Book reviews     

W. Manshard  W. B. Morgan  Philip Tilley  Atsushi Otomo  G. Kunkel  W. Lauer  K. Kunkel  David Rickard  Joan M. Kenworthy  A. Grotewold  C. Chr Liebmann 《GeoJournal》1981,5(3):291-296

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Atmospheric noble gases in volcanic glasses from the southern Lau Basin: origin from the subducting slab?     

Wolfgang Bach  Samuel Niedermann 《Earth and Planetary Science Letters》1998,160(3-4):297-309

Noble gas concentrations and isotopic compositions have been determined for four submarine volcanic glasses from the Valu Fa Ridge (VFR) in the southern Lau Basin. The samples are the least differentiated ones from this area, and they display enrichments in fluid-mobile elements similar to the nearby island arc. ³He/⁴He ratios are slightly below average MORB (6.8–7.8 times atmospheric), whereas Ne, Ar, Kr, and Xe have isotopic compositions very similar to air. Together with previously published data from the Valu Fa Ridge and other spreading segments in the Lau Basin, our data show a systematic latitudinal variation of increasing Ne, Ar, Kr, and Xe abundances from north to south as well as Ne and Ar isotopic compositions changing from MORB-like to atmosphere-like in the same direction. Moreover, isotopic compositions and noble gas abundances of the lavas correlate strongly with Ba/Nb ratios and H₂O concentrations. Based on these observations and mass balance arguments, we propose that the atmospheric noble gases come from the subducting oceanic crust and are not due to shallow contamination with air dissolved in seawater or assimilation of old crust. Our data suggest that the noble gases released from the subducting slab are atmospheric and thus contain little or no solar He and Ne. In addition to the fact that ratios of He to heavy noble gases are small in aged ocean crust, He has possibly fractionated from the other noble gases due to its higher diffusivity, and thus He transport from the subducting slab into the mantle wedge is probably insignificant. We propose that the ³He/⁴He ratios lower than MORB observed in the VFR lavas result from radiogenic ingrowth of He in a highly depleted, and hence degassed, mantle wedge after the enrichment of U and Th released from the downgoing slab.  相似文献   

Anomalously nucleogenic neon in North Chile Ridge basalt glasses suggesting a previously degassed mantle source     

Samuel Niedermann  Wolfgang Bach 《Earth and Planetary Science Letters》1998,160(3-4):447-462

Fresh basalt glasses from the North Chile Ridge (NCR) in the southeastern Pacific have Ne isotopic compositions distinctly different from typical mid-ocean ridge basalts (MORB). In a three-isotope plot of ²⁰Ne/²²Ne vs. ²¹Ne/²²Ne, the NCR data define a correlation line with a slope smaller than that of the MORB correlation line, i.e. their Ne composition is more nucleogenic than that of MORB. ³He/⁴He ratios are slightly lower than the MORB average, whereas in a few stepwise heating fractions very high ⁴⁰Ar/³⁶Ar ratios up to 28,000 are found. One model to explain the data assumes contamination of the NCR mantle source by material from the continental or oceanic crust, but in addition to difficulties with quantitatively reconciling the noble gas patterns with such a model it seems unable to account for some geochemical characteristics of NCR basalts reported earlier [Bach et al., Earth Planet. Sci. Lett. 142 (1996) 223–240], such as depletions in highly incompatible elements and unradiogenic Sr isotope compositions. Therefore we favor the scenario of a mantle source which was depleted and degassed previously, possibly as a residue from mantle melting beneath the southern East Pacific Rise that was transported to the NCR and melted again. The time during which such a depleted reservoir would have to be separated from the MORB mantle is estimated at 10–100 Ma based on U/Th–Ne systematics, in reasonable agreement with the time scale deduced from the formation history of the NCR and the temporal evolution of the southeast Pacific.  相似文献   

The partial molal volume of silicic acid in 0.725 m NaCl     

Iver W Duedall  Ramesh Dayal  Joan D Willey 《Geochimica et cosmochimica acta》1976,40(10):1185-1189

