persistent scatterer interferometric synthetic aperture radar for crustal deformation analysis with application to volcan alcedo galapagos 1 while conventional interferometric synthetic aperture radar insar is a very effective technique for measuring crustal deformation almost any interferogram includes large areas where the signals decorrelate and no measurement is possible persistent scatterer ps insar overcomes the decorrelation problem by identifying resolution elements whose echo is dominated by a single scatterer in a series of interferograms existing ps methods have been very successful in analysis of urban areas where stable angular structures produce efficient reflectors that dominate background scattering however man made structures are absent from most of the earth s surface furthermore existing methods identify ps pixels based on the similarity of their phase history to an assumed model for how deformation varies with time whereas characterizing the temporal pattern of deformation is commonly one of the aims of any deformation study we describe here a method for ps analysis stamps that uses spatial correlation of interferogram phase to find pixels with low phase variance in all terrains with or without buildings prior knowledge of temporal variations in the deformation rate is not required for their identification we apply stamps to volcan alcedo where conventional insar fails because of dense vegetation on the upper volcano flanks that causes most pixels to decorrelate with time we detect two sources of deformation the first we model as a contracting pipe like body which we interpret to be a crystallizing magma chamber the second is downward and lateral motion on the inner slopes of the caldera which we interpret as landsliding

on the hellenic subduction zone and the geodynamic evolution of crete since the late middle miocene abstract in recent syntheses of the geodynamic evolution of the aegean area the hellenic subduction zone and in particular its initiation plays a central role two basic aspects of the recent comprehensive model put forward by le pichon angelier and co workers are a initiation of subduction along the hellenic arc is inferred to have taken place approximately 13 ma ago whereas several others have suggested approximately 5 ma and b migration of the trench system to the south southwest giving rise to an extensional regime in the back arc region which led to general subsidence and formation of the present day aegean sea new data on the structure of the upper mantle underneath the aegean area indicate that the former aspect requires modification the seismic velocity structure indicating a northward dipping slab down to a depth of at least 600 km and the depth distribution of earthquake hypocenters can not be reconciled with straightforward initiation of subduction approximately 13 ma ago estimates of about 5 ma for the time of initiation of the present subduction zone are even more difficult to reconcile assuming 400 km as an upper bound for the effect of stretching of the aegean sea and of other processes contributing to the separation of crete from the eurasian mainland we arrive at an age for the hellenic subduction zone of at least 26 ma as to aspect b geological data of crete lend strong support to the idea that on crete compressional tectonics is of much greater importance than current models imply combining geophysical and geological data we propose a modification of the tectonic evolution for the cretan segment of the hellenic arc whereas the basic process of extension caused by a migrating trench system roll back in a land locked basin remains a very useful and sound concept the tectonics of the margins of a region subject to stretching in this case crete may be more complicated than hitherto thought in our model the documented fragmentation of crete into several basins which started about 12 ma ago is not attributed to initiation of subduction but to inception of the roll back process compressional tectonics on crete is taken to be associated with deformation of the crust resulting from the overall tensional stress regime

ground deformation in askja iceland its source and possible relation to flow of the mantle plume abstract the volcano askja in east central iceland erupted several times between 1920 and 1930 following a very large caldera forming eruption in 1875 the last eruption occurred in 1961 measurements of the vertical component of ground deformation in askja were commenced in 1966 and made once each year 1966 to 1972 and 1983 to 1987 distance measurements with a geodimeter were first made in 1982 the measurements have shown alternating uplift and subsidence of the central part of the askja caldera two periods of uplift and three periods of subsidence have been identified during the 21 years of observations observed vertical displacements agree fairly well with a single point source model at a depth of 1 5 3 5 km below the surface near the center of the askja caldera deviation from a single point source model can be explained by a secondary source of subsidence beneath the site of the 1961 eruption this secondary source has been diminishing in intensity and appears to have been exhausted by 1983 1987 askja has been subsiding at a rate of 6 10 cm per year during the period 1983 1987 but in 1970 1972 rapid inflation was observed possibly as much as 20 cm per year the period of no levelings 1972 to 1983 is characterized by deflation but at a slower average rate than observed in 1983 1987 this suggests continuation of the 1970 1972 inflation into 1973 or 1974

the miocene pakhna formation southern cyprus and its relationship to the neogene tectonic evolution of the eastern mediterranean abstract the miocene pakhna formation is interpreted as relating to onset of the present northward subduction of the african plate beneath cyprus and is thus critical to understanding of the neogene evolution of the eastern mediterranean basin following a perios of deep water pelagic chalk deposition in the late eocene and oligocene upper lefkara fm the pakhna formation records heterogeneous mainly carbonate sedimentation the pakhna formation is bounded by the limassol forest block an uplifted ophiolitic terrain to the north and by the akrotiri high a ridge of exotic mesozoic lithologies to the south two sub basins maroni in the e and khalassa in the w within the pakhna formation were separated by the wnw ese trending yerasa lineament located near the s margin of the ophiolite in most areas the pakhna formation overlies the lefkara formation disconformably the succession begins with deep water pelagic carbonates and shows increased input of shallow water bioclastic and terrigenous sediment upward during the early to mid miocene the ophiolitic terrain to the n was uplifted deformed and eroded followed by marine transgression and patch reef development in the tortonian late miocene ophiolite derived clastics were mixed with shallow water bioclastic sediment reworked in a high energy coastal setting and transported downslope within channels into the basin accumulating as massive sands debris flows and calciturbidites in the maroni sub basin localised debris aprons prograded into a pelagic carbonate environment to the se further west in the khalassa sub basin little uplift occurred along the basin margins and redeposited sediment was mainly bioclastic contrasting sediment including chert was derived from the allochthonous mamonia complex exposed on the akrotiri high to the s and its possible offshore extension bioclastic sediment including reef talus was also derived from an intrabasinal high in the khalassa sub basin eventually normal marine deposition was ended by the messinian salinity crisis

the magmatic plumbing system of the askja central volcano iceland as imaged by seismic tomography the magmatic plumbing system beneath askja a volcano in the central icelandic highlands is imaged using local earthquake tomography we use a catalog of more than 1300 earthquakes widely distributed in location and depth to invert for the p wave velocity vp and the vp vs ratio extensive synthetic tests show that the minimum size of any velocity anomaly recovered by the model is 4 km in the upper crust depth 8 km below sea level bsl increasing to 10 km in the lower crust at a depth of 20 km bsl the plumbing system of askja is revealed as a series of high vp vs ratio bodies situated at discrete depths throughout the crust to depths of over 20 km we interpret these to be regions of the crust which currently store melt with melt fractions of 10 the lower crustal bodies are all seismically active suggesting that melt is being actively transported in these regions the main melt storage regions lie beneath askja volcano concentrated at depths of 5 km bsl with a smaller region at 9 km bsl their total volume is 100 km3 using the recorded waveforms we show that there is also likely to be a small highly attenuating magmatic body at a shallower depth of about 2 km bsl

plate boundary deformation in north iceland during 1992 2009 revealed by insar time series analysis and gps abstract in north iceland extensional plate motion is accommodated by the northern volcanic zone a set of en echelon volcanic systems and the tjornes fracture zone a transform offset in the mid atlantic ridge consisting of two parallel transform lineaments the southern lineament the husavik flatey fault is a 100 km long right lateral strike slip fault that has not ruptured for more than 140 years and poses a significant seismic hazard to husavik a fishing town located by the fault and to other coastal communities we present results of insar time series analysis data spanning almost two decades 1992 2009 that show extensional and interseismic deformation within the northern volcanic zone and the on shore part of the tjornes fracture zone the results also exhibit transient inflation at theistareykir volcano deflation at krafla central volcano and a broad uplift north of krafla the current plate extension is not uniform across the northern volcanic zone but concentrated at the western fissures of the theistareykir volcanic system and the outermost fissures of the krafla fissure swarm we combine a back slip plate boundary model with a set of point pressure sources representing volcanic changes to describe the current extensional plate boundary deformation and update the previous estimations of the locking depth and slip rate of the husavik flatey fault that were based on gps data alone using different combinations of input data we find that the husavik flatey fault has a locking depth of 6 10 km and with a slip rate of 6 9 mm yr is accommodating about a third of the full transform motion we furthermore show that while the insar data provide important constraints on the volcanic deformation within the nvz they do not significantly improve the model parameter estimation for the hff as the dense gps network appears to better capture the deformation across the fault

sedimentology of a marine intermontane pleistocene gilbert type fan delta complex in the crati basin calabria southern italy the crati basin is a pliocene holocene extensional basin filled by the progradation of different types of marine fan delta systems coarse grained gilbert type fan deltas developed during the pleistocene they represent the sedimentary response to a strong differential uplift involving the basin margins and the basin itself the differential uplift was responsible for the fragmentation of the basin into several sub basins into which these fan deltas prograded the protection and lateral confinement by structural highs steep coastlines and the absence of strong tidal action in the adjacent ionian sea allowed the regular progradation of these fan deltas in the restricted gulfs and narrow embayments of the crati basin for the classical gilbert type fan deltas in lacustrine settings homopycnal inflow favours a rapid mixing of water masses and deposition of sediment close to the river mouth in the case of the example described here the density contrast between the sea water and the inflowing river water caused the separation of the muddy fraction from the coarse sandy and conglomeratic part of the sediment this allowed the development of steep mud poor coarse grained delta foresets slope instability features slump scars conglomeratic flow slides are fairly scarce in the proximal parts of the san lorenzo del vallo system towards the north where protection from the ionian sea was less they increase in importance

deformation of grimsvotn volcano iceland 1998 eruption and subsequent inflation 1 grimsvotn is a subglacial volcano under the vatnajokull ice cap at the center of the icelandic hotspot this highly active volcano erupted in december 1998 gps measurements at a single station on a nunatak at the caldera rim were made 7 times during 1992 2001 the measurements prior to the 1998 eruption reveal pre eruption inflation but subsidence of more than 15 cm was measured during the eruption following the eruption re inflation occurred initially at a rate of 20 mm month then declined to 5 mm month measurements were fitted to a mogi model assuming that the source was located under the center of the grimsvotn caldera complex results indicate a source depth of at least 1 6 km the calculated amount of magma outflow during the eruption is comparable to field estimates of the erupted volume grimsvotn continues to inflate but has not reached its 1998 pre eruption level

satellite radar interferometry 1993 1999 suggests deep accumulation of magma near the crust mantle boundary at the krafla volcanic system iceland 1 deep magma accumulation near the crust mantle boundary 21 km depth at the krafla volcanic system is suggested from insar observations a best fit model derived from four interferograms covering 1993 1999 comprises an opening dike representing plate spreading and post rifting deformation and two mogi sources a mogi source deflating at a rate of 0 3 106 m3 yr coincides with the shallow krafla magma chamber while a deeper inflating mogi source further north at 21 km depth inflates at a rate of 26 106 m3 yr the inflating source is at or near the crust mantle boundary as identified by seismic studies and is interpreted as accumulating magma

