Volcanology of Ischia (Italy)

Abstract

A volcanological map of the active Ischia volcanic field that includes Vivara Island is presented. The volcanological map is at the 1:10,000 scale and is based on 1:5000 field mapping, geological CAR.G data, and new volcanological studies. Geological data are represented on the three-dimensional orographic background digital terrain model of the inland and offshore areas of the volcanic field. This allows a better visualization of the main morphological, volcanic, and geological structures. Six phases were identified on the basis of volcanotectonic events; the 110 volcanic units were arranged following these evolutive phases, and a volcanosedimentary apron unit was introduced. This volcanological map enables visualization of the volcanic evolution of the Ischia volcanic field and could be useful for the evaluation of volcano-related hazards in the area.

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Volcanology of Ischia (Italy)
Alessandro Sbrana, Paola Marianelli & Giuseppe Pasquini
To cite this article: Alessandro Sbrana, Paola Marianelli & Giuseppe Pasquini (2018) Volcanology
of Ischia (Italy), Journal of Maps, 14:2, 494-503, DOI: 10.1080/17445647.2018.1498811
To link to this article: https://doi.org/10.1080/17445647.2018.1498811
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Science
Volcanology of Ischia (Italy)
Alessandro Sbrana, Paola Marianelli and Giuseppe Pasquini
Dipartimento di Scienze della Terra, Università di Pisa, Pisa, Italy
ABSTRACT
A volcanological map of the active Ischia volcanic field that includes Vivara Island is presented.
The volcanological map is at the 1:10,000 scale and is based on 1:5000 field mapping, geological
CAR.G data, and new volcanological studies. Geological data are represented on the three-
dimensional orographic background digital terrain model of the inland and offshore areas of
the volcanic field. This allows a better visualization of the main morphological, volcanic, and
geological structures. Six phases were identified on the basis of volcanotectonic events; the
110 volcanic units were arranged following these evolutive phases, and a
volcanosedimentary apron unit was introduced. This volcanological map enables visualization
of the volcanic evolution of the Ischia volcanic field and could be useful for the evaluation of
volcano-related hazards in the area.
ARTICLE HISTORY
Received 10 April 2018
Revised 6 July 2018
Accepted 6 July 2018
KEYWORDS
Volcanological map; volcanic
field; digital terrain model;
Ischia; Vivara; Italy
1. Introduction
Ischia Island represents the emerged portion of a wide
volcanic field (Bruno, de Alteriis, & Florio, 2002;Orsi,
Gallo, & Zanchi, 1991) extending from the continental
slope (facing westward on the Tyrrhenian batial plain)
to the continental volcanic area of Campi Flegrei. It is
part of the Phlegraean Volcanic District (Orsi, De Vita,
& Di Vito, 1996), the most widespread active volcanic
system of the Mediterranean area, developed inside the
Campanian Plain half graben. The PVD formed fol-
lowing the opening of the Tyrrhenian basin, along a
system of regional transfer faults, affecting the Tyrrhe-
nian side of the Apennine chain during the Neogene
Quaternary evolution of the area (Sartori, 2003;Scan-
done, 1979); it comprises (Figure 1(A, B)) two big vol-
canic fields, Ischia and Campi Flegrei, fed mainly by
evolved alkaline magmas and the minor volcanic field
of Procida, characterized by trachybasaltic–shoshonitic
monogenic tuffand scoria cones and minor lavas
(Brown et al., 2014;D’Antonio et al., 2013;Paoletti,
D’Antonio, & Rapolla, 2013; and references therein).
Previous detailed Ischia geological maps include the
1:10,000 geological map of Rittmann (1930),Rittman
and Gottini (1980) and the 1:10,000 map of Vezzoli
(1988). The description of the Mt Epomeo resurgent
block as being a result of a volcanotectonic mechanism,
the mapping of lahars, and the reconstruction of the
sequence of events were described in pioneering
works of Rittmann. Recent volcanism is well detailed
in Vezzoli (1988); in its geological map, a coherent stra-
tigraphic framework of the volcanic events is based on
a complete dataset of absolute ages (Gillot, Chiesa,
Pasquarè, & Vezzoli, 1982). In a more recent paper,
Brown, Orsi, and De Vita (2008) detail the strati-
graphic framework between 75 and 50 ka, highlighting
that volcanism was very active in this period.
