pollution and paradigms lessons from icelandic volcanism for continental flood basalt studies grattan j pollution and paradigms lessons from icelandic volcanism for continental flood basalt studies lithos 2005 79 pp 343 353

palaeomagnetic data suggest link between the archaean proterozoic boundary and inner core nucleation it is generally believed that the earth s magnetic field arises from dynamo action in the convecting outer core1 3 thus the geomagnetic field and especially its strength can provide information about core processes recent determinations of the geomagnetic palaeointensity using archaean and early proterozoic samples from the kaapvaal and superior cratons are consistent with a sharp increase in the magnitude of the geomagnetic field between 2 7 and 2 1 gyr analysis of published late archaean and early proterozoic apparent polar wander paths shows that an abrupt change in the rate and style of continental motion occurred at about 2 5 2 6 gyr ago if this change is also interpreted to be related to the growth of an inner core then an intriguing conjecture arises that the archaean proterozoic transition is related to inner core nucleation

chemical and magnetic tracing of coal slag pollutants in karstic river sediments the mre nica river near duga resa croatia serves as an ideal natural laboratory for studying downstream transport of material in river systems this study expands the so far brief knowledge about magnetic and chemical properties of sediments along the lower course of this river contaminated by discharge of coal slag and ash from a former textile factory directly released into the river for 110 years 1884 1994 magnetic susceptibility of the river sediments is very high close to the pollution source and shows a decreasing trend downstream still being above the level of unpolluted sediments just before the confluence with the korana river app 7 km away from the point source thermomagnetic curves reveal magnetite as the dominant magnetic mineral and low frequency dependent susceptibility indicates an anthropogenic origin most heavy metals and other elements in the sediments show a decreasing trend in the downstream direction similar to the magnetic concentration signal correlation analysis between magnetic susceptibility and concentrations of 29 elements shows strongest correlations with co r 0 70 fe r 0 92 sr r 0 86 al r 0 74 u r 0 78 and b r 0 96 cluster analysis distinguishes three clusters cluster 1 is under strong influence of contamination and contains four sampling sites cluster 2 has extreme values of cd cr mo and ni and contains seventeen sites cluster 3 reflects rather clean sites and contains nine sites according to existing sediment quality criteria ni and cr show the largest degree of contamination among six evaluated heavy metals strong variability in the data and frequent extremes are to a large degree caused by heterogeneity in the spatial distribution of the coal derived material to account for this situation and to resolve the variability in more detail statistical sampling of sediments in river cross sections and estimation of the sediment volume are needed being a target for further research

the antiquity indicator argon 40 argon 36 for lunar surface samples calibrated by uranium 235 xenon 136 dating several solar gas rich lunar soils and breccias have trapped 40ar 36ar ratios 10 although solar ar is expected to yield a ratio of 0 01 radiogenic 40ar produced in the lunar crust from 40k decay was outgassed into the lunar atmosphere ionized accelerated in the electromagnetic field of the solar wind and reimplanted into lunar surface material the 40ar loss rate depends on the decreasing abundance of 40k in order to calibrate the time dependence of the 40ar 36ar ratio in lunar surface material the period of reimplantation of lunar atmospheric ions and of solar wind ar was determined using the 235u 136xe dating method that relies on secondary cosmic ray neutron induced fission of 235u we identified the trapped fissiogenic and cosmogenic noble gases in lunar breccia 14307 and lunar soils 70001 8 70181 74261 and 75081 uranium and th concentrations were determined in the 74261 soil for which we obtain the 235u 136xe time of implantation of 3 25 0 38 0 60 ga ago on the basis of several cosmogenic noble gas signatures we calculate the duration of this near surface exposure of 393 45 ma and an average shielding depth below the lunar surface of 73 7 g cm2 a second recent exposure to solar and cosmic ray particles occurred after this soil was excavated from shorty crater 17 2 1 4 ma ago using a compilation of all lunar data with reliable trapped ar isotopic ratios and pre exposure times we infer a calibration curve of implantation times based on the trapped40 ar 36ar ratio a possible trend for the increase with time of the solar 3he 4he and 20ne 22ne ratios of about 12 ga and about 2 ga respectively is also discussed

