physical properties of tuffs from a scientific borehole at alban hills volcanic district central italy recent seismic swarms and hydrothermal activity suggest that the quaternary volcanic complex of the alban hills may pose a threat to the city of rome a 350 m scientific borehole was therefore drilled into this volcanic area to elucidate its inner structure for the first time wire line logs were run in the borehole in order to characterize the physical properties of the rocks and their variations with depth in particular a detailed sonic log was run to measure the p wave velocity from the well head down to 110 m to further investigate velocity changes we carried out laboratory measurements of p and s elastic wave velocities and fluid permeability at effective pressures up to 70 mpa during both increasing and decreasing pressure cycles on selected core samples representative of the main volcanic units specifically we studied samples from two pyroclastic units representative of two classes of volcanic deposits that are representative of the whole succession i a coarse grained well lithified facies pozzolane rosse unit containing abundant mm to cm lava clasts and crystals and ii a fine grained matrix supported pyroclastic deposit tufo pisolitico di trigoria unit with rare lithic lava clasts and sparse pumice elastic wave velocities reveal significant differences between units and indicate how within the same lithology the different degree of lithification and presence of clasts can affect significantly physical property values the mean laboratory value of the p wave velocity for pozzolane rosse and tufo pisolitico di trigoria units is respectively of 3 75 and 3 2 km s at an effective pressure equivalent to that at the depth at which the sonic velocity was measured under increasing effective pressure a profound influence on the transport properties is observed permeability ranges from the order of 10 18 m 2 for the pozzolane rosse unit to the order of 10 15 m 2 for the tufo pisolitico di trigoria unit in good agreement with the shallow aquifer circulating in the shallower units c 2008 elsevier b v all rights reserved

u th ages obtained by mass spectrometry in corals from barbados sea level during the past 130 000 years the study of the sea level record during the last glacial cycle has primarily proceeded indirectly by means of oxygen isotope measurements on foraminifera from deep sea sediments1 2 the direct approach of dating sea level indicators stagnated during the past decade mainly because the samples required to complete our knowledge of the past glaciations are below the present day sea level3 7 using the 14c ages of acropora palmata samples collected by drilling offshore the island of barbados fairbanks8 presented the first detailed chronology for the last deglaciation this radiocarbon chronology is limited to the past 30 kyr because of the short half life of 14c 5 730 yr we must therefore rely on other dating methods to obtain information for the whole last glacial cycle during the past four years 230th 234u dating of corals by thermal ionization mass spectrometry has been shown to be significantly more precise and accurate than the classical counting method9 14 we have used this technique to measure u th ages in coral samples from the barbados collection and from subaerially exposed outcrops see also ref 15 here we present results bearing on the sea level record for the past 130 000 years we conclude that the last deglaciation started 3 000 years earlier than previously thought and confirm that there were two surges in melt water8 at about 11 kyr and 14 kyr bp before present

pulsed uplift estimated from terrace elevations in the coast of rome evidence for a new phase of volcanic activity abstract the most recent phase of activity from the roman volcanoes since 45 ka has been interpreted to be the waning stage of the older explosive activity that peaked between 550 and 250 ka yet substantial regional uplift from approximately 250 ka suggests that magma chambers beneath the area are growing rather than shrinking we have estimated the uplift history of the region using radioisotopically and paleomagnetically constrained coastal terrace elevation data that allow us to correlate these terraces with marine oxygen isotopic stages 1 22 elevations have been corrected for glacio eustatic sea level change our study shows that over the last million years regional uplift of coastal terraces occurred in pulses that preceded volcanic activity at roughly 800 ka in the monti sabatini and 600 ka in the alban hills the recent pulse of uplift since 250 ka occurred primarily during a period of relative volcanic dormancy that lasted from 250 to 45 ka we hypothesize that the most recent volcanic activity since 45 ka may reflect the completion of magma chamber recharge suggesting the start of a new volcanic epoch it is also possible that the local tectonic stress field changed recently from one dominated by transpression to one dominated by extension allowing magma to more easily reach the surface via normal faults

single crystal 40ar 39ar dating of the olorgesailie formation southern kenya rift single crystal laser fusion sup 40 ar sup 39 ar analyses and several conventional bulk fusion sup 40 k sup 40 ar dates have been used to determine the age of volcaniclastic strata within the olorgesailie formation and of associated volcanic and sedimentary units of the southern kenya rift in the principal exposures along the southern edge of the legemunge plain the formation spans the interval from approximately 500 to 1 000 ka deposition continued to the east along the ol keju nyiro river where a tuff near the top of the formation has been dated at 215 ka in these exposures the formation is unconformably overlain by sediments dated at 49 ka a possible source for the olorgesailie tephra the ol doinyo nyokie volcanic complex contains as ash flow dated at approximately 1 ma extending the known age range of this complex to encompass that of virtually the entire olorgesailie formation in the legemunge plain these geologic examples illustrate the importance of the single crystal sup 40 ar sup 39 ar dating technique whereby contaminant altered or otherwise aberrant grains can be identified and eliminated from the determination of eruptive ages for reworked or altered pyroclastic deposits the authors have presented a computer modeling procedure based on an inverse isochron analysis thatmore promotes a more objective approach to trimming sup 40 ar sup 39 ar isotope data sets of this type less

calculation of ice velocities in the jakobshavn isbrae area using airborne laser altimetry abstract the ability to measure velocities of fast moving glaciers is essential to the understanding and interpretation of their dynamics and related processes this is especially important in the jakobshavn drainage basin of the greenland ice sheet where a significant portion of the ice sheet mass loss occurs and the iceberg calving rate is high in this article we present a method for using airborne laser altimetry data to determine surface velocities in portions of the jakobshavn drainage basin that have distinct elevation features by examining correlations between repeat elevation surveys the motion of these features the most distinct of which are crevasses is tracked results show that for areas with a standard deviation in elevation in excess of 1 m displacement of features can be tracked to a precision of 1 2 m and the corresponding velocities can be retrieved the maximum velocity of the jakobshavn isbrae at its calving front is found to be nearly 7 km yr 1 ice stream boundaries and flow patterns can also be observed in the derived velocity data

post stagnation behavior in the upstream regions of ice stream c west antarctica the region where two active tributaries feed into the now stagnant ice stream c isc west antarctica is thickening in this region we observe a correlation between faster ice flow the tributaries and elevated topography we conclude that stagnation of isc resulted in compression and thickening along the tributaries eventually forming a bulge on the ice sheet surface modern hydraulic potential gradients would divert basal meltwater from isc to ice stream b isb these gradients are primarily controlled by the bulge topography and so likely formed subsequent to trunk stagnation as such we argue against water piracy as being the cause for isc s stagnation kinematic wave theory suggests that thickness perturbations propagate downstream over time but that kinematic wave speed decreases near the stagnant trunk this and modest diffusion rates combine to trap most of the tributary fed ice in the bulge region using interferometric synthetic aperture radar velocity measurements we observe that half of the ice within isc s southern tributary flows into isb that flow pattern and other observations of non steady flow in the region likely result from stagnation induced thickening along upper isc combined with a longer period of thinning on upper isb if current trends in thickness change continue more ice from upper isc will be diverted to isb

structure and evolution of the sacrofano baccano caldera sabatini volcanic complex rome abstract sacrofano eruptive center in the eastern part of the sabatini volcanic complex was active between 0 5 and 0 09 m y ago the baccano geothermal area lies at the western edge of sacrofano caldera sedimentary substrata that form the reservoir for this geothermal system were exposed at the surface at the beginning of volcanic activity the volcanic history of the sacrofano center can be divided into three stages 1 1 construction of the sacrofano pyroclastic edifice by predominantly strombolian activity 2 2 collapse of sacrofano caldera following eruption of pyroclastic flows 3 3 development of the baccano explosive center at the western edge of sacrofano caldera and collapse of baccano caldera hydrovolcanic activity that began at the end of the first stage of sacrofano can be explained by a drop in the magma level in the conduit that relieved hydrostatic pressure in the aquifer as intense fracturing associated with caldera collapse penetrated the carbonate reservoir the entrapped water flowed towards the conduit to balance the pressure change the close link between tectonism and volcanism in the sacrofano center suggests that eruptions there may have been triggered by gravity faults related to regional tectonics

quaternary fluvial volcanic stratigraphy and geochronology of the capitoline hill in rome in and around rome coastal and fluvial sediments influenced by quaternary sea level changes interfinger with accurately datable highly potassic pyroclastic volcanic units we describe the complex internal geology of the capitoline hill for centuries a place of leading importance in ancient rome and more recently a focus of archaeological research outcrops and many new drill cores reveal at least four cycles of valley cutting and filling probably recording the history of the tiber river in response to changes in sea level single crystal 40 ar 39 ar dates on sanidine give ages of 518 6 413 5 and 353 2 ka for three prominent volcanic units filling separate paleovalleys the roman region offers the potential for direct age calibration of the quaternary sea level record

evidence for gas hydrate occurrences in the canadian arctic beaufort sea within permafrost associated shelf and deep water marine environments the presence of a wedge of offshore permafrost on the shelf of the canadian beaufort sea has been previously recognized and the consequence of a prolonged occurrence of such permafrost is the possibility of an underlying gas hydrate regime we present the first evidence for wide spread occurrences of gas hydrates across the shelf in water depths of 60 100 m using 3d and 2d multichannel seismic mcs data a reflection with a polarity opposite to the seafloor was identified 1000 m below the seafloor that mimics some of the bottom simulating reflections bsrs in marine gas hydrate regimes however the reflection is not truly bottom simulating as its depth is controlled by offshore permafrost the depth of the reflection decreases with increasing water depth as predicted from thermal modeling of the late wisconsin transgression the reflection crosscuts strata and defines a zone of enhanced reflectivity beneath it which originates from free gas accumulated at the phase boundary over time as permafrost and associated gas hydrate stability zones thin in response to the transgression the wide spread gas hydrate occurrence beneath permafrost has implications on the region including drilling hazards associated with the presence of free gas possible overpressure lateral migration of fluids and expulsion at the seafloor in contrast to the permafrost associated gas hydrates a deep water marine bsr was also identified on mcs profiles the mcs data show a polarity reversed seismic reflection associated with a low velocity zone beneath it the seismic data coverage in the southern beaufort sea shows that the deep water marine bsr is not uniformly present across the entire region the regional discrepancy of the bsr occurrence between the us alaska portion and the mackenzie delta region may be a result of high sedimentation rates expected for the central mackenzie delta and high abundance of mass transport deposits that prohibit gas to accumulate within and beneath the gas hydrate stability zone

