Showing papers by "University of Iceland published in 1983"
TL;DR: In this paper, a new CO2 geothermometer is proposed which is considered to be useful in estimating underground temperatures in fumarolic geothermal fields, its application involves analysis of CO2 concentrations in the fumarole steam.
450 citations
TL;DR: The major element chemistry of Icelandic geothermal waters is predictable provided two parameters are known as mentioned in this paper, namely temperature and the mobility of chloride, which is known to have a significant effect on water chemistry.
294 citations
TL;DR: In this paper, the thermal structure of nonmagnetic neutron star envelopes is determined by the single parameter T(s to the 4th/g(s), where T is the effective surface temperature and g(s) the surface gravity of the star.
Abstract: The envelopes of nonmagnetic neutron stars are studied using the best available opacities and equation of state. The general relativistic equations of the structure and evolution of nonmagnetic neutron stars are discussed, and it is shown that they can be reduced to a single equation for calculating the thermal structure of neutron star envelopes. The physical input needed to solve the thermal structure equation is investigated and the numerical results of envelope model calculations are presented. It is shown that the thermal structure of neutron star envelopes is determined by the single parameter T(s) to the 4th/g(s), where T(s) is the effective surface temperature and g(s) the surface gravity of the star. This result is used to derive a number of other scaling relations, and the effects of general relativity on the envelope thermal structure are examined in detail. The results of a sensitivity analysis of the regional opacity needed to obtain a reliable relationship between the temperatures of the inner and outer boundaries of the envelope is presented.
287 citations
TL;DR: In this article, it is suggested that primary 3He/4He ratios may have been modified by incorporation of radiogenic helium developed within the Icelandic crust to impose a larger range of 3he/4he ratios on the erupted products than was actually inherited from the mantle beneath Iceland.
233 citations
TL;DR: In this paper, the authors focus on assessing the overall water composition with respect to mineral equilibria, rather than attempting to distinguish geothermal waters from shallow waters by a classification involving the relative abundance of major anions and major cations.
185 citations
TL;DR: The sixteenth eruption of Hekla since 1104 began on August 17th, 1980, after the shortest repose period on record, only ten years as mentioned in this paper, and produced a total of 120 million m3 of lava and about 60 million m 3 of airborne tephra.
Abstract: The sixteenth eruption of Hekla since 1104 began on August 17th, 1980, after the shortest repose period on record, only ten years. The eruption started with a plinian phase and simultaneously lava issued at high rate from a fissure that runs along the Hekla volcanic ridge. The production rate declined rapidly after the first day and the eruption stopped on August 20th. A total of 120 million m3 of lava and about 60 million m3 of airborne tephra were produced during this phase of the activity. In the following seven months steam emissions were observed on the volcano. Activity was renewed on April 9th 1981, and during the following week additional 30 million m3 of lava flowed from a summit crater and crater rows on the north slope.
88 citations
TL;DR: Difference in substrate affinity can account for the inhibition of methanogenesis from H2 and CO2 in sulfate-rich ecosystems (mainly saltwater marshes), where the H2 concentration is well below 5 μM.
Abstract: The apparent Ks values for H2 of several phylogenetically distant strains of both methanogenic bacteria and sulfate-reducing bacteria were measured. The sulfate reducers had Ks values of about 2 μM whereas the Ks values of the methanogens were 6–20 μM. This indicates that probably all sulfate-reducing bacteria have a higher substrate affinity for H2 than the methanogenic bacteria. Difference in substrate affinity can thus account for the inhibition of methanogenesis from H2 and CO2 in sulfate-rich ecosystems (mainly saltwater marshes), where the H2 concentration is well below 5 μM. Possible explanations for this general phenomenon are discussed.
61 citations
TL;DR: The growth range in nature of bacteria belonging to the genus Thermus was investigated by sampling 55 different hot springs in Iceland and found to agree well with the overall distribution in individual springs.
