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Journal of Maps
ISSN: (Print) 1744-5647 (Online) Journal homepage: https://www.tandfonline.com/loi/tjom20
Volcanic evolution of the Somma-Vesuvius
Complex (Italy)
Alessandro Sbrana, Raffaello Cioni, Paola Marianelli, Roberto Sulpizio,
Daniele Andronico & Giuseppe Pasquini
To cite this article: Alessandro Sbrana, Raffaello Cioni, Paola Marianelli, Roberto Sulpizio, Daniele
Andronico & Giuseppe Pasquini (2020) Volcanic evolution of the Somma-Vesuvius Complex (Italy),
Journal of Maps, 16:2, 137-147, DOI: 10.1080/17445647.2019.1706653
To link to this article: https://doi.org/10.1080/17445647.2019.1706653
© 2020 The Author(s). Published by Informa
UK Limited, trading as Taylor & Francis
Group on behalf of Journal of Maps
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Science
Volcanic evolution of the Somma-Vesuvius Complex (Italy)
Alessandro Sbrana
a
,Raffaello Cioni
b
, Paola Marianelli
a
, Roberto Sulpizio
c,d
, Daniele Andronico
e
and Giuseppe Pasquini
a
a
Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy;
b
Dipartimento di Scienze della Terra, Università di Firenze, Firenze, Italy;
c
Dipartimento Geomineralogico, Università di Bari, Bari, Italy;
d
IGAG-CNR, section Milano, via M. Bianco 9, Milano, Italy;
e
Istituto Nazionale di
Geofisica e Vulcanologia, Osservatorio Etneo - Sezione di Catania, Catania, Italy
ABSTRACT
A volcanological map of the active Somma-Vesuvius volcano is presented at the 1:20,000 scale.
The map is based on 1:5000 field mapping carried out during the Italian CARG project.
Geological data are represented on a digital terrain model of the volcano. This allows a
better visualisation of the main morphological, volcanic, and geological features. The legend
is organised in four different panels, which depict the activity of the volcano and caldera
development. The geological survey is based on recognition and description of
lithostratigraphic units. The geological map highlights the volcanic evolution of the Somma-
Vesuvius volcano, and it is propaedeutic for further studies aimed at improving the scientific
knowledge and the volcanic hazard assessment of this world-famous volcano.
ARTICLE HISTORY
Received 13 August 2019
Accepted 16 December 2019
KEYWORDS
Geological map; digital
terrain model; Somma-
Vesuvius; Italy
1. Introduction
The Somma-Vesuvius, together with the Phlegrean
Fields Volcanic District (Rosi & Sbrana, 1987;Sbrana,
Marianelli, & Pasquini, 2018 and references therein),
are part of a series of active volcanic complexes devel-
oped within the extensional graben of the Campanian
plain, one of the most important peri-Tyrrhenian struc-
tures of the Southern Apennines chain. Its formation
occurred from Miocene to Pleistocene following the
opening of the Tyrrhenian basin (Peccerillo, 2005).
Somma-Vesuvius volcano formed at the intersection
of two main, NE-SW and NW-SE fault systems, inside
thesoutheastportionoftheCampanianplainhalfgraben.
In this side of the graben, the Mesozoic carbonate units
represent the basement of the volcano (below 1800 m
ofdepth)andhostpartofthemagmafeedingsystem.
In some cases, the presence of carbonates influences the
eruption dynamics, through the interaction between
magma and carbonate-derived CO
2,
and possibly the
magma composition by carbonate assimilation (Dallai,
Cioni, Boschi, & D’Oriano, 2011;Iacono Marziano,
Gaillard, & Pichavant, 2008;Peccerillo, 2005;Rittmann,
1933;Savelli, 1967), and distinguishes Somma-Vesuvius
from the volcanoes of the Phlegrean Fields Volcanic
District (carbonate basement deeper than 4000 m).
