Eearth Discussions最新文献

{"title":"Thermogeodynamic manifestations in the Caucasus and their genesis","authors":"G. Gugunava, J. Kiria, T. Bochorishvili","doi":"10.5194/EED-4-77-2009","DOIUrl":"https://doi.org/10.5194/EED-4-77-2009","url":null,"abstract":"In the work two aspects of thermal character are considered: first of all this is the connection of subduction phenomena with thermal life of the Caucasus on the basis of over interpreted data of magnetotelluric sounding, and secondly, origin of thermostressed condition of the Caucasus and its geological aspects which is manifested in the follow5 ing: 1. in the zones of anomalous thermodisplacements thermofaults should occur (Le Pishon et al., 1977). These thermofaults are in good correlation with deep faults which are distinguished by geological and seismic methods, these thermofaults may be earthquake sources (Spitak, Racha, etc. earthquakes), also may be chan10","PeriodicalId":394654,"journal":{"name":"Eearth Discussions","volume":"56 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2009-09-29","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125929799","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Use of remote sensing and GIS in mapping the environmental sensitivity areas for desertification of Egyptian territory","authors":"A. Gad, I. Lotfy","doi":"10.5194/EED-3-41-2008","DOIUrl":"https://doi.org/10.5194/EED-3-41-2008","url":null,"abstract":"Desertification is defined in the first art of the convention to combat desertification as \"land degradation in arid, semiarid and dry sub-humid areas resulting from climatic variations and human activities\". Its consequence include a set of important processes which are active in arid and semi arid environment, where water is the main limiting factor of land use performance in such ecosystem . Desertification indicators or the groups of associated indicators should be focused on a single process. They should be based on available reliable information sources, including remotely sensed images, topographic data (maps or DEM'S), climate, soils and geological data. The current work aims to map the Environmental Sensitivity Areas (ESA's) to desertification in whole territory of Egypt at a scale of 1:1 000 000. ETM satellite images, geologic and soil maps were used as main sources for calculating the index of Environmental Sensitivity Areas (ESAI) for desertification. The algorism is adopted from MEDALLUS methodology as follows; ESAI = (SQI * CQI * VQI) 1/3 Where SQI is the soil quality index, CQI is the climate quality index and VQI is the vegetation quality index. The SQI is based on rating the parent material, slope, soil texture, and soil depth. The VQI is computed on bases of rating three categories (i.e. erosion protection, drought resistance and plant cover). The CQI is based on the aridity index, derived from values of annual rainfall and potential evapotranspiration. Arc-GIS 9 software was used for the computation and sensitivity maps production. The results show that the soil of the Nile Valley are characterized by a moderate SQI, however the those in the interference zone are low soil quality indexed. The dense vegetation of the valley has raised its VQI to be good, however coastal areas are average and interference zones are low. The maps of ESA's for desertification show that 86.1% of Egyptian territory is classified as very sensitive areas, while 4.3% as Moderately sensitive, and 9.6% as sensitive. It can be concluded that implementing the maps of sensitivity to desertification is rather useful in the arid and semi arid areas as they give more likely quantitative trend for frequency of sensitive areas. The integration of different factors contributing to desertification sensitivity may lead to plan a successful combating. The usage of space data and GIS proved to be suitable tools to rely estimation and to fulfill the needed large computational requirements. They are also useful in visualizing the sensitivity situation of different desertification parameters.","PeriodicalId":394654,"journal":{"name":"Eearth Discussions","volume":"94 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-06-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"128460358","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Zoogeography of the bottom Foraminifera of the West-African coast","authors":"V. Mikhalevich","doi":"10.5194/EED-3-1-2008","DOIUrl":"https://doi.org/10.5194/EED-3-1-2008","url":null,"abstract":"HAL is a multi-disciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L’archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d’enseignement et de recherche français ou étrangers, des laboratoires publics ou privés. Zoogeography of the bottom Foraminifera of the West-African coast V. Mikhalevich","PeriodicalId":394654,"journal":{"name":"Eearth Discussions","volume":"12 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2008-03-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122009240","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Paleodepth