monitoring ice sheet behavior from space satellite remote sensing has revolutionized ice sheet research a variety of instruments sensitive to different parts of the electromagnetic spectrum take what the human eye detects as a flat white desert and provide data sets rich in scientific information image based maps of ice sheets are becoming commonplace and have become an integral component of field work more than a pretty picture the digital character of the satellite data from these instruments has become fundamental to the production of elevation motion accumulation and reflectance data sets visible imagery shows the scientist a wealth of features that offer clues to the history and current behavior of the ice sheet radar and microwave imagery provide information from beneath the surface and have been used to estimate snow accumulation rates interferometry principles have recently been applied to measure surface topography and ice motion with unparalleled precision nonimaging instruments also keep a watchful eye monitoring the ice sheet for indications of growth or shrinkage further expansion of the uses of satellite data is anticipated in the future

stratigraphic and tectonic features of the middle pleistocene sedimentary and volcanic deposits in the area of rome italy the analysis of a large number of stratigraphic logs from boreholes as well as an extensive field survey suggests that the middle pleistocene sedimentary deposits in the area of rome can be subdivided into two groups each one characterised by a different stratigraphy and tectonic setting a north eastern sector corresponding to the eastern urban area of rome and a south western sector corresponding to the ponte galeria area in the north eastern sector the distribution of sediments is influenced by vertical block faulting showing a predominantly north south trend superimposed on a middle pleistocene ne sw extensional tectonic domain in the south western sector we suggest that the ponte galeria formation auct can be subdivided into two depositional sequences that can be linked to isotope stages 19 and 21 in addition a sedimentary hiatus is proposed at the top of the ponte galeria sequence it corresponds to the deposition of a continental succession in the north eastern sector before the emplacement of pyroclastic deposits from the colli albani and sabatini volcanic districts the correlation between these two depositional sequences that have been identified and the oxygen isotope time scale allowed us to extend our investigation across to the urban area of rome where we have recognised six sedimentary cycles all of pleistocene age which have been tentatively related to particular isotopes stages

40ar 39ar geochronology of roman volcanic province tephra in the tiber river valley age calibration of middle pleistocene sea level changes the close proximity of the roman volcanic province to the tyrrhenian sea coastline provides a unique opportunity to combine clastic stratigraphy with 40 ar 39 ar geochronology to constrain the timing of pleistocene sea level oscillations the main eruptions from the monti sabatini volcanic district occurred during the interval 560 280 ka and the alban hills volcanic district main eruptions span 560 350 ka the interfingering of volcanics from these two centers with fluvial and shallow marine sediments of the tiber river and delta provides a datable relative sea level record for this portion of middle pleistocene time we calculate the timing of glacial terminations using analytical errors only then assess age uncertainties that include analytical plus systematic errors the latter is required to compare 40 ar 39 ar ages with those from other dating methods terminations iii v and vi occur at 278 261 285 ka 95 confidence interval 430 422 442 ka and 534 520 541 ka respectively when only analytical uncertainties are used to calculate the ages of bracketing volcanic horizons the confidence interval expands significantly when full external errors are considered with predicted ages of 276 258 289 ka 430 416 448 ka and 533 512 548 ka for the terminations the resultant 40 ar 39 ar chronology is generally consistent with the deep sea 18 o record of sea level change tuned to earth9s obliquity cycle for glacial terminations vi v and iii in addition the 40 ar 39 ar constrained tiber river delta sea level record has the added benefit of identifying when coastal sections respond to complex multistep terminations

numerical model of the geothermal regime on the beaufort shelf arctic canada since the last interglacial 1 a finite element geothermal model is developed for the outer mackenzie delta beaufort sea shelf to predict permafrost evolution since the last interglacial 130 116 kabp cal the purpose is to reconcile sparse observations of the depth and extent of ice bonded permafrost with sediment properties and the paleoenvironment sea level curves determine as a function of time areas of the shelf that were subaerially exposed promoting permafrost aggradation and areas that were submerged promoting permafrost degradation assuming as a model starting point that a paleoclimate similar to today persisted through the last interglacial permafrost subsequently aggrades in depth and advances seaward from the present shoreline to the shelf slope bathymetric break by the last glacial maximum lgm 26 kabp cal modeled permafrost exhibits reduced growth in depth and seaward progression that correlate with early and middle wisconsin stillstands in sea level following the lgm and rise in sea level offshore permafrost degrades and permafrost base rises 100 m to its present depth of 600 m the offshore limit of modeled ice bonded permafrost lies at the 95 m isobath within 1 km of the bathymetric shelf slope break the model replicates features of offshore permafrost body observed seismically and demonstrates that warm outflow from the mackenzie river depresses the upper surface of offshore permafrost by tens of meters to the 20 m isobath although pleistocene permafrost predated the wisconsinan the model demonstrates that the paleoenvironment of the last 125 000 years is sufficient to develop the depth seaward extent and principal features of the permafrost body

mechanical properties of sand silt and clay containing tetrahydrofuran hydrate 1 the mechanical behavior of hydrate bearing sediments subjected to large strains has relevance for the stability of the seafloor and submarine slopes drilling and coring operations and the analysis of certain small strain properties of these sediments for example seismic velocities this study reports on the results of comprehensive axial compression triaxial tests conducted at up to 1 mpa confining pressure on sand crushed silt precipitated silt and clay specimens with closely controlled concentrations of synthetic hydrate the results show that the stress strain behavior of hydrate bearing sediments is a complex function of particle size confining pressure and hydrate concentration the mechanical properties of hydrate bearing sediments at low hydrate concentration probably 50 of pore space the behaviorbecomesmoreindependentofstressbecausethehydratescontrolbothstiffnessand strength and possibly the dilative tendency of sediments by effectively increasing interparticle coordination cementing particles together and filling the pore space the cementation contribution to the shear strength of hydrate bearing sediments decreases with increasing specific surface of soil minerals the lower the effective confining stress the greater the impact of hydrate formation on normalized strength

the villa senni eruption alban hills central italy the role of h2o and co2 on the magma chamber evolution and on the eruptive scenario abstract the villa senni eruption unit vseu belongs to the tuscolano artemisio phase of volcanic activity in the alban hills volcanic district the closest to rome of the recent or active volcanoes of central italy the most important products of this eruption are represented by pyroclastic flow deposits named lower and upper flow unit lfu and ufu respectively three main rock types form vseu as follows 1 juvenile k foiditic scoria clasts of the lfu 2 juvenile phonotephritic scoria clasts of the ufu and 3 holocrystalline phonotephritic lithic inclusions italites in the ufu on the basis of the chemistry mineralogy and petrography of the three studied rock types their phase relations have been discussed other petrologic constraints from laboratory melting experiments are presented and used to investigate the role of volatiles on the evolution of the magma chamber system some broad implications on withdrawal pattern are also presented it has been verified the lfu rock type can be obtained from a parental melt of ufu composition by a co2 controlled crystal liquid fractionation of a solid assemblage close in composition to that of italites because it can be proved that the storage of magma occurred at shallow depth within the mesozoic carbonate country rocks it is proposed that co2 diffusion originating from thermal decomposition of wall rock carbonates controlled the evolution trend of the melt at the periphery of the magma chamber whereas the inner part of the magma body retained the volatile component essentially h2o of the original melt the corresponding eruption model is therefore comprehensive of an early eruptive phase lfu rock type involving the more differentiated central magma bulb whereas the late eruptive phase ufu rock type tapped the more mafic peripheral magma the italite xenoliths are believed to represent the chilled margins of the magma chamber

satellite imagery of the onset of streaming flow of ice streams c and d west antarctica five overlapping landsat multispectral scanner satellite images of the interior of the west antarctic ice sheet were enhanced with principal component analysis high pass filtering and linear contrast stretching and merged into a mosaic by aligning surface features in the overlap areas the mosaic was registered to geodetic coordinates to an accuracy of about 1 km using the five scene centers as control points the onset of streaming flow of two tributaries of ice stream c and one tributary of ice stream d is visible in the mosaic the onset appears to occur within a relatively short distance less than the width of the ice stream typically at a subglacial topographic feature such as a step or ridge the ice streams extend farther up into the interior than previously mapped ice stream d starts about 150 km from the ice divide at an altitude of about 1500 m approximately halfway up the convex upward dome shape of the interior ice sheet ice stream d is relatively much longer than ice stream c possibly because ice stream d is currently active whereas ice stream c is currently inactive the grounded portion of the west antarctic ice sheet is perhaps best conceptualized as an ice sheet in which ice streams are embedded over most of its area with slow moving ice converging into fast moving ice streams in a widely distributed pattern much like that of streams and rivers in a hydrologic basin a relic margin appears to parallel most of the south margin of the tributary of ice stream d separated from the active shear margin by about 10 km or less for a distance of over 200 km this means there is now evidence for recent changes having occurred in three of the five major ice streams which drain most of west antarctica b c and d two of which b and d are currently active

physical conditions at the base of a fast moving antarctic ice stream boreholes drilled to the bottom of ice stream b in the west antarctic ice sheet reveal that the base of the ice stream is at the melting point and the basal water pressure is within about 1 6 bars of the ice overburden pressure these conditions allow the rapid ice streaming motion to occur by basal sliding or by shear deformation of unconsolidated sediments that underlie the ice in a layer at least 2 meters thick the mechanics of ice streaming plays a role in the response of the ice sheet to climatic change

satellite image derived velocity field of an antarctic ice stream the surface velocity of a rapidly moving ice stream has been determined to high accuracy and spatial density with the use of sequential satellite imagery variations of ice velocity are spatially related to surface undulations and transverse velocity variations of up to 30 percent occur such large variations negate the concept of plug flow and call into question earlier mass balance calculations for this and other ice streams where sparse velocity data were used the coregistration of images with the use of the topographic undulations of the ice stream and the measurement of feature displacement with cross correlation of image windows provide significant improvements in the use of satellite imagery for ice flow determination