mortality in england during the 1783 4 laki craters eruption 1783 4 has been recognised as a mortality crisis year in the population history of england this demographic incident coincides with the laki craters eruption iceland which began in june 1783 and fumigated many parts of europe with volcanic gases and particles many reports and proxy climate records implicate the volcanic cloud in meteorological anomalies including notably hot 1783 summer conditions in england and a severe subsequent winter we present here a detailed analysis of the geographical and temporal trends in english mortality data and interpret them in the light of the climatological records and observations of the pollutant cloud we show that there were two distinct crisis periods in august september 1783 and january february 1784 which together accounted for 20 000 extra deaths in both cases the east of england was the worst affected region possible causes for the two crisis periods are considered and we conclude that the timing and magnitude of the winter mortality peak can be explained by the severe cold of january 1784 the late summer mortality followed 1 2 months after the very hot july of 1783 and may also have been related to the weather with the time lag reflecting the relatively slow spread of enteric disease or the contraction of malaria however it is hard to explain the entire late summer anomaly by these high temperature causes we therefore consider that fine acid aerosol and or gases in the volcanic haze may also have contributed to the unusual august september mortality given that complex radiative and dynamical effects of the volcanic cloud are implicated in the climatic anomalies in 1783 4 it is likely that the laki craters eruption did play a role in the english mortality crises of the same period

sedimentation in a disequilibrium river dominated estuary the rasa river estuary adriatic sea croatia this paper examines sediment transport sedimentation and properties of suspended matter and sediments in the rasa river estuary a small rock bounded microtidal low wave energy karstic estuary in the north eastern adriatic the rasa river is characterized by large variation in water flow and variable load of mineral particles more than 90 of this load is brought into the estuary as fine grained suspended matter consisting of only 24 36 of carbonates the rest being clays sedimentation occurs at the salt wedge resulting in a prograding estuarine delta salt induced flocculation is the predominant process of sediment deposition the rasa estuary is infilling with sediment and classifies as a disequilibrium estuary we propose a modification of cooper s 1993 classification scheme to include river dominated disequilibrium estuaries with the rasa river as an example

the effect of volcanic eruptions on the chemistry of surface waters the 1991 and 2000 eruptions of mt hekla iceland abstract the mt hekla eruptions in 1991 and 2000 have provided a unique opportunity to study the local environmental effects of high latitude volcanic eruptions in the middle of winter both eruptions started around sunset at sub zero temperatures in order to define better these effects we studied the chemistry of surface waters in the vicinity of the volcano additionally we describe and predict the environmental consequences of these volcanic eruptions on the chemistry of surface waters on land and in the ocean several dissolved elements in the polluted snow melt from the 2000 eruption cl f al fe mn as cd pb zn and u exceeded the limits for water intended for human consumption the volcanic ash the primary minerals and secondary mineral phases that commonly form in the weathering environment of iceland were undersaturated in the polluted snow melts with the exception of fluorite barite goethite and amorphous feooh these minerals can constrain the maximum initial concentration of the respective dissolved constituents in the meltwaters it took few days after the first rainfall on the volcanic ash to flush out the readily soluble constituents in the vicinity of the headwaters of the ytri ranga river the polluted river waters were oversaturated with respect to several secondary minerals resulting in precipitation of amorphous al hydroxide and feooh and further scavenging of some trace elements on the al and fe surfaces dissolved al and f were the main contaminants in the ytri ranga river water previous studies have shown that combined al f toxicity is directly related to the predominance of specific al f species in solution model calculations for mixing of a hekla type volcanic cloud with 4 surface water end members shows al f species to be most important in rain and dilute river waters this makes al and f phyto available but diminishes the concentration of the al 3 species the most toxic al species mixing with high alkalinity river waters or seawater results in the domination of non toxic al oh 4 species at dilutions greater than 800 thus hindering al toxicity and bioavailability this study indicates that h 2 so 4 contamination from volcanic eruptions is time and place dependent volcanic eruptions that take place during winter at high latitudes result in relatively high global sulfur contamination and relatively low local sulfur contamination due to the low oxidation rate of so 2 into h 2 so 4 because of the low solar radiation

