The structures of albite and jadeite composition glasses quenched from high pressure

The structures of jadeite and albite composition glasses quenched from 10 and 15 kbar, respectively, have been studied using radial distribution analysis. It is found that aluminum does not undergo a coordination increase at these pressures, in agreement with recent Raman and NMR studies of these glass compositions. Radial distribution functions (RDF's) indicate that the structural response of albite and Jadeite composition melts to pressure up to 10–15 kbar has to do primarily with a distortion of the tetrahedral sites, a slight collapse of the tetrahedral rings forming the framework, and a small loss of short range order resulting in a more densely packed framework structure. The RDF's do not provide any clues concerning T-O-T angular changes at these pressures. It is suggested that the observed structural changes should be closely related to those that take place in melts of rhyolitic composition. Such changes in rhyolitic melts would result in a density increase and viscosity decrease with increasing pressure similar to that observed for melts of albite and jadeite composition.     

Oceanographic studies supporting the assessment of deep-sea disposal of defueled decommissioned nuclear submarines

Based on criteria developed by the international Atomic Energy Agency (IAEA), potential disposal sites for defueled, decommissioned nuclear submarines appear to exist in deep water south of the Mendocino Fracture Zone within 200 nautical miles of the United States Oceanographic measurements in the water column and at the sea floor in a study area (W-N) at 39 5°N, 127 5°W will allow the operational and radiological consequences of deep-sea disposal to be compared with land burial of old submarines. The W-N studies also are yielding new data that will provide insights to the deposition and early diagenesis of distal hemipelagic sediments Royalty-free reproduction of this article by the U S Government or by the authors for U S. Government purposes is permitted.     

X-ray K-edge absorption spectra of Fe minerals and model compounds: II. EXAFS

K-edge extended X-ray absorption fine structure (EXAFS) spectra of Fe in varying environments in a suite of well-characterized silicate and oxide minerals were collected using synchrotron radiation and analyzed using single scattering approximation theory to yield nearest neighbor Fe-O distances and coordination numbers. The partial inverse character of synthetic hercynite spinal was verified in this way. Comparison of the results from all samples with structural data from X-ray diffraction crystal structure refinements indicates that EXAFS-derived first neighbor distances are generally accurate to ±0.02 Å using only theoretically generated phase information, and may be improved over this if similar model compounds are used to determine EXAFS phase functions. Coordination numbers are accurate to ±20 percent and can be similarly improved using model compound EXAFS amplitude information. However, in particular cases the EXAFS-derived distances may be shortened, and the coordination number reduced, by the effects of static and thermal disorder or by partial overlap of the longer Fe-O first neighbor distances with second neighbor distances in the EXAFS structure function. In the former case the total information available in the EXAFS is limited by the disorder, while in the latter case more accurate results can in principle be obtained by multiple neighbor EXAFS analysis. The EXAFS and XANES spectra of Fe in Nain, Labrador osumulite and Lakeview, Oregon plagioclase are also analyzed as an example of the application of X-ray absorption spectroscopy to metal ion site occupation determination in minerals.     

Shoreline changes along the southeastern coast of Martha's Vineyard, Massachusetts for the past 200 years

Shoreline changes since 1776, including two 30-yr periods separated by nearly 100 yr are documented from surveys, topographic maps, harbor charts, and aerial photographs for the southeastern corner of the island of Martha's Vineyard, Massachusetts (41°25′ N, 70°35′ W). From 1776 to 1969, a barrier beach has receded by more than 880 m, and average rate of 4.6 m/yr. A series of four detailed surveys from 1840 to 1886 document consistent shoreline retreat in this area of 3.1 m/yr.For the period 1938–1969, planimetry from aerial photographs and field observation indicate that more than 28 ha and nearly 3 × 10⁶ m³ of foreland composed of till have washed away. A house, located 200 m from the cliff edge of the foreland in 1938 was only 56 m from the cliff edge in July 1972.Violent storms were associated with the opening of the bay behind the barrier beach in nearly the same location in 1856, 1886, 1938, and 1954. Easterly migration of the opening results in rapid erosion of the southeastern corner of the island (Wasque Point) and eventual closing of the opening.Field observation of the 1954 opening indicates that the mechanism of failure of the barrier beach is primarily by storm tide-induced subsidence. Subsequently, strong (up to 1.2 mps) easterly currents cause migration of the opening to the east and closure within 15 yr.A summary review of evidence for changes in sea level in the past is suggested in partial explanation for the consistent shoreline retreat described in this paper.     

