occurring from a number of vents located within the summit crater. During December 2011, the activity continued at fluctuating levels, , and with frequent episodes of spattering, in particular on the morning of 10 December. The activity was concentrated at the two active vent areas, in the northern and southern sectors of the crater terrace; the spattering episodes occurred in the southern area and did not lead to the formation of any lava flows.