The Nordic Volcanological Institute: understanding volcanoes at spreading centres

The Nordic countries (known as 'Norden') are not immediately associated with volcanoes: Norway with folded mountains cut by fjords and its offshore oil and gas deposits, Sweden and Finland by the western part of the Baltic shield, a huge area of Precambrian rocks, of which gneisses form a large part, and Denmark, a country of Mesozoic and Cenozoic rocks, where glacial, superficial deposits are of major importance. But Norden also includes Iceland, where everyone immediately thinks of volcanoes and glaciers. Clearly volcanological research would be expected to be a major priority for the Icelandic nation. However, in the other Nordic countries old volcanic and other igneous rocks play a significant role, comprising a large part of the Precambrian and Caledonian terrains and being a key to many of the commercial mineral deposits which play a major role in the economies of Norway, Sweden and Finland. Even Denmark, a country of sedimentary rocks has an impressive sequence of Paleogene volcanic ashes and the Faeroe Islands, made up almost entirely of basalts, are part of Denmark.     

A process framework for coastal zone management in Tanzania

A process framework is described to address socio-economic issues related to coastal zone management, specifically as it applies to the mitigation of impacts due to the establishment of marine protected areas (MPAs). Analysis of the existing social environment in Tanzania, including social capital, vulnerable groups and livelihood components, was undertaken to allow for the identification of critical issues and challenges. The developed process framework is a guidance document for decision-makers to incorporate the interests and needs of affected stakeholders. This safeguard commits to a consultative process with clear channels of communication, established grievance procedures, and monitoring and evaluation activities for affected communities.     

Messengers from the deep – the mantle under the North Atlantic area

Only the very outermost skin of the Earth will ever be directly accessible with the deepest boreholes extending to only about 10 km. This is negligible compared to the distance to the core of around 6000 km, or even the base of the crust, which is tens of kilometres thick under the continents. Nevertheless, we can gain information about the deep regions of the earth by two means: geophysics, and situations where deep rocks have become exposed at the surface.     

Deep secrets of a sun and surf resort in the Atlantic

The majority of igneous rocks can be classified into either the basalt–gabbro group, or the rhyolite–granite group. However, there also exist a wide range of rocks whose composition lies outside these broad groupings, some of which are compositionally extreme and contain many rare minerals, sometimes as essential components. Petrologists have always interested themselves in these unusual rock types, just as collectors always value rare items over the commonplace. Many of these unusual rock types have been given weird and wonderful names, driving non‐petrologists to distraction, although a more scientific system of nomenclature has yet to receive general acclaim. The giving of a plethora of names to igneous rocks was largely a phenomenon of the early years of petrology in the late nineteenth and early twentieth century and many will be surprised to learn that new names are still being coined as with the, as yet unauthorized, bermudite, not surprisingly, called after the island of Bermuda.     

Integrated Futures for Europe’s Mountain Regions: Reconciling Biodiversity Conservation and Human Livelihoods

Introduction Europe's mountains cover nearly half of the continent's area (Price et al. 2004) and land cover varies significantly (European Commission 2004). In most massifs, except for Sicily, southern Greece, and the British Isles, forest cover is dominant. In northern Europe, grassland is proportionately more important, and much of the mountains of the British Isles is covered by moorland. In central and southern Europe, arable land is of far greater importance than grassland, with Med…     

Multiple-impact mechanisms on Venus and other solid planets and satellites

While atmospheric pressure can be considered a major multiple impact mechanism on Venus, probable mechanisms for multiple impacts on other solid planetary bodies cannot be isolated with certainty.     

