For the first time, a 3D model of the geological structure of Etna has been created which provides a new hypothesis on the evolutionary framework of the volcano. The results were disclosed by a study conducted by INGV and the University of Catania, published in Tectonics of the American Geophysical Union
A 3D modeling of the geological structure of Etna has made it possible to calculate, with more precision, the volume of the volcanic edifice and to reconstruct the variation of the eruptive rate over time. It was developed by a team of researchers from the National Institute of Geophysics and Volcanology - Etna Observatory (INGV-OE) and from the University of Catania - Department of Biological, Geological and Environmental Sciences (DSBGA).
The study, Three-dimensional modeling of Mount Etna volcano: volume assessment, trend of eruption rates and geodynamic significance, published in the American Geophysical Union's Tectonics (https:// doi: 10.1002/2017TC004851), also provides a new hypothesis on the evolutionary framework of the volcano, closely connected to the drastic geodynamic changes that have affected eastern Sicily, during the formation and growth of Mount Etna.
A first reconstruction of the morphological and structural setting of the sedimentary basement of Mount Etna had already been developed in a previous work (The morphostructural setting of Mount Etna sedimentary basement (Italy): Implications for the geometry and volume of the volcano and its flank instability,
https://www.sciencedirect.com/science/article/pii/S0040195112007305).
"Starting precisely from the data of the sedimentary basement and from those of the recent geological cartography of the volcano", explains Stefano Branca, volcanologist at INGV-OE, "the volcanic structures that were formed and superimposed starting from the last 3 years and which overall led to the formation of the great strato-volcano of Mount Etna, whose volume is approximately 220.000 km535".
The 3D modeling made it possible to reconstruct the morphological evolution of the volcano during the main growth phases of the Etna edifice, showing the eruptive centers of the Valle del Bove, active between about 110.000 and 65.000 years ago. And he also illustrated the structure that has developed during the last 60.000 years, with the formation of the main eruptive centre, known as the Elliptic volcano, which around 20.000 years ago had reached a height of 3600 m. The volumes emitted in the period of time analyzed made it possible to determine the trend of the eruptive rate of Etna, highlighting a drastic increase in the last 15.000 years, the period in which the current edifice known as the Mongibello volcano was formed.
"The comparison of the average eruptive rates of the individual Etna phases with those of other volcanic systems, located in different geodynamic environments around the world, has shown how in the last 60.000 years, i.e. with the formation of the Ellittico and Mongibello volcanoes, the eruptive rates have reached a value close to that of oceanic arc volcanoes (such as those of the Pacific ring of fire), although Etna is considered a typical intraplate volcano”, continues the volcanologist.
This result is in agreement with some recent studies that have shown a possible evolution of the magmatic source of Etna towards an island arc type volcanism, such as that of the Aeolian Islands.
“In fact, the portion of the subducting crust, under the Calabrian-Peloritan sector and the Tyrrhenian Sea, underwent, during the middle Pleistocene, a laceration which allowed the mantle from the Aeolian arc area to flow southwards into the region of Mount Etna”, concludes Branca.
Extended
Three-dimensional modeling of Mount Etna volcano: volume assessment, trend of eruption rates and geodynamic significance
Giovanni Barreca, Stefano Branca, Carmelo Monaco (2018), Three-dimensional modeling of Mount Etna volcano: volume assessment, trend of eruption rates and geodynamic significance. tectonics, https:// doi: 10.1002/2017TC004851
3D modeling of Mt. Etna, the largest and most active volcano in Europe, has for the first time enabled acquiring new information on the volumes of products emitted during the volcanic phases that have formed Mt. Etna and particularly during the last 60 ka, an issue previously not fully addressed. Volumes emitted over time allow determining the trend of eruption rates during the volcano's lifetime, also highlighting a drastic increase of emitted products in the last 15 ka. The comparison of Mt. Etna's eruption rates with those of other volcanic systems in different geodynamic frameworks worldwide revealed that, since 60 ka ago, eruption rates have reached a value near to that of oceanic-arc volcanic systems, although Mt. Etna is considered a continental rift stratovolcano. This finding agrees well with previous studies on a possible transition of Mt. Etna's magmatic source from plume-related to island-arc related. As suggested by tomographic studies, trench-parallel breakoff of the Ionian slab has occurred north of Mt. Etna. Slab gateway formation right between the Aeolian magmatic province and the Mt. Etna area probably induced a previously softened and fluid-enriched supra-subduction mantle wedge to flow towards the volcano with consequent magmatic source mixing.
Keywords: 3D modeling, Mt. Etna volcano, emitted volumes, eruption rates, slab breakoff, mantle flow, magmatic source mixing.
Figure 1: The northeast crater, taken on March 10, 2018
Figure 2: schematic geological sections (AB) and related 3-D models with NW perspective view of the crust/asthenosphere system under Etna and under the western sector of the Aeolian arc. In (A) the geological setting during the middle-late Pleistocene is represented, a period in which the volcanism of the islands of Alicudi and Filicudi was still active. In (B) the current geological structure is represented which shows the presence of the asthenospheric window between the Etna and the Aeolian areas responsible for the recent contamination between the two magmatic sources