the late devensian 22 000 bp irish sea basin the sedimentary record of a collapsed ice sheet margin the late devensian 20 ka bp glacial geology of the irish sea basin 4000 km2 is an event stratigraphy recording the entry of marine waters into a glacio isostatically depressed basin and the rapid retreat of the irish sea glacier as a tidewater ice margin marine limits occur up to 140 m o d across much of the central basin the ice margin was uncoupled from its bed exposing a subglacially scoured topography to glaciomarine processes the irish sea glacier was a major drainage conduit of the last british ice sheet calving of the marine ice margin resulted in fast flow surging of ice streams recorded by drumlin fields around the northern basin margin and tunnel valleys rapid evacuation of the basin may have stranded large areas of dead ice in peripheral zones e g cheshire shropshire lowlands and initiated the collapse of the ice sheet thick wedges of ice contact glaciomarine sediments were deposited during ice retreat as morainal bank complexes by successive tidewater ice margins stabilized at pinning points around the irish sea coast where morainal banks occur on the seaward side of drumlin swarms there is a clear sequential relationship between rapid ice loss from calving ice margins the development of fast flowing ice streams drumlinization and the pumping of subglacial sediment to tidewater raised delta complexes are locally associated with marine limits along the high relief coastal margins of wales east central ireland and the lake district associated valley infill complexes record downslope resedimentation of heterogenous sediments into the marine environment during ice retreat co eval offshore deposits are represented by well stratified glaciomarine complexes that infill a subglacially scoured topography that shows networks of tunnel valleys glaciomarine mud drapes occur well to the south of the maximum limit of grounded ice in the basin e g north devon scilly islands southern ireland the age of these distal sediments previously mapped as pre devensian tills is constrained by amino acid ratios basin rebound following deglaciation was rapid with over 100 m recovery in 3 ka and was followed by a low marine still stand peat accumulating in offshore areas now as much as 55 m below sea level has been drowned by the postglacial eustatic rise in sea level the glacio sedimentary model identified in this paper involving rapid ice retreat and related sedimentation triggered by rising relative sea level suggests that isotatic downwarping is an important mechanism for deglaciating continental shelves

seismic activity accompanying the outbreak of the 1991 1993 eruption of mt etna italy abstract the character and location of seismic activity accompanying the onset of the 1991 1993 eruption at mt etna are compatible with the surface evidence of the volcanic pile rupture both the epicentral distribution and the focal mechanisms of a swarm that occurred on december 14 1991 agree with magma ascent occurring along the main nnw sse trending structure of the volcano and the consequent opening of a system of effusive fissures with the same trend a typical mainshock aftershock sequence recorded the day after and indicating transcurrent displacement occurring along the second principal structure of etna ne sw depicts the tectonic response of the volcanic pile and the underlying basement to major stresses applied by the magma push

documenting surface magmatic activity at mount etna using atsr remote sensing analysis of thermally generated night time volcanic radiances recorded with a 1 km pixel size at 1 6 and 11 m during 1991 1993 and 1996 1999 for mount etna shows that lava flows extending beyond the summit craters can be distinguished from vent activity the two phenomena plot in different regions of feature space when the mean volcanic radiance per anomalous pixel at 11 m is plotted against the mean volcanic radiance at 1 6 m the distinct feature space characteristics of lava flow fields are apparent within 1 2 days of the onset of each effusive event such a plot also enables lava flow fields being fed by open channels to be distinguished from tube fed flow fields rank order analysis of the total 1 6 m volcanic radiance series shows that vent activity and lava flows belong to different populations and offers further scope for remotely identifying changes in eruptive state

