Search results for "METEOROLOGY"

Could tsunami risk be underestimated using core‐based reconstructions? Lessons from ground penetrating radar

2017

Where should we take cores for palaeotsunami research? It is generally considered that local depressions with low energy environments such as wetlands are one of the best places. However, it is also recognized that the presence or absence of palaeotsunami deposits (and their relative thickness) is highly dependent upon subsoil microtopography. In the beach ridge system of Ishinomaki Plain, Japan, several palaeotsunami deposits linked to past Japan Trench earthquakes have been reported. However, the number of palaeotsunami deposits reported at individual sites varies considerably. This study used ground penetrating radar (GPR) combined with geological evidence to better understand the relati…

Hydraulic properties of fault zones in porous carbonates, examples from central and southern Italy

2016

We present the results of in situ permeability measurements performed, using a portable field permeameter, on normal and strike-slip fault zones that crosscut high-porosity carbonate grainstones. The measurement sites expose in the Cretaceous Orfento Formation of the Majella Mountain (Abruzzo, Italy), and the Lower Pleistocene deposits of the Favignana Island (Sicily, Italy). Nine small-displacement, compactive shear banding-based fault zones have been tested in the field. The fault offset ranges between 10 and 200 centimeters. The acquired permeability data indicate a two orders of magnitude decrease of porosity and permeability from the host rock to the cataclastic fault cores. A clear de…

Late Jurassic globetrotters compared: A closer look at large and giant theropod tracks of North Africa and Europe

2019

Abstract Late Jurassic theropod tracks are very common both in North Africa and Europe. Two recently described ichnotaxa Megalosauripus transjuranicus and Jurabrontes curtedulensis from the Kimmeridgian of Switzerland show the coexistence of two apex predators in the same palaeoenvironment. Similar tracks can be found in tracksites from the Iberian Peninsula and from Morocco. Here, we further explore the similarities among the Swiss ichnotaxa and the other tracks from Germany (Kimmeridgian), Spain (Tithonian-Berriasian), Portugal (Oxfordian-Tithonian) and Morocco (Kimmeridgian) through novel three-dimensional data comparisons. Specimens were grouped in two morphotypes: 1) large and gracile …

Strong intracontinental lithospheric deformation in South China: Implications from seismic observations and geodynamic modeling

2014

Abstract Classical plate tectonics theory predicts concentrated deformation at plate boundaries and weak deformation within plates. Yet, the existence of intracontinental orogens shows that highly deformed regions can occur within continental plates, which is geodynamically incompletely understood. Shear wave splitting measurements in South China show belt-parallel (i.e. NE–SW) fast directions beneath the Wulingshan-Xuefengshan Belts, while no dominant fast direction is found in the cratonic Sichuan Basin. Tomographic studies in the mantle in the same area show that the thickness of lithosphere beneath the intracontinental orogen is larger than that beneath the cratonic Sichuan Basin. In or…

El Niño in the Eocene greenhouse recorded by fossil bivalves and wood from Antarctica

2011

[1] Quasi-periodic variation in sea-surface temperature, precipitation, and sea-level pressure in the equatorial Pacific known as the El Nino – Southern Oscillation (ENSO) is an important mode of interannual variability in global climate. A collapse of the tropical Pacific onto a state resembling a so-called ‘permanent El Nino’, with a preferentially warmed eastern equatorial Pacific, flatter thermocline, and reduced interannual variability, in a warmer world is predicted by prevailing ENSO theory. If correct, future warming will be accompanied by a shift toward persistent conditions resembling El Nino years today, with major implications for global hydrological cycles and consequent impact…

Sulphur-gas concentrations in volcanic and geothermal areas in Italy and Greece: Characterising potential human exposures and risks

2013

Abstract Passive samplers were used to measure the atmospheric concentrations of SO 2 naturally emitted at three volcanoes in Italy (Etna, Vulcano and Stromboli) and of H 2 S naturally emitted at three volcanic/geothermal areas in Greece (Milos, Santorini and Nisyros). The measured concentrations and dispersion patterns varied with the strength of the source (open conduits or fumaroles), the meteorological conditions and the area topography. At Etna, Vulcano and Stromboli, SO 2 concentrations reach values that are dangerous to people affected by bronchial asthma or lung diseases (> 1000 μg m − 3 ). H 2 S values measured at Nisyros also exceed the limit considered safe for the same group of …

2021

Abstract The spaceborne detection of volcanic ash clouds at infrared wavelengths helps to avoid regions with enhanced volcanic ash concentrations that pose a threat to aviation. Current volcanic ash data retrievals require detailed information on microphysical properties and the refractive index of volcanic ash, which are highly variable. Uncertainties in the latter currently limit the quality of volcanic ash nowcasts. Here, we introduce a novel method to calculate the complex refractive indices of volcanic ashes at wavelengths from 5 to 15 μm from measurements of their individual components based on generic petrological ash compositions. Thereby the refractive indices for volcanic glasses …

Chlorine isotope composition of volcanic rocks and gases at Stromboli volcano (Aeolian Islands, Italy): Inferences on magmatic degassing prior to 201…

2017

Abstract Among the magmatic volatiles, chlorine (Cl) is degassed at shallow depths offering the opportunity to investigate the behavior of magmatic degassing close to the surface, and the possible occurrence of chemical and isotopic fractionation related to gas/melt partitioning. However, it is still unclear if the isotopic composition of Cl (δ 37 Cl) can be used as a proxy of magmatic degassing. In this work, we investigate the concentrations of chlorine and sulfur, and the Cl isotope composition of rocks and plume gases collected at Stromboli volcano, Aeolian Islands, Italy. This volcano was chosen because it is characterized by persistent eruptive activity (i.e., Strombolian explosions) …

Morphological characterization of calanchi (badland) hillslope connectivity

2017

Calanchi, a type of Italian badlands created by a combination of water erosion processes and local geomorphological and tectonic controls, is a striking example of long-term landscape evolution. In small temporal/spatial scales, the calanchi exhibit many of the geomorphic processes and landforms that may be observed in fluvial landscapes, hence they may be considered as micro-basins where geomorphic dynamics and landscape features can be related. The goal of this research is testing the use of simple morphometric variables for assessing sediment connectivity of calanchi landforms. In order to detect the morphological characteristics controlling the landscape connectivity of calanchi basins,…

Deformation and fluid flow in the Huab Basin and Etendeka Plateau, NW Namibia

2016

Abstract The Lower Cretaceous Twyfelfontein sandstone formation in the Huab Basin in NW Namibia shows the effects of volcanic activity on a potential reservoir rock. The formation was covered by the Parana-Etendeka Large Igneous Province shortly before or during the onset of South-Atlantic rifting. Deformation bands found in the sandstone trend mostly parallel to the continental passive margin and must have formed during the extrusion of the overlying volcanic rocks, indicating that their formation is related to South-Atlantic rifting. 2D-image porosity analysis of deformation bands reveals significant porosity reduction from host rock to band of up to 70%. Cementation of the sandstone, lin…