driftwood dropstones in middle miocene climate optimum shallow marine strata calvert cliffs maryland coastal plain erratic pebbles no certain proxy for cold climate abstract sparse lithic erratics pebbles to cobbles sampled from three shallow marine strata deposited during the middle miocene climate optimum mmco ca 16 14 ma along the western atlantic margin exposed in the calvert cliffs maryland suggest transport and deposition not from ice but from the roots of trees uprooted during floods and carried out to sea evidence for driftwood transport includes carbonized wood in the same strata more than half the ca 225 erratics were quarried in the largely metamorphic piedmont province including a few from the port deposit gneiss still outcropping on the lower susquehanna river the lowest sampled bed parker creek bone bed is assigned to the ca 15 7 15 5 ma peak warmth of the mmco which we attribute in part to co2 from the coevally erupted grande ronde flood basalts grfb the peak effusiveness episode of the columbia river flood basalts crfb the three sampled beds predate the ca 13 9 ma antarctic cryosphere expansion which may be recorded in the calvert cliffs by a unique buried channel

architecture and emplacement of flood basalt flow fields case studies from the columbia river basalt group nw usa the physical features and morphologies of collections of lava bodies emplaced during single eruptions known as flow fields can be used to understand flood basalt emplacement mechanisms characteristics and internal features of lava lobes and whole flow field morphologies result from the forward propagation radial spread and cooling of individual lobes and are used as a tool to understand the architecture of extensive flood basalt lavas the features of three flood basalt flow fields from the columbia river basalt group are presented including the palouse falls flow field a small 8 890 km2 190 km3 unit by common flood basalt proportions and visualized in three dimensions the architecture of the palouse falls flow field is compared to the complex ginkgo and more extensive sand hollow flow fields to investigate the degree to which simple emplacement models represent the style as well as the spatial and temporal developments of flow fields evidence from each flow field supports emplacement by inflation as the predominant mechanism producing thick lobes inflation enables existing lobes to transmit lava to form new lobes thus extending the advance and spread of lava flow fields minimum emplacement timescales calculated for each flow field are 19 3 years for palouse falls 8 3 years for ginkgo and 16 9 years for sand hollow simple flow fields can be traced from vent to distal areas and an emplacement sequence visualized but those with multiple layered lobes present a degree of complexity that make lava pathways and emplacement sequences more difficult to identify

regional warming of the lower atmosphere in the wake of volcanic eruptions the role of the laki fissure eruption in the hot summer of 1783

the role of suspended matter in the biogeochemical cycles in the adige river estuary northern adriatic sea abstract suspended matter and sediments from the adige river mouth were analysed in an attempt to elucidate the transfer of heavy metals from the river to the sea the vertical profile of grain size spectra of suspended matter in front of the river mouth has shown that the riverine particles are limited to the upper brackish layer particulate matter was found to have a large specific surface area up to 20 m 2 g 1 in the estuarine sample high quantities of quartz and phyllosilicates micas and clay minerals were found in the riverine suspended matter the quartz content of the suspended matter from the brackish layer was found to be diminishing and with the organic matter becoming the essential component 22 higher levels of trace metals were usually detected in suspended matter samples 40 ppm ni 200 ppm cr 60 ppm pb 100 ppm cu 320 ppm zn and 0 9 ppm cd than in sediments the observed similarity of physico chemical mineralogical and geochemical characteristics of riverine suspended matter and recent marine sediments indicates that most of the riverborne particulate matter is deposited in the proximity of the adige river mouth the peculiar characteristics of the chromium level high bulk concentration and its abundance in the organic fraction of the particular matter when compared to the other trace metals indicates the anthropogenic influence on its biogeocycle

orphan radiogenic noble gases in lunar breccias evidence for planet pollution of the sun abstract surface correlated noble gases in lunar soils are primarily implanted sw solar wind noble gases however they also include apparently orphan radiogenic 40 ar 129 xe and 244 pu derived fission xe in excess of plausible primordial solar origin these orphan radiogenic components are usually assigned a lunar origin in a scenario in which radiogenic noble gases produced in the lunar interior were degassed into the transient atmosphere and then re implanted to the lunar surface together with sw there are some quantitative difficulties with this scenario however and it requires special constraints on the degassing history of the moon that have not emerged from more general thermal history models we therefore urge consideration of alternative hypotheses as a possible source for the orphan radiogenic noble gases we have examined planetary pollution of the sun as suggested by studies of extrasolar planetary systems e g murray et al 2001 astrophys j 555 801 815 israelian et al 2001 nature 411 163 166 pollution of the sun by 2 m two earth mass planetary materials murray et al 2001 astrophys j 555 801 815 is likely not significant for ar but could be important to account for orphan xe in the moon