Despite Somma-Vesuvius is worldwide recognised
as one of the most hazardous volcanoes, few geological
maps have been published. After the pioneering geo-
logical map of sir Johnston-Lavis (1891), a geological
map of Somma-Vesuvius Volcanic Complex at
1:25,000 scale was published by Rosi, Santacroce, and
Sbrana (1986), containing a detailed survey of both
ancient and modern lava flows, the latter performed
through the analysis of historical documents combined
with field data. However, the geological map did not
describe the complex pyroclastic successions, that
were mapped through the use of a single unit. In the
framework of the CARG’88 project, financed by Servi-
zio Geologico d’Italia (ISPRA) and aimed at obtaining
a new 1:50,000 geological map of Italy, new geological
surveys and volcanological studies started in the
Somma-Vesuvius area in the 90s. They produced a
more detailed and accurate geological map of
Somma-Vesuvius and the surrounding plain at
1:15,000 scale (Regione Campania, 2003). In the same
project, other geological maps based on the Unconfor-
mity Bounded Stratigraphic Units (UBSU) were
implemented, i.e. the 1:50,000 scale Sheets Ercolano
and Sorrento (Servizio Geologico d’Italia, in press).
More recently, a geological map of a limited area in
the southwestern sector of the volcano, dominated by
the products of the most recent period of activity of
the volcano, was published by Paolillo et al. (2016).
Based on the detailed field surveys carried out
during the above mentioned CARG’88 project and
on new stratigraphic and volcanological studies, an
updated geological map of the Somma-Vesuvius vol-
cano is here presented at the scale 1:20,000 (Plate I).
Geological data were placed on a digital terrain
model (DTM) of the volcano, allowing a better visual-
isation of the morphological and volcanological fea-
tures. The legend, based on lithostratigraphic units,
© 2020 The Author(s). Published by Informa UK Limited, trading as Taylor & Francis Group on behalf of Journal of Maps
This is an Open Access article distributed under the terms of the Creative Commons Attribution-NonCommercial License (http://creativecommons.org/licenses/by-nc/4.0/), which
permits unrestricted non-commercial use, distribution, and reproduction in any medium, provided the original work is properly cited.
CONTACT Paola Marianelli paola.marianelli@unipi.it
JOURNAL OF MAPS
2020, VOL. 16, NO. 2, 137–147
https://doi.org/10.1080/17445647.2019.1706653
was also revised and grouped to better illustrate the
volcanological evolution of Somma-Vesuvius. Finally,
a large set of published and unpublished volcanological
data on dispersal of pyroclastic density currents
(PDCs) and fallout deposits of more than 20 explosive
events of variable magnitude and intensity was also
completely revised and summarised in a dedicated
plate (Plate I).
2. Eruptive history of Somma-Vesuvius
The Somma-Vesuvius volcanic complex is formed by
an older stratovolcano (Mt. Somma) cut by an
eccentric, polyphasic caldera, and by a stratocone
(Vesuvius) grown during historical times inside the cal-
dera (Figure 1). Mt. Somma stands over a large sedi-
mentary plain, prevalently formed by volcaniclastic
deposits originated by the mobilisation of the pyroclas-
tic deposits during inter- and syn-eruptive periods, and
collectively described as the volcano sedimentary apron
of Somma-Vesuvius (Regione Campania, 2003). The
volcanoclastic deposits alternate with medial to distal
PDCs and fall deposits.
The first detailed stratigraphy of the Somma-Vesu-
vius was made by Delibrias, Di Paola, Rosi, and Santa-
croce (1979), who named all the main eruption units
and first provided a general chronologic framework.
This reconstruction was the base for the monographic
work of Santacroce (1987) and was then progressively
improved and detailed (Figure 2) by several authors
(as summarised in Cioni, Bertagnini, Santacroce, &
Andronico, 2008 and Santacroce et al., 2008).
Nowadays the deposits of a large number of eruptions
of different intensity occurred in the last 22 ky of
activity are well known in terms of stratigraphy, disper-
sal and main physical parameters, and many of them
can be mapped with a certain detail. Most of the studies
dedicated to the different eruptions derive from the
detailed stratigraphic work carried out during the
field survey for the new geological map, and isopach
maps of more than 20 events have been revised and
presented in the synoptic Plate I.
