Volcanoes hold a fascination for human beings and, before they were recorded by literate observer... more Volcanoes hold a fascination for human beings and, before they were recorded by literate observers, eruptions were portrayed in art, were recalled in legend and became incorporated into religious practices: being viewed as agents of punishment, bounty or intimidation depending upon their state of activity and the culture involved. In the Middle East the earliest record dates from the third millennium BCE and knowledge of volcanoes increased progressively over time. In the first century CE
Mount Etna in Sicily (Italy) shows N 2500 years of interactions between volcanic eruptions and hu... more Mount Etna in Sicily (Italy) shows N 2500 years of interactions between volcanic eruptions and human activity, and these are well documented in historical sources. During the last 400 years, flank eruptions have had major impacts on the urban fabric of the Etna region, especially in 1651–54, 1669, 1923 and 1928, and it is the last of these which is the focus of this paper. A detailed field and historical reconstruction of the 1928 eruption is presented which allows three themes to be discussed: the evolution of the flow field, lava volume and average magma discharge rate trend; the eruption's human impact, particularly the destruction of the town of Mascali; and the recovery of the region with reconstruction of Mascali in a new location. Detailed mapping of lava flows allowed the following dimensions to be calculated: total area, 4.38 × 10 6 m 2 ; maximum length, 9.4 km; volume , 52.91 ± 5.21 × 10 6 m 3 and an average effusion rate of 38.5 m 3 s −1. Time-averaged discharged rates are calculated allowing the reconstruction of their temporal variations during the course of the eruption evidencing a high maximum effusion rate of 374 m 3 s −1. These trends, in particular with regard to the Lower Fissure main phase of the eruption, are in accordance with the 'idealized discharge model' of Wadge (1981), proposed for ba-saltic eruptions driven by de-pressurization of magma sources, mainly through reservoir relaxation (i.e. elastic contraction of a magma body). The eruption took place when Italy was governed by Mussolini and the fascist party. The State response both, during and in the immediate aftermath of the eruption and in the years that followed during which Mascali was reconstructed, was impressive. This masked a less benign legacy, however, that can be traced for several subsequent decades of using responses to natural catastrophes to manufacture State prestige by reacting to, rather than planning for, disasters.
A new volcano-tectonic map of Etna volcano has been compiled
through a morphotectonic analysis pe... more A new volcano-tectonic map of Etna volcano has been compiled through a morphotectonic analysis performed with detailed field mapping, high-resolution DEM and orthoimages, constrained by seismotectonic data. In this study, we present a homogeneous mapping of the volcano-tectonic and tectonic elements on the whole volcano, consistent with the updated knowledge on the geology and active tectonics observed in historical times. Details of the tectonic features occurring in the lower-middle part of the volcanic edifice, namely the more densely urbanized areas, are described; volcanic elements such as eruptive fissures, caldera and flank collapse rims affecting the upper sectors, are also reported. All the volcanic landforms of Etna edifice have been generated by constructive and destructive volcanic processes largely during the last 15 ka activity of Mongibello volcano. DEM-derived images (e.g. slope and aspect maps) were produced and interpreted in order to identify faultrelated surface features based on an explicit list of well-known elements of tectonic geomorphology. Subsequently, the morphotectonic mapping has been compared with field data on geologic marker offsets, as well as evidence of surface faulting, including coseismic displacements and creeping of historical and recent events. This combined approach has enabled classifying each element reported in the map as (i) exposed faults, (ii) buried faults and (iii) hidden faults. The analysis of slip-rates confirms the exceptional dynamics of the Pernicana fault, which is characterised by an almost constant slip-rate of 20-36 mm/a over the last 1000 years, while the Timpe fault zone and the structural system in the southern flank accommodate a relevant amount of deformation with slip-rates reported to range of ca. 2-4 mm/a. Finally, a seismotectonic model summarises the information regarding seismic hazard, with reference to the additional, potentially severe effects induced by surface faulting.
Since the 1970’s, about 50 radio-isotopic ages have been determined
on Etna volcanics using diffe... more Since the 1970’s, about 50 radio-isotopic ages have been determined on Etna volcanics using different techniques: Th-U and K/Ar. Unfortunately, these ages cannot be readily used to constrain the new stratigraphic setting of the volcano, because of the uncertainty in sample locations or, sometimes, the large errors affecting the calculated ages. For this reason a program of radio-isotopic dating applying the 40Ar/39Ar incremental heating technique to date the groundmass of basaltic samples has been carried out from 2002. Forty samples (22 of which are of new publication) were collected from key outcrops on Etna volcano, selected on the basis of their stratigraphic position, while one sample was collected from the Hyblean plateau volcanics. We have obtained reliable results from all volcanics analysed from 542 ka up to 10 ka with the MSWD’s (Mean Square of Weighted Deviates) ranging from 0.03 up to 1.7 excluding IS sample (MSWD = 6.28). These new results allow us to: i) assign an age to 19 of the 25 lithostratigraphic units defined in the new geological map of Etna volcano; ii) clarify the uncertain stratigraphic position of isolated volcanic units; iii) constraint the temporal hiatus that matches the main unconformities; iv) outline the lapse of time between the end of the Hyblean volcanism and the beginning of eruptive activity in the Etna region.
This work deals with the dating of Mount Etna lava flows and
eruptive fissure deposits to the las... more This work deals with the dating of Mount Etna lava flows and eruptive fissure deposits to the last four millennia following field investigations and stratigraphic data (BRANCA et alii, 2011a). We have studied 24 of these volcanic products, including 301 large samples, through high precision archeomagnetic dating checked by 226Ra-230Th radiochronology, thus providing additional material to the previous paper by TANGUY et alii (2007). In most cases our results allow attributing ages to the historical period, although two flows are shown to be prehistoric. For the historic lavas, archeoma - gnetic ages can be defined within decades, except for three of them that erupted during a time span (Greco-Roman epoch) when the geomagnetic field underwent little variation. Although 60% of these volcanics exhibit ages comprised between 700 AD and 1850, only one (1285) is mentioned by contemporary written accounts. We conclude that i) historical documents alone are insufficient to reconstruct a coherent sequence of eruptions, and ii) a multidisciplinary approach is necessary to obtain a comprehensive eruptive history of such a very active volcano, useful for both scientific and civil protection purposes, even for such a geologically recent period as that of the last 10 or 20 centuries. Thanks to these new archeomagnetic and 226Ra-230Th data coupled with stratigraphic data, a comprehensive volcanic history of the still-outcropping Mount Etna volcanics is now available for the last 2,400 years.