strike slip faulting and block rotation a possible triggering mechanism for lava flows in the alban hills abstract it is suggested in this paper that two distinct tectonic triggers tapping different depths of a magma reservoir may be the cause of nearly contemporaneous eruptions of lava flows and ignimbrites in the alban hills the area between the alban hills and rome underwent alternating regional extensional and strike slip faulting during the middle pleistocene the geometries of the main structural dislocations in quaternary strata combined with a statistical analysis of drainage network trends show a structural pattern that is consistent with local strain partitioning in transpressive zones at strike slip fault bends superimposed on regional extension based on this analysis it is suggested that local clockwise block rotation between parallel n s strike slip faults might have generated local crustal decompression allowing relatively volatile free magma to rise from deep reservoirs beneath the alban hills triggering peripheral fissure lava flows in contrast the main ignimbrite eruptions appear to tap shallow volatile rich magma reservoirs and are controlled by extensional processes

seismic mapping and modeling of near surface sediments in polar areas a knowledge of permafrost conditions is important for planning the foundation of buildings and engineering activities at high latitudes and for geological mapping of sediment thicknesses and architecture the freezing of sediments is known to greatly affect their seismic velocities in polar regions the actual velocities of the upper sediments may therefore potentially reveal water saturation and extent of freezing we apply various strategies for modeling seismic velocities and reflectivity properties of unconsolidated granular materials as a function of water saturation and freezing conditions the modeling results are used to interpret a set of high resolution seismic data collected from a glaciomarine delta at spitsbergen the norwegian arctic where the upper subsurface sediments are assumed to be in transition from unfrozen to frozen along a transect landward from the delta front to our knowledge this is the first attempt to study pore fluid freezing from such data our study indicates that the p

the geochemistry of potassic lavas from vulsini central italy and implications for mantle enrichment processes beneath the roman region major and trace element and 143nd 144nd 0 51209 0 51216 and 87sr 86sr 0 70879 0 71105 isotope analyses are presented on a representative group of lavas from the vulsini district of the roman magmatic province three distinct series are identified the high k and low k series are similar to those described from other italian volcanoes while the third is represented by a group of relative ly undifferentiated leucite basanites which are thought to be near primary mantle melts major and trace element variations within the high k series are consistent with fractional crystallisation from a parental magma similar to the most magnesian leucitites crustal contamination resulted in an increase in 87sr 86sr with increasing fractionation but it was superimposed on magmas which had already inherited a range of incompatible element and isotope ratios from enrichment processes in the sub continental mantle these are reviewed using the available results from vulsini roccamonfina and ernici transition element abundances and ta yb ratios indicate that the pre enrichment mantle was similar to that of e type morb and that these elements were not mobilised by the enrichment process mixing calculations suggest that three components were involved in the enrichment process mantle comparable with the source of morb and two other components rich in trace elements one the low k component had high sr nd th ta and ba nb and no europium anomaly while the second had lower sr nd a negative europium anomaly and very high th ta it was also characterised by low nb ba and high rb ba ratios similar to those reported from phlogopite rich peridotite xenoliths the trace element enrichment processes are therefore thought to have occurred in the mantle wedge above a subduction zone with the trace element characteristics of the high k end member reflecting the subduction of sediments and the stabilisation of mantle phlogopite

permafrost active layer abstract this article discusses the properties and occurrence of an active layer al in the near surface of the lithosphere in glacial and periglacial environments this layer shows a seasonal variability in temperature as a result of the climate the al as classically understood seasonally thaws and freezes while in glacial environments it usually only reaches 0 c the definition of al is currently not consistent with the definition of permafrost even though both concepts usually appear linked for these terms to be comparable both should be defined based on temperature variability and not exclusively on phase change thus the al would be described not only as the upper section of perennially frozen ground presenting seasonal thaw freeze cycles 1 but as a layer presenting a seasonal variation in temperature 2 classical active layer can be thawed to a depth of approximately 2 8 cm the thickest al reaches over 20 m in the particularly favorable conditions al might be completely absent with the permafrost beginning at the ground surface in glacial and sub marine permafrost environments the al includes a layer of liquid water that seasonally accompanies the permafrost glaciers and ice sheets are usually devoid of the classical al in both cases the al is usually horizontal but in specific terrains such as sea shore cliffs or karst environments the al may have a vertical course and may even be reversed both al and permafrost are common in other frozen bodies in the solar system differing mainly in their thermal character

geochemical and geophysical evidence of methane release over the east siberian arctic shelf the east siberian arctic shelf esas which includes the laptev sea the east siberian sea and the russian part of the chukchi sea has not been considered to be a methane ch 4 source to hydrosphere or atmosphere because subsea permafrost which underlies most of the esas was believed first not to be conducive to methanogenesis and second to act as an impermeable lid preventing ch 4 escape through the seabed here recent observational data obtained during summer 2005 2006 and winter 2007 expeditions indicate the ubiquitous presence of elevated dissolved ch 4 and an elevated atmospheric ch 4 mixing ratio the ch 4 data were also analyzed together with high resolution seismic hrs data obtained by means of a sonic m 141 system consisting of a high resolution profiler and side scan sonar mounted in a towed fish during the transdrift x expedition 2004 onboard the r v yakov smimitskiy results show anomalously high concentrations of dissolved ch 4 up to 5 m and an episodically nongradually increasing atmospheric mixing ratio of ch 4 up to 8 2 ppm in some areas of the esas a most likely source is year round ch 4 release through taliks columns of thawed sediments within permafrost from seabed ch 4 reservoirs such as shallow hydrates and geological sources such releases occur not only within the areas underlain by fault zones but also outside of them this points to permafrost s failure to further preserve ch 4 deposits in the esas the total amount of carbon preserved within the esas as organic matter and ready to release ch 4 from seabed deposits is predicted to be 1400 gt release of only a small fraction of this reservoir which was sealed with impermeable permafrost for thousands of years would significantly alter the annual ch 4 budget and have global implications because the shallowness of the esas allows the majority of ch 4 to pass through the water column and escape to the atmosphere

characteristics of the active layer and shallow subsea permafrost a seasonal active layer associated with subsea permafrost was found in the sediments near the seabed of the beaufort sea near prudhoe bay alaska the active layer existed where sea ice was frozen to the seabed and also in shallow water where the under ice seawater salinities exceeded open water values initial freezing of the active layer was about coincident with the formation of new sea ice within 400 m of shore it appeared to freeze to an underlying ice bonded permafrost table ibpt farther offshore where this table is deeper the active layer thickness decreased with distance offshore and the layer was underlain by a talik relative ice contents in the active layer generally decreased with distance offshore were a few hundred parts per thousand ppt in the fall and ranged to more than 800 ppt in the spring seasonal changes in the bulk soil solution salinity showed that the partially frozen active layer redistributed salts during freezing was infiltrated by concentrated brines derived from the growth of sea ice and affected the timing of brine drainage to lower depths in the sediments these brines provide the salts required for thawing the underlying subsea permafrost in the presence of negative sediment temperatures the region near shore had a partially frozen transition layer just above the ibpt where the ice content increased and the brine content decreased with depth temperature at the ibpt is nearly constant beyond about 412 m to at least 3 5 km offshore at about 2 41 c implying relatively constant soil solution salinities there

seismicity seismogenic structures and crustal stress fields in the greater rome area central italy 1 instrumental seismicity of the greater rome area is analyzed using the most recent seismological database the aim of this study is to identify potential seismogenic structures responsible for the moderate seismicity that characterizes this sector where no surface faulting is expected on the basis of the absence of strong local earthquakes as evidenced by the 2000 year long historical record nevertheless in light of the great value and the high vulnerability of the architectural and monumental patrimony of rome even the occurrence of moderate events imposes a careful assessment of the hazard linked to the presence of active faults that are undetectable by means of classic geological field investigation seismic data here analyzed belong to the period 1997 2008 and show local magnitude ml ranging from 1 5 to 4 7 to better constrain the hypocentral depths we computed the vp vs ratio using a modified wadati method and the minimum 1 d velocity model that approximates the seismic structure of the study area moreover we applied a double difference hypocentral determination technique to improve earthquake locations most of the located seismicity appears to be concentrated within seven main clusters spatial distribution of the seismicity allowed us to identify several seismogenic structures corresponding to previously undetected or only supposed active faults the stress tensor obtained by inverting the focal mechanisms computed in this study is in agreement with the ne sw extensional tectonic stress active in the inner chain of the apennines although there is evidence of some local stress field heterogeneities

taliks in relict submarine permafrost and methane hydrate deposits pathways for gas escape under present and future conditions we investigate the response of relict arctic submarine permafrost and gas hydrate deposits to warming and make predictions of methane gas flux to the water column using a 2 d multiphase fluid flow model exposure of the arctic shelf during the last glacial cycle formed a thick layer of permafrost protecting hydrate deposits below however talik formation below paleo river channels creates permeable pathways for gas migration from depth an estimate of the maximum gas flux at the present time for conditions at the east siberian arctic seas is 0 2047 kg yr 1 m 2 which produces a methane concentration of 142 nm in the overlying water column consistent with several field observations for conditions at the north american beaufort sea the maximum gas flux at the present time is 0 1885 kg yr 1 m 2 which produces a methane concentration of 78 nm in the overlying water column shallow sediments are charged with residual methane gas after venting events sustained submergence into the future should increase gas venting rate roughly exponentially as sediments continue to warm studying permafrost associated gas hydrate reservoirs will allow us to better understand the arctic s contribution to the global methane budget and global warming

a sea level curve for the canadian beaufort shelf radiocarbon dated peat and peaty clay samples from geotechnical boreholes in the canadian beaufort continental shelf have been used to reconstruct a late quaternary relative sea level rsl curve the samples were carefully selected and evaluated using palynological techniques to ensure that reasonable age error limits could be given to each sample the dated samples were then related to the local geological setting using seismic profiles to determine the environment of deposition the resulting data show a rise of 140 m in rsl since 27 000 years bp a minor lowering of rsl at some time between 20 000 and 10 000 years bp is inferred from acoustic data contributions from basin subsidence sediment loading and consolidation account for 35 m of the total rsl rise the rsl curve is interpreted in the light of recent models of the isostatic and eustatic responses of the earth s crust at the laurentide ice sheet margin ice may have been more extensive during the middle wisconsinan than previously thought a

