Bull Volcanol (2005) 67:732–742DOI 10.1007/s00445-005-0412-z

R E S E A R C H A R T I C L E

Stefano Branca · Paola Del Carlo

Types of eruptions of Etna volcano AD 1670–2003:implications for short-term eruptive behaviour

Received: 18 December 2003 / Accepted: 1 December 2004 / Published online: 13 April 2005� Springer-Verlag 2005

Abstract Analysis of the historical records of Etna’seruptive activity for the past three centuries shows that,after the large 1669 eruption, a period of about 60 years oflow-level activity followed. Starting from 1727, explosiveactivity (strombolian, lava fountaining and subplinian) atthe summit crater increased exponentially to the presentday. Since 1763, the frequency of flank eruptions alsoincreased and this value remained high until 1960; af-terward it further increased sharply. In fact, the number ofsummit and flank eruptions between 1961 and 2003 wasfour times greater than that of the pre-1960 period. Thislong-term trend of escalating activity rules out a pattern ofcyclic behaviour of the volcano. We propose instead thatthe 1670–2003 period most likely characterises a singleeruptive cycle which began after the large 1669 eruptionand which is still continuing.On the basis of the eruptive style, two distinct types offlank eruptions are recognised: Class A and Class B.Class A eruptions are mostly effusive with associatedweak strombolian activity; Class B eruptions are charac-terised by effusive activity accompanied by intense, long-lasting, strombolian and lava fountaining activity thatproduces copious tephra fallouts, as during the 2001 and2002–2003 eruptions. Over the past three centuries, sevenClass B eruptions have taken place with vents locatedmainly on the south-eastern flank, indicating that thissector of the volcano is a preferential zone for the intru-sion of volatile-rich magma rising from the deeper regionof the Etna plumbing system.

Keywords Etna · Historical record · Summit activity ·Flank eruptions · Eruptive behaviour

Electronic Supplementary Material Supplementarymaterial is available for this article at http://dx.doi.org/10.1007/s00445-005-0412-z

Introduction

Eruptions of Etna consist of quasi-continuous activity atsummit craters (Fig. 1) and quite frequent events alongfissures on its flanks. Strombolian activity and periodiclava fountaining episodes, often associated with lavaflows, frequently occur at summit craters (Guest 1982;Coltelli et al. 1998, 2000; Calvari et al. 2002; Alparone etal. 2003). In contrast, flank eruptions take place at inter-vals of years, producing lava effusion commonly associ-ated with weak explosive activity. From 1989, Etna hasproduced more than 150 lava fountaining episodes,ranging from strongly strombolian to subplinian, causingtephra fallout over eastern Sicily. During 2001 and 2002–2003, a period of strong explosive activity, originatingfrom vents opened on its upper flanks (Fig. 2a and b), hasdominated the activity of Etna (INGV Research Staff2001; Andronico et al. 2004). During these eruptions,particularly during the 2002–2003 activity, lava foun-taining activity formed a 4–6 km-high a.s.l. eruptiveplume that fed continuous tephra fallout. Copious lapilliand ash covered the volcano slopes, and the fine tephrafell on central Italy, western Greece, and the coast ofLibya (Andronico et al. 2004). This “unusual” flank ac-tivity has seriously impacted both economy and health,especially for the disruption at the Catania and ReggioCalabria airports (Fig. 1). Such explosive activity of Etna,previously considered subordinate with respect to thelava-flow eruptions, has drawn increasing attention fromthe scientific and political communities.

To investigate whether the behaviour of Etna in therecent past has included similar explosive activity to thatoccurring during the last 20 years, we analysed the recordof eruptions since the mid-17th century. About threemillennia of Etna activity are documented in historicalsources. Such documentation gives volcanologists a un-

Editorial responsibility: M. Carroll

S. Branca ()) · P. D. CarloIstituto Nazionale di Geofisica e Vulcanologia-Sezione di Catania,Piazza Roma 2, 95123 Catania, Italye-mail: branca@ct.ingv.itTel.: +39-95-7165800Fax: +39-95-435801

ique and long record for an active volcano, though onlyafter the mid-17th century is this record of flank eruptionscomplete and accurate (Branca and Del Carlo 2004). Inparticular, these authors emphasise that after the large anddestructive 1669 eruption (Fig. 3), observations and de-scriptions of the eruptive events involved a more modernapproach that greatly improved the quality and com-pleteness of information. Furthermore, since the 1669activity, reports became ever more detailed and docu-mented the quasi-persistent activity at the summit cratersas well as the flank eruptions. Finally, the increasingscientific quality of the chronicles allow us to obtaindetailed volcanological information and estimate themagnitude of the major explosive events.

Different cyclic behaviour was previously defined onthe basis of repeated distinct repose periods, followed bycentral activity and ending with a series of flank eruptionsfrom the mid-18th century (Imb� 1928; Behncke and Neri2003). The lack of detailed studies of the central activity,basically concerning the prolonged phases of intracraterstrombolian activity, led the aforementioned authors todefine different eruptive cycles in the various papers,stemming from subjective identification of the reposeperiods.

In this paper, we have integrated the dataset of histor-ical eruptions presented in Branca and Del Carlo (2004)with the record of strombolian intracrater activity, therebycompiling the most complete dataset available to date forthe period 1670 to the present. Moreover, we have ex-amined the features of the explosive activity that occurredat the summit craters and at vents of the flank eruptions.Our analysis of the presented data allows us to distinguishthe types of central and flank eruptions and to better definethe repose periods. Moreover, it allows us to account forthe occurrence of flank eruptions characterised by long-lasting explosive activity, such as the 2001 and 2002–2003eruptions. Finally, we investigate the relationship betweenthe central and flank activity, in an attempt to identifyapparent systematic trends in eruptive activity and to de-fine the short-term behaviour of the volcano.