New geological maps of the volcano were recently rea-
lized in the framework of the CAR.G Project (Regione
Campania, 2011;Servizio Geologico d’Italia, 2018).
These maps significantly improve the stratigraphy of
whole successions, absolute ages, the mapping of units,
recognition of eruptive centers, and knowledge of the cal-
dera resurgence and of relations of uplift phenomena and
related epiclastic forming around the resurgent block.
Deposits that are the result of sector collapse of resurgent
block flanks are traced and mapped both on land and in
the marine areas surrounding Ischia.
Based on the CAR.G data and on new volcanological
studies, an updated volcanological map of the Ischia vol-
canic field that includes Vivara Island was generated in
this study. Geological data were placed on the three-
dimensional (3D) orographic background digital terrain
model(DTM)oftheinlandandoffshore areas of the vol-
canic field. This enables a better visualization of the vol-
canic structure. The design of the legend on the basis of a
simplified lithology and of volcanological features, clar-
ifies the reading of the map as well as the comprehension
of volcanological evolution of the field. Furthermore,
normal faults related to caldera resurgence (induced by
magma injection) were distinguished from regional and
normal faults interesting the whole volcanic field.
This new volcanological map should be very useful for
the following reasons. The intensely urbanized island is
environmentally very fragile because its morphology
© 2018 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 Dipartimento di Scienze della Terra, Università di Pisa, via S. Maria 53, 56126 Pisa, Italy
JOURNAL OF MAPS
2018, VOL. 14, NO. 2, 494–503
https://doi.org/10.1080/17445647.2018.1498811

and the activity of the volcano induce hazards related to
volcanic events, such as destructiveearthquakes (the last
occurred in 2017 causing several casualties (De Novellis
et al., 2018), formation of mud flows and landslides, sec-
tor collapses and related debris avalanches linked tovol-
canotectonic uplift (De Vita, Sansivero, Orsi, & Marotta,
2006) and subsidence phenomena, and general volcanic
deformation processes.
2. Volcanic field history
Volcanic fields develop in both continental and mar-
ine environments (Passaro, De Alteriis, & Sacchi,
2016). Volcanic successions outcropping on the Ischia
Island register a long history, dating from more than
150 ka ago (Gillot et al., 1982;Vezzoli, 1988)tothe
present; the last erupted deposits (Arso lavas and pyr-
oclastics) date to 1301–1302 AD (Rittman & Gottini,
1980).
Volcanism develops through the building of a volca-
nic field made mainly by monogenic volcanoes (tuff
cones, scoria cones, spatter cones and spatter ramparts,
lava domes and lava flows) dispersed over an area of
250 km
2
(Figure 2). Volcanics have mainly trachytic
compositions (Vezzoli, 1988), whereas trachybasalts
and shoshonites characterize few deposits. Several pyr-
oclastic units emplaced during paroxysmal eruptions
were mapped on the island and traced in submarine
areas up to the nearby Campi Flegrei volcanic field,
which is covered by several of these volcanic units
Figure 1. A: Phlegrean Volcanic District (Google Earth image). B: Phlegrean Volcanic District, view from Ischia. In the foreground
Castello d’Ischia spatter cone, followed by the Vivara tuffring, by Procida volcanic field, and in the background, continental Phle-
grean Fields and Somma-Vesuvius volcano. C: Castello d’Ischia spatter cone, view from North. D: Porticello cliff(southeastern island),
deposits of Secca d’Ischia offshore volcano (see Figure 2). E: Pietra Martone, Mt. Epomeo Green Tuff. In picture note the normal fault
wall of the resurgent block and the scar of debris avalanche.
JOURNAL OF MAPS 495

(Sbrana, Fulignati, Marianelli, Boyce, & Cecchetti,
2009;Sbrana et al., 2011;Servizio Geologico d’Italia,
2018). Some of these, which occurred between 60 and
56 ka ago, are linked to the Ischia caldera formation
(Brown et al., 2008;Carlino, Cubellis, Luongo, &
Obrizzo, 2006;Sbrana et al., 2009;Vezzoli, 1988; and
references therein).