sulfur and chlorine in late cretaceous deccan magmas and eruptive gas release large volume p hoehoe lava flows erupted 67 to 65 million years ago forming the deccan traps india the impact of these flood basalt eruptions on the global atmosphere and the coeval end cretaceous mass extinction has been uncertain to assess the potential gas release from this volcanism we measured sulfur and chlorine concentrations in rare glass inclusions inside crystals and on glassy selvages preserved within lavas concentrations range from 1400 parts per million of s and 900 parts per million of cl in inclusions down to a few hundred parts per million in the lava these data indicate that eruptions of deccan lavas could have released at most 0 103 weight of s yielding up to 5 4 teragrams of so2 per cubic kilometer of lava a more conservative estimate is 0 07 weight of s and 0 04 weight of cl yielding 3 5 teragrams of so2 and 1 teragram of hcl for every cubic kilometer of lava erupted the flows were very large in volume and these results imply that huge amounts of s and cl gases were released the environmental impact from even individual eruptions during past flood basalt activity was probably severe

40ar 39ar dating of the thorsmork ignimbrite and icelandic sub glacial rhyolites abstract robust correlation of paleoclimatic archives e g marine sediments ice speleothems necessitates an increase of the number of independent and accurately dated stratigraphic markers using numerical methods icelandic rhyolitic volcanism has a strong chronological interest because these products are found as tephra in the north atlantic marine archives as well as in greenland ice cores in this study we have dated using the 40ar 39ar method subglacial rhyolites of the tindfjallajokull kerlingarfjoll and torfajokull volcanoes which are the main sources of rhyolitic tephra identified in marine and glaciological records the thorsmork ignimbrite tindfjallajokull which correlates with the rhyolitic component ii rhy 1 of the north atlantic ash zone ii naaz ii layer is dated at 55 6 2 4 ka an age that agrees with the ones given by the ice core chronologies gicc05 55 4 1 2 ka the eruptions of rau fossafjoll and fannborg are respectively dated at 77 0 3 0 ka and 149 3 3 4 ka these new ages along with the published ones confirm as already concluded by flude et al 2010 that there is no clear evidence at least at the latitude of iceland that climate warming is the main mechanism that triggered rhyolitic eruptions combining major and trace element compositions with our new age determinations it appears that the rau fossafjoll and the snaefell rhyolitic eruptions have not yet been discovered in marine sediment cores nevertheless given the accuracy and precision of our dating these rhyolitic eruptions have the potential to become chronostratigraphic markers once tephra shards corresponding to these eruptions are discovered in ice and or marine sediment records the fannborg eruption might be recorded in the marine core link 16 during mis 6 prior to the transition to mis5e

non climatic factors and the environmental impact of volcanic volatiles implications of the laki fissure eruption of ad 1783 studies of the potential of icelandic volcanic eruptions to modify the environment of the british isles have primarily concentrated on the degree of induced climate change but models and temperatu

long term changes in solar wind elemental and isotopic ratios a comparison of two lunar ilmenites of different antiquities abstract an ilmenite separate from lunar regolith breccia 79035 a sample presumed to have been exposed to solar wind more than 2 ga ago was analyzed for noble gas and nitrogen elemental and isotopic abundances by stepwise oxidation and pyrolysis the gases appear to be distributed between two distinct reservoirs in the ilmenite defined by release patterns and isotopic considerations one of the reservoirs near grain surfaces yields elemental ratios that for the most part are solar while the other sited at greater depths within grains has severely fractionated elemental abundances and generally heavier isotopic ratios as well xenon provides an exception to the solar abundance pattern in the near surface reservoir being enhanced by about a factor of 2 relative to the expected value a comparison of the 79035 separate with a previously analyzed ilmenite from soil 71501 which received its solar wind exposure much more recently indicates that the two fold xenon enhancement occurs in the fractionated reservoir as well as the solar one and that it may therefore be attributable to a change in the solar wind elemental abundances other differences between the two ilmenites occur in helium and neon isotopic ratios and in he ar elemental ratios since mineralogical influences on retentivities of the gases in the two samples should be the same and possible contributions of non solar wind components to one ilmenite in preference to the other can generally be eliminated or accounted for all of these differences may reflect changes in the solar wind over time