Revisiting the compositions and volatile contents of olivine-hosted melt inclusions from the Mount Shasta region: implications for the formation of high-Mg andesites

Primitive chemical characteristics of high-Mg andesites (HMA) suggest equilibration with mantle wedge peridotite, and they may form through either shallow, wet partial melting of the mantle or re-equilibration of slab melts migrating through the wedge. We have re-examined a well-studied example of HMA from near Mt. Shasta, CA, because petrographic evidence for magma mixing has stimulated a recent debate over whether HMA magmas have a mantle origin. We examined naturally quenched, glassy, olivine-hosted (Fo_87–94) melt inclusions from this locality and analyzed the samples by FTIR, LA-ICPMS, and electron probe. Compositions (uncorrected for post-entrapment modification) are highly variable and can be divided into high-CaO (>10 wt%) melts only found in Fo > 91 olivines and low-CaO (<10 wt%) melts in Fo 87–94 olivine hosts. There is evidence for extensive post-entrapment modification in many inclusions. High-CaO inclusions experienced 1.4–3.5 wt% FeO^T loss through diffusive re-equilibration with the host olivine and 13–28 wt% post-entrapment olivine crystallization. Low-CaO inclusions experienced 1–16 wt% olivine crystallization with <2 wt% FeO^T loss experienced by inclusions in Fo > 90 olivines. Restored low-CaO melt inclusions are HMAs (57–61 wt% SiO₂; 4.9–10.9 wt% MgO), whereas high-CaO inclusions are primitive basaltic andesites (PBA) (51–56 wt% SiO₂; 9.8–15.1 wt% MgO). HMA and PBA inclusions have distinct trace element characteristics. Importantly, both types of inclusions are volatile-rich, with maximum values in HMA and PBA melt inclusions of 3.5 and 5.6 wt% H₂O, 830 and 2,900 ppm S, 1,590 and 2,580 ppm Cl, and 500 and 820 ppm CO₂, respectively. PBA melts are comparable to experimental hydrous melts in equilibrium with harzburgite. Two-component mixing between PBA and dacitic magma (59:41) is able to produce a primitive HMA composition, but the predicted mixture shows some small but significant major and trace element discrepancies from published whole-rock analyses from the Shasta locality. An alternative model that involves incorporation of xenocrysts (high-Mg olivine from PBA and pyroxenes from dacite) into a primary (mantle-derived) HMA magma can explain the phenocryst and melt inclusion compositions but is difficult to evaluate quantitatively because of the complex crystal populations. Our results suggest that a spectrum of mantle-derived melts, including both PBA and HMA, may be produced beneath the Shasta region. Compositional similarities between Shasta parental melts and boninites imply similar magma generation processes related to the presence of refractory harzburgite in the shallow mantle.     

A New Face for The Cartographic Journal

Abstract

The logic behind the placement of names on maps is investigated as part of a study, the object of which is the automation of map lettering. After describing the basic principles the author illustrates his solution.     

ANOMALOUS WET AND DRY SPELLS IN THE CENTRAL UNITED STATES, 1931–75

The Palmer Index (PI) was employed to compare anomalous dry spells with anomalous wet spells for 76 climatic divisions in the central United States. Comparisons were made in terms of the frequency, severity and persistence of wet and dry climatic episodes for the period 1931–75. The results indicated more frequent dry anomalies in the southwest (New Mexico and west Texas) portion of the study area and more frequent wet anomalies in the northeast (Illinois and Iowa). Not surprisingly, these are the most arid and most humid portions respectively. The results of the analysis for persistence were less clear. Typically dry anomalies lasted longer than wet anomalies, especially as the minimum length was increased. This was especially apparent when comparing the very longest dry spell with the very longest wet spell during the 45-year study period. Thus there are more but shorter wet spells and less frequent, but typically longer lasting dry spells. This final relationship posits the question of feedback processes between surface soil moisture and the persistence of atmospheric precipitation anomalies. [Key Words: Palmer Index, drought, moisture anomalies, wet spells, dry spells.]     

Sphene (titanite)

Few people have heard of the mineral sphene (also called titanite), but it is nevertheless extremely widespread, occurring in most common rocks. It can be useful to the Earth scientist as it contains information on the timing, temperature and pressure of formation of many common rocks. It is also a source of titanium—and can sometimes be used as a gemstone.