The construction of the stratovolcano started after
the Campanian Ignimbrite eruption (Phlegrean Fields;
39 ky, De Vivo et al., 2001), as evidenced by the strati-
graphy of the Trecase 1 geothermal well (Brocchini,
Principe, Castradori, Laurenzi, & Gorla, 2001). The
stratovolcano grew up to around 2000 m in height
over a time span of ca. 20 ky (Cioni, Santacroce, &
Sbrana, 1999), mainly through the piling up of lava
flows and spatter and loose scoria deposits. The main
effusive to mildly explosive activity of the Somma stra-
tovolcano was interrupted around 22 ky BP by the tra-
chytic Pomici di Base Plinian eruption (Santacroce
et al., 2008). This event marked the onset of the multi-
stage Somma caldera formation (Cioni et al., 1999) and
the shift to a more explosive activity fed by generally
evolved magmas. The Pomici di Base eruption was fol-
lowed by effusive/mildly explosive activity from lateral
vents, aligned along regional faults (San Severino, Pol-
lena and Camaldoli eruptive fracture systems) (Figure
3) and, after about 3 ky, by the Pomici Verdoline
(Figure 4(A)) subplinian eruption (Cioni, Sulpizio, &
Garruccio, 2003). The following 15 ky period of activity
Figure 1. (A): View from Vesuvius cone; in the background the Somma inner caldera wall; in the foreground 1944 lava flow. (B):
Somma-Vesuvius (Google Earth image). (C): Valle del Gigante, view from Mt. Somma, Cognoli di Levante. In the foreground Somma
spatter cone (Cognoli) and lavas (LSC formation in the main map), and in the background, 1944 lava (lv20 in the main map, centre
of picture) and 1944 hot avalanche deposits (1944 va in the main map) overlying the lava flow and Colle Umberto exogenous lava
dome (left).
138 A. SBRANA ET AL.
was characterised by two, large intensity (Plinian)
eruptions, separated by long periods of nearly complete
quiescence, and by a shift from trachytic to phonolitic
compositions (Figure 5). These two Plinian events
(Mercato Pumice, 9.0 ky BP; Mele, Sulpizio, Dellino,
& La Volpe, 2011; Avellino Pumice, 3.9 ky BP; Sevink
et al., 2011;Sulpizio, Bonasia, et al., 2010a,2010b), pro-
duced phonolitic and phonolitic to tephriphonolitic
Figure 2. Simplified chronostratigraphic sequence (not to scale) of Somma-Vesuvius. Arrows refer to explosive eruptions, length
and colour (blue = VEI 2; green = VEI 3; orange = VEI 4; red = VEI 5) reflect the estimated VEI (data from Cioni et al., 2008); dashed
arrows mark eruptions of uncertain source. Yellow boxes show periods of persistent strombolian and effusive activity.
Figure 3. Geological and structural sketch map of Somma-Vesuvius. Submarine gas emission areas from Caliro, Chiodini, Avino,
Cardellini, and Frondini (2005).
JOURNAL OF MAPS 139
products, respectively (Figure 4(A,B)). Both these Pli-
nian eruptions, culminated in phases of caldera col-
lapse, are related to the partial emptying of a crustal
magma reservoir (Cioni et al., 1999), which started to
define the present-day caldera shape (see the main
map and Figure 3). No clear activity from Somma-
Vesuvius is recorded in the intervening periods separ-
ating these two eruptions, except for the sporadic
finding of badly preserved, fall deposits dubitatively
traceable to the activity of the volcano or from the
nearby Phlegrean fields caldera (Figure 2).
After the Avellino eruption, the frequency of med-
ium to high intensity eruptions increased, with at least
8 explosive events ranging from subplinian to violent
strombolian and vulcanian (Andronico & Cioni,
2002). This period of activity ends in 217 BC
(Stothers & Rampino, 1983) preceding the AD 79
Pompeii Plinian eruption. This iconic event was
described in detail by Pliny the Younger, who was
the first eyewitness of a large volcanic eruption that
handed down a written report of this natural
phenomenon. The deposits are represented by a
widely dispersed pumice fallout and by numerous
PDCs (Figure 6). Magma composition varies from
phonolitic to tephriphonolitic, mainly differing from
the preceding products for the highest K
2
O/Na
2
O
ratio. The deposits of AD 79 eruption are still easily
visible in the main archaeological sites of Ercolano,
Oplontis and Pompei (Figure 3) and in several
other minor excavations. The eruption modified the
morphology surroundings the volcano, producing a
general increase of the elevations up to 10–20 m in
Ercolano (Guidobaldi, Camardo, & Rossi, 2014) and
Pompei archeological areas (Vogel, Maerker, & Seiler,
2011), and an important variation of the coastline, as
reported in the geological map (main map; Cinque &
Irollo, 2004;Guidobaldi, Camardo, & Notomista,
2014).