Abstract: The growth range in nature of bacteria belonging to the genus Thermus was investigated by sampling 55 different hot springs in Iceland. The springs ranged in temperature from 32 to 99 degrees C, and in pH from 2.1 to 10.1. Viable counts of Thermus spp. ranging from 10 to 10 CFU/100 ml of spring water were found in 27 of the springs sampled. The temperature range for these bacteria was found to be 55 to 85 degrees C, and the pH range was from about 6.5 to above 10. Thermus spp. were found in springs containing up to 1 mM dissolved sulfide and having conductivity up to 2,000 muS/cm. The distribution of Thermus spp. in a hot spring thermal gradient was also investigated and found to agree well with the overall distribution in individual springs.
57 citations
TL;DR: In this article, it is suggested that chromian spinels and olivine nucleates heterogeneously, dependent on growth of olivines phenocrysts, which may be the prime reason for the non-equilibrium precipitation of included spinels.
Abstract: Crystallization of spinel minerals in transitional and alkali basalts from Iceland can be related to the FeO, MgO, TiO2 and Cr contents of the coexisting melt. Chromian spinel occurs in glasses in which TiO2 is less than 2.8 wt.% and the weight ratio FeO/MgO is less than 2.0, whereas titanomagnetite occurs when the same parameters are greater than 4 wt.% and 2.7, respectively. In addition, chromian spinel only occurs in basalts with Cr greater than 200 ppm. It is suggested that chromian spinel crystallizes, together with olivine, from liquids with olivine liquidus temperatures ranging from above 1,200° C to approximately 1,150° C. A discontinuity in spinel crystallization follows until below 1,100° C, where titanomagnetite starts to crystallize. Compositional variations in chromian spinel attached to, or included, in homogeneous olivine phenocrysts, however, cannot be related to equilibrium relations. Textural relations suggest homogeneous nucleation for titanomagnetite, whereas chromian spinel nucleates heterogeneously, dependent on growth of olivine phenocrysts. The composition of chromian spinels cannot in detail be related to physical and compositional parameters of the average melt, but may be related to local compositional relations in the melt adjacent to growing crystals. Such compositional variation around growing olivine crystals may be the prime reason for the non-equilibrium precipitation of included chromian spinels.
49 citations
01 Jan 1983
TL;DR: In this paper, wide-angle reflection surveys across the active volcanic zones and the adjacent plateau basalts have given a detailed picture of the crust, and the cross sections bear a certain resemblance to the crustal structure deduced from geological observations in Eastern Iceland.
Abstract: Except for greater thickness and more pronounced lateral variations the Icelandic crust is very similar to the crust beneath the Reykjanes Ridge. Layer 3 can be traced without interruption from the 10 m.y. old oceanic crust on the southeastern flank of the ridge through Iceland. It exists also beneath the eastern neo- volcanic zone which is supposed to be the present spreading axis. Wide-angle reflection surveys across the active volcanic zones and the adjacent plateau basalts have given a detailed picture of the crust. The cross sections bear a certain resemblance to the crustal structure deduced from geological observations in Eastern Iceland. The dip of refractors and reflectors toward the axial zone and the absence of reflecting horizons below 8 km depth in the central part of the zone, support the predictions of models of crustal accretion mechanism. The episode of crustal rifting in the NE Iceland axial zone, which started in 1975 and still continues, has demonstrated how intimately the rifting is related to episodic magmatic processes at central volcanoes.
49 citations
TL;DR: Icelanders proved to be larger than in Europeans generally, being exceeded only by Australian Aborigines, some American Indian populations, and American Negroes in comparison with Ohio Caucasians of Northwest European origin.
Abstract: Mesiodistal and buccolingual crown diameters were measured from casts of 1010 dentitions of schoolchildren from Northeast Iceland. Their teeth proved to be larger than in Europeans generally, being exceeded only by Australian Aborigines, some American Indian populations, and American Negroes. In comparison with Ohio Caucasians of Northwest European origin Icelanders showed clearly larger dimensions, less sexual dimorphism, and a different pattern of dimorphism. Crown indices were also distinctly different in Icelanders and Ohio Caucasians
TL;DR: In this paper, the authors show that these measurements can be interpreted in terms of inflating magma reservoirs with a centre at ∼8 km depth below the volcano, over a period of 10 months, the volume of the inflation amounted to 55 × 106 m3.
