Thermodynamic and rheological properties of rhyolite and andesite melts

The heat capacities of a rhyolite and an andesite glass and liquid have been investigated from relative-enthalpy measurements made between 400 and 1800 K. For the glass phases, the experimental data agree with empirical models of calculation of the heat capacity. For the liquid phases, the agreement is less good owing to strong interactions between alkali metals and aluminum, which are not currently accounted for by empirical heat capacity models. The viscosity of both liquids has been measured from the glass transition to 1800 K. The temperature dependence of the viscosity is quantitatively related to the configurational heat capacity (determined calorimetrically) through the configurational entropy theory of relaxation processes. For both rhyolite and andesite melts, the heat capacity and viscosity do not differ markedly from those obtained by additive modeling from components with mineral compositions

A new era in hydrofluoric acid solution calorimetry: Reduction of required sample size below ten milligrams.

Significant advances have been made in hydrofluoric acid solution calorimetry at Lafayette College in the past 15 years. To determine the degree to which these developments enable the reduction of sample size, calorimetric experiments were performed on hexagonal germanium oxide as a function of sample weight. The resulting calorimetric data indicate that the highest degrees of reproducibility (60.1%) are maintained down to sample sizes of 50 mg, and that precisions of 61%, acceptable for many applications, are observed to sample sizes of 10 mg. Because silicate systems produce weight-based heats of solution that are about twice that of germanium oxide, the required sample size for these will be even less. The new minimum required sample size of 5 to 25 mg (depending on application) is about two orders of magnitude less than that used 20 or 30 years ago. This makes possible many new kinds of projects for HF solution calorimetric investigation, including those on high-pressure materials

Thermodynamic and rheological properties of rhyolite and andesite melts

The heat capacities of a rhyolite and an andesite glass and liquid have been investigated from relative-enthalpy measurements made between 400 and 1800 K. For the glass phases, the experimental data agree with empirical models of calculation of the heat capacity. For the liquid phases, the agreement is less good owing to strong interactions between alkali metals and aluminum, which are not currently accounted for by empirical heat capacity models. The viscosity of both liquids has been measured from the glass transition to 1800 K. The temperature dependence of the viscosity is quantitatively related to the configurational heat capacity (determined calorimetrically) through the configurational entropy theory of relaxation processes. For both rhyolite and andesite melts, the heat capacity and viscosity do not differ markedly from those obtained by additive modeling from components with mineral compositions

Isidore, Michel, Albert et autres penseurs latins et arabes : des regards médiévaux sur les volcans

Volcanism was not left out from the reflexions of medieval thinkers. With Isidore of Seville in Spain and Bede the Venerable in England, volcanic fire acquired in the 7th and 8th centuries a moral significance with respect to that of hell. Simply denoted by mountains of fire by the Greeks and Romans, volcanoes acquired their name in the Arabic literature after the conquest of Sicily. In an island that was reconquered by the Normans, a rich intellectual life took place in the 13th century at the Palermitan court of Frederick II Hohenstaufen. A testimony is probably the most detailed medieval account of volcanism that was given by the great translator Michael Scot who introduced in it alchemical considerations. At the same period Albertus Magnus investigated in Germany the explosive effect of waters coming in contact with fire during an eruption. When mentioning also the speculations of a 12th-century author named Marius on the rock transformations induced by fire in the interior of the Earth, one must conclude that the Middle Ages should not be excluded from the history of volcanology.Le volcanisme ne resta pas à l'écart des réflexions des penseurs médiévaux. Avec Isidore de Séville en Espagne, puis Bède le Vénérable en Angleterre, le feu des volcans acquit aux VII e et VIII e siècles une signification morale en rapport avec celui de l'enfer. Simplement nommés montagnes de feu par les Grecs et les Romains, les volcans prirent leur nom dans la littérature arabe après la conquête de la Sicile. Dans une île reconquise par les Normands, une intense activité intellectuelle prit place au XIII e siècle à la cour palermitaine de Frédéric II Hohenstaufen. Un témoignage en fut l'exposé médiéval sans doute le plus détaillé du volcanisme que présenta alors le grand traducteur Michel Scot en y mêlant des considérations alchimiques. À la même époque, Albert le Grand effectua en Allemagne une première étude expérimentale du pouvoir explosif d'eaux entrant en contact avec des feux lors d'une éruption. En mentionnant aussi les spéculations d'un auteur du XII e siècle nommé Marius sur les transformations des roches induites par le feu dans les profondeurs de la Terre, on doit conclure que le Moyen âge ne doit pas être exclu de l'histoire de la volcanologie

The Creation of the world and the birth of chronology

International audienc

Preface of the Proceedings of the 47th Inhigeo Symposium edited by Gaston Godard, Philippe Grandchamp and Pascal Richet

Proceedings of the 47th Inhigeo Symposium edited by Gaston Godard, Philippe Grandchamp and Pascal Richet. INHIGEO Symposium - Les Eyzies, FRANCE (15-24 September 2022) - organized by Claudine Cohen, Françoise Dreyer, Gaston Godard, and Pascal RichetInternational audiencePreface of the Proceedings of the 47th Inhigeo Symposium edited by Gaston Godard, Philippe Grandchamp and Pascal Richet. INHIGEO Symposium - Les Eyzies, FRANCE (15-24 September 2022) - organized by Claudine Cohen, Françoise Dreyer, Gaston Godard, and Pascal Riche

Heat capacity of liquid silicates: new measurements on NaAISiO8 and K2SiO9

International audienceDrop calorimetric measurements of HT-H273 are reported for glassy and liquid albite and potassium tetrasilicate for the temperature interval 600–1500 K. Analysis of these observations as well as data for 13 other stable and supercooled silicate liquids suggests strongly that the isobaric heat capacities of stable and supercooled liquids are equal and thus temperature independent. Available evidence indicates that the isochoric heat capacities of liquid alkali silicates are also temperature independent within present experimental uncertainties