lower crustal earthquakes caused by magma movement beneath askja volcano on the north iceland rift the lower crust of magmatically active rifts is usually too hot and ductile to allow seismicity the icelandic mid atlantic rift is characterized by high heat flow abundant magmatism generating up to 25 30 km thick crust and seismicity within the upper 8 km of the crust in a 20 seismometer survey in july august 2006 within the northern rift zone around the askja volcano we recorded 1700 upper crustal earthquakes cutting off at 7 8 km depth marking the brittle ductile boundary unexpectedly we discovered 100 small magnitude ml 1 5 earthquakes occurring in swarms mostly at 14 26 km depth within the otherwise aseismic lower crust and beneath the completely aseismic middle crust a repeat survey during july august 2007 yielded more than twice as many lower crustal events geodetic and gravimetric data indicate melt drainage from crustal magma chambers beneath askja we interpret the microearthquakes to be caused by melt moving through the crust from the magma source feeding askja they represent bursts of magma motion opening dykes over distances of a few meters facilitated by the extensional setting of the active rift zone

fault slip distribution of two june 2000 m w 6 5 earthquakes in south iceland estimated from joint inversion of insar and gps measurements abstract we present the first detailed estimates of co seismic slip distribution on faults in the south iceland seismic zone sisz an area of bookshelf tectonics we have estimated source parameters for two m w 6 5 earthquakes in the sisz on june 17 and 21 2000 through a joint inversion of insar and gps measurements our preferred model indicates two simple 15 km long near vertical faults extending from the surface to approximately 10 km depth the geometry is in good agreement with the aftershock distribution the dislocations experienced pure right lateral strike slip reaching maxima of 2 6 m and 2 9 m for the june 17 and 21 events respectively we find that the distribution of slip with depth may be correlated to crustal layering with more than 80 of the total geometric moment release occurring in the uppermost 6 km according to the distributed slip model the middle and upper crust appears to be more apt to generate large displacements than the lower crust the geodetic estimates of seismic moments are 4 4 10 18 nm m w 6 4 and 5 0 10 18 nm m w 6 5 the total moment released by the two events equals that generated by several decades of plate motion in the area but is only a fraction of the moment accumulated in the area since the last major earthquake in 1912

insar based sill model links spatially offset areas of deformation and seismicity for the 1994 unrest episode at eyjafjallajokull volcano iceland 1 we present insar observations of deformation due to an intrusion in the eyjafjallajokull volcano southern iceland in 1994 more than 15 cm of deformation in the line of sight los direction is detected in a series of interferograms spanning a micro earthquake swarm occurring in june 1994 the location of the seismicity is more than 6 km offset compared to the area of inferred maximum surface uplift through an inversion scheme we find that a horizontal sill intrusion experiencing variable opening of up to 0 36 m agrees well with the deformation data the total intrusion volume is 0 017 km3 the northern periphery of the modeled intrusion fits well with the area of recorded seismicity indicating a close connection several processes may be responsible our preferred explanation is that the earthquakes are caused by opening of a narrow magma channel from depth feeding the sill

estimation of erosion deposition and net volumetric change caused by the 1996 skeiðararsandur jokulhlaup iceland from synthetic aperture radar interferometry using repeat pass satellite synthetic aperture radar interferometry we develop a methodology to measure flood induced erosion and deposition and apply it to a record 1996 glacier outburst flood jokulhlaup on skei ararsandur iceland the procedures include 1 coregistration of backscatter intensity images to observe morphological differences 2 mapping of interferometric phase correlation to identify preserved and modified surfaces and 3 construction correction and differencing of pre jokulhlaup and post jokulhlaup topography procedures 1 and 2 are robust and should be widely applicable to other fluvial environments while procedure 3 is complicated by uncertainties in phase measurement baseline estimate and atmospheric effects after a correction procedure involving interpolation of digital elevation model elevation differences across low correlation areas we find 4 m of elevation change are required to calculate volumes of erosion or deposition this condition was satisfied for the 40 km2 proglacial zone of skei ararsandur where we estimate 38 106 m3 of net sediment deposition along the ice margin 2 106 m3 of net erosion in channels downstream and a total net balance of 13 106 these estimates are supported by field observations and survey data collected in 1997

formation of oskjuvatn caldera at askja north iceland mechanism of caldera collapse and implications for the lateral flow hypothesis the oskjuvatn caldera at askja volcano north iceland was formed as a result of an explosive eruption at askja on 28th 29th march 1875 oskjuvatn is one of the youngest collapse calderas on earth and its initiation and growth were observed and documented by explorers and geologists working in the askja region between 1875 and 1932 it is an example of caldera formation where the volume of the caldera collapse far exceeds the volume of associated erupted products the discrepancy between the collapse volume and associated erupted products has been used by previous workers as a justification for the hypothesis that the injection of lateral dykes from askja fed the february to october 1875 n jahraun fissure eruptions at the sveinagja graben some 60 km north of askja however historical accounts documenting the caldera formation in sufficient detail show clearly that oskjuvatn formed by piecemeal collapse taking over 40 years to reach its current form we use these accounts to undertake a detailed examination of the stages of caldera collapse and to compare them with the known magmatic output of askja in the years following the 1875 eruption arcgis software was used to calculate the volume of oskjuvatn during the various stages of collapse and the volume of material erupted after 1875 while a dyke extending between askja and sveinagja may be implied to account for the missing volume our results demonstrate that the volume of oskjuvatn in july 1875 closely corresponds to the volume of rhyolitic material erupted on 28th 29th march 1875 in addition geochemical evidence indicates that the n jahraun magmas were sourced from a deeper reservoir rather than by lateral injection from askja s shallow crustal magma chamber we therefore suggest that the injection of sills and dykes in a coherent intrusion complex beneath askja central volcano combined with background deflation of the magma storage zone beneath oskjuvatn caldera over 30 to 40 years following 1875 satisfactorily accommodates the volume required to form oskjuvatn caldera

structures involved in the vertical deformation at lake taupo new zealand between 1979 and 2007 new insights from numerical modelling abstract since 1979 repeat levelling measurements have been conducted on the lake filling the caldera of the dormant taupo rhyolitic volcano in the north island of new zealand interpretation of these data through numerical modelling provides information on the structures involved in the relative vertical crustal movement throughout the southern end of the taupo volcanic zone tvz an area of active back arc extension the best defined feature is a long term global subsidence of the northern part of the lake 7 mm yr 1 due to the cumulative effect of the crust stretching and a deep deflation source this long term subsidence is occasionally disturbed by strong short term uplifts linked with overpressure sources located below the northern part of the lake near active geothermal fields episodes of uplift can be attributed to various combinations of the following two processes taking place beneath the geothermal field 1 movement or formation of rhyolitic magma deepest sources 2 pressurization of the shallow hydrothermal fluid reservoir that traps volatiles exsolved from a crystallizing rhyolitic magma shallowest sources the pressurization of the shallow hydrothermal system gives rise to tensional stresses in the upper crust resulting in seismic and aseismic fault ruptures slow slip motion of the kaiapo fault decouples on a short term time scale the ground deformation pattern on both sides of the fault our results discriminating what parts of the deformation are due to the regional setting the hydrothermal circulations and the seismic activity reveal that each seismic swarm is preceded by 1 to 3 years of inflation of the eastern part of the lake this systematic behaviour may allow us in the future to better predict the occurrence of the seismic swarms below the lake

the misis andirin complex a mid tertiary melange related to late stage subduction of the southern neotethys in s turkey abstract the mid tertiary mid eocene to earliest miocene misis andirin complex documents tectonic sedimentary processes affecting the northerly active margin of the south tethys neotethys in the easternmost mediterranean region each of three orogenic segments misis in the sw andirin central and engizek in the ne represent parts of an originally continuous active continental margin a structurally lower volcanic sedimentary unit includes late cretaceous arc related extrusives and their lower tertiary pelagic cover this unit is interpreted as an early tertiary remnant of the mesozoic south tethys the overlying melange unit is dominated by tectonically brecciated blocks 100 m across of mesozoic neritic limestone that were derived from the tauride carbonate platform to the north together with accreted ophiolitic material the melange matrix comprises polymict debris flows high to low density turbidites and minor hemipelagic sediments the misis andirin complex is interpreted as an accretionary prism related to the latest stages of northward subduction of the south tethys and diachronous continental collision of the tauride eurasian and arabian african plates during mid eocene to earliest miocene time slivers of upper cretaceous oceanic crust and its early tertiary pelagic cover were accreted while blocks of mesozoic platform carbonates slid from the overriding plate tectonic mixing and sedimentary recycling took place within a trench subduction culminated in large scale collapse of the overriding northern margin and foundering of vast blocks of neritic carbonate into the trench a possible cause was rapid roll back of dense downgoing mesozoic oceanic crust such that the accretionary wedge taper was extended leading to gravity collapse melange formation was terminated by underthrusting of the arabian plate from the south during earliest miocene time collision was diachronous in the east engizek range and se anatolia collision generated a lower miocene flexural basin infilled with turbidites and a flexural bulge to the south miocene turbiditic sediments also covered the former accretionary prism further west misis range the easternmost mediterranean remained in a pre collisional setting with northward underthrusting incipient subduction along the cyprus arc the lower miocene basins to the north misis and adana indicate an extensional to transtensional setting the ne sw linking segment andirin probably originated as a mesozoic palaeogeographic offset of the tauride margin this was reactivated by strike slip and transtension during later tertiary diachronous collision related to on going plate convergence the former accretionary wedge upper plate was thrust over the lower miocene turbiditic basins in mid late miocene time the plio quaternary was dominated by left lateral strike slip along the east anatolian transform fault and also along fault strands cutting the misis andirin complex

the tertiary geodynamical evolution of the aegean arc a paleomagnetic reconstruction abstract the paleomagnetic results obtained in the last 5 6 years from tertiary formations in the aegean domain indicate that the lower miocene arc was almost rectilinear with an e w trend and that its curvature has been acquired tectonically in two major phases during the middle miocene a first phase of deformation is characterized by rotations occurring at the two terminations of the arc clockwise in the west epirus anticlockwise in the east southeastern anatolia a second phase of rotation occurring in the last 5 ma about a pole situated in the southern adriatic sea has affected only the northwestern part the data also indicate that the antalya basin has not been involved in the geodynamical evolution of the arc so that the bey daglari represent its easternmost unit a more complex rotational pattern is observed in the internal zones the large rotations measured in evia 48 and skyros 26 probably occurred in the last 5 ma and result from rotation of fault bounded blocks in a shear zone connecting the north aegean trough to the external arc in the izmir region in the karaburun peninsula of western anatolia and in the island of lesbos significant counterclockwise clockwise or null rotations of coherent blocks have taken place during the neotectonic extensional regime furthermore the values of the inclination obtained from both sedimentary and volcanic oligo miocene formations are systematically shallower than expected on the basis of a geocentered dipole field this suggests that the entire studied area has undergone a northward drift of over 1000 km since the middle miocene

