Maria Teresa Pareschi

Petrology of volcanic products younger than 42 ka on the Lipari-Vulcano complex (Aeolian Islands, Italy): an example of volcanism controlled by tectonics

Abstract Over the last 42 ka, volcanic activity at Lipari Island (Aeolian Arc, Italy) produced lava domes, flows and pyroclastic deposits with rhyolitic composition, showing in many cases evidence of magma mixing such as latitic enclaves and banding. In this same period, on nearby Vulcano Island, similar rhyolitic lava domes, pyroclastic products and lava flows, ranging in composition from shoshonite to rhyolite, were erupted. As a whole, the post-42 ka products of Lipari and Vulcano show geochemical variations with time, which are well correlated between the two islands and may correspond to a modification of the primary magmas. The rhyolitic products are similar to each other in their major elements composition, but differ in their trace element abundances (e.g. La ranging from 40 to 78 ppm for SiO2 close to 75 wt%). Their isotopic composition is variable, too. The 87Sr/86Sr (0.704723–0.705992) and 143Nd/144Nd (0.512575–0.512526) ranges partially overlap those of the more mafic products (latites), having 87Sr/86Sr from 0.7044 to 0.7047 and 143Nd/144Nd from 0.512672 to 0.512615. 206Pb/204Pb is 19.390–19.450 in latites and 19.350–19.380 in rhyolites. Crystal fractionation and crustal assimilation processes of andesitic to latitic melts, showing an increasing content in incompatible elements in time, may explain the genesis of the different rhyolitic magmas. The rocks of the local crustal basement assimilated may correspond to lithotypes present in the Calabrian Arc. Mixing and mingling processes between latitic and rhyolitic magmas that are not genetically related occur during most of the eruptions. The alignment of vents related to the volcanic activity of the last 40 ka corresponds to the NNW–SSE Tindari–Letojanni strike-slip fault and to the correlated N–S extensional fault system. The mafic magmas erupted along these different directions display evidence of an evolution at different PH2O conditions. This suggests that the Tindari–Letojanni fault played a relevant role in the ascent, storage and diversification of magmas during the recent volcanic activity.

The changing face of Mount Etna's summit area documented with Lidar technology

1986–2007 period amounts to 112 ± 12 10 6 m 3 ,a t a mean annual rate of 5.3 10 6 m 3 . The comparison of the various surveys furthermore emphasizes the levels of accuracy and resolution of the different techniques applied. The Lidar technology used in 2007 allows production of high-precision maps in near-real-time, facilitating work concerning environmental hazards such as numerical simulations of, e.g., lava flows. Citation: Neri, M., F. Mazzarini, S. Tarquini, M. Bisson, I. Isola, B. Behncke, and M. T. Pareschi (2008), The changing face of Mount Etna’s summit area documented with Lidar technology, Geophys. Res. Lett., 35, L09305, doi:10.1029/2008GL033740.

Evolution of an active lava flow field using a multitemporal LIDAR acquisition

This work was partially funded by the Italian 930 Dipartimento della Protezione Civile in the frame of the 2007–2009 Agree- 931 ment with Istituto Nazionale di Geofisica e Vulcanologia–INGV. A.F. 932 benefited from the MIUR‐FIRB project “Piattaforma di ricerca multi‐disci- 933 plinare su terremoti e vulcani (AIRPLANE)” n. RBPR05B2ZJ. S.T. 934 benefited from the project FIRB “Sviluppo di nuove tecnologie per la prote- 935 zione e difesa del territorio dai rischi naturali (FUMO)” funded by the Italian 936 Ministero dell’Istruzione, dell’Universita e della Ricerca.

The dem of mt. etna: geomorphological and structural implications

AbstractA Digital Elevation Model (DEM) of Mt. Etna is presented; it has altimetric and planimetric resolution of 1 m and 5 m, respectively, and covers an area of about 120 km . This 3-D view of Mt. Etna allowed both recognition and location of the main morphostructural and volcano-tectonic features of the volcano. A slope map has been generated from the DEM; on the basis of slope distributions and surface textures, five acclivity domains have been recognized. The largest domain, south of the summit craters, reflects the occurrence of old plateau lavas, distinct from central volcanoes which built the present Etnean volcanic system. Interaction between the central volcanoes, with their summit calderas and failed slopes, produced the other recognised domains. Furthermore, newly identified relevant morphostructural lines are discussed.

Lava flow hazard at Nyiragongo volcano, D.R.C. 1. Model calibration and hazard mapping