The 1669 AD flank eruption was the most destructive
event on Etna volcano in historical times (∼7... more The 1669 AD flank eruption was the most destructive event on Etna volcano in historical times (∼700 BC) and provided, because of the presence of numerous quarries and subsurface data, the opportunity for a unique case study in which we directly measured the thickness of the lava field. Moreover, analysis of historical documents allowed reconstruction of the temporal evolution of the lava field and estimation of the average effusion rate. One hundred and thirty-eight thickness measurements, acquired from field surveys and subsurface data, allowed us to divide the lava field into 12 zones of homogenous mean thickness and to calculate a total lava volume of (607±105)×106m3, corresponding to an average effusion rate of 58±10 m3/s. This new volume differs by −24 % up to +64 %, from previously published values. The temporal evolution of the cumulative volume and average effusion rate were reconstructed for the first fourteen days, from field data and analysis of historical records. A short initial phase was characterized by a rapid increase in effusion rate, which reached a peak of ∼640 m3/s after 3 days. This was followed by a longer phase in which the flow rate decreased. The first 14 days were crucial for the development of the lava field, and in this time it covered 72 % of its final area and produced most of the damage. Thereafter, the growth of a complex lava tube network promoted lava field lengthening to the city of Catania, 17 km away from the vent. Effusion rate trends like those of the 1669 eruption can be adopted for future investigations aimed at assessing the effects of similar events on Etna’s most highly urbanized area and at other effusive basaltic volcanoes.
An updated geological evolution model is presented for the composite
basaltic stratovolcano of Mo... more An updated geological evolution model is presented for the composite basaltic stratovolcano of Mount Etna. It was developed on the basis of the stratigraphic setting proposed in the new geological map that was constrained by 40Ar/39Ar age determinations. Unconformitybounded stratigraphy allows highlighting four main evolutionary phases of eruptive activity in the Etna region. The Basal Tholeiitic Supersynthem corresponds to a period, from about 500 to 330 ka, of scattered fissure-type eruptions occurring initially in the foredeep basin and then in a subaerial environment. From about 220 ka, an increase in the eruptive activity built a lava-shield during the Timpe Supersynthem. The central-type activity occurred at least 110 ka ago through the Valle del Bove Supersynthem. The earliest volcanic centres recognized are Tarderia, Rocche and Trifoglietto and later Monte Cerasa, Giannicola, Salifizio and Cuvigghiuni. During the Stratovolcano Supersynthem, from about 57 ka ago, the intense eruptive activity of Ellittico volcano formed a roughly 3600 m-high stratocone that expanded laterally, filling the Alcantara and Simeto paleovalleys. Finally, effusive activity of the last 15 ka built the Mongibello volcano. Its eruptive activity is mainly concentrated in three weakness zones in which the recurrent magma intrusion generates flank eruptions down to low altitude. The four main evolutionary phases may furnish constraints to future models on the origin of Etna volcano and help unravel the geodynamic puzzle of eastern Sicily.
In this paperwe trace the impact of the 1669 eruption and the 1693 earthquakes in eastern Sicily,... more In this paperwe trace the impact of the 1669 eruption and the 1693 earthquakes in eastern Sicily, their effects on the people living in the Etna region and, more particularly, in the city of Catania and its hinterland. The former event was the largest historic eruption of Etna, having a flow field with an area of ca. 40 km2 and a maximum flow length of ca. 17 km, whereas the latter – occurring only 24 years later – killed between 11,000 and 20,000 of Catania’s estimated 20–27,000 inhabitants, plus many more in smaller settlements. Using a combination of field-based research, contemporary accounts and archival sources, the authors are able to drawa number of conclusions. First, the 1669 eruption, although it did not kill or injure, was economically the most devastating of historical eruptions. Although it affected a limited area, inundation by lava meant that landwas effectively sterilized for centuries and, in a pre-industrial agriculturally-based economy, recovery could not occur quicklywithout outside assistance from the State. Indeed some of the worst affected municipalities (i.e. Comuni) were only able to support populations that were much reduced in size. Secondly, much of the damage caused to buildings by volcanic earthquakes was effectively masked, becausemost of the settlements affectedwere quickly covered by lava flows. The vulnerability to volcanic earthquakes of traditionally constructed buildings has, however, remained a serious example of un-ameliorated risk exposure through to the present day. A third conclusion is that the 1693 earthquakes, although more serious with respect to the number of people and the area they affected in terms of mortality, morbidity and their immediate economic impact, saw a rapid and sustained recovery. Thiswas due in part to the fact that, in contrast to lava flows, an earthquake does not sterilize land, but more significant was the reduction in population numberswhich served both to release and concentrate funds for investment in recovery. By the close of the eighteenth century Cataniawas knownthroughout Europe for the quality of its townscape and buildings, many of which were constructed in the then fashionable (and expensive) baroque style. Finally, the 1669 and 1693 disasters were seized on by the authorities as opportunities to plan new and re-build old settlementswith improved infrastructure to facilitate economic growth. By the nineteenth centurymany of the lessons had been largely forgotten and there were many examples of: poor seismic design of individual buildings; and the location of newresidential and commercial areas that placed more people at greater risk fromfuture extreme events. Indeed it is only recently have new regulations been enacted to prevent the construction of buildings in the vicinity of active faults and to control development in other hazardous zones.
The new geological map of Etna volcano at 1:50,000 scale represents
a significant progress in the... more The new geological map of Etna volcano at 1:50,000 scale represents a significant progress in the geological studies of this volcano over the last 30 years, coming after Waltershausen’s map published around the mid of 19th century, the first geological map of a large active volcano, and the ROMANO et alii (1979) map published about a century later, both at 1:50,000 scale. Lithostratigraphy was used for mapping volcanic units and then Unconformity Bounded Units were applied to group lithostratigraphic units into synthems. In addition, lithosomes were exploited to better represent the spatial localization of different eruptive centres according to their morphology. On the whole, we identified 27 lithostratigraphic units, grouped into 8 synthems, and 9 volcanoes. In detail, effusive and explosive deposits generated by each eruption of Mongibello and, partially, Ellittico volcanoes were mapped as flow rank. This stratigraphic framework represents the best synthesis of the geological evolution of Etna volcano using the main unconformities recognized within its complex volcanic succession. In addition, we constrain the Etna volcanic succession and its lithostratigraphic units chronologically by radioisotope age determinations. On the basis of the outlined synthemic units, it was possible to divide Etna’s volcanic succession into 4 supersynthems, which correspond to 4 well-defined and spatially localized phases. The detailed reconstruction of the past eruptive activity allowed compiling the most accurate dataset in particular of the Holocene eruptions of Etna volcano, which will enable significantly improving the volcanic hazard assessment, together with petrological interpretation of erupted magmas and geophysical modelling of the volcano plumbing system.