deformation in the northern volcanic zone of iceland 2008 2014 an interplay of tectonic magmatic and glacial isostatic deformation gps measurements spanning 2008 to 2014 are used to derive the surface velocity field across the northern volcanic zone nvz of iceland a subaerial part of the divergent boundary between the north american and eurasian plates no volcanic activity nor magmatic intrusions were detected in the zone during this time period we infer an extensional rate of 17 4 0 3 0 2 mm yr in direction 292 0 0 6 0 5 consistent with the results of previous studies and current plate motion models including morvel2010 and geodvel2010 the horizontal velocity field reveals about 50 km wide stretching zone caused by the divergent plate movements glacial isostatic adjustment gia induces uplift of over 20 mm yr at the northern edge of vatnajokull ice cap and 3 4 mm yr horizontal motion directed away from the ice cap deformation in the nvz between 2008 and 2014 can be reproduced by a combination of models relating to several different processes i mogi sources for volcanic and geothermal deformation at the askja and krafla volcanoes ii scaled version of a velocity field derived from a glacial isostatic model and iii simple arctangent based model for secular plate spreading we find the approximate location of the plate boundary spreading axis as well as its locking depth the spreading axis lies through the krafla fremrinamar and askja central volcanoes the most active ones in the nvz it does not appear to follow the general direction of each fissure swarm but rather to change direction at the central volcanoes the locking depth is on average within the 7 9 km range

plate boundary deformation and man made subsidence around geothermal fields on the reykjanes peninsula iceland abstract we present interferometric synthetic aperture radar insar data from 1992 1999 and 2003 2008 as well as gps data from 2000 2009 for the active plate boundary on the reykjanes peninsula southwest iceland the geodetic data reveal deformation mainly due to plate spreading anthropogenic subsidence caused by geothermal fluid extraction and possibly increasing pressure in a geothermal system subsidence of around 10 cm is observed during the first 2 years of production at the reykjanes geothermal power plant which started operating in may 2006 we model the surface subsidence around the new power plant using point and ellipsoidal pressure sources in an elastic halfspace short lived swarms of micro earthquakes as well as aseismic fault movement are observed near the geothermal field following the start of production possibly triggered by the stresses induced by geothermal fluid extraction

gravity and elevation changes at askja iceland ground tilt measurements demonstrate that askja is in a state of unrest and that in the period 1988 1991 a maximum 48 3 rad tilt occurred down towards the centre of the caldera this is consistent with 126 mm of deflation at the centre of the caldera with a 2 5 3 0 km depth to the source of deformation the volume of the subsidence bowl is 6 2x106 m3 when combined with high precision microgravity measurements the overall change in sub surface mass may be quantified after correction for the observed elevation change using the free air gradient of gravity measured for each station the total decrease in mass is estimated to be less than 109 kg a small residual ground inflation and net gravity increase in the southeastern part of the caldera may be caused by dyke intrusion in this region the minimum dimensions of such an intrusion or complex of intrusions are 1 m width up to 100 m deep and up to several hundred metres thick

miocene remagnetisation of carbonate platform and antalya complex units within the isparta angle sw turkey abstract a palaeomagnetic study has been carried out within the mesozoic and tertiary units of the relatively autochthonous carbonate platforms and the allochthonous deep sea volcanics and sediments of the antalya complex exposed around the isparta angle sw turkey the antalya complex is interpreted as a mosaic of carbonate platforms basinal sediments volcanic and ophiolitic rocks which formed within a southerly strand of the neotethyan ocean adjacent to gondwana the results indicate a widespread remagnetisation event negative fold tests show that the remanence at most sites is of secondary origin e g within the cirali lavas the magnetisation is carried by magnetite of presumed authigenic origin the remagnetisation event is believed to have occurred in the early middle miocene burdigalian langhian it was possibly triggered by the migration of orogenic fluids ahead of the advancing lycian nappes during their emplacement onto the carbonate platforms subsequent to remagnetisation a large segment of the isparta angle underwent an anticlockwise rotation of 30 this rotation is attributed to the overall convergence and bending of the hellenic arc and the final stages of emplacement of the lycian nappes during the late miocene in agreement with previous studies previously southerly palaeolatitudes were inferred from late triassic extrusives of the godene zone calbali dag unit the post folding magnetisation identified here within the cirali lavas of the godene zone to the south implies that these low palaeolatitudes result from the inappropriate application of structural tilt corrections the available data cannot be used to substantiate an origin for the antalya units south of the equator in the early mesozoic instead a position close to the northern margin of gondwana is indicated

crustal deformation associated with the 1996 gjalp subglacial eruption iceland insar studies in affected areas adjacent to the vatnajokull ice cap abstract crustal deformation signals associated with the september 30 october 13 1996 gjalp subglacial eruption vatnajokull ice cap iceland have been identified using interferometric analysis of synthetic aperture radar images insar in areas outside the ice cap on september 29 1996 an mw 5 6 earthquake occurred at the nearby bardarbunga volcano and on september 30 seismicity propagated 20 km southwards where the gjalp eruption occurred analysis of interferograms spanning different times from 1992 to 2000 allows us to separate two distinct co eruptive deformation periods in areas outside the ice cap diking at the bardarbunga caldera rim appears to be responsible for deformation during the first week of eruption while significant deflation occurred at bardarbunga only after october 6 when most of the magma had already been erupted at gjalp a pressure connection between the bardarbunga volcano and the gjalp eruptive fissure is inferred fault slip in three areas up to 30 km from the center of the bardarbunga volcano was triggered by the deflation local deformation signals there are consistent with small fault movements

direction of ophiolite emplacement inferred from cretaceous and tertiary sediments of an adjacent autochthon the bey daglari southwest turkey the late mesozoic to mid tertiary depositional history of an autochthonous block in southwest turkey is outlined in relation to the direction of emplacement of adjacent allochthonous units in this area a lively debate persists as to whether the antalya complex located along the mediterranean coast should be correlated with the lycian nappes sited to the northwest in central western anatolia both allochthonous bodies include mesozoic ophiolites and similar shallow to deep water sedimentary facies correlation of the antalya complex and the lycian nappes requires transport over the adjacent autochthon the bey daglari here field data from the southern part of the bey daglari are used to trace the depositional history of the autochthon from late cretaceous to late miocene time a pattern of late mesozoic pelagic carbonate deposition giving way to more heterogeneous sedimentation in the early tertiary is documented by early miocene the autochthon was blanketed by a thick sequence of miocene elastics mostly derived from an ophiolite evidence from sedimentary structures shows that transport was from the east and northeast depositional models are advanced which involve an early miocene delta submarine fan giving way in later miocene times to an alluvial fan demonstration that in this area the ophiolite material was derived from the east provides additional important evidence of the existence of a southerly mesozoic oceanic basin distinct in origin from the lycian nappes to the north

the 2008 may 29 earthquake doublet in sw iceland summary on 2008 may 29 an earthquake doublet shook the southwestern part of iceland the first main shock originated beneath mt ingolfsfjall located near the western margin of the south iceland seismic zone sisz approximately 40 km east of the capital reykjavik immediate aftershock activity was recorded by the sil seismic network operated by the icelandic meteorological office imo with both n s and e w structures illuminated over a broad area a continuous gps cgps network also operated by the imo recorded coseismic offsets with up to 200 mm of horizontal motion at the closest stations we estimate the coseismic surface deformation observed by campaign and continuous gps and satellite radar data insar we invert the geodetic data to find the optimal geometry location and slip on the main faults accounting for variation in the elastic parameters of the crust with depth our models indicate that most of the slip occurred on two n s structures spaced 5 km apart from a joint inversion of gps and insar data for variable slip models we find that most of the slip for the first ingolfsfjall event was concentrated at 2 4 km depth with a maximum of 1 9 m whereas the slip on the second kross fault was located deeper at 3 6 km depth with up to 1 4 m of motion the models give similar geodetic moments for the two main events equivalent to a moment magnitude of mw5 8 and mw5 9 for the first and second event respectively our estimated composite moment therefore equals a mw6 1 for the doublet smaller than the mw6 3 estimated from teleseismic data e g neic and harvard the geodetic data support rupture on two main faults and analysis of high rate 1 hz cgps data suggests that slip on the second fault initiated within 3 s of the first main shock static coulomb failure stress calculations indicate that the first event caused a stress increase in the area of the main asperity i e at the location of the largest slip patch on the second fault however we cannot rule out dynamic stress triggering due to the short time between the two main events the 2008 may 29 earthquake doublet appears to be a continuation of the earthquake sequence that started in 2000 june when two mw6 5 events struck the eastern and central part of the south iceland seismic zone in the span of 81 hr the 2000 june 2008 may sequence has released about half of the moment accumulated by plate motion since the previous earthquake sequence in 1896 1912 therefore continued earthquake activity with moderate size events rupturing n s faults in the sisz in the coming decades is likely

rheologic controls on inter rifting deformation of the northern volcanic zone iceland article i nfo extensional rifts are characterized by significant lateral variations in crustal rheology as lithospheric material cools and advects away from the rift axes nevertheless most models used for modeling of crustal movements consist of horizontal layers with uniform properties this paper explores the role spatial variation of rheological properties play in modifying the style of surface deformation at rifts by comparing finite element model predictions to inferred inter rifting surface deformation in iceland s northern volcanic zone crustal deformation has been observed by satellite radar interferometry insar and gps measurements extension is observed across the entire northern rift zone whereas subsidence occurs in two distinct areas corresponding to mapped fissure swarms where major rifting took place in 1975 1984 and 1874 1876 respectively our models indicate that the observed inter rifting plate spreading deformation field is controlled by rheological variations within the en echelon arrangement of fissure segments and that a central ridge axes model does not apply uniform stretching across a plate boundary zone where fissure swarms are weaker than the surrounding crust and reflect the surface expression of the rift reproduces the characteristics of the deformation field the most realistic fissure swarm structure consists of a wedge of

deep magma storage at hekla volcano iceland revealed by insar time series analysis 1 hekla volcano is one of the most active volcanoes in iceland the most recent eruption occurred from 26 february to 8 march 2000 when about 0 19 km3 of magma was erupted we present deformation data from multitemporal analyses of synthetic aperture radar sar images acquired between 1993 and 2008 focusing on pixels with low phase variance using persistent scatterer and small baseline approaches prior to and after the 2000 eruption we find a broad area of inflation around the volcano radius about 20 km with satellite line of sight los shortening of up to 5 mm yr we interpret this signal as the result of pressure increase in a deep seated magma chamber which we model as a spherical source at 14 20 km depth increasing in volume by 0 003 0 02 km3 yr within a 6 km radius of the summit of the volcano a los lengthening is superimposed on the broad inflation signal which correlates partly with recent lava flows we interpret this signal as the result of thermally contracting lava flows combined with viscoelastic yielding due to the load of the volcano and its lavas coeruptive deflation during the 2000 eruption was similar to the cumulative inflation from 1993 to 2000 and is consistent with a spherical magma chamber at 14 18 km depth that decreases in volume by 0 04 0 08 km3 interferograms spanning the 2000 eruption show a local coeruptive deformation signal near the eruptive fissure this is consistent with a dike opening from the surface to depths up to 5 8 km with a volume of 0 005 0 006 km3