The uplift of a resurgent block (Mt Epomeo) charac-
terizes the central portion of the caldera (Acocella &
Funiciello, 1999;Carlino, 2012;Carlino et al., 2006;
Orsi et al., 1991;Sbrana et al., 2009;Tibaldi & Vezzoli,
2004 and references therein). This block, tilted south-
ward and fragmented in smaller blocks, is delimited
by conjugate systems of faults at SW of Mt Epomeo
(Main Map). The resurgence deeply influenced the
morphology and geology of the volcanic field also
with the formation of an epiclastic and volcanic
apron all around Mt Epomeo. Several epiclastic units,
interlayered with volcanic deposits, were identified
during the geological survey and were linked to sector
collapses inducing debris avalanches, and accelerated
erosion phases of the resurgent block. Several authors
(Carlino, 2012;Carlino et al., 2006;Rittmann, 1930;
Sbrana et al., 2009; and references therein) link the
resurgence of Mt Epomeo and the volcanic activity
around the block to a laccolith-shaped shallow
magma body. The faulting mechanism evidenced in
the Main Map is induced by emplacement at very
Figure 2. Geological and structural sketch map of Ischia volcanic field. Deposits of debris avalanches and volcanic vents are high-
lighted in marine areas. Location of toponyms (numbered dots) cited in the main text is also reported.
496 A. SBRANA ET AL.

shallow depths of apophyses of the magmatic intrusion
that drove resurgence (Sbrana et al., 2011). Other
authors explain the structure of the resurgence by an
increase in pressure in a shallow magma chamber
using a trapdoor model (Acocella & Funiciello, 1999)
or a simple shear model (Orsi et al., 1991).
The volcanological studies and seismic surveys per-
formed in marine areas show clearly that in Ischia, stra-
tigraphic sequences are present in numerous units
derived from eruptive vents located in the marine
areas surrounding the island; among these are the pyr-
oclastic units of volcanoes of Secca d’Ischia, Citara,
Sant’Angelo, Monte Cotto and San Michele, Grotta
dello Spuntatore, San Montano, and the Plinian depos-
its of Russo units (Sbrana et al., 2011).
During the last phase of activity, uplifts and subsi-
dences affected the volcanic field. On the northern
side of the island, marine terraces and shoreline fossi-
liferous sediments recorded an uplift of about 60 m
after 5.5 ka; structural terraces affected the southern
side of the island facing the Maronti shore at similar
heights, whereas uplifted ancient shorelines are evident
in the Forio area on the west side of the island, and fur-
rows are present on the southeast marine cliffs between
Sant’Angelo and Chiarito.
After the Roman era, subsidence affected the island.
The Roman small town of Aenaria (the ancient name
of Ischia), dating back to 200 BC, is presently sub-
merged 6 m east of the island. A general trend of
slow subsidence of the island, with a maximum value
of about 1 cm/yr, has been recorded by GPS network
and DInSAR data since 1992 (De Martino et al.,
2011;Manzo et al., 2006). Intense hydrothermalism
(Chiodini et al., 2004) and volcanotectonic earthquakes
characterize the island (De Novellis et al., 2018).
3. Methods
The first step toward the realization of this volcanolo-
gical map was the generation of the data necessary for
preparing the topographic 3D base map.
The inland 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 project
DTM (5 × 5 m, years 2004–2005). These two digital
elevation models were next overlapped to create a rea-
listic tridimensional effect, using Adobe Photoshop
CS6. The high-resolution Lidar DTM, (see http://sit.
cittametropolitana.na.it/lidar.html), was also used to
check the location of geomorphological elements
such as faults, fractures, crater rims, and scars.
The topographic contour lines (http://sit.
cittametropolitana.na.it/) were derived from the
smoothing and contouring process on the ORCA DTM.
The offshore bathymetric reconstruction was based
on the map of De Alteriis, Tonielli, Passaro, and De
Lauro (2006) and of Passaro et al. (2016).
The orographic background of inland and offshore
areas constitute the raster base of the map. The map
was completed by extracting the buildings and the
main road features from the Open Street Map (OSM)
database, through the OSM plugin for Quantum GIS
(QGIS Desktop 2.18.12).