Analysis of the historical records of Etna’s eruptive activity for the past three centuries shows... more Analysis of the historical records of Etna’s eruptive activity for the past three centuries shows that, after the large 1669 eruption, a period of about 60 years of low-level activity followed. Starting from 1727, explosive activity (strombolian, lava fountaining and subplinian) at the summit crater increased exponentially to the present day. Since 1763, the frequency of flank eruptions also increased and this value remained high until 1960; afterward it further increased sharply. In fact, the number of summit and flank eruptions between 1961 and 2003 was four times greater than that of the pre-1960 period. This long-term trend of escalating activity rules out a pattern of cyclic behaviour of the volcano. We propose instead that the 1670–2003 period most likely characterises a single eruptive cycle which began after the large 1669 eruption and which is still continuing. On the basis of the eruptive style, two distinct types of flank eruptions are recognised: Class A and Class B. Class A eruptions are mostly effusive with associated weak strombolian activity; Class B eruptions are characterised by effusive activity accompanied by intense, long-lasting, strombolian and lava fountaining activity that produces copious tephra fallouts, as during the 2001 and 2002–2003 eruptions. Over the past three centuries, seven Class B eruptions have taken place with vents located mainly on the south-eastern flank, indicating that this sector of the volcano is a preferential zone for the intrusion of volatile-rich magma rising from the deeper region of the Etna plumbing system.
A multidisciplinary geological and compositional investigation allowed us to reconstruct the occu... more A multidisciplinary geological and compositional investigation allowed us to reconstruct the occurrence of flank eruptions on the lower NE flank of Stromboli volcano since 15 ka. The oldest flank eruption recognised is Roisa, which occurred at ~15 ka during the Vancori period, and has transitional compositional characteristics between the Vancori and Neostromboli phases. Roisa was followed by the San Vincenzo eruption that took place at ~12 ka during the early stage of Neostromboli period. The eruptive fissure of San Vincenzo gave rise to a large scoria cone located below the village of Stromboli, and generated a lava flow, most of which lies below sea level. Most of the flank eruptions outside the barren Sciara del Fuoco occurred in a short time, between ~9 and 7 ka during the Neostromboli period, when six eruptive events produced scoria cones, spatter ramparts and lava flows. The Neostromboli products belong to a potassic series (KS), and cluster in two differently evolved groups. After an eruptive pause of ~5,000 years, the most recent flank eruption involving the NE sector of the island occurred during the Recent Stromboli period with the formation of the large, highly K calc-alkaline lava flow field, named San Bartolo. The trend of eruptive fissures since 15 ka ranges from N30°E to N55°E, and corresponds to the magma intrusions radiating from the main feeding system of the volcano.
Volcanoes hold a fascination for human beings and, before they were recorded by literate observer... more Volcanoes hold a fascination for human beings and, before they were recorded by literate observers, eruptions were portrayed in art, were recalled in legend and became incorporated into religious practices: being viewed as agents of punishment, bounty or intimidation depending upon their state of activity and the culture involved. In the Middle East the earliest record dates from the third millennium BCE and knowledge of volcanoes increased progressively over time. In the first century CE
Mount Etna in Sicily (Italy) shows N 2500 years of interactions between volcanic eruptions and hu... more Mount Etna in Sicily (Italy) shows N 2500 years of interactions between volcanic eruptions and human activity, and these are well documented in historical sources. During the last 400 years, flank eruptions have had major impacts on the urban fabric of the Etna region, especially in 1651–54, 1669, 1923 and 1928, and it is the last of these which is the focus of this paper. A detailed field and historical reconstruction of the 1928 eruption is presented which allows three themes to be discussed: the evolution of the flow field, lava volume and average magma discharge rate trend; the eruption's human impact, particularly the destruction of the town of Mascali; and the recovery of the region with reconstruction of Mascali in a new location. Detailed mapping of lava flows allowed the following dimensions to be calculated: total area, 4.38 × 10 6 m 2 ; maximum length, 9.4 km; volume , 52.91 ± 5.21 × 10 6 m 3 and an average effusion rate of 38.5 m 3 s −1. Time-averaged discharged rates are calculated allowing the reconstruction of their temporal variations during the course of the eruption evidencing a high maximum effusion rate of 374 m 3 s −1. These trends, in particular with regard to the Lower Fissure main phase of the eruption, are in accordance with the 'idealized discharge model' of Wadge (1981), proposed for ba-saltic eruptions driven by de-pressurization of magma sources, mainly through reservoir relaxation (i.e. elastic contraction of a magma body). The eruption took place when Italy was governed by Mussolini and the fascist party. The State response both, during and in the immediate aftermath of the eruption and in the years that followed during which Mascali was reconstructed, was impressive. This masked a less benign legacy, however, that can be traced for several subsequent decades of using responses to natural catastrophes to manufacture State prestige by reacting to, rather than planning for, disasters.
A new volcano-tectonic map of Etna volcano has been compiled
through a morphotectonic analysis pe... more A new volcano-tectonic map of Etna volcano has been compiled through a morphotectonic analysis performed with detailed field mapping, high-resolution DEM and orthoimages, constrained by seismotectonic data. In this study, we present a homogeneous mapping of the volcano-tectonic and tectonic elements on the whole volcano, consistent with the updated knowledge on the geology and active tectonics observed in historical times. Details of the tectonic features occurring in the lower-middle part of the volcanic edifice, namely the more densely urbanized areas, are described; volcanic elements such as eruptive fissures, caldera and flank collapse rims affecting the upper sectors, are also reported. All the volcanic landforms of Etna edifice have been generated by constructive and destructive volcanic processes largely during the last 15 ka activity of Mongibello volcano. DEM-derived images (e.g. slope and aspect maps) were produced and interpreted in order to identify faultrelated surface features based on an explicit list of well-known elements of tectonic geomorphology. Subsequently, the morphotectonic mapping has been compared with field data on geologic marker offsets, as well as evidence of surface faulting, including coseismic displacements and creeping of historical and recent events. This combined approach has enabled classifying each element reported in the map as (i) exposed faults, (ii) buried faults and (iii) hidden faults. The analysis of slip-rates confirms the exceptional dynamics of the Pernicana fault, which is characterised by an almost constant slip-rate of 20-36 mm/a over the last 1000 years, while the Timpe fault zone and the structural system in the southern flank accommodate a relevant amount of deformation with slip-rates reported to range of ca. 2-4 mm/a. Finally, a seismotectonic model summarises the information regarding seismic hazard, with reference to the additional, potentially severe effects induced by surface faulting.
