A dated volcano-tectonic deformation event in Jan Mayen causing landlocking of Arctic charr     

Eiliv Larsen  Astrid Lyså  Ármann Höskuldsson  Jan G. Davidsen  Marie J. Nadeau  Michael Power  Georgios Tassis  Stefan Wastegård 《第四纪科学杂志》2021,36(2):180-190

We provide the first documentation of tectonic deformation resulting from a volcanic eruption on the island of Jan Mayen. Vertical displacement of about 14 m southwest of the stratovolcano Beerenberg is associated with an eruption in ad 1732 on its southeastern flank. The age of the uplift event is bracketed by radiocarbon-dated driftwood buried by material deposited due to uplift, and by tephra from this eruption. Constraints, inferred from radiocarbon ages alone, allow for the possibility that uplift was completed prior to the ad 1732 eruption. However, the occurrence of tephra in the sediment column indicates that some displacement was ongoing during the eruption but ceased before the eruption terminated. We attribute the tectonic deformation to intrusion of shallow magma associated with the volcanic eruption. Our results complement previous studies of volcanic activity on Jan Mayan by providing precise age constraints for past volcanic activity. Also, it raises new hypotheses regarding the nature, timing and prevalence of precursor tectonic events to Jan Mayan eruptions. The uplift caused the complete isolation of a coastal lake by closing its outlet to the sea, thus landlocking the facultative migratory fish species Arctic charr (Salvelinus alpinus).  相似文献   

Analysis of the rainfall pattern triggering the Lemešná debris flow,Javorníky Range,the Czech Republic     

Smolíková  Jana  Hrbáček  Filip  Blahůt  Jan  Klimeš  Jan  Vilímek  Vít  Loaiza Usuga  Juan Carlos 《Natural Hazards》2021,106(3):2353-2379

Natural Hazards - Two significant rainfall episodes affected the eastern part of the Czech Republic in May 2010 causing dozens of landslides, including a potentially damaging debris flow on...  相似文献   

Global Calibration of SARAL/AltiKa Using Multi-Mission Sea Surface Height Crossovers     

Denise Dettmering  Christian Schwatke  Wolfgang Bosch 《Marine Geodesy》2015,38(3):206-218

SARAL/AltiKa completed its first year in orbit in March 2014. The 1 Hz GDR-T data of the first 10 cycles of the mission are used to perform a comprehensive quality assessment by means of a global multi-mission crossover analysis. Within this approach, SARAL sea surface heights are compared with data from other current missions, mainly Jason-2 and Cryosat-2, to reveal its accuracy and consistency with the other altimeter systems. Alongside with global mean range bias and instrumental drifts, investigations on geographically correlated errors as well as on the realization of the systems origin are performed. The study proves the high quality and reliability of SARAL. The mission shows only a small range bias of about ?5 cm with respect to Jason-2 and neither significant time-tag bias nor instrumental drifts. With 1.3 cm the scatter of radial errors is in the same order of magnitude as for Cryosat-2 and Jason-1 GM and will probably further improve using an enhanced sea state bias (SSB) model. However, the wet tropospheric corrections from SARAL radiometer still show some systematic effects influencing the range bias as well as geographically correlated error patterns and the z-component of the origin. Improved inflight calibration will be necessary to overcome these effects.  相似文献   

Effects on satellite orbits in the gravitational field of an axisymmetric central body with a mass monopole and arbitrary spin multipole moments     

Jan Meichsner  Michael H. Soffel 《Celestial Mechanics and Dynamical Astronomy》2015,123(1):1-12

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Cosmogenic radionuclides and mineralogical properties of the Chelyabinsk (LL5) meteorite: What do we learn about the meteoroid?          下载免费PDF全文

Pavel P. Povinec  Matthias Laubenstein  A. J. Timothy Jull  Ludovic Ferrière  Franz Brandstätter  Ivan Sýkora  Jozef Masarik  Juraj Beňo  Andrej Kováčik  Dan Topa  Christian Koeberl 《Meteoritics & planetary science》2015,50(2):273-286