geodetic data shed light on ongoing caldera subsidence at askja iceland subsidence within the main caldera of askja volcano in the north of iceland has been in progress since 1983 here we present new ground and satellite based deformation data which we interpret together with new and existing micro gravity data to help understand which processes may be responsible for the unrest from 2003 to 2007 we observe a net micro gravity decrease combined with subsidence and from 2007 to 2009 we observe a net micro gravity increase while the subsidence continues we infer subsidence is caused by a combination of a cooling and contracting magma chamber at a divergent plate boundary mass movements at active volcanoes can be caused by several processes including water table lake level movements hydrothermal activity and magma movements we suggest that here magma movement and or a steam cap in the geothermal system of askja at depth are responsible for the observed micro gravity variations in this respect we rule out the possibility of a shallow intrusion as an explanation for the observed micro gravity increase but suggest magma may have flowed into the residing shallow magma chamber at askja despite continued subsidence in particular variable compressibility of magma residing in the magma chamber as well as compressibility of the surrounding rock may be the reason why this additional magma did not create any detectable surface deformation

recoil emanation theory applied to radon release from mineral grains abstract in this paper the recoil emanation theory is presented as a major mechanism for rn release from solid materials the basic theory is developed for rn emanation from geometrical shapes spheres and cylinders having variable thickness of precursor ra containing material subsequently a sphere pore model of emanation from mineral grains like those in rocks soils etc is developed in this model a surface of the grain is constructed as a superposition of in and out directed spherical caps and cylindrical pores the model incorporates processes like rn embedding pore overlap water effect and emanation from the edges using such a geometrical model it is shown how the rn emanating power measurements can give a clue to the ra distribution and surface properties of the samples in particular it is shown that for grains reasonably larger than the recoil range and for surface ra distribution the emanating power is independent of the grain size but the total ra concentration varies with the reciprocal of the grain size the opposite is true for ra distributed uniformly throughout the volume of the grain it is shown how the rn emanating power is related to the surface porosity of the grain also implications are made with respect to u transport in nature and with respect to low emanating power from lunar soil finally a failure of the emanation theory is discussed to reproduce emanation curves for the samples having high specific surface areas and ra distributed throughout the volume

iceland rising solid earth response to ice retreat inferred from satellite radar interferometry and visocelastic modeling a broad uplift occurs in iceland in response to the retreat of ice caps which began circa 1890 until now this deformation signal has been measured primarily using gps at points some distance away from the ice caps here for the first time we use satellite radar interferometry interferometric synthetic aperture radar to constrain uplift of the ground all the way up to the edge of the largest ice cap vatnajokull this allows for improved constraints on the earth rheology both the thickness of the uppermost earth layer that responds only in an elastic manner and the viscosity below it the interferometric synthetic aperture radar velocities indicate a maximum displacement rate of 24 4 and 31 4 mm yr at the edge of vatnajokull during 1995 2002 and 2004 2009 respectively the fastest rates occur at outlet glaciers of low elevation where ice retreat is high we compare the observations with glacial isostatic adjustment models that include the deglaciation history of the icelandic ice caps since 1890 and two earth layers using a bayesian approach we derived probability density functions for the average earth model parameters for three satellite tracks based on our assumptions the three best fit models give elastic thicknesses in the range of 15 40 km and viscosities ranging from 4 10 1018 pa s

the fissure swarm of the askja volcanic system along the divergent plate boundary of n iceland divergent plate boundaries such as the one crossing iceland are characterized by a high density of subparallel volcanic fissures and tectonic fractures collectively termed rift zones or fissure swarms when extending from a specific volcano volcanic fissures and tectonic fractures in the fissure swarms are formed during rifting events when magma intrudes fractures to form dikes and even feeds fissure eruptions we mapped volcanic fissures and tectonic fractures in a part of the divergent plate boundary in northern iceland the study area is 1 800 km2 located within and north of the askja central volcano the style of fractures changes with distance from askja close to askja the swarm is dominated by eruptive fissures the proportion of tectonic fractures gets larger with distance from askja this may indicate that magma pressure is generally higher in dikes close to askja than farther away from it volcanic fissures and tectonic fractures are either oriented away from or concentric with the 3 4 identified calderas in askja the average azimuth of fissures and fractures in the area deviates significantly from the azimuth perpendicular to the direction of plate velocity as this deviation decreases gradually northward we suggest that the effect of the triple junction of the north american eurasian and the hreppar microplate is a likely cause for this deviation shallow tectonic earthquakes in the vicinity of askja are often located in a relatively unfractured area between the fissure swarms of askja and kverkfjoll these earthquakes are associated with strike slip faulting according to fault plane solutions we suggest that the latest magma intrusions into either the askja or the kverkfjoll fissure swarms rotated the maximum stress axis from being vertical to horizontal causing the formation of strike slip faults instead of the dilatational fractures related to the fissure swarms the activity in different parts of the askja fissure swarm is uneven in time and switches between subswarms as shown by a fissure swarm that is exposed in an early holocene lava nw of her ubrei but disappears under a younger 3500 4500 bp lava flow we suggest that the location of inflation centres in askja central volcano controls into which part of the askja fissure swarm a dike propagates the size and amount of fractures in the kollottadyngja lava shield decrease with increasing elevation we suggest that this occurred as the depth to the propagating dike s was greater under central kollottadyngja than under its flanks due to topography

multiple melt injection along a spreading segment at askja iceland lower crustal earthquakes 12 25 km depth have been detected since august 2005 in the askja volcanic system along the north iceland rift in the normally ductile part of the crust the earthquakes occur in three clusters which have stable dimensions and locations through time and are interpreted as positions of repeated melt supply from the mantle to the lower crust seismic velocity vp vs ratios are consistent with the presence of partial melt in the lower crust at askja the spatial separation of the clusters shows that there are multiple positions of melt injection within this one magmatic segment and all three positions are currently active this pattern of melt supply is more like that observed on fast spreading ridges than slow spreading ridges and is probably a consequence of the increased melt production beneath iceland compared to the rest of the mid atlantic ridge however the relative number of earthquakes in each cluster shows that two thirds of the melt is supplied to the central volcano askja i e segment center during the last major rifting episode shallow lateral melt migration occurred from the magma chamber beneath the volcano therefore on long time scales melt supply is probably greater at the segment center with melt redistribution in the upper crust even though there are multiple points of lower crustal injection along the segment

wrench and thrust tectonics along a mesozoic cenozoic continental margin antalya complex sw turkey the segment of the antalya complex w of antalya bay displays the results of latest cretaceous to miocene deformation on a previously passive mesozoic continental margin the 300 km 2 area detailed here includes parts of from w to e a mesozoic carbonate platform its bordering sediment margin and the adjacent marginal oceanic crust with sediment cover the platform is folded on n s axes and has been overthrust westward by its sediment margin this thin sediment sequence has been detached from its basement in a spectacular w verging imbricate thrust belt similar though less organized westward thrusting occurs in the thin sediment cover to the marginal oceanic crust and may also affect the igneous basement itself however this part of the margin is dominated by an array of anastomosing subvertical screens of serpentinite up to several kilometres wide these are thought to be cool upward protrusions of the hydrated ultramafic substratum to the marginal crust into a then active braided strike slip fault system the fault strands now divide the intact marginal rocks into large lozenges some of which have oblique and sigmoidal structures and steeply plunging folds the thrust and wrench tectonics may have operated in concert in a regionally transpressive regime or thrusting may have accompanied only the initiation of wrench tectonics the local interplay of transpression and transtension was partly responsible for the present complexity of the area even more important was the original mechanical inhomogeneity of the margin particularly the inclusion of rifted off continental fragments in the marginal ocean crust and the strong basement cover contrasts on the margin

sandy high energy flood sedimentation some criteria for recognition with an example from the devonian of s w england abstract many modern sand deposits resulting from episodic floods in semi arid zones are dominated by parallel laminations but parallel laminated sands are not a major feature in perennial streams single flood events may deposit over 1 5 m of parallel laminated sand hence ancient parallel laminated sand dominated alluvial deposits may be the product of ephemeral flows the trentishoe formation hangman sandstone group middle devonian of north devon consists in part of laterally extensive beds of parallel laminated fine grained red sandstones that build multistorey sand bodies individual beds are little more than 1 m thick but may extend laterally for hundreds of metres a vertical sequence of erosion surface sparse silt clasts parallel laminations silt drape is often found suggesting high flow stage deposition of plane bedded sand followed by a very rapid waning of flow with silt fallout in the final stages of the flood this sequence bears marked similarity to certain modern ephemeral flow sands

magma transport and storage at piton de la fournaise la reunion between 1972 and 2007 a review of geophysical and geochemical data abstract since the middle of the 20th century improvement in volcano monitoring techniques has provided large data sets that can be used to evaluate the evolution of magma plumbing systems at piton de la fournaise volcano abundant eruptive activity and a dense monitoring network are especially conducive to such research analysis of the extensive set of geophysical and geochemical data associated with the last 35 years of activity provides new insights into magma transport and storage at piton de la fournaise two periods of frequent eruptions separated by 6 years of inactivity can be distinguished 1972 1992 and 1998 2007 considering these two periods we show evidence of major changes in the shallow plumbing system in 2000 during 1972 1992 and 1998 2000 lava compositions and weak long term eruptive precursors lasting few days to three weeks characterized by no significant summit inflation and about ten volcano tectonic earthquakes per day suggest that eruptions were fed by the progressive drainage of an occasionally recharged shallow magma reservoir geophysical evidence of shallow magma reservoir recharge was only recorded in 1986 and 1998 in contrast from 2000 to 2007 geophysical data highlight the appearance of long term precursors 1 to 5 months of summit inflation and strong seismicity up to one hundred events per day preceding cycles of successive eruptions each cycle of eruptions was characterized by a sequence 3 to 10 months in duration of summit and near summit proximal eruptions and ended with a distal low altitude oceanite olivine abundances 20 vol eruption on the eastern flank of the volcano within each of these eruptive cycles lavas became progressively more magnesian over time the preferential motion of the eastern flank caused by continuous recharging of the shallow reservoir since 2000 would favour the occurrence of distal eruptions towards this flank at the end of a cycle