The partial molal volume ($\text{V}\text{?}$) of silicic acid in 0.725 m NaCl at 20°C has been calculated from (1) direct volume changes due to the dissolution of anhydrous sodium silicate and (2) some literature values for the partial molal volumes of NaOH and water. , unconnected for electrostriction effects, was found to be 53 ± 2 ml mole^?1. , corrected for volume changes due to solvent electrostriction by charged Si species, was estimated to be in the range 58–62 ml mole^?1; this range is 7–11 ml mole^?1 greater than the calculated from Willey's (Mar. Chem. 2, 239–250, 1974) solubility data obtained from the dissolution, in seawater, of amorphous silica subjected to hydrostatic pressure. Our does, however, agree within experimental error with the calculated from Jones and Pytkowicz's (Bull. Soc. Roy. Sci. Liege 42, 118–120, 1973) data for the solubility of amorphous silica in seawater at high pressure and is nearly in agreement with Willey's (Ph.D. thesis, Dalhousie University, 1975) solubility data for amorphous silica in 0.6 m NaCl.  相似文献   

Postglacial climates inferred from a lake at treeline,southwest Yukon Territory,Canada     

Joan Bunbury  Konrad Gajewski 《Quaternary Science Reviews》2009,28(3-4):354-369

Pollen, chironomid, and ostracode records from a lake located at alpine treeline provide regional paleoclimate reconstructions from the southwest Yukon Territory, Canada. The pollen spectra indicate herbaceous tundra existed on the landscape from 13.6–11 ka followed by birch shrub tundra until 10 ka. Although Picea pollen dominated the assemblages after 10 ka, low pollen accumulation rates and Picea percentages indicate minimal treeline movement through the Holocene. Chironomid accumulation rates provide evidence of millennial-scale climate variability, and the chironomid community responded to rapid climate changes. Ostracodes were found in the late glacial and early Holocene, but disappeared due to chemical changes of the lake associated with changes in vegetation on the landscape. Inferred mean July air temperature, total annual precipitation, and water depth indicate a long-term cooling with increasing moisture from the late glacial through the Holocene. During the Younger Dryas (12.9–11.2 ka), cold and dry conditions prevailed. The early and mid-Holocene were warm and dry, with cool, wet conditions after 4 ka, and warm, dry conditions since the end of the Little Ice Age.  相似文献   

Spatial variability of snowmelt timing from AMSR‐E and SSM/I passive microwave sensors,Pelly River,Yukon Territory,Canada     

Joan M. Ramage  Jeremy D. Apgar  Rose A. McKenney  Wade Hanna 《水文研究》2007,21(12):1548-1560

Spring snow melt run‐off in high latitude and snow‐dominated drainage basins is generally the most significant annual hydrological event. Melt timing, duration, and flow magnitude are highly variable and influence regional climate, geomorphology, and hydrology. Arctic and sub‐arctic regions have sparse long‐term ground observations and these snow‐dominated hydrologic regimes are sensitive to the rapidly warming climate trends that characterize much of the northern latitudes. Passive microwave brightness temperatures are sensitive to changes in the liquid water content of the snow pack and make it possible to detect incipient melt, diurnal melt‐refreeze cycles, and the approximate end of snow cover on the ground over large regions. Special Sensor Microwave Imager (SSM/I) and Advanced Microwave Scanning Radiometer for EOS (AMSR‐E) passive microwave brightness temperatures (T_b) and diurnal amplitude variations (DAV) are used to investigate the spatial variability of snowmelt onset timing (in two stages, ‘DAV onset’ and ‘melt onset’) and duration for a complex sub‐arctic landscape during 2005. The satellites are sensitive to small percentages of liquid water, and therefore represent ‘incipient melt’, a condition somewhat earlier than a traditional definition of a melting snowpack. Incipient melt dates and duration are compared to topography, land cover, and hydrology to investigate the strength and significance of melt timing in heterogeneous landscapes in the Pelly River, a major tributary to the Yukon River. Microwave‐derived melt onset in this region in 2005 occurred from late February to late April. Upland areas melt 1–2 weeks later than lowland areas and have shorter transition periods. Melt timing and duration appear to be influenced by pixel elevation, aspect, and uniformity as well as other factors such as weather and snow mass distribution. The end of the transition season is uniform across sensors and across the basin in spite of a wide variety of pixel characteristics. Copyright © 2007 John Wiley & Sons, Ltd.  相似文献   