Data from the historical record

Methodology of compilation

We have compiled a catalogue that summarises the date,duration, vent location, eruption type and description ofthe activity for all known Etna’s eruptions since 1670 (seeElectronic Supplementary Material). We have also in-cluded the references to the accounts that scientists wrotefollowing the eruptions. In compiling the catalogue, wehave used data from the period 1670–2003 that are con-sistent and comparable with each other. Our compilationalso includes observation of the persistent central activity,ranging from non-explosive degassing to the weak in-tracrateric strombolian explosions. This kind of analysis,however, cannot be extended before the 1669 eruptionbecause of the progressive decrease in quality and accu-racy of the sources (Branca and Del Carlo 2004). In ad-dition, concerning the intracrateric activity in the period1670–1750, we cannot exclude some gaps in the reports.Starting from the second half of 18th century the abbotRecupero provided more continuous information aboutsummit activity and from the 19th century on, the reportshave no more gaps in the eruptive record (Branca and DelCarlo 2004). Figure 4 summarised eruptive activity from1670 to the present.

We have read all accounts of post-1670 activity writtenby eyewitnesses, giving a synthetic description of theeruptive events. We have classified the more explosiveeruptions, from strong strombolian to subplinian, com-paring the deposit parameters (fallout dispersal, thickness

Fig. 1 Location map of eastern Sicily showing the location of MtEtna. SC: Summit craters; VdB: Valle del Bove. Insert a): Etnasummit craters. Bocca Nuova (BN); Voragine (VOR); North EastCrater (NEC); South East Crater (SEC)

733

of the deposit, maximum size of the clasts) with those ofwell-studied eruptions since 1986.

In the case of lava fountaining episodes (e.g., 1989,2000, and 2001 from South East Crater), the fallout dis-persion is limited within a distance of 15–20 km from thevent, and the tephra cover is not continuous (involvingonly a few grams per square metre). In the case of sub-plinian eruptions, the fallout dispersal extends to dis-tances of 100 km or more, and the deposit of tephra iscontinuous within several kilometres from the vents in theorder of 500–1,000 g per square metre (e.g., 4/5 January1990 and 22 July 1998, see references in Table 1). On thebasis of the 18th and 19th century chronicles, we candistinguish only the most intense subplinian eruptions.Concerning the smaller events, whose magnitude fallsbetween violent strombolian and subplinian such as the 23December 1995 episode from North East Crater (Coltelli

et al. 1998), their classification was possible only becausethe study of the deposit was done within a few hoursfollowing the event, before the tephra could be removedby erosion and reworking. Therefore, we could not dis-criminate the very small subplinian events from the highlava fountaining episodes by simply reading the chroni-cles. Finally, owing to detailed chronicles of some erup-tions, which report the diameter of the clasts in the distalarea of dispersal, the thickness or the weight per squaremetre of the deposit, and the related damage to the vil-lages and surrounding areas, we were able sometimes toestimate the column height, the fallout dispersion and themagnitude of the eruption.

For the central eruptions, we have distinguished effu-sive from explosive activity (see Fig. 4), which has beenfurther subdivided according to strombolian activity,single lava fountaining episodes, periods of repeated lavafountaining, and subplinian eruptions. For flank eruptions,we have classified them on the basis of the eruptive styleas follows: (i) Class A: almost purely effusive; (ii) ClassB: effusive activity associated with long-lasting, ashplume-forming, explosive activity.

– Class A eruptions are characterised by lava effusionlasting from a few days to several years, during whichsimple or compound lava-flow fields form; weakstrombolian activity is often limited to the initial phaseof the eruption and produces hornitos, spatter rampartsor small scoria cones.

– Class B eruptions are characterised by vigorous ex-plosive activity at the vents lasting for most of theeruption. Explosive activity varies between strombo-lian and lava fountaining, producing eruptive plumes

Fig. 2 a Ash plume directed southward from the new scoria conethat formed at 2,550 m elevation during the 2001 eruption. Theeruptive column is about 1.5 km high (photo by S. Branca). bAerial view from the west showing the eruptive plume directed

south-eastward originating from the eruptive vent at 2,750 m ele-vation during the 2002–2003 eruption. The summit craters can beseen to the left of the picture from the west (photo by UFVG ofINGV-Sezione di Catania)

Fig. 3 Artist’s depiction of the voluminous 1669 eruption showingthe lava flow from Monti Rossi entering the city of Catania andreaching the sea (Anonymous, ca. 1687, in Boschi and Guidoboni2001)

Fig. 4 Synoptic diagram of Mt. Etna eruptive activity from 1670 to2003, according to the different types of central and flank activity.Arrow and question mark indicate the uncertain onset and/or end ofthe eruption

734

735

and ash fall within tens to hundreds of kilometres fromthe vent. Proximal deposits form large scoria cones ora series of coalescent cones. Effusive activity is gen-erally intense as well, forming wide compound lava-flow fields.