Die Küste Dithmarschens im Kartenbild von 1559

Zusammenfassung Seit langer Zeit liegt in der österreichischen Nationalbibliothek in Wien ein Karten-Unikum: der Original-Holzschnitt von Petrus Boeckels Karte von Dithmarschen wÄhrend der Unterwerfung 1559. Eine ganze Reihe von Nachbildungen bis etwa 1608 und sodann ein Kupferstich in einer — inzwischen recht selten gewordenen — Chronik von A. Vieth, 1733, haben in der Literatur zu Verwechslungen und Irrtümern Anla\ gegeben. Wahrscheinlich, weil die meisten Verfasser, bis in neueste Zeiten, das Original in Wien nie gesehen haben.Zu einer Besprechung der Originalkarte erwies es sich zuallererst als nötig, die verschiedenen Karten ganz scharf zu unterscheiden, um erneute Mi\verstÄndnisse zu vermeiden. — Im folgenden sollen die Karten einzeln behandelt und ihre Beziehungen oder AbhÄngigkeiten klargestellt werden (vgl. Tab. 1, S. 167). Dazu war es erforderlich, wo dies nur irgend ging, den Bildma\stab der BlÄtter als eines der wichtigen Unterscheidungsmittel trotz vieler schwerwiegender zeichnerischer Verzerrungen zu berechnen.Diese topographischen Verzerrungen beeintrÄchtigen aber nicht die hervorragende Leistung Boeckels, der damals in einer Zeit grö\ter Fortschritte der Kartographie eine landmesserische Arbeit zustande gebracht hat, die nicht hoch genug bewertet werden kann. Dieser Gesichtspunkt soll durch Vergleich mit zeitgenössischen Karten gewürdigt werden.

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The coast of Dithmarschen as it is represented on maps edited in about 1559 and later

Summary For a long time, the National Library of Austria in Vienna is holding the unique of a map: the original wood engraving by Petrus Boeckel showing the land of Dithmarschen (Schleswig-Holstein) at the time of the conquest by King Frederic II of Denmark and the Dukes of Schleswig-Holstein in 1559. Quite a number of copies dating from the time between 1559 to about 1608 and a copper engraving, included in a chronicle — now rare — by Vieth 1733, gave rise to many confusion and mistakes in literature, apparently due to the fact that, up to the present time, most of the authors never saw the original wood engraving itself.The discussion of the original map made it necessary to first clearly discriminate between the different maps in order to avoid new misunderstandings. For this reason, the maps in question are individually discussed and their interdependency is laid open (cf. table 1, page 167). Another requirement was the computation of the maps' scales as one of the most discriminative means; this had to be done whenever such computation proved feasible and in spite of many grave topographic distortions residing in the drawing.The topographic distortions may, however, not be regarded as detrimental to Boeckel's remarkable achievement who, at an epoch of eminent progress in cartography, accomplished a survey work of great value. In support of this appreciation a comparison is made with contemporary maps.

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La cÔte du pays des Dithmarses comme elle se trouve représentée sur les cartes géographiques parues en et après 1559

Résumé La Librairie Nationale de l'Autriche à Vienne possède depuis longtemps l'exemplaire unique d'une carte géographique: l'Original de la gravure sur bois par Petrus Boeckel. Cette gravure représente le pays des Dithmarses à l'époque de sa conquÊte en 1559 par le roi Frédéric II de Danemark et les ducs de Slesvig-Holstein. Toute une série de copies publiées jusqu'à 1608 environ ainsi qu'une gravure en taille douce — entretemps devenue très rare — qui fait part d'une chronique de 1733 par A. Vieth, ont donné lieu, en littérature, à des confusions et des erreurs, apparemment dues au fait que la plupart des auteurs n'ont jamais eu l'occasion de regarder de leurs propres yeux l'original à Vienne.La discussion de la carte originale exigea en premier lieu, de séparer nettement les diverses cartes pour éviter la formation d'autres erreurs. Pour cette raison, le travail actuel soumet les cartes en question à une étude individuelle (voir le tableau 1, page 167). Le calcul de l'échelle des cartes différentes s'étant montré un des moyens de distinction les plus essentiels, on s'est mis dans ce travail à ce calcul malgré le grand nombre de graves distortions au point de vue du dessin.Ces distorsions topographiques ne déprécient pas, cependant, la valeur des remarquables travaux cartographiques de Boeckel, qui a effectué des levés topographiques d'une grande utilité à une époque d'éminents progrès dans le domaine de la cartographie. Pour soutenir cet aspect, la carte de Boeckel est comparée avec des cartes géographiques contemporaines.

     

A low latitude general circulation model

Summary The primitive equations of motion are solved to find peak latitudes of families of trajectories of air moving from low latitudes towards the pole from a state of rest under the action of a constant meridional pressure gradient. The general case is discussed first and then calculations are applied to the 20° West meridian in January and July for the Northern Hemisphere.The resulting mass transposition indicates that a belt of convergence should occur at about 32° N in January; this agrees well with the latitude of the axis of the mean sub-tropical high pressure belt at that time of year.The nature of the climatological model in low latitudes suggested by the calculation is then discussed.

