gas evolution in eruptive conduits combining insights from high temperature and pressure decompression experiments with steady state flow modeling abstract in this paper we examine the consequences of bubble nucleation mechanism on eruptive degassing of rhyolite magma we use the results of published high temperature and pressure decompression experiments as input to a modified version of conflow the numerical model of mastin and ghiorso 2000 u s g s open file rep 00 209 53 pp and mastin 2002 geochem geophys geosyst 3 10 1029 2001gc000192 for steady two phase flow in vertical conduits synthesis of the available experimental data shows that heterogeneous nucleation is triggered at p 120 150 mpa and leads to disequilibrium degassing at extreme h2o supersaturation in this latter case nucleation is an ongoing process controlled by changing supersaturation conditions exponential bubble size distributions are often produced with number densities of 106 109 bubbles cm3 our numerical analysis adopts an end member approach that specifically compares equilibrium degassing with delayed disequilibrium degassing characteristic of homogeneously nucleating systems the disequilibrium simulations show that delaying nucleation until p 150 mpa restricts degassing to within 1500 m of the surface fragmentation occurs at similar porosity in both the disequilibrium and equilibrium modes 80 vol but at the distinct depths of 500 m and 2300 m respectively the vesiculation delay leads to higher pressures at equivalent depths in the conduit and the mass flux and exit pressure are each higher by a factor of 2 0 residual water contents in the melt reaching the vent are between 0 5 and 1 0 wt roughly twice that of the equilibrium model

messinian crisis what happened around the northeastern aegean abstract the effects of the severing of the atlantic mediterranean connection during the 400 000 year messinian event are also observed around the northern aegean during this time a sea of brackish water character developed between paratethys in the north and the mediterranean in the south this sea is named here egemar this basin was principally fed by surrounding rivers and by paratethyan waters that entered egemar via a connection through the sea of marmara which was then a bay of the paratethys the sedimentary sequence deposited in egemar is principally composed of limestones containing brackish water fauna paratethyan however there are some intercalations containing mediterranean species five intercalations of mediterranean character are found within the sedimentary sequence of egemar indicating the re establishment of an atlantic mediterranean connection from time to time and thus replenishment of marine waters the turolian is represented by continental clastics which interdigitate with the brackish water cycles implying a number of regressions egemar eventually became part of the eastern mediterranean due to a major transgression during the early pliocene

conduit convection driving persistent degassing at basaltic volcanoes abstract the persistent release of gas at basaltic volcanoes where there is a low magma eruption rate can be driven by an exchange flow of magma in the conduit in which gas rich magma ascends degasses and crystallises and then sinks back down the conduit the driving force of the flow is provided by the density difference between the buoyant bubble rich magma at depth and the dense degassed crystallised magma at shallow levels in this study we attempt to constrain the physical and chemical processes driving an exchange flow of magma at stromboli aeolian archipelago italy the model uses a simple cylindrical geometry we define degassing and crystallisation paths of the ascending and descending magmas constrained by gas flux and melt inclusion data given in the literature to produce a three phase model of ascending and descending magmas driving persistent gas fluxes we calculate the viscosity of the three phase magma using end member rheological models for bubble and crystal suspensions combining our modelled magma properties with analogue exchange flow experiments we can relate the regime of magma flow driving persistent degassing to pressure at pressures 90 mpa 3 km the viscosity ratio is 100 and the regime is predicted to be side by side flow with both ascending and descending magmas adjacent to a portion of the conduit wall at pressures 90 mpa 3 km the viscosity ratio between the ascending and descending magma is 100 and the flow is predicted to be core annular flow with the ascending vesiculating magma in the inner core and the more crystalline degassed magma flowing down along the conduit wall by analogy we hypothesise that degassed magma would flow down along the walls in dike like plumbing geometries that have been proposed for the deeper strombolian system analogue experiments suggest that exchange flows do not overturn under conditions of maximum volume flux we use an empirical relationship to characterise the volume flux of the exchange flow and show that the radius of a cylindrical conduit required to account for the observed persistent gas flux at stromboli at 0 1 mpa is 1 m