the 1989 1990 seismic swarm in the alban hills volcanic area central italy abstract a long seismic swarm has been recorded by a digital microseismic network that the istituto nazionale di geo fisica ing deployed from april 1989 to march 1990 in the alban hills quaternary volcanic region about 20 km southeast of rome the network consisted of thirteen digital stations equipped with four six component weak motion and strong motion sensors three three component and six vertical weak motion seismometers including both broad band and short period sensors more than 3000 earthquakes were detected during about one year of operation the data recorded during the sequence provided an unprecedented opportunity to resolve details of the seismogenic features of this area that has experienced earthquakes since the roman age although the temporal distribution of seismicity reveals a volcanic type swarm activity the recorded seismic signals show medium high frequency waveforms and clear s wave arrivals typical of tectonic earthquakes about 1100 earthquakes in a magnitude range between m d 1 5 and md 4 0 have been located the seismicity delineates a 6 12 km 2 nw se elongated region that corresponds to the area where the most recent 0 027 ma phreato magmatic activity took place almost no earthquakes occurred beneath the central cone and the eastern side of the caldera the seismicity is shallow and is mostly concentrated in two clusters that are offset laterally and are at sligthly different depths 3 5 and 4 6 km the fault plane solutions of the strongest earthquakes reveal a ne sw extension consistent with the regional orientation of the stress field along the apenninic chain as obtained by other seismo logical data

the roman eifel aqueduct archaeoseismological evidence for neotectonic movement at the transition of the eifel to the lower rhine embayment the lower rhine embayment and adjacent areas are characterised by neotectonic deformation resulting in differential crustal movement slip rates along the fault systems are very low 0 1 mm a significant earthquakes are known to have occurred in the past but the faulting behaviour is not adequately known which hampers the risks assessment we analysed the archaeological record of the largest roman aqueduct north of the alps this so called eifel aqueduct is 95 4 km long has its source in the eifel mountains and supplied the ancient city of cologne with calcareous fresh water the aqueduct crosses major faults of the lower rhine embayment perpendicular analyses of the aqueduct s gradient gives weak evidence for creep along the kirspenich fault resulting in differential movement of hanging and foot wall in the order of a few centimetres vertical offsets of 15 and 35 cm are documented exactly where the aqueduct crosses the holzheim fault system close to the city of mechernich here also structural damage of the aqueduct is recorded and archaeological evidence exists for repair works on the aqueduct we interpret these observations as well as the construction of a 4 km long deviation as necessary measures to keep the aqueduct operational after earthquake damage the timing of the event falls within the period of aqueduct operation which is reconstructed to be between 80 10 and 270 10 ce supporting evidence for earthquake activity within this period is seen in the roof collapse of the nearby kakus cave

high level triggers for explosive mafic volcanism albano maar italy abstract colli albani is a quiescent caldera complex located within the roman magmatic province rmp italy the recent via dei laghi phreatomagmatic eruptions led to the formation of nested maars albano maar is the largest and has erupted seven times between ca 69 33 ka the highly explosive nature of the albano maar eruptions is at odds with the predominant relatively mafic sio 2 48 52 wt foiditic k 2 o 9 wt composition of the magma the deposits have been previously interpreted as phreatomagmatic however they contain large amounts up to 30 vol of deep seated xenoliths skarns and all pre volcanic subsurface units all of the xenoliths have been excavated from depths of up to 6 km rather than being limited to the depth at which magma and water interaction is likely to have occurred suggesting an alternative trigger for eruption high precision geochemical glass and mineral data of fresh juvenile magmatic clasts from the small volume explosive deposits indicate that the magmas have evolved along one of two evolutionary paths towards foidite or phonolite the foiditic melts record ca 50 mixing between the most primitive magma and ca rich melt late stage prior to eruption a major result of our study is finding that the generation of ca rich melts via assimilation of limestone may provide storage for significant amounts of co 2 that can be released during a mixing event with silicate magma differences in melt evolution are inferred as having been controlled by variations in storage conditions residence time and magma volume

measuring snow and glacier ice properties from satellite satellite remote sensing is a convenient tool for studying snow and glacier ice allowing us to conduct research over large and otherwise inaccessible areas this paper reviews various methods for measuring snow and glacier ice properties with satellite remote sensing these methods have been improving with the use of new satellite sensors like the synthetic aperture radar sar during the last decade leading to the development of new and powerful methods such as sar interferometry for glacier velocity digital elevation model generation of ice sheets or snow cover mapping some methods still try to overcome the limitations of present sensors but future satellites will have much increased capability for example the ability to measure the whole optical spectrum or sar sensors with multiple polarization or frequencies among the methods presented are the satellite derived determination of surface albedo snow extent snow volume snow grain size surface temperature glacier facies glacier velocities glacier extent and ice sheet topography in this review emphasis is put on the principles and theory of each satellite remote sensing method an extensive list of references with an emphasis on studies from the 1990s allows the reader to delve into specific topics

a thermomechanical model of ice flow in west antarctica this study uses a three dimensional thermo mechanical model to investigate the internal flow dynamics of the west antarctic ice sheet wais the model allows ice thickness flow and temperature to interact freely its domain is prescribed as that of the present day grounded wais realistic present day climatic and topographical boundary conditions are employed the analysis of a series of experiments pays particular attention to the location and dynamics of concentrations of ice flow ice streams underlying topographic troughs are crucial in determining the strength and location of these concentrations of flow the flow pattern generated by subglacial troughs is made more distinct by the inclusion of ice flow temperature coupling the inclusion of sliding leads to the generation of limit cycles in the ice flow they are concentrated around the present day ice streams b and c of the siple coast and have a period of 5 to 10 ky there appears to be competition between several preferred ice flow pathways in this area the two end members of the flow regime are a strong ice stream c with a weakened ice stream a b complex and strong ice streams a and b with a dormant ice stream c ice streams appear to require ice discharges above a certain threshold in order to maintain frictional heat generation and fast flow individual ice streams can therefore interact through changes in catchment area size a reduction in catchment area reduces the volume of ice entering a stream and can cause stagnation as the amount of frictional heating falls

the effect of the extent of freezing on seismic velocities in unconsolidated permafrost we develop a model to relate velocities of seismic waves in unconsolidated permafrost is idealized as an assemblage of spherical quartz grains imbedded in a matrix composed of spherical water inclusions in ice the theory of kuster and toksoz based on wave scattering considerations is used to determine the effective elastic moduli and hence the wave speeds the hasin shtrikman theoretical bounds on the elastic moduli of heterogeneous materials and considerations establish the plausibility of the model the model predicts vp and vs to be decreasing functions of both the porosity and the water to ice ratio and the ratio vp vs to be an increasing function of these two parameters the theory is then applied to laboratory measurements of shear and compressional wave velocities in 23 permafrost samples from different sites in the beaufort sea mackenzie river valley and canadian arctic islands although no direct measurements were made of the extents of freezing in these samples the data are consistent w

changes in west antarctic ice stream velocities observation and analysis 1 we have produced a map of velocity covering much of the siple coast ice streams the map confirms earlier estimates of deceleration on whillans ice stream comparison with bed elevation data indicates that subglacial topography and the location of consolidated sediment play a strong role in determining the location of the tributaries feeding the ice streams force balance estimates based on these data indicate that the tributaries have beds nearly an order of magnitude stronger than those beneath many of the ice streams we have used a theoretical analysis to examine the controls on fast flow this analysis suggests that ice plains very wide ice streams are inherently unstable this instability may be responsible for the current deceleration on the ice plain of whillans ice stream and the shutdown of ice stream c 150 years ago thinning induced reductions in driving stress may also explain some of the observed deceleration particularly in upstream areas the active portions of ice stream c coincide well with the areas where we estimate that melt should be taking place current topography and inferences of large thickening following a shutdown suggest the upstream migration of a stagnation front that initiated at the ice plain uncertainty remains about the basal conditions on ice stream d while the basal resistance on ice stream e is large enough to ensure basal melting

minimum distribution of subsea ice bearing permafrost on the u s beaufort sea continental shelf 1 starting in late pleistocene time 19 ka sea level rise inundated coastal zones worldwide on some parts of the present day circum arctic continental shelf this led to flooding and thawing of formerly subaerial permafrost and probable dissociation of associated gas hydrates relict permafrost has never been systematically mapped along the 700 km long u s beaufort sea continental shelf and is often assumed to extend to 120 m water depth the approximate amount of sea level rise since the late pleistocene here 5 000 km of multichannel seismic mcs data acquired between 1977 and 1992 were examined for high velocity 2 3 km s 1 refractions consistent with ice bearing coarse grained sediments permafrost refractions were identified along 5 of the tracklines at depths of 5 to 470 m below the seafloor the resulting map reveals the minimum extent of subsea ice bearing permafrost which does not extend seaward of 30 km offshore or beyond the 20 m isobath

surface towed electromagnetic system for mapping of subsea arctic permafrost abstract sea level has risen globally since the late pleistocene resulting in permafrost bearing coastal zones in the arctic being submerged and subjected to temperature induced degradation knowing the extent of permafrost and how it changes over time is important for climate change predictions and for planning engineering activities in the arctic environment we developed a controlled source electromagnetic csem method to obtain information on the depth thickness and lateral extent of marine permafrost to operate in shallow water we used a surface towed electric dipole dipole csem system suitable for deployment from small boats this system was used to map permafrost on the arctic shelf offshore prudhoe bay alaska our results show significant lateral variability in the presence of permafrost with the thickest layers associated with a large river outflow where freshwater influx seems to have a preserving effect on relict subsea permafrost

subsea ice bearing permafrost on the u s beaufort margin 2 borehole constraints borehole logging data from legacy wells directly constrain the contemporary distribution of subsea permafrost in the sedimentary section at discrete locations on the u s beaufort margin and complement recent regional analyses of exploration seismic data to delineate the permafrost s offshore extent most usable borehole data were acquired on a 500 km stretch of the margin and within 30 km of the contemporary coastline from north of lake teshekpuk to nearly the u s canada border relying primarily on deep resistivity logs that should be largely unaffected by drilling fluids and hole conditions the analysis reveals the persistence of several hundred vertical meters of ice bonded permafrost in nearshore wells near prudhoe bay and foggy island bay with less permafrost detected to the east and west permafrost is inferred beneath many barrier islands and in some nearshore and lagoonal back barrier wells the analysis of borehole logs confirms the offshore pattern of ice bearing subsea permafrost distribution determined based on regional seismic analyses and reveals that ice content generally diminishes with distance from the coastline lacking better well distribution it is not possible to determine the absolute seaward extent of ice bearing permafrost nor the distribution of permafrost beneath the present day continental shelf at the end of the pleistocene however the recovery of gas hydrate from an outer shelf well belcher and previous delineation of a log signature possibly indicating gas hydrate in an inner shelf well hammerhead 2 imply that permafrost may once have extended across much of the shelf offshore camden bay