Analysis of Etna’s historical eruptive activity

In the interval between 1670 and 1726, central activitywas infrequent, consisting only of lava emission in 1688and some months of intense lava fountaining activity in1694 at the summit. At that time, the summit consisted ofa single crater named the Central Crater (CC). Most ofthis period is characterised by prolonged phases of qui-escence, the longest of which was between 1703 and

Table 1 Summary of the subplinian eruptions during the period from 1670 to 2003. Summit craters: Central Crater (CC); Bocca Nuova(BN); Voragine (VOR); North East Crater (NEC); South East Crater (SEC). Location of towns and villages shown in Fig. 1

Year Date Vent Description References

1787 18 July CC Abundant lapilli and ash fallout on the south-eastern flank. Ash fellon Malta Island. Damage to the forests down to 1,000 m elevation

Gioeni 1787 Mirone Pasquali1787 Recupero, 1815

1800 4 March CC Lapilli and ash fall on the northern flank to the Tyrrhenian coast(Milazzo area). 238–344 g scoria injured people in the area of RoccellaVal Demone (20 km from the vent) and Moio Alcantara

Ferrara 1818;Alessi 1829–1835

1863 7 July CC Lapilli and ash fall on the southeastern flank and over southeasternSicily. A few centimetre ash layer covered the beach of Catania(Playa beach). Ash fall is reported on Malta Island and on theCalabrian coast. The “Casa Inglese” shelter at 2,957 m was destroyedby metre-sized bombs. Bombs up to 13 cm in size at about 2.5 kmaway from the vent. Damage to the cultivated areas of the SE flank

Gemmellaro 1863;Silvestri 1867

1940 16 March CC Ash fall on the eastern flank between Taormina and Catania. Thedispersal axis was northeast; about 2 kg/m2 of lapilli and ash inPiedimonte area and about 1 kg/m2 of ash in Taormina. Coarse ashfall occurred in Messina and Reggio Calabria too

Boll. Istituto VulcanologicoEtneo 1936–46

1947 5/6 Feb NEC Lapilli and ash fall on the eastern flank to the coast. A continuouslapilli deposit with bombs up to 8 cm covered the Giarre area

Cucuzza Silvestri 1949

1960 17 July CC This episode formed a several km-high eruptive column. Lapilli andash fell northeastward reaching Taormina and Messina and causingdamage to agricultural land. Some forest fires were ignited byincandescent pyroclastics up to 7 km from the summit, at 1,700–1,800 m of elevation. The most affected sector was in theLinguaglossa-Fiumefreddo area, where lapilli up to 5 cm were depositedin a continuous sheet. The proximal thickness of the deposit wasabout 10 m

Cucuzza Silvestri 1960a, b

1979 3 Aug SEC The proximal deposit was formed by metre-sized bombs up to 300 maway from the vent and bombs with a maximum diameter of 0.5 mwere emplaced at 500 m of distance. This episode produced ash fallin Catania and Siracusa causing the closure of the Catania airport

Romano and Sturiale 1981,Chester et al. 1985

1986 24 Sept NEC Formation of an eruptive column 10–13 km-high and ash fallout on theSE flank as far as 80 km away, reaching Siracusa and causing the closureof the Catania airport. At the climax, lava jets reached 1,000–1,500 mabove the vent, and the summit area was showered with large bombs upto 2 m. 750 g/m2 of lapilli and ash deposited in Nicolosi and 8–10 g/m2

deposited in Siracusa

Caltabiano et al. 1987;Amore et al. 1987

1990 4/5 Jan SEC Lapilli and ash fallout on the NW flank reaching the Tyrrhenian coastfrom S. Stefano di Camastra to Barcellona Pozzo di Gotto. The deposit

was 1.5 m thick in the proximal area and about 15 cm at 4.5 km away

Calvari et al. 1991;Carveni et al. 1994

1995 23 Dec NEC Abundant lapilli and ash fall on the east flank to the coast (Giarre).The deposit was 7 cm thick at 6 km away with bombs up to 30 cm insize and 1–2 cm thick at 20 km along the coast. Many civil defenceproblems i.e. the halting of air and road traffic and damage to vegetation

Bonaccorso et al. 1997;Coltelli et al. 1998

1998 22 July VOR This episode formed a 9 km-high eruptive column. Lapilli and ash fellsouth-southeast to Catania and Siracusa. The deposit was 4 cm thickat 4 km away. 1.5 kg/m2 of lapilli and ash deposited in Zafferana and120 g/m2 deposited in Catania. Two rheomorphic lava flows formedflowing inside BN and another one 1 km westward

IIV Trimester report(July–Sept. 1998);Andronico et al. 1999

1999 4 Sept VOR Formation of several km-high eruptive columns with lapilli and ash fallon the east flank to the coast (Giarre). During the climax, two shortrheomorphic lava flows formed, respectively 0.6 km long eastward and0.4 km long westward. A 0.5 km-long debris flow directed southwardformed from the upper slope of the summit cone. Finally, the explosiveactivity involved the BN too, and then an intense strombolian activityat SEC occurred, producing a short lava overflow south-eastward

IIV Annual report 1999

736

1726. Concerning the flank eruptions, we recognise threeClass A eruptions; these eruptions were not preceded byany central explosive activity.

From 1727 to 1879, central activity is generally char-acterised by phases of strombolian activity and lavaemissions at CC, lasting from a few months to three years,and separated by long periods of rest, the longest of whichwas 13 years (1767–1780). In several cases, lava flowsoccurred contemporaneously with the strombolian activ-ity, forming lava-flow fields in the summit areas. Duringphases of strombolian activity, intense lava fountain epi-sodes took place occasionally, producing tephra fallout onthe volcano flanks. Almost continuous lava fountainingperiods, each lasting about one month, occurred in July1787, July 1798, and June 1799. Concerning the highermagnitude events, three subplinian eruptions occurred on18 July 1787, 4 March 1800 and 7 July 1863 (see Ta-ble 1). These paroxysmal events apparently occurredwithin phases of strombolian activity. Only in some casesis explosive activity at CC followed by flank eruptions(e.g., 1792–1793 eruption). We recognise 14 Class Aflank eruptions during this period and 3 Class B (1763 LaMontagnola, 1811 Mt Simone and 1852–1853 Mt Cen-tenari; Fig. 5).