recent deposits and suspended sediments off the po della pila po river main mouth italy abstract present sedimentary conditions in the prodeltaic marine area immediately in front of the po della pila po river main mouth are characterized by a maximum thickness of holocene muds of 10 12 m at a depth of 20 25 m and by two different sedimentary cycles with the more recent lens shaped unit 2 5 4 0 m thick probably deposited in the last 300 yrs the nearshore prodelta area is characterized by rapidly accumulating deposits 2 4 cm yr enriched in smectite gas organic material 1 2 and trace metals the water system presented well marked vertical stratification during the summer of 1985 revealing three distinct water bodies 1 riverine and diluted waters average depth of 3 m 2 middle depth waters 10 20 m and 3 bottom waters temperature oxygen and particulate organic carbon decrease with depth whilst total suspended matter yellow substances and total particulate carbon show maxima at the surface and in the bottom layers and minima in the intermediate waters where the organic fraction comprises 42 of the total

geochemical considerations on trace element distributions in suspended matter and sediments at the river sea interface adige river mouth northern adriatic sea abstract the particulate matter at the adige river mouth has been investigated in order to determine the natural geochemical processes in the estuarine environment and the anthropogenic influence on the biogeochemical cycling of heavy metals the determination of suspended matter and sediment physico chemical characteristics grain size mineralogy organic matter content specific surface area and of concentrations of major and trace elements in the adige river mouth in different hydrological conditions has shown that this mouth acts as a trap for most heavy metals heavy metals were found to be preferentially bonded to the particulates and in the estuarine mixing zone scavenging of most dissolved metals occurs due to salinity and ph gradients and to the formation of new particulate organic matter the surface characteristics of suspended particulate matter fine grain size abundance of clay minerals large specific surface area ssa organic and inorganic coatings favour the adsorption of heavy metals the sedimentation pattern rapid deposition due to flocculation of fine particles and to low environmental energy and estuarine circulation causes accumulation of particulate matter enriched in heavy metals in the prodelta zone moderate anthropogenic influence on cu pb cd and cr concentrations has been recognised in the adige river the environmental fate of these elements is determined by the same natural processes and therefore accumulation in front of the river mouth occurs the elevated partitioning in the organic phase of the anthropogenically influenced elements could favour their mobility in different environmental conditions

late quaternary palaeoenvironmental evolution of the adriatic coastal plain and the onset of po river delta abstract despite abundant geologic literature about the po coastal plain stratigraphic architecture beneath modern po river delta is virtually unknown in this paper combined sedimentological micropalaeontological and geochemical investigations of three continuous cores cores 1 to 3 about 40 m thick enable for the first time the detailed reconstruction of subsurface stratigraphy in the po river delta area along with its late quaternary palaeoenvironmental evolution lowstand deposits formed during the last glacial maximum are expressed as a fining upward succession of fluvial channel and related overbank deposits capped by a stiff overconsolidated horizon above this unconformable surface the lower post glacial succession transgressive systems tract or tst is less than 7 m thick and includes a deepening upward succession of back barrier shoreface and inner shelf deposits on the other hand the overlying highstand systems tract is considerably thicker up to 27 m and comprises the bulk of recent delta progradation i e vertically stacked prodelta delta front and delta plain deposits stratigraphic correlations within early transgressive back barrier deposits show vertically stacked thin shallowing upward successions reflecting an internal subdivision of tst into small scale parasequences the homogeneous shallow marine clay that accumulated at the turnaround from transgressive to highstand conditions can be palaeontologically differentiated into two packages miliolidae dominated and ammonia cribroelphidium dominated reflecting open marine and river influenced conditions respectively timing of maximum marine ingression maximum flooding surface mfs is recorded within the open marine clays at about 5500 calibrated yr bp by minor changes in microfauna geochemical characterization of core 1 testifies that distinct changes in sediment provenance accompanied the palaeoenvironmental evolution of the study area under changing relative sea level conditions at lowstand times the study area was an alluvial plain under the influence of adige river as suggested by comparatively high ba al values within pre holocene fluvial deposits increasing upward values of cr al 2 o 3 and ni mg within tst suggest an increasing sediment provenance from the po river during early stages of transgression via the longshore drift the onset of modern age po delta in the study area is precisely identified in core 1 at 25 10 m depth and has a distinctive double signature in terms of microfaunal assemblages po river sediments are clearly marked by the development of a characteristic foraminiferal association dominated by the opportunistic species nonionella turgida a taxon typically abundant in the marginal zone of present northern adriatic sea mud belt po river deposits are also fingerprinted by a peculiar geochemical composition corresponding to maximum cr and ni concentrations

