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The Lami succession piled up during the explosive activity of the Monte Pilato on Lipari Island (Central Aeolian Arc, Italy). It comprises a repetitive alternation of fall and pyroclastic density current beds, which define 13 Units separated by fine ash beds. Despite the homogeneous rhyolitic composition the juveniles fragments show strong textural heterogeneities from highly vesicular pumice to dense black obsidians. The pumice types are termed: i) "tube", which shows elongated tubular vesicles, ii) "frothy", highly vesicular with large, sub-rounded vesicles, and iii) agglomerated and welded. Two types of obsidian pyroclasts are recognized: i) aphyric black obsidian, and ii) grey obsidian showing spherulitic texture. All these pyroclastic types occur throughout the stratigraphic succession, and mixed in the same bed. They account for changing physical conditions along the conduit, which is hypothesised to be filled by a melt plug during the eruption of 12 out of 13 Units. The strong textural heterogeneities of the juvenile fragments testify for the existence of differential shear rates, which can be explained though two shear mechanism: i) simple shear, producing horizontal zonation of texture in the conduit with black obsidians along the conduit walls passing to tube and frothy pumice to the centre, and ii) pure shear, producing a vertical zonation in the conduit, with black obsidians at the top overlying frothy pumice. Agglomerated and welded pumice of Unit 13 is thought to represent the portion of magma heated by a batch of hotter melt that entered the magma chamber and triggered the eruption. The deposits of Unit 13 represent a unique case of spatter accretion due to accumulation of hot, low-viscous rhyolitic pumice fragments, emplaced from pyroclastic fountaining. © 2010 Elsevier B.V.

Caron B.,University Paris - Sud | Sulpizio R.,CIRISIVU | Siani G.,University Paris - Sud
Comptes Rendus - Geoscience | Year: 2010

We present in this work a tephrostratigraphic record from a sediment piston core (JO 2004) from Lake Ohrid. Five tephra layers were recognised, all from explosive eruptions of southern Italy volcanoes. A multidisciplinary study was carried out, including stratigraphy, AMS 14C chronology and geochemistry. The five tephra layers were correlated with terrestrial proximal counterparts and with both marine and lacustrine tephra layers already known in the central Mediterranean area. The oldest is from Pantelleria Island (P11, 131 ka BP). Other three tephra layers are from Campanian volcanoes: X6, Campanian Ignimbrite-Y5 and SMP1-Y3 (107, 39 and 31 ka BP respectively). The youngest tephra layer corresponds to the FL eruption from Etna Volcano (3.4 ka BP). In three cases these recognitions confirm previous findings in the Balkans, while two of them were for the first time recognised in the area, with a significant enlargement of the previous assessed dispersal areas. © 2010 Académie des sciences.

Sulpizio R.,CIRISIVU | Vogel H.,University of Cologne | Wagner B.,University of Cologne
Biogeosciences | Year: 2010

Four cores from Balkans lakes Ohrid and Prespa were examined for recognition of tephra layers and cryptotephras, and the results presented along with the review of data from other two already published cores from Lake Ohrid. The six cores provide a previously unrealised tephrostratigraphic framework of the two lakes, and provide a new tephrostratigraphic profile (composite) for the Balkans, which spans from the end of the Middle Pleistocene to the AD 472. A total of 12 tephra layers and cryptotephras were recognised in the cores. One is of Middle Pleistocene age (131 ka) and correlated to the marine tephra layer P-11 from Pantelleria Island. Eight volcanic layers are Upper Pleistocene in age, and encompass the period between ca. 107 ka and ca. 31 ka. This interval contains some of the main regional volcanic markers of the central Mediterranean area, including X-6, X-5, Y-5 and Y-3 tephra layers. The other layers of this interval have been related to the marine tephra layers C20, Y-6 and C10, while one was for the first time recognised in distal areas and correlated to the Taurano eruption of probable Vesuvian origin. Three cryptotephras were of Holocene age. Two of which have been correlated to Mercato and AD 472 eruptions of Somma-Vesuvius, while the third has been correlated to the FL eruption from Mount Etna. These recognitions provide a link of the Ohrid and Prespa lacustrine successions to other archives of the central Mediterranean area, like south Adriatic, Ionian, and south Tyrrhenian seas, lakes of southern Italy (Lago Grande di Monticchio, Pantano di San Gregorio Magno and Lago di Pergusa) and Balkans (Lake Shkodra). © 2010 Author(s).