From 1880 until 1960, strombolian activity at CC be-came more frequent and lasted longer than previously,generally separated by a few year intervals of inactivity,the longest of which lasted seven years (1899–1906).Some important structural and morphologic changes oc-curred at the summit in the 20th century. In particular, the

North East Crater (NEC) formed in 1911 as a pit on thenorth-eastern flank of the summit cone. Some short-livedlava effusions and associated strombolian activity (max-imum 5 months long) occurred in 1918, 1923, 1955, 1956,and 1957. Lava fountain episodes show a similar behav-iour as in the previous period; some occur randomly,others before or at the onset of flank eruptions and gen-erally associated with periods of intense eruptive activityat the summit craters. Three subplinian eruptions occurredon 16 March 1940 at CC, 5/6 February 1947 at NEC, and17 July 1960 at CC (Table 1). One of these eruptions (17July 1960) is an isolated impulsive event not associatedwith central activity. We distinguish twelve Class A flankeruptions and two Class B (1886 Mt Gemmellaro and1892 Mts Silvestri; Fig. 5).

From 1961 to 2003, we observe a rise in the frequencyin the entire spectrum of central activity, from weak in-tracrater strombolian to the subplinian episodes, as well asflank eruptions. During this period, the longest reposeinterval was between April 1993 and July 1995. Signifi-cant morphological changes took place in the summit areain this time interval. In June 1968, a pit crater, namedBocca Nuova (BN), formed on the west side of the CC.From this date on, the previous main vent (CC) began tobe known as Voragine (VOR). Finally, in 1971 a new pitcrater opened to the southeast of BN. Starting from 1978this new crater, named South East Crater (SEC), becameactive (Fig. 1).

Concerning the highest-magnitude central events, sixsubplinian eruptions took place: on 3 August 1979 atSEC, 24 September 1986 at NEC, 4/5 January 1990 atSEC, 23 December 1995 at NEC, 22 July 1998 at VORand 4 September 1999 at VOR. Finally, in 2000 during 7months 65 episodes of lava fountaining occurred at SEC.As regards the flank eruptions, we recognised eighteenClass A and two Class B eruptions (2001 and 2002–2003;Fig. 5).

Discussion

The record of Etna’s eruptive activity highlights that thefrequency of volcanic events after the 1669 eruption wasrelatively low for about 60 years. During the period 1670–1727, only three small Class A eruptions and two briefsummit events are recorded. From the end of 1727, weobserve increased eruptive activity at CC and from 1763an increased number of flank eruptions as well (Fig. 6).Starting from 1880 the frequency of explosive activity(strombolian, lava fountaining and subplinian) increasedat CC. Finally, from 1961 significant increase in explo-sive activity at summit craters is also accompanied by asharp increase in the number of the flank eruptions(Fig. 6).

This increase in activity is consistent with the trend ofvolumetric output of lava estimated for individual flankeruptions since the 17th century (Wadge et al. 1975;Hughes et al. 1990). These authors demonstrate that the1669 eruption marks the end of a period characterised by

Fig. 5 DEM of the Etna region (from Favalli et al. 1999), showingthe vent locations of the Class B flank type eruptions since 1670.SC: Summit craters; VdB: Valle del Bove

737

large volume eruptions with a mean effusive rate of1.19 m3/s. After the 1669 eruption, a low lava outputpersisted until the mid-18th century with a mean effusiverate of 0.02 m3/s, followed by a moderately high increasecharacterised by a mean effusive rate of 0.2 m3/s until1971. Finally, the output rate then increased further afterthe 1971 eruption showing a mean effusive rate of0.51 m3/s (Wadge and Guest 1981; Branca and Del Carlo2004).

From a detailed analysis of the types of central activitywe have distinguished periods with significantly differentcharacteristics.

1. Periods of strombolian/lava fountain activity, lastingfrom days to years, which apparently reflect degassingprocesses involving magma in the upper part of theplumbing system, but not followed by any flankeruption. Occasionally, lava effusions took place dur-ing the climax of the explosive activity.

2. Periods of strombolian/lava fountain activity lastingfrom months to years, followed by flank eruptions.

3. The absence of central activity before some flankeruptions.

4. Impulsive subplinian eruptions lasting from a fewminutes to hours, generally coincident with periods ofintense strombolian activity; nonetheless on some oc-casions (e.g., 17 July 1960) they occur during reposeperiods. For the studied period, at least 12 subplinianeruptions took place. These paroxysmal events pro-duced several km-high eruptive columns that causedtephra fallout at distances of hundreds of kilometres.

From our analysis of the types of flank eruptions thatoccurred during the period from 1670 to 2003, we notedthat 54 eruptive events occurred, 87% of which areclassified as Class A and only 13% as Class B. The du-ration of the flank eruptions ranged from a few hours(13 h in 1942) to more than a year (473 days in 1991–1993). The eruptive fissures of Class A eruptions arenearly equally distributed on the North, South and Eastflanks, whereas only four eruptions have affected the

West flank (Fig. 7). The majority of Class A eruptionsvents are located in specific areas corresponding to im-portant eruptive regions, well described in the literature asareas of vent clustering (Chester et al. 1985 and refer-ences therein). These regions are the NE, ENE and S Riftzones, which radiate from the summit (McGuire andPullen 1989). Another region containing a high-density ofvents is the W Rift zone, which has been less activeduring the past three centuries, producing only foureruptions. The vents are mainly distributed between 1,600and 2,800 m elevation, with a peak between 1,600 and1,700 m (Fig. 8). Only three eruptive events were pro-duced by vents that opened below 1,600 m elevationdown to 1,100 and 1,300 m elevation (1809, 1928: theeruption that destroyed Mascali village, and 1981).