Figure 4. (A) Traianello quarry. The white pumice layer in the middle of the sequence is the base of the Mercato Pumice fallout,
followed on top by pyroclastic flow unit. The thinly stratified fallout deposits of Pomici Verdoline and Campi Flegrei Agnano Pomici
Principali are visible below the Mercato Pumice. (B) The fallout sequence (white and grey beds) of the Avellino Pumice. (C) Panora-
mic view of the Post AD 472 sequence in the area of Terzigno. The sequence is formed by the superposition of scoria and ash fallout
beds of several eruptions. The light coloured deposits at the base of the sequence record the final pyroclastic density currents and
lahars related to the AD 472 Pollena eruption.
140 A. SBRANA ET AL.
The Vesuvius cone possibly began to form after
AD 79 inside the Somma caldera, in coincidence
with minor explosive activity described in few con-
temporary chronicles (Cioni, D’Oriano, Bertagnini, &
Andronico, 2013). Its growth occurred discontinuously
during periods of open conduit activity (Figure 2). All
the products erupted during the entire following period
of activity are mostly characterised by poorly evolved
compositions (from tephrites to tephriphonolites)
with only minor amount of phonolitic magmas associ-
ated to the very initial phases of the two largest and
most intense events of the period. At the same time,
the alkali content of the products was increasingly
higher with respect to the preceding activity (Figure 5).
The first period, named Santa Maria Cycle (Cioni
et al., 2013), punctuated the I-III century period, pre-
ceding the subplinian event of the AD 472 Pollena
eruption (Sulpizio, Mele, Dellino, & La Volpe, 2005).
Open conduit activity (Figure 4(C)) characterised the
V–VIII and X–XII centuries (San Pietro Cycle and
Villa Inglese lava flows), and preceded the AD 1631
subplinian eruption. The latter was the last large explo-
sive event occurred in the recent history of Vesuvius.
Basing on several lines of evidence, these two last
subplinian eruptions were taken as reference for
defining the maximum expected event in case of reac-
tivation by the national Civil Protection Department
(http://www.protezionecivile.gov.it/media-comunicazione/
dossier/dettaglio/-/asset_publisher/default/content/
aggiornamento-del-piano-nazionale-di-emergenza-per-
il-vesuvio).
In particular, the scenario of the expected event was
based on that of the AD 1631 eruption, accurately
reconstructed through detailed stratigraphic works
and the analysis of several contemporary chronicles
(Bertagnini et al., 2006;Rosi, Principe, & Vecci,
1993). The AD 1631 eruption was followed by the
last period of activity (1638–1944) during which the
‘Gran Cono’of Vesuvius attained its present mor-
phology. The eruptive activity of this period was split
into 18 cycles characterised by summit and lateral
lava effusions and semi-persistent mild explosive
activity. Each cycle was closed by more intense
effusive-explosive ‘final’eruptions (Santacroce, 1987),
the last one occurred in 1944 (Figure 7). The rise of a
volatile-rich mafic magma batch triggered a mixed
effusive-explosive eruption (Marianelli, Metrich, &
Sbrana, 1999;Marianelli, Sbrana, Métrich, & Cecchetti,
2005) opened by lava effusions and followed by a vio-
lent lava fountaining phase (Figure 7(B)) and by a
final phreatomagmatic phase (Marianelli et al., 1999,
and references therein). The Vesuvius is quiescent
since March 1944.
