Chronology of Vesuvius activity from AD 79 to 1631 based on archeomagnetism of lavas and ...

22 Pages·2004·1.58 MB·English

BullVolcanol (2004) 66:703–724
DOI 10.1007/s00445-004-0348-8
ORIGINAL PAPER
Claudia Principe · Jean Claude Tanguy ·
Simone Arrighi · Anna Paiotti · Maxime Le Goff ·
Ugo Zoppi
Chronology of Vesuvius(cid:1) activity from A.D. 79 to 1631 based
on archeomagnetism of lavas and historical sources
Received: 1September 2002/Accepted: 29January 2004/Publishedonline:25May2004
(cid:1)Springer-Verlag 2004
Abstract The activity of Vesuvius between A.D. 79 and the densely inhabited town of Torre Annunziata. Among
1631 has been investigated by means of precise ar- the various investigated lavas, a number of which were
chaeomagnetic dating of primary volcanic deposits and previously attributed to the 1631 eruption, none is actu-
taking into account the stratigraphy of lavas and tephra, ally younger than the 12th century. Therefore it is
historical written accounts, archaeological evidence re- definitivelyconcludedthatthedestructive1631eventwas
lated to the developing urbanisation, and radiocarbon exclusively explosive.
ages. We found that the historical records are highly
usefulinconstrainingthetimingofthemainevents,even Keywords: Archaeomagnetism · Historical records ·
if the data are often too scarce and imprecise for ascer- Vesuvius · A.D. 79–1631 · Lavas
tainingthedetailsofallphasesofactivity,especiallytheir
magnitude and emplacement of all the deposit types. In
addition,someeruptionsthattookplaceinthe9thand10th Introduction
centuries appear to be unnoticed by historians. The ar-
chaeomagnetic study involved 26 sites of different lavas Vesuvius’ activity from A.D. 79 to 1631 involved both
and 2 pyroclastic deposits. It shows that within the 15 lateRomanactivity,whichoccurredfromA.D.79to472,
centuries which elapsed between A.D. 79 and 1631, the and medieval activity (Rolandi et al., 1998), which took
effusive activity of Vesuvius clustered in the relatively place from A.D. 472 to 1631. This terminology is based
short period of time between A.D.787 and 1139 and was ontheroughtemporalcoincidencebetweenthefallofthe
followed by a 5-century-long repose period. During this Roman Empire and the beginning of Middle Age (A.D.
time Vesuvius prepared itself for the violent explosive 476), which lasted until 1492. During this period, two
eruptionof1631.Thehugelavasshapingthemorphology small-scale plinian eruptions occurred, in A.D. 472 and
of the coast occurred largely through parasitic vents lo- 1631, respectively (Rosi & Santacroce, 1983; Rosi et al.,
cated outside the Mount Somma caldera. One of these 1993). In fact, there is little information regarding the
parasitic vents is located at low elevation, very close to volcanic activity of the Vesuvius between the plinian
eruption of A.D. 79 and the nearly continuous activity
that occurred after the small-scale 1631 plinian eruption
Editorialhandling: J.McPhie (Arn(cid:2)etal.,1987).Thiscontinuousactivitywasmadeup
C. Principe())· S.Arrighi of lava effusions (Fig. 1), together with strombolian, vi-
Istitutodi Geoscienze eGeorisorse (IGG), olentstrombolian,andsubplinianepisodes(Arrighietal.,
CNR, ViaG.Moruzzi 1,56124Pisa, Italy 2001). Little data exist in the literature on the time of
e-mail: [email protected] deposition and distribution of the lavas discharged
Tel.:[phone]
during the 15-century-long period from A.D. 79 to 1631.
Fax:[phone]
Moreover, determination of the stratigraphic position of
J.C. Tanguy·M.L. Goff the so-called “medieval” lavas within the overall stratig-
Universityof Paris 6 andInstitut dePhysique duGlobede Paris, raphy of the Vesuvius has been hindered by urban de-
94107St.Maurdes Fosses Cedex,France velopment along the Vesuvius’ coast. In spite of this
unclear stratigraphic position, many authors, even in re-
A.Paiotti
cent literature, attributed many of these large lavas that
Via PietroNenni 25,55042Forte deiMarmi,Italy
shape the coast morphology to the 1631 eruption (Di
U.Zoppi Girolamo, 1970; Burri & Di Girolamo, 1975; Rolandi &
ANSTO– environment, Russo,1989;Rolandietal.,1993;Lireretal.,2001).This
PrivateMail Bag1,2233Menai, NSW,Australia
704
Fig.1 Samplingmap (topogra-
phyfrom IGM-DTMdata,
courtesy ofG.Vilardo, INGV-
VesuvianObservatory,Naples).
Roman numerals:sampling
sectors asdiscussed inthetext.