offshore permafrost decay and massive seabed methane escape in water depths 20 m at the south kara sea shelf 1 since the last glacial maximum 19 ka coastal inundation from sea level rise has been thawing thick subsea permafrost across the arctic although subsea permafrost has been mapped on several arctic continental shelves permafrost distribution in the south kara sea and the extent to which it is acting as an impermeable seal to seabed methane escape remains poorly understood here we use 1300 km of high resolution seismic data to map hydroacoustic anomalies interpreted to record seabed gas release on the west yamal shelf gas flares are widespread over an area of at least 7500 km2 in water depths 20 m we propose that continuous subsea permafrost extends to water depths of 20 m offshore and creates a seal through which gas cannot migrate this arctic shelf region where seafloor gas release is widespread suggests that permafrost has degraded more significantly than previously thought

modeling the evolution of climate sensitive arctic subsea permafrost in regions of extensive gas expulsion at the west yamal shelf thawing subsea permafrost controls methane release from the russian arctic shelf having a considerable impact on the climate sensitive arctic environment expulsions of methane from shallow russian arctic shelf areas may continue to rise in response to intense degradation of relict subsea permafrost here we show modeling of the permafrost evolution from the late pleistocene to present time at the west yamal shelf modeling results suggest a highly dynamic permafrost system that directly responds to even minor variations of lower and upper boundary conditions e g geothermal heat flux from below and or bottom water temperature changes from above permafrost scenarios of permafrost evolution show a potentially nearest landward modern extent of the permafrost at the west yamal shelf limited by 17 m isobaths whereas its farthest seaward extent coincides with 100 m isobaths the model also predicts seaward tapering of relict permafrost with a maximal thickness of 275 390 m near the shoreline previous field observations detected extensive emissions of free gas into the water column at the transition zone between today s shallow water permafrost 20 m the model adapts well to corresponding heat flux and ocean temperature data providing crucial information about the modern permafrost conditions it shows current locations of upper and lower permafrost boundaries and evidences for possible release of methane from the seabed to the hydrosphere in a warming arctic

evidence of active tectonics on a roman aqueduct system ii iii century a d near rome italy abstract in this paper we describe evidence of strong tectonic deformation affecting two aqueducts of roman age ii iii century a d the channels are located approximately 20 km northeast of rome along the ancient via tiburtina brittle and ductile deformation affects these two structures including extensional joint systems ne oriented faults and horizontal distortion this deformation is consistent with right lateral movement on major n striking faults and represents the first evidence that tectonic deformation took place in historical times in the vicinity of rome with local strike slip movement superimposed on a regional extensional fault system

permafrost associated natural gas hydrate occurrences on the alaska north slope abstract in the 1960s russian scientists made what was then a bold assertion that gas hydrates should occur in abundance in nature since this early start the scientific foundation has been built for the realization that gas hydrates are a global phenomenon occurring in permafrost regions of the arctic and in deep water portions of most continental margins worldwide in 1995 the u s geological survey made the first systematic assessment of the in place natural gas hydrate resources of the united states that study suggested that the amount of gas in the gas hydrate accumulations of northern alaska probably exceeds the volume of known conventional gas resources on the north slope researchers have long speculated that gas hydrates could eventually become a producible energy resource yet technical and economic hurdles have historically made gas hydrate development a distant goal this view began to change in recent years with the realization that this unconventional resource could be developed with existing conventional oil and gas production technology one of the most significant developments was the completion of the bpxa doe usgs mount elbert gas hydrate stratigraphic test well on the alaska north slope which along with the mallik project in canada have for the first time allowed the rational assessment of gas hydrate production technology and concepts almost 40 years of gas hydrate research in northern alaska has confirmed the occurrence of at least two large gas hydrate accumulations on the north slope we have also seen in alaska the first ever assessment of how much gas could be technically recovered from gas hydrates however significant technical concerns need to be further resolved in order to assess the ultimate impact of gas hydrate energy resource development in northern alaska

basal friction of ice stream e west antarctica we use surface velocity derived from sequential landsat imagery and a control method to estimate the basal friction distribution of a major west antarctic ice stream the area averaged basal stress is approximately 1 4 10 4 pa or about 29 of the area averaged driving stress of 4 9 10 4 pa uncertainty of the derived area averaged basal stress is difficult to assess and depends primarily on spatial variation of the flow law rate factor in the constitutive law spatial variation associated with depth averaged temperature variation gives an uncertainty of approximately 10 3 pa approximately 60 of the ice stream has a basal stress magnitude less than 10 4 pa and approximately 30 has less than 10 3 pa these characteristics suggest the presence of a mechanically weak water charged subglacial till small scale sticky spots where basal friction exceeds the area averaged driving stress are scattered irregularly across the subglacial regime and comprise approximately 15 of the ice stream area sticky spots cluster in regions where landsat imagery suggests structural features in the underlying bedrock

crustal structure and moho depth profile crossing the central apennines italy along the n42 parallel 1 we present results from a teleseismic receiver function study of the crustal structure in the central apennines italy data from 15 stations deployed in a linear transect running along the n42 parallel were used for the analysis a total number of 364 receiver functions were analyzed the crustal structure has been investigated using the neighborhood algorithm inversion scheme proposed by sambridge 1999a obtaining crustal thicknesses bulk crustal vp vs ratio and velocity depth models in each inversion the degree of constraint of the different parameters has been appraised by the bayesian inference algorithm by sambridge 1999b the study region is characterized by crustal complexities and intense tectonic activity recent volcanism orogenesis active extensional processes and these complexities are reflected in the receiver functions however the relatively close spacing among the seismometers about 20 km helped us in the reconstruction of the crustal structure and moho geometry along the transect crossing the apennines from west to east the moho depth varies by more than 20 km going from a relatively shallow depth around 20 km on the tyrrhenian side deepening down to about 45 km depth beneath the external front of the apenninic orogen and rising up again to about 30 km depth in correspondence of the adriatic foreland despite the strong variability of the crustal thickness the average crustal vs values show little variation along the transect fluctuating around 3 km s the average vp values obtained from the vs and vp vs are generally lower than 6 km s

a newly emerged august 2013 artificially triggered fumarole near the fiumicino airport rome italy abstract early in the morning of 24 august 2013 following by hours the drilling of a shallow borehole in the same spot a new fumarole producing emissions of co2 rich gas water and mud suddenly appeared at a crossroad along the fenced area of the fiumicino international airport of rome italy similar episodes have been scientifically documented or simply reported in recent and past years to understand why gases are easily entrapped in the shallow subsurface of the fiumicino area we used five borehole cores drilled by us analyzed the stratigraphy of these and other nearby cores acquired a 2d seismic refraction tomogram and performed chemical and isotopic analyses of water samples collected from aquifers intercepted by two drilled boreholes our boreholes were realized with proper anti gas measures as while drilling we recorded the presence of pressurized gases at a specific permeable gravel level results show that in the study area gases become mainly entrapped in a mid pleistocene gravel horizon at about 40 50 m depth this horizon contains a confined aquifer that stores the endogenous upwelling gases the gravel is interposed between two silty clayey units the lower unit very hard and overconsolidated is affected by fractures that allow ascending gases to bypass the otherwise impermeable shale permeate the gravel and dissolve into the aquifer in contrast the upper unit is impermeable to fluids and seals the gas pressurized aquifer which therefore constitutes a source of hazard during human activities such as well drilling quarrying and various building related excavations as the stratigraphy of the fiumicino area is very common in large portions of the densely populated roman area and as the adjacent volcanic districts are hydrothermally active we conclude that phenomena similar to that observed at fiumicino could again occur both at fiumicino and elsewhere in the surrounding region as a prompt confirmation of our conclusion we signal that while writing this paper new artificially triggered degassing phenomena occurred off fiumicino in connection with the construction of the new harbor

tectonic evolution of the internal sector of the central apennines italy a wide sector of the internal portion of the central apennines which comprises the southern lepini mtns up to the northern simbruini mtns has been investigated through detailed field mapping and integrated with structural analyses a few small productive oil fields and a large number of hydrocarbon seeps and oil impregnations are located in this sector this area offers good opportunities for testing the use of structural fieldwork methodologies in order to highlight oil migrating paths from triassic source rocks and prospecting chances for oil field exploitation the main stages of the structural evolution of the area took place after deposition of the foredeep sediments frosinone fm i e after late tortonian under a stress field characterised by a ne sw trending s1 which was responsible for the early emplacement of major thrust faults present in the area the messinian early pliocene thrust top basin deposits allowed the reconstruction of an in sequence evolution of the thrust system the development of out of sequence thrusting post dates these structures leading to a further strong shortening phase in the area during the pliocene this phase is characterised by a roughly nne ssw trending s1 some peculiar tectonic features evidenced by thrust faults with younger over older relationships and an inversion of the original stacking of thrust sheets developed during this phase successively a block faulting tectonic mainly with ne sw extension stress field occurred and dismembered the compressive tectonic edifice later on up to the middle pleistocene n s to nne ssw trending dextral strike slip faults also acted in the area associated to the strikeslip tectonics are local volcanic centres as well as necks whose compositions show a mantle origin thus indicating deep seating and a possible lithospheric significance of these structures in the light of this study the reduced extension of the productive oil area as well as the spotting of oil seeps may indicate that the migration conditions are not tied to well defined structures but that likely the cross cutting points among structures facilitate the conditions for an upwards rising of oil these conditions in particular are achieved at least in two cases 1 where the late triassic source rocks do not have great depth due to normal or reverse faults or 2 at a major depth when encountered by transcurrent oblique roughly n s trending faults in both cases oil can easily migrate along the damage zone associated to the fault plane q 2004 elsevier ltd all rights reserved