The data source (CAR.G geological maps) covers the
land and marine areas of the volcanic field. The CAR.G
surveys were realized at the 1:5000 scale. During the
geological survey, the guidelines issued by the Italian
Geological Survey were followed, using unconformity
bounded stratigraphic units (UBSU), delimitated on
the basis of the presence of evident, demonstrable,
and significant unconformities.
All the volcanic, epiclastic, and sedimentary units
mapped in CAR.G geological surveys are reported in
this new volcanological map. Thus, the details of the
geological surveys (made in the field at the 1:5000
scale) were maintained.
In this study, all data were stored and generated in a
geographical information system (GIS) developed with
ESRI ARCGIS 10.2.2, using the cartographical refer-
ence system WGS 84-UTM 33N. Data generation in
a GIS environment enables the production of the fol-
lowing thematic layouts: topographic and bathymetric
contour lines; polygonal and linear base map elements;
and polygonal, linear, and punctual features for volca-
nological, geological, and geomorphological elements
and location of fumaroles and springs.
All these vector layers were exported and graphically
managed with Adobe Illustrator CS6, to obtain the final
map layout at the scale 1:10,000.
4. Results and discussion
4.1. Phases of activity and associated
volcanological units
About 110 volcanic units were identified and arranged
in the volcanological legend map, following the six evo-
lutive phases identified on the basis of volcanotectonic
events (caldera formation, resurgence phases of Mt.
Epomeo) and of periods of stasis, in the history of
the volcanic field (Figure 3).
In each phase, the volcanic units are distinguished in
deposits linked to explosive or to effusive activity. Fur-
thermore, a volcanosedimentary apron succession was
introduced in the map legend to point out the role of
the resurgent block in the volcanological evolution of
Ischia.
4.1.1. Phase 1: Building of the Ischia volcanic field
(>150–73 ka ago)
The deposits of the building of the Ischia volcanic field
are grouped in the first phase. This activity spanned
from about >150–73 ka ago (Figure 3). The oldest
units of the volcanic field are linked mostly to
JOURNAL OF MAPS 497

monogenic tuffcones, lava domes, spatter cones
(Figure 1(C)), and lava flows. The Vivara trachybasaltic
tuffring (Figure 1(A)) also formed during this phase.
Afterward, Plinian eruptions (La Carrozza unit)
occurred. Their deposits are covered by thick lava
fountains deposits, related to eruptive fractures (Tor-
one, Monte di Vezzi, 130 ka). At around 117 and
100 ka ago, lava flows and lava domes were emplaced.
An explosive paroxysm is recorded in the volcanic suc-
cessions around 100 ka ago; deposits of Plinian events
form L’Elefante and Spiaggia d’Agnone units. The vol-
canic field building continued up to 73 ka ago, with the
emplacement of lava domes and lava flows.
4.1.2. Phase 2: Ischia caldera forming and filling
(60–<56? ka)
Caldera-forming paroxistic phase (60–56 ka ago).
Around 60 ka ago, several layers of pumice-rich depos-
its intercalated by paleosoils, the Pigniatiello For-
mation (Rosi, Sbrana, & Vezzoli, 1988) blanketed the
southern and eastern sectors of Ischia, Vivara, and Pro-
cida islands and the continental Campi Flegrei volcanic
field, east of Ischia. At Vivara, deposits of mafic scoria
cones outcrop at the bottom and top of the Pigniatiello
Formation without evidence of stasis. These deposits
are linked to volcanoes that are submerged today in
the area between Castello d’Ischia and Vivara Island,
Figure 3. Simplified chronostratigraphic sequence (not to scale) of Ischia volcanic field. For the meaning of labels of units, see the
Legend in the Main Map.
498 A. SBRANA ET AL.

respectively, the Formiche di Vivara and Catena volca-
noes (Figure 2). The Pigniatiello Formation was fol-
lowed by explosive eruptions of high magnitude that
formed an ignimbrite plateau (58–56 ka ago), continu-
ous in marine areas all around the island and extends
to Campi Flegrei. On the island, these are present as
welded ignimbrites and breccias. These eruptions
induce the Ischia caldera collapse. At least three tuffac-
eous units, named Pizzone, Frassitelli, and Tufo Verde
dell’Epomeo ponded inside caldera are recognized.