Whitedots: samplingsites (see
Table 3 forthenumberof
samplesateach site).The dis-
tribution oflavas erupted be-
tween1631and1944(simplified
fromtheCNR,1986,geological
map),and thepyroclastic flow
deposits ofthe1631eruption
(fromRosietal.1993)arealso
shown
ideaoflarge1631lavasoriginatesfromarelativelyrecent 1996). However, the written sources available on the
reconstructionofthe1631eruption(LeHon,1865,1866), Vesuvius’ activity between A.D. 79 and 1631 provide
that has been uncritically adopted by almost all later au- usefulrecordsofthemaineventsandatleastsomedetails
thors. According to Rosi et al. (1993), the 1631 eruption on the types of volcanic activity.
did not produce any lava flow. All the post-1631 accounts, dealing with Vesuvius’
Thismatterhasimportantimplicationsfordetermining history or its “latest” eruption, contain more or less
the degree of volcanic risk in the Vesuvius area, because completelistsofthevolcano’spasteruptions,aswellasa
the 1631 eruption has been taken as representative of the numberofreferencestoprintedsourcesthatdealwiththe
maximum expected hazards posed by the volcano in the VesuviusasfarbackasGreekandRomantimes.Perhaps
mid-to-long term (Barberi et al., 1995). In order to assess the most complete and reliable of these lists is presented
thepotentialhazardoftheVesuvius,itisalsonecessaryto in the milestone work “Bibliography of Vesuvius” by
ascertain whether eruptions were uniformly distributed in Furchheim (1897). An accurate critical collection of the
time or clustered in climaxes with very high eruption written sources on Vesuvius’ activity from A.D. 79 to
rates, alternating with periods of much less intense ac- 1631 was given by Alfano (1924). Other authors have
tivity (Heiken, 1999). Such information exists for the subsequently dealt with the chronology of the Vesuvius’
relatively short period from 1631 to 1944 (e.g. Carta et eruptions between A.D. 79 and 1631 (Preusse, 1931;
al., 1981 and Arrighi et al., 2001), but is lacking for the Figliuolo & Marturano, 1998; Nazzaro, 1998, Gasparini
muchlongertimeintervalfromA.D.79to1631.Theaim &Musella,1991)withoutsubstantialchangestoAlfano’s
of this paper is to fill the gap mainly through critical conclusions. Recently, Stothers & Rampino (1983) con-
reading of historical records and archaeomagnetic dating sidered not only written and associated archaeological
of the “medieval lavas”. sources on Vesuvius’, but also on all the volcanic erup-
tions that occurred throughout the Mediterranean area
before A.D. 630. The investigated printed sources are
Historical and geochronological data rather different from those usually quoted by people
working on Vesuvius and include not only Latin and
Historical sources Greek texts, but Byzantine, Syrian, and Armenian sour-
ces, as well.
Itis commonlybelieved thatthe information provided by It is important to note that all these studies have been
thehistoricalsourcesontheVesuvius’activityfromA.D. performed based on the more common printed sources.
79 to 1631 is scarce and fragmentary. Such a belief arose Detailed work on manuscript and ecclesiastic documents
in comparison with the large amount of documentation found in archives and libraries is still required in order to
published after the 1631 eruption (Cerbai & Principe,
705
Table1 The activity of Vesuvius between A.D. 79 and 1631 as bolian activity, with possible emission of intracaldera lava flows.
inferredbyhistoricalsources.Citationsrefertotheprintedsources. SeePrincipe(2003)foradetaileddiscussionandtheoriginaltexts
“Activity” refers reported weak, more or less continuous strom-
Eruptions Activity DescribedPhenomena
172 Violentstrombolianactivity1
AD203 Explosiveeruption,withaplinianfalloutphase2
222–235 Moreorlesscontinuousstrombolianactivity3
379–395 Atleastfumarolicactivity4.Aphaseoflavaeffusionpossiblyhappened5
AD472 5–6November:largeexplosiveeruption,withaplinianfalloutphase,dispersedtoNE(ashesasfaras
Costantinopoli),darkeningandheavyrains.Hugenu(cid:1)eardentesandseveredestructionaredescribedallaround
Vesuvius’6.FromthiseruptionstartsthecultofSanGennaroasprotectorofNaplesagainstVesuvius’
512 Moreorlesscontinuousstrombolianactivity7
AD536 Explosiveeruption,darkeninginMesopotamialastedallthewinterofthisyear.8
AD685 February-March:earthquakes,pliniancolumnandrelatedfallout9.Anotcompletelyreliablesourcegivesan
accountoflavasenteringthesea10
AD787 Autumn-Winter:lavafountainsandlava(orpyroclastic?)flows“sixmileslong”11
AD968 Eruptionwithlavasintothesea12
AD991 Earthquakeandexplosiveeruption(“...eruptingflamesandvomitingashes...”)13
AD999 Suddenlavafountainsandlavaemission(”...piceasatquesulphurearepenteflammaserumpere...”),fineashes14
1006or Atleastexplosiveeruption,withrumble,vigorousthrowingofblocks(3milesfromthecrater)andunbreathable
1007 gasemissions15
1037 27JanuaryorFebruary:Effusiveeruptionwithlavasintothesea(“...eructavitincendium,itautusqueadmare
discurreret...”)16
1139 From29Mayto5June:explosiveeruption,withblacklapillifalloutandreddishashes(“...pulveremferruginei
colorisetsubrubei...”),fallingduring30daysasfarasNapoli,Capua,SalernoandBenevento17
1150 Violentstrombolianactivity18
1306? Unlikelyparasiticeruptionwithlavasintothesea19
1500? Fumarolicactivityandunlikelyphreaticexplosion20
1ClaudioGaleno Pergameno,DeMedendi MethodoLibriXIII,liberV,cap.12
2Dione CassioNiceo, Historiae Romanae,liberLXXVI.