modelling the rapid near surface expansion of gas slugs in low viscosity magmas the ascent of large gas bubbles slugs in vertical cylindrical conduits and low viscosity magmas is simulated using 1d mathematical and 3d computational fluid dynamic cfd models following laboratory evidence the 1d model defines a constant rise velocity for the slug base and allows gas expansion to accelerate the slug nose through the overlying fluid during ascent the evolution of rapidly expanding gas slugs observed in laboratory experiments is reproduced well and at volcano scales predicts at surface overpressures of several atmospheres without requiring any initial overpressure at depth the near surface dynamics increase slug nose velocities through the overlying magma by a factor of c 2 5 and the gas expansion results in pre burst magma surface velocities of c 35m s21 to examine pressure distributions and the forces exerted on a conduit 3d cfd simulations were carried out at volcano scales the vertical single forces during final slug ascent to the surface are c 106 n two orders of magnitude smaller than those associated with verylong period seismic events at stromboli this supports a previous interpretation of these events in which they are generated by gas slugs flowing through changes in conduit geometry rather than being the direct result of slug eruption processes

the 1 october 1995 dinar earthquake sw turkey the dinar earthquake ms 6 1 usgs pde of 1 october 1995 occurred on the nwse trending dinar fault the earthquake is associated with a 10 km long surface rupture with predominantly normal faulting the mainshock was preceded by a series of foreshocks that started 6 days before the mainshock and included two md 4 5 events the mainshock source mechanism derived from the inversion of broad band p waves revealed that two sub events occurred on a nw se trending normal fault with a small strike slip component according to the source model estimated in this study the first rupture started at a depth of about 8 km and reached to a depth of about 12 km propagating north west the total seismic moment found from the inversion of p waveforms is 2 0 times 10 18 nm the seismic moment of the second sub event was about four times larger than the first one field observations gps measurements and slip vector obtained from the inversion of broad band p waveforms suggest that the nw se trending dinar fault is due to the internal deformation of sw anatolia moving south westwards

evolution of melt vapor surface tension in silicic volcanic systems experiments with hydrous melts 1 we evaluate the melt vapor surface tension of natural water saturated dacite melt at 200 mpa 950 1055 c and 4 8 5 7 wt h2o we experimentally determine the critical supersaturation pressure for bubble nucleation as a function of dissolved water and then solve for at those conditions using classical nucleation theory the solutions obtained give dacite melt vapor surface tensions that vary inversely with dissolved water from 0 042 0 003 j m 2 at 5 7 wt h2o to 0 060 0 007 j m 2 at 5 2 wt h2o to 0 073 0 003 j m 2 at 4 8 wt h2o combining our dacite results with data from published hydrous haplogranite and high silica rhyolite experiments reveals that melt vapor surface tension also varies inversely with the concentration of mafic melt components e g cao feototal mgo we develop a thermodynamic context for these observations in which melt vapor surface tension is represented by a balance of work terms controlled by melt structure overall our results suggest that cooling crystallization and vapor exsolution cause systematic changes in that should be considered in dynamic modeling of magmatic processes

flow to fracture transition in a volcanic mush plug may govern normal eruptions at stromboli stromboli is a model volcano for studying eruptions driven by degassing the current paradigm posits that strombolian eruptions represent the bursting of gas slugs ascending through melt filled conduits but petrological observations show that magma at shallow depth is crystalline enough to form a three phase plug consisting of crystals bubbles and melt we combine a 1d model of gas flushing a crystalline mush with a 3d stress model our results suggest that localized gas segregation establishes hot conduits of mobile magma within a stagnant plug the plug is prone to tensile failure controlled by gas over pressure and tectonic stress with failure most likely beneath the observed vent locations we hence argue that strombolian eruptions are related to plug failure rather than flow our proposed three phase model of the shallow plumbing system may provide a promising framework for integrating geophysical petrological and morphological observations at stromboli and in open system volcanism more generally