Abstract: Hekla, situated on the western boundary of the eastern volcanic zone in South Iceland, is one of the most active volcanoes in Iceland having erupted 16 times since 1104. Repeated electronic distance measurements since its eruption in 1980–81 show significant changes in crustal movement in the aftermath of the eruption. Such movement on and around volcanoes can be used to monitor movement of magma within and below volcanoes1,3. We show here that these measurements can be interpreted in terms of inflating magma reservoirs with a centre at ∼8 km depth below the volcano. Over a period of 10 months, the volume of the inflation amounted to 55 × 106 m3.
TL;DR: In this article, Icelandic and British subjects were compared on the personality factors, using reduced scales comprising only items both scoring keys shared; Icelandic subjects scored lower on all factors, although not always at a statistically significant level.
Abstract: 577 men and 567 women were given the 101-item version of the Eysenck Personality Questionnaire, translated into Icelandic. Although some items were inappropriate for use in Iceland, a viable scoring key was suggested and all reliabilities, except perhaps for Psychoticism, were satisfactory. Indices of factor comparison showed very clearly identical factors in both countries. Icelandic and British subjects were compared on the personality factors, using reduced scales comprising only items both scoring keys shared; Icelandic subjects scored lower on all factors, although not always at a statistically significant level.
TL;DR: In this article, it was concluded that these waters represent meteoric waters which have seeped to variable depths into the bedrock of the Snaefellsnes Peninsula of western Iceland.
TL;DR: An inverse relationship between arachidonic acid content ofosphatidylcholine and phosphatidylethanolamine was observed, and the cardiolipin fraction retained its high amount of linoleic acid and the fatty acid composition of the triacylglycerol was not altered, although the amount was significantly decreased.
TL;DR: In this article, a bimodality in size and composition of plagioclase and olivine phenocrysts can be explained in the light of experimental investigations of the effect of pressure on phase relations.
Abstract: Basaltic glasses from the three alkalic areas of Iceland (Snaefellsnes Volcanic Zone, Sudurland Volcanic Zone and Vestmannaeyjar Volcanic Area) contain plagioclase, olivine, clinopyroxene, chromian spinel and titanomagnetite as phenocryst phases. The glasses are hypersthene to nepheline normative alkali basaltic with FeO/ MgO ratios between 1.4–4.7. Olivine ranges in composition from Fo90 to Fo55, plagioclase from An90 to An50 and clinopyroxene from En45Fs10Wo45 to En40Fs17Wo43. Clinopyroxene reveals systematic Ti:Al metastable crystallization trends related to the composition of the enclosing glass. Two types of phenocryst are present in most glasses and show a bimodality in size and composition. Microphenocryst phases are those most likely to have crystallized from the enclosing glass, while macrophenocrysts may have crystallized from a liquid of slightly less evolved composition. The glasses show complex phenocryst-glass relations which can be related to a polybaric effect. The normative glass compositions are related to 2-phase cotectic surfaces in the basalt tetrahedron and define the position of the 3-phase cotectic line. In general with increasing FeO/MgO in the glass the phenocryst assemblages vary from clinopyroxene, olivine and plagioclase along a clinopyroxene-olivine surface to olivine and plagioclase along an olivine-plagioclase surface. The normative glass compositions show a deflection from clinopyroxene-bearing to clinopyroxene-free glasses. The appearance of plagioclase together with clinopyroxene and olivine can be explained in the light of experimental investigations of the effect of pressure on phase relations. The major element variation of the glasses is interpreted as representing mantle derived magma batches of primary liquids, modified to some degree by high (6 kbar) and intermediate to low pressure (below 3 kbar) crystal fractionation towards equilibrium phase relations during ascent and residence in crustal magma chambers. The observed deflection in normative compositions of the glasses marks the position of the high pressure 3-phase cotectic line. The bimodality in size and composition of plagioclase and olivine phenocrysts can be related to high pressure crystal fractionation in the melt. The Fe-Ti basalt glasses from Sudurland are believed to be quenched high pressure compositions.