3. Methods
The first step for the elaboration of the volcanological
map was the collection and the graphic layout of the
base map. The orographic background of the map is
the result of the Lidar DTM (1 × 1 m ground resolution,
Z-error ± 15 cm, years 2009–2012) and the ORCA pro-
ject DTM (5 × 5 m, years 2004–2005). These two digital
elevation models were mixed to produce a realistic topo-
graphic effect, using Adobe Photoshop® CC 2018. The
topographic contour lines were derived from the
smoothing and contouring process on the ORCA
DTM, and the high-resolution Lidar DTM was also
used to draw geomorphological elements such as frac-
tures, scars, caldera and crater rims and parasitic vents
(see http://sit.cittametropolitana.na.it/lidar.html).
Figure 5. Composition of Somma-Vesuvius products is largely variable through time and within a single eruption. The diagram
shows the increasing alkalinity of the erupted products from the Somma lavas up to the most recent products (data from Santacroce
et al., 2008).
JOURNAL OF MAPS 141
Figure 6. A general consensus exists on the stratigraphy of the AD 79 eruption deposits (Cioni, Marianelli, & Sbrana, 1992;Sigurdsson,
Carey, Cornell, & Pescatore, 1985) with the definition of three different phases. The Opening phase, comprising only a few centimetres
of accretionary lapilli-bearing ash fall and very minor surge beds, was followed by the Plinian magmatic phase, mostly consisting of
tephra fallout (white and grey pumice layers, phonolitic to tephriphonolitic) dispersed in an elongated fan to SSW. This fallout deposit
is the product of a sustained Plinian column, which during the deposition of the grey pumice collapsed at least four times producing
low concentration, turbulent pyroclastic density currents (hereafter PDCs). The latter can be found interlayered in the fallout deposits
along the slopes of the volcano and in the plain approximately up to a maximum distance of 8–10 km from the vent. According to Pliny
the Younger’s letters (Sigurdsson et al., 1985;Sigurdsson, Cashdollar, & Sparks, 1982), the Plinian phase of the eruption lasted no
longer than 20 h. It was followed by a phreatomagmatic phase whose initial stages (formation of a short-lived sustained column con-
cluded with the generation of a high-energy turbulent PDC) coincided with the onset of the caldera collapse that enlarged to the
South the existing depression left by the preceding Plinian events (Cioni et al., 1999). The AD 79 eruption closed with the emplace-
ment of ‘wet’PDCs and a thick succession of accretionary lapilli-bearing ash beds. The figure contains the stratigraphy of the eruption
in the Pozzelle quarry. (A) Close view of the white pumice fallout. At the base it is visible the grey ash of the opening phase. On top of
the white pumice is a thin bed of grey pumice fallout followed by the pyroclastic flow deposits related to the total column collapse. (B)
Sequence of pyroclastic flow deposits in the San Sebastiano quarry.
142 A. SBRANA ET AL.
The bathymetric reconstruction was based on the
data elaboration extracted from the map ‘Golfo di
Napoli’, 1:60.000 scale published by Istituto Idrografico
della Marina, Genova, 1889.
The geological data are based on the CARG’88 field
survey carried out at the 1:5.000 scale and on unpub-
lished data of the authors. In this study, all data were
stored and generated in a geographical information
system (GIS) developed with ESRI ARCGIS® 10.6,
using the cartographical reference system WGS 84-
UTM 33N. Data generation in a GIS environment
enables the production of the following thematic
layouts:
.orographic background of inland and offshore areas;
.topographic and bathymetric contour lines;
.polygonal and linear base map elements such as
buildings and streets (Open Street Map);
.polygonal, linear, and punctual features for volcano-
logical, geological, and geomorphological elements;
.Archaeological sites of interest (Pompei and Erco-
lano data extracted from CTP –Carta Tecnica Pro-
vinciale, scale 1:25.000; sheets 446 IV and 448 III);
All these layers were elaborated with Adobe Illus-
trator® CC 2018 and Adobe Photoshop® CC 2018
obtaining the final layout at the scale 1:20,000.
