Volcanic plume thermal radiation: 1972 eruption of piton de la fournaise, Réunion Island

Using an infrared radiometer, the authors measured the infrared radiation emitted by the plume during the 1972 Piton de la Fournaise (Réunion Island) eruption in the 9.1- to 11.9-μm range.Eight histograms summarize twenty hours of continuous measurements and show a flux between 0.557 and 1.279 W/cm² with an average of 0.88 W/cm². The greatest number of events correspond to the flux emitted by lava fountains, while the high and rare flux values (4–6 W/cm²) correspond to detonations of chemical explosions, probably of H₂ and O₂.After calibration in the laboratory on a reference black body and in the field by correlation with field observations, such a technique can be used to follow changes of volcanic activity in remote and dangerous spots. Information on the number of explosions, their magnitude, and the presence and relative significance of hot magma can be transmitted continuously to a safe place.     

Quantitative evaluation of fractional crystallization in Bouvet Island lavas

Bouvet Island, situated near the southernmost end of the Mid-Atlantic Ridge, is characterized by lavas ranging in composition from hawaiite through mugearite and benmoreite to rhyolite. Major and trace elements vary systematically throughout the sequence, as do mineral compositions, and geochemical modelling indicates that the compositional variations observed in the differentiated lavas can be ascribed to extensive fractional crystallization of a parental hawaiite magma. Following this scheme the hawaiite parent magma experienced approximately 44% fractional crystallization of plagioclase + clinopyroxene + olivine + opaque oxides and minor apatite to give rise to the mugearite magma, which in turn experienced a further 69% fractional crystallization of the same phase assemblage (though with more evolved compositions) to give rise to the Bouvet Island rhyolite. Extensive fractional crystallization (64%), possibly separated in time, of the parental hawaiite gave rise to the benmoreite magma. In the latter scheme the fractionating phases are similar both in composition and proportion to those crystallizing in the passage from hawaiite to mugearite, suggesting that the Bouvet Island hawaiites correspond in composition to a six phase (plag + of + cpx + Fe-Ti oxide + ap+ lq) saturation surface and that the more differentiated lavas resulted from differing degrees of crystallization on this surface.     

太阳十厘米射电流量与太阳运动

本文利用１９４７ ～１９９０ 年加拿大Ｏｔｔａｗａ 的２８００ ＭＨｚ 太阳射电流量与太阳绕太阳系质心运动的角动量变化率ｄＬ／ｄｔ 做线性相关,当迟滞时间τ～３ 年得相关系数为０ ．８２２ ,线性相关置信水平远大于９９ ．９ ％ 。本文还用同期的太阳黑子相对数与太阳角动量变化率ｄＬ／ｄｔ 做线性相关,当迟滞时间τ～２ － ３ 年得相关系数为０ ．８２９ ,其置信水平亦远大于９９ ．９ ％ ,证实了董士仑在１９９７ 年在天体物理学报发表的结果（１９００ － １９８０ 年,τ～２ 年,相关系数为０ ．８１）     

The chemistry of magmatic gases from Erta'Ale,Ethiopia

The chemical composition of the gases emitted from a hornito close to the active lava lake of Erta'Ale, Ethiopia, as derived from chemical analyses on 18 samples collected on 23 January 1974, was found to be (in mol-%): H₂O: 79.4, CO₂: 10.4, total S: 7.36, HCl: 0.42, H₂: 1.49, N₂: 0.18, Ar: 0.001, CO: 0.46, and COS: 0.009. Thermodynamic considerations, based on the equilibria CO₂ + H₂ ? CO + H₂O and CO₂ + 3H₂ + SO₂ ? COS + 3H₂O show that the analytical values represent the equilibrium composition of a gas mixture at the measured temperature of around 1130°C under close to the surface pressure conditions. Comparison of the Erta'Ale gas emissions with those from other volcanoes suggests a close similarity in their chemical composition. This similarity is considered to be due to common processes governing the release of gaseous species from a magma.     

The effect of prolonged X-ray irradiation on lithium tetraborate glass discs as used in X.R.F. analyses

Prolonged irradiation by X-rays of lithium tetraborate glass discs causes significant changes in countrates for certain elements e.g. Na and Mg decrease while Al, Si and P increase. This effect is probably due to surface diffusion in the glass as grinding away about 10 μm of the surface of the disc restores the countrates to their original levels. Although no change in countrates will ever be noticed on individual glass discs undergoing routine analyses, where irradiation time is only a minute or so, a close watch must be kept on any specimens that have been irradiated for more than a few tens of hours.     

10 Hygiea: ISO Infrared Observations

Observations of emissivity features of 10 Hygiea have been made for the first time in the relatively unexplored thermal-infrared wavelength region with the ISO (Infrared Space Observatory) satellite. Spectrophotomer (PHT-S) and short wavelength spectrometer (SWS) spectra of 10 Hygiea, obtained at 5.8-11.6 and 7-45 μm, respectively, are presented. In order to remove the thermal emission continuum, an advanced thermo-physical model has been applied to the observational data. To better interpret the spectral features above the thermal emission continuum, we compared the ISO observations with laboratory spectra available in the literature. Several laboratory experiments on minerals and meteorites have been performed to complete the analysis and to study the spectral behavior at various grain sizes. A possible spectral similarity with CO carbonaceous chondrites at small grain size is demonstrated.     

First observations in a high rocky-shore community after the Erika oil spill (December 1999, Brittany,France)

The high mediolittoral rocky-shore community on the island of Groix (Brittany, France), was studied for the year immediately following the Erika oil spill (12/12/1999). The macrofaunal assemblages of three habitats (exposed bedrock, crevices, boulders) under three situations (non-impacted, impacted and not washed, impacted and washed) were monitored monthly. The assemblage of each habitat showed specific responses to the impacts and initiated various patterns of succession: the bed rock assemblage changed in terms of abundance but no species-richness variations occurred; in the crevices richness variations occurred both in the disappearance of some species and the immigration of opportunistic ones; the boulder assemblage lost many species and remained unstructured one year after the oil spill. These first results of this most recent oil spill in Europe, raised the question of the relative importance of habitat-species and species interactions on the community structure.     

Long-term thermal evolution and effect of low power heating in an underground quarry

Vertical profiles of temperature have been monitored in the atmosphere of an underground quarry since June 2001. A long-term temperature increase of the order of 0.1 °C per year is observed. Three heating experiments with 100-W sources, performed to study plume dynamics, can also be used to investigate the effect of visits on this increase. Ten days after the 24-h heatings, the initial state is not restored. Artificial contributions to the observed long-term temperature trend, triggered by internal heat release, thus cannot be ruled out. This experiment defines strict criteria for the underground monitoring of global warming or the preservation of painted caves. To cite this article: C. Crouzeix et al., C. R. Geoscience 335 (2003).