plio quaternary stress state in the burdur basin sw turkey abstract this study defines the plio quaternary to present day stress regime in the burdur basin located at the northeastern end of the fethiye burdur fault zone in sw turkey this fault length which is considered the landward continuation of the pliny strabo trench is an important feature in sw turkey the inversion slip vectors measured on fault planes indicate a consistent normal faulting stress regime during plio quaternary time continuing into recent times as indicated by earthquake focal mechanism inversions both states have consistent nw se trending horizontal minimum stress axes 3 the orientation of fault sets is predominantly around the ne sw direction in the major fethiye burdur fault zone making the extension nw se the mean stress ratio is 0 74 indicating a triaxial stress state which is clearly different from radial extension the nw se extension is probably responsible for the formation of the burdur basin during plio quaternary time this extension which is probably caused by slab pull force due to the subduction process along the cyprus arc produces a dominant normal motion along the fbfz

structural architecture of the rhodes basin a deep depocentre that evolved since the pliocene at the junction of hellenic and cyprus arcs eastern mediterranean abstract interpretation of 1500 km of multi channel seismic reflection profiles shows that the rhodes basin evolved in two distinct tectonic stages a protracted miocene convergence episode p1 resulted in the development of a mainly sse verging fold thrust belt this period corresponds with the emplacement of the lycian nappes to the northeast and fold thrust complexes on the island of rhodes to the west this phase of deformation ceased in the late miocene the absence of evaporites in the rhodes basin suggests that this region must have remained above the depositional base of marine evaporite environment during the messinian the morphology of the m reflector and the architecture of the lowermost pliocene growth strata in the central portion of the rhodes basin demonstrate the existence of rugged paleo relief over the pre existing miocene fold thrust belt in early pliocene the middle pliocene quaternary phase of deformation is characterised by ne sw sinistral transpression p2 and rapid regional subsidence the p2 deformation occurred in response to an actively curving hellenic arc and the increasing obliquity of its eastern limb the pliny strabo trenches or fault zones to the convergence vector of the african plate during this time the p1 structures became re activated as transpressional faults further facilitating the rapid subsidence we envisage the evolution of the rhodes basin as the result of subsidence associated with loading of the large imbricate thrust panels that carry the western tauride mountains in the north at present the pliny strabo fault zones are delineated as a ne sw trending 30 50 km wide zone that continue into the western segment of the rhodes basin this fault zone is further correlated with the similar trending 50 km wide burdur fethiye fault zone in southwestern turkey

the generation of gas overpressure in volcanic eruptions abstract observations of natural eruption products show that different parts of a single magma batch may experience different degassing histories during ascent in a volcanic conduit in non explosive eruptions lava issuing from a volcanic vent may contain overpressured gas bubbles these important features of volcanic eruptions cannot be accounted for by existing flow models which rely on simplifying hypotheses for the relationship between pressures in the gas phase and in the bulk flow volcanic flows involve highly compressible material which undergoes large viscosity variations as degassing proceeds we show that these properties may lead to large gas overpressures in erupting lava the magnitude of this overpressure depends on the initial volatile content of magma and is largest for relatively volatile poor magmas due to the extreme viscosity variations at water contents less than 1 wt we develop a simple analytical model to illustrate the main features of compressible viscous flows 1 at any level gas pressure is larger near the conduit axis than at the walls 2 gas overpressure is an increasing function of mass discharge rate