TL;DR: The majority of the volcanic activity in Iceland occurs on both rift zones and non-rifting zones as discussed by the authors, and the majority of volcanic material is of the primitive tholeiites (MORB) series.
Abstract: The volcanism in Iceland occurs on both rift zones and non-rifting zones. The rift zone volcanism produces rock suites of the tholeiitic series, ranging from primitive tholeiites (MORB) to highly silicic rocks. The non-rifting volcanic zones produce rock suites of transitional to mildly alkaline or even calc-alkaline composition, the basalts typically being FETI-basalts. Over 50 per cent of the rift zone production in Iceland is of the primitive MORB-type. The relative amount of the evolved rock types, as well as the total volcanic production increases inland along the rift zones. The rock types of the Icelandic rift zones are identical to those of the submerged oceanic rift zones, but the Icelandic production is somewhat offset towards a more voluminous evolved end. The skewness in volume relations of rock types, as compared to the oceanic rifts in general, is mainly caused by the products of the non-rifting volcanic zones of Iceland and only to a small degree by the rift zone products.
TL;DR: The observed alterations in fatty acid composition of heart muscle phospholipids resemble changes induced by repeated administration of norepinephrine and subsequent recovery.
TL;DR: In this paper, a sociological explanation for the ideology of the skipper effect and how the ideology developed in response to historical changes in the social relations of production in fishing from the 19th century as labor and fish both became commodities, as Iceland gained independence from Denmark, and as new fishing technology developed.
Abstract: There are two folk models to explain differential fishing success in Iceland. One applies to the short term and is based on material factors; the other refers to the long term of seasons and careers and centers on the personal qualities of skippers, or the skipper effect. We show first that the skipper effect cannot account for differential fishing success. We then develop a sociological explanation for the ideology of the skipper effect and show how the ideology developed in response to historical changes in the social relations of production in fishing from the 19th century as labor and fish both became commodities, as Iceland gained independence from Denmark, and as new fishing technology developed. Finally, we describe the earlier conceptual scheme of fishing, which entailed foremen rather than skippers, and show how the role of skipper became elaborated as fishing developed into an autonomous economic field separate from other aspects of peasant production. [fishing, folk models, Iceland, social relations of production, history]
01 Jan 1983
TL;DR: In this article, the authors present a polar stereographic chart at a scale of 1: 2 000 000 on which most of the available data are displayed in the form of residual anomaly profiles along track.
Abstract: During the past two decades many shipborne and airborne magnetic surveys have been carried out in the vicinity of Iceland, but no comprehensive compilation has been available. As an accompaniment to the present volume we present a polar stereographic chart at a scale of 1: 2 000 000 on which most of the available data are displayed in the form of residual anomaly profiles along track. The chart has been colored to indicate the continuity of positive and negative anomalies. Bathymetric contours in fathoms (Gronlie and Talwani, 1979) are also shown.
TL;DR: Results indicate that "farmer's lung" in man and "haysickness" in horses are of the same origin, however, further studies are necessary to substantiate the diagnostic or prognostic value of these precipitin tests in equine practice.
Abstract: Blood samples were taken from 18 healthy horses (Group A), 15 horses clinically diagnosed to have "haysickness" ("farmer's lung") (Group B), 10 closely related horses (Group C) and 14 inbred horses (Group D). Precipitins in sera were measured by double gel diffusion test against Micropolyspora faeni, Thermoactinomyces vulgaris, Aspergillus fumigatus, Alternaria, Penicillium and Rhizopus species. In Group A, all the horses were precipitin negative except one with a faint reaction to Rhizopus species. In Group B all had precipitin against M faeni. One horse also had precipitins against Rhizopus species and another against A fumigatus. In Group C, seven of the 10 horses had precipitins against M faeni. Of these, five had a history of respiratory signs, but two horses with a faint reaction had no such history. In Group D, four out of 14 horses had positive precipitin tests against M faeni. Of these four horses, three also had a faint reaction to A fumigatus and one a faint reaction to Alternaria species. All were asymptomatic. These results indicate that "farmer's lung" in man and "haysickness" in horses are of the same origin. However, further studies are necessary to substantiate the diagnostic or prognostic value of these precipitin tests in equine practice. The question of whether hereditary factors play a role in causing this disease also warrants further studies.