ice dynamics at the mouth of ice stream b antarctica field data collected at the mouth of ice stream b show that the flow dynamics of this region are distinctly different than either the major portion of the ice stream upstream or the ice shelf downstream surface slopes in this region are as low as ice shelf surface slopes yet with the exception of patches of ice which may be floating the ice is grounded basal shear stress is negligible the resistance to flow being partitioned between shear at the sides and longitudinal gradients of longitudinal and transverse stress the surface is generally crevasse free features similar to ice rises are observed upstream of the grounding line their origin is uncertain but they move at velocities comparable to the surrounding ice the flow is laterally extensive and longitudinally compressive but there are large local variations of the strain rate from the regional trends the boundary between the two major tributaries to ice stream b followed with the radar is characterized by a band of strain rates much smaller than average detailed measurements at the downstream b network highlight this local variability of strain rates but confirm that there is a strong correlation between surface topography and strain rates the strain rates indicate that the undulating topography is locally generated the lower elevation ice is thicker and moves faster a velocity profile across the crevassed northern margin shows that the decrease of velocity toward the edge is nearly linear a calculation of ice stream discharge at this location agrees closely with two rather rough estimates of balance flux and is considerably larger than a third estimate the discharge of ice stream b does not appear to be significantly out of balance with published estimates of total ice accumulation within the present catchment basin

the history of the monti sabatini and alban hills volcanoes groundwork for assessing volcanic tectonic hazards for rome abstract the volcanic rocks of rome provide chronostratigraphic constraint that is of use to geologists archaeologists and paleontologists identifying the areal distribution of these rocks their mode of emplacement and a detailed chronology of the eruptive events also is crucial for assessing local natural hazards in a volcanic tectonic context and for recognizing whether the volcanoes may erupt again in the future we have identified and dated many of the volumetrically significant eruptive units from the monti sabatini and alban hills colli albani and propose a formalized volcanic stratigraphy for rome it is probable that seismic events triggered some eruptions as several ignimbrites from the two volcanoes have statistically indistinguishable ages following a 200 kyr period of dormancy that was coincident with a pulse of regional uplift the alban hills appears to have begun recently circa 45 ka a new eruptive cycle therefore accurate assessment of volcanic tectonic hazards and estimation of possible future volcanic activity is necessary for the safety of the five million people living near these volcanoes

performance of landsat 8 operational land imager for mapping ice sheet velocity landsat imagery has long been used to measure glacier and ice sheet surface velocity and this application has increased with increased length and accessibility of the archive the radiometric characteristics of landsat sensors however have limited these measurements generally to only fast flowing glaciers with high levels of surface texture and imagery with high sun angles and cloud free conditions preventing wide area velocity mapping at the scale achievable with synthetic aperture radar sar the operational land imager oli aboard the newly launched landsat 8 features substantially improves radiometric performance compared to preceding sensors enhancing performance of automated repeat image feature tracking rift for mapping ice flow speed in order to assess this improvement we conduct a comparative study of oli and the landsat 7 enhanced thematic mapper plus etm performance for measuring glacier velocity in a range of surface and atmospheric conditions to isolate the effects of radiometric quantization and noise level we construct a model for simulating etm imagery from oli and compare rift results derived from each we find that a nonlinearity in the relationship between etm and oli radiances at higher brightness levels results in a particularly large improvement in rift performance over the low textured interior of the ice sheets as well as improved performance in adverse conditions such as low sun angles and thin clouds additionally the reduced noise level in oli imagery results in fewer spurious motion vectors and improved rift performance in all conditions and surfaces we conclude that oli imagery should enable large area ice sheet and glacier mapping so that its coverage is comparable to sar with a remaining limitation being image geolocation

intrapermafrost gas hydrates from a deep core hole in the mackenzie delta northwest territories canada visible gas hydrate and possible pore space hydrate samples have been recovered for the first time in north america from within ice bonded permafrost in a 451 m deep core hole in the mackenzie delta northwest territories canada the visible hydrate was found as thin icelike layers that released methane gas initially upon retrieval but stabilized for up to 4 h at atmospheric pressure conditions and subfreezing temperatures the temporary stabilization of hydrate samples is attributed to the self preservation phenomenon described by others on the basis of laboratory studies high methane concentrations in well ice bonded sediments and gas releases suggest that pore space hydrate may be found at depths as shallow as 119 m geochemical and isotopic determinations suggest that the methane hydrate observed in the core hole is biogenic microbial in origin

the integration of jers 1 and ers sar in differential interferometry for measurement of complex glacier motion complex glacier motion in the grove mountains region antarctica is measured using four pass differential synthetic aperture radar sar interferometry insar the components of the motion vector field are resolved using a 44 day separation japanese earth resources satellite 1 jers 1 insar pair and a european remote sensing satellite 1 2 ers 1 2 tandem insar pair the 44 day temporal baseline provides the sensitivity required to observe the range of ice motion around 8 10 m a 1 and the 1 day short baseline provides the best choice for glacier digital elevation model reconstruction it is remarkable that the scattering field of the jers 1 pair remained coherent over the long time interval and the interferometric fringes are clear the overall ice flow is from east to west downslope and towards lambert glacier the regional flow is obstructed by nunataks extending north south with two wide gaps two narrow glaciers flow past the nunataks and rejoin each other at the downstream end regional morphology and the resolved flow in the grove mountains area suggests that ice flow is channeled throughout this eastern flank of lambert glacier

remote sensing of ice motion in antarctica a review abstract the antarctic ice sheet holds 91 of the global ice mass making it the biggest potential contributor to global sea level rise in order to evaluate the ice sheet s present and future response to global climate change detailed information about spatial and temporal ice mass dynamics is required while ice sheet surface mass balance can be estimated from regional climate models ice discharge is often determined from spaceborne measurements of ice thickness and ice motion at selected flux gates the retrieval of ice motion is not only critical for analysing the rate of ice transport into the ocean but also for investigating the spatial and temporal pattern or the driving forcings of antarctic ice flow dynamics this study provides a comprehensive review of state of the art spaceborne ice velocity measurements in antarctica based on 201 scientific papers published over the last three decades our analysis revealed a dominant interest in local and regional scale investigations yet the launch of the ers 1 2 and radarsat 1 sar satellites in the 1990s dramatically increased data coverage over the antarctic continent and enabled the first circum antarctic velocity product to be published in the late 2000s in recent years the improved imaging capabilities of landsat 8 led to a shift towards using mainly optical satellite data and enabled great advances in circum antarctic velocity mapping data from the currently operating sentinel 1 2 missions was applied in fewer studies but will play a crucial role in future ice motion studies e g as part of esa cci projects in addition we found a growing interest in high temporal resolution velocity change analyses based on the reviewed studies we moreover summarized the highly dynamic and locally variable flow pattern over the antarctic continent being in accordance with varying local and regional driving mechanisms despite the great advances in spaceborne ice velocity mapping in antarctica we report some major drawbacks and discuss future challenges and requirements to start with our study uncovered strong variations regarding the spatial availability of investigations while we found an aggregation of studies over selected glaciers we report a major lack of studies in all three antarctic sectors additionally many velocity datasets were created with strongly heterogeneous output parameters and were provided at coarse temporal resolution or at point based measurement locations only future studies should consequently aim at creating more uniform ice motion products at defined spatial and temporal coverage and resolution standards and at analysing particularly the least studied glaciers

subglacial sediments as a control on the onset and location of two siple coast ice streams west antarctica laterally continuous subglacial sediments are a necessary component for ice streaming in the modern onset regions of the ice streams draining the siple coast of west antarctica on the basis of new seismic data combined with previous results we present geophysical results from seismic reflection and refraction experiments in the upper reaches of ice streams c and d that highlight continuous sedimentary basins within and upstream of the current onset regions of both ice streams with streaming ice overlying these sedimentary packages the subglacial environment changes from no sediment to discontinuous sediment to continuous sediment cover along a longitudinal profile from the ice sheet to tributary c1b along this same profile we observe a speedup of ice flow and then full development of the ice stream tributary ice stream d flows above a thick sedimentary package with an uppermost low seismic velocity zone indicative of soft till and the upglacier and lateral extensions of ice stream d are tightly constrained by the extent of continuous sediments the inland termination of these sediments suggests that future migration of high velocity low shear stress ice flow in these regions appears unlikely

integrated geochronology of acheulian sites from the southern latium central italy insights on human environment interaction and the technological innovations during the mis 11 mis 10 period abstract we have explored the multimethod approach combining 40ar 39ar on single crystal esr on bleached quartz and esr u series on teeth to improve the age of four neighbours acheulian sites of the frosinone province latium italy fontana ranuccio cava pompi pofi isoletta and lademagne ages obtained by the three methods are in mutual agreement and confirm the potential of dating with confidence middle pleistocene sites of italy using these methods at fontana ranuccio the 40ar 39ar age 408 10 ka full external error at 2 obtained for the archaeological level unit fr4 and geochemical analyses of glass shards performed on the unit fr2a layer allow us to attribute the studied volcanic material to the pozzolane nere volcanic series a well known caldera forming event originated from the colli albani volcanic district these new data ascribe the fontana ranuccio site as well as the eponym faunal unit to the climatic optimum of marine isotope stage mis 11 ages obtained for the cava pompi isoletta and lademagne sites cover a relatively short period of time between 408 ka and 375 ka spanning mis 11 climatic optimum to the mis 11 10 transition analysis of small collections of lithic industries bifacial tools and small cores technologies from isoletta lademagne and the neighbour site of ceprano campogrande shows common technical strategies for the period comprised between mis 11 and mis 9 410 325 ka such as the elaboration of flaked elephant bone industries found over the whole latium region however some features found only in the frosinone province area like large sized bifaces suggest particular regional behaviours the presence of one levallois core in the oldest layer of lademagne i e 405 9 ka suggests a punctual practice of this technology also proposed as early as mis 10 11 in the neighbour site of guado san nicola molise in central italy

