Very shallow dyke intrusion and potential slope failure imaged by ground deformation: The 28 December 2014 eruption on Mount Etna

Abstract

On 28 December 2014, eruptive activity resumed at Mount Etna with fire fountain activity feeding two lava flows on the eastern and southwestern upper flanks of the volcano. Unlike all previous summit activity, this eruption produced clear deformation at the summit of the volcano. GPS displacements and Sentinel‐1A ascending interferograms were calculated in order to image the ground deformation pattern accompanying the eruption. The displacements observed by GPS depict a local ground deformation pattern, affecting only the upper part of the volcano. Despite snow cover on the summit, differential interferometry synthetic aperture radar (DInSAR) data allowed obtaining more detail on the ground deformation pattern on the upper eastern side of the volcano. Three‐dimensional GPS displacements inversion located a very shallow NE‐SW intrusion just beneath the New Southeast Crater. However, this model cannot justify all the deformation observed by DInSAR thus revealing a gravitational failure of the lava flow field.

The continuing story of Etna's New Southeast Crater (2012–2014): Evolution and volume calculations based on field surveys and aerophotogrammetry

“…December 2014, during which two eruptive fissures opened on the southwestern and northeastern flanks of the NSEC cone (Bonforte and Guglielmino, 2015), and the upper portion of the cone, which had been built up during E48 (June 2014) and E50 (August 2014) was destroyed. Much of the explosive ac i i a co ce ra e a a e l i i e " a le" e ee e C co e a e ol o ea…”

Topographic Maps of Mount Etna’s Summit Craters, updated to December 2015

“…The upper eastern flank of the NSEC has a new pit, some tens of meters wide, with a fan of lava flows from its base spreading eastwards, towards the Valle del Bove. Between the summit of SEC and NSEC, an ellipsoidal crater represents the highest feature of an ENE-WSW fissure opened in December 2014 (Bonforte & Guglielmino, 2015) and reactivated several times during 2015.…”

Why Does a Mature Volcano Need New Vents? The Case of the New Southeast Crater at Etna

“…Indeed, the shift of the location of volcanism from the SEC to the NSEC is not only significant from a structural point of view, as it also changes, probably increasing, the context of volcanic hazards at the volcano. In particular, the growth of a new cone on the western rim of the Valle del Bove may promote further instability (as recently observed; Bonforte and Guglielmino, 2015), both of the cone itself and of the slope upon which it rests, which by now have merged into a continuum. Repeated intrusion of magma through the flanks of the cone, especially in its eastern sector, has in fact led to small to moderate size collapse events in late-2013 and early 2014; the largest of these events, on 11 February 2014, entrained hot, active lava, resulting in a hot, pyroclastic-flow-like avalanche.…”

“…Finally, during 2014-2015, dilatation reappeared, but it affected mostly the southern portion of the summit area, with a NW-SE orientation ( Figure 5J). This may have prepared the ground for the NE-SW-striking dike intrusion accompanying the paroxysmal episode at the NSEC on 28 December 2014 (Bonforte and Guglielmino, 2015).…”