3Dione CassioNiceo, Historiae Romanae,liberLXVI.
4San Paciano, Paraenesis adpoenitentiam.
5Ammiano Marcellino, Indictione decima.
6Marcellino(Conte),Chronicon;ProcopiofromCesarea,DeBelloGotico,liberII,capIV;CarloSigonio,HistoriarumdeOccidentali
ImperioLibriXX,liberXIV&XVI;FlavioMagnoAurelioCassiodoro,OperaOmniaquaeextant,LiberIVVariarum,Epistola50.
7Marcellino (Conte),Chronicon.
8 Procopio from Cesarea, De Bello Gotico, liber II (cap IV), liber IV (cap XXXV); Giovanni from Efeso, Ecclesiastical History (other
references are listed inStothers and Rampino,1983).
9PaoloDiacono,HistoriaLongobardorum,liberVI,cap.IX;GiorgioAgricola,Deremetallica.Denaturaeorumquaeeffluuntexterra,
liberIV.
10 Appendixtotheholylegend of San Gennaro (inAlfano, 1924).
11 GregorioMonaco,manuscript ingreek, Universityof Messinalibrary.
12Damianus Petrus,Opera Omnia,OpusculumXIX.
13 PompeoSarnelli, CronologiadeiVescovi etArcivescovi Sipontini,1730, pg.112.
14DamianusPetrus,OperaOmnia,OpusculumXIX;UbaldoMonaco,ChronicumDucumNeapolis,inRaccoltadivariecroniche,diarii
ecc, appartenentialRegno diNapoli,Napoli, Perger, 1781.
15 RidolfoGlaber,Historia Francorum.
16 AnonymusCassinensis, Chronicon;AnonymusCavensis, Chronicon;RomoaldoSalernitano, Chronicon.
17 Anonymus Cassinensis, Chronicon; Anonymus Cavensis, Chronicon; Falcone Beneventano, Chronicon; Romualdo Salernitano
Chronicon.
18 ElEldrisi,L’italia descritta nellibro delRe Ruggero,quotedin Baratta,IlVesuvio e lesueeruzioni, Roma,DanteAlighieri, 1897.
19PighiusStephanusVinandus,HerculesProdiciusseuPrincipiisjuventutisvitaetperegrinatio,Antuerpiae,CristoforoPlautinus,1587,
pg466;AndreaSchottus,ItinerariumItaliae,Amstelodami,Jansson,1655,pg526(intotheItalianedition,dated1669,thenameofthe
Author becameFrancesco Scoto).
20 LeoneAmbrosio, DeNola,Venetiis, 1514, liberI,cap.I:De AgroNolano,deque montibusVesuvio etAbella.
produce a fully reliable picture of the activity of the noted by Stothers & Rampino (1983), to the proliferation
volcano during this long historical period. of vicarious “second-hand” citations.
Table 1 (Principe, 2003) provides a summary of This common practice gave rise, for instance, to var-
Vesuvius’ activity between A.D. 79 and 1631 deduced ious reports of the “great eruption of A.D. 512”, which
from critical reading of the original sources proposed by washypothesizedbyAlfano(1924)onthebasisofaletter
previousauthors.Thenumberofconfirmederuptionsand from Magno Aurelio Cassiodoro to King Teodorico of
periods of activity is much smaller than that reported in Italy and uncritically accepted in all the subsequent lit-
thepost-1631literatureontheVesuvius,asisthenumber erature.However, acarefulreadingofCassiodoro’sletter
of the truly primary sources, meaning contemporary (or reveals that it was simply a request for fiscal exemptions
nearly so) to the described events. Such a misleadingly for a population still suffering the effects of a previous
large number of sources and eruptions is due, as already devastating eruption in A.D. 472.
