The mean volcanic tremor amplitude at Etna volcano, Italy is showing an increasing trend, the Istituto Nazionale di Geofisica e Vulcanologia, Osservatorio Etneo, reported September 6. Sounds characteristic of Strombolian activity and spattering have been heard this morning at the Bocca Nuova crater.
Since the second half of August, a slow and gradual rise of the mean amplitude has been recorded, which today, on the peripheric stations of the seismic network, has reached values comparable to those seen shortly before the December 2018 eruption, and higher than those observed before the eruptive episodes of May -July 2019.
During the past few days, the volcanic tremor source has remained confined to the summit area, mainly below the Southeast Crater - New Southeast Crater system.
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Conspicuous degassing from Etna's summit craters at daybreak on September 6, 2019, seen from south. Credit: INGV
As for ground deformation, no significant variations are being observed in the trends of the mean-term temporal series, INGV said.
Inclement weather is preventing observation of the activity at the summit craters with the visual and thermal surveillance cameras. However, mountain guides report that the characteristic sounds of Strombolian activity and spattering have been heard this morning at the Bocca Nuova crater.
The photo below shows conspicuous degassing from Etna's summit craters at daybreak on September 6, 2019, seen from south.
Mount Etna, towering above Catania, Sicily's second-largest city, has one of the world's longest documented records of historical volcanism, dating back to 1500 BCE. Historical lava flows of basaltic composition cover much of the surface of this massive volcano, whose edifice is the highest and most voluminous in Italy.
The Mongibello stratovolcano, truncated by several small calderas, was constructed during the late Pleistocene and Holocene over an older shield volcano. The most prominent morphological feature of Etna is the Valle del Bove, a 5 x 10 km (5.1 x 6.2 miles) horseshoe-shaped caldera open to the east.
Two styles of eruptive activity typically occur at Etna. Persistent explosive eruptions, sometimes with minor lava emissions, take place from one or more of the three prominent summit craters, the Central Crater, NE Crater, and SE Crater (the latter formed in 1978). Flank vents, typically with higher effusion rates, are less frequently active and originate from fissures that open progressively downward from near the summit (usually accompanied by strombolian eruptions at the upper end).
Cinder cones are commonly constructed over the vents of lower-flank lava flows. Lava flows extend to the foot of the volcano on all sides and have reached the sea over a broad area on the SE flank. (GVP)
Featured image: Etna on the morning of September 6, 2019. Credit: INGV