Figure 7. (A) View of the present Vesuvius crater (inner northern), deposits of Phase 4: 1913–1944 lavas (lv19 and lv20 in the main
map); 1944 proximal fallout deposits (spatter ss and lapilli fallout in the main map); breccia and ashes (pc in the main map). (B)
Somma-Vesuvius and 1944 plume on 24 March 1944 (photo credit: U.S. Air Force Photo Coll. Courtesy of the National Air and Space
Museum, Smithsonian Institution).
JOURNAL OF MAPS 143
Data collected for Plate I, as isopachs of fallout and
PDC deposits, main outcrops, vents and caldera rims of
the different eruptions, are from a detailed revision of
published and unpublished data mainly collected by
the authors in the last 30 years. Published data are
acknowledged in the legend of Plate I.
4. Results and discussion
The geological map (main map) is based on a reinter-
pretation of the volcano evolution in terms of different
phases, during which the volcano changed the style of
activity and some main volcano-tectonic structures
progressively formed and evolved. The proposed
phases mark the main steps of the volcano evolution,
that will be described in detail in the following sub-sec-
tions: (i) Somma stratovolcano growth, (ii) polyphasic
caldera formation, (iii) post caldera activity and, (iv)
growth of Vesuvius cone. The forty-three lithostrati-
graphic units related to the different phases are here
distinguished on the basis of their lithologic and sedi-
mentological features, as well as in many cases by the
presence of basal unconformities (mainly erosional),
paleosols, reworked or variably pedogenized beds
and, in a few cases, structural unconformities. We pre-
ferred not to use a stratigraphic scheme based on
UBSU (Unconformably Bounded Stratigraphic
Units), as for example proposed at other Italian volca-
noes (Branca, Coltelli, Groppelli, & Lentini, 2011;Funi-
ciello & Giordano, 2010) or similar to that used for the
1:50,000 geological map of Italy. In fact, as indicated
above, the four different phases recognised in the evol-
ution of the volcano are related to changes in the style
of activity and may or not correspond to the presence
of unconformable surfaces between the deposits at the
scale of the entire edifice. In fact, the nature itself of
volcanic activity, largely discontinuous in time, results
in the frequent formation of multiple, local or more
extended erosional surfaces both during the activity
within a single phase or due to events that mark the
passage from a phase to another.
4.1. Phase 1: Building of the Somma
stratovolcano (ca. 39 ka –22 ka)
Alternating lava flows and scoria deposits form the
Somma stratovolcano, cropping out extensively along
the upper slopes of Mt. Somma (see geological sketch
in the main map and Figure 3) and on the scarp of
the Somma caldera (Figure 1(A)). The sequence
exposed on the caldera wall evidences two main
units: (i) a lower unit, mostly represented by weathered
scoria beds and, (ii) an upper unit, formed by an alter-
nation of thin lava flows and scoriae topped by para-
sitic cones (LSC in the main map; Figure 1(C)). The
stratigraphic succession is locally crosscut by several
dykes, up to a few metres thick (Marinoni, 2001;
Porreca et al., 2006). Few parasitic scoria and spatter
cones are located on the lower slopes of Mt. Somma
and in the surrounding plain buried under younger
pyroclastic and volcaniclastic deposits. These have
morphological evidences and crop out both in the
southern and eastern sectors, in the Pompei and in
the Palma Campania areas, respectively.
This sequence (LPG and LSC in the main map;
Figure 1(A,C)), representing the oldest outcropping
products of the Somma volcanic successions, is uncon-
formably covered by the units of Phase 2, dominated by
explosive activity, which partially infill deep valleys
eroded on the Somma flanks (especially in the northern
sector or in the higher slopes of the eastern sector) or
mantle the interfluves. The products of this activity
are not exposed in the southern and western sectors
of the volcano, except in few quarries in the areas of
Boscoreale, where they are covered by a 20–30 m
thick pyroclastic succession of the following activity.
4.2. Phase 2: Caldera formation (22 ka –AD 79)
During this period, at least four major Plinian erup-
tions and several lower intensity eruptions occurred.