706
No lavas outside the Mount Somma caldera are A presumed eruption in 1306, with lava reaching the
recorded by historical sources during the first centuries sea, is referred toby Leandro Alberti (1568), and Pighius
after the A.D. 79 eruption. On the contrary, Vesuvius’ (1587) as well as by Schottus (1655), who copied from
activity only involved a series of explosive events of Pighius. This eruption was also confirmed by Masculo
variable violence until at least A.D. 685. The A.D. 472 (1633) on the basis of these sources. However, Alfano
eruption was by far the most important of these events. (1924) denied the existence of such an eruption, demon-
Plinian fallout and huge nu(cid:1)es ardentes can be clearly strating on thebasis of historical argumentsthat the1306
identified in the historical accounts of this eruption (Rosi date is a typographical error in the text of Alberti (1568)
& Santacroce, 1983). who intended to discuss the 1036 event (Principe, 2003).
An explosive eruption must have occurred around The occurrence of at least one flank eruption at the
A.D. 536. This has been indirectly documented in the Vesuvius during the period between A.D. 79 and 1631 is
writings of ProcopiofromCesarea, GiovannifromEfeso, possibly recorded by a fresco, which once adorned the
and other authors in the western Mediterranean, who re- vestibule of the Basilica of San Gennaro Extra Moenia in
ported the darkening of the sky over Constantinople for Naples. The work has been attributed to the 15th century
manymonths, accompanied byan unusuallyharsh winter school of Andrea Da Salerno. Reprinted in Alfano (1924),
in Mesopotamia (Stothers & Rampino, 1983). it depicts the Vesuvius as observed from Naples, with two
TheeruptionofA.D.685surelyhadastrongexplosive volcanic plumes, one issuing from the main crater (the
componentaswell.Analysisofthehistoricalsourcesdoes elevationofwhichislowerthanthepeakofMountSomma)
not clarify whether this eruption also involved lavas as whiletheotheremergesfromoneormoreventssituatedon
popular tradition implies the lava underlying the old the southern flank of the Gran cono. The date of the
PalazzoBaronaleofTorredelGrecooriginatesfromthis eruption towhich the fresco refers toisunknown. In other
event,anddoesnotcropoutanymoreatpresent(Principe, words,thisfrescomightsimplybeeitheragenericviewof
2003). A number of the subsequent eruptions (e.g. A.D. the erupting Vesuvius, or a copy of a previous work.
787, 968, 999, and 1037) had large effusive components. Historical accounts describe a number of parasitic
TheA.D.991eventwasapparentlyexclusivelyexplosive, cones,whichbyageandpositionmayrepresentthevents
aswellasthosein1006–7and1139forwhichnoeffusive of some lavas emitted between A.D. 79 and 1631. These
episodes are described. However, the last two eruptions include the Viulo and Fossamonaca cones, the morphol-
were documentedbyauthorslivingoutside theVesuvius’ ogy of which is still well visible today, the two cones at
area. For this reason, in the absence of great damages to Tironi and the three cones at I Monticelli (“little hills”).
inhabited areas, the emission of lavas during these erup- Sorrentino (1734) described two scoria cones and asso-
tions remains possible (Principe, 2003). ciated lavas from the site known as “i Tironi”, north of
Although the summit of the volcano is described by Torre del Greco, as well as three small scoria cones,
Dione Cassio as a rounded depression “like an am- called “I Monticelli”, aligned in a roughly east-to-west
phitheatre”,withoutmentionofanyinternalcone(Alfano, direction behind the Camaldoli hill. All these cones are
1924) during the third century A.D., historical data sug- attributed to medieval eruptions by Sorrentino (1734).
gest the gradual building of the Gran cono inside the The cones of I Monticelli have been buried by the prod-
Mount Somma caldera, starting from ~A.D. 172, due to ucts of subsequent eruptions and only a few morpholog-
intracaldera lava emissions and strombolian activity icaltracesremainatpresent,whereastheTironihillswere
(Table 1). After the 1139 eruption, the Gran cono was already almost completely quarried by Sorrentino’s time.
certainly present inside the Mount Somma caldera, with In 1514 the Venetian Leone Ambrosio described an
an altitude lower than that of Mount Somma, and a large event that took place in the year 1500. This could be a
crater“resultingfromthelasteruption”(Boccaccio,1353, modest phreatic eruption. Apart from this source, how-
inAlfano,1924).Thisisthesamegeneralmorphologyof ever, no trace remains of the 1500 event in the various
the volcano after the main explosive eruptions of the manuscripts, annals, and chronicles of the time. For this
1631–1944 period (Nazzaro, 1998; Arrighi et al., 2001). reason, its occurrence had already been disputed in the
After the 1139 eruption, the next description of the 17th century (Braccini, 1632).