Since the 1970’s, about 50 radio-isotopic ages have been determined
on Etna volcanics using diffe... more Since the 1970’s, about 50 radio-isotopic ages have been determined on Etna volcanics using different techniques: Th-U and K/Ar. Unfortunately, these ages cannot be readily used to constrain the new stratigraphic setting of the volcano, because of the uncertainty in sample locations or, sometimes, the large errors affecting the calculated ages. For this reason a program of radio-isotopic dating applying the 40Ar/39Ar incremental heating technique to date the groundmass of basaltic samples has been carried out from 2002. Forty samples (22 of which are of new publication) were collected from key outcrops on Etna volcano, selected on the basis of their stratigraphic position, while one sample was collected from the Hyblean plateau volcanics. We have obtained reliable results from all volcanics analysed from 542 ka up to 10 ka with the MSWD’s (Mean Square of Weighted Deviates) ranging from 0.03 up to 1.7 excluding IS sample (MSWD = 6.28). These new results allow us to: i) assign an age to 19 of the 25 lithostratigraphic units defined in the new geological map of Etna volcano; ii) clarify the uncertain stratigraphic position of isolated volcanic units; iii) constraint the temporal hiatus that matches the main unconformities; iv) outline the lapse of time between the end of the Hyblean volcanism and the beginning of eruptive activity in the Etna region.
This work deals with the dating of Mount Etna lava flows and
eruptive fissure deposits to the las... more This work deals with the dating of Mount Etna lava flows and eruptive fissure deposits to the last four millennia following field investigations and stratigraphic data (BRANCA et alii, 2011a). We have studied 24 of these volcanic products, including 301 large samples, through high precision archeomagnetic dating checked by 226Ra-230Th radiochronology, thus providing additional material to the previous paper by TANGUY et alii (2007). In most cases our results allow attributing ages to the historical period, although two flows are shown to be prehistoric. For the historic lavas, archeoma - gnetic ages can be defined within decades, except for three of them that erupted during a time span (Greco-Roman epoch) when the geomagnetic field underwent little variation. Although 60% of these volcanics exhibit ages comprised between 700 AD and 1850, only one (1285) is mentioned by contemporary written accounts. We conclude that i) historical documents alone are insufficient to reconstruct a coherent sequence of eruptions, and ii) a multidisciplinary approach is necessary to obtain a comprehensive eruptive history of such a very active volcano, useful for both scientific and civil protection purposes, even for such a geologically recent period as that of the last 10 or 20 centuries. Thanks to these new archeomagnetic and 226Ra-230Th data coupled with stratigraphic data, a comprehensive volcanic history of the still-outcropping Mount Etna volcanics is now available for the last 2,400 years.
The 1669 AD flank eruption was the most destructive
event on Etna volcano in historical times (∼7... more The 1669 AD flank eruption was the most destructive event on Etna volcano in historical times (∼700 BC) and provided, because of the presence of numerous quarries and subsurface data, the opportunity for a unique case study in which we directly measured the thickness of the lava field. Moreover, analysis of historical documents allowed reconstruction of the temporal evolution of the lava field and estimation of the average effusion rate. One hundred and thirty-eight thickness measurements, acquired from field surveys and subsurface data, allowed us to divide the lava field into 12 zones of homogenous mean thickness and to calculate a total lava volume of (607±105)×106m3, corresponding to an average effusion rate of 58±10 m3/s. This new volume differs by −24 % up to +64 %, from previously published values. The temporal evolution of the cumulative volume and average effusion rate were reconstructed for the first fourteen days, from field data and analysis of historical records. A short initial phase was characterized by a rapid increase in effusion rate, which reached a peak of ∼640 m3/s after 3 days. This was followed by a longer phase in which the flow rate decreased. The first 14 days were crucial for the development of the lava field, and in this time it covered 72 % of its final area and produced most of the damage. Thereafter, the growth of a complex lava tube network promoted lava field lengthening to the city of Catania, 17 km away from the vent. Effusion rate trends like those of the 1669 eruption can be adopted for future investigations aimed at assessing the effects of similar events on Etna’s most highly urbanized area and at other effusive basaltic volcanoes.
An updated geological evolution model is presented for the composite
basaltic stratovolcano of Mo... more An updated geological evolution model is presented for the composite basaltic stratovolcano of Mount Etna. It was developed on the basis of the stratigraphic setting proposed in the new geological map that was constrained by 40Ar/39Ar age determinations. Unconformitybounded stratigraphy allows highlighting four main evolutionary phases of eruptive activity in the Etna region. The Basal Tholeiitic Supersynthem corresponds to a period, from about 500 to 330 ka, of scattered fissure-type eruptions occurring initially in the foredeep basin and then in a subaerial environment. From about 220 ka, an increase in the eruptive activity built a lava-shield during the Timpe Supersynthem. The central-type activity occurred at least 110 ka ago through the Valle del Bove Supersynthem. The earliest volcanic centres recognized are Tarderia, Rocche and Trifoglietto and later Monte Cerasa, Giannicola, Salifizio and Cuvigghiuni. During the Stratovolcano Supersynthem, from about 57 ka ago, the intense eruptive activity of Ellittico volcano formed a roughly 3600 m-high stratocone that expanded laterally, filling the Alcantara and Simeto paleovalleys. Finally, effusive activity of the last 15 ka built the Mongibello volcano. Its eruptive activity is mainly concentrated in three weakness zones in which the recurrent magma intrusion generates flank eruptions down to low altitude. The four main evolutionary phases may furnish constraints to future models on the origin of Etna volcano and help unravel the geodynamic puzzle of eastern Sicily.