deflation of the askja volcanic system constraints on the deformation source from combined inversion of satellite radar interferograms and gps measurements the askja central volcano in northern iceland has been continuously subsiding at least since 1983 gps and optical leveling tilt measurements show subsidence of at least 75 cm from 1983 to 1998 in the center of the askja caldera without any eruptive activity we have performed an interferometric analysis of synthetic aperture radar images insar of the area utilizing data from the ers satellites we observe subsidence of the askja caldera and its fissure swarm up to a distance of 25 km from the volcano we evaluate the geometry of the magma chamber at askja from a combined inversion of satellite radar interferograms and gps measurements several models were tested including a mogi point source as well as an ellipsoidal source the use of an ellipsoidal source instead of a mogi source gives an estimate of the dimensions of the magma chamber and its deflating pressure whereas these parameters are not independently resolved if a mogi source is used two source models were also considered in order to explain the additional subsidence observed along the askja fissure swarm we tested a model using two mogi sources at different depths a shallow ellipsoidal cavity with a deeper mogi source and then a shallow mogi source with a deeper elongated ellipsoid oriented along the fissure swarm results indicate that an ellipsoidal source at about 3 km depth can accommodate most of the deflation occurring in the caldera residual subsidence occurs along the askja fissure swarm suggesting the existence of a deeper source of contraction we interpret this signal in terms of subsidence of the plate boundary

patterns of reef sedimentation and diagenesis in the miocene of cyprus abstract an early tertiary regressive sedimentary succession developed along an active plate margin in cyprus a varied clastic and carbonate succession of the miocene pakhna formation and then messinian evaporites culminate the regression within the pakhna formation two phases of reef growth were developed the aquitanian burdigalian terra member and the tortonian koronia member the terra member is exposed only in west and southeast cyprus mainly between pelagic carbonates the koronia member is exposed around the margins of the troodos massif in north south and west cyprus and on the akamas peninsula in northwest cyprus there was little tectonic influence on the growth pattern of the terra member reefs the koronia member reefs however are developed on up faulted blocks most of the koronia member fore reef facies and associated clastic input was shed into downfaulted basinal depocentres there are differences between the first and second miocene reef phases in cyprus in primary reef construction and in the level of background carbonate pelagic sedimentation the terra member reefs are dominantly framestones comprising faviids and domal poritids with several types of secondary reef dwelling corals there is no indication of a connection with the indo pacific coral faunal province benthonic foraminifera and fragments of crustose coralline algae are abundant in the off reef by contrast the koronia member is a bindstone comprising virtually monospecific laminar poritid corals but with coralline algae also playing a role in encrustation the koronia member off reef facies comprises decimetre thick beds of bioclastic reef detritus in north cyprus however beds of similar detritus centimetres in thickness are overlain by progressively thicker up to several metres debris flow sheets the terra member reefs have limited acicular fringe cement probably aragonitic this is overlain by an abundant marine bladed formerly high mg calcite cement later cements present in the reef facies include micritised calcite spars perhaps indicating microboring in cements during their precipitation neomorphism was extensive converting most cements to low mg calcite stable isotopic data for all the cyprus calcites exhibit depletion in the heavier isotopes 18 o and 13 c indicative of meteoric alteration the koronia member limestones show abundant indication of early lithification with fringing acicular aragonite and micrite cements stable isotopic data of the botryoidal aragonite cements indicate a marine origin the dolomite is thought to result from marine freshwater mixing and to be of pliocene age on the basis of stratigraphical solution replacement fabric and stable isotopic data sr isotopic data do not contradict a pliocene age dolomite characteristically replaces the pliocene fissure fill contents in southeast cyprus and off reef horizons in the terra member of west cyprus and koronia member of north cyprus the growth and burial history of miocene reefs contribute to the understanding of the tectonic history and palaeogeographical evolution of cyprus

new evidence and model on the evolution of the southeast anatolian orogen this paper describes the orogenic evolution of the southeast anatolian orogenic belt based mostly on new geologic data collected from its constituent tectonic units in the course of new mapping programs of the past decade the southeast anatolian orogenic segment of the alpides may be divided into three approximately east west trending zones from south to north they are the arabian platform followed by a zone of imbrication and then a zone of nappes the arabian platform includes a mostly marine sedimentary succession deposited from early cambrian to middle miocene time the zone of imbrication is a narrow belt sandwiched between the arabian platform and the zone of nappes it consists of imbricated thrust slices emplaced onto a late cretaceous to early miocene sequence the zone of nappes is the highest tectonic unit consisting of two stacks of nappes simply designated the lower and upper nappes the lower nappe is represented by the slices of a polyphase metamorpbic ophiolitic assemblage and the maden group the upper nappe rests on the lower nappe and is represented by the bitlis and poturge metamorphic massifs southeastern anatolia underwent two major episodes of alpide deformation the first occurred during the late cretaceous period when ophiolite was emplaced on the arabian platform this event was not the consequence of a continental collision the ophiolite obduction onto the arabian platform was followed by a regionwide extension and a new marine transgression over the platform immediately after the ophiolite obduction the second episode of deformation occurred during middle eocene miocene time in two distinct stages as a result of the progressive elimination and complete closure of the ocean s which led to the collision between the zone of nappes located to the north being a part of eurasia and the arabian plate the maden marginal basin formed north of the subduction zone that eliminated the ocean between eurasia and arabia along the southern margin of the taurus belt and abutted the arabian plate much later during the final collision the second episode of deformation formed the present orogenic segment leading to the amalgamation of different tectonic units these amalgamated nappes collided with the arabian plate and welded onto it at the latest stage of the orogenic evolution during the miocene epoch

correlations of radon and carbon isotopic measurements with petroleum and natural gas at cement oklahoma radon in soil gas and the carbon isotopic composition of carbon compounds in soil have been measured at 98 sites over the cement oklahoma oil and gas field strong correlations were observed between the density of oil and gas wells and storage tanks and soil 222rn field 222rn vertical gas flow and 13c gradients no meaningful correlation is seen with 13c if further study shows that these results are general the types of measurement done here could facilitate exploratory drilling

mechanisms of radon loss from zircon microstructural controls on emanation and diffusion abstract understanding how radon escapes from minerals is important for many fields in earth science yet few studies have focused on the mechanisms for radon escape we measured radon emanation rate and radon loss upon heating for crushed aliquots of three large zircon crystals from three localities mud tank australia bancroft canada and malawi africa our study in conjunction with published data shows that the room temperature radon emanation coefficient rec varies over 5 orders of magnitude in zircon for low u zircon mud tank there are variations in rec that appear to be related to annealing at different temperatures possibly due to annealing of fission tracks however all rec values for mud tank zircon are within error of one another bancroft and malawi zircons have higher u content and do not show any systematic relationship of rec to annealing temperature results from mud tank zircon suggest that partial annealing of fission tracks decreases rec but when all fission tracks are annealed rec reaches a maximum rec in zircons with high u content bancroft and malawi is slightly higher than in zircon with lower u although results are within error results of measurements of radon loss upon heating suggest that radon diffusion is slow 30 of the radon is lost during heating at 975 c for 48 h samples heated a second time yield less fractional radon loss 10 suggesting that diffusion parameters are changed during heating at temperatures 975 c which is likely the result of annealing of radiation damage diffusion parameters calculated from the fractional loss experiments reflect diffusion in highly radiation damaged or metamict zircons our results indicate that internal microstructures in zircon such as fission tracks and alpha radiation damage influence radon escape for diffusion and recoil mechanisms and hence if these effects can be further characterized measurements of 222rn escape have the potential to be useful for probing the internal structure of zircon and other u bearing minerals

first paleomagnetic evidence for a post eocene clockwise rotation of the western taurides thrust belt east of the isparta reentrant southwestern turkey abstract a paleomagnetic study was carried out on 23 sites sampled in paleocene eocene and lower miocene sedimentary formations of the western taurides belt east of the isparta reentrant the paleomagnetic data based on twelve suitable sites record a coherent post eocene 40 clockwise rotation throughout the area studied we interpret this regional rotation as a semi rigid rotation of the whole western taurides belt above a major deep decollement level together with previously published data these new results suggest that the isparta reentrant would result from diachronous opposite rotations of the two branches first a late eocene oligocene clockwise rotation of the akseki beysehir taurides initiating the tauride arc and then anticlockwise rotation of the lycian taurides probably during middle miocene times

icelandic rhythmics annual modulation of land elevation and plate spreading by snow load we find strong correlation between seasonal variation in cgps time series and predicted response to annual snow load in iceland the load is modeled using green s functions for an elastic halfspace and a simple sinusoidal load history on iceland s four largest ice caps we derive e 40 15 gpa as a minimum value for the effective young s modulus in iceland increasing with distance from the eastern volcanic zone we calculate the elastic response over all of iceland to maximum snow load at the ice caps using e 40 gpa predicted annual vertical displacements are largest under the vatnajokull ice cap with a peak to peak seasonal displacement of 37 mm cgps stations closest to the ice cap experience a peak to peak seasonal displacement of 16 mm consistent with our model east and north of vatnajokull we find the maximum of annual horizontal displacements of 6 mm resulting in apparent modulation of plate spreading rates in this area

comparative study of 222rn 40ar 39ar and 37ar leakage from rocks and minerals implications for the role of nanopores in gas transport through natural silicates we have measured the leakage of radiogenic 222rn and 40ar and reactor produced 39ar and 37ar in samples of granites plagioclase orthoclase cleavelandite and hornblende to assess the role of nanopores in gas transport through them the 39ar and 37ar were produced by fast neutron irradiation of the samples in vacuum sealed ampoules the leakage of all three ar isotopes was barely measurable in contrast the leakage of 222rn ranged between 1 45 18 1 orders of magnitude higher than that of the ar isotopes the extremely low ar isotope leakage suggests that the samples studied are not permeated by extensive nanopore networks which intersect grain surfaces the relatively high 222rn loss from these samples therefore has to be attributed to preferential enrichment of 226ra 238u on grain surfaces or to the existence of u th accessory minerals in or around grain boundaries from which substantial quantities of 222rn escape