Vesuviusinanactivestate,characterisedby“emissionof Summing up, on the basis of available historical data,
incandescentmaterialsfromthemaincrater”(strombolian itseemsprobablethatfromtheearly12thcenturyto1631,
activity), seems to be presented in the text of the Arab the volcano was in a state of repose, apart perhaps from
writer El Eldrisi, dated 1150 and quoted by Alfano more or less continuous fumarolic activity. Since the
(1924), who refers to Baratta (1897). The numerous Vesuvius was practically inactive for such a long time, it
sources subsequent to 1150 listed by Alfano (1924) only caught most of the inhabitants unaware at the moment of
report that a mountain near Naples had occasionally itsawakeningonDecember16th,1631(Rosietal.,1993).
eruptedinthepast,withoutprovidingfurtherobservations
on eruptive activities coeval to the time of writing. There
are, instead, some references to flames in the crater, vis- Tephra chronology
ible especially at night, and probably attributable to the
ignition of fumarole gases, rather than strombolian ac- The main stratigraphical markers of the entire post-A.D.
tivity from the main crater. 79 succession are the A.D. 472 deposits (Rosi & San-
707
Table2 Available 14C data for charcoal and paleosols (*) of the intervals, stratigraphic position, and physical characteristics, as
postA.D.79–1631period.Themostprobable(boldtype)eruption givenintheliterature,andthehistoricaldatalistedinTable1.(**)
dates were defined in this work on the basis of calibrated age Calibrated agegivenin Andronicoetal. (1995)
1 2 3 4 5 6 7
Sample Locality Ageb.p. Calibrated Literature Reference Mostprobableeruptions
age attribution
R715/L371E 1815€40 A.D.135–320 SantaMaria Andronicoetal.(1995) A.D.203
PFSV86A LAGNO 1750€60 AD472 Arn(cid:2)etal.(1987)
AMENDOLARE
R939* ARCIPRETE 1630€50 AD472 Arn(cid:2)etal.(1987)
Rome643 1605€35 A.D.415–535 AD472 Andronicoetal.(1995) A.D.472
PFSV83 LAGNOdiPOLLENA 1600€60 AD472 Arn(cid:2)etal.(1987)
TERZIGNO 1590€190 A.D.59–861 AD472 Rolandietal.(1998) A.D.472
PFSV86A LAGNO 1580€60 AD472 Arn(cid:2)etal.(1987)
AMENDOLARE
PFSV306* CASETRAPOLINO 1550€50 AD512 Arn(cid:2)etal.(1987) A.D.536
WW-595 TERZIGNO 1440€60 A.D.537–692 IIeruption Rolandietal.(1998) A.D.685
Rome644 1355€55 A.D.645–760 PM5 Andronicoetal.(1995) A.D.685
WW-6327 OTTAVIANO 1290€40 A.D.661–863 IIeruption Rolandietal.(1998) A.D.685
PFSV101 LAGNOdiPOLLENA 1280€50 AD787 Arn(cid:2)etal.(1987)
Rome653* 1265€55 A.D.685–885 PM5 Andronicoetal.(1995) A.D.685
Rome641 1230€55 A.D.690–935 PM6 Andronicoetal.(1995) A.D.787
Rome652* 1166€55 A.D.780–980 PM6 Andronicoetal.(1995) A.D.787
WW-596 TERZIGNO 1140€60 A.D.775–1017 IIIeruption Rolandietal.(1998) 787/991/999/1006–7
PFSV86B LAGNO 1050€85 AD787 Arn(cid:2)etal.(1987)
AMENDOLARE
BOSCOREALE 950€90 A.D.895–1279 IVeruption Rolandietal.(1998) 991/999/1006–7/1037/1139
WW-597 TERZIGNO 950€50 1003–1279 IVeruption Rolandietal.(1998) 1006–7/1037/1139
PFSV308* WofOTTAVIANO 470€55 1631 Arn(cid:2)etal.(1987)
PFSV315 betweenPOLLENA 330€55 1485–1650** 1631 Arn(cid:2)etal.(1987) 1631
andCERCOLA
tacroce, 1983, Mastrolorenzo et al., 2002) and the 1631 in pockets above the medieval-age lavas in an area
deposits (Rosi et al., 1993), both resulting from small- southeast of the Vesuvius, and beneath the 1631 pyro-
scale plinian events. On this basis, the tephra succession clastic flow deposits.
