Partly filled with ash of the 2001 and 2002-2003 eruptions but still impressive, the Cisternazza collapse pit yawns in the southeastern part of what used to be called the "Piano del Lago" (the plain of the lake) until the latest eruptions led to the growth of large new pyroclastic cones on the former plain. The Cisternazza formed at the beginning of the 1792-1793 eruption and is a typical though unusually large example of collapse pits forming in the uppermost portions of eruptive fissures of flank eruptions at Etna. In the background (center) lie the two large pyroclastic cones built up during the 2002-2003 eruption, and behind them to the right, the still larger cone of the Southeast Crater, one of Etna's four summit craters. A gas plume is fed from the Northeast Crater, which lies behind the Southeast Crater. View is to the NNW, taken in mid-June 2003

Mamma Etna's countless children
1792-1793 eruptive vents
SSE flank, 15.008144° E, 37.725378° N (Cisternazza);
15.026762° E, 37.707978° N (uppermost effusive vent)
elevation: ~2630 m (Cisternazza); ~2000-1850 m (effusive vents
outside the Valle del Bove)

In late May 1792, a long-lived and voluminous flank eruption began on the upper SSE flank of Etna, initially from vents on the lower Piano del Lago and within the upper southern part of the Valle del Bove. On 1 June of that year, new vents opened outside the Valle del Bove, immediately below its southern crest (known as "Schiena dell'Asino", which means "the back of the donkey") and a little further downslope, between 2000 and 1850 m. A large volume of lava was emitted from the lowermost portion of this system of eruptive fissures, with the most advanced lava fronts coming very close to the village of Zafferana. In spite of the volume of emitted lava, this eruption was almost non-explosive, with only some explosive activity at the beginning of the eruption on the Piano del Lago, where a spectacular collapse pit, the Cisternazza, was formed. The eruption ended late in May 1792, after one year. In some respects it was similar to the 1991-1993 eruption, which also threatened Zafferana and was essentially non-explosive, but this latter eruption was confined to the Valle del Bove.
Many of the 1792-1793 eruptive vents are still well visible today. The Cisternazza, which lies in the southeastern part of the Piano del Lago (or what used to be called Piano del Lago until the eruptions of 2001 and 2002-2003), is a simple circular pit about 200 m in diameter and (before 2001) 70 m deep, and with subvertical walls. Some of its depth probably was lost due to the heavy tephra falls of the 2001 and 2002-2003 eruptions. The first effusive vents to become active, high on the southwest wall of the Valle del Bove, have been buried under the lavas of the 1991-1993 eruption. Outside the Valle del Bove, nearly on the crest of the "Schiena dell'Asino", lies a shallow pit crater about 20 m in diameter, from which a narrow tongue of lava extends about 1.3 km down the slope. At the northern rim of the pit lie the remains of a small scoria or spatter cone, which formed before the nearby pit collapsed, exposing a narrow dike within the remainder of the spatter cone.
Further downslope, about 0.5-0.6 km southeast of the small pit, the main section of the 1792-1793 eruptive fissure system is marked by a series of hornitos, small, steep-sided cones consisting of welded spatter. From here the largest lava flow of the eruption was emitted, which transformed much of Etna's middle southeast flank into a monotonous lava plain. Nowadays the 1792-1793 lava field is covered with some vegetation, and furthermore it is one of the few lava fields on this volcano that has abundant pahoehoe lava surfaces. Two spectacular lava caves lie within this lava field, the Grotta Cassone and the Grotta Tre Livelli, both of which were discovered during the construction of the road that leads from Zafferana to the tourist facilities around the Rifugio Sapienza.
The photos on this page were taken during two visits to the eruptive fissure outside the Valle del Bove in 1998 and 2001, and to the Cisternazza in 2003.

The rising sun is casting long shadows on the SSE flank of Etna on the early morning of 24 May 1998, rendering morphological features well visible. Among these are a small collapse pit (at extreme left), flanked by a half-collapsed mound of scoriae (seen in left foreground), from which a narrow lava flow with low levees extends down the slope. This pit lies immediately to the south of the south rim of the Valle del Bove, here known as "Schiena dell'Asino" (the back of the donkey), and formed during the second phase of the 1792-1793 eruption. Most of the lava produced by this eruption was emitted from vents on both sides of the "Schiena dell'Asino", within the Valle del Bove and on its outer SSE slope. The low cone with a large crater in the right background is Monte Salto del Cane

Geology students from Germany examining the small collapse pit immediately to the south of the Schiena dell'Asino (whose crest is visible in the background in right photograph), where the interior of a small spatter cone is exposed on the pit's rim. The cone formed shortly before the collapse of the pit and is seen to have been fed by a narrow (0.3-0.5 m) dike. Photos taken in early September 2001

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Copyright © Boris Behncke, "Italy's Volcanoes: The Cradle of Volcanology"