Major Plinian eruptions (Pomici di Base, Mercato,
Avellino and Pompeii) were responsible of the shaping
of the summit caldera (Cioni et al., 1999). Summit cal-
dera collapses occurred after each Plinian eruption,
each centred at slightly different locations roughly
aligned along an E-W direction (Figure 3). The depos-
its of these Plinian eruptions are always characterised
by fall beds of pumice and lithics, usually alternating
with and followed by deposits of dilute to concentrate
PDC. Fall deposits dominate the eastern and north
eastern flanks of the volcano, reflecting the direction
of the dominant stratospheric winds (Plate I). PDC
deposits are dispersed along the entire slopes of the vol-
cano, from an elevation of about 500 m down to the
nearby plain, where they are interstratified with the
volcanoclastic deposits (forming the Somma-Vesuvius
apron).
The PDC deposits show largely variable sedimento-
logical features, from massive to stratified deposits, and
from ash-dominated to breccia-like deposits. The
maximum thickness of these deposits generally
coincides with the termination of the main paleoval-
leys, where they form pyroclastic fans reaching a thick-
ness of several metres. Thinly stratified deposits from
dilute PDCs are also widely exposed on Somma slopes,
irrespective of the paleotopography of the volcano. The
stratigraphic relationships between the deposits of the
different eruptions are complex, as they occupy
paleo-depressions often cut into the deposits of the pre-
vious eruptions, resulting in a complex geometry with
lateral or vertical superposition of units from different
eruptions. Phase 2 deposits also comprise the products
of a few subplinian events (Pomici Verdoline, AP1 and
144 A. SBRANA ET AL.
AP2 eruptions) mainly characterised by fall beds, with
only minor PDC deposits. Ash deposits from long-last-
ing ash emission activity (AP3, AP4, AP5) locally form
thick deposits on the eastern slopes of the volcano. In
the time interval between 22 and 19 ka, activity along
several eruptive fractures fed by latitic magmas formed
spatter and scoria cones and minor lava flows along the
San Severino valley (NE of slopes) and in the area
upslope of Pollena village (NW Somma slopes). In
the stratigraphic succession, sporadic tephra layers of
possible Somma-Vesuvius provenance are also present
(MA1 and MA2) as well as of at least two major erup-
tions of Phlegrean Fields (Agnano Pomici Principali
and Agnano Monte Spina Plinian eruptions; Rosi &
Sbrana, 1987; de Vita et al., 1999). As a whole, the pro-
ducts of this phase represent the majority of the out-
cropping deposits along the northern and eastern
slopes of the volcano, while they are mainly covered,
in the western and southern sectors, by the deposits
of the following phases.
4.3. Phase 3: Post-caldera activity (AD 472 –AD
1631)
Phase 3 deposits are the result of the post-caldera
activity, which comprises several eruptions mainly
sourced inside the caldera. Volumetrically, this activity
is dominated by the deposits of the two subplinian
eruptions of AD 472 (Pollena, PPL) and AD 1631
(PMX). Both eruptions were characterised by easterly
to north easterly dispersed fall beds, followed by PDC
deposits spreading all over the volcano slopes (PPL)
or only over its western and southern slopes (PMX).
The absence of AD 1631 PDC deposits on the northern
Somma slopes indicates they had not enough energy to
overpass the caldera wall. These AD 1631 PDC depos-
its are mainly represented by massive, poorly sorted,
valley-pond units, usually showing a large proportion
of block-sized material (both juvenile and lithic),
which flowed following the main valleys and forming
pyroclastic fans at the break in slope to the plain sur-
rounding the volcano. These PDC contributed to
bury the Villa of Emperor August, I-IV century, that
survived to the AD 79 eruption (Perrotta, Scarpati,
Luongo, & Aoyagi, 2006). Although Phase 3 deposits
are dominated by the products of the AD 472 and
AD 1631 eruptions, an important high-frequency,
mid- to low-intensity activity also occurred between
the two events. This activity is locally recorded,
especially in the eastern sector, by a succession of lapilli
and ash fallout layers only separated by minor
reworked beds or erosional surfaces. This activity,
started in AD 512, and lasted at least up to XII century.
Lava flows vented from inside the caldera first over-
passed the southern (and lower altitude) rim of the cal-
dera approximately during the XI century activity,
invading the southern and then the western slopes of
the volcano (Paolillo et al., 2016;Principe et al.,
2004). An important effusive activity possibly also
accompanied the VI to X century explosive activity,
being confined inside the caldera and not evident on
the outer slopes of the volcano. Minor scoria cones,
Fossa Monaca and Viulo vents, on the lower southern
slopes of the volcano were also built up during this
period.