recent seismicity and tomographic modeling of the mount etna plumbing system the monitoring of seismic activity in eastern sicily southern italy has been recently improved in the framework of the poseidon project to investigate both tectonics and volcanic processes of mount etna this effort has produced a homogeneous and complete data set which we use to image the deep structure of the volcano and to define the space and time distribution of the recent seismicity encompassing the 1995 eruption diffuse eruptions between 1995 and 1997 a further magma intrusion started in 1997 and an increase of volcanic activity in july 1998 we inverted p wave arrival times from 307 selected local earthquakes to obtain a three dimensional velocity model of the volcano with a simultaneous inversion for hypocenters and velocity parameters the new tomographic images permit us to define the structure beneath the volcano from the surface down to 18 km depth the main structural feature revealed by our inversion is a high velocity body located beneath the central craters whose lateral extent increases from 6 km between 18 and 9 km depth to 12 km between 9 and 3 km depth near the surface the fast anomaly branches in two separate high vp regions which are located below the summit craters and the eastern flank valle del bove respectively the high velocity features are interpreted as high density cumulates of solidified magma that intruded the shallow crust we hypothesize that magma ascends the crust within the relatively small high velocity conduit below 9 km depth and is stored at depth shallower than 9 km within the broad high velocity region as also suggested by petrological data a sharp increase of seismicity in 1997 with earthquakes occurring at the border of the high velocity body suggests that mount etna sustained recent episodes of intrusions which possibly herald future eruptions no large low velocity anomaly interpretable as a melted magma chamber is imaged in the upper 18 km of the crust while a broad low velocity anomaly in the uppermost mantle revealed by regional seismic data possibly indicates the magma source region at depth earthquake occurrence from the deep source to the shallow intrusive area helps to trace the magma migration and the feeding of the volcanic system

dispersion of gaseous volcanogenic fluoride island of hawaii abstract fluoride was measured in samples of lichen collected in 1990 from 68 sites on the island of hawaii in addition fluoride levels were measured in 8 rainfall samples collected at the same time the levels of fluoride in the lichens range from 6 to 332 g g 1 which are similar to the levels measured on etna the highest levels of fluoride were detected close to kilauea and the concentration generally decreases with increasing distance from this volcano this overall pattern of distribution is modified by local variations in wind direction which relate to the topographic features of the island close to kilauea there are more localised controls on the fluoride levels caused by circulating groundwaters and degassing lavas

volcanic activity influenced by tectonic earthquakes static and dynamic stress triggering at mt merapi 1 mt merapi is one of the most dangerous volcanoes in indonesia located within the tectonically active region of south central java this study investigates how mt merapi affected and was affected by nearby tectonic earthquakes in 2001 a mw6 3 earthquake occurred in conjunction with an increase in fumarole temperature at mt merapi in 2006 another mw6 3 earthquake took place concomitant with an increase of magma extrusion and pyroclastic flows here we develop theoretical models to study the amount of stress transfer between the earthquakes and the volcano showing that dynamic rather than static stress changes are likely responsible for the temporal and spatial proximity of these events our examination of the 2001 and 2006 events implies that volcanic activity at mt merapi is influenced by stress changes related to remote tectonic earthquakes a finding that is important for volcano hazard assessment in this densely inhabited area

coupling of eruptions and earthquakes at mt etna sicily italy a case study from the 1981 and 2001 events 1 changes in coulomb failure stress cfs induced by dike propagation during two flank eruptions on mt etna 1981 and 2001 are calculated for the most seismically active faults on the east slope of the volcano the right lateral timpe fault system oriented nnw sse and the left lateral pernicana fault oriented e w calculations performed using coulomb 2 5 software indicate that intrusion of a nnw dike on the nw side of the volcano 1981 eruption rises cfs on both the timpe and pernicana faults in contrast intrusion of a n s dike at high elevation on the south flank 2001 eruption rises cfs only on timpe fault system these results are compatible with the observed pattern of seismicity but emphasize an extremely heterogeneous state of stress on the east flank of the volcano

ground deformation patterns at mt etna from 1993 to 2000 from joint use of insar and gps techniques abstract combined gps measurements and radar interferometry insar have been applied at mt etna to study the ground deformation affecting the volcano both over the long 1993 2000 and short term 1997 1998 and 1998 2000 the aim was to better understand the dynamics of the volcano during the magma recharging phase following the 1991 93 eruption since 1993 insar and gps data indicate that mt etna has undergone an inflation a deep intrusion was detected by insar on the western flank of the volcano between march and may 1997 in the following months this intrusion rose up leading to a seismic swarm occurring in january 1998 in the western sector this now shallow intrusion is confirmed by gps data from 1998 to 2000 a general deflation affecting the upper part of the volcano was detected over the whole study period a continuous eastward to south eastward motion of the eastern sector of the volcano was also evidenced the analytical inversions of gps data inferred a plane dipping about 12 ese located beneath the eastern flank of the volcano at a depth of 1 4 km b s l the movement along this plane is able to reproduce the observed south eastward motion of a sector bounded northward by the pernicana fault westward by the north east rift and the south rift and southward by the mascalucia tremestieri trecastagni fault system insar data have validated this model