Sulpizio R.,CIRISIVU | Van Welden A.,Laboratoire Of Geodynamique Des Chaines Alpines
Journal of Quaternary Science | Year: 2010

Two cores were recovered in the southeastern part of Lake Shkodra (Montenegro and Albania) and sampled for identification of tephra layers. The first core (SK13, 7.8m long) was recovered from a water depth of 7m, while the second core (SK19, 5.8m long) was recovered close to the presentday shoreline (water depth of 2m). Magnetic susceptibility investigations show generally low values with some peaks that in some cases are related to tephra layers. Nakedeye inspection of the cores allowed the identification of four tephra layers in core SK13 and five tephra layers in core SK19. Major element analyses on glass shards and mineral phases allowed correlation of the tephra layers between the two cores, and their attribution to six different Holocene explosive eruptions of southern Italy volcanoes. Two tephra layers have undersaturated composition of glass shards (foiditic and phonolitic) and were correlated to the AD 472 and the Avellino (ca. 3.9cal.ka BP) eruptions of SommaVesuvius. One tephra layer has benmoreitic composition and was correlated to the FL eruption of Mount Etna (ca. 3.4cal.ka BP). The other three tephra layers have trachytic composition and were correlated to Astroni (ca. 4.2cal.ka BP), Agnano Monte Spina (ca. 4.5cal.ka BP) and Agnano Pomici Principali (ca. 12.3cal.ka BP) eruptions of Campi Flegrei. The ages of tephra layers are in broad agreement with eight 14C accelerator mass spectrometric measurements carried out on plant remains and charcoal from the lake sediments at different depths along the two cores. The recognition of distal tephra layers from Italian volcanoes allowed the physical link of the Holocene archive of Lake Shkodra to other archives located in the central Mediterranean area and the Balkans (i.e. Lake Ohrid). Five of the recognised tephra layers were recognised for the first time in the Balkans area, and this has relevance for volcanic hazard assessment and for ash dispersal forecasting in case of renewed explosive activity from some of the southern Italy volcanoes. © 2009 John Wiley & Sons, Ltd.

Roverato M.,National Autonomous University of Mexico | Capra L.,National Autonomous University of Mexico | Sulpizio R.,CIRISIVU | Sulpizio R.,CNR Institute for the Dynamics of Environmental Processes | And 2 more authors.
Journal of Volcanology and Geothermal Research | Year: 2011

Throughout its history, Colima Volcano has experienced numerous partial edifice collapses with associated emplacement of debris avalanche deposits of contrasting volume, morphology and texture. A detailed stratigraphic study in the south-eastern sector of the volcano allowed the recognition of two debris avalanche deposits, named San Marcos (>28,000calyr BP, V=~1.3km3) and Tonila (15,000-16,000calyr BP, V=~1km3). This work sheds light on the pre-failure conditions of the volcano based primarily on a detailed textural study of debris avalanche deposits and their associated pyroclastic and volcaniclastic successions. Furthermore, we show how the climate at the time of the Tonila collapse influenced the failure mechanisms. The >28,000calyr BP San Marcos collapse was promoted by edifice steep flanks and ongoing tectonic and volcanotectonic deformation, and was followed by a magmatic eruption that emplaced pyroclastic flow deposits. In contrast, the Tonila failure occurred just after the Last Glacial Maximum (22,000-18,000cal BP) and, in addition to the typical debris avalanche textural characteristics (angular to sub-angular clasts, coarse matrix, jigsaw fit) it shows a hybrid facies characterized by debris avalanche blocks embedded in a finer, homogenous and partially cemented matrix, a texture more characteristic of debris flow deposits. The Tonila debris avalanche is directly overlain by a 7-m thick hydromagmatic pyroclastic succession. Massive debris flow deposits, often more than 10m thick and containing large amounts of tree trunk logs, represent the top unit in the succession. Fluvial deposits also occur throughout all successions; these represent periods of highly localized stream reworking. All these lines of evidence point to the presence of water in the edifice prior to the Tonila failure, suggesting it may have been a weakening factor. The Tonila failure appears to represent an anomalous event related to the particular climatic conditions at the time of the collapse. The presence of extensive water at the onset of deglaciation modified the mobility of the debris avalanche, and led to the formation of a thick sequence of debris flows. The possibility that such a combination of events can occur, and that their probability is likely to increase during the rainy season, should be taken into consideration when evaluating hazards associated with future collapses at Colima volcano. © 2011 Elsevier B.V.