4.4. Phase 4: Vesuvius cone (post 1631–1944)
The AD 1631 eruption marked an important change in
the style of activity of the volcano, whose activity
rapidly resumed with a nearly continuous open-con-
duit activity. Lava effusion and low-intensity explosive
activity characterised this period, which was also punc-
tuated by violent strombolian eruptions (Arrighi, Prin-
cipe, & Rosi, 2001;Marianelli et al., 2005;Santacroce,
1983). The present Vesuvius cone is the result of lava
and tephra accumulation during this period of activity
(Figure 7(A)). Although being prevalently focused in
the central part of the caldera, effusive activity some-
times issued from vents on the flanks of Vesuvius
cone or close to its base, and in some cases also outside
of the caldera, along the slopes of the volcano (Principe
et al., 2004). The products of this activity are collec-
tively indicated in the main map and in Figure 3 as
Phase 4. The witnesses of this activity are the large
lava flows flowing down from the caldera border to
cover the southern and western sectors of the volcano.
Most of these lava flows can be recognised through
their morphology and attributed to the related erup-
tions thanks to the huge literature existing for the
area since the XVIII century.
5. Final remarks and conclusions
The new volcanological map of the Somma-Vesuvius
Complex presents a novel, exhaustive picture of the
volcanic structures, geological history, and distribution
of effusive and explosive deposits. The map represents
the basic document for a correct reconstruction of the
past activity and a guide for the possible impact on the
territory in case of a future reactivation of the volcano.
Hence, we expect that the geological map (main map)
and the associated table presenting the dispersal of fall-
out and PDC deposits of a large number of past events
(Plate I) can become a reference for any future, long-
term, territorial planning and assessment of volcanic
hazard in the area.
In this new map, the volcano activity is framed in
different phases aimed to increase detail of the deposits
of the numerous eruptions of the past 22 ka of the vol-
cano, and to give an easier and more effective interpret-
ative key of the volcano evolution. With respect to the
other available maps of Vesuvius area, the proposed
grouping of the different litostratigraphic units into
JOURNAL OF MAPS 145
some main phases, and the picture given by Plate I of
the impact related to the main past explosive eruptions,
represent in our opinion an important added value, as
they offer a clearer and direct view of the changes
occurred in the volcano through time. Easiness of read-
ing and directness of the message brought by the large
amount of geological information conveyed by the
main map and Plate I are particularly important not
only for their scientific content, but also for a correct
dissemination of the available knowledge on the volca-
nic area, of absolute relevance for increasing the aware-
ness of the several hundred thousand inhabitants living
on the volcano slopes and the nearby plain.
Software
ESRI ArcGIS® 10.6 was used to produce the digital
elevation model, to collect all data in GIS, and to create
new features. The design of the final map layout was
created using Adobe Photoshop® CC 2018 and Adobe
Illustrator® CC 2018.
Acknowledgements
The contribution of the CAR.G Project team, the Geological
Survey of Italy, and the Istituto Superiore per la Protezione e
la Ricerca Ambientale (ISPRA) and Regione Campania are
acknowledged in the map. The authors are grateful to
Heike Apps, José Luis Macías, Guido Ventura and Claudio
Riccomini for their constructive comments and suggestions
that helped to improve the quality of the manuscript.
Disclosure statement
No potential conflict of interest was reported by the authors.
Funding
This work was financially supported by the University of
Pisa, grants to A. Sbrana and PRA 2018–19.
ORCID
Alessandro Sbrana http://orcid.org/0000-0003-1373-0603
Raffaello Cioni http://orcid.org/0000-0002-2526-9095
Paola Marianelli http://orcid.org/0000-0001-9535-8635
Roberto Sulpizio http://orcid.org/0000-0002-3930-5421
Daniele Andronico http://orcid.org/0000-0002-8333-1547
Giuseppe Pasquini http://orcid.org/0000-0002-1981-1191
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