The 2002 eruption of Nyiragongo volcano constitutes the most outstanding case ever of lava flow in a big town. It also represents one of the very rare cases of direct casualties from lava flows, which had high velocities of up to tens of kilometer per hour. As in the 1977 eruption, which is the only other eccentric eruption of the volcano in more than 100 years, lava flows were emitted from several vents along a N–S system of fractures extending for more than 10 km, from which they propagated mostly towards Lake Kivu and Goma, a town of about 500,000 inhabitants. We assessed the lava flow hazard on the entire volcano and in the towns of Goma (D.R.C.) and Gisenyi (Rwanda) through numerical simulations of probable lava flow paths. Lava flow paths are computed based on the steepest descent principle, modified by stochastically perturbing the topography to take into account the capability of lava flows to override topographic obstacles, fill topographic depressions, and spread over the topography. Code calibration and the definition of the expected lava flow length and vent opening probability distributions were done based on the 1977 and 2002 eruptions. The final lava flow hazard map shows that the eastern sector of Goma devastated in 2002 represents the area of highest hazard on the flanks of the volcano. The second highest hazard sector in Goma is the area of propagation of the western lava flow in 2002. The town of Gisenyi is subject to moderate to high hazard due to its proximity to the alignment of fractures active in 1977 and 2002. In a companion paper (Chirico et al., Bull Volcanol, in this issue, 2008) we use numerical simulations to investigate the possibility of reducing lava flow hazard through the construction of protective barriers, and formulate a proposal for the future development of the town of Goma.

Large submarine landslides offshore Mt. Etna

[1] High resolution seismic data, we collected in the Ionian sea, reveal large submarine landslide deposits offshore from Mt. Etna (Italy), spatially consistent with the eastern flank collapse of this volcano. A large debris-avalanche deposit, we relate to the Valle del Bove scar, displays long offshore run-outs (till 20 km) and a volume of a few tens of cubic kilometres (16-21 km 3 ). Other landslide deposits are also imaged, in particular a striking unique record of the relative timing of multiple submarine large slump events.

Role of local wind circulation in plume monitoring at Mt. Etna volcano (Sicily): Insights from a mesoscale numerical model

[1] Mesoscale simulations at Mt. Etna volcano (Sicily, Italy), validated by measurements, highlight the fundamental role played by the local wind field in the dispersion of a gaseous volcanic plume. During the night, downslope surface winds (over-hill flow and katabatic breezes) force the plume to follow the steep morphology, whereas during the day very frequent NNW synoptic winds crash into the cone and are contrasted by SE strong sea breezes and anabatic winds, with the consequent formation of convective ascendant currents. The local mesoscale wind reconstruction can provide useful improvements in gaseous flux estimation. Far away synoptic wind velocities, often used in these flux evaluations, might be inadequate. We propose a 3D numerical mesoscale wind reconstruction to evaluate plume dynamics (and from it plume flux and potential hazard) throughout all the hours of the day.

Atmospheric dispersion of natural gases at Vulcano island

Abstract Various computational scenarios are analyzed for the evaluation of volcanic CO 2 and SO 2 concentrations in the air over the island of Vulcano (Aeolian Archipelago, north of Sicily). Simulations were done using a 3D mesoscale meteorological model for complex terrain. Local wind depends on differences in land heating and cooling and on island topography. Row model outputs were used by a Lagrangian particle model to simulate dispersion of gases emitted from crater fumaroles. Both models were able to reproduce observations. Simulation of the fumarolic gas dispersion at Vulcano were performed for selected summertime conditions, when more than 10,000 tourists reside in the area of Vulcano Porto. In the inhabited area NW of the cone, the highest concentrations of gases occur near sunrise, due to nocturnal stratification and downslope breezes from the volcano. Present gas emission rates from crater fumaroles do not pose any hazard for humans. An SO 2 output rate two orders of magnitude higher with respect to a considered case of 30 tons per day may pose an hazard.

A LiDAR survey of Stromboli volcano (Italy): Digital elevation model-based geomorphology and intensity analysis

LiDAR (Light Detection and Ranging) is a novel and very useful active remote sensing system which can be used to directly identify geomorphological features as well as the properties of materials on the ground surface. In this work, LiDAR data were applied to the study of the Stromboli volcano in Italy. LiDAR data points, collected during a survey in October 2005, were used to generate a Digital Elevation Model (DEM) and a calibrated intensity map of the ground surface. The DEM, derived maps and topographic cross-sections were used to complete a geomorphological analysis of Stromboli, which led to the identification of four main geomorphological domains linked to major volcanic cycles. Moreover, we investigated and documented the potential of LiDAR intensity data for distinguishing and characterizing different volcanic products, such as fallout deposits, epiclastic sediments and lava flows.

The assessment of volcanic gas hazard by means of numerical models: An example from Vulcano Island (Sicily)

Volcanic activity can inject large quantities of gases and aerosols into the atmosphere both during and between eruptions, creating a health risk for the local population. The paper describes how the volcanic gas concentration in the air can be computed by a flow model simulating the wind field over a digital terrain model of the volcano coupled with a Lagrangian particle model that uses the known (measured) gas emission rates to simulate gas dispersion. The coupling provides hazard maps for a number of meteorological conditions, introduced as boundary and initial conditions to the wind flow model, and permits the estimation of the risk both for actual and increased emission rates. An application for Vulcano Island (Sicily, Italy) is presented. According to the results, the risk at Vulcano is mainly related to: i) SO 2 from the fumaroles of La Fossa cone; ii) the diffuse soil emission of CO 2 from the cone flanks and from the plane around the cone. Although the conclusion is that there is no major hazard for passive degassing at present flux rates, the situation could change in the future. If gaseous emission rates would increase by one order of magnitude above the peak values of a few years ago, the gas concentrations could reach dangerous thresholds for the people of Vulcano Porto village, 1 km NW to the cone.