The eruptive fissures of Class B eruptions are re-stricted to the south and eastern flanks (Fig. 7). This kindof flank eruption, characterised by ash-plume-formingexplosive activity, as during the 2001 and 2002–2003events, is infrequent. In fact, in the 18th century, only oneoccurred in 1763 on the upper South flank (Fig. 5). Thiseruption was characterised by intense, continuous explo-sive activity for the entire period and minor lava effusion(Table 2). The lava fountain activity produced volcanic

Fig. 6 Histogram of the frequency of the eruptions from 1670 to2003 and relative cumulative curve (modified after Branca and DelCarlo 2004)

Fig. 7 Frequency distribution of the vent locations of the flankeruptions from 1670 to 2003

Fig. 8 Vent elevation distribution of the Class A eruptions from1670 to 2003

738

Table 2 Summary of the Class B type eruptions during the period from 1670 to 2003. Location of towns and villages shown in Fig. 1

Year Period(durationin days)

Ventlocation(m a.s.l.)

Description of the activity References

1763 18 June–10 Sept. (84)

S Flank:2,500

Along the NNE-SSW fissure intense and continuous lava fountainactivity between 19th June and 8th August formed a few km higheruptive plume, producing abundant lapilli and ash fall mainlysoutheastward. About 4 kg/m2 of ash fell on Catania between 1stand 6th July. A sharp decrease in the explosive activity took placebetween 8th and 11th August. From this date until 30th August lavafountain resumed producing ash fall. Finally, the explosive activityquickly decreased until the end of the eruption. Proximal depositformed La Montagnola scoria cone at 2,500 m elevation. A 3.5 km-long lava flow south and southeastward was produced. There wassevere damage to the cultivated areas affected by the tephra fallout

Recupero 1815;Ferrara 1818

1811 27 Oct.–24 April 1812(182)

E flank:3,000–2,000

On 27th October 1811, ash plume formed from CC. Along the E-Weruptive fissure several vents produced a wide lava flow field about5 km-long in VdB that reached an elevation of 1,100 m. Intensestrombolian activity along the fissure formed Mt Simone scoriacone and produced discontinuous ash fall on the eastern flank forthe entire period of the eruption. In particular, on 31st October 1811ash fell as far as Messina, and in Catania and Augusta on 1stNovember 1811. About 530 g/m2 of ash fell in Nicolosi on 2ndDecember

Gemmellaro 1811

1852 20 Aug.–27 May 1853(280)

E flank:1,950–1,700

Along an E-W eruptive fissure intense and continuous explosiveactivity between 20th August and 28th November formed aneruptive plume that produced ash fall mainly on the eastern flankand southwestward to Catania and Siracusa and northeastward toTaormina and Messina. The continuous ash fall caused damageto the cultivated areas on the eastern flank and some roof collapsein Zafferana, Milo, and other villages. The intensity of explosiveactivity decreased from 28th November and strombolian activityformed the Mts Centenari scoria cones. Lava effusion formed awide lava flow field 8 km-long eastward and southeastward inVdB threatening Milo, Ballo and Zafferana and reaching an elevationof 635 m

Tornabene 1852;Vigo 1853;Gemmellaro1854a, b

1886 19 May–7 June (20)

S flank:1,500–1,300

On 18th May, intense explosive activity at CC formed an ash plumeproducing ash fall on the western flanks. Intense strombolian activityalong NNE-SSW eruptive fissure formed the large Mt Gemmellaroscoria cone. The formation of eruptive plume until the end of Mayproduced almost continuous ash fall mainly on the southeastern flankto Catania, where 2.6 kg/m2 fell between 28th and 29th May, causingdamage to the cultivated areas of Pedara and Nicolosi. Ash falloccurred also in northern and southern Sicily and as far as Malta.Lava effusion formed a wide lava flow field, 6.5 km long, headingsouth and reaching an elevation of 780 m

Silvestri 1886a, b;Gentile Cus� 1886;Silvestri 1893

1892 9 July–29 Dec. (173)

S flank:2,025–1,800

On 8th July, intense explosive activity at CC formed an ash plumeproducing ash fall on the south and southeast flanks down to Catania.Along the eruptive fissure a 300–400 m-high lava fountain formedan eruptive plume that produced almost continuous lapilli and ashfall until 30th July mainly on the southeastern flank and up to Malta.The ash fall occurred also on northeastern flank reaching Messinaand Reggio Calabria. There was no explosive activity between31st July and 2nd August. It resumed on 3rd August with a lowerintensity and until 27th August formed a dilute ash plume. Severalcoalescent scoria cones formed during this eruption namedMts Silvestri. In this period, the explosive activity progressivelybecame strombolian and gradually decreasing with time. Lavaeffusion formed a wide, 7 km-long lava flow field directedsouthward, reaching an elevation of 920 m

Bartoli 1892;Arcidiacono 1902;Ricc� andArcidiacono 1904

2001 17 July–9 Aug (23)

S flank lowervent: 2,550;2,190–2,060

Lava fountaining activity formed a 2 km-high eruptive plumefrom the 2,550 m vent producing continuous ash emission between20th and 24th July and between 31st July and 5th August. Duringthese periods lapilli and ash fell eastward from Taormina to Cataniacausing the closure of Catania airport for several days. 900 g/m2

of ash fell in Acicastello in four days. Intense strombolian activityformed a large scoria cone at the 2,550 m vent between 25th and30th July. From this vent a main lava flow, heading southward,destroyed the cable car and the ski-lift. Two minor lava flows eastwardin VdB. Weak strombolian activity at the 2,190–2,060 m eruptivefissure formed a small scoria cone. From this fissure effusive activitygenerated a lava flow field that reached 1,035 m of elevation