faulting on the western flank of mt etna and magma intrusions in the shallow crust surface deformations on the western flank of mt etna volcano spanning 1980 2004 have been analysed as they pertain to stress interactions between magma intrusions within the shallow crust along the s se rift and faulting sensitivity during this period an accurate analysis of strain parameters computed by inversion of sw electro optical distance data suggested that the observed strong displacements on this flank of the edifice can also be related to dextral shear movements along a roughly ne sw buried fault crossing the area covered

magma uprising and flank dynamics on mount etna volcano studied using gps data 1994 1995 1 ground deformation occurring on mount etna from 1994 to 1995 is analyzed in this paper this period was characterized by intense volcanic activity at the four summit craters with frequent strombolian activity fire fountains and emplacement of several new lava flows four gps surveys were carried out during this time two as routinely planned each year and an additional two in 1995 to acquire more data to follow the activity at the ne crater the comparisons between gps surveys are reported in terms of horizontal and vertical displacements of each station and in terms of areal dilatation and principal strain axes during the period considered in this work a trend of increasing areal dilatation of the volcano at a rate of about 5 strain yr was recognized it was briefly interrupted by a small contraction about 2 strain in the autumn of 1995 when volcanic activity at the summit craters began in detail the strain distribution of the network is analyzed it allows the detection of areas showing anomalous behavior such as the summit zone or the pernicana fault inversions of the ground displacement vectors have been performed by appropriately combining numerical and analytical approaches results of the inversions suggest structures defining an eastward and southward sliding of the eastern and southeastern sectors of mount etna

feeding system and magma storage beneath mt etna as revealed by recent inflation deflation cycles 1 ground deformation at mt etna detected by three gps surveys carried out in 2004 2005 and 2006 is analyzed the data set encompasses the 2004 2005 eruptions and foreruns those of 2006 a wide deflation of the entire volcano was detected from 2004 to 2005 accompanying the 2004 2005 eruption conversely an evident inflation phase from 2005 to 2006 followed this eruption and preceded the 2006 one in both cases the deflation inflation cycle was accompanied by a continuous seaward motion of the eastern flank we inverted both data sets 2004 2005 deflation and 2005 2006 inflation using an optimization algorithm based on the genetic algorithm ga in order to detect the ground deformation sources the wide contraction measured during the eruption reveals the drainage of a sill shaped magma reservoir located by data inversions at a depth of about 4 5 km b s l the pressurizing source modeled for the 2005 2006 time interval indicates a refilling of the shallower near vertical plumbing system of the volcano this could indicate a change in the geometry of the feeding system active after the 2004 2005 eruption with a new and shallower magma storage that could have enabled the resumption of volcanic activity that was observed at summit craters in 2006 these results improve the imaging of the plumbing system of mt etna volcano

the subsidence history of the northern hyblean plateau margin southeastern sicily abstract the southeastern corner of sicily is dominated by the hyblean plateau which is composed of carbonate rocks of triassic to miocene age the plateau forms part of the african foreland which collided during tertiary times with the calabrian arc giving rise to the maghrebian thrust belt the present study attempts to reconstruct the subsidence history of the northern hyblean plateau during the neogene climax of the plate collision this area has been a centre for widespread basaltic volcanic activity 8 1 ma and uplift at the close of the collisional events pliocene early pleistocene the area under consideration has been affected by subsidence and the progressive consumption of the northern margin of the hyblean plateau led to the development of the modern foredeep a quantitative analysis was done by one dimensional airy backstripping of seven deep wells located on this crucial part of the hyblean plateau the results of the analysis show that the subsidence history of the northern hyblean plateau area is characterized by four main phases similar to other domains in the central and eastern mediterranean basins these phases are a neotethyan rifting during late triassic early jurassic time b a slow thermal subsidence from early jurassic until late cretaceous time leading to the formation of a widespread mesozoic carbonate platform c compressional phase during late cretaceous palaeogene time which resulted in the formation of fold systems and d uplift and subsidence events during the middle tertiary which are probably the result of the continued collision of the european african plates after the early pleistocene unlike other terranes within the mediterranean an uplift occurred in the northern hyblean plateau following the upper miocene lower pleistocene massive volcanic activity this uplift is probably associated with the latest stages of thrusting along the frontal part of the maghrebian thrust belt

