Search results for "volcan"
showing 10 items of 899 documents
Unravelling textural heterogeneity in obsidian:shear-induced outgassing in the Rocche Rosse flow
2016
Obsidian flow emplacement is a complex and understudied aspect of silicic volcanism. Of particular importance is the question of how highly viscous magma can lose sufficient gas in order to erupt effusively as a lava flow. Using an array of methods we study the extreme textural heterogeneity of the Rocche Rosse obsidian flow in Lipari, a 2. km long, 100. m thick, ~. 800. year old lava flow, with respect to outgassing and emplacement mechanisms. 2D and 3D vesicle analyses and density measurements are used to classify the lava into four textural types: 'glassy' obsidian (<. 15% vesicles), 'pumiceous' lava (>. 40% vesicles), high aspect ratio, 'shear banded' lava (20-40% vesicles) and lo…
Materials and Tools across Volcanoes: Exploitation of Georesources in Piano dei Cardoni (Ustica, Italy) during Prehistory.
2021
The paper aims at merging the first results from the analyses of the georesources exploited in the site of Piano dei Cardoni (Ustica island, Italy) during the Neolithic phases of its occupation (Middle-Late Neolithic, 4.7-4.2 ka cal BC). Grinding tools consist of a very varied typology of local volcanic rocks, easy to collect and available very close to the investigated site. A selection of shapes and lithology is applied to reach the best performance of the tools. The elevated number of grinders, pestles, mortars testify to an intense activity of food/plant processing in the site. The absence of chert or obsidian resources on the island pushed the human communities to import such raw ma…
Stratospheric sulfur and its implications for radiative forcing simulated by the chemistry climate model EMAC
2015
Multiyear simulations with the atmospheric chemistry general circulation model EMAC with a microphysical modal aerosol module at high vertical resolution demonstrate that the sulfur gases COS and SO2, the latter from low-latitude and midlatitude volcanic eruptions, predominantly control the formation of stratospheric aerosol. Marine dimethyl sulfide (DMS) and other SO2 sources, including strong anthropogenic emissions in China, are found to play a minor role except in the lowermost stratosphere. Estimates of volcanic SO2 emissions are based on satellite observations using Total Ozone Mapping Spectrometer and Ozone Monitoring Instrument for total injected mass and Michelson Interferometer fo…
A revised stratigraphy of the pre-Green Tuff ignimbrites at Pantelleria (Sicily Channel)
2012
Peralkaline silicic magmas were erupted at Pantelleria in a variety of eruptive typologies and magnitudes: pyroclastic flows, Plinian to strombolian pumice fallout and lava flows. The initial cycle (330- 180 ka) was characterized mainly by effusive activity, and was followed by an intermediate cycle (181 - 85 ka), characterized by a clear drift to explosive activity. This period, onto we focus, is bracketed by six ignimbrite-forming eruptions (older and intermediate of the two caldera collapses at 140 and 50 ka that characterize the volcanological history of the island, which drained silicic and variably peralkaline magma for a cumulative volume close to 6 km3 DRE. These ignimbrites lack of…
Volcanological evolution of Pantelleria Island (Strait of Sicily) peralkaline volcano: a review
2022
International audience; Pantelleria volcano has a particularly intriguing evolutionary history intimately related to the peralkaline composition of its explosively erupted magmas. Due to the stratigraphic complexity, studies over the last two decades have explored either only the pre-Green Tuff ignimbrite volcanism or the post-Green Tuff activity. We here focus on the whole evolutionary history, detailing the achievements since the first pioneering studies, in order to illustrate how the adoption and integration of progressively more accurate methods (40 Ar/ 39 Ar, paleomagnetism, petrography, and detailed field study) have provided many important independent answers to unresolved questions…
Late Cretaceous palaeoenvironments expressed by the clay mineralogy of Cenomanian–Campanian chalks from the east of the Paris Basin
2005
Abstract The clay fraction of Cenomanian–Campanian chalks cored at Poigny and Sainte-Colombe, close to Provins (east-south-east of Paris), includes variable proportions of smectitic minerals, illite and kaolinite. The smectitic sediments (which constitute the background of low-terrigenous supply throughout the stratigraphic interval) resulted mainly from the warm, humid climate and high sea level that prevailed during Late Cretaceous in this area. During the Late Turonian, the smectitic sedimentation was interrupted by significant detrital inputs of illite and kaolinite. This reflected tectonic rejuvenation of landmasses coeval with an explosive volcanism expressed by the occurrence of bent…
Collapse structures in the Permian of the Saar-Nahe area, Southwest Germany
1971
Volcanic breccias near an intrusive rhyolite dome in the Permian Saar-Nahe trough of southwest Germany have been identified as complex pipe-like subsidence-structures occupying the site and immediate neighbourhood of “explosive” volcanoes.
Contrôle géodynamique de la sédimentation argileuse du Callovien-Oxfordien moyen dans l'Est du bassin de Paris: influence eustatique et volcanique
1999
The Middle Callovian to Middle Oxfordian clay deposits drilled in the eastern Paris Basin (borehole HTM 102, ANDRA) show a strong mineralogical change occurring in the lowermost Oxfordian (Scarburgense subzone, Mariae zone). Such a change probably results from the initial development of connections between the young Atlantic Ocean and the Paris Basin. A bentonitic layer identified close to the boundary between Lower and Middle Oxfordian and also recognized in the subalpine Basin (South-East of France) at the same age, reflects a volcanic activity probably resulting from an extensional regime located in the North Sea.
Climate change and the collapse of the Akkadian empire: Evidence from the deep sea
2000
The Akkadian empire ruled Mesopotamia from the headwaters of the Tigris-Euphrates Rivers to the Persian Gulf during the late third millennium B.C. Archeological evidence has shown that this highly developed civilization collapsed abruptly near 4170 ± 150 calendar yr B.P., perhaps related to a shift to more arid conditions. Detailed paleoclimate records to test this assertion from Mesopotamia are rare, but changes in regional aridity are preserved in adjacent ocean basins. We document Holocene changes in regional aridity using mineralogic and geochemical analyses of a marine sediment core from the Gulf of Oman, which is directly downwind of Mesopotamian dust source areas and archeological si…
27. A new holsteinian pollen record from the dry maar at Döttingen (Eifel)
2007
Abstract A new interglacial pollen sequence from the Dottingen dry maar in the Eifel region of the Rheinish Schield is presented. Palynology is used to correlate with several classical north German Holsteinian sites. The lake sediments reveal the complete interglacial and also 60 m of laminated sediments from the glacial preceding the Holsteinian. The interglacial section indicates limnic conditions in its lower part and telmatic conditions in its upper part with an intermediate episode of peat formation. Ash layers document intensive volcanism during the interglacial in the Eifel region. Some of the north German Holsteinian sites reveal spikes of high abundance of Pinus, Betula and Poaceae…