1983 2003 decaying rate of deflation at askja caldera pressure decrease in an extensive magma plumbing system at a spreading plate boundary new deformation data from the askja volcano iceland show that the volcano s caldera has been deflating continuously for over 20 years and confirm that the rate of subsidence is slowing down the decay in subsidence rate can be fitted with a function of the form e t where is 39 years reanalysis of gps data from 1993 1998 show that these data can be fitted with a model calling for two mogi point sources one shallow and another one much deeper 16 2 km depth pressure decrease occurs in both sources the deeper source is responsible for observed horizontal contraction towards askja at distances that cannot be explained by the shallower source plate spreading of 19 mm year distributed evenly over about 100 km wide zone is also favoured by the data

a new method for measuring deformation on volcanoes and other natural terrains using insar persistent scatterers 1 we present here a new insar persistent scatterer ps method for analyzing episodic crustal deformation in non urban environments with application to volcanic settings our method for identifying ps pixels in a series of interferograms is based primarily on phase characteristics and finds low amplitude pixels with phase stability that are not identified by the existing amplitude based algorithm our method also uses the spatial correlation of the phases rather than a well defined phase history so that we can observe temporally variable processes e g volcanic deformation the algorithm involves removing the residual topographic component of flattened interferogram phase for each ps then unwrapping the ps phases both spatially and temporally our method finds scatterers with stable phase characteristics independent of amplitudes associated with man made objects and is applicable to areas where conventional insar fails due to complete decorrelation of the majority of scatterers yet a few stable scatterers are present

shallow magma accumulation at kīlauea volcano hawai i revealed by microgravity surveys for vertical displacement at the summit of about 1 3 m and 160 gal respectively the volume of magma lost based on grav ity data and assuming a reasonable magma density exceeded the volume of summit col lapse suggesting the creation of 40 90 10 6 abstract using microgravity data collected at k lauea volcano hawai i united states between november 1975 and january 2008 we document signifi cant mass increase beneath the east margin of halema uma u crater within k lauea s summit caldera surprisingly there was no sustained uplift accompanying the mass accumulation we propose that the positive grav ity residual in the absence of signifi cant uplift is indicative of magma accumulation in void space probably a network of interconnected cracks which may have been created when magma withdrew from the summit in response to the 29 november 1975 m 7 2 south fl ank earthquake subsequent refi lling documented by gravity represents a gradual recovery from that earthquake a new eruptive vent opened at the summit of k lauea in 2008 within a few hundred meters of the positive gravity residual maximum probably tapping the reservoir that had been accumulating magma since the 1975 earthquake

towards more realistic values of elastic moduli for volcano modelling abstract the accuracy of elastic analytical solutions and numerical models widely used in volcanology to interpret surface ground deformation depends heavily on the young s modulus chosen to represent the medium the paucity of laboratory studies that provide young s moduli for volcanic rocks and studies that tackle the topic of upscaling these values to the relevant lengthscale has left volcano modellers ill equipped to select appropriate young s moduli for their models here we present a wealth of laboratory data and suggest tools widely used in geotechnics but adapted here to better suit volcanic rocks to upscale these values to the scale of a volcanic rock mass we provide the means to estimate upscaled values of young s modulus poisson s ratio shear modulus and bulk modulus for a volcanic rock mass that can be improved with laboratory measurements and or structural assessments of the studied area but do not rely on them in the absence of information we estimate upscaled values of young s modulus poisson s ratio shear modulus and bulk modulus for volcanic rock with an average porosity and an average fracture density quality to be 5 4 gpa 0 3 2 1 gpa and 4 5 gpa respectively the proposed young s modulus for a typical volcanic rock mass of 5 4 gpa is much lower than the values typically used in volcano modelling we also offer two methods to estimate depth dependent rock mass young s moduli and provide two examples using published data from boreholes within k lauea volcano usa and mt unzen japan to demonstrate how to apply our approach to real datasets it is our hope that the data and analysis presented herein will assist in the selection of elastic moduli for volcano modelling to this end we provide a microsoft excel spreadsheet containing the data and necessary equations to calculate rock mass elastic moduli that can be updated when new data become available the selection of the most appropriate elastic moduli will provide the most accurate model predictions and therefore the most reliable information regarding the unrest of a particular volcano or volcanic terrain

222rn and 220rn emanations as a function of the absorbed α doses from select metamict minerals metamict minerals contain uranium and thorium which contribute to physical degradation or metamictization of their crystal structures over geologic time the damage occurs primarily through progressive overlapping recoil nuclei collision cascades from decay of 238u 232th 235u and their daughter products we measured 222rn and 220rn emanations from metamict samples of nine oxides brannerite davidite fergusonites pyrochlores samarskites and uraninite two phosphates monazites and eight silicates cerite gadolinites perrierite rinkite thorite turkestanite and vesuvianite the total absorbed doses ranged from 1 4 1015 to 6 1 1018 decay mg 1 for cerite and uraninite respectively the 222rn emanation coefficients varied from 5 10 5 uraninite to 2 5 turkestanite the 220rn emanation coefficients varied from 7 10 3 gadolinite ytterby to 6 2 gadolinite marysin the lowest 222rn emanation coefficients occurred among metamict minerals containing the highest concentrations of 238u i e uraninite samarskites and brannerite overall the 222rn and 220rn emanation coefficients observed in this study fall significantly below previously reported values

facies and tectonic significance of two contrasting miocene basins in south coastal turkey several miocene basins are developed on a mosaic of deformed mesozoic carbonate platforms and ophiolitic units in the antalya region of south west turkey two of these the manavgat and kopru basins show contrasting orientations and stratigraphies the manavgat basin is orientated broadly se nw and contains a succession of shallow water reef carbonates overlain by a thick sequence of deeper water marls the upper part of the succession consists of sandstones siltstones and conglomerates mainly deposited by gravity processes the stratigraphy of the n s kopru basin can be subdivided into a western part which consists of coarse fan delta conglomerates with local patch reefs and an eastern part with thinly bedded sandy turbidites tooi marks indicate north to south flow in the north of the basin but a southeasterly direction in the area of intersection with the manavgat basin in the south east in the light of alternative regional hypotheses it is thought that early miocene basin initiation is related to coeval southeastward thrusting of the mesozoic lycian nappes flexural loading is inferred to have resulted in block faulting of the foreland and this exploited pre existing lines of structural weakness dating from early mesozoic rifting mid miocene relative sea level rise may relate to global eustacy and or regional tectonic subsidence finally late miocene renewed coarse clastic input locally very coarse and basin infilling reflect tectonic uplift to the north possibly related to continuing africa eurasia convergence in the region

subsidence of askja caldera 2000 2009 modelling of deformation processes at an extensional plate boundary constrained by time series insar analysis abstract many calderas in the world show long term unrest in the form of elevated rates of deformation and seismicity related to pressure changes and magma movements within their magmatic plumbing systems we present new observations of the style of deformation at the askja caldera iceland since 2000 using interferometric analysis of synthetic aperture radar images insar acquired by the canadian radarsat 2 satellite when combined with previously acquired detailed geodetic observations by various techniques we obtain an overview of askja s behaviour through more than four decades the combined dataset reveals that during this non eruptive period askja continuously subsides at a rate of 2 5 3 cm yr in 2000 2009 somewhat lower than the 5 cm yr rate inferred for the 1983 1998 period this behaviour of askja is evaluated and compared to those of other restless calderas the wrapped interferograms show three main features 1 concentric fringes depicting subsidence in the centre of the main askja caldera 2 oval fringes elongated along the rift portraying subsidence and 3 subsidence in an area north of the vatnajokull glacier the average line of sight los velocity from ground to satellite was used as input for inverse modelling of a deflating pressure source beneath the caldera embedded in a homogeneous elastic half space two different source geometries were tested a point pressure source and a horizontal penny shaped crack the concentric fringes centred in the askja caldera are best fit by a point source located at 65 05 n 16 78 w at a depth of 3 2 3 8 km with a volume decrease of 0 0012 0 0017 km3 yr from 2000 to 2009 consistent with previous studies provisional 2d fem models including structural complexities in the crustal layers indicate that the tectonic setting of askja plays an important role in the continuous long term high subsidence rates observed there in order to fully understand the cause and effects of the complicated tectonic setting we encourage the use of a more realistic rheological model of the area which could lead to reinterpretation of previous model results

processes of late cretaceous to late miocene episodic thrust sheet translation in the lycian taurides sw turkey the lycian taurides of sw turkey consist of an allochthonous mesozoic passive margin succession that was episodically detached from its autochthon and translated southeastwards between latest cretaceous to late miocene times a combination of structural analysis sedimentology palaeontology and geochemistry allows subdivision of this orogenic event into 1 latest cretaceous trench passive margin collision causing ophiolite obduction and detachment of the koycegyiz thrust sheet 2 mid late eocene continent continent collision renewing southeastwards thrusting and causing detachment of the teke dere thrust sheet and yavus thrust sheets 3 miocene extensional collapse of the orogen with southeastwards translation of the allochthon coeval with rift basin formation in the hinterland

an anomalous radon decrease in groundwater prior to an m6 0 earthquake a possible precursor a significant decrease in the radon concentration of artesian groundwater was observed at a well established observation site in northeast japan about two days before an m 6 0 earthquake occurred about 200 km from the site on the basis of a concurrent in situ minus 126 m temperature drop of the groundwater the authors infer that precursory changes in regional stress were locally amplified near this site and resulted in the temporary mixing of cooler radon poor groundwater into the normal artesian flow

an insar based survey of volcanic deformation in the central andes we extend an earlier interferometric synthetic aperture radar insar survey covering about 900 remote volcanos of the central andes 14 27 s between the years 1992 and 2002 our survey reveals broad 10s of km roughly axisymmetric deformation at 4 volcanic centers two stratovolcanoes are inflating uturuncu bolivia and hualca hualca peru another source of inflation on the border between chile and argentina is not obviously associated with a volcanic edifice here called lazufre and a caldera cerro blanco also called robledo in northwest argentina is subsiding we explore the range of source depths and volumes allowed by our observations using spherical ellipsoidal and crack like source geometries we further examine the effects of local topography upon the deformation field and invert for a spherical point source in both elastic half space and layered space crustal models we use a global search algorithm with gradient search methods used to further constrain best fitting models inferred source depths are model dependent with differences in the assumed source geometry generating a larger range of accepted depths than variations in elastic structure source depths relative to sea level are 8 18 km at hualca hualca 12 25 km for uturuncu 5 13 km for lazufre and 5 10 km at cerro blanco deformation at all four volcanoes seems to be time dependent and only uturuncu and cerro blanco were deforming during the entire time period of observation inflation at hualca hualca stopped in 1997 perhaps related to a large eruption of nearby sabancaya volcano in may 1997 although there is no obvious relation between the rate of deformation and the eruptions of sabancaya we do not observe any deformation associated with eruptions of lascar chile at 16 other volcanoes that had recent small eruptions or fumarolic activity or associated with a short lived thermal anomaly at chiliques volcano we posit a hydrothermal system at cerro blanco to explain the rate of subsidence there for the last decade we calculate the ratio of the volume of magma intruded to extruded is between 1 10 and that the combined rate of intrusion and extrusion is within an order of magnitude of the inferred geologic rate

new mass increase beneath askja volcano iceland a precursor to renewed activity askja is an active central volcano located on the ns trending en echelon rift zone marking the mid atlantic plate boundary in north iceland between 2007 and 2009 we observed a gravity increase at the centre of the caldera this contrasts with net gravity decreases recorded between 1988 and 2007 interpreted previously in terms of magma drainage the recent gravity increase is rapid but similar in terms of lateral extent to the preceding decrease this gravity increase corresponds to a sub surface mass increase of 0 68 1011kg at about 3km depth it is possible that the new gravity increases observed at askja reflect accumulation of magma beneath the caldera and thus may herald a new phase in the activity of this volcano which last erupted in 1961

