Search results for "pumice"
showing 10 items of 35 documents
Submarine deposits from pumiceous pyroclastic density currents traveling over water: An outstanding example from offshore Montserrat (IODP 340)
2017
© 2016. Geological Society of America. All right reserved. Pyroclastic density currents have been observed to both enter the sea, and to travel over water for tens of kilometers. Here, we identified a 1.2-m-thick, stratified pumice lapilli-ash cored at Site U1396 offshore Montserrat (Integrated Ocean Drilling Program [IODP] Expedition 340) as being the first deposit to provide evidence that it was formed by submarine deposition from pumice-rich pyroclastic density currents that traveled above the water surface. The age of the submarine deposit is ca. 4 Ma, and its magma source is similar to those for much younger Soufrière Hills deposits, indicating that the island experienced large-magnitu…
The pumice aggregates of Lipari Island (Aeolian Isles-Italy)
1984
In the Island of Lipari (Aeolian Archipelago) there is a large pumice deposit. The pumice is exploited in an open-cast mine through mechanical means and taken to crushing and screening plants. Aggregates for urban construction, gravel and powder are obtained. The aggregates are used in the manufacture of light concrete. Nowadays the possibility of using pumice aggregates in order to obtain light structural concrete is being studied.
Volatile dilution during magma injections and implications for volcano explosivity
2016
Magma reservoirs underneath volcanoes grow through episodic emplacement of magma batches. These pulsed magma injections can substantially alter the physical state of the resident magma by changing its temperature, pressure, composition, and volatile content. Here we examine plagioclase phenocrysts in pumice from the 2014 Plinian eruption of Kelud (Indonesia) that record the progressive capture of small melt inclusions within concentric growth zones during crystallization inside a magma reservoir. High-spatial-resolution Raman spectroscopic measurements reveal the concentration of dissolved H2O within the melt inclusions, and provide insights into melt-volatile behavior at the single crystal…
Volatiles in pantellerite magmas: A case study of the Green Tuff Plinian eruption (Island of Pantelleria, Italy)
2013
Abstract The Green Tuff (GT) Plinian eruption, the largest in magnitude at Pantelleria, erupted 3 to 7 km3 DRE of pantellerite magma and a small volume of trachyte. Fifty-nine anorthoclase-hosted melt inclusions from the two basal pumice members were analyzed by FT-IR spectroscopy in order to assess the pre-eruptive H2O content in the pantellerite melt. Microanalytical methods were used to determine major element, Cl, F and S contents. Melt inclusions and glassy groundmasses have a nearly homogeneous pantelleritic composition (peralkaline index = 1.9-2.2) and variable water contents ranging from 1.4 to as high as 4.2 wt %, i.e. much higher than the 1.4 wt % of earlier published studies. The…
Outgassing: Influence on speed of magma fragmentation
2013
[1] Predicting explosive eruptions remains an outstanding challenge. Knowledge of the controlling parameters and their relative importance is crucial to deepen our understanding of conduit flow dynamics and accurately model the processes involved. This experimental study sheds light on one important parameter—outgassing—and evaluates its influence on magma fragmentation behavior. We perform fragmentation experiments based on the shock tube theory at room temperature on natural pyroclastic material with a connected porosity ranging from 15% to 78%. For each sample series, we determine the initial pressure (P) required to initiate magma fragmentation (fragmentation threshold, Pth). Furthermor…
The use and beauty of ultra-high-resolution seismic reflection imaging in Late Quaternary marine volcaniclastic settings, Napoli Bay, Italy
2019
A Nápolyi-öbölben felvett ultra nagy felbontású egycsatornás (IKB-Seistec™) reflexiós szeizmikus szelvények korábbi geológiai és geofizikai vizsgálatok eredményeivel együtt kivételes, eddig soha nem látott felbontású szeizmikus leképezését nyújtják a Flegrei-mezők és a Somma-Vezúv felszín alá süllyedt késő-pleisztocén–holocén rétegtani felépí - tésének. A szeizmikus szelvényeken látott geometria és gravitációs magvevővel nyert üledékek adatainak összevetéséből Campania partközeli kontinentális talapzatán számos olyan üledékes és vulkáni szerkezet, valamint hidrotermális jelenség került leképezésre, melyek a legutolsó glaciális maximum (kb. 18 000 év) óta keletkeztek. A Pozzuoli-öbölben mért…
The structure of pumice: An XPS and27Al MAS NMR study
1992
In order to investigate the surface structure of pumice, an amorphous aluminosilicate, samples of pumice and of standards of silica and alumina have been studied by x-ray photoelectron spectroscopy (XPS). The effect of a mild acid leaching was also considered. The analysis of the Si 2p, Al 2p and O 1s photoelectron peaks and the Si KLL and O KLL Auger peaks indicated that pumice is formed by tetrahedral silica with some units being replaced by aluminate, AlO2−. The acid treatment decreases the alkali and the aluminate ions. X-ray photoelectron spectra of the valence band of pumices and of standards of Al2O3 and SiO2 agree with the core-level results. To support the conclusions from the XPS …
EXAFS and XRD study of Pd–Ag bimetallic catalysts supported on pumice from organometallic precursors
2001
Abstract Silver–palladium bimetallic catalysts were supported on pumice following different procedures, based on mild treatments of organometallic precursors. The experiments for the structural characterization of the synthesized samples, wide angle X-ray diffraction (XRD) and X-ray absorption spectroscopy, were carried out at the beamline GILDA of the European Synchrotron Radiation Facility. The analysis of the data demonstrated that alloying took place with a degree of homogeneity depending on the different preparation routes.
The holocene marine record of unrest, volcanism, and hydrothermal activity of campi flegrei and somma-vesuvius
2020
Abstract This chapter illustrates the marine record of a spectrum of volcanic, hydrothermal, and sedimentary features that characterize the Latest Pleistocene–Holocene evolution of the Naples Bay offshore Campi Flegrei and Somma–Vesuvius. The work is based on review of previous literature integrated with interpretation of new high-resolution marine Digital Terrain Models (DTMs) derived from swath bathymetry surveys and high-resolution reflection seismic profiles calibrated with marine gravity core data. Seismic profiles from Pozzuoli Bay provide detailed images of the ring fault system and resurgent dome associated with the evolution of the Neapolitan Yellow Tuff (NYT) collapse caldera and …
Pumice concrete for structural wall panels
2003
Some properties of lightweight pumice stone concrete (LWPSC) are discussed, on account of a possible structural use of this material. Then the results of an experimental investigation are described, in order to show that pumice can really be considered an alternative to common artificial lightweight aggregates, taking into account the performance pointed out by loading tests carried out on structural systems made of LWPSC. Three different kinds of reinforced wall panels were made using LWPSC, lightweight expanded clay concrete and normal weight concrete; then their structural responses under horizontal cyclic and constant vertical forces were compared, above all with reference to lateral st…