These constitute the succession of the uplifted block
located at the caldera center (see Phase 3). The intracal-
dera tuffs appeared to be intensely hydrothermalized. A
submarine volcano (Secca d’Ischia) forms in the south-
eastern offshore of the Ischia volcanic field (Figure 2)at
the end of this paroxysmal phase. Thick deposits of this
volcano cover the southeast hills of the island (Figure 1
(D)) and can also be found inside the eastern portion of
the Ischia caldera, in the Scarrupata di Barano area.
Epiclastic caldera filling (<56–? ka ago). After the
caldera collapse, an important stasis in volcanism is
observed. In this period, erosion and epiclastic sedi-
mentation in marine environment partially filled the
Ischia caldera depression. The span of the stasis is
not well defined, but several epiclastic and sedimentary
units, more than 100 m thick, cover (Main Map) the
upper tuffs of the sin-caldera succession (Epomeo
Green tuff, 56 ka). This suggests a relatively long period
of rest interrupted by the volcanism resumption
(Citara tuffs, Phase 3, 45 ka ago).
4.1.3. Phase 3: Postcaldera activity and caldera
resurgence (<56?–33 ka ago)
After collapse and partial epiclastic filling, a fast resur-
gence of the caldera center started. The beginning of
resurgence is not well constrained by absolute age or
stratigraphic data. In any case, there is geological evi-
dence that 33 ka ago, the center of the caldera (Mt Epo-
meo) was uplifted at least 600 m (Sbrana et al., 2009).
In the southwestern sector of the resurgent block
(Figure 1(E)), field surveys show that the intracaldera
tuffs of the paroxysmal phase of activity (Phase 2)
appear discordantly covered by yellow tuffs dated to
33 ka ago that sealed the normal fault plane of the
resurgent block, thus enabling definition of the age of
the uplift movements. These pyroclastics are related
to the tuffcones aligned along the master faults of
the resurgent block. These data are evidence that the
first phase of resurgence occurred after the caldera col-
lapse and before 33 ka ago.
Resumption of volcanism after the caldera collapse
occurred around 45 ka ago with the Citara tuffcone
located in the western offshore area of the volcanic
field (Figure 2) after about 11 ka of stasis in volcanism.
In the same period (about 39 ka ago, De Vivo et al.,
2001), the supereruption in the Campi Flegrei volcanic
field known as the Campanian Ignimbrite (Marianelli,
Sbrana, & Proto, 2006) and the formation of the Campi
Flegrei caldera occurred. Deposits of this event (Tufo
Grigio Campano-Breccia Museo) are interlayered in
the Vivara successions covering a coarse fallout of the
Ischia caldera-forming phase (Phase 2).
Geological mapping and the absolute ages of volca-
nic deposits reveal that in this period, several eruptive
vents, scoria cones and tuffcones developed on the
normal faults driving the uplift of Mt. Epomeo resur-
gent block on the western, southwestern, and southern
sides. Furthermore, in this phase, several vents opened
in the western and southern marine areas (Main Map).
4.1.4. Phase 4: Renewal of volcanic activity (29–
13 ka ago)
After a repose period of about 8 ka, renewal of volcanic
activity occurred between 25 and 18 ka ago in the wes-
tern and southwestern sectors of the volcanic field. This
explosive activity included several Plinian pumice
deposits linked to source areas located offshore of the
island in the west (Russo pyroclastics). Meanwhile,
from the craters of La Nave and Pilaro, located on
the border of the continental slope in the west sector
of the island, thick layers of spatters and pumiceous
breccias (Scarrupata di Panza and La Nave units, etc.)
were emplaced.
During this timespan (about 18 ka) basaltic magmas
fed the tuffcone of Solchiaro (east of Vivara on the
Procida volcanic field) just before the eruption of the
dome and lavas of St. Anna, and the pumice sheets of
Mormile linked to violent strombolian and/or sub-Pli-
nian eruptions from vents east of the resurgent block.
The emplacement of the domes of Costa Sparaina
and Trippodi occurred between 16 and 13 ka ago on
the eastern master faults of the Epomeo resurgent
block.