INGV Annualreport 2001;INGV Researchstaff Sezionedi Catania 2001

739

plume a few km-high, resulting in fallout of abundantlapilli and ash, mainly over the south-eastern flank downto Catania. On this occasion, the weight of tephra per unitarea was measured for the first time. The abbot Recupero(1815) measured at Catania (24 km from the vent) 4 kgper square metre of ash which had fallen over seven days(Table 2). During the 19th century, four eruptions tookplace (1811, 1852–1853, 1886, 1892) along the south-eastern flank (Fig. 5). In general, these eruptions werecharacterised by vigorous explosive activity and lavaemission forming extensive lava-flow fields (Table 2). Inparticular, during the 1811 eruption about 530 g persquare metre fell in one day on Nicolosi, 15 km from thevent (Fig. 1). No measurements exist for the tephra de-posit of the 1852–1853 eruption, but as a consequence ofash deposition, some roofs collapsed at about 7 km farfrom the vent. During the 1886 eruption, 2.6 kg per squaremetre of ash fell 20 km from the vent in Catania in justone day, and in 1892 approximately two months of con-tinuous ash fallout affected the entire south-eastern flank,but we have no data about the weight/area of the deposit.In the 20th century no Class B eruption occurred. Afterabout a century, copious tephra fallout has affected east-ern Sicily. In fact, during the 2001 eruption, 900 g persquare metre fell in four days in Acicastello at 23 kmfrom the vent (Fig. 1), and finally in the 2002–2003eruption, 2.1 kg per square metre of ash were deposited inthree days at Catania.

The two recognised types of flank eruptions reflectdifferent eruptive mechanisms. The Class A eruptions arebelieved to represent the outpouring of magma that haslost volatiles throughout a multi-stage decompressionduring ascent within the plumbing system before reachingthe surface, as evidenced by their petrographic and geo-chemical features (Armienti et al. 1988; Corsaro andPompilio 2004). In contrast, the high explosivity of Class

B eruptions implies a much higher volatile content in themagma rising, with minimal pre-eruptive degassing, fromthe deeper part of the plumbing system. In some cases, themagma intrusion and ascent can bypass the central con-duits, producing eruptions in which an undegassed mag-ma is erupted, directly draining the deep portion of thefeeding system, as occurred in 1763, 2001 and 2002–2003(Armienti et al. 1988; INGV Research Staff 2001; An-dronico et al. 2004 and references therein).

Conclusive remarks

Our analysis of the eruptive activity at Etna since 1670indicates that its behaviour during the past three centurieshas been complex; it exhibits significant variations interms of eruption frequency and magma output rate.

1. From 1727, about 60 years after the end of the 1669eruption, the number of volcanic events began to in-crease at Etna; this increase is not linear but expo-nential. In addition, the increase in explosive activityat the summit craters precedes that in the occurrence offlank eruptions by a few years.

2. This long-term trend of increasing eruptive activityrules out a cyclic behaviour of the volcano as previ-ously supposed. Conversely, the increasing trend aftera long period (1670–1726) of very low activity mayindicate that the volcano may be still within a singleeruptive period begun after the 1669 eruption. Thisvoluminous eruption apparently ended the previouseruptive period, thus “resetting” the plumbing systemof the volcano, as inferred by Wadge et al. (1975) andHughes et al. (1990). However, this hypothesis must betested by more detailed knowledge of the longer-termbehaviour of Etna, by fully integrating the historical

Table 2 (continued)

Year Period(durationin days)

Ventlocation(m a.s.l.)

Description of the activity References

2002 27 Oct.–8 Jan. 2003(93)

S flank:2,850–2,600

Intense and almost continuous lava fountain activity between27th October and 10th December formed eruptive plume 4–6 kmhigh a.s.l. During this period, ash fall occurred in all directionsand mainly on the eastern flank of Etna. 2.1 kg/m2 of ash fell inCatania between 27 and 30th October. Ash fell over eastern Sicilyand reached Calabria and Campania regions, the western coastof Greece and the coast of Libya. A decrease in the intensity ofash emission occurred from the second half of December onwards.In this period, an alternation of lava fountains and strombolianactivity took place. Proximal deposit formed two coalescent scoriacones along the N-S eruptive fissure at 2,750 and 2,800 m ofelevation that covered Torre del Filosofo shelter. The persistentash fall caused extensive loss to the economy of eastern Sicilybecause of the prolonged closure of Catania and Reggio Calabriaairports, and damage to the cultivated areas. Discontinuouseffusive activity formed a 4.2 km-long lava flow field south andsouthwestward. Lava flow cut the S.P. 92 road and destroyeda facility and a restaurant in the Rifugio Sapienza area wherea phreatic burst injured some people on 16th December

Andronico et al.2004

740

data with geological data for at least the past 3–4 ka ofits eruptive history.

3. There appears to be no systematic relationship betweencentral activity and flank eruptions, because flankeruptions may or may not be preceded by periods ofstrombolian/lava fountain activity at summit craters.

4. Long-lasting explosive activity at vents of flankeruptions can produce widely dispersed and continu-ous tephra fallout; conversely at summit craters pro-longed explosive activity is generally weaker andproduces tephra fallout over limited areas.

5. Class A eruptions represent the most frequent type offlank eruptions at Etna during the time interval con-sidered. The vents are located mainly above 1,600 melevation along Etna’s rift zones, among which the S-Rift is the most active.