In this paperwe trace the impact of the 1669 eruption and the 1693 earthquakes in eastern Sicily,... more In this paperwe trace the impact of the 1669 eruption and the 1693 earthquakes in eastern Sicily, their effects on the people living in the Etna region and, more particularly, in the city of Catania and its hinterland. The former event was the largest historic eruption of Etna, having a flow field with an area of ca. 40 km2 and a maximum flow length of ca. 17 km, whereas the latter – occurring only 24 years later – killed between 11,000 and 20,000 of Catania’s estimated 20–27,000 inhabitants, plus many more in smaller settlements. Using a combination of field-based research, contemporary accounts and archival sources, the authors are able to drawa number of conclusions. First, the 1669 eruption, although it did not kill or injure, was economically the most devastating of historical eruptions. Although it affected a limited area, inundation by lava meant that landwas effectively sterilized for centuries and, in a pre-industrial agriculturally-based economy, recovery could not occur quicklywithout outside assistance from the State. Indeed some of the worst affected municipalities (i.e. Comuni) were only able to support populations that were much reduced in size. Secondly, much of the damage caused to buildings by volcanic earthquakes was effectively masked, becausemost of the settlements affectedwere quickly covered by lava flows. The vulnerability to volcanic earthquakes of traditionally constructed buildings has, however, remained a serious example of un-ameliorated risk exposure through to the present day. A third conclusion is that the 1693 earthquakes, although more serious with respect to the number of people and the area they affected in terms of mortality, morbidity and their immediate economic impact, saw a rapid and sustained recovery. Thiswas due in part to the fact that, in contrast to lava flows, an earthquake does not sterilize land, but more significant was the reduction in population numberswhich served both to release and concentrate funds for investment in recovery. By the close of the eighteenth century Cataniawas knownthroughout Europe for the quality of its townscape and buildings, many of which were constructed in the then fashionable (and expensive) baroque style. Finally, the 1669 and 1693 disasters were seized on by the authorities as opportunities to plan new and re-build old settlementswith improved infrastructure to facilitate economic growth. By the nineteenth centurymany of the lessons had been largely forgotten and there were many examples of: poor seismic design of individual buildings; and the location of newresidential and commercial areas that placed more people at greater risk fromfuture extreme events. Indeed it is only recently have new regulations been enacted to prevent the construction of buildings in the vicinity of active faults and to control development in other hazardous zones.
The new geological map of Etna volcano at 1:50,000 scale represents
a significant progress in the... more The new geological map of Etna volcano at 1:50,000 scale represents a significant progress in the geological studies of this volcano over the last 30 years, coming after Waltershausen’s map published around the mid of 19th century, the first geological map of a large active volcano, and the ROMANO et alii (1979) map published about a century later, both at 1:50,000 scale. Lithostratigraphy was used for mapping volcanic units and then Unconformity Bounded Units were applied to group lithostratigraphic units into synthems. In addition, lithosomes were exploited to better represent the spatial localization of different eruptive centres according to their morphology. On the whole, we identified 27 lithostratigraphic units, grouped into 8 synthems, and 9 volcanoes. In detail, effusive and explosive deposits generated by each eruption of Mongibello and, partially, Ellittico volcanoes were mapped as flow rank. This stratigraphic framework represents the best synthesis of the geological evolution of Etna volcano using the main unconformities recognized within its complex volcanic succession. In addition, we constrain the Etna volcanic succession and its lithostratigraphic units chronologically by radioisotope age determinations. On the basis of the outlined synthemic units, it was possible to divide Etna’s volcanic succession into 4 supersynthems, which correspond to 4 well-defined and spatially localized phases. The detailed reconstruction of the past eruptive activity allowed compiling the most accurate dataset in particular of the Holocene eruptions of Etna volcano, which will enable significantly improving the volcanic hazard assessment, together with petrological interpretation of erupted magmas and geophysical modelling of the volcano plumbing system.
Analysis of the historical records of Etna’s eruptive activity for the past three centuries shows... more Analysis of the historical records of Etna’s eruptive activity for the past three centuries shows that, after the large 1669 eruption, a period of about 60 years of low-level activity followed. Starting from 1727, explosive activity (strombolian, lava fountaining and subplinian) at the summit crater increased exponentially to the present day. Since 1763, the frequency of flank eruptions also increased and this value remained high until 1960; afterward it further increased sharply. In fact, the number of summit and flank eruptions between 1961 and 2003 was four times greater than that of the pre-1960 period. This long-term trend of escalating activity rules out a pattern of cyclic behaviour of the volcano. We propose instead that the 1670–2003 period most likely characterises a single eruptive cycle which began after the large 1669 eruption and which is still continuing. On the basis of the eruptive style, two distinct types of flank eruptions are recognised: Class A and Class B. Class A eruptions are mostly effusive with associated weak strombolian activity; Class B eruptions are characterised by effusive activity accompanied by intense, long-lasting, strombolian and lava fountaining activity that produces copious tephra fallouts, as during the 2001 and 2002–2003 eruptions. Over the past three centuries, seven Class B eruptions have taken place with vents located mainly on the south-eastern flank, indicating that this sector of the volcano is a preferential zone for the intrusion of volatile-rich magma rising from the deeper region of the Etna plumbing system.
A multidisciplinary geological and compositional investigation allowed us to reconstruct the occu... more A multidisciplinary geological and compositional investigation allowed us to reconstruct the occurrence of flank eruptions on the lower NE flank of Stromboli volcano since 15 ka. The oldest flank eruption recognised is Roisa, which occurred at ~15 ka during the Vancori period, and has transitional compositional characteristics between the Vancori and Neostromboli phases. Roisa was followed by the San Vincenzo eruption that took place at ~12 ka during the early stage of Neostromboli period. The eruptive fissure of San Vincenzo gave rise to a large scoria cone located below the village of Stromboli, and generated a lava flow, most of which lies below sea level. Most of the flank eruptions outside the barren Sciara del Fuoco occurred in a short time, between ~9 and 7 ka during the Neostromboli period, when six eruptive events produced scoria cones, spatter ramparts and lava flows. The Neostromboli products belong to a potassic series (KS), and cluster in two differently evolved groups. After an eruptive pause of ~5,000 years, the most recent flank eruption involving the NE sector of the island occurred during the Recent Stromboli period with the formation of the large, highly K calc-alkaline lava flow field, named San Bartolo. The trend of eruptive fissures since 15 ka ranges from N30°E to N55°E, and corresponds to the magma intrusions radiating from the main feeding system of the volcano.
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Papers by Stefano Branca
through a morphotectonic analysis performed with detailed field
mapping, high-resolution DEM and orthoimages, constrained by
seismotectonic data. In this study, we present a homogeneous mapping
of the volcano-tectonic and tectonic elements on the whole volcano,
consistent with the updated knowledge on the geology and
active tectonics observed in historical times. Details of the tectonic
features occurring in the lower-middle part of the volcanic edifice,
namely the more densely urbanized areas, are described; volcanic
elements such as eruptive fissures, caldera and flank collapse rims
affecting the upper sectors, are also reported. All the volcanic landforms
of Etna edifice have been generated by constructive and
destructive volcanic processes largely during the last 15 ka activity of
Mongibello volcano. DEM-derived images (e.g. slope and aspect
maps) were produced and interpreted in order to identify faultrelated
surface features based on an explicit list of well-known elements
of tectonic geomorphology. Subsequently, the morphotectonic
mapping has been compared with field data on geologic
marker offsets, as well as evidence of surface faulting, including
coseismic displacements and creeping of historical and recent
events. This combined approach has enabled classifying each element
reported in the map as (i) exposed faults, (ii) buried faults and
(iii) hidden faults. The analysis of slip-rates confirms the exceptional
dynamics of the Pernicana fault, which is characterised by an almost
constant slip-rate of 20-36 mm/a over the last 1000 years, while the
Timpe fault zone and the structural system in the southern flank
accommodate a relevant amount of deformation with slip-rates
reported to range of ca. 2-4 mm/a. Finally, a seismotectonic model summarises
the information regarding seismic hazard, with reference to
the additional, potentially severe effects induced by surface faulting.
on Etna volcanics using different techniques: Th-U and K/Ar.