evidence from the ad 2000 izu islands earthquake swarm that stressing rate governs seismicity magma intrusions and eruptions commonly produce abrupt changes in seismicity far from magma conduits that cannot be associated with the diffusion of pore fluids or heat such swarm seismicity also migrates with time and often exhibits a dog bone shaped distribution the largest earthquakes in swarms produce aftershocks that obey an omori type exponential temporal decay but the duration of the aftershock sequences is drastically reduced relative to normal earthquake activity here we use one of the most energetic swarms ever recorded to study the dependence of these properties on the stress imparted by a magma intrusion a 1 000 fold increase in seismicity rate and a 1 000 fold decrease in aftershock duration occurred during the two month long dyke intrusion we find that the seismicity rate is proportional to the calculated stressing rate and that the duration of aftershock sequences is inversely proportional to the stressing rate this behaviour is in accord with a laboratory based rate state constitutive law suggesting an explanation for the occurrence of earthquake swarms any sustained increase in stressing rate whether due to an intrusion extrusion or creep event should produce such seismological behaviour

dynamic deformation of etna volcano observed by satellite radar interferometry satellite radar interferometry of mt etna volcano sicily italy reveals a sequence of deformation characterized by deflation during the end of the 1993 eruption inflation from 1993 1995 with an increase in the inflation rate immediately before its resumed eruptive activity in late 1995 this was followed by very low deformation levels during the following year the source of the deformation changed from a depth of 9 km during deflation to more than 11 14 km during the subsequent inflation consistent with a model in which deflation at shallower levels is followed by inflation at greater depth as the volcano system recharges from below before its next eruption this study demonstrates that radar interferometry provides an important contribution towards understanding the dynamic deformation of volcanoes by revealing large scale changes in their pre eruption deformation rates radar interferometry could play an important role in volcano eruption monitoring

island terminus evolution related to changing ebb tidal delta configuration texel the netherlands historical maps of southwest texel and the adjacent ebb tidal delta supplemented with quartz osl optically stimulated luminescence ages of dune sand span four centuries and show several links between coastal development and ebb tidal delta behavior updrift inlet migration governed recurved spit formation and changes in ebb tidal delta size and shape resulted in the formation of a bulge at the island terminus sustained updrift migration of the ebb tidal delta resulted in a commensurate position shift of the bulge and eventually in flattening of the coastline regional coastal management measures have had a strong influence on tidal inlet and ebb tidal delta behavior and therefore also on the changing shape of southwest texel identification of relationships between ebb tidal delta behavior and changing barrier terminus erosion and accretion patterns on a decadal to century time scale contributes to our understanding of coastal system dynamics any barrier terminus with preserved sets of dune ridges holds a potential record on past ebb tidal delta orientations which provide clues on past changes in tidal prisms and wave versus tide dominance under the current ebb tidal delta configuration the entire westward oriented coast of southwest texel is too exposed for lasting accretion bulges resulting from future merger of shoals with the coast in this area will be eroded rapidly 2006

dike induced reverse faulting in a graben normal fault slip of the boundary faults of a graben is commonly attributed to dike induced stresses here however we report for the first time clear field evidence of a large dike induced reverse fault slip on a fault associated with a volcano tectonic graben the measured reverse faulting of at least 5 m occurs in the holocene rift zone of northern iceland the reverse slip has apparently occurred on an existing normal fault as a result of over pressure of a nearby 6 13 m thick 8 ka feeder dike a numerical model of the dike fault interaction supports our interpretation the results indicate that dikes particularly potential feeder dikes may cause large reverse slips on nearby normal faults this conclusion should improve the general understanding of geodetic deformation during volcanic unrest periods and may help forecast dike fed eruptions

the svalbard barents sea ice sheet historical current and future perspectives abstract the history of research on the late quaternary svalbard barents sea ice sheet mirrors the developments of ideas and the shifts of paradigms in glacial theory over the past 150 years since the onset of scientific research there in the early 19th century svalbard has been a natural laboratory where ideas and concepts have been tested and played an important but rarely acknowledged role in the break through of the ice age theory in the 1870 s the history of how the scientific perception of the svalbard barents sea ice sheet developed in the mid 20th century also tells a story of how a combination of fairly scattered and often contradictory observational data and through both deductive and inductive reasoning could outline a major ice sheet that had left but few tangible fingerprints since the 1980 s with increased terrestrial stratigraphical data ever more marine geological evidence and better chronological control of glacial events our perception of the svalbard barents sea ice sheet has changed the first reconstructions depicted it as a static concentric single domed ice sheet with ice flowing from an ice divide over the central northern barents sea that expanded and declined in response to large scale late quaternary climate fluctuations and which was more or less in tune with other major northern hemisphere ice sheets we now increasingly perceive it as a very dynamic multidomed ice sheet controlled by climate fluctuations relative sea level change as well as subglacial topography substrate properties and basal temperature in this respect the svalbard barents sea ice sheet will increasingly hold the key for understanding the dynamics and processes of how marine based ice sheets build up and decay