Volcanic ash causes multiple hazards. One hazard of increasing importance is the threat posed to civil aviation, which occurs over proximal to long-range distances. Ash fallout disrupts airport operations, while the presence of airborne ash at low altitudes near airports affects visibility and the safety of landing and take-off operations. Low concentrations of ash at airplane cruise levels are sufficient to force re-routing of in-flight aircrafts. Volcanic fallout deposits spanning large distances have been recognized from the Somma-Vesuvius volcano for several Holocene explosive eruptions. Here we develop hazard and isochron maps for distal ash fallout from the Somma-Vesuvius, as well as hazard maps for critical ash concentrations at relevant flight levels. Maps are computed by coupling a meteorological model with a fully numeric tephra dispersal model that can account for ash aggregation processes, which are relevant to the dispersion dynamics of fine ash. The simulations were carried out using supercomputing facilities, spanning on entire meteorological year that is statistically representative of the local meteorology during the last few decades. Seasonal influences are also analyzed. The eruptive scenario is based on a Subplinian I-type eruption, which is within the range of the maximum expected event for this volcano. Results allow us to quantify the impact that an event of this magnitude and intensity would have on the main airports and aerial corridors of the Central Mediterranean Area. © 2010 Springer-Verlag.

Mele D.,CIRISIVU | Sulpizio R.,CIRISIVU | Dellino P.,CIRISIVU | la Volpe L.,CIRISIVU
Bulletin of Volcanology | Year: 2011

New volcanological studies allow reconstruction of the eruption dynamics of the Pomici di Mercato eruption (ca 8,900 cal. yr B. P.) of Somma-Vesuvius. Three main Eruptive Phases are distinguished based on two distinct erosion surfaces that interrupt stratigraphic continuity of the deposits, indicating that time breaks occurred during the eruption. Absence of reworked volcaniclastic deposits on top of the erosion surfaces suggests that quiescent periods between eruptive phases were short perhaps lasting only days to weeks. Each of the Eruptive Phases was characterised by deposition of alternating fall and pyroclastic density current (PDC) deposits. The fallout deposits blanketed a wide area toward the east, while the more restricted PDC deposits inundated the volcano slopes. Eruptive dynamics were driven by brittle magmatic fragmentation of a phonolitic magma, which, because of its mechanical fragility, produced a significant amount of fine ash. External water did not significantly contribute either to fragmentation dynamics or to mechanical energy release during the eruption. Column heights were between 18 and 22 km, corresponding to mass discharge rates between 1.4 and 6 × 107 kg s-1. The estimated on land volume of fall deposits ranges from a minimum of 2.3 km3 to a maximum of 7.4 km3. Calculation of physical parameters of the dilute pyroclastic density currents indicates speeds of a few tens of m s-1 and densities of a few kg m-3 (average of the lowermost 10 m of the currents), resulting in dynamic pressures lower than 3 kPa. These data suggest that the potential impact of pyroclastic density currents of the Pomici di Mercato eruption was smaller than those of other Plinian and sub-Plinian eruptions of Somma-Vesuvius, especially those of 1631 AD and 472 AD (4-14 kPa), which represent reference values for the Vesuvian emergency plan. The pulsating and long-lasting behaviour of the Pomici di Mercato eruption is unique in the history of large explosive eruptions of Somma-Vesuvius. We suggest an eruptive scheme in which discrete magma batches rose from the magma chamber through a network of fractures. The injection and rise of the different magma batches was controlled by the interplay between magma chamber overpressure and local stress. The intermittent discharge of magma during a large explosive eruption is unusual for Somma-Vesuvius, as well as for other volcanoes worldwide, and yields new insights for improving our knowledge of the dynamics of explosive eruptions. © 2010 Springer-Verlag.

Sulpizio R.,CIRISIVU | Capra L.,National Autonomous University of Mexico | Sarocchi D.,Institute Geologia | Saucedo R.,Institute Geologia | And 2 more authors.
Journal of Volcanology and Geothermal Research | Year: 2010

Maps of areas potentially affected by block-and-ash flows and associated ash clouds are here presented for the Volcán de Colima. TITAN2D 2.0.1 code has been used to simulate block-and-ash flows using as an input volume that of the actual summit dome (assessed at 2×106m3), while the Energy Cone model has been used to delimit the possible inundated area from associated ash clouds. Both Merapi- and Soufriere-type block-and-ash flows were generated using different basal friction angles and maintaining fixed the volume and the internal friction angle. The setting of the input parameters takes into account some flow characteristics, such as the stepwise aggradation of different pulses that piled up to form the total thickness of the block-and-ash flow deposits. The outputs of the computational routines are reported as two maps describing the total thickness of the final deposits. They predict that thick deposits will engulf the ravines descending from the main cone to the west, south and southeast, with expected maximum runouts between 4.5 and 7km. The associated ash clouds have slightly longer runouts, and the model predicts they will inundate some higher grounds that are not affected by the concentrate underflows. The presented maps represent useful tools for managing the current block-and-ash flow hazard at Volcán de Colima. © 2010 Elsevier B.V.