temporal development of the 1999 intrusive episode in the eyjafjallajokull volcano iceland derived from insar images eyjafjallajokull volcano located in southern iceland is characterized by its quiet nature only about a handful of earthquakes associated with the volcanic system had been detected prior to the 1990s earthquake swarms did however occur in 1994 and 1999 here we investigate the spatio temporal evolution of a magmatic intrusion associated with the 1999 earthquake swarm via analysis of produced surface deformation a series of interferometric synthetic aperture radar insar images spanning various periods of the intrusion show that in 1999 surface deformation occurred mainly on the southern flanks of the volcano the deformation amounts to more than 20 cm of range change inverse modeling resolves the deformation source to be a sill intrusion at 6 3 km depth sill opening was up to 1 m and the total intruded volume amounts to 0 03 km3 the insar data display a migration of the center of deformation through time enabling us to create time dependant sill opening models furthermore we investigate the spatio temporal distribution of earthquakes and find that the distribution supports the insar derived model and additionally provides indications for a possible site of a feeder channel magmatic flow rate estimates indicate an initial intrusion rate of 4 6 m3 s declining over a few weeks

on precisely modelling surface deformation due to interacting magma chambers and dykes combined data sets of insar and gps allow us to observe surface deformation in volcanic settings however at the vast majority of volcanoes a detailed 3 d structure that could guide the modelling of deformation sources is not available due to the lack of tomography studies for example therefore volcano ground deformation due to magma movement in the subsurface is commonly modelled using simple point mogi or dislocation okada sources embedded in a homogeneous isotropic and elastic half space when data sets are too complex to be explained by a single deformation source the magmatic system is often represented by a combination of these sources and their displacements fields are simply summed by doing so the assumption of homogeneity in the half space is violated and the resulting interaction between sources is neglected we have quantified the errors of such a simplification and investigated the limits in which the combination of analytical sources is justified we have calculated the vertical and horizontal displacements for analytical models with adjacent deformation sources and have tested them against the solutions of corresponding 3 d finite element models which account for the interaction between sources we have tested various double source configurations with either two spherical sources representing magma chambers or a magma chamber and an adjacent dyke modelled by a rectangular tensile dislocation or pressurized crack for a tensile okada source representing an opening dyke aligned or superposed to a mogi source magma chamber we find the discrepancies with the numerical models to be insignificant 5 per cent independently of the source separation however if amogi source is placed side by side to an okada source in the strike perpendicular direction we find the discrepancies to become significant for a source separation less than four times the radius of the magma chamber for horizontally or vertically aligned pressurized sources the discrepancies are up to 20 per cent which translates into surprisingly large errors when inverting deformation data for source parameters such as depth and volume change beyond 8 radii however we demonstrate that the summation of analytical sources represents adjacent magma chambers correctly

unrest at campi flegrei a contribution to the magmatic versus hydrothermal debate from inverse and finite element modeling 1 we present results from the modeling of ground deformation and microgravimetric data recorded at campi flegrei in order to assess the causative phenomena of caldera unrest between 1981 and 2001 we find that residual gravity changes during ground uplift 1982 1984 are indicative of mass changes in a hybrid of magmatic and hydrothermal sources during deflation between 1985 and 2001 the inversion of gravity residuals for a single source does not provide convincing results we then performed the joint inversion of gravity and deformation data for multiple spherical sources and refined source parameters by finite element modeling in order to mitigate against limitations of the analytical solutions the data recorded during inflation and rapid deflation may be best explained by mass and pressure changes in a deep magmatic source at about 5 km depth and a shallow 2 km deep hydrothermal source both sources contribute equally to the gravity changes observed between 1982 and 1984 the contemporary uplift appears to be mainly caused by the shallow source the subsequent deflation is dominated by a pressure decrease in the hydrothermal source the magmatic source contributes chiefly to the observed gravity changes pressure and density variations within multiple shallow seated hydrothermal sources provide acceptable fits to the deflation and accompanying gravity changes recorded since 1988 these shallow level dynamics also appear to trigger spatially and temporarily random short term reversals of the overall mode of ground subsidence since 1985 our analysis does not support the idea of magmatic contributions to these short lived periods of inflation

triggered fault slip on june 17 2000 on the reykjanes peninsula sw iceland captured by radar interferometry 1 dynamically triggered seismicity followed shortly after a ms 6 6 earthquake in iceland on june 17 2000 smaller earthquakes occurred on the reykjanes peninsula up to 100 km from the mainshock rupture using interferometric analysis of synthetic aperture radar images insar we measure crustal deformation associated with three triggered deformation events the largest of these occurred at lake kleifarvatn 85 km west of the mainshock epicenter modeling of the insar data reveals strikeslip on a north striking fault with a geodetic moment of 6 2 1017 nm equivalent to magnitude mw 5 8 earthquake a seismological estimate of the moment is not yet available because the seismic signature of this event is partly hidden by the mainshock waveform the paucity of aftershocks on the triggered rupture plane suggests some aseismic slip there compatible with a thin seismogenic crust high heat flow hydrothermal alteration and the presence of fluids in the area

building icelandic igneous crust by repeated melt injections observations of microseismicity provide a powerful tool for mapping the movement of melt in the crust here we record remarkable sequences of earthquakes 20 km below the surface in the normally ductile crust in the vicinity of askja volcano in northeast iceland the earthquakes occur in swarms consisting of identical waveforms repeating as frequently as every 8 s for up to 3 h we use template waveforms from each swarm to detect and locate earthquakes with an automated cross correlation technique events are located in the lower crust and are inferred to be the result of melt being injected into the crust during melt intrusion high strain rates are produced in conjunction with high pore fluid pressures from the melt or exsolved carbon dioxide these cause brittle failure on high angle fault planes located at the tips of sills moment tensor solutions show that most of the earthquakes are opening cracks accompanied by volumetric increases this is consistent with the failure causing the earthquakes by melt injection opening new tensile cracks analysis of the magnitude distribution of earthquakes within a swarm reveals a complicated relationship between the imposed strain rates and the fluids that cause brittle failure the magnitude of the earthquakes is controlled by the distance fluids can migrate along a fault whereas the frequency of the events is controlled by the strain rate faults at the tips of sills act to focus melt transport between sills and so must be an important method of transporting melt through the lower crust

facies and palaeogeographic evidence for the miocene evolution of the isparta angle in its regional eastern mediterranean context abstract we summarise facies evidence for four miocene basins lycian aksu kopru and manavgat within the isparta angle facies patterns are plotted on six palaegeographic maps restored to their pre late miocene setting these maps are used to help infer the various controls on deposition facies trends and structural features suggest that the individual basins were kinematically linked within the overall african eurasia convergence zone the miocene basins represent a classic example of how related basins may develop within an evolving orogen subject to variable controls through time the dominant control was tectonic although autocyclic sedimentary processes e g reef growth and both relative and eustatic sea level change played a significant role from the palaeogeographic reconstructions and the tectonic context of the isparta angle we infer that during the early miocene the westerly lycian basin and the neighbouring aksu basin experienced flexural subsidence related to southeastward thrusting of the lycian nappes more distal effects of the forebulge may have caused uplift around the aksu and kopru basins initiating n s half grabens bounded by master faults on the eastern side of each basin later the eastern basins of the isparta angle were influenced by regional northward subduction and inferred slab retreat within a remnant of the southern neotethys located within the mediterranean sea at the intersection of the south aegean and cyprus arcs

fault block rotations at the edge of a zone of continental extension southwest turkey the ne sw trending burdur acigol and baklan basins of southwest turkey are bounded by normal faults which became active in quaternary times prior to this a more widely spaced system of pliocene basins had existed each of the quaternary basins has a half graben geometry with a major nw dipping fault on its southeast side previous studies of the 1971 burdur earthquake caused by movement on the fault bounding the burdur basin have shown this fault to flatten slightly at depth deformation in the hangingwall of the fault controlling the pliocene basin in the burdur region suggests a planar fault geometry it is suggested that the pliocene fault rotated to its present shallow orientation then became inactive and acted as a detachment at depth for the more recent quaternary fault quaternary faults bounding the burdur acigol and baklan basins have a sinistral strike slip component with slip vectors indicating extension in an nw se direction this is at variance with regional n s extension in western turkey a solution for this contrast is found by invoking block rotations about vertical axes in a deforming zone between the rapidly extending aegean region to the west and the stable unstretched anatolian plateau to the east

annealing kinetics of fission tracks in zircon an experimental study a series of laboratory annealing experiments on zircon fission tracks has been carried out under heating conditions of 350 750 c for 10 1 103 hr i e 4 5 min 40 days variation in the confined lengths of spontaneous fission tracks was determined using zircon grains from nisatai dacite the fading contours of normalized mean track length r on the arrhenius diagram showed as sets of straight lines we performed a series of model fittings called the parallel and fanning models in order to describe the decrease in r with increasing temperature or heating time the lowest temperature limit of the zircon partial annealing zone zpaz was defined as r 0 95 and the highest as r 0 4 which approximately corresponded to the total fading of surface tracks extrapolation of the results of the laboratory experiments to the geological timescale gives for a heating duration of 106 yr estimated values of the zpaz of 210 320 c 60 c 2 with the parallel model 190 350 c 50 c 2 with the fanning model critical temperature t0 and 170 390 c 50 c 2 with the fanning model t0 the temperatures of the zpaz decrease by 20 c for an annealing duration that is an order of magnitude longer because the estimated closure temperature of zircon fission track analysis approximately corresponds to the middle of the zpaz these results support the previously estimated closure temperature of 240 c by varying the etching time it was revealed that significant removal of radiation damage occurs at r 0 93

the sedimentology and development of terravecchia formation carbonates upper miocene of north central sicily possible eustatic influence on facies development abstract on at least two occasions during the late tortonian siliciclastic deposition ceased and carbonates accumulated at the northern margin of the caltanissetta basin in north central sicily bioclastics dominated in the shallower proximal areas while coral reef facies developed where shallow water sand and cobble substrates existed or where sea floor highs has created local shallows the genetic model proposed is that siliciclastic deposition was repeatedly terminated during the late tortonian by rises in sea level which transgressed fluviatile and deltaic environments carbonate deposition was widespread but later erosion and reworking removed much of the sediments except within abandoned delta distributary channels and minor sea floor depressions reef developments associated with channel mouths and the shelf slope break have been preserved in situ whereas channels in more proximal locations are filled with siliciclastic bioclastic and intraclastic rubble from elsewhere on the delta top the wide lateral extent of the truncated tops of the carbonate beds argues for eustatic rather than tectonic controls of erosion and subsequent reworking these events may be closely related in time to other recorded late tortonian eustatic events in the foreland zones such as the hyblean plateau and the maltese islands further south collectively they give some support to a model involving multiple eustatic fluctuations associated with the onset of the messinian desiccation of the mediterranean