the 1994 1995 seismicity and deformation at the hengill triple junction iceland triggering of earthquakes by minor magma injection in a zone of horizontal shear stress since july 1994 an unusually persistent swarm of earthquakes m 4 0 has been in progress at the hengill triple junction sw iceland activity is clustered around the center of the hromundartindur volcanic system geodetic measurements indicate a few centimeters uplift and expansion of the area consistent with a pressure source at 6 5 3 km depth beneath the center of the volcanic system the system is within the stress field of the south iceland transform zone and the majority of the recorded earthquakes represent strike slip faulting on subvertical planes we show that the secondary effects of a pressure source modeled as a point source in an elastic half space include horizontal shear that perturbs the regional stress near the surface shear stress is enhanced in quadrants around the direction of maximum regional horizontal stress and diminished in quadrants around the direction of minimum regional stress the recorded earthquakes show spatial correlation with areas of enhanced shear the maximum amount of shear near the surface caused by the expanding pressure source exceeds 1 strain sufficient to trigger earthquakes if the crust in the area was previously close to failure

seismogenic stress field beneath mt etna south italy and possible relationships with volcano tectonic features abstract shallow shear type seismic activity occurring beneath the etna volcano during 1990 1995 has been analysed for hypocenter locations focal mechanisms and stress tensor inversion the results have been examined jointly with electronic distance measurements and tiltmeter data collected in the same period and reported in the literature significant seismicity located in the upper 10 km was found to be confined to the time intervals in which ground deformation data indicated inflation of the volcano edifice e g the periods preceding the december 1991 march 1993 and august 1995 march 1996 eruptive phases the shocks mostly occurred in a sector approximately centered on the crater area and elongated in the east west direction the causative seismogenic stress shows a low dip east west orientation of 1 in agreement with existing knowledge on relationships between local fault systems and magma uprise processes the shallow seismicity in question is tentatively explained as being due to lateral compression by magma inside a nearly north south system the volcano deflation phase revealed by electronic distance measurements and tilt data during the 1991 1993 major eruption was not accompanied by any significant shear type shallow event below the depth of 10 km the north south prevailing orientation of 1 reflects the dominant role of the regional stress

volcanological inferences from seismic strain tensor computations at mt etna volcano sicily kostrov s 1974 algorithm for seismic strain tensor computations in the version implemented by wyss et al 1992a for error estimates has been applied to shear type earthquakes occurring beneath the etna volcano during 1990 1996 space time variations of strain orientations and amplitudes have been examined jointly with ground deformation and gravimetric data collected in the same period and reported in the literature taking also into account the information available from volcanological observations and structural geology we propose a model assuming that hydraulic pressure by magma emplaced in nearly north south vertical structures produces the e w orientation of the maximum compressive strain found in the upper 10 km beneath the crater area in contrast regional tectonics deriving from the slow north south convergence between the african and european plates appear to play a dominant role in the generation of stress and strain fields at crustal depths deeper than 10 km below the volcano according to our interpretation the progressive ascent of magma through the upper crust prior to eruption produces the observed gravity changes cone inflation and unusual seismic strain rate in the upper 10 km associated with a more sharply defined seismic deformation regime i e very small confidence limits of the e1 orientation in agreement with this model deflation revealed by ground deformation data during the course of the major 1991 1993 eruption was accompanied by a practically nil level of shallow seismicity

magma intrusion mechanisms and redistribution of seismogenic stress at mt etna volcano 1997 1998 terra nova 23 339 348 2011 abstract several volcanoes worldwide have shown changes in their stress state as a consequence of the deformation produced by the pressurization of a magmatic body this study investigated seismic swarms occurring on the western flank of mt etna in january 1997 january 1998 integrating seismic observations and geodetic data we constrained the seismogenic fault system and on the basis of stress tensor inversion and shmax analyses we inferred an inflating pressure source located at 5 5 km b s l beneath the west portion of summit area evaluation of coulomb failure stress related to the proposed model showed how a large part of the seismogenic fault underwent a significant coulomb failure stress increase 500 kpa we inferred the presence of a sub vertical faulted region potentially weak n50 e oriented beneath the western sector of mt etna this structure could be brought closer to failure thereby generating seismic swarms as the effect of elastic stress transfer induced by movement and or overpressure of magmatic masses within the upper crust under the volcano