Unfortunately, these ages cannot be readily used to constrain the
new stratigraphic setting of the volcano, because of the uncertainty
in sample locations or, sometimes, the large errors affecting the calculated
ages. For this reason a program of radio-isotopic dating
applying the 40Ar/39Ar incremental heating technique to date the
groundmass of basaltic samples has been carried out from 2002.
Forty samples (22 of which are of new publication) were collected
from key outcrops on Etna volcano, selected on the basis of their
stratigraphic position, while one sample was collected from the
Hyblean plateau volcanics. We have obtained reliable results from
all volcanics analysed from 542 ka up to 10 ka with the MSWD’s
(Mean Square of Weighted Deviates) ranging from 0.03 up to 1.7
excluding IS sample (MSWD = 6.28). These new results allow us to:
i) assign an age to 19 of the 25 lithostratigraphic units defined in the
new geological map of Etna volcano; ii) clarify the uncertain stratigraphic
position of isolated volcanic units; iii) constraint the temporal
hiatus that matches the main unconformities; iv) outline the
lapse of time between the end of the Hyblean volcanism and the
beginning of eruptive activity in the Etna region.
eruptive fissure deposits to the last four millennia following field
investigations and stratigraphic data (BRANCA et alii, 2011a). We
have studied 24 of these volcanic products, including 301 large samples,
through high precision archeomagnetic dating checked by
226Ra-230Th radiochronology, thus providing additional material to
the previous paper by TANGUY et alii (2007). In most cases our
results allow attributing ages to the historical period, although two
flows are shown to be prehistoric. For the historic lavas, archeoma -
gnetic ages can be defined within decades, except for three of them
that erupted during a time span (Greco-Roman epoch) when the
geomagnetic field underwent little variation. Although 60% of these
volcanics exhibit ages comprised between 700 AD and 1850, only
one (1285) is mentioned by contemporary written accounts. We conclude
that i) historical documents alone are insufficient to reconstruct
a coherent sequence of eruptions, and ii) a multidisciplinary
approach is necessary to obtain a comprehensive eruptive history of
such a very active volcano, useful for both scientific and civil protection
purposes, even for such a geologically recent period as that of
the last 10 or 20 centuries. Thanks to these new archeomagnetic and
226Ra-230Th data coupled with stratigraphic data, a comprehensive
volcanic history of the still-outcropping Mount Etna volcanics is
now available for the last 2,400 years.
event on Etna volcano in historical times (∼700
BC) and provided, because of the presence of numerous
quarries and subsurface data, the opportunity for a unique
case study in which we directly measured the thickness of
the lava field. Moreover, analysis of historical documents
allowed reconstruction of the temporal evolution of the lava
field and estimation of the average effusion rate. One hundred
and thirty-eight thickness measurements, acquired
from field surveys and subsurface data, allowed us to divide
the lava field into 12 zones of homogenous mean thickness
and to calculate a total lava volume of (607±105)×106m3,
corresponding to an average effusion rate of 58±10 m3/s.
This new volume differs by −24 % up to +64 %, from
previously published values. The temporal evolution of the
cumulative volume and average effusion rate were reconstructed
for the first fourteen days, from field data and
analysis of historical records. A short initial phase was
characterized by a rapid increase in effusion rate, which
reached a peak of ∼640 m3/s after 3 days. This was followed
by a longer phase in which the flow rate decreased. The first
14 days were crucial for the development of the lava field,
and in this time it covered 72 % of its final area and
produced most of the damage. Thereafter, the growth of a
complex lava tube network promoted lava field lengthening
to the city of Catania, 17 km away from the vent.
Effusion rate trends like those of the 1669 eruption can be
adopted for future investigations aimed at assessing the
effects of similar events on Etna’s most highly urbanized
area and at other effusive basaltic volcanoes.
basaltic stratovolcano of Mount Etna. It was developed on the
basis of the stratigraphic setting proposed in the new geological map
that was constrained by 40Ar/39Ar age determinations. Unconformitybounded
stratigraphy allows highlighting four main evolutionary
phases of eruptive activity in the Etna region. The Basal Tholeiitic
Supersynthem corresponds to a period, from about 500 to 330 ka, of
scattered fissure-type eruptions occurring initially in the foredeep
basin and then in a subaerial environment. From about 220 ka, an
increase in the eruptive activity built a lava-shield during the Timpe
Supersynthem. The central-type activity occurred at least 110 ka ago
through the Valle del Bove Supersynthem. The earliest volcanic centres
recognized are Tarderia, Rocche and Trifoglietto and later Monte
Cerasa, Giannicola, Salifizio and Cuvigghiuni. During the Stratovolcano
Supersynthem, from about 57 ka ago, the intense eruptive activity
of Ellittico volcano formed a roughly 3600 m-high stratocone that
expanded laterally, filling the Alcantara and Simeto paleovalleys.
Finally, effusive activity of the last 15 ka built the Mongibello volcano.
Its eruptive activity is mainly concentrated in three weakness
zones in which the recurrent magma intrusion generates flank eruptions
down to low altitude. The four main evolutionary phases may
furnish constraints to future models on the origin of Etna volcano
and help unravel the geodynamic puzzle of eastern Sicily.
the people living in the Etna region and, more particularly, in the city of Catania and its hinterland. The former
event was the largest historic eruption of Etna, having a flow field with an area of ca. 40 km2 and a maximum
flow length of ca. 17 km, whereas the latter – occurring only 24 years later – killed between 11,000 and 20,000
of Catania’s estimated 20–27,000 inhabitants, plus many more in smaller settlements. Using a combination of
field-based research, contemporary accounts and archival sources, the authors are able to drawa number of conclusions.