effects of volcanic activity on mire development case studies from hokkaido northern japan field stratigraphy and macrofossil composition of four mires in hokkaido northern japan were investigated to test whether tephra deposition induces long term vegetation shifts macroscopic tephras of known origin ranging from 0 5 to 25 cm in thickness were found in two or more of the study sites allowing correlation of the stratigraphic development of the mires major peat types and position of macroscopic mineral layers were determined in the field and selected cores were analysed by quantitative macrofossil analysis some macrofossil groups and the content of unidentifiable organic matter showed changes in the vicinity of tephra layers but they did not indicate a clear response pattern of the vegetation or the decomposition dynamics of plant material mosses were expected to be most strongly affected by tephra deposition but even in cases where tephra fell on sphagnum dominated vegetation no fundamental shifts to new plant communities were found this suggests that disturbance by widespread tep

a tale of two extinctions converging end permian and end triassic scenarios the end permian c 252 ma and end triassic c 201 ma mass extinction events are commonly linked to the emplacement of the large igneous provinces of the siberia traps and central atlantic magmatic province respectively accordingly scenarios for both extinctions are increasingly convergent and cross fertilization of ideas has become important here we present a synthesis of extinction scenarios based on a critical assessment of the available palaeontological sedimentological geochemical and geophysical evidence how similar were the extinction events what gaps exist in our understanding and how can a comparison of the events enhance our understanding of each event individually our focus is on the most important proximate kill mechanisms including climate change and atmospheric pollution increased soil erosion weathering and runoff forest dieback and the spread of pathogens and ocean temperature changes anoxia and acidification there is substantial evidence to suggest that very similar kill mechanisms acted upon late permian as well as late triassic ecosystems strengthening the hypothesis that the ultimate causes of the mass extinction events were similar

first measurements of the ionospheric plasma escape from mars before the phobos mission the magnetosphere of mars was relatively unexplored basically all data on the charged particle environment of mars had come from the soviet mars missions mars 2 3 4 and 5 here we report the results of an ion composition experiment on board the soviet phobos 2 spacecraft which allowed us to determine the loss of plasma from the ionosphere of mars because mars has a very small intrinsic magnetic field the ion outflow had been expected to be similar to that of venus surprisingly there were many similarities between the ionospheric outflow from mars and the earth the ion loss from mars results from both ion pick up that results from mass loading of the solar wind in the martian boundary layer and ionospheric o beams of energies up to several kev possibly from upward acceleration processes similar to those observed above the earth s auroral oval a preliminary estimate of the ionospheric outflow from mars indicates that the planet is losing oxygen at a rate of 3 x 1025 ions s 1 this corresponds to an evacuation of its present total atmospheric oxygen content contained in co2 and o2 in less than 100 million years

sulphur release from flood lava eruptions in the veidivotn grimsvotn and katla volcanic systems iceland book description humans have long marvelled at and feared the odorous and colourful manifestations of volcanic emissions and in some cases have harnessed them for their economic value the degassing process responsible for these phenomena is now understood to be one of the key factors influencing the timing and nature of volcanic eruptions moreover the surface emissions of these volatiles can have profound effects on the atmospheric and terrestrial environment and climate even more fundamental are the relationships between the history of planetary outgassing differentiation of the earth s interior chemistry of the atmosphere and hydrosphere and the origin and evolution of life this book provides a compilation of 23 papers that investigate the behaviour of volatiles in magma the feedbacks between degassing and magma dynamics and the composition flux and environmental atmospheric and climatic impacts of volcanic gas emissions

rjecina river sediments croatia from captured spring to polluted prodelta surface sediments fraction 6 ppm that might have the lowest toxic effects at the lower rjecina and in prodelta sediments pb was also present at slightly elevated concentrations 31 ppm that could cause such effects concentrations of zn in the prodelta correspond to those occurring in moderately polluted sediments 90 200 ppm in the prodelta sediments hg is slightly below toxicity threshold 1 ppm while ag is present at toxicity threshold 0 5 ppm or close to it rjecina river could act as a good illustrative example for behavior of toxic metals in allogenic karstic rivers in which accumulation of anthropogenically introduced pollutants usually occurs in their estuaries as a result of transport and deposition of fine particles