6. During Class B eruptions, intense long-lasting explo-sive activity produced eruptive plumes and copioustephra fallouts. The occurrence of this type of eruptionis restricted mostly to the 19th century. Therefore, themost recent eruptive behaviour of Etna (i.e., during the2001 and 2002–2003 eruptions) is uncommon; at thesame time, however, the eruptive style since the startof the 21st century does not appear to be anomalouswhen considered within the range of activity over thepast three centuries.

7. The vents of Class B eruptions are mainly located alongthe south-eastern flank and, in particular, five of themare aligned N-S (Fig. 5), emphasising that this is apreferred zone for the intrusion of volatile-rich magmafrom the deeper, little degassed part of the plumbingsystem. In terms of hazard assessment, the occurrenceof this type of highly explosive flank eruption must beconsidered along with the already known hazard sce-nario for this sector of the volcano, which is the mostdensely inhabited in the Etnean region.

Acknowledgements Special thanks are due to M. Coltelli whogreatly supported us during this work with discussion and criticalrevision of the paper. The authors are grateful to S. Calvari for thecritical revision of an earlier version of the manuscript, and to E.Guidoboni for advice concerning the historical sources of thestudied period. Review by M.R. Carroll, R.I. Tilling and an anon-ymous reviewer greatly improved the manuscript. We also thank S.Maugeri of the Library of the Dipartimento di Scienze Geologiche-Sezione Mineralogia e Vulcanologia, Universit� di Catania. Re-search was supported by INGV-GNV of Italy.

References

Alessi G (1829–1835) Storia delle eruzioni dell’Etna. Atti AccGioenia Sci Nat, Catania, ser. 1, vol. 3 (17–75), 4 (23–74), 5(43–72), 6 (85–116), 7 (21–65), 8 (99–148), 9 (127–206)

Alparone S, Andronico D, Lodato L, Sgroi T (2003) Relationshipbetween tremor and volcanic activity during the SoutheastCrater eruption on Mount Etna in early 2000. J Geophys Res108(B5):2241 DOI 10.1029/2002JB001866

Amore C, Giuffrida E, Scribano V, Lowenstern JB, Muller W(1987) Emplacement and textural analysis of some present-daypyroclastic deposits of Mt. Etna (Sicily). Boll Soc Geol It106:785–791

Andronico D, Del Carlo P, Coltelli M (1999) The 22 July 1998 firefountain episode at Voragine Crater (Mt Etna, Italy). Volcanicand Magmatic Studies Group, Annual Meeting, 5–6 January1999, Birmingham

Andronico D, Branca S, Calvari S, Burton MR, Caltabiano T,Corsaro RA, Del Carlo P, Garf� G, Lodato L, Miraglia L, Mur�F, Neri M, Pecora E, Pompilio M, Salerno G, Spampinato L(2004) A multi-disciplinary study of the 2002–03 Etna erup-tion: insights for a complex plumbing system. Bull Volcanolpublished online SSN:0258-8900(Paper) 1432-0819(Online)DOI: 10.1007/s00445-004-0372-8

Arcidiacono S (1902) Eruzione dell’Etna del 1892. Parte prima:L’Etna dal 1883 al 1892. Boll Acc Gioenia Sci Nat, Catania72:6–7

Armienti P, Innocenti F, Petrini R, Pompilio M, Villari L (1988)Sub-aphyric alkali basalt from Mt.Etna: inferences on the depthand composition of the source magma. Rend Soc It MineralPetrol 43:877–891

Bartoli A (1892) Sull’eruzione dell’Etna scoppiata il 9 Luglio 1892.Bol Soc Meteor It 2, 12, 11:169–179

Behncke B, Neri M (2003) Cycles and trends in the recent eruptivebehaviour of Mount Etna (Italy). Can J Earth Sci 40:1405–1411

Bollettino Istituto Vulcanologico Etneo, Universit� di Catania(1936–1946) Vol. I-VIII, In: Boll Acc Gioenia Sci Nat, Cataniaser II, Fasc 2–21

Bonaccorso A, Caltabiano T, Coltelli M, Del Carlo P, Pompilio M,Privitera E, Romano R, Spampinato S (1997) Volcanic activityof Etna volcano in 1995. Bull Volcanol Erupt 35

Boschi E, Guidoboni E (2001) Catania terremoti e lave dal mondoantico alla fine del Novecento. INGV-SGA, Compositori edi-tore, p 414

Branca S, Del Carlo P (2004) Eruptions of Mt Etna during the past3,200 Years: a revised compilation integrating the historicaland stratigraphic records. In: Bonaccorso A, Calvari S, ColtelliM, Del Negro C, Falsaperla S (eds) Mount Etna volcano lab-oratory. AGU (Geophysical monograph series), vol 143, pp 1–27

Caltabiano T, Calvari S, Romano R (1987) Rapporto sull’attivit�eruttiva dell’Etna nel periodo gennaio 1986-febbraio 1987. BollGNV 215–231

Calvari S, Coltelli M, Pompilio M, Scribano S (1991) The eruptiveactivity between October and December 1990. Acta Vulcanol1:257–260

Calvari S, Neri M, Pinkerton H (2002) Effusion rate estimationsduring the 1999 summit eruption on Mt. Etna, and growth oftwo distinct lava flow fields. J Volcanol Geotherm Res119:107–123

Carveni P, Romano R, Caltabiano T, Grasso MF, Gresta S (1994)The exceptional esplosive activity of 5 January 1990 at SE-Crater of Mt Etna volcano (Sicily). Boll Soc Geol It 113:613–631

Chester DK, Duncan AM, Guest JE, Kilburn CJR (1985) MountEtna: the anatomy of a volcano. Chapman and Hall, London, p404