the neogene origin adoption evolution and controversy abstract some stratigraphers have recently insisted that for historical reasons the neogene miocene pliocene should be extended to the present however despite some ambiguity in its application by moriz hornes in the 1850s the neogene was widely adopted by european geologists to refer to the miocene and pliocene of lyell but excluding the diluvium later to become the pleistocene and alluvium later to become the holocene during the late 19th and early 20th centuries the ends of the neogene tertiary and pliocene evolved in response to the progressive lowering of the beginnings of the quaternary and pleistocene this evolution was a logical result of the widespread views that the most recent ice ages were worthy of recognition as a formal unit of the standard geologic time scale and that the structure of this time scale must be strictly hierarchical motivations for the extension of the neogene to the present include the desire to establish a monopoly for marine biochronology in the definition of standard global chronostratigraphic boundaries this agenda would also eliminate the tertiary quaternary and holocene these changes are unnecessary there is every reason to retain the traditional hierarchical structure of the cenozoic time scale

magma dynamics in the shallow plumbing system of mt etna as recorded by compositional variations in volcanics of recent summit activity 1995 1999 describe the reactivation and the successive evolution of the shallow plumbing system of mt etna between the end of the largest flank eruption of the last three centuries 1991 1993 and the subterminal eruption from south east crater sec which occurred between february and mid november 1999 our analysis is based on observations of the volcanic activity and petrological studies of the erupted volcanics bulk rock mineral and glass compositions have been determined for more than 80 samples erupted from the four summit craters between october 1995 and february 1999 these data allow us to recognise significant compositional variations among the products of different craters in particular volcanics produced between 1995 and 1999 by bocca nuova bn voragine vor and north east crater nec show limited compositional variations and are similar to those observed during recent eruptions e g 1991 93 more primitive magmas have been produced during the more vigorous fire fountains episodes on the contrary the south east crater produced slightly more differentiated volcanics than those of the other summit craters following its reactivation november 1996 until the end of 1998 whole rock compositions of products from this crater show low cao al 2 o 3 whereas interstitial glasses have lower mgo and higher alkali contents than those from the other craters however since the beginning of 1999 and just before the start of the subterminal eruption from sec the volcanics erupted from this crater progressively changed in composition becoming similar to those of the other craters this trend indicates that within the conduits of the summit craters distinct thermal and fluid dynamical regimes can evolve controlling the cooling and crystallisation of etna magmas

seismic tomography of the crust underneath the etna volcano sicily abstract a new tomographic inversion of the velocity structure and hypocenter parameters has been carried out in the etna area using a remarkably larger seismic dataset than used in the previous investigations the obtained v p and v p v s space distributions allow us to detail the already known structural features and to find new velocity anomalies a major aseismic high velocity body is recognized in the upper 10 km beneath the central crater area and the southeastern flank of the volcano interpreted as high strength magmatic rocks such as cumulites dike structures etc a high level of seismic activity and low v p values are found immediately to the west and the east of the high velocity body suggesting the presence of highly fractured weakness zones which also taking into account the local distribution of seismogenic stress can be supposed to include paths for magma rising and stationing clear evidence is also found of a shallow aseismic low velocity zone beneath the volcano s southwestern flank corresponding to the volume where previous investigators hypothesized the presence of a magma chamber on the grounds of geodetic data and seismic b value mapping

dynamics of mount etna volcano inferred from static and kinematic gps measurements 1 ground deformations measured on mount etna from late 1995 to mid 1998 using gps observations are analyzed four gps surveys were carried out during the considered period in 1995 the gps network consisted of 18 stations on the volcanic edifice and 6 stations around it during the 1996 survey 22 new monuments were added along a n s profile crossing the summit craters area this profile was surveyed by a semikinematic method allowing greater spatial detail to be achieved on the uppermost part of the volcano the comparisons between the gps surveys are reported here in terms of horizontal and vertical displacements for each station and also in terms of areal dilatation and strain distribution this last parameter continues its ascending trend at a rate of 5 strain yr 1 already shown in the previous period after the end of the 1991 1993 flank eruption inversion of the ground deformation patterns permits investigation of the evolution of both the position and dynamics of magma reservoirs beneath the volcano consistently associated with a general eastward sliding of its eastern sector this study allows us to define the nonuniqueness of ground deformation sources through the investigated period suggesting that the plumbing system of the volcano is made up of a complex system of single intrusions occurring at different times