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Zusammenfassung Die vereinfachten Bewegungsgleichungen werden gelöst, um Scheitelbreiten für Trajektorienscharen der Luftbewegungen zu finden, die ausgehend von dem Ruhezustand unter Einwirkung eines konstanten meridionalen Druckgradienten polwärts gerichtet sind. Der allgemeine Fall wird diskutiert und es werden Berechnungen für den 20. westlichen Längengrad der Nordhemisphäre für Januar und Juli durchgeführt.Der resultierende Massentransport zeigt, daß im Januar in 32° N ein Konvergenzgürtel auftreten sollte. Dies stimmt gut überein mit der geographischen Breite der Achse des mittleren subtropischen Hochdruckgürtels zu dieser Jahreszeit.Schließlich wird die Form des klimatologischen Modells für niedere Breiten, das durch diese Berechnungen nahegelegt wird, diskutiert.

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Résumé Résolution des équations simpflifiées du mouvement pour déterminer l'origine des faisceaux de trajectoires des courants aériens qui, partant du repos, sont dirigés vers le pôle sous l'effet d'un gradient constant de pression méridien. Discussion du cas général; calcul pour le 20^e méridien Ouest de l'hémisphère Nord en janvier et en juillet.Le transport de masse résultant montre qu'il doit y avoir en janvier, a 32° de latitude Nord, une ceinture de convergence ce qui concorde bien avec la latitude de l'axe de la zone moyenne des hautes pressions subtropicales en cette saison.Forme du modèle climatologique aux basses latitudes suggéré par ces calculs.

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Temperature trends in England, 1698–1957

Summary Comparable figures representative of the mean temperature at inland places in Central England are provided for every month from 1698 to the end of 1957. These are based on the assemblage of a number of early and scattered records brought to modern standards and to centigrades. Diagrams are added for purposes of illustration and comparison with Holland and elsewhere in Europe.

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Zusamenfassung Es werden Vergleichszahlen für die Mitteltemperatur an Inlandstationen in Mittelengland für alle Monate von 1698 bis 1957 mitgeteilt; sie beruhen auf der Verarbeitung einer Anzahl älterer und vereinzelter Serien, die auf neuzeitlichen Stand und auf Zentigrade reduziert wurden. Zur Veranschaulichung und zum Vergleich mit holländischen und anderen europäischen Stationen sind Kurvendarstellungen beigefügt.

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Résumé Moyennes mensuelles de température de stations de l'Angleterre centrale, de la période 1698 à 1957, tirées de séries anciennes convenablement réduites et converties en degrés centigrades. Des représentations graphiques facilitent la comparaison avec les stations européennes.

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Experimental studies of the distribution of rare earths as trace elements among silicate minerals and liquids and water

The distribution of the REE between synthetic diopside, forsterite, enstatite, and gaseous water and between natural plagioclase, 2 rhyolite obsidian melts and gaseous water have been measured. Values for distribution coefficients (D) for the REE between the minerals and aqueous fluid vary significantly over the temperature range of 550°C to 850°C, but little variation was found for the values of D between the silicate liquids and aqueous fluid over a temperature range of 100°C. By assuming that the values of D for the silicate liquids are independent of major element composition and temperature, it is possible to calculate values of D for REE between silicate minerals and silicate liquid. The values obtained for diopside, forsterite, enstatite and plagioclase compare favorably with those obtained for the natural materials clinopyroxene, olivine, orthopyroxene and plagioclase (except for Eu). The values of D for diopside were found to increase and those for forsterite and enstatite to decrease with increasing temperatuie. Values of temperature of equilibration for natural minerals obtained by extrapolation of graphs for experimental data of In D against 1/T for the systems diopside-silicate liquid, forsterite-silicate liquid, and forsterite-diopside fall within a reasonable range, suggesting the possibility of geothermometry using REE concentrations of minerals.     

Geodiversity and the ‘8Gs’: a response to Brocx & Semeniuk (2019)

Abstract

Brocx and Semeniuk’s (2019 Brocx, M., & Semeniuk, V. (2019). The ’8Gs’ – a blueprint for geoheritage, geoconservation, geo-education and geotourism. Australian Journal of Earth Sciences, 66(6), 803–821. doi:10.1080/08120099.2019.1576767[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]) paper is discussed, particularly in relation to the concept of geodiversity and their proposed sequence of ‘8Gs’. Their ideas on these topics are at odds with the majority of published papers and Internet sources on geodiversity. We argue that geodiversity as a concept has real value and that (a) the planet’s geodiversity occurs at all scales from global downwards, (b) it deserves an absolutely central place in any sequence of ‘Gs’ since it is the backbone of international and national geoheritage and geoconservation strategies, and the basis for geoheritage assessments, and (c) that as well as underpinning biodiversity, geodiversity is the source of many other geosystem services, including geotourism. Finally, a revised proposal for the relationship between geology, geodiversity, geoheritage, geoconservation and other ‘Gs’ is presented.