assessing the volcanic hazard for rome 40ar 39ar and in sar constraints on the most recent eruptive activity and present day uplift at colli albani volcanic district we present new 40ar 39ar data which allow us to refine the recurrence time for the most recent eruptive activity occurred at colli albani volcanic district cavd and constrain its geographic area time elapsed since the last eruption 36 kyr overruns the recurrence time 31 kyr in the last 100 kyr new interferometric synthetic aperture radar data covering the years 1993 2010 reveal ongoing inflation with maximum uplift rates 2 mm yr in the area hosting the most recent 200 ka vents suggesting that the observed uplift might be caused by magma injection within the youngest plumbing system finally we frame the present deformation within the structural pattern of the area of rome characterized by 50 m of regional uplift since 200 ka and by geologic evidence for a recent 2000 years switch of the local stress field highlighting that the precursors of a new phase of volcanic activity are likely occurring at the cavd

age of the ponta grossa dike swarm brazil and implications to parana flood volcanism the ponta grossa dike swarm pgds occurs in a nw trending 200 km wide zone exposed just east of the parana basin in southeastern brazil the predominantly basaltic dikes intrude crystalline basement paleozoic mesozoic sediments and rarely flows of the parana etendeka flood volcanic province pep the pgds resembles the failed arm of a rift rift rift triple junction related to the separation of south america and africa detailed geochemical studies of the dikes including major minor trace element and sr nd isotopic analyses indicate that they probably represent feeders for the voluminous phase of flood volcanism represented by relatively uncontaminated predominantly high tio2 lavas of the northern pep where lava accumulations reach 1700 m thick 40ar 39ar stepwise degassing data using both laser and radiofrequency induction furnace on plagioclase separates from eighteen dikes and one sill yield seventeen plateau ages three are between 120 7 1 3 ma and 125 8 0 6 ma and fourteen are clustered between 129 2 0 4 ma and 131 4 0 5 ma isochron ages are not significantly different from the plateau ages and plateau ages are adopted in all but two cases as being the most accurate age estimates the age probability distribution for the dominant pulse 131 4 0 4 to 129 2 0 4 ma shows a pronounced peak at 130 5 ma this distribution probably reflects the magma production history in the region the new geochronologic data are consistent with conclusions based on paleomagnetic and chemical stratigraphic data that the pgds is younger than the volumetrically dominant majority of volcanism in the southern pep which occurred at 133 132 ma the younger commonly ne trending dikes may reflect the initiation of full drift which was coincident with major basin development in the adjacent continental borderland at 125 120 ma the pgds may indeed represent the failed arm of a rift rift rift triple junction but the triple junction did not coincide exactly in time or space with the site that would be inferred for plume impact

recent uplift of the alban hills volcano italy evidence for magmatic inflation first order leveling surveyed in 1951 and 1994 along a line across the alban hills volcano reveals maximum vertical uplift of 30 cm average of 7 mm yr in the region of geologically recent 0 020 0 030 ma explosive activity the uplifted region corresponds to an area where seismic activity is concentrated at depths of 3 6 km uplift exceeding 10 cm is observed over a 14 km wide zone in the center of a 40 km long line with the deformation tapering to zero at both ends of the line data from a few sparse older benchmarks measured in 1891 and 1927 suggest that the deformation in the first half of this century was very small compared to the period 1951 1994 the observed uplift together with increased seismic activity suggest that recent magma injection has occurred in the upper crust beneath the alban hills volcano

reconstruction of the mis 5 5 5 3 and 5 1 coastal terraces in latium central italy a re evaluation of the sea level history in the mediterranean sea during the last interglacial abstract we present a geomorphological stratigraphical and geochronological study reconstructing a suite of paleo surfaces in a 200 km long coastal sector of the central tyrrhenian sea between argentario and circeo promontories identification of the near shore deposits associated with these paleo surfaces allow us to define corresponding marine terraces and paleo sea levels 40ar 39ar and esr u th geochronologic constraints on key deposits provide correlation with the terraces previously recognized in the coast of central latium refining their correlation with the marine isotopic stages results of this study enable us to propose a re assessment of the ages for the sea level markers of mis 5 5 5 3 5 1 in the central tyrrhenian sea suggest that a continuous tectonic uplift with an average rate of 0 224 mm yr affects the latium coast since 200 ka provide new evidence for a mis 5 5 paleo sea level marker occurring at 35 m a s l on the coastal sector extending from montalto di castro to latina while it possibly drops down and connects to a paleo sea level ranging 10 5 m between monte circeo and gaeta previously attributed to this interglacial discussing possible evidence of similar elevation of the sea level during mis 5 5 5 3 and 5 1 interglacials in the tyrrhenian sea compare this datum with those from the western pacific and several coral reefs where the differences with respect to tectonically stable regions were attributed either to tectonics or to the glacial isostatic adjustment showing that the presented record of sea level markers may have a strong impact on modeling the post glacial effects in the mediterranean sea and on the paleoclimatic and paleoceanographic studies in this region

subsea ice bearing permafrost on the u s beaufort margin 1 minimum seaward extent defined from multichannel seismic reflection data subsea ice bearing permafrost ibpf and associated gas hydrate in the arctic have been subject to a warming climate and saline intrusion since the last transgression at the end of the pleistocene the consequent degradation of ibpf is potentially associated with significant degassing of dissociating gas hydrate deposits previous studies interpreted the distribution of subsea permafrost on the us beaufort continental shelf based on geographically sparse datasets and modeling of expected thermal history the most cited work projects subsea permafrost to the shelf edge 100 m isobath this study uses a compilation of stacking velocity analyses from 100 000 line km of industry collected multichannel seismic reflection data acquired over 57 000 km2 of the us beaufort shelf to delineate continuous subsea ibpf gridded average velocities of the uppermost 750 ms two way travel time range from 1475 to 3110 m s 1 the monotonic cross shore pattern in velocity distribution suggests that the seaward extent of continuous ibpf is within 37 km of the modern shoreline at water depths 25 m these interpretations corroborate recent beaufort seismic refraction studies and provide the best margin scale evidence that continuous subsea ibpf does not currently extend to the northern limits of the continental shelf this article is protected by copyright all rights reserved

methane release from pingo like features across the south kara sea shelf an area of thawing offshore permafrost the holocene marine transgression starting at 19 ka flooded the arctic shelves driving extensive thawing of terrestrial permafrost it thereby promoted methanogenesis within sediments the dissociation of gas hydrates and the release of formerly trapped gas with the accumulation in pressure of released methane eventually triggering blowouts through weakened zones in the overlying and thinned permafrost here we present a range of geophysical and chemical scenarios for the formation of pingo like formations plfs leading to potential blowouts specifically we report on methane anomalies from the south kara sea shelf focusing on two plfs imaged from high resolution seismic records a variety of geochemical methods are applied to study concentrations and types of gas its character and genesis plf 1 demonstrates ubiquitously low methane concentrations 14 2 55 3 ppm that are likely due to partly unfrozen sediments with an ice saturated internal core reaching close to the seafloor in contrast plf 2 reveals anomalously high methane concentrations of 120 000 ppm where frozen sediments are completely absent the methane in all recovered samples is of microbial and not of thermogenic origin from deep hydrocarbon sources however the relatively low organic matter content 0 52 1 69 of seafloor sediments restricts extensive in situ methane production as a consequence we hypothesize that the high methane concentrations at plf 2 are due to microbial methane production and migration from a deeper source

the bag tephra a widespread tephrochronological marker in middle europe chemical and mineralogical investigations the bag tephra is a widespread tephra layer interbedded in quaternary loess deposits along the danubian valley of hungary and slovakia its age is poorly defined between 788 and 380 ka b p the glass and mineral composition micropumice clasts of phono tephrite and blocky shards of tephri phonolite associated with two kinds of clinopyroxene fassaitic diopside and salite is very distinctive this tephra could be used as a chronological marker as soon as its age is refined the probable origin is the middle italian volcanic area

a review of the stratigraphy of rome italy according to geochronologically and paleomagnetically constrained aggradational successions glacio eustatic forcing and volcano tectonic processes abstract in this paper we provide a critical review of the studies conducted on the geology of rome since the first half of the 20th century aimed at presenting an updated state of the art on the stratigraphy of this area following this introductory summary we present a complete reconstruction of the geological evolution and the resulting chrono litho stratigraphic setting of the greater area of rome according to a series of works that in the last 20 years have adopted an innovative methodological approach based on the conceptual model of aggradational successions deposited in response to sea level rise during the glacial terminations and on the strict geochronologic constraints to the sedimentary record achieved by paleomagnetic investigation of clay sections and 40ar 39ar dating of interbedded volcanic materials we also present a complete overview on the chronostratigraphy of the two volcanic districts of colli albani and monti sabatini located se and nw of rome respectively that has been achieved integrating the field work with the large number of radiometric ages provided in these years on their eruptive products moreover we propose a revised stratigraphic column to compare the most recent official 1 50 000 and 1 10 000 geologic mapping of rome which is intended as a tool of correlation for an international audience of quaternary scientists to approach the study of this area a detailed discussion of the proposed revisions is also provided as supplementary information to this paper

surface morphology and internal layer stratigraphy in the downstream end of kamb ice stream west antarctica satellite images of kamb ice stream formerly ice stream c west antarctica reveal several long curved linear features lineations oriented sub parallel to the ice flow direction we use ground based radar to characterize the internal layer stratigraphy of these lineations and the terrains that they bound some lineations are relict ice stream shear margins identified by hyperbolic diffractors near the surface interpreted to be buried crevasses and highly disturbed internal layers at depth satellite images show another set of lineations outside the relict margins that wrap around the ends of the surrounding inter ice stream ridges internal layers beneath these lineations are downwarped strongly into a syncline shape the internal stratigraphy of the terrain between these lineations and the relict margins is characterized by deep hyperbolic line diffractors our preferred hypothesis for the origin of this terrain is that it was floating sometime in the past the deep hyperbolas are interpreted to be basal crevasses and the strongly downwarped internal layers mark the position of a relict grounding line our study shows that lineations and intervening terrains have different internal layer characteristics implying different origins differentiation between these features is not possible using satellite images alone