intrusion triggering of the 2010 eyjafjallajokull explosive eruption the ash cloud that brought chaos to european air traffic in april this year was the result of emissions from an icelandic volcano that had been intermittently active for about 18 years a combination of detailed space based geodetic measurements and seismic monitoring of the eyjafjallajkull volcano in the run up to the ash producing explosive summit eruption reveals an unusual deformation pattern that may be attributed to its off rift setting with relatively cool subsurface structure and limited magma at shallow depth as to the predictability of such a dramatic reawakening the immediate precursors to the initial eruption of the volcano in 2010 were subtle and difficult to detect but the clear signs of volcanic unrest during the weeks months and years preceding it may provide better clues to the catastrophic explosion

increased capture of magma in the crust promoted by ice cap retreat in iceland retreating ice caps overlying volcanoes are thought to relieve surface pressure causing enhanced magma generation and volcanic activity analysis of crustal stress during a dyke intrusion event associated with retreat of iceland s largest ice cap indicates that ice retreat could instead promote storage of magma in the crust rather than eruption at the surface

plate boundary deformation and continuing deflation of the askja volcano north iceland determined with gps 1987 1993 gps geodetic measurements were conducted around the askja central volcano located at the divergent plate boundary in north iceland in 1987 1990 1992 and 1993 the accuracy of the 1987 and 1990 measurements is in the range of 10 mm for horizontal components the accuracy of the 1992 and 1993 measurements is about 4 mm in the horizontal plane regional deformation in the askja region is dominated by extension points located outside a 30 45 km wide plate boundary deformation zone indicate a displacement of 2 4 0 5 cm a in the direction n 99 e 12 of the eurasian plate relative to the north american plate in the period 1987 1990 within the plate boundary deformation zone extensional strain accumulates at a rate of 0 8 strain a displacement of control points next to askja 7 km from the caldera center in the periods 1990 1993 and 1992 1993 show deflation and contraction towards the caldera these results are in accordance with the results obtained by other geodetic methods in the area which indicate that the deflation at askja occurs in response to a pressure decrease at about 2 8 km depth located close to the center of the main askja caldera a mogi point source was fixed at this location and the gps data used to solve for the source strength a central subsidence of 11 2 5 cm in the period 1990 1993 is indicated and 5 5 1 5 cm in the period 1992 1993 the maximum tensional strain rate according to the point source model occurs at a horizontal distance of 2 5 6 km from the source at the same location as the main caldera boundary discrepancies between the observed displacements and predicted displacements from the mogi model near the askja caldera can be attributed to the regional eastwest extension that occurs at askja

kinematic evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we present an updated series of kinematic reconstructions of the major plates around the tethys from the atlantic ocean to the pamirs between the early jurassic and the present this set is used elsewhere as a basis for paleogeographic maps of the entire region the problems related to the positions of the continents in the lower triassic are also discussed no direct analyses of magnetic anomalies and fracture zones in the atlantic have been made rather all available poles and rotations have been tested in order to eliminate or minimize possible kinematic errors the reconstructions are shown for nine key geological periods which correspond to well recognized magnetic anomalies except for the jurassic cretaceous boundary and the cretaceous tertiary boundary which correspond to interpolated positions paleolatitudes have been drawn using the study of westphal et al 1986 an attempt has been made to take into account the displacements caused by formation of the continental margins and basins by stretching the resulting relative vector of motions along the northern boundary of the tethys shows a significant change 80 m y ago left lateral motion with compression dominates before whereas right lateral motion with compression dominates after to the east rates of motion vary by a factor of three with time and four maxima can be clearly related to tectonic events in the late jurassic late cretaceous eocene and post middle miocene to the west north of apulia on the contrary the motion rate has not changed significantly since the early cretaceous and is close to 1 cm yr as an average these rather complex adjustments in rates and directions of relative motion are produced in great part through a complex migration of the africa eurasia pole of rotation and seem to be mostly governed by the tectonics of the tethys plate boundary

radon emanation coefficients of several minerals how they vary with physical and mineralogical properties the escape rates of radon gas from rocks and minerals are of great relevance to many branches of geosciences and it is thus important to understand the physical and mineralogical properties that control radon emanation rates mechanisms of radon loss from minerals have direct bearing on the reliability of u pb and u th he geochronology fourteen minerals from three different mineral groups and with localities spanning three continents were selected for this study the radon emanation coefficients rec for each mineral were measured as a function of grain size temperature 238 u and 232 th activities total absorbed dose density and mineral melting temperature the measured 238 u and 232 th activities ranged from 0 01 to 6487 bq g and from below detection limit to 776 bq g respectively the rec values for unheated pulverized samples ranged from 0 083 to 7 0 which is comparable to previously reported ranges except for zircon an inverse correlation between grain size and rec was observed full annealing of fission tracks resulted in an overall decrease in rec values suggesting that nuclear tracks could possibly act as conduits for radon release while activity dose density and melting temperatures are not strongly correlated with rec values it was observed that minerals with high melting points 1400 c have lower rec values most likely due to inhibition of radon release by compact crystal lattice structures this is the first attempt to our knowledge to correlate rec values with melting temperature and this study reports six minerals for which no rec values have been previously reported

interaction between central volcanoes and regional tectonics along divergent plate boundaries askja iceland activity within magmatic divergent plate boundaries mdpb focuses along both regional fissure swarms and central volcanoes an ideal place to investigate their mutual relationship is the askja central volcano in iceland askja consists of three nested calderas namely kollur askja and oskjuvatn located within a hyaloclastite massif along the nne ssw trending icelandic mdpb we performed an extensive field based structural analysis supported by a remote sensing study of tectonic and volcanic features of askja s calderas and of the eastern flank of the hyaloclastite massif in the massif volcano tectonic structures trend n 10 e to n 40 e but they vary around the askja caldera being both parallel to the caldera rim and cross cutting on the western side structural trends around the oskjuvatn caldera are typically rim parallel volcanic vents and dikes are preferentially distributed along the caldera ring faults however they follow the nne ssw regional structures when located outside the calderas our results highlight that the askja volcano displays a balanced amount of regional fissure swarm related and local shallow magma chamber related tectonic structures along with a mutual interaction among these this is different from krafla volcano to the north of askja dominated by regional structures and grimsvotn to the south dominated by local structures therefore askja represents an intermediate tectono magmatic setting for volcanoes located in a slow divergent plate boundary this is also likely in accordance with a northward increase in the spreading rate along the icelandic mdpb

chromite from the blue ridge province of north carolina accessory chromite in dunite shows a variety of textures that indicate alteration one group type a consists of four types of chromite clean chromite lattice chromite in which the invading chlorite occurs along three directions in the 100 plane optically zoned chromite and poikiloblastic chromite most of type a chromites are surrounded by chromian clinochlore the other group type b consists of euhedral to subhedral chromite grains which are included in olivine or pyroxene the accessory chromites define a trend exhibited by chromite from other areas that have undergone metamorphism olivine spinel geothermometry indicates equilibration temperatures near 700 degrees c roughly consistent with mineral assemblages in the host gneisses thus the blue ridge dunites are metamorphic rocks and not primary mantle peridotites modified journal abstract

multiple volcano deformation sources in a post rifting period 1989 2005 behaviour of krafla iceland constrained by levelling tilt and gps observations abstract the krafla rifting episode which occurred in north iceland in 1975 1984 was followed by inflation of a shallow magma chamber until 1989 at that time gradual subsidence began above the magma chamber and has continued to the present at a declining rate pressure decrease in a shallow magma chamber is not the only source of deformation at krafla as other deformation processes are driven by exploitation of two geothermal fields together with plate spreading in addition deep seated magma accumulation appears to take place with its centre 10 km north of the krafla caldera the relative strength of these sources has varied with time new results from a levelling survey and gps measurements in 2005 allow an updated view on the deformation field deformation rates spanning 2000 2005 are the lowest recorded in the 30 year history of geodetic studies at the volcano the inferred rate of 2000 2005 subsidence related to processes in the shallow magma chamber is less than 0 3 cm yr whereas it was 5 cm yr in 1989 1992 currently the highest rate of subsidence takes place in the leirbotnar area within the krafla caldera and appears to be a result of geothermal exploitation

seismotectonics of the aegean region abstract fault plane solutions neotectonic field observations and in situ stress measurements have been used to determine the stress field associated with the active deformation of the lithosphere in the aegean and surrounding regions a stress gradient and a zonal pattern of different tectonism away from the trench axis has been postulated pure thrust faulting occurs in the fore arc side while the back arc side is mainly dominated by almost n s extensional tectonics a narrow belt of strike slip faults with predominantly thrust component separates these tectonic zones this belt seems to represent a transition from the thrust type faults to normal faults fault plane solutions of the whole region in question indicate that both the large and small magnitude shocks are caused by the same regional stress field a body of 33 focal mechanisms indicates that the intermediate depth shocks along the sinking mediterranean slab are associated with thrust type fracturing orientation of kinematic axes favours the suggestion that shear zones within the descending slab cause these shocks the active crustal shortening along the hellenic consuming boundary and the sinking of the mediterranean lithosphere beneath the south aegean area explain satisfactorily the seismotectonic features of the fore arc and the southern back arc sides on the contrary geophysical evidence concerning the cenozoic geodynamic evolution of the aegean is needed to interpret features of the north back arc area

association of subsurface radon changes in alaska and the northeastern united states with earthquakes abstract changes of radon concentration in the ground have been reported to correlate with seismic activity in many places over widely varying distances from the earthquake epicenters sometimes over 100 s and occasionally over 1000 s of km depending on the magnitude m of the earthquakes for proper use of such correlations in forecasting the location and size of impending earthquakes it would be useful to establish a relation between m and the maximum distance x m at which radon can be significantly altered by preseismic effects we have monitored radon in the ground continuously at blue mountain lake ny starting dec 3 1975 and at three locations in alaska icy bay yakataga and sand point starting nov 12 1979 march 5 1980 and june 29 1980 respectively sample correlations from visual examination of the recent radon record and tentative use of a proposed scaling relation show a number of possible earthquake related signals at these locations the data are compatible with scaling relations that were derived from two separate models of premonitory elastic strains in this work x m 10 0 48 m where x m is in units of km and m 3 since tilt and strain signals correlate similarly with magnitude and distance it is likely that most earthquake related radon signals are mechanically induced

u pb geochronology of the grenville orogen of ontario and new york constraints on ancient crustal tectonics based on lithological structural and geophysi cal characteristics the proterozoic grenville orogen of southern ontario and new york has been divided into domains that are separated from each other by ductile shear zones in order to constrain the timing of meta morphism u pb ages were determined on metamorphic and igneous sphenes from marbles calc silicate gneisses amphibolites granitoids skarns and pegmatites in addi tion u pb ages were obtained for monazites from meta pelites and for a rutile from an amphibolite these mineral ages constrain the timing of mineral growth the duration of metamorphism and the cooling history of the different domains that make up the southern part of the exposed grenville orogen based on the ages from metamorphic minerals regional and contact metamorphism occurred in the following intervals central granulite terrane