First, the 1669 eruption, although it did not kill or injure, was economically the most devastating of historical
eruptions. Although it affected a limited area, inundation by lava meant that landwas effectively sterilized
for centuries and, in a pre-industrial agriculturally-based economy, recovery could not occur quicklywithout outside
assistance from the State. Indeed some of the worst affected municipalities (i.e. Comuni) were only able to
support populations that were much reduced in size. Secondly, much of the damage caused to buildings by volcanic
earthquakes was effectively masked, becausemost of the settlements affectedwere quickly covered by lava
flows. The vulnerability to volcanic earthquakes of traditionally constructed buildings has, however, remained a
serious example of un-ameliorated risk exposure through to the present day. A third conclusion is that the 1693
earthquakes, although more serious with respect to the number of people and the area they affected in terms of
mortality, morbidity and their immediate economic impact, saw a rapid and sustained recovery. Thiswas due in
part to the fact that, in contrast to lava flows, an earthquake does not sterilize land, but more significant was the
reduction in population numberswhich served both to release and concentrate funds for investment in recovery.
By the close of the eighteenth century Cataniawas knownthroughout Europe for the quality of its townscape and
buildings, many of which were constructed in the then fashionable (and expensive) baroque style. Finally, the
1669 and 1693 disasters were seized on by the authorities as opportunities to plan new and re-build old settlementswith
improved infrastructure to facilitate economic growth. By the nineteenth centurymany of the lessons
had been largely forgotten and there were many examples of: poor seismic design of individual buildings; and
the location of newresidential and commercial areas that placed more people at greater risk fromfuture extreme
events. Indeed it is only recently have new regulations been enacted to prevent the construction of buildings in
the vicinity of active faults and to control development in other hazardous zones.
a significant progress in the geological studies of this volcano
over the last 30 years, coming after Waltershausen’s map published
around the mid of 19th century, the first geological map of a large
active volcano, and the ROMANO et alii (1979) map published about a
century later, both at 1:50,000 scale. Lithostratigraphy was used for
mapping volcanic units and then Unconformity Bounded Units were
applied to group lithostratigraphic units into synthems. In addition,
lithosomes were exploited to better represent the spatial localization
of different eruptive centres according to their morphology. On the
whole, we identified 27 lithostratigraphic units, grouped into 8 synthems,
and 9 volcanoes. In detail, effusive and explosive deposits
generated by each eruption of Mongibello and, partially, Ellittico
volcanoes were mapped as flow rank. This stratigraphic framework
represents the best synthesis of the geological evolution of Etna volcano
using the main unconformities recognized within its complex
volcanic succession. In addition, we constrain the Etna volcanic succession
and its lithostratigraphic units chronologically by radioisotope
age determinations. On the basis of the outlined synthemic
units, it was possible to divide Etna’s volcanic succession into 4
supersynthems, which correspond to 4 well-defined and spatially
localized phases. The detailed reconstruction of the past eruptive
activity allowed compiling the most accurate dataset in particular of
the Holocene eruptions of Etna volcano, which will enable significantly
improving the volcanic hazard assessment, together with
petrological interpretation of erupted magmas and geophysical modelling
of the volcano plumbing system.
through a morphotectonic analysis performed with detailed field
mapping, high-resolution DEM and orthoimages, constrained by
seismotectonic data. In this study, we present a homogeneous mapping
of the volcano-tectonic and tectonic elements on the whole volcano,
consistent with the updated knowledge on the geology and
active tectonics observed in historical times. Details of the tectonic
features occurring in the lower-middle part of the volcanic edifice,
namely the more densely urbanized areas, are described; volcanic
elements such as eruptive fissures, caldera and flank collapse rims
affecting the upper sectors, are also reported. All the volcanic landforms
of Etna edifice have been generated by constructive and
destructive volcanic processes largely during the last 15 ka activity of
Mongibello volcano. DEM-derived images (e.g. slope and aspect
maps) were produced and interpreted in order to identify faultrelated
surface features based on an explicit list of well-known elements
of tectonic geomorphology. Subsequently, the morphotectonic
mapping has been compared with field data on geologic
marker offsets, as well as evidence of surface faulting, including
coseismic displacements and creeping of historical and recent
events. This combined approach has enabled classifying each element
reported in the map as (i) exposed faults, (ii) buried faults and
(iii) hidden faults. The analysis of slip-rates confirms the exceptional
dynamics of the Pernicana fault, which is characterised by an almost
constant slip-rate of 20-36 mm/a over the last 1000 years, while the
Timpe fault zone and the structural system in the southern flank
accommodate a relevant amount of deformation with slip-rates
reported to range of ca. 2-4 mm/a. Finally, a seismotectonic model summarises
the information regarding seismic hazard, with reference to
the additional, potentially severe effects induced by surface faulting.
on Etna volcanics using different techniques: Th-U and K/Ar.
Unfortunately, these ages cannot be readily used to constrain the
new stratigraphic setting of the volcano, because of the uncertainty
in sample locations or, sometimes, the large errors affecting the calculated
ages. For this reason a program of radio-isotopic dating
applying the 40Ar/39Ar incremental heating technique to date the
groundmass of basaltic samples has been carried out from 2002.
Forty samples (22 of which are of new publication) were collected
from key outcrops on Etna volcano, selected on the basis of their
stratigraphic position, while one sample was collected from the
Hyblean plateau volcanics. We have obtained reliable results from
all volcanics analysed from 542 ka up to 10 ka with the MSWD’s
(Mean Square of Weighted Deviates) ranging from 0.03 up to 1.7
excluding IS sample (MSWD = 6.28). These new results allow us to:
i) assign an age to 19 of the 25 lithostratigraphic units defined in the
new geological map of Etna volcano; ii) clarify the uncertain stratigraphic
position of isolated volcanic units; iii) constraint the temporal
hiatus that matches the main unconformities; iv) outline the
lapse of time between the end of the Hyblean volcanism and the
beginning of eruptive activity in the Etna region.
eruptive fissure deposits to the last four millennia following field
investigations and stratigraphic data (BRANCA et alii, 2011a). We
have studied 24 of these volcanic products, including 301 large samples,
through high precision archeomagnetic dating checked by
226Ra-230Th radiochronology, thus providing additional material to
the previous paper by TANGUY et alii (2007). In most cases our
results allow attributing ages to the historical period, although two
flows are shown to be prehistoric. For the historic lavas, archeoma -
gnetic ages can be defined within decades, except for three of them
that erupted during a time span (Greco-Roman epoch) when the
geomagnetic field underwent little variation. Although 60% of these
volcanics exhibit ages comprised between 700 AD and 1850, only
one (1285) is mentioned by contemporary written accounts. We conclude
that i) historical documents alone are insufficient to reconstruct
a coherent sequence of eruptions, and ii) a multidisciplinary
approach is necessary to obtain a comprehensive eruptive history of
such a very active volcano, useful for both scientific and civil protection
purposes, even for such a geologically recent period as that of
the last 10 or 20 centuries. Thanks to these new archeomagnetic and
226Ra-230Th data coupled with stratigraphic data, a comprehensive
volcanic history of the still-outcropping Mount Etna volcanics is
now available for the last 2,400 years.
event on Etna volcano in historical times (∼700
BC) and provided, because of the presence of numerous
quarries and subsurface data, the opportunity for a unique
case study in which we directly measured the thickness of
the lava field. Moreover, analysis of historical documents
allowed reconstruction of the temporal evolution of the lava
field and estimation of the average effusion rate. One hundred
and thirty-eight thickness measurements, acquired
from field surveys and subsurface data, allowed us to divide
the lava field into 12 zones of homogenous mean thickness
and to calculate a total lava volume of (607±105)×106m3,
corresponding to an average effusion rate of 58±10 m3/s.