4.1.5. Phase 5: New phase of Mt. Epomeo and
uplift (10–5 ka ago)
Between 10 and 6 ka ago, monogenic volcanoes or vol-
canic complexes were active mainly in the northern
and eastern sectors of the island. Lava domes and
lava flows formed at east, north-east: Selva del Napoli-
tano, Fundera, and Zaro complex. Tuffcone activity
occurred at Casamicciola, Cava del Puzzillo, and Villa
Arbusto, where explosive hydromagmatic centers, yel-
low tuffcones, are activated. The phase was closed by a
phreatoplinian eruption, the Piano Liguori unit
(5.6 ka), which caused the emplacement of a thick
cover of ashy layers. These deposits mantle all the
southeastern reliefs of the island. The source area,
which possibly subsided or collapsed after the eruption,
is hypothesized to be between the Arso vent and the
Montagnone dome (De Vita, Sansivero, Orsi, Marotta,
& Piochi, 2010).
During this phase and the successive Phase 6, several
debris avalanche deposits, followed by thick sequences
JOURNAL OF MAPS 499

of debris flows and landslide deposits, were emplaced
because of sector collapses of the flanks of the Mt Epo-
meo resurgent block (see description in Section 2.2.7).
This fact and the presence of uplifted marine epi-
clastics suggest that a new phase of resurgence of the
central portion of the caldera and of some sector of
the island took place as a response to the refilling and
evolution of the shallow magmatic system of Ischia.
4.1.6. Phase 6: Historical phase (3.7 ka ago–1302
AD)
The volcanism in the Ischia volcanic field was very
intense in Greek and Roman times, up to the Middle
Ages; at least 15 volcanic edifices located mainly in
the eastern sector of the island were identified. They
are represented by complexes of domes and lavas
(Rotaro and Montagnone) with associated pyroclastics,
scoria and spatter cones of Vateliero, Molara, Cava
Nocelle, Punta della Cannuccia, Ischia Porto, and
Spiaggia degli Inglesi. Other mapped pyroclastic units
are not referable to a well-identified volcanic edifice.
This is particularly true for the pumice sheet of Cretaio
(Figure 4(A)) sub-Plinian eruption deposits that were
aged to 150 A.D. The coarse ashes of the Rotaro com-
plex mantle the Vivara island successions.
In 1302, the Arso eruption occurred with scoriae
spatter and lava flow. The presence of mixed/mingled
magmas (Piochi, Civetta, & Orsi, 1999) in the erupted
deposits, and the eruption of mafic magmas (Vateliero,
Punta della Cannuccia scoria cones) characterize this
last phase of activity. In this phase, the NE SW regional
(transtensional) fault system activates the rise of deep
mafic melts (Acocella & Funiciello, 1999;Sbrana
et al., 2011).
This phase appears to have been preceded by a gen-
eral uplift of the northern sector of the island as high-
lighted by the marine epiclastics (sands) and terraces
observed on the north coast from Bagnetielli to Mezza-
via vecchia.
4.2. Epiclastic apron associated to the Mt
Epomeo resurgent block
The morphologic evolution associated to the caldera
resurgence and its related earthquakes well explain
the formation and evolution of this unit. Sedimentary
apron deposits in areas surrounding the Mt Epomeo
resurgent block were derived by the removal of some
cubic kilometers of deposits that ponded inside caldera,
following sector collapses, accelerated erosion, and
landslide processes induced by the volcanotectonic
resurgence events.
Debris avalanches outcrop on the island (Figure 1
(E), Figure 2,Figure 4(B, C)) and extend to the marine
areas, reaching distances of 10 km from the coast to the
north and west, and about 40 km to the south (Chiocci
Figure 4. A: Sub-Plinian fallout deposit of 150 AD Cretaio eruption. B: Megaboulder in debris avalanche deposit at Cava Scura. C:
Debris avalanche deposit at Cava Acquara; note different megaboulders of tuff. D: aerial view of mud flow channel and deposits at
Monte di Vezzi (30 April 2006).
500 A. SBRANA ET AL.

& De Alteriis, 2006;De Alteriis et al., 2010). Their
deposits characterize the morphology of the inland
areas, where hummock morphologies develop and in
marine areas, where bathimetric, side-scan sonar and
reflection seismic surveys reveal the widespread pres-
ence of hummock-shaped chaotic deposits.