from A.D. 79 to 1631 can be divided into two parts. With the aim of identifying possible correlations be-
Andronico and coworkers (Andronico et al. 1995, tween historically-defined eruption ages and the different
1996a,1996b) called the pyroclastic sequence prior to the tephra age attributions proposed by various authors, Ta-
A.D. 472 eruption the “ Santa Maria cycle”, which in- ble2reportsallthe14Cagesavailableintheliteraturefor
cludes the tephra of the A.D. 203 eruption, as already the period from A.D. 79 to 1631. The last column in
recognised by Johnston-Lavis (1884) and Arn(cid:2) et al. Table 2 reports the historically substantiated eruptions or
(1987). Andronico et al. (1995, 1996a, 1996b) identified eruptive periods in the age interval obtained by calibrat-
six main explosive-component eruptions subsequent to ing the 14C ages. Of the eruptions deemed “possible”
A.D.472;theirtephradepositsareinterlayeredwithseven throughstudy of thehistorical sources,the mostprobable
minor tephra layers. The first main tephra layer was at- ones (also based on stratigraphic position and physical
tributed by Andronico et al. (1995, 1996a, 1996b) to the characteristics) are presented. A newly determined ra-
A.D.512eruption,however,thiseruptionhasbeenshown diocarbon age (see Appendix 1), based on charcoal
to be an unlikely source (see discussion above). There- fragmentsfoundunderalapillifalloutdepositoftheA.D.
fore, we propose to attribute this first main tephra layer, 79–1631 period, confirms the occurrence of an explosive
starting the post-A.D. 472 succession, to the explosive episode around A.D. 685.
eruption of A.D. 536. Comparing Tables 1 and 2, it is evident that, despite
In contrast to Andronico et al. (1995, 1996a, 1996b), the rather low precision of the 14C age determinations, a
Rolandi et al. (1998) identified only four main explosive good agreement exists between the 14C ages and the
eruptions in the post-A.D.-472 stratigraphy, and also at- historically documented eruption ages for the events with
tributed different ages to the layers. The last of these an explosive component, a fact that underscores the im-
eruptions is represented by a lapilli fallout deposit which portance of historical data.
was attributed to the 1139 eruption by Rolandi et al.
(1998). The description and stratigraphic position of this
deposit correspond to the “ochraceous” lapilli fallout
described by Principe et al. (1987), which is encountered
708
Fig.2 a-b Sector I.(a)The
Granatello headland onthe
Topographicmapof Mount
Vesuvius compiled anddrawn
insixsheets atthescale of
1:10.000bystudents ofthe
MilitaryTopography Institute
ofFlorence (1875–86).The
small promontoryof Villa
d’Elboeuf (1) isformed bythe
A.D.79pyroclasticflow and
debris flowdeposits. Abranch
ofthenu(cid:3)eardentesofthe1631
eruption(Rosi etal., 1993) ex-
tended southof this,leaving
PalazzoMascabruno (2)un-
touched, butdestroyngthean-
cientGranatello gardens(4)
and partially covering thepre-
1631lava thatgave rise tothe
main coastal morphology.Con-
structionoftheRoyalPalaceof
Portici(3)and surrounding
gardensbegan in1738. (5) The
Herculaneum excavations.(b)
Aerial viewof thecurrent
Granatello andRoyal Palace
areas; P25refers tothesam-
plingsiteoftheGranatellolava
Chronostratigraphy of lavas
Theproblemoftheabsoluteageandstratigraphicposition
oflavasfromA.D.79to1631wasraisedforthefirsttime
by Johnston-Lavis (1884,1891b) who believed that the
lavaeffusionsreportedinhistoricalsourcesfortheperiod
from A.D. 79 to 1631 were much less frequent than the
explosive events. Moreover, he maintained that the lavas
were confined inside the Mount Somma caldera sur-
rounding the Gran cono (Fig. 1), which had not yet been
filled.Thisconvinctionwasduetothefactthat,following
Fig.3 SectorI,immediatelysouthoftheGranatelloarea.(1)The
LaFavoritacountryhouseand(2)itsgardensthatreachtheseaat
ScoglidellaFavorita.(3)Afewhundredmeterssouth,ahugelava
crops out extensively on the headland of Scogli della Scala (now
Punta Quattro Venti), sampled at P18. Topographic base as in
Figure2
709
Fig.4a-b SectorII.(a)Aerial
photographof Torredel Greco
asit appears today. (b)Map of
Torre delGreco drawn byG.
Morghen afterthe1794lava
destroyedfour-fifthsofthethen
existingtown. (1) The lava
headland ofCalastro(sampling
siteP10).(2)TheMonasteryof
theMinorFranciscanOrderand
theannexedchurchofMadonna
delleGrazie. TheMonastery
wassparedfrom the1631py-
roclastic flow (Rosietal.,
1993).(3)Palazzo Brancaccio
and itsgardens. (4)The Torre
delGrecoTownHallhousedin
theone-time PalazzoBaronale.