variations on the Eratosthenes Seamount (Eastern Mediterranean): sea-level changes or subsidence?","authors":"S. Spezzaferri, F. Tamburini","doi":"10.5194/EED-2-115-2007","DOIUrl":"https://doi.org/10.5194/EED-2-115-2007","url":null,"abstract":"The Eratosthenes Seamount (Eastern Mediterranean) is interpreted as a crustal block in process of break up in response to subduction and incipient collision of the African and Eurasian Plates. Subsidence is considered to be the mechanism triggering the Messinian to Pleistocene water deepening above this unique structure. However, the 5 application of a recently developed transfer equation of depth range distribution of benthic foraminifera indicates that sea-level changes may also have played a role, although it was generally minor. In particular, we suggest that across the Miocene/Pliocene boundary and during the Pliocene-Pleistocene, the eustatic signal is frequently coupled with uplifts and subsidence. The uplift of Cyprus across the Pliocene-Pleistocene 10 transition is clearly recorded in the paleodepth curve. Micropaleontological studies and the use of this transfer equation based on the distribution of benthic foraminifera proves to be useful when studying the paleodepth history of complex sites, where tectonic and eustatic signals combine. We also show that marginal seas record global sea-level changes that can be identified even in tectonically active settings. 15","PeriodicalId":394654,"journal":{"name":"Eearth Discussions","volume":"30 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-09-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131660599","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A normalised seawater strontium isotope curve and the Neoproterozoic-Cambrian chemical weathering event","authors":"G. Shields","doi":"10.5194/EED-2-69-2007","DOIUrl":"https://doi.org/10.5194/EED-2-69-2007","url":null,"abstract":"Introduction Conclusions References Tables Figures ◭ ◮ ◭ ◮","PeriodicalId":394654,"journal":{"name":"Eearth Discussions","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-03-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"125888609","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Exhumation of metamorphic rocks in N Aegean: the path from shortening to extension and extrusion","authors":"R. Lacassin, N. Arnaud, P. Leloup, R. Armijo, B. Meyer","doi":"10.5194/EED-2-1-2007","DOIUrl":"https://doi.org/10.5194/EED-2-1-2007","url":null,"abstract":"The Olympos-Ossa-Pelion (OOP) ranges, in NW Aegean, encompass Greece highest summit and are located near the extremity of the North Anatolian Fault (NAF). Structural and thermochronological data gathered in the OOP ranges show that the main exhumation of metamorphic nappes occurred in the Eocene, at ca. 43-39 Ma. This early exhumation, associated with ductile, then brittle-ductile normal faulting with northeastward transport, is nearly coeval with orogenic shortening in the close area. Cooling rates, and likely exhumation, have been low between ~40 Ma and ~20 Ma. 40 Ar/ 39 Ar crystallization ages (between 20 and 15 Ma) appears related to brittle-ductile normal faulting and likely associated with the onset of Aegean back-arc extension. The dating of a diabase dyke, and the geometry of associated brittle jointing, of onshore and offshore active normal faults imply a shift in extension direction after 4 Ma. Such a shift is probably related the propagation of the NAF in northern Aegean known to have occurred around 5 Ma.","PeriodicalId":394654,"journal":{"name":"Eearth Discussions","volume":"16 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-01-18","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"114394557","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"What olivine, the neglected mineral, tells us about kimberlite petrogenesis","authors":"N. Arndt, A. Boullier, J. Clement, M. Dubois, D. Schissel","doi":"10.5194/EE-1-15-2006","DOIUrl":"https://doi.org/10.5194/EE-1-15-2006","url":null,"abstract":"We report here the results of a petrographic and geochemical study of remarkably well-preserved kimber- lites from the Kangamiut region in Greenland. The sam- ples contain between 5 and 45% of olivine in the form of rounded \"nodules\", each 1 to 5 mm in diameter. Most orig- inally were single crystals but many consist of polycrys- talline, monomineralic aggregates. Olivine compositions vary widely from nodule to nodule (from Fo 81-93) but are constant within individual nodules. A thin rim of high-Ca olivine of intermediate composition (Fo 87-88) surrounds many nodules. Deformation structures in olivine in the nod- ules and in the matrix demonstrate a xenocrystic origin for the olivine: only olivine in the thin rims is thought to have crystallized from the kimberlite magma. Using major and trace element data, we show that the kimberlite compositions are controlled by the addition of xenocrystic olivine into a parental magma that contained about 24-28% MgO. The monomineralic