Coltelli M, Pompilio M, Del Carlo P, Calvari S, Pannucci S,Scribano V (1998) Mt Etna – 1993–95 Eruptive activity. ActaVulcanol 10/1:141–148

Coltelli M, Del Carlo P, Pompilio M (2000) Etna: Eruptive activityin 1996. Acta Vulcanol 12/1:63–67

Corsaro RA, Pompilio M (2004) Magma Dynamics at Mount Etna.In: Bonaccorso A, Calvari S, Coltelli M, Del Negro C, Fal-saperla S (eds) Mount Etna Volcano Laboratory. AGU (Geo-physical monograph series) Vol 143, pp 91–110

Cucuzza Silvestri S (1949) Sui vari tipi di esplosioni vulcanicheosservati sull’Etna nell’anno 1947. Boll Acc Gioenia Sci Nat,Catania ser IV 2:1–9

Cucuzza Silvestri S (1960a) Attivit� esplosiva dell’Etna nel 1960(luglio-agosto). L’Universo 40:957–964

Cucuzza Silvestri S (1960b) Vitalit� attuale dell’Etna. Le vied’Italia, Touring Club Italia 66(12):1–10

Favalli M, Innocenti F, Pareschi MT, Pasquar� G, Mazzarini F,Branca S, Cavarra L, Tibaldi A (1999) The DEM of Mt Etna:

741

geomorphological and structural implications. Geodin Acta12(5):279–290

Ferrara F (1818) Descrizione dell’Etna, con la storia delle eruzionie il catalogo dei prodotti. Lorenzo Dato, Palermo, vol. in 8�, p256

Gemmellaro M (1811) Giornale dell’eruzione dell’Etna avvenuta il27 Ottobre 1811. Unpublished manuscript

Gemmellaro C (1854a) Sunto del giornale della eruzione dell’Etnadel 1852. Atti Acc Gioenia Sci Nat, Catania, II 9:115–141

Gemmellaro C (1854b) Breve ragguaglio della eruzione dell’Etnadel 21 Agosto 1852. Atti Acc Gioenia Sci Nat, Catania, II, p 9

Gemmellaro C (1863) Breve relazione della piccola eruzione del-l’Etna avvenuta in Luglio 1863. Tipografia C Galatol�, Catania,p 12

Gentile Cus� B (1886) Sull’eruzione dell’Etna di Maggio-Giugno1886. In Martinez F II (ed.) Catania, p 21

Gioeni G (1787) Relazione della eruzione dell’Etna nel mese diluglio 1787. Catania, Stamp. Acc degli Etnei, F. Pastore, p 39

Guest JE (1982) Styles of eruptions and flow morphology on Mt.Etna (volcanological data). Mem Soc Geol It 23:49–73

Hughes JW, Guest JE, Duncan AM (1990) Changing styles of ef-fusive eruption on Mount Etna since AD 1600. In: Ryan MP(ed.) Magma transport and storage. John Wiley and Sons, NewYork, pp 385–406

Imb� G (1928) Sistemi eruttivi etnei. Bulletin Vulcanologique,Series I 5:89–119

INGV, Istituto Nazionale di Geofisica e Vulcanologia-CataniaSection (2001) Annual report, State of the volcano

INGV Research Staff Sezione di Catania (2001) Multidisciplinaryapproach yields insight into Mt Etna 2001 eruption. EOSTransactions, Am Geoph Union 82:653–656

IIV, Istituto Internazionale di Vulcanologia CNR (1998) Trimesterreport (July–Sept.)

IIV, Istituto Internazionale di Vulcanologia CNR (1999) Annualreport, State of the volcano

McGuire WJ, Pullen AD (1989) Location and orientation of erup-tive fissures and feeder-dykes at Mount Etna: influence ofgravitational and regional tectonic stress regimes. J VolcanolGeotherm Res 38:352–344

Mirone Pasquali G (1787) Descrizione de fenomeni osservati nel-l’eruzione dell’Etna accaduta in quest’anno 1787... Stamp. Accdegli Etnei, F. Pastore, Catania, p 15

Recupero G (1815) Storia naturale e generale dell’Etna. Ed. Dafni,Tringali Editore, Catania, 1970

Ricc� A, Arcidiacono S (1904) L’eruzione dell’Etna nel 1892. AttiAcc Gioenia Sci Nat, Catania, 4, 15, 16, 17

Romano R, Sturiale C (1981) Annual report of the world volcaniceruption in 1979. Bull Volc Erupt 19:10–12

Silvestri O (1886a) La recente eruzione dell’Etna. Nuova An-tolologia 3(4):22–36

Silvestri O (1886b) Sulle eruzioni Centrale ed Eccentrica dell’Etnascoppiate il 18 e 19 Maggio 1886. I� e 2� Rapporto al RegioGoverno, Niccol� Giannotta Editore, Catania, p 32

Silvestri O (1867) I fenomeni vulcanici presentati dall’Etna nel1863, 1864, 1865, 1866 considerati in rapporto alla grandeeruzione del 1865. Atti Acc Gioenia Sci Nat, Catania 3(1):53–319

Silvestri O (1893) L’eruzione dell’Etna del 1886. Atti Acc GioeniaSci Nat, Catania, 4, VI, p 36

Tornabene F (1852) Sull’eruzione presente dell’Etna. Stab. Tipo-grafico Gaetano Nobile, Napoli, p 22

Vigo L (1853) La eruzione Etnea del 1852. Atti Acc Sci Lett,Palermo, vol II, p 28

Wadge G, Guest JE (1981) Steady-state magma discarge at Etna1971–1981. Nature 255:385–387

Wadge G, Walker GPL, Guest JE (1975) The output of Etna vol-cano. Nature 294:548–550

742