Detecting short-term evolution of Etnean scoria cones: a LIDAR-based approach

The 2001 and 2002–2003 flank eruptions on Mount Etna (Italy) were characterized by intense explosive activity which led to the formation of two large monogenetic scoria cones (one from each eruption) on the upper southern flank of the volcano. Continuous monitoring of Etna, especially during flank eruptions, has provided detailed information on the growth of these cones. They differ in genesis, shape, and size. A set of high resolution (1 m) digital elevation models (DEMs) derived from light detection and ranging (LIDAR) data collected during four different surveys (2004, 2005, 2006, and 2007) has been used to map morphology and to extract the morphometric parameters of the scoria cones. By comparing LIDAR-derived DEMs with a pre-eruption (1998) 10 m DEM, the volume of the two scoria cones was calculated for the first time. Comparison of the LIDAR-derived DEMs revealed in unprecedented detail morphological changes during scoria cone degradation. In particular, the morphologically more exposed and structurally weaker 2002–2003 cone was eroded rapidly during the first few years after its emplacement mainly due to gravitational instability of slopes and wind erosion.     

Thermal expansion-contraction and slope instability of a fumarole field inferred from geodetic measurements at Vulcano

Between 1987 and 1993, fumarole temperatures at the Fossa crater of Vulcano (Italy) were characterized by the highest values since the 1920’s, increasing from about 300°C in 1987 to 690°C in May 1993, before decreasing to 400°C by 1996–1997. During 1990, Vulcano’s Electronic Distance Measurement (EDM) network was expanded to provide more detailed coverage of the northern sector of the Fossa crater and, in particular, to monitor the movement of the northern flank the Fossa cone. Measurements, carried out between 1990 and 1994, showed shortening by about 6 to 7 cm along baselines measured to a small section of the northern rim. Over the following four years these baselines showed a slow extension by about 3 cm, to gradually recover part of the previous deformation. We believe that the shortening and lengthening of the EDM baselines was respectively due to the increasing and decreasing temperature of the rock body lying close to the deforming area. This caused thermal expansion, followed by contraction. The positive movement of the rim was not completely matched by a negative recovery, suggesting that a non-recoverable sliding movement was also responsible for some of the shortening of the baselines. We verified our hypothesis by calculating the expected dilatation of a rock body, as a function of the volume of rock heated and its thermal expansion coefficient, and compared the expected deformation to that observed. The geodetic investigation showed that the unstable portion affects a small length of the rim (about 100 m long) and involves a volume of about 0.8 × 10⁶ m³. However, this zone lies directly above a particularly unstable portion of the flank, as well as the main village and port on the island.     

Seismic performance of non-structural components and contents in buildings: an overview of NZ research

This paper summarizes the research on non-structural elements and building contents being conducted at University of Canterbury in New Zealand. Since the 2010-2011 series of Canterbury earthquakes, in which damage to non-structural components and contents contributed heavily to downtime and overall financial loss, attention to seismic performance and design of non-structural components and contents in buildings has increased exponentially in NZ. This has resulted in an increased allocation of resources to research leading to development of more resilient non-structural systems in buildings that would incur substantially less damage and cause little downtime during earthquakes. In the last few years, NZ researchers have made important developments in understanding and improving the seismic performance of secondary building elements such as partitions, facades, ceilings and contents.     

The role of structural inheritance in continental break-up and exhumation of Alpine Tethyan mantle(Canavese Zone,Western Alps)

The Canavese Zone(CZ)in the Western Alps represents the remnant of the distal passive margin of the Adria microplate,which was stretched and thinned during the Jurassic opening of the Alpine Tethys.Through detailed geological mapping,stratigraphic and structural analyses,we document that the continental break-up of Pangea and tectonic dismemberment of the Adria distal margin,up to mantle rocks exhumation and oceanization,did not simply result from the syn-rift Jurassic extension but was strongly favored by older structu ral inheritances(the Proto-Canavese Shear Zone),which controlled earlier lithospheric weakness.Our findings allowed to redefine in detail(i)the tectono-stratigraphic setting of the Variscan metamorphic basement and the Late Carbonife rous to Early Cretaceous CZ succession,(ii)the role played by inherited Late Carboniferous to Early Triassic structures and(iii)the significance of the CZ in the geodynamic evolution of the Alpine Tethys.The large amount of extensional displacement and crustal thinning occurred during different pulses of Late Carbonife rous-Early Triassic strike-slip tectonics is wellconsistent with the role played by long-lived regional-scale wrench faults(e.g.,the East-Variscan Shear Zone),suggesting a re-discussion of models of mantle exhumation driven by low-angle detachment faults as unique efficient mechanism in stretching and thinning continental crust.     

Role of vegetation in shaping Early Pennsylvanian braided rivers: Architecture of the Boss Point Formation,Atlantic Canada