On February 15, 2013, after the observation of a brilliant fireball and a spectacular airburst over the southern Ural region (Russia), thousands of stones fell and were rapidly recovered, bringing some extremely fresh material for scientific investigations. We undertook a multidisciplinary study of a dozen stones of the Chelyabinsk meteorite, including petrographic and microprobe investigations to unravel intrinsic characteristics of this meteorite. We also study the short and long‐lived cosmogenic radionuclides to characterize the initial meteoroid size and exposure age. Petrographic observations, as well as the mineral compositions obtained by electron microprobe analyses, allow us to confirm the classification of the Chelyabinsk meteorite as an LL5 chondrite. The fragments studied, a few of which are impact melt rocks, contain abundant shock melt veins and melt pockets. It is likely that the catastrophic explosion and fragmentation of the Chelyabinsk meteoroid into thousands of stones was in part determined by the initial state of the meteoroid. The radionuclide results obtained show a wide range of concentrations of ¹⁴C, ²²Na, ²⁶Al, ⁵⁴Mn, ⁵⁷Co, ⁵⁸Co, and ⁶⁰Co, which indicate that the pre‐atmospheric object had a radius >5 m, consistent with other size estimates based on the magnitude of the airburst caused by the atmospheric entry and breakup of the Chelyabinsk meteoroid. Considering the observed ²⁶Al activities of the investigated samples, Monte Carlo simulations, and taking into account the ²⁶Al half‐life (0.717 Myr), the cosmic‐ray exposure age of the Chelyabinsk meteorite is estimated to be 1.2 ± 0.2 Myr. In contrast to the other radionuclides, ¹⁴C showed a very large range only consistent with most samples having been exposed to anthropogenic sources of ¹⁴C, which we associate with radioactive contamination of the Chelyabinsk region by past nuclear accidents and waste disposal, which has also been confirmed by elevated levels of anthropogenic ¹³⁷Cs and primordial ⁴⁰K in some of the Chelyabinsk fragments.  相似文献   

Prediction of phase ambiguity resolution based on signal intensity and geometry     

Daniel Willi  Jan Skaloud 《GPS Solutions》2015,19(3):467-474

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Temporal trends of mercury in marine biota of west and northwest Greenland     

Rigét F  Dietz R  Born EW  Sonne C  Hobson KA 《Marine pollution bulletin》2007,54(1):72-80

Temporal trends in mercury concentrations ([Hg]) during the last two to three decades were determined in liver of shorthorn sculpin, ringed seal and Atlantic walrus from northwest Greenland (NWG, 77 degrees N) and in liver of shorthorn sculpin and ringed seal from central west Greenland (CWG, 69 degrees N) during the last decade. Stable-nitrogen (delta(15)N) and carbon (delta(13)C) isotope values were determined in muscle of ringed seals to provide insight into potential trophic level changes through time. Log-linear regressions on annual median [Hg] did not reveal any temporal trend in shorthorn sculpin from CWG and NWG and walrus from NWG. In ringed seals from NWG, an increase in [Hg] of 7.8% per year was observed. When based on delta(15)N-adjusted [Hg] this rate increased to 8.5% but was still non-significant. In ringed seal from CWG no trend was found in [Hg] during the period 1994-2004. However, during the last part of the period (1999-2004) the [Hg] increased significantly. Including tissue delta(15)N values as a covariate had a marked effect on these results. The annual changes in delta(15)N-adjusted [Hg] was estimated to -5.0% for the whole period and 2.2% during the last 5 years compared to -1.3% and 12.4%, respectively, for the non-adjusted [Hg].  相似文献   

Effects of acoustic alarms, designed to reduce small cetacean bycatch in gillnet fisheries, on the behaviour of North Sea fish species in a large tank     

Kastelein RA  van der Heul S  van der Veen J  Verboom WC  Jennings N  de Haan D  Reijnders PJ 《Marine environmental research》2007,64(2):160-180

