First historical evidence of a significant Mt. Etna eruption in 1224     

Emanuela Guidoboni  Cecilia Ciuccarelli 《Journal of Volcanology and Geothermal Research》2008

The 1224 Mt. Etna eruption is a significant event both in terms of the mass of erupted materials and because it involved the lower eastern slope of the volcano, reaching down to the sea. Nevertheless, it is unknown to current historical catalogues. According to the historical sources, only two other lava flows actually reached as far as the sea: in 396 BC, just north of the present-day inhabited area of Acireale, according to the geological data alone, and in 1669, when the lava covered the south-eastern flank of Mt. Etna and damaged Catania. We present and discuss the two medieval sources that attest to the eruption of 1224 and make available the original texts. Furthermore, through the close analysis of the historical and topographic context of the Etna area, taking account of the roads and ports in the early 13th century, we have tried to single out the possible area of the lava's outlet into the sea in 1224 on historical grounds. A repeat of an eruption similar to that of 1224 would have a serious impact today as the coast is densely populated.  相似文献   

Patterns and Levels of Organochlorines (DDTs, PCBs, non-ortho PCBs and PCDD/Fs) in Male Harbour Porpoises (Phocoena phocoena) from the Baltic Sea, the Kattegat-Skagerrak Seas and the West Coast of Norway     

Per Berggren  Rasha Ishaq  Yngve ZebÜhr  Carina Nf  Cecilia Bandh  Dag Broman 《Marine pollution bulletin》1999,38(12):238-1084

Patterns and levels of chlorinated aromatic contaminants (DDTs, PCBs, non-ortho PCBs and PCDD/Fs) in blubber tissue were compared among six sample groups of male harbour porpoises (Phocoena phocoena) from the Baltic Sea, the Kattegat-Skagerrak Seas and the west coast of Norway. A principal component and classification analysis showed that mature harbour porpoises from the Baltic had significantly different contaminant patterns than animals from the Kattegat-Skagerrak and Norway. ANOVAs showed that mature porpoises from the Baltic had higher levels of ΣPCB and several individual PCBs and PCDD/Fs than the Kattegat-Skagerrak and the Norwegian samples and higher ΣDDT than the Norwegian. A comparison between immature porpoises showed that Baltic animals had higher levels of ΣPCDD/F than the corresponding sample from the Kattegat-Skagerrak. The levels of ΣDDT, ΣPCB and Σnon-ortho PCB were significantly higher in animals collected during 1978–81 compared to animals collected in 1988–90 indicating a temporal decline of these organochlorines in the Kattegat-Skagerrak Seas. The contaminant levels recorded in the Baltic Sea are a serious cause for concern and could have management implications for the already threatened harbour porpoises in this area.  相似文献   

Assessment of Geogenic and Anthropogenic Pollution Sources Using an Aquatic Plant Along the Sonora River Basin: Insights from Elemental Concentrations and Pb Isotope Signatures     

Romo-Morales  Diana  Moreno-Rodríguez  Verónica  Molina-Freaner  Francisco  Valencia-Moreno  Martín  Ruiz  Joaquín  Minjárez-Osorio  Christian  Hernández-Mendiola  Ernesto  del Rio-Salas  Rafael 《Natural Resources Research》2020,29(4):2773-2786

Natural Resources Research - Mining is an important activity in Mexico; however, despite its economic benefits, it carries potential environmental risks, including mine spills. On August 6,...  相似文献   

Black hole spin and radio loudness in a Λ cold dark matter universe     

Claudia del P. Lagos  Nelson D. Padilla  Sofía A. Cora 《Monthly notices of the Royal Astronomical Society》2009,395(2):625-636

We use a combination of a cosmological N -body simulation of the concordance Λ cold dark matter paradigm and a semi-analytic model of galaxy formation to investigate the spin development of central supermassive black holes (BHs) and its relation to the BH host galaxy properties. In order to compute BH spins, we use the α model of Shakura & Sunyaev and consider the King et al. warped disc alignment criterion. The orientation of the accretion disc is inferred from the angular momentum of the source of accreted material, which bears a close relationship to the large-scale structure in the simulation. We find that the final BH spin depends almost exclusively on the accretion history and only weakly on the warped disc alignment. The main mechanisms of BH spin-up are found to be gas cooling processes and disc instabilities, a result that is only partially compatible with Monte Carlo models where the main spin-up mechanisms are major mergers and disc instabilities; the latter results are reproduced when implementing randomly oriented accretion discs in our model. Regarding the BH population, we find that more massive BHs, which are hosted by massive ellipticals, have higher spin values than less massive BHs, hosted by spiral galaxies. We analyse whether gas accretion rates and BH spins can be used as tracers of the radio loudness of active galactic nuclei (AGN). We find that the current observational indications of an increasing trend of radio-loud AGN fractions with stellar and BH mass can be easily obtained when placing lower limits on the BH spin, with a minimum influence from limits on the accretion rates; a model with random accretion disc orientations is unable to reproduce this trend. Our results favour a scenario where the BH spin is a key parameter to separate the radio-loud and radio-quiet galaxy populations.  相似文献   