genesis of hummocky moraines by thrusting in glacier ice evidence from svalbard and britain irregular mounds of glacial debris commonly referred to as 9hummocky moraine9 until recently were linked to ice stagnation during rapid climatic amelioration however recent work in scotland has demonstrated that some hummocky moraine dating from the younger dryas event c 10 000 years bp was the product of deposition at active ice margins observations at modern high arctic glacier margins in svalbard 76 80 n indicate that some moraines of this type form under a dynamic glaciological regime mainly by thrusting in active polythermal ice undergoing strong longitudinal compression this situation is particularly common where there is a transition from warm based ice in the interior of a glacier to cold based ice at the margins or snout from their morphological similarity rectilinear slopes facing up glacier and irregular downglacier faces and apparent stacking of slabs of sediment of subglacial derivation it is concluded that some assemblages of british moraines are also the product of thrusting this process appears to be most dominant in polythermal glaciers rather than in temperate glaciers on this basis it is tentatively suggested that the younger dryas in britain was characterized by a climatic regime similar to that in svalbard today mean annual temperature 5 c 400 1000 mm precipitation and that the associated glaciers may have been of polythermal character

magma ascent and the pressurization of mount etna s volcanic system after a period of deflation during the 1991 1993 flank eruption mount etna underwent a rapid inflation seismicity and ground deformation show that since 1994 a huge volume of magma intruded beneath the volcano producing from 1998 onward a series of eruptions at the summit and on the flank of the volcano the last of these started on 27 october 2002 is still in progress and can be considered one of the most explosive eruptions of the volcano in recent times here we show how geodetic data and seismic deformation between 1994 and 2001 indicate a radial compression around an axial intrusion consistent with a repressurization of mount etna s plumbing system at a depth of 6 to 15 kilometers which triggered most of the seismicity and provoked the dilatation of the volcano and the recent explosive eruptive activity

charles lyell and the evidences of the antiquity of man abstract this paper examines the importance of lyell s book the geological evidences of the antiquity of man 1863 in lyell s work and career as well as its contribution to the founding of two scientific disciplines prehistoric archaeology and palaeoanthropology it first focuses on lyell s two conversions to the idea of the antiquity of man and to darwin s theory of transmutation of species both of which he acknowledged in his book it turns then to a study of the nature of the evidences that lyell advances these evidences were of several kinds archaeological palaeontological anthropological and most importantly geological at the time the best way to prove the existence of fossil man was to demonstrate geologically the contemporaneity of man made objects and extinct animals this paper insists in particular on lyell s relationship to french science of the time and examines the circumstances and modalities of a collaboration which was essential to the international acceptance of the antiquity of man the fact that lyell was a major scientific authority whose expertise could validate the authenticity of evidence allowed him to play a central role in the founding of a new field of knowledge

fast deformation processes and eruptive activity at mount etna italy the seismic and deformation patterns observed on mount etna before and during the 1991 1993 eruption the third largest since the seventeenth century in terms of lava volume are consistent with the regional tectonic framework of eastern sicily the pattern of the stress field acting on the intermediate and lower crust was defined at the local scale by focal mechanisms of microearthquakes occurring at depths between 10 and 25 km beneath the volcano they provide evidence for a strike slip compressional stress regime with the maximum compressive component acting approximately n s the fault plane solutions and the spatial and temporal distribution of seismicity indicate that usually sinistral shear ruptures occur along approximately ne sw trending fault zones while dip slip ruptures affect approximately nnw sse trending fault zones the latter include the avenues along which magma ascended during the 1991 1993 eruption seismic observations indicate a local inversion of the stress field acting on the upper crust depth 10 km underlying mount etna which was initiated less than 2 months before the eruptive event and disappeared with its end this is consistent with a local tensile regime that favored the magma ascent through the shallow crust the events preceding the eruption and accompanying its onset tilt anomalies and seismic swarms and those occurring shortly after its beginning a mainshock aftershock seismic sequence and associated coseismic tilts provide important evidence for understanding the dynamics of the two main volcano tectonic structures ne sw and nnw sse trending fault zones and associated intrusive mechanisms on etna the shape and location of the eruption feeding dike have been modeled from ground deformation data this approximately nnw sse modeled dike the seismicity and the position of the fractures are consistent with the regional stress field characterized by 1 oriented approximately n s the geophysical data presented and analyzed in the present paper strongly suggest an overall regional tectonic control as well as an active role for the intruding magma in the dynamics of the volcano

