Search results for "Geophysics"
showing 10 items of 2645 documents
Mount Etna: Geochemical signals of magma ascent and unusually extensive plumbing system
2003
] FiveyearsofgasmonitoringfromselectedsitessuggestthatMtEtna’splumbingsystemismuchmoreextensivethanpreviously reported. It extends at least 40 km SW from thevolcano’s boundary along the NE-SW regional fault, whereit discharges about 200 tons/day of gas, containing heliumwith mantle-type isotopic composition. Synchronousvariations of
Investigation of Surface Geology and Intensity Variability in the Palermo, Italy, Urban Area after the 6 September 2002 Earthquake
2005
For the first time, a high-density macroseismic survey has been carried out in the city of Palermo, Italy, after the 6 September 2002, Mw 5.9 earthquake. The aim was to investigate the spatial relationships and correlations between intensity data and surface geology. A very dense database has been created to store a large amount of macroseismic, stratigraphic, and geotechnical information. A Geographic Information Systems (gis) tool, called City-gis, enables data processing by instruments and research keys devoted to seismic hazard. The results show the feasibility of such procedures, especially for large cities where the surface geology critically influences the ground motion. Our analysis…
Integrated geophysical survey for 3D modelling of a coastal aquifer polluted by seawater
2013
Geophysical surveys are carried out in the coastal area of Petrosino (south-western Sicily) to study the time evolution of seawater contamination of the coastal aquifer, probably increased due to human impact. The overexploitation of the aquifer, due to an intensive agricultural use has affected significantly the natural hydro-geochemical state of the basin. The study is based on a processing and integrated analysis of hydrogeological, geochemical and geophysical data. In particular in the last two years seasonal time-lapse electrical resistivity tomographies (ERT), new TDEM soundings and Multi-Analysis Surface Wave soundings (MASW) have been carried out. The interpretation of the total set…
Geophysical investigations in the Flumendosa River Delta, Sardinia (Italy) — Seismic reflection imaging
2006
A geophysical investigation that included seismic-reflection surveying and time-domain electromagnetics (EM) was carried out in the Flumendosa River Delta plain in southeastern Sardinia, Italy. The objective was to improve knowledge of geologic and hydrogeologic controls on a highly productive aquifer hosted in thick Quaternary deposits and known to be affected by an extensive saltwater intrusion. The seismic reflection survey, whose results are reported here, aimed to image the Paleozoic bedrock topography and to obtain detailed structural and stratigraphic information on the sequence of largely fluvial sediments extending from the surface down to bedrock. The survey consisted of two inli…
Exceptional mobility of an advancing rhyolitic obsidian flow at Cordón Caulle volcano in Chile
2013
The emplacement mechanisms of rhyolitic lava flows are enigmatic and, despite high lava viscosities and low inferred effusion rates, can result in remarkably, laterally extensive (30 km) flow fields. Here we present the first observations of an active, extensive rhyolitic lava flow field from the 2011-2012 eruption at Cordón Caulle, Chile. We combine high-resolution four-dimensional flow front models, created using automated photo reconstruction techniques, with sequential satellite imagery. Late-stage evolution greatly extended the compound lava flow field, with localized extrusion from stalled, ~35 m-thick flow margins creating80 breakout lobes. In January 2013, flow front advance continu…
The emissions of CO2 and other volatiles from the world’s subaerial volcanoes
2019
AbstractVolcanoes are the main pathway to the surface for volatiles that are stored within the Earth. Carbon dioxide (CO2) is of particular interest because of its potential for climate forcing. Understanding the balance of CO2 that is transferred from the Earth’s surface to the Earth’s interior, hinges on accurate quantification of the long-term emissions of volcanic CO2 to the atmosphere. Here we present an updated evaluation of the world’s volcanic CO2 emissions that takes advantage of recent improvements in satellite-based monitoring of sulfur dioxide, the establishment of ground-based networks for semi-continuous CO2-SO2 gas sensing and a new approach to estimate key volcanic gas param…
Tropical Atlantic temperature seasonality at the end of the last interglacial
2015
The end of the last interglacial period, ~118 kyr ago, was characterized by substantial ocean circulation and climate perturbations resulting from instabilities of polar ice sheets. These perturbations are crucial for a better understanding of future climate change. The seasonal temperature changes of the tropical ocean, however, which play an important role in seasonal climate extremes such as hurricanes, floods and droughts at the present day, are not well known for this period that led into the last glacial. Here we present a monthly resolved snapshot of reconstructed sea surface temperature in the tropical North Atlantic Ocean for 117.7±0.8 kyr ago, using coral Sr/Ca and δ18O records. W…
Antarctic erosion history reconstructed by Terre Adélie moraine geochronology
2020
AbstractWe report apatite fission-track and 10Be terrestrial cosmogenic nuclide (TCN) dating of 14 moraine boulders originating from inland Terre Adélie, East Antarctica. These data show cooling of the Proterozoic Terre Adélie craton at < ~120°C between 350 and 300 Ma, suggesting > 4 km temperate glacial erosion during the Late Palaeozoic Ice Age, followed by nearly null Mesozoic erosion and low glacial erosion (< 2 km) in the Cenozoic. Based on glacial flux maps, the origin of the boulders may be located ~400 km upstream. Preliminary TCN (10Be) datings of moraine boulders cluster within the last 30 ka. Cosmogenic ages from the Lacroix Nunatak suggest a main deglaciation after the …
Palaeomagnetism of the central Cuban Cretaceous Arc sequences and geodynamic implications
2009
Abstract A detailed palaeomagnetic study of Cretaceous age volcanic and sedimentary arc rocks from central Cuba has been carried out. Samples from 32 sites (12 localities) were subjected to detailed demagnetisation experiments. Nineteen sites from the Los Paso, Matagua, Provincial and Cabaiguan Formations yielded high unblocking temperature, dual polarity directions of magnetisation which pass the fold tests with confidence levels of 95% or more and are considered to be primary in origin. The palaeomagnetic inclinations are equivalent to palaeolatitudes of 9°N for the Aptian, 18°N for the Albian. A synfolding remanence identified in 5 sites from the younger Hilario Formation indicates a lat…
The Palaeomagnetism of the Permian Rocks of the Black Forest, Germany
1972
Summary Palaeomagnetic measurements made upon Permian samples from the Black Forest, Odenwald and Pfalzerwald (excluding those measurements on samples from the Schopfheim basin) are consistent with those from north-western Europe. The virtual pole based upon 18 sites is 174.9°E. 48.4N. The measurements made on the fine-grained shales and mudstones from the Schopfheim basin are significantly different from the preceding. Since incorrect age assignment, sampling, components of secondary magnetic and tectonic effects can be excluded, the difference is attributed to incomplete removal of the effects of secular variation. The Scharfenstein massif previously regarded as Permian, was found to have…