A large-scale extinction map of the Galactic Anticentre from 2MASS     

D. Froebrich  G. C. Murphy  M. D. Smith  J. Walsh  C. del Burgo 《Monthly notices of the Royal Astronomical Society》2007,378(4):1447-1460

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COSTEP - Comprehensive Suprathermal and Energetic Particle Analyser   总被引：1，自引：0，他引：1  

R. Müller-Mellin  H. Kunow  V. Fleißner  E. Pehlke  E. Rode  N. Röschmann  C. Scharmberg  H. Sierks  P. Rusznyak  S. Mckenna-Lawlor  I. Elendt  J. Sequeiros  D. Meziat  S. Sanchez  J. Medina  L. del Peral  M. Witte  R. Marsden  J. Henrion 《Solar physics》1995,162(1-2):483-504

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Conformal geometry of the Kepler orbit space     

José F. Cariñena  Carlos López  Mariano A. del Olmo  Mariano Santander 《Celestial Mechanics and Dynamical Astronomy》1991,52(4):307-343

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Upper Eocene ejecta of the New Jersey continental margin reveal dynamics of Chesapeake Bay impact     

Cecilia M.G McHugh  Scott W Snyder  Kenneth G Miller   《Earth and Planetary Science Letters》1998,160(3-4):353-367

Evidence for the Chesapeake Bay Crater as the source for New Jersey continental margin ejecta is provided by fine-grained tektites and coarse-grained unmelted ejecta. The Upper Eocene ejecta deposit, now demonstrated to be part of the North American strewn field, occurs on the New Jersey continental margin at Ocean Drilling Program (ODP) Sites 904 and 903. The mineralogy, major oxide composition of the ejecta materials, and biostratigraphic age of the enclosing sediments link the origin of these ejecta to the recently recognized Chesapeake Bay impact crater, located only 330 km away. Sediments associated with the ejecta provide information about the dynamics of impact events. The 35-cm-thick ejecta-bearing layer can be subdivided into three subunits that indicate a sequence of events. Bottom subunit III documents sediment failure and deposition of gravel-sized fragments, middle subunit II records deposition of abundant sand-sized ejecta by gravity settling, and upper subunit I contains a 12-cm-thick sedimentary deposit containing rare silt-sized tektites and evidence of waning currents. These events are interpreted by linking sediment deposition to seismic ground motion and subsequent tsunami waves triggered by both the Chesapeake Bay impact and slope failures.  相似文献   

Differential responses of hillslope and channel elements to rainfall events in a semi-arid area     

Juan Puigdefabregas  Gabriel del Barrio  Matthias M. Boer  Leonardo Gutirrez  Albert Sol 《Geomorphology》1998,23(2-4)

The degree of hydrological connectivity of hillslope elements in a semi-arid climate was studied at the season and event timescales. Field data were obtained in Rambla Honda, a Medalus project field site situated in SE Spain, on micaschist bedrock and with 300 mm annual rainfall. The season timescale was assessed using correlation analysis between soil moisture and topographic indices. The event timescale was studied by a quasi-continuous monitoring of rainfall, soil moisture, runoff and piezometric levels. Results show that widespread transfers of water along the hillslope are unusual because potential conditions for producing overland flow or throughflow are spatially discontinuous and extremely short-lived. During extreme events, runoff coefficients may be locally high (ca. 40% on slope lengths of 10 m), but decrease dramatically at the hillslope scale (<10% on slope lengths of 50 m). Two mechanisms of overland flow generation have been identified: infiltration excess, and local subsurface saturation from upper layers. The former occurs during the initial stages of the event while the latter, which is quantitatively more important, takes place later and requires a certain time structure of rainfall intensities that allow saturation of the topsoil and the subsequent production of runoff. Hillslopes and alluvial fans function as runoff sources and sinks respectively. Permanent aquifers are lacking in Rambla Honda. Variable proportions of hillslope areas may contribute to flash floods in the main channel, but their contribution to the formation of saturated layers within the sediment fill is very limited.  相似文献   

Nuclear stellar discs in early-type galaxies — II. Photometric properties     

Cecilia Scorza  & Frank C. van den Bosch 《Monthly notices of the Royal Astronomical Society》1998,300(2):469-478

Hubble Space Telescope images of two early-type galaxies harbouring both nuclear and outer stellar discs are studied in detail. By means of a photometric decomposition, the images of NGC 4342 and 4570 are analysed and the photometric properties of the nuclear discs investigated. We find a continuity of properties in the parameter space defined by the central surface brightness μ₀ and the scalelength R _d of discs in spirals, S0s and embedded discs in ellipticals, in the sense that the nuclear discs extend the observed disc properties even further towards smaller scalelengths and brighter central surface brightnesses. When including the nuclear discs, disc properties span more than four orders of magnitude in both scalelength and central surface brightness. The nuclear discs studied here are the smallest and brightest stellar discs known, and as such, they are as extreme in their photometric properties as Malin I, when compared with typical galactic discs that obey Freeman's law. We discuss a possible formation scenario in which the double-disc structure observed in these galaxies has been shaped by now dissolved bars. Based on the fact that the black holes known to exist in some of these galaxies have masses comparable to those of the nuclear discs, we explore a possible link between the black holes and the nuclear discs.  相似文献