Geological data and absolute ages indicated that this
epiclastic apron was formed mainly during Phases 5
and 6. The age of formation of debris avalanches is
defined by De Alteriis et al. (2010) for the southern
debris avalanche (Bocca di Serra unit) as 2.7–5.2 ka;
the northern debris avalanche (Lacco Ameno unit) is
covered by marine sediments having an absolute age
of 5.8 ka. These sediments are today uplifted by at
least 60 m. Furthermore, the apron epiclastics are not
covered by younger volcanics.
These age indications correlate the increase in vol-
canism in the fifth to sixth phases and the eruption
of mafic magmas with the rejuvenation of volcanic,
magmatic, and associated seismic activity. This could
have induced a new phase of uplift/destabilization of
the resurgent block, triggering the sector collapse of
the western (Forio), northern (Casamicciola), and
southern (Serrara Fontana) sides of the resurgent
block. Debris avalanche deposits are covered by thick
sequences of debris flow, mud flows, and landslides.
Debris flow and mud flow deposits appear because of
increased erosion, whereas earthquakes favor the for-
mation of landslide deposits that are widely distributed
on the apron.
5. Final remarks and conclusions
The volcanological map of Ischia and Vivara placed on
3D DTM represents a contribution to the reconstruc-
tion of the volcanic evolution of the Ischia volcanic
field. The general interest in this volcanological map
derives from the fact that Ischia represents a good
example of an active and dangerous volcanic field
with a big caldera structure that is affected by huge
and rapid resurgence.
The cartographic representation of the units
placed on 3D DTM shows the morphology of the vol-
canoes not covered by successive deposits. For
instance, the climax of activity of Phases 5 and 6
resulted in multiphase dome complexes (the Rotaro
and Montagnone domes), whose morphological
structure is particularly evident, as well as the lava
flowsofZaroandArso.Themapalsoindicatesthe
tephra blankets of the Plinian and sub-Plinian units
of the last phase of activity.
In this volcanological map is particularly evident the
morphology induced by the resurgent block and conse-
quent apron development, both inland and in marine
areas of the Ischia volcanic field, where debris ava-
lanche deposits and debris flows model the surface
shapes.
The resurgence phenomena expose very thick
explosive pyroclastics emplaced during the caldera
collapse, highlighting the processes of hydrothermal
alteration inside the caldera as a result of huge ther-
mal anomaly.
Post resurgence volcanism occurs along the active
high-angle normal faults that drive the Mt Epomeo
uplift (Figures 1(E) and 2), and in the whole volcanic
field. This represents a very important case-study of
caldera that was affected by large and fast uplift since
recent geological time (Di Giuseppe, Troiano, & Car-
lino, 2017;Sbrana et al., 2009). This process is associ-
ated to high volcanic hazard (Carlino, 2012) due to
the extensive urbanization of the island and surround-
ings. In fact, some of the volcanotectonic faults mapped
in this volcanological map are seismogenetic in recent
times: e.g. the 1883 and 2017 destructive earthquakes
were located on the faults bordering the resurgent
block south of Casamicciola (Figure 2).
Afinal remark addresses the importance of this map
for the mitigation of volcanic, seismic, and geological
hazards that deeply affect the island, e.g. recent
mudflows (Figure 4(D)). This volcanological map,
being focused on the distribution of deposits, their
age, and their geographical distribution, represents a
tool for defining specific risk maps for this densely
inhabited island.
Software
ESRI ArcGIS 10.2.2 was used to elaborate the digital
elevation model, to collect all the vectorial information
in a GIS, and to create new features. Quantum GIS
(QGIS Desktop 2.18.12) was used to extract the base-
map elements through the OSM plugin. The design
of the final map layout was performed using Adobe
Photoshop CS6 and Adobe Illustrator CS6.
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 is
acknowledged in the map. The authors are grateful to Ste-
fano Carlino, Makram Murad-al-shaikh and Salvatore Pas-
saro for their constructive comments, suggestions and
criticisms 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.
JOURNAL OF MAPS 501

ORCID
Paola Marianelli http://orcid.org/0000-0001-9535-8635
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