S U M M A R YWe discuss theoretical and computational method on plate-driven mantle flow beneath midocean ridges. We consider a steady-state flow induced by motion of overlying rigid plates in an incompressible viscous mantle beneath a generic ridge-transform-ridge plate boundary. No assumption of orthogonal and symmetric spreading at ridge axis is made. Analytical solutions for viscosity flow in a half-space and in a layered viscosity mantle beneath an infinitesimal thickness lithosphere and beneath plates that thicken with increasing age, are presented. Numerical calculations were carried out using a standard fast Fourier transform algorithm. The difficulty of using standard Fourier methods to predict accurately the mantle flow field in the proximity of the plate boundaries is overcome by applying the Gegenbauer reconstruction post-processing technique to the Fourier pseudo-spectral solutions. Finally, we present some examples of flow computations. We consider, for both models, two different ridge-transformridge geometries consisting of 100 and 1000 km offsets of two ridge segments spreading at 15 mm/yr half rate. We found a significant difference in the flow structure between the two flow models close to ridge axis and ridge-transform intersections. The proposed model and methods are useful for fast mantle flow calculations to investigate melting processes beneath spreading centres, and to predict the relationship between mantle temperature, crustal thickness and geochemistry of the oceanic crust.

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The Nirano Salse, known since the Roman Times, are one of the most beautiful and scenic mud volcanoes areas of Italy with thousands of visitors every year. In this work, we apply novel (for the context) hydrogeological techniques to characterize mud levels in the Salse by means of GPS-RTK positioning and continuous level logging within mud conduits. This is important to quantify the gas–liquid ratio in the conduits and evaluate the potential for dangerous abrupt mud eruptions. The results presented suggest that different mud levels in mud volcanoes clusters are due to the different gas–liquid ratio in the conduits and not necessarily exclude interconnection at depth, a hypothesis, on the other hand, that seems strengthened by mud level time series correlations. The presence of shallow aquifers at a depth of 5 to 30 m is also supported by our field data and allows us to delineate the boundaries of the shallow mud reservoir—pipes system and its overall shape. The shallow aquifers may provide a temporary storage for the ascending gas and when fluid pressure in these aquifers exceeds the tensional strength of the sedimentary rock, leakage of fluids to the surface would occur. In this case, if the gas–liquid ratio is high, mud volcanoes develop into tall gryphons and tend to have a discontinuous activity with sudden eruptions of mud after long periods of quiescence. This, together with the knowledge of shallow conduits localization has an important implication for site safety in proximity to the mud volcanoes. Our inferences based on mud level relationships to mud extrusion dynamics can be applied to lower risk in other mud volcanoes areas of the world with high geo-tourist visits, such as those of Trinidad, Azerbaijan, and Colombia.

On November 1, 1755, the city of Lisbon was completely devastated by the combined effect of a tremendous earthquake, tsunami waves, and fire. The 1755 Lisbon earthquake was the most destructive cataclysm recorded in western Europe since the Roman Republic, with an estimated earthquake magnitude Mw ∼8.5 [Martins and Mendes Victor, 1990] and estimated tsunami magnitude of Mt= Mw= 8.5. The earthquake was felt as far away as Great Britain and Finland. The tsunami hit many coastal cities along southwest Iberia and North Africa, causing heavy destruction in Tanger and Casablanca.

The present research investigates the possibility to create a silt-waste reinforced composite through a NaOH-activated, metakaolin-based geopolymerization process. In this regard, we used thermal exo–endo analysis, X-ray diffraction (XRD), and oedometric mechanical tests to characterize the produced composites. In our experimental conditions, the tested material mixtures presented exothermic peaks with maximum temperatures of about 100 °C during the studied geopolymerization process. In general, the XRD analyses showed the formation of amorphous components and new mineral phases of hydrated sodalite, natrite, thermonatrite and trona. From oedometric tests, we observed a different behavior of vertical deformation related to pressure (at RT) for the various produced composites. The present work indicated that the proposed geopolymerization process to recycle silt-waste produced composite materials with various and extended mineralogy and chemical–physical properties, largely depending on both the precursors and the specific alkaline-activating solution. Thermal analysis, XRD, and oedometric mechanical tests proved to be fundamental to characterize and understand the behavior of the newly formed composite material.