Sulpizio R.,CIRISIVU | Bonasia R.,CIRISIVU | Bonasia R.,Italian National Institute of Geophysics and Volcanology | Dellino P.,CIRISIVU | And 3 more authors.
Bulletin of Volcanology | Year: 2010

Pyroclastic density currents (PDCs) generated during the Plinian eruption of the Pomici di Avellino (PdA) of Somma-Vesuvius were investigated through field and laboratory studies, which allowed the detailed reconstruction of their eruptive and transportation dynamics and the calculation of key physical parameters of the currents. PDCs were generated during all the three phases that characterised the eruption, with eruptive dynamics driven by both magmatic and phreatomagmatic fragmentation. Flows generated during phases 1 and 2 (EU1 and EU3pf, magmatic fragmentation) have small dispersal areas and affected only part of the volcano slopes. Lithofacies analysis demonstrates that the flow-boundary zones were dominated by granular-flow regimes, which sometimes show transitions to traction regimes. PDCs generated during eruptive phase 3 (EU5, phreatomagmatic fragmentation) were the most voluminous and widespread in the whole of Somma-Vesuvius' eruptive history, and affected a wide area around the volcano with deposit thicknesses of a few centimetres up to more than 25 km from source. Lithofacies analysis shows that the flow-boundary zones of EU5 PDCs were dominated by granular flows and traction regimes. Deposits of EU5 PDC show strong lithofacies variation northwards, from proximally thick, massive to stratified beds towards dominantly alternating beds of coarse and fine ash in distal reaches. The EU5 lithofacies also show strong lateral variability in proximal areas, passing from the western and northern to the eastern and southern volcano slopes, where the deposits are stacked beds of massive, accretionary lapilli-bearing fine ash. The sedimentological model developed for the PDCs of the PdA eruption explains these strong lithofacies variations in the light of the volcano's morphology at the time of the eruption. In particular, the EU5 PDCs survived to pass over the break in slope between the volcano sides and the surrounding volcaniclastic apron-alluvial plain, with development of new flows from the previously suspended load. Pulses were developed within individual currents, leading to stepwise deposition on both the volcano slopes and the surrounding volcaniclastic apron and alluvial plain. Physical parameters including velocity, density and concentration profile with height were calculated for a flow of the phreatomagmatic phase of the eruption by applying a sedimentological method, and the values of the dynamic pressure were derived. Some hazard considerations are summarised on the assumption that, although not very probable, similar PDCs could develop during future eruptions of Somma-Vesuvius. © 2010 Springer-Verlag.

Wagner B.,University of Cologne | Vogel H.,University of Cologne | Zanchetta G.,CNR Institute of Geosciences and Earth Resources | Sulpizio R.,CIRISIVU
Biogeosciences | Year: 2010

Lakes Prespa and Ohrid, in the Balkan region, are considered to be amongst the oldest lakes in Europe. Both lakes are hydraulically connected via karst aquifers. From Lake Ohrid, several sediment cores up to 15 m long have been studied over the last few years. Here, we document the first long sediment record from nearby Lake Prespa to clarify the influence of Lake Prespa on Lake Ohrid and the environmental history of the region. Radiocarbon dating and dated tephra layers provide robust age control and indicate that the 10.5 m long sediment record from Lake Prespa reaches back to 48 ka. Glacial sedimentation is characterized by low organic matter content and absence of carbonates in the sediments, which indicate oligotrophic conditions in both lakes. Holocene sedimentation is characterized by particularly high carbonate content in Lake Ohrid and by particularly high organic matter content in Lake Prespa, which indicates a shift towards more mesotrophic conditions in the latter. Long-term environmental change and short-term events, such as related to the Heinrich events during the Pleistocene or the 8.2 ka cooling event during the Holocene, are well recorded in both lakes, but are only evident in certain proxies. The comparison of the sediment cores from both lakes indicates that environmental change affects particularly the trophic state of Lake Prespa due to its lower volume and water depth. © Author(s) 2010.

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