low magnitude earthquakes in rome structural interpretation and implications for the local stress field on 1995 june 12 a ml 3 6 earthquake occurred in the cecchignola area of southern rome a detailed structural investigation of this area and an analysis of macroseismic and instrumental data indicate a seismogenic area for the local low magnitude seismicity that affects the city of rome a peripheral volcanic field in cecchignola shows that the local seismicity could be related to the same volcanotectonics that affects the colli albani alban hills region fracture field emission is proposed for the emplacement of about 2 5 km3 of lava which developed a small plateau that was subsequently intruded by the feeder dyke of a large ignimbrite the geometry of this dyke as well as the faults disrupting the lava field indicates ne sw extension younger tectonic features show a nw striking 3 in the studied area suggesting that dextral n s strike slip displacement generated structures that are not compatible with the local present day stress field characterized by a ne striking 3 an analysis of focal solutions and the spatial distribution of the 1995 june 12 microearthquake sequence suggests an e w seismogenic structure whose trend is atypical of the structural setting of the area the present study identifies surface faulting with the same trend as the focal mechanisms in the epicentral area and suggests that these faults represent an inactive surface expression of the deeper structures it is also suggested that these structures originated during a different tectonic regime and are presently reactivated at depth by the ne sw extension the general ne orientation of the t axes from focal mechanisms for the colli albani earthquakes and for the 1995 june 12 cecchignola event strongly supports a regional interpretation for the present day stress field previously observed only in the colli albani area it is likely that a combination of different tectonic styles during the last 600 kyr is necessary to explain the structural features of the cecchignola area and of the central tyrrhenian sea margin of italy in general

marine transgression shoreline emergence evidence in seabed and terrestrial ground temperatures of changing relative sea levels arctic canada precise temperatures to depths of several hundred meters have been measured in abandoned petroleum exploration wells in coastal and offshore areas of the canadian arctic in these regions changes in relative sea level during the quaternary have left a strong thermal signature on deep ground temperatures surface temperature changes of the order of 10 20 k accompanied shoreline emergence due to uplift in some regions and marine transgression due to eustatic changes in sea levels in others classical analytic techniques are used to demonstrate that these anomalous features are a direct consequence of recent changes in sea level in coastal areas of the queen elizabeth islands modelling of the large near surface temperature depth gradients and the distinct curvature in the measured profiles yield emergence times in general agreement with dates taken from emergence curves the analysis suggests that surface temperatures of these coastal areas were 16 19 k higher than at present from the late wisconsinan until emergence in the holocene suggesting either marine conditions for this period or glacial ice cover with basal temperatures near the pressure melting point in contrast at two offshore wells on the beaufort shelf analyses of the negative temperature depth gradients below the seabed and profile curvature yield times of marine transgression generally consistent with the published sea level curve for the area the analyses suggest that surface temperatures of some present offshore areas were 10 16 k lower than today s sea bottom temperatures from the late wisconsinan until marine transgression in the holocene the characteristic ground temperature profiles measured in such arctic areas provide independent evidence for the relative changes in sea level indicated by proxy data it is especially valuable for these areas where there is little historical record and from which datable material such as shells driftwood and pumice fragments may be scarce or ambiguous these effects may not be observable in temperate areas because of the smaller contrast in sea bottom and terrestrial temperatures

changes in the west antarctic ice sheet the portion of the west antarctic ice sheet that flows into the ross sea is thinning in some places and thickening in others these changes are not caused by any current climatic change but by the combination of a delayed response to the end of the last global glacial cycle and an internal instability the near future impact of the ice sheet on global sea level is largely due to processes internal to the movement of the ice sheet and not so much to the threat of a possible greenhouse warming thus the near term future of the ice sheet is already determined however too little of the ice sheet has been surveyed to predict its overall future behavior

stagnation of ice stream c west antarctica by water piracy the dynamic behavior of the west antarctic ice sheet is of interest because of the possibility that it may change and cause rapid sea level rise attention is focused on the fast moving and rapidly responding ice streams that drain the ice sheet one of these ice stream c largely stopped about a century ago and some models for this shutdown postulate negative feedbacks that would tend to stabilize the ice sheet here new data are presented indicating that the slowdown of the ice stream is restricted to its lower part and occurred because of loss of lubrication on localized sticky spots at the bed of the ice stream the increased friction probably arises from a topographic accident of the glacier bed that has directed lubricating water to the neighboring ice stream b together with slow drawdown of the ice sheet rather than from any general stabilizing feedbacks

effects of submarine groundwater discharge on the present day extent of relict submarine permafrost and gas hydrate stability on the beaufort sea continental shelf we investigate the role of submarine groundwater discharge on the offshore temperature and salinity field and its effect on the present day extent of submarine permafrost and gas hydrate stability on the north american beaufort shelf with a two dimensional numerical model based on the finite volume method this study finds that submarine groundwater discharge can play a large role in submarine permafrost evolution and gas hydrate stability suggesting that local hydrology may control the evolution of submarine permafrost as strongly as does sea level or paleoclimatic conditions submarine permafrost evolution shows transient behavior over potentially long time scales e g several glacial cycles before a balance of density and pressure driven flows is established with the permeability variations imposed by the overlying permafrost layer the detectable offshore permafrost extent is related to the quasi stationary location of the saltwater freshwater transition larger values of submarine groundwater discharge allow permafrost to extend farther offshore because fresh pore water preserves relict ice therefore differences in the permafrost extent at locations that share similar paleoclimatic history may be explained in part by differences in the local hydrology gas hydrate stability on the north american beaufort shelf may be more widespread than currently thought because low ice saturation highly degraded submarine permafrost likely exists beyond the boundary detectable by common geophysical methods

normal fault displacement dislocating a roman aqueduct of ephesos western turkey a 38 km long ancient aqueduct channel that served roman ephesos turkey was dislocated vertically over 3 m by a single seismic event on a normal fault a new channel was constructed downstream from the fault in roman times next to and partly on top of the original channel archaeological investigations and study of carbonate deposits suggest a causative seismic event in the second half of the second century ce probably in 178 ce after the original channel had functioned for 35 years the icme tepe fault was identified as responsible for the displacement and may still constitute a seismic and tsunami hazard for the turkish west coast specifically for the city of kusadasi ancient aqueducts of which more than 1400 are presently known are a promising and almost untapped archive for archaeoseismic studies especially in the mediterranean area

permafrost heat flow and the geothermal regime at prudhoe bay alaska temperature measurements through permafrost in the oil field at prudhoe bay alaska combined with laboratory measurements of the thermal conductivity of drill cuttings permit an evaluation of in situ thermal properties and an understanding of the general factors that control the geothermal regime a sharp contrast in temperature gradient at approx 600 m represents a contrast in thermal conductivity caused by the downward change from interstitial ice to interstitial water at the base of permafrost under near steady state conditions interpretation of the gradient contrast in terms of a simple mode for the conductivity of an aggregate yields the mean ice content approx 39 and thermal conductivities for the frozen and thawed section 8 1 and 4 7 mcal cm s sup 0 c respectively these results yield a heat flow of approx 1 3 hfu which is similar to other values on the alaskan arctic coast the anomalously deep permafrost is a result of the anomalously high conductivity of the siliceous ice rich sediments curvature in the upper 160 m of the temperature profiles represents a warming of approx 1 8 sup 0 c of the mean surface temperature and a net accumulation of 5 6 kcal cm sup 2 by the solid earth surface during the last 100 years or so rising sea levelmore and thawing of ice rich sea cliffs probably caused the shoreline to advance tens of kilometers in the last 20 000 years inundating a portion of the continental shelf that is presently the target of intensive oil exploration a simple conduction model suggests that this recently inundated region is underlain by near melting ice rich permafrost to depths of 300 500 m its presence is important to seismic interpretations in oil exploration and to engineering considerations in oil production with confirmation of the permafrost configuration by offshore drilling heat conduction models can yield reliable new information on the chronology of arctic shorelines less

correlation of fluviodeltaic aggradational sections with glacial climate history a revision of the pleistocene stratigraphy of rome volcanic horizons interbedded with fluviodeltaic clastic sediments of the tiber and fosso galeria river valleys near rome provide a unique opportunity to date five middle pleistocene fining upward aggradational sections 40 ar 39 ar ages from the interbedded volcanic beds illustrate that aggradation occurred on an approximate 100 k y cycle and was initiated by sea level rise associated with glacial melting the age constraint additionally shows that aggradation occurs rapidly in response to sea level change and thus ages from volcanic strata within the aggradational sections provide high resolution constraint on the timing of relative sea level rise the established chronology is consistent with other glacial proxies and their radioisotopically or orbitally based time scales for the timing of glacial terminations vi and v but is significantly older than most records for the timing of termination iii ultimately the age of each termination should be determined by radioisotopic means and to that end the work here shows that fluviodeltaic sedimentology provides valuable information for middle pleistocene time scale calibration

genesis evolution and tectonic significance of k rich volcanics from the alban hills roman comagmatic region as inferred from trace element geochemistry trace element data are reported in 21 lava samples from the alban hills one of the most important volcanic complexes of the roman comagmatic region the samples consist mostly of tephritic leucitites with minor phonolitic tephrites and tephritic phonolites emplaced during two distinct phases of activity separated by a caldera collapse

dissolved methane in the beaufort sea and the arctic ocean 1992 2009 sources and atmospheric flux methane concentration and isotopic composition was measured in ice covered and ice free waters of the arctic ocean during 11 surveys spanning the years of 1992 1995 and 2009 during ice free periods methane flux from the beaufort shelf varies from 0 14 mg ch4 m 2 d 1 to 0 43 mg ch4 m 2 d 1 maximum fluxes from localized areas of high methane concentration are up to 1 52 mg ch4 m 2 d 1 seasonal buildup of methane under ice can produce short term fluxes of methane from the beaufort shelf that varies from 0 28 mg ch4 m 2 d 1 to 1 01 mg ch4 m 2 d 1 scaled up estimates of minimum methane flux from the beaufort sea and pan arctic shelf for both ice free and ice covered periods range from 0 02 tg ch4 yr 1 and 0 30 tg ch4 yr 1 respectively to maximum fluxes of 0 18 tg ch4 yr 1 and 2 2 tg ch4 yr 1 respectively a methane flux of 0 36 tg ch4 yr 1 from the deep arctic ocean was estimated using data from 1993 to 1994 the flux can be as much as 2 35 tg ch4 yr 1 estimated from maximum methane concentrations and wind speeds of 12 m s representing only 0 42 of the annual atmospheric methane budget of 560 tg ch4 yr 1 there were no significant changes in methane fluxes during the time period of this study microbial methane sources predominate with minor influxes from thermogenic methane offshore prudhoe bay and the mackenzie river delta and may include methane from gas hydrate methane oxidation is locally important on the shelf and is a methane sink in the deep arctic ocean