pressure solution and viscous compaction in sedimentary basins mathematical models of compaction in sedimentary basins typically assume a relationship between effective pressure pand porosity which is of a non linear type that is p p d however at depths greater than a kilometer pressure solution becomes important and this relationship approaches a viscous one we derive a mathematical model for viscous compaction in sedimentary basins and show how the model suggests different styles of behavior in the limits of slow nd fst compaction the initial pore pressure will be lithostatic over time the sediments compact and the resultant expulsion of pore water allows the pore pressure to approach a hy drostatic limit and in so doing the porosity is reduced at depths up to about a kilometer this compaction is elastic and due to the rearrangement of sediment particles at greater depths cementation and pressure solution occur and the latter causes further compac tion we call compaction by pressure solution viscous compaction and it forms the subject of the present pa per one of the interesting features of overpressuring is that it typically occurs suddenly at depths in excess of 3000 meters hunt 1990 and is often associated

stability and instability of quiescently active volcanoes the case of masaya nicaragua quiescently active volcanoes are enigmatic due to their restlessness but lack of eruptive activity i present a model of coupled conduit convection and foam accumulation to explain degassing behavior of masaya an active volcano in nicaragua that is currently emitting large amounts of gas but not erupting gas rich magma is transported through a conduit 2 6 m in radius and then released into a shallow reservoir the magma is degassed in the reservoir and forms a foam 1 3 m thick at the top with bubbles 20 60 m in diameter the foam layer is stable because the input of gas into the foam is balanced by gas release through a vent to the surface if the foam layer is destabilized the volcano can erupt explosively the most likely cause of foam destabilization is a large injection of volatile rich magma from deeper levels into the shallow conduit reservoir system thereby increasing magma fluxes and gas fluxes exsolving large gas bubbles and reducing surface tension of the magma

multiple rifting pulses and sedimentation pattern in the cameli basin southwestern anatolia turkey abstract the neotectonic development of western anatolia was characterized by the formation of numerous graben type basins which have been well documented by general mapping although the cause and timing of the neogene regional tectonic extension remain controversial previous interpretations of the origin and evolution of these neogene basins were based mainly on regional scale tectonic inferences rather than detailed basin fill analysis the present study of the terrestrial intramontane cameli basin in the western taurides combines detailed facies analysis with biostratigraphic dating mammalian and molluscan fossils and documents three pulses of crustal extension that are reflected in changes in the palaeogeography and sedimentary architecture of the basin development of the cameli graben commenced in the vallesian time early tortonian and is marked by alluvial fan fluvial and lacustrine depositional systems with freshwater molluscan fauna a second pulse of tectonic extension occurred in the late ruscinian time early middle pliocene producing a new normal fault that split the basin longitudinally into two compartments the lake environment expanded and deepened coastal peat forming mires developed and abundant mammal fauna appeared by the early villanian time middle pliocene with the lacustrine deposits onlapping the basin margin and intrabasinal fault escarpments the lacustrine environment subsequently shrank as the progradation of axial river deltas and basin margin fan deltas caused water shallowing and shoreline regression a third pulse of extension occurred at the end of villanian time late pliocene when the development of a new generation of normal faults further split the basin into still narrower half graben compartments the third pulse of rifting is estimated to have accounted for little more than 10 of the sub basinal crustal extension but caused the most striking changes in the basin palaeogeography and drainage pattern the inward development of the successive normal faults indicated a high rate crustal extension this is the first regional case study of a terrestrial neotectonic graben employing detailed sedimentary facies analysis and mammal biostratigraphy and providing a time stratigraphic framework for the rifting pulses in western anatolia

volatile transport in a convecting magma column implications for porphyry mo mineralization we propose that convection in a column of silicic magma allows transport of volatile components from large 50 km3 magma chambers to the sites of shallow 3 km porphyry type mo deposits using constraints from the henderson and pine grove systems we show that even at temperatures as low as 700 c a granitic magma with 30 vol phenocrysts can flow through a magma column with a 150 m radius at a rate 10 km3 yr enough magma to contribute the mo necessary to form an ore deposit in a geologically reasonable time frame this process requires an efficient mechanism for bubble separation at the top of the magma column to produce degassed magma that can descend down through the column it also requires slow rates of crystallization in the silicic magma consistent with experimental studies hydrothermal fluids released from the convecting magma column can explain many geologic features of the deposits