shear response to an intrusive episode at mt etna volcano january 1998 inferred through seismic and tilt data abstract the space time evolution of a seismic swarm m d max 3 7 occurring on 9 14 january 1998 at mt etna volcano is analysed the hypocentral pattern and most reliable focal mechanisms indicate that seismic activity during 10 14 january mainly occurred within a fault zone located in the volcano s western flank the fault showed an approximately ne sw overall trend and shallow rupture mode of right lateral strike slip type it is noteworthy that earthquakes occurring during the initial phase 9 january of the swarm showed prevalent dip slip rupture mechanisms which are consistent with tensile opening of an approximately nnw sse trending fault zone this nnw sse structural lineament belongs to a regional lithospheric structure which has also been identified as a main volcano genic structural trend of mt etna the observed continuous tilt data are not explainable by the seismic slip associated with strain released along the ne sw structure however an intrusive source would be compatible with the rupture mechanisms observed during the initial phase of the swarm and could explain the observed tilt therefore we evidence that an intrusive episode occurred along the nnw sse structure starting 9 january and during the following days it forced the ne sw fault system to work in a right lateral mode these mechanisms leading to the february november 1999 summit eruption are analogous to the ones observed before the 1991 93 eruption

stress transferred by the 1995 mw 6 9 kobe japan shock effect on aftershocks and future earthquake probabilities the kobe earthquake struck at the edge of the densely populated osaka kyoto corridor in southwest japan we investigate how the earthquake transferred stress to nearby faults altering their proximity to failure and thus changing earthquake probabilities we find that relative to the pre kobe seismicity kobe aftershocks were concentrated in regions of calculated coulomb stress increase and less common in regions of stress decrease we quantify this relationship by forming the spatial correlation between the seismicity rate change and the coulomb stress change the correlation is significant for stress changes greater than 0 2 1 0 bars 0 02 0 1 mpa and the nonlinear dependence of seismicity rate change on stress change is compatible with a state and rate dependent formulation for earthquake occurrence we extend this analysis to future mainshocks by resolving the stress changes on major faults within 100 km of kobe and calculating the change in probability caused by these stress changes transient effects of the stress changes are incorporated by the state dependent constitutive relation which amplifies the permanent stress changes during the aftershock period earthquake probability framed in this manner is highly time dependent much more so than is assumed in current practice because the probabilities depend on several poorly known parameters of the major faults we estimate uncertainties of the probabilities by monte carlo simulation this enables us to include uncertainties on the elapsed time since the last earthquake the repeat time and its variability and the period of aftershock decay we estimate that a calculated 3 bar 0 3 mpa stress increase on the eastern section of the arima takatsuki tectonic line attl near kyoto causes fivefold increase in the 30 year probability of a subsequent large earthquake near kyoto a 2 bar 0 2 mpa stress decrease on the western section of the attl results in a reduction in probability by a factor of 140 to 2000 the probability of a mw 6 9 earthquake within 50 km of osaka during 1997 2007 is estimated to have risen from 5 6 before the kobe earthquake to 7 11 afterward during 1997 2027 it is estimated to have risen from 14 16 before kobe to 16 22

impulsive tilt variations on mount etna volcano 1990 1993 abstract this study was focussed on the analysis of the fast ground deformations impulsive anomalies recorded at the mt etna tilt array from 1990 to 1993 a period that preceded accompanied and followed the 1991 1993 eruption these fast deformations were recorded as transient anomalies ranging from a few hours to days 1 2 observed contemporaneously at several tilt stations and characterized by variations ranging from one to tens of microradians the signals evidenced volcanic dynamics characterized by tilt anomalies during the non eruptive periods 1990 1993 the pre eruptive period november december 1991 the beginning of the eruption 14 15 december 1991 and the eruption course 1992 in particular pre seismic co eruptive and co seismic anomalies were recorded during the pre eruptive period and the eruption onset in these cases interpretations of the phenomena and comparison to modelling studies are provided furthermore tilt variations affecting the global volcanic edifice were also observed one year before the eruption when they were followed by seismicity and during the eruption course without seismicity we interpreted this last class of tilt variations as due to the push of the magma uprising along the main nnw sse structure crossing mt etna