TL;DR: The hypothesis that a part of LG II (e-Es) shares homologies with mouse chromosome 8 is thus confirmed, as the murine homologue of GOTM is located within the cluster of esterase loci on chromosome 8.
Abstract: Three previously described electrophoretic phenotypes of mitochondrial glutamate oxaloacetate transaminase (GOTM) in horse leukocytes are shown to be controlled by two codominant alleles at a single autosomal locus. The GOTM locus is linked to the serum esterase locus (Es), as no recombination between these loci was observed among 16 informative offspring in one sire family. The results assign GOTM to equine linkage group (LG) II. The hypothesis that a part of LG II (e-Es) shares homologies with mouse chromosome 8 is thus confirmed, as the murine homologue of GOTM is located within the cluster of esterase loci on chromosome 8. The assumed homology also involves rabbit LG VI, rat LG V, and human chromosome 16. The observation is a striking example of the conservation of linkage relationships between mammalian species.
TL;DR: Using a mouse model of oral candidosis, differences in colonization and infection between two strains of C. albicans were demonstrated.
TL;DR: Two female patients are described who were, following difficulties in blood cross matching, found to be homozygous for the rare Rhesus --D-- gene complex, and had formed Rh antibodies, one provoked by transfusions and the other by three pregnancies.
TL;DR: Fluorine in 22 international reference samples has been determined with an ion selective electrode following fusion with a Na2bCO3-ZnO mixture, the results presented are means of fluoride determinations from a standard calibration curve and from the method of standard addition as discussed by the authors.
Abstract: Fluorine in 22 international reference samples has been determined with an ion selective electrode following fusion with a Na2bCO3-ZnO mixture To eliminate the effect of fluorine complexes in the solutions, the results presented are means of fluoride determinations from a standard calibration curve and from the method of standard addition Together with these new determinations an updated compilation of USGS-I reference samples is presented
01 Jan 1983
TL;DR: The purpose of this study was to examine the fatty acid composition and content of phospholipids, and free fatty acids in human heart muscle samples obtained at autopsy from people that died suddenly in accidents and from people That died suddenly from heart disease, with or without coronary artery disease.
Abstract: The purpose of this study was to examine the fatty acid composition and content of phospholipids, and free fatty acids in human heart muscle samples obtained at autopsy from people that died suddenly in accidents and from people that died suddenly from heart disease, with or without coronary artery disease.
TL;DR: In this article, a method for determining the sensitivity of certain types of calculations to uncertainties in the input physics or model parameters is given for problems that involve solutions to coupled, ordinary differential equations.
Abstract: A method is given for determining the sensitivity of certain types of calculations to the uncertainties in the input physics or model parameters; this method is applicable to problems that involve solutions to coupled, ordinary differential equations. In particular the sensitivity of calculations of the thermal structure of neutron star envelopes to uncertainties in the opacity and equation of state is examined. It is found that the uncertainties in the relationship between the surface and interior temperatures of a neutron star are due almost entirely to the imprecision in the values of the conductive opacity in the region where the ions form a liquid; here the conductive opacity is, for the most part, due to the scattering of electrons from ions.
TL;DR: In this paper, the components of the magnetic field caused by the edge of a large steel plate are measured and compared quantitatively to theoretical derivations, which is useful in geophysics instruction.
Abstract: Measurement of the components of the magnetic field caused by the edge of a large steel plate, provides a simple introduction to the study of potential fields. Results can be compared quantitatively to theoretical derivations. This experiment is particularly useful in geophysics instruction.