The 9th paroxysm of the New SE crater on 3 April 2013Sezione di Catania - Osservatorio Etneo reported that on 3 April, after almost 18 days of relative quiet, the New Southeast Crater (NSEC) of Etna produced its ninth episode of lava fountaining. Activity had increased on 2 April when small grayish-brown puffs rose from NSEC. Cloud cover prevented further visual observations through the following night; however, sporadic glow suggested Strombolian activity.
On the morning of 3 April, the volcanic tremor amplitude slowly increased and was accompanied by numerous explosion signals. Field observations revealed that at 1330 vigorous Strombolian activity was occurring at one or two NSEC vents, with jets of pyroclastic material rising up to a few tens of meters above the crater rim. The activity progressively intensified between 1400 and 1430, with frequent, powerful Strombolian explosions often generating loud bangs and launching great quantities of incandescent bombs (with diameters of many meters) onto the flanks of the cone. Shortly after 1435, ash emission started from the saddle vent (SV), followed a few minutes later by Strombolian explosions from the same vent. At 1450, a continuous jet of incandescent lava fountained up to 100 m, whereas the vents within NSEC continued to produce powerful loud explosions. At around 1505 a lava flow moved through the deep breach in the SE rim of NSEC and then traveled over the W rim of the Valle del Bove. During the same time interval, lava emissions started from SV, feeding a flow that went S.
Since 1430 the eruptive plume drifted SE and contained modest amounts of volcanic ash. At around 1540 ash emissions progressively increased and the volcanic tremor amplitude showed a rapid rise. Between 1540 and 1615 low lava fountaining continued from SV, whereas the vents within NSEC emitted intermittent, pulsating lava fountains. The incandescent jets from the vents within NSEC rose up to 400 m above the crater rim. At 1615, lava fountaining at SV intensified, with jets rising 400-500 m high. Explosions from the vents within NSEC continued, producing loud detonations every 1-2 seconds.
Lava fountaining significantly decreased between 1625 and 1628 when a new eruptive vent (NV) opened a few tens of meters to the W of SV, on the E slope of the old SEC cone, and emitted grayish-brown ash. A dense cloud of pyroclastic material emitted by NSEC vents and SV rose about 2 km high and drifted SE. Fallout of pyroclastic material affected almost the same area that had already been subjected to the heavy shower of lapilli on 16 March: Zafferana Etnea and Santa Venerina on the SE flank, and the N part of Acireale plus a number of smaller villages to the N at the S margin of Giarre, in the Ionian area. The deposit was thinner than that of 16 March, and the dimensions of the lapilli were notably smaller.
Between 1630 and 1640, the eruptive activity reached a new peak of intensity with sustained lava fountains from SV and powerful explosions from the vents within the NSEC. At 1637 a thermal surveillance camera recorded a pyroclastic flow from the NE flank of the NSEC cone. Two lava flows emerged from the same area and traveled toward the Valle del Bove.
After 1640, lava fountaining activity showed a rapid decrease, followed by a long series of explosions heard many tens of kilometers away, vibrating doors and windows on the E flank. During this phase, a second pyroclastic flow from the NE flank of the NSEC cone traveled about 1.5 km. The series of strong explosions at the conclusion of the paroxysm lasted until about 1705; subsequently, brown ash continued to be emitted from the SV and NV vents, eventually followed by dense volumes of white vapor. After nightfall, the lava flows emitted during the paroxysm were still brightly incandescent, and slow lava emission continued from several vents on the S and NE sides of the cone. All lava emissions ceased on 4 April.
Source: INGV Catania / Smithsonian / USGS Weekly Volcanic Activity Report