Allthese buildings lieona
morphologicalhigh sparedby
1631nu(cid:1)eardentesandthenby
1794lava,that corresponds to
an oldlava,unfortunately not
croppingoutanymore, attribut-
ed byhistorical records to the
A.D.685eruption.(5)Thearea
affectedbythepyroclasticflow
deposits ofthe1631eruption
(“mareseccato”,which isItal-
ianfor“dried sea”) andbythe
lava ofthe1794eruption after-
wards
Le Hon (1865,1866), Johnston-Lavis attributed all the been attributed by Di Girolamo (1970) to the 1631
lavas cropping out along the coast to the 1631 eruption. eruption, always on the basis of the data of Vittozzi &
The belief that all the lavas along the coast belong to Gasparini (1965), without any stratigraphic support. At
the 1631 eruption has been recently supported by the least for Torre Bassano, historical data do not support
work of Vittozzi & Gasparini (1965), who performed such attributions, since a watchtower was built between
absolute age determinations via the radioactive 1559 and 1567 over this lava (Principe, 2003, Fig. 5).
226Ra-238U disequilibrium method on the lava of Recently, Rolandi & Russo (1989) ascribed both the lava
GranatelloandonthethreelavasoftheVillaInglese(see under Masseria Donna Chiara and the lava cropping out
Figures 2, 3, 4,5, 6,7 for the locations). On the basis of along the coast near Torre Annunziata between Cantiere
these data, Burri & Di Girolamo (1975) ascribed the la Perla and Palazzo Monteleone to the 1631 eruption.
Granatello lava to 1631, and the Villa Inglese lavas to Finally,althoughtheemissionoflavasduringthe1631
1631, 1480 and 1139. Other lavas cropping out along the eruption can be ruled out, based on volcanological evi-
coastbetweenPorticiandTorreAnnunziata(Scoglidella dence (Principe et al., 2003) and historical documents
Scala, Calastro, Ponte di Riveccio, Torre Bassano) have (Rosi et al., 1993), most of the lavas cropping out along
710
Fig.5 Sector III. The Torre Bassano headland exhibits the mor- the railway (2), and covers a stratigraphic succession (see inset)
phology and stratigraphy typical of all the sector of the coastline including the A.D. 79 eruption-related debris flow and previous
from Portici to Torre Annunziata. In this site, the tower (1) was pyroclastic deposits. The pyroclastic flow deposits of the 1631
built between 1559 and 1567 on the promontory generated by a eruption(3)extendonbothsidesofthemophologicalhighinduced
medieval lava that flowed into the sea. This lava crops out under by the lava and are now covered by numerous greenhouses and
thetower(2),alongtheroadinlandfromthetower(P15),andalong vineyards
the coast of the Vesuvius are still attributed to the 1631 refer to the so-called “big sample plaster method” of
eruption by many authors. We intend to definitively Thellier (1981) for archaeological purposes and routinely
clarify this subject with our archaeomagnetic data. applied at the Saint Maur Laboratories. Application of
this methodology for dating of young volcanic products,
its advantages, and limitations are given by Tanguy et al.
Synthesis of available chronological data (2003).
The sampling method involves the collection of sev-
Onthebasisoftheavailablechronologicalinformation,at eralbigsamples,eachweighing0.5–1kg,distributedover
least 11 main eruptions took place at Vesuvius’ between some tens of meters. Each block is first detached with a
A.D. 79 and 1631. The most important of these events is hammer and then replaced in its original position. Plaster
the small-scale plinian eruption of A.D. 472. An effusive ofappropriatefluidityispouredontheblock,tosupporta
component is described by historical documents for at plate carrying a spherical spirit level, thus making a
least four of these eleven eruptions (Table 1), with lava horizontal surface 6–7 cm in diameter on which the sun
fronts spreading outside the Mount Somma caldera rim, shadow is marked for calculation of the geographical
and reaching the sea in A.D. 787, 968, 999, and 1037. north. In the laboratory, the samples are replastered in
According to historical, radiocarbon, and stratigraphic square moulds 12 cm in size. Measurements are per-
data, significant explosive episodes took place at least in formed by means of a large rotating induction magne-
A.D.203,472,536,685,787,991,999,1006/7,and1139, tometer and an AF demagnetization device for big sam-
resulting in a sequence of lapilli fallout deposits. Within ples (Le Goff, 1975).
this sequence, a number of minor tephra deposits give The advantages of this method with respect to tradi-
evidence of additional minor explosive episodes not re- tional core-drilling are the extremely precise orientation
ported by printed chronicles and still not dated by ra- of the sample in the field and the possibility of obtaining
diocarbon or other methods. high-precision data on lavas, welded scoriae, and high-
temperature-emplaced, non-welded, pyroclastic deposits
(Hoblitt et al., 1985; Genevey et al., 2002). Another
Archaeomagnetic sampling and measurements fundamental advantage is that the plaster method avoids
the effect of any parasitic magnetization acquired during
This archaeomagnetic study of the Vesuvius is based on the drilling process (Lauer, 1978; Audunsson & Levi,
the precise method developed at Saint Maur Laboratories 1989).