volcanism impact and mass extinctions incredible or credible coincidences massive continental volcanism and or bolide impacts are considered by many authors to have caused three major mass extinction events during the last 300 million years the end permian end cretaceous and end triassic extinctions however reevaluation of the frequency of bolide impacts and plume related flood basalt provinces indicates that both types of event occur much more frequently than mass extinctions and so in isolation may not be responsible for the largest extinctions furthermore the kill mechanisms associated with either flood basalts or impacts do not appear to be sufficiently powerful to cause worldwide collapse of ecosystems leading to the largest mass extinctions contemporaneous flood basalts and bolide impact may be prerequisites for the largest mass extinctions we present a statistical analysis of the probability of coincidence between volcanism and impact and show that three random coincidences of these events in the last 300 m y are likely no causal relationship between impact and volcanism is necessary the lesser mass extinctions on the other hand may not require juxtaposition of two such catastrophic events such coincidences occurring on more than three occasions during the last 300 m y become increasingly unlikely d 2004 elsevier b v all rights reserved

sedimentation of riverborne material in a shallow shelf sea adige river adriatic sea fast sedimentatio of fine grained riverborne suspended matter occurs in the prodelta zone of the adige river mouthdue to deceleration of river flow and spreading into the low energy environment in front of the river mouth process is probably associated with flocculation processin brackish water

acid loading from icelandic tephra falling on acidified ecosystems as a key to understanding archaeological and environmental stress in northern and western britain abstract this paper proposes that the additional acid loading brought about by the deposition of large quantities of acid aerosols from icelandic volcanic eruptions may be responsible for environmental stress and settlement abandonment postulated by previous authors for northern and western britain in the late 2nd millennium bc the mechanism is predicted to have been of significance only in those ecosystems that were already significantly acidified the paper discusses and counters suggestions that the volcanically induced climatic change was the principal mechanism for both an apparent abandonment of settlement over large areas of northern scotland and the stress experienced by oak trees growing on raised bogs in ireland

changes in stratospheric composition chemistry radiation and climate caused by volcanic eruptions the primary effect of a volcanic eruption is to alter the composition of the stratosphere by the direct injection of ash and gases on average there is a stratospherically significant volcanic eruption about every 5 5 years the principal effect of such an eruption is the enhancement of stratospheric sulphuric acid aerosol through the oxidation and condensation of the oxidation product h2804 following the formation of the enhanced aerosol layer observations have shown a reduction in the amount of direct radiation reaching the ground and a concomitant increase in diffuse radiation this is associated with an increase in stratospheric temperature and a decrease in global mean surface temperature although the spatial pattern of temperature changes is complex in addition the enhanced aerosol layer increases heterogeneous processing and this reduces the levels of active nitrogen in the lower stratosphere this in turn gives rise to either a decrease or an increase in stratospheric ozone levels depending on the level of chlorine loading

new 40ar 39ar and k ar ages of the viluy traps eastern siberia further evidence for a relationship with the frasnian famennian mass extinction abstract we present here new ages combining both k ar and 40 ar 39 ar techniques reinforcing the possible link between the viluy traps eastern siberia with the late devonian mass extinctions the viluy traps also referred to as the yakutsk large igneous province are associated with the breakup of the eastern margin of the siberian platform as a triple junction rift system with volcanic outcropping along the lena markha and viluy rivers and an initial volume of volcanic products of about one million cubic kilometers k ar ages obtained on seven samples from the viluy rift display values ranging from 366 5 to 381 5 ma with a mean age of 374 5 ma our new 40 ar 39 ar results display well defined step heating plateau ages ranging from 362 3 3 4 to 379 7 3 5 ma although most k ar and 40 ar 39 ar ages agree within about 1 uncertainty which reinforces the validity of the k ar ages obtained with the cassignol and gillot unspiked technique even in the paleozoic a slightly clearer scenario appears when only the 40 ar 39 ar ages are considered effectively they cluster in two different groups with weighted mean ages of 364 4 1 7 and 376 7 1 7 ma these ages support a multi phases emplacement of the viluy traps as is the case for many continental flood basalts because the age of the first volcanic phase is undistinguishable from recent determinations of the age of the frasnian famennian boundary our results further strengthen the hypothesis of a causal relationship between the two events the second phase of emplacement of the viluy traps occurred at the end of the devonian apparently slightly before the devonian carboniferous boundary finally except for the ordovician silurian extinction which remains to be associated with a volcanic province all major phanerozoic mass extinctions have been correlated with the emplacement of a cfb thereby reinforcing the possible causal link between these events