Cyclic Evolution of Coronal Fields from a Coupled Dynamo Potential-Field Source-Surface Model     

Mausumi Dikpati  Akshaya Suresh  Joan Burkepile 《Solar physics》2016,291(2):339-355

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Occurrence and fate of polycyclic aromatic hydrocarbons in the coastal surface microlayer   总被引：2，自引：0，他引：2  

Guitart C  García-Flor N  Bayona JM  Albaigés J 《Marine pollution bulletin》2007,54(2):186-194

Polycyclic aromatic hydrocarbons (PAHs) were measured in the coastal sea surface microlayer (SML), the sub-surface waters (SSW) and the overlying atmosphere in order to investigate the influence of the SML on contaminant enrichment and air-sea exchange. Samples were collected at two contrasting locations of the NW Mediterranean, one urban influenced (off Barcelona, Spain) and another comparatively clean (off Banyuls-sur-Mer, France). Statistical data analysis confirmed the accumulation of PAHs in the SML with respect to the SSW (20.3+/-9.1 vs. 13.1+/-10.0 ng L(-1) in the dissolved phase; 709+/-207 vs. 158+/-111 ng g(-1) in the particulate phase). This accumulation was higher at the contaminated location (Barcelona station) compared with the more pristine one, with PAH enrichments 1.5 and 4.5 times higher for the dissolved and particulate phases, respectively, indicating that the enrichment of PAHs in the SML is dominated by particle transport processes.  相似文献   

A digitized global flood inventory (1998–2008): compilation and preliminary results     

Pradeep Adhikari  Yang Hong  Kimberly R. Douglas  Dalia Bach Kirschbaum  Jonathan Gourley  Robert Adler  G. Robert Brakenridge 《Natural Hazards》2010,55(2):405-422

Floods have profound impacts on populations worldwide in terms of both loss of life and property. A global inventory of floods is an important tool for quantifying the spatial and temporal distribution of floods and for evaluating global flood prediction models. Several global hazard inventories currently exist; however, their utility for spatiotemporal analysis of global floods is limited. The existing flood catalogs either fail to record the geospatial area over which the flood impacted or restrict the types of flood events included in the database according to a set of criteria, limiting the scope of the inventory. To improve upon existing databases, and make it more comprehensive, we have compiled a digitized Global Flood Inventory (GFI) for the period 1998–2008 which also geo-references each flood event by latitude and longitude. This technical report presents the methodology used to compile the GFI and preliminary findings on the spatial and temporal distributions of the flooding events that are contained in the inventory.  相似文献   

Geophysical exploration on the subsurface geology of La Garrotxa monogenetic volcanic field (NE Iberian Peninsula)     

Xavier Bolós  Stéphanie Barde-Cabusson  Dario Pedrazzi  Joan Martí  Albert Casas  Raúl Lovera  Daniel Nadal-Sala 《International Journal of Earth Sciences》2014,103(8):2255-2269

We applied self-potential (SP) and electrical resistivity tomography (ERT) to the exploration of the uppermost part of the substrate geology and shallow structure of La Garrotxa monogenetic volcanic field, part of the European Neogene–Quaternary volcanic province. The aim of the study was to improve knowledge of the shallowest part of the feeding system of these monogenetic volcanoes and of its relationship with the subsurface geology. This study complements previous geophysical studies carried out at a less detailed scale and aimed at identifying deeper structures, and together will constitute the basis to establish volcanic susceptibility in La Garrotxa. SP study complemented previous smaller-scale studies and targeted key areas where ERT could be conducted. The main new results include the generation of resistivity models identifying dykes and faults associated with several monogenetic cones. The combined results confirm that shallow tectonics controlling the distribution of the foci of eruptive activity in this volcanic zone mainly correspond to NNW–SSE and accessorily by NNE–SSW Neogene extensional fissures and faults and concretely show the associated magmatic intrusions. These structures coincide with the deeper ones identified in previous studies, and show that previous Alpine tectonic structures played no apparent role in controlling the loci of this volcanism. Moreover, the results obtained show that the changes in eruption dynamics occurring at different vents located at relatively short distances in this volcanic area are controlled by shallow stratigraphical, structural and hydrogeological differences underneath these monogenetic volcanoes.  相似文献