This new volume differs by −24 % up to +64 %, from
previously published values. The temporal evolution of the
cumulative volume and average effusion rate were reconstructed
for the first fourteen days, from field data and
analysis of historical records. A short initial phase was
characterized by a rapid increase in effusion rate, which
reached a peak of ∼640 m3/s after 3 days. This was followed
by a longer phase in which the flow rate decreased. The first
14 days were crucial for the development of the lava field,
and in this time it covered 72 % of its final area and
produced most of the damage. Thereafter, the growth of a
complex lava tube network promoted lava field lengthening
to the city of Catania, 17 km away from the vent.
Effusion rate trends like those of the 1669 eruption can be
adopted for future investigations aimed at assessing the
effects of similar events on Etna’s most highly urbanized
area and at other effusive basaltic volcanoes.
basaltic stratovolcano of Mount Etna. It was developed on the
basis of the stratigraphic setting proposed in the new geological map
that was constrained by 40Ar/39Ar age determinations. Unconformitybounded
stratigraphy allows highlighting four main evolutionary
phases of eruptive activity in the Etna region. The Basal Tholeiitic
Supersynthem corresponds to a period, from about 500 to 330 ka, of
scattered fissure-type eruptions occurring initially in the foredeep
basin and then in a subaerial environment. From about 220 ka, an
increase in the eruptive activity built a lava-shield during the Timpe
Supersynthem. The central-type activity occurred at least 110 ka ago
through the Valle del Bove Supersynthem. The earliest volcanic centres
recognized are Tarderia, Rocche and Trifoglietto and later Monte
Cerasa, Giannicola, Salifizio and Cuvigghiuni. During the Stratovolcano
Supersynthem, from about 57 ka ago, the intense eruptive activity
of Ellittico volcano formed a roughly 3600 m-high stratocone that
expanded laterally, filling the Alcantara and Simeto paleovalleys.
Finally, effusive activity of the last 15 ka built the Mongibello volcano.
Its eruptive activity is mainly concentrated in three weakness
zones in which the recurrent magma intrusion generates flank eruptions
down to low altitude. The four main evolutionary phases may
furnish constraints to future models on the origin of Etna volcano
and help unravel the geodynamic puzzle of eastern Sicily.
the people living in the Etna region and, more particularly, in the city of Catania and its hinterland. The former
event was the largest historic eruption of Etna, having a flow field with an area of ca. 40 km2 and a maximum
flow length of ca. 17 km, whereas the latter – occurring only 24 years later – killed between 11,000 and 20,000
of Catania’s estimated 20–27,000 inhabitants, plus many more in smaller settlements. Using a combination of
field-based research, contemporary accounts and archival sources, the authors are able to drawa number of conclusions.
First, the 1669 eruption, although it did not kill or injure, was economically the most devastating of historical
eruptions. Although it affected a limited area, inundation by lava meant that landwas effectively sterilized
for centuries and, in a pre-industrial agriculturally-based economy, recovery could not occur quicklywithout outside
assistance from the State. Indeed some of the worst affected municipalities (i.e. Comuni) were only able to
support populations that were much reduced in size. Secondly, much of the damage caused to buildings by volcanic
earthquakes was effectively masked, becausemost of the settlements affectedwere quickly covered by lava
flows. The vulnerability to volcanic earthquakes of traditionally constructed buildings has, however, remained a
serious example of un-ameliorated risk exposure through to the present day. A third conclusion is that the 1693
earthquakes, although more serious with respect to the number of people and the area they affected in terms of
mortality, morbidity and their immediate economic impact, saw a rapid and sustained recovery. Thiswas due in
part to the fact that, in contrast to lava flows, an earthquake does not sterilize land, but more significant was the
reduction in population numberswhich served both to release and concentrate funds for investment in recovery.
By the close of the eighteenth century Cataniawas knownthroughout Europe for the quality of its townscape and
buildings, many of which were constructed in the then fashionable (and expensive) baroque style. Finally, the
1669 and 1693 disasters were seized on by the authorities as opportunities to plan new and re-build old settlementswith
improved infrastructure to facilitate economic growth. By the nineteenth centurymany of the lessons
had been largely forgotten and there were many examples of: poor seismic design of individual buildings; and
the location of newresidential and commercial areas that placed more people at greater risk fromfuture extreme
events. Indeed it is only recently have new regulations been enacted to prevent the construction of buildings in
the vicinity of active faults and to control development in other hazardous zones.
a significant progress in the geological studies of this volcano
over the last 30 years, coming after Waltershausen’s map published
around the mid of 19th century, the first geological map of a large
active volcano, and the ROMANO et alii (1979) map published about a
century later, both at 1:50,000 scale. Lithostratigraphy was used for
mapping volcanic units and then Unconformity Bounded Units were
applied to group lithostratigraphic units into synthems. In addition,
lithosomes were exploited to better represent the spatial localization
of different eruptive centres according to their morphology. On the
whole, we identified 27 lithostratigraphic units, grouped into 8 synthems,
and 9 volcanoes. In detail, effusive and explosive deposits
generated by each eruption of Mongibello and, partially, Ellittico
volcanoes were mapped as flow rank. This stratigraphic framework
represents the best synthesis of the geological evolution of Etna volcano
using the main unconformities recognized within its complex
volcanic succession. In addition, we constrain the Etna volcanic succession
and its lithostratigraphic units chronologically by radioisotope
age determinations. On the basis of the outlined synthemic
units, it was possible to divide Etna’s volcanic succession into 4
supersynthems, which correspond to 4 well-defined and spatially
localized phases. The detailed reconstruction of the past eruptive
activity allowed compiling the most accurate dataset in particular of
the Holocene eruptions of Etna volcano, which will enable significantly
improving the volcanic hazard assessment, together with
petrological interpretation of erupted magmas and geophysical modelling
of the volcano plumbing system.