World-wide many cetaceans drown incidentally in fishing nets. To reduce the unwanted bycatch in gillnets, pingers (acoustic alarms) have been developed that are attached to the nets. In the European Union, pingers will be made compulsory in some areas in 2005 and in others in 2007. However, pingers may effect non-target marine fauna such as fish. Therefore in this study, the effects of seven commercially-available pingers on the behaviour of five North Sea fish species in a large tank were quantified. The species tested were: sea bass (Dicentrarchus labrax), pout (Trisopterus luscus), thicklip mullet (Chelon labrosus), herring (Clupea harengus), and cod (Gadus morhua). The fish were housed as single-species schools of 9-13 individuals in a tank. The behaviour of fish in quiet periods was compared with their behaviour during periods with active pingers. The results varied both between pingers and between fish species. Sea bass decreased their speed in response to one pinger and swam closer to the surface in response to another. Thicklip mullet swam closer to the bottom in response to two pingers and increased their swimming speed in response to one pinger. Herring swam faster in response to one pinger, and pout and cod (close relatives) showed no behavioural responses to any of the pingers. Of the seven pingers tested, four elicited responses in at least one fish species, and three elicited no responses. Whether similar responses would be elicited in these fish species in the wild, and if so, whether such responses would influence the catch rate of fisheries, cannot be derived from the results of this study. However, the results indicate the need for field studies with pingers and fish. Based on the small number of fish species tested, the present study suggests that the higher the frequency of a pinger, the less likely it is to affect the behaviour of marine fish.  相似文献   

Formation of lunar mare domes along crustal fractures: Rheologic conditions, dimensions of feeder dikes, and the role of magma evolution   总被引：1，自引：0，他引：1  

Christian Wöhler  Raffaello Lena 《Icarus》2007,189(2):279-307

In this study we examine a set of lunar mare domes located in the Hortensius/Milichius/T. Mayer region and in northern Mare Tranquillitatis with respect to their formation along crustal fractures, their rheologic properties, the dimensions of their feeder dikes, and the importance of magma evolution processes during dome formation. Many of these domes display elongated summit vents oriented radially with respect to major impact basins, and several dome locations are also aligned in these preferential directions. Analysis of Clementine UV/VIS and Lunar Prospector gamma ray spectrometer data reveals that the examined mare domes formed from low-Si basaltic lavas of high FeO and low to moderate TiO₂ content. Based on their morphometric properties (diameter, height, volume) obtained by photoclinometric and shape from shading analysis of telescopic CCD images, we derive rheologic quantities (lava viscosity during eruption, effusion rate, duration of the effusion process, magma rise speed) and the dimensions of the feeder dikes. We establish three rheologic groups characterised by specific combinations of rheologic properties and dike dimensions, where the most relevant discriminative parameter is the lava viscosity η. The first group is characterised by and contains the domes with elongated vents in the Milichius/T. Mayer region and two similar domes in northern Mare Tranquillitatis. The second group with comprises the very low aligned domes in northern Mare Tranquillitatis, and the third group with the relatively steep domes near Hortensius and in the T. Mayer region. The inferred dike dimensions in comparison to lunar crustal thickness data indicate that the source regions of the feeder dikes are situated within the upper crust for six of the domes in northern Mare Tranquillitatis, while they are likely to be located in the lower crust and in the upper mantle for the other examined domes. By comparing the time scale of magma ascent with the time scale on which heat is conducted from the magma into the host rock, we find evidence that the importance of magma evolution processes during ascent such as cooling and crystallisation increases with lava viscosity. We conclude that different degrees of evolution of initially fluid basaltic magma are able to explain the broad range of lava viscosities inferred for the examined mare domes. The spectral data reveal that differences in TiO₂ content may additionally account for the systematic difference in lava viscosity between the two examined lunar regions. We show that the described mechanisms are likely to be valid also for other lunar mare domes situated near Cauchy and Arago, regarded for comparison. On the other hand, we find for the Gruithuisen and Mairan highland domes that despite their inferred high lava viscosities of , no significant magma cooling in the dike occurred during ascent, supporting previous findings that the highland domes were formed during a specific phase of non-mare volcanism by highly silicic viscous lavas.  相似文献   

Developmental disorders in larvae of eelpout (Zoarces viviparus) from German and Swedish Baltic coastal waters     

Gercken J  Förlin L  Andersson J 《Marine pollution bulletin》2006,53(8-9):497-507

Pregnant eelpout were collected for several years at German and Swedish Baltic coastal stations with different impact of pollutants and the prevalence of fry abnormalities compared between sites. Mortality of apparently normal developed larvae was observed with high variability in both German and Swedish sites. Malformation of larvae was a prominent disorder at all German stations with a prevalence ranging from about 50% up to a maximum of 90% in almost all analysed samples. At the Swedish stations malformation rates were significantly lower (range: 0-6%). Growth retardation of fry was clearly more prominent in eelpout from German coastal waters as well. Taken together the field data suggests that impaired larval development was associated with the state of environmental pollution at the sampling locations.  相似文献