Vegetation is a major driver of fluvial dynamics in modern rivers, but few facies models incorporate its influence. This article partially fills that gap by documenting the stratigraphy, architecture and palaeobotany of the Lower Pennsylvanian Boss Point Formation of Atlantic Canada, which contains some of the Earth's earliest accumulations of large woody debris. Braided‐fluvial systems occupied channel belts of varied scale within valleys several tens of metres deep and more than 12 km wide, and their deposits predominantly consist of sandy and gravelly bedforms with subordinate accretionary macroforms, high flow‐strength sand sheets and rippled abandonment facies. Discrete accumulations of clastic detritus and woody debris are up to 6 m thick and constitute at least 18% of the in‐channel deposits; they represent lags at the base of large and small channels, fills of minor channels and sandy macroforms that developed in central positions in the upper parts of channel fills. Sandstones with roots and other remnants of in situ vegetation demonstrate that vegetated islands were present, and the abundance of discrete channel fills suggests that the formation represents an anabranching, island‐braided sandbed river, the earliest example documented to date. Although some sphenopsid and lycopsid remains are present, most woody fragments are derived from cordaitalean trees, and the evolution of this group late in the Mississippian is inferred to have exerted a significant influence on fluvial morphodynamic patterns. The formation records a landscape in which active channel belts alternated with well‐drained floodplains colonized by dense, mature forests and local patches of pioneering, disturbance‐tolerant vegetation. Lakes and poorly drained floodplains dominated by carbonate and organic deposition, respectively, were also present. A large supply of woody debris triggered channel blockage and avulsion, and active channel margins and islands within the channel belts were initially colonized by pioneer vegetation and subsequently stabilized by large trees. A similar alternation of stable and unstable conditions is observed in modern braided rivers actively influenced by vegetation.     

Central Mediterranean tephrochronology between 313 and 366 ka: New insights from the Fucino palaeolake sediment succession

Thirty-two tephra layers were identified in the time-interval 313–366 ka (Marine Isotope Stages 9–10) of the Quaternary lacustrine succession of the Fucino Basin, central Italy. Twenty-seven of these tephra layers yielded suitable geochemical material to explore their volcanic origins. Investigations also included the acquisition of geochemical data of some relevant, chronologically compatible proximal units from Italian volcanoes. The record contains tephra from some well-known eruptions and eruptive sequences of Roman and Roccamonfina volcanoes, such as the Magliano Romano Plinian Fall, the Orvieto–Bagnoregio Ignimbrite, the Lower White Trachytic Tuff and the Brown Leucitic Tuff. In addition, the record documents eruptions currently undescribed in proximal (i.e. near-vent) sections, suggesting a more complex history of the major eruptions of the Colli Albani, Sabatini, Vulsini and Roccamonfina volcanoes between 313 and 366 ka. Six of the investigated tephra layers were directly dated by single-crystal-fusion ⁴⁰Ar/³⁹Ar dating, providing the basis for a Bayesian age–depth model and a reassessment of the chronologies for both already known and dated eruptive units and for so far undated eruptions. The results provide a significant contribution for improving knowledge on the peri-Tyrrhenian explosive activity as well as for extending the Mediterranean tephrostratigraphical framework, which was previously based on limited proximal and distal archives for that time interval.     

The 1906 eruption of Vesuvius: from magmatic to phreatomagmatic activity through the flashing of a shallow depth hydrothermal system

The April 1906 eruption of Vesuvius is the type-example of the final eruptions that close the short cycles of semi-persistent activity that characterized the volcano in the 1631–1944 period. The eruption had a marked explosive character that accompanied the emission of lava from several vents on the southern slopes of the volcano. The observed sequence of events was characterized by repeated fluctuations of the magma level within the conduit, by large lava fountains, by conduit partial collapses, and by the final explosive decapitation of the summit cone. Contemporary chronicles, although frequently contradictory, allow reconstruction of the eruption, which can be divided into four main phases: (1) lateral lava effusions; (2) lava fountains; (3) gas-pyroclasts column; (4) low dense clouds. Pyroclastic deposits of the Monte Somma ridge and northeastern slope can be related to observed and described events and mainly refer to the 2nd and 3rd phases. The increase in the degree of fragmentation of the juvenile component together with the marked increase of the lithic component and morphologic evidence emphasize the repeated occurrence of magmawater interaction. This was most spectacular in the 3rd phase of the eruption in which, after the decapitation of the cone, a high gas-pyroclasts eruption column was formed. Because of the nature of the lithic fragments (mainly hydrothermally altered and metasomatic rocks), the huge amount of steam, and the high lithic/juvenile ratio, it is unlikely that the largest part of the energy in play was related to the contact between magma and cold phreatic water. We suggest that most of the steam involved in this phase of the eruption came from flashing of the hydrothermal system connected to the very shallow feeding system of the volcano and formed as a consequence of repeated subsurface intrusions between 1872 and 1906. Juvenile products were ejected through the eruption, and represent (at least) two different magma bodies: the first (older) was erupted during the initial phase of the eruption and was exhausted at the beginning of the lava fountains phase, when fresh magma was involved in the eruption.     

A novel insight into vertical ground motion modelling in earthquake engineering

Recent observations of failure and damage of buildings and structures under seismic action has led to an increasing interest for an in-depth analysis of the vertical component of site ground motion. In particular, when dealing with saturated soils, the current engineering practice does not usually go beyond the simplified $u$–$p$ formulation of the Biot's equations describing the coupled hydro-mechanical behaviour, thus neglecting some terms of fluid inertial forces, despite the presence of more refined formulations, for example, the $u$–$U$ formulation. Therefore, a theoretical and numerical validation of the $u$–$p$ formulation as compared with the $u$–$U$ formulation is proposed in this work, where the numerical simulations are compared with the analytical solution for the $u$–$p$ formulation, which is also derived and illustrated in this text. The comparison between the two formulations and the analytical solution is provided for different levels of permeability and dynamic actions, which are representative of a wide scenario of site ground properties and seismic hazard in the vertical direction. In particular, the soil response is analysed in terms of acceleration and pore pressure time history, frequency content, acceleration response spectrum, and amplification ratio of acceleration. This study extends the discussion of the limits of applicability of the $u$–$p$ formulation with respect to the rigorous solution of Biot's equations (obtained here with $u$–$U$ formulation) to the context of a complex dynamic regime provided by the vertical components of real earthquake records, and paves the way for further investigations.