character of the olivine nodules is problematic because dunite is a relatively rare rock in the lithospheric mantle. The source of the xenocrystic olivine lacked pyroxene and an aluminous phase, which make up about half of most mantle-derived rocks. It appears that these minerals were removed from the material that was to become the nodules, perhaps by fluids that immediately preceded the passage of the kimberlites. We speculate that this mantle \"de- fertilization\" process was linked to interaction between CO 2- rich fluid and mantle and that this interaction controlled the geochemical and isotopic composition of kimberlites.","PeriodicalId":394654,"journal":{"name":"Eearth Discussions","volume":"147 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-10-23","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"127252056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Extracting low frequency climate signal from GRACE data","authors":"O. Viron, M. Diament, I. Panet","doi":"10.5194/EE-1-9-2006","DOIUrl":"https://doi.org/10.5194/EE-1-9-2006","url":null,"abstract":"For more than four years, the GRACE pair of satellites have been orbiting the Earth, monitoring the time variable mass distribution for scales ranging from regional to global. The GRACE data have been released for a broad scientific community and sets of gravity fields are available. This paper shows that there are evidences at interrannual time scales for the presence of ENSO signal in the data, strongly correlated with the hydrological mass distribution, and also similar to the expected hydrological signature asso- ciated with the ENSO cycle. This signal dominates, at global scale, the one associated with geodynamic sources.","PeriodicalId":394654,"journal":{"name":"Eearth Discussions","volume":"32 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-10-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124305618","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"A calibrated radiocarbon database of late Quaternary volcanic eruptions","authors":"R. U. Bryson, R. Bryson, A. Ruter","doi":"10.5194/EED-1-123-2006","DOIUrl":"https://doi.org/10.5194/EED-1-123-2006","url":null,"abstract":"Researchers at the Center for Climatic Research (CCR) at the University of Wisconsin-Madison have revised and calibrated a global volcanic database compiled from more than 2000 radiocarbon-dated eruptions from the late Pleistocene and Holocene. The updated database is available online as an appendix to this correspondence (http://www.electronic-earth-discuss.net/1/123/2006/eed-1-123-2006-supplement.zip). We briefly describe the database, suggest some potential applications, and invite other researchers in the geologic and atmospheric sciences to both use and help refine the archive by incorporating additional data as it becomes available.","PeriodicalId":394654,"journal":{"name":"Eearth Discussions","volume":"484 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-25","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"123558073","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}

{"title":"Horizontal versus vertical plate motions","authors":"M. Cuffaro, E. Carminati, C. Doglioni","doi":"10.5194/EED-1-63-2006","DOIUrl":"https://doi.org/10.5194/EED-1-63-2006","url":null,"abstract":"We review both present and past motions at major plate boundaries, which have the horizontal component in average 10 to 100 times faster (10?100 mm/yr) than the vertical component (0.01?1 mm/yr) in all geodynamic settings. The steady faster horizontal velocity of the lithosphere with respect to the upward or downward velocities at plate boundaries supports dominating tangential forces acting on plates. This suggests a passive role of plate boundaries with respect to far field forces determining the velocity of plates. The forces acting on the lithosphere can be subdivided in coupled and uncoupled, as a function of the shear at the lithosphere base. Higher the asthenosphere viscosity, more significant should be the coupled forces, i.e., the mantle drag and the trench suction. Lower the asthenosphere viscosity, more the effects of uncoupled forces might result determinant, i.e., the ridge push, the slab pull and the tidal drag. Although a combination of all forces acting on the lithosphere is likely, the decoupling between lithosphere and mantle suggests that a torque acts on the lithosphere independently of the mantle drag. Slab pull and ridge push are candidates for generating this torque, but, unlike these boundary forces, the advantage of the tidal drag is to be a volume force, acting simultaneously on the whole plates, and being the decoupling at the lithosphere base controlled by lateral variations in viscosity of the low-velocity layer.","PeriodicalId":394654,"journal":{"name":"Eearth Discussions","volume":"17 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2006-07-03","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"133594056","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}