Search results for "Impact crater"
showing 10 items of 134 documents
Rapid oxidation of mercury (Hg) at volcanic vents: Insights from high temperature thermodynamic models of Mt Etna's emissions
2011
A major uncertainty regarding the environmental impacts of volcanic Hg is the extent to which Hg is deposited locally or transported globally. An important control on dispersion and deposition is the oxidation state of Hg compounds: Hg(0) is an inert, insoluble gas, while Hg(II) occurs as reactive gases or in particles, which deposit rapidly and proximally, near the volcanic vent. Using a new high temperature thermodynamic model, we show that although Hg in Etna's magmatic gases is almost entirely Hg(0) (i.e., gaseous elemental mercury), significant quantities of Hg(II) are likely formed at Etna's vents as gaseous HgCl2, when magmatic gases are cooled and oxidised by atmospheric gases. Thes…
On the formation of maars
1973
The Pleistocene maars in the Eifel region of Germany, and Massif Central in France, formed when fissures opened at the bottom of older valleys allowing stream water to pour down them and come into contact with rising magma. The resulting phreato-magmatic eruptions gave rise to both base surge and air-fall deposits. Spalling of wall rock at depth enlarged the fissure into an eruption chamber. Subsidence along a ring fault into the eruption chamber accounts for the larger crater cut into the country rocks. The volume relationship between the crater excavated, the ejected pyroclastic debris of the rim and the volume below the floor of the crater, indicates that the volume of the maar ejecta is…
Soil and fumarole gases of Mount Etna: geochemistry and relations with volcanic activity
1998
Abstract Between 1993 and 1996, gas samples were collected on Mt. Etna volcano from both high- and low-temperature fumaroles and from soils in areas of anomalous degassing located on the flanks of the volcanic edifice. The chemical composition of all the emitted gases is consistent with their magmatic origin. During their transport to the surface, they would undergo shallow mixing processes, mostly with air. Locally, as in the case of a point in the lower southwestern flank of the volcano (P39), very high contents of He and CH4 indicate that deep gases mainly interact with ground waters and also with a hydrocarbon reservoir. The isotopic composition of carbon in CO2 from these gases also su…
CO 2 output and δ 13 C(CO 2 ) from Mount Etna as indicators of degassing of shallow asthenosphere
1997
An estimated average CO2 output from Etna's summit craters in the range of 13±3 Mt/a has recently been determined from the measured SO2 output and measured CO2/SO2 molar ratios. To this amount the CO2 output emitted diffusely from the soil (≈ 1 Mt/a) and the amount of CO2 dissolved in Etna's aquifers (≈ 0.25 Mt/a) must be added. Data on the solubility of CO2 in Etnean magmas at high temperature and pressure allow the volume of magma involved in the release of such an amount of this gas to be estimated. This volume of magma (≈ 0.7 km3/a) is approximately 20 times greater than the volume of magma erupted annually during the period 1971–1995. On the basis of C-isotopic data of CO2 collected in…
Long-time variation of soil CO2 fluxes at the summit crater of Vulcano (Italy)
2012
Here, we report the first continuous data of geochemical parameters acquired directly from the active summit crater of Vulcano. This approach provides a means to better investigate deep geochemical processes associated with the degassing system of Vulcano Island. In particular, we report on soil CO2 fluxes from the upper part of Vulcano, a closed-conduit volcano, from September 2007 to October 2010. Large variations in the soil CO2 and plume SO2 fluxes (order of magnitude), coinciding with other discontinuous geochemical parameters (CO2 concentrations in fumarole gas) and physical parameters (increase of shallow seismic activity and fumarole temperatures) have been recorded. The results fro…
The evolution of a dynamic geological system: the support of a GIS for geochemical measurements at the fumarole field of Vulcano, Italy
1997
The island of Vulcano (Aeolian arc, Southern Italy) has displayed several periods of volcanic unrest since the end of the last eruption (1890). We report here results obtained from a long-term survey concerning variations of both the steam output and the exhaling surface area at the summit crater fumarolic field of La Fossa. The field measurements analysed in a Geographical Information System (GIS) show a highly dynamic volcanic system in which deep variations in the geochemistry and the temperature of the released fluids were accompanied by fluctuations in the mass output of steam and the topography of the crater field. The use of a GIS facilitated digitized reconstructions of maps of the …
Degassing of trace volatile metals during the 2001 eruption of Etna
2003
This paper provides new data on sulfur, halogens, and minor and trace metal contents in airborne particulate matter from the Mt. Etna volcanic plume. Aerosol samples were collected by conventional filtration techniques before and during the summer 2001 eruption, in order to investigate relations between plume chemistry and volcano dynamics. Data analysis reveals that abundances of trace metals in the plume result from mixing of erosive and volatile components. The former is responsible for the contents of rare earth elements (REE), Ca, Ba, Sr, Ti, Sc, Y, Hf and Th; the latter contributes significantly to the abundance of Cs, Rb, Na and K, probably transported in the plume as metal halides, …
Active moss monitoring allows to identify and track distribution of metal(loid)s emitted from fumaroles on Vulcano Island, Italy
2014
Abstract Volatile metal(loid)s are known to be emitted from volcanoes worldwide. We tested the suitability of active moss monitoring for tracking volatile metal(loid)s released from the fumarolic field on Vulcano Island, Italy, and differentiated fumaroles from other sources of gaseous and particulate trace elements such as sea spray and soil. Metal(loid) accumulation on the mosses per day did depend neither on the state of the exposed moss (dead or living) nor exposure time (3, 6, or 9 weeks). After collection, mosses were digested with either HNO3/H2O2 or deionized water and analyzed by ICP-MS. While for most elements both extraction methods yielded similar concentrations, higher concentr…
Real-time simultaneous detection of volcanic Hg and SO2at La Fossa Crater, Vulcano (Aeolian Islands, Sicily)
2007
Measuring Hg/SO2 ratios in volcanic emissions is essential for better apportioning the volcanic contribution to the global Hg atmospheric cycle. Here, we report the first real-time simultaneous measurement of Hg and SO2 in a volcanic plume, based on Lumex and MultiGAS techniques, respectively. We demonstrate that the use of these novel techniques allows the measurements of Hg/SO2 ratios with a far better time resolution than possible with more conventional methods. The Hg/SO2 ratio in the plume of FO fumarole on La Fossa Crater, Vulcano Island spanned an order of magnitude over a 30 minute monitoring period, but was on average in qualitative agreement with the Hg/SO2 ratio directly measured…
First 13C/12C isotopic characterisation of volcanic plume CO2
2010
We describe analytical details and uncertainty evaluation of a simple technique for the measurement of the carbon isotopic composition of CO2 in volcanic plumes. Data collected at Solfatara and Vulcano, where plumes are fed by fumaroles which are accessible for direct sampling, were first used to validate the technique. For both volcanoes, the plume-derived carbon isotopic compositions are in good agreement with the fumarolic compositions, thus providing confidence on the method, and allowing its application at volcanoes where the volcanic component is inaccessible to direct sampling. As a notable example, we applied the same method to Mount Etna where we derived a δ13C of volcanic CO2 betw…