from the Institut de Physique du Globe de Paris (IPGP), On the basis of their stratigraphic positions and addi-
France (Thellier, 1981; Tanguy et al., 1985, 1999, 2003). tionalfielddata(e.g.,ageoftheoldestbuildingssittingon
Sampling and measurement procedures used in this work the lavas, changes of locality names after the main
711
Fig.6 a-b Sector IV.(a) To-
pography oftheVilla Inglese-
Le Mortellearea (topographic
baseas inFig.2) showingthe
smoothmorphologyinducedby
themedievallavaflowscovered
bysubsequent tephra deposits,
contrasting withtherough
morphologyoftheof the1760
lavasurfacecroppingoutinthe
easternsectorofthisfigure.(1)
The oldlava quarryof Villa
Inglese.(2)Masseria Donna
Chiara.(3)Villa Prota.(4)Le
Mortelle.(5)Torre Scassata.
The quarryhasbeen progres-
sively enlargedand todayhas
reached thelava emittedin
1760.(b)Presentaerialviewof
theVillaInglese quarry. Num-
bersrefer tothesamplingsites
ofthe pre-1631lavas flowsex-
tensively croppingoutboth in-
sidethequarriedareaandonthe
coast beneath andinland of the
TorreScassata tower
eruptions, etc. ...) (see Appendix 2), a total of 26 sites thecoastdonotappearonthe1:25,000-scaleCNR(1986)
have been selected and sampled for archaeomagnetic geological map.
measurements, giving a total of over 400 analysed sam- All the lavas of this period are petrographically very
ples, covering nearly all the lava outcrops attributable to similar(Joronetal.,1987;Belkinetal.,1998;Raiaetal.,
theA.D.79–1631period.Fig.1showsthelocationofthe 2000; Paiotti, 2000) (Table 4). The main phenocrysts are
sites which are grouped in geographical sectors, whereas two clinopyroxenes(diopside and augite), which are both
Table 3 gives the geographical coordinates and a de- present in all lavas, and leucite. Olivine and a dark mica
scription of each site. Some sites are located in corre- (phlogopite) are the other most important phases. The
spondencetonewlybuiltroadsegmentsorworkyardsfor groundmass is composed of plagioclase (An ), leucite,
80
the construction of new buildings, which have brought to clinopyroxenes, and oxides. Modal analyses (Table 5)
light portions of the lavas covered by the 1631 nu(cid:1)es show the fact that correlations between different sites
ardentes. Some of the sampled lavas cropping out along cannot be performed on the basis of petrographical
712
Fig.7 a-c Sector V.(a)The
shoreof Torre Annunziata(to-
pographicbaseasinFig.3).(1)
Scogli diProta.(2)The old
“Fortedell’Oncino”fortress.
(3)Villa Filangeri.(4) Terme
Nunziante-Lido Azzurro.(5)
PalazzoMonteleone.Originat-
ingfrom a ventnearBosco del
Monaco (label ‘vent’inthis
sketch map),a huge lava
reached theseaforming theLa
Storta promontory,where the
pier ofTorre Annunziatais
nested.Note theancient lava
quarries(q) markingthelava
positionbetween theventand
thesea. (b)Present aerial view
ofthe TorreAnnunziata water-
front.Some depositsattributed
totheA.D.79and 472erup-
tions are exposedunder the
aforementioned lava inthe
scarp alongtheLitoraneaMar-
coniroad, from PalazzoMon-
teleone(5)to LidoAzzurro
(Cantiere LaPerla)(4).(c)
Stratigraphic sectionof theex-
cavationsforthe newTorre
AnnunziataHospital atRione
Boscomonica (P23inmapa).
Ozf 467referstoa sampleof
charcoal, dated bymeans of
radiocarbonmethod (see Ap-
pendix1).Its calibrated age is
639–687A.D
composition.Infact,samplescomingfromthesamelava, differentportionsoftheselectedlava.Theobtainedmean
asinthecaseofP01andP20samplingsites,maydifferin value of the semi-angles of the 95% confidence cone of
mineral abundance (Lc and Cpx) and vesicularity, as al- the average paleodirections (a ) resulted in 1.2, with a
95
ready found for the similar lavas of the 1631–1944 range from 0.6 to 1.8 (Table 6).
Vesuvius activity (Principe, 1979).
For each site, an average of 12 archaeomagnetic
analyses were performed on samples originating from