the fethiye burdur fault zone a component of upper plate extension of the subduction transform edge propagator fault linking hellenic and cyprus arcs eastern mediterranean abstract the hellenic and cyprus arcs that mark the convergent boundary of the african and aegean anatolian plates are offset along a subduction transform edge propagator step fault running ne sw along the pliny and strabo trenches the continuation of the fault to the northeast through the rhodes basin and into sw anatolia is assessed seismic reflection profiles show that the structural architecture of the northern sector of the rhodes basin includes a large crustal scale fold thrust belt which is overprinted by numerous faults with small extensional stratigraphic separations a protracted episode of convergence in the miocene resulted in the development of a prominent ne sw striking and nw verging fold thrust belt in the rhodes basin the absence of evaporites in the rhodes basin and several seaward prograded vertically stacked quaternary delta successions resting at 2500 3500 m water depth collectively suggest that the rhodes basin must have remained above the depositional base of marine evaporite environment during the messinian and that the region must have subsided very rapidly during the pliocene quaternary during the pliocene quaternary a ne sw trending belt developed across the rhodes basin while the structural framework of this belt was characterised by reactivated thrusts in the central portion of the basin a prominent zone of ne sw striking and nw and se dipping faults with extensional separations developed in the northern portion of the basin two seismic profiles running parallel to the present day coastline provide the much needed linkage between the fethiye burdur fault zone onland and the reactivated thrusts in central rhodes basin and show that the pliocene quaternary zone of high angle faults with extensional separations clearly link with the similarly trending and dipping strike slip faults onland in the esen valley thus providing the continuity between the pliny strabo trenches in the southwest and the fethiye burdur fault zone in the northeast mapping of many faults in parts of the fethiye burdur fault zone shows evidence for sinistral strike slip but total displacement across the fault zone is at maximum a few tens of kilometres the step fault thus appears to have diminishing displacement associated with it as it propagates upwards into the upper plate from its originating tear in the subducting plate

a heat pipe model for vertical magma filled conduits abstract a 5 m radius magma filled conduit will solidify in much less than one year if heat losses to the conduit wall are not offset by some form of forced or free convection of magma from some source body through the conduit if the forced convection of magma from a source through the conduit is either too weak or is prevented by closure of the conduit at the end nearest the surface only free convective circulations between the source chamber and conduit are available to balance the wall heat loss using an integral approach the efficiency of free convection is investigated for conduits emplaced in both conductive and hydrothermally convective host rock environments the results of the model strongly suggest that free circulations within conduits of large aspect ratio provide an efficient mechanism for offsetting heat losses to the conduit wall the model provides a possible explanation for the occurrence of periodic eruptions from a conduit when the periodicity greatly exceeds the time scale for the cooling of a quiescent conduit by heat loss through the wall

conduit convection magma mixing and melt inclusion trends at persistently degassing volcanoes abstract magmas progressively exsolve volatiles as they ascend towards the earth s surface such that their volatile content is a function of pressure water and carbon dioxide concentrations measured in melt inclusions from degassing volcanoes rarely coincide with modelled degassing trends i show that observed melt inclusion trends can be reproduced through mixing of magmas either during convection within the volcanic conduit or within a subterranean magma reservoir no fluxing gas phase or post entrapment loss of water need be invoked a permeable network allowing gas transport is still required to avoid fragmentation of magma at shallow depths

stability of lava lakes a physical model of a generic lava lake system is developed we derive the requisite conditions for the existence of an equilibrium lava lake in which magmastatic pressure at the base of the conduit balances the pressure in the underlying magmatic reservoir the stability of this lava lake system is tested by investigating the response of the system to perturbation we develop a graphical method based on the system s pressure depth profile to predict the subsequent behaviour of the system despite the simplicity of the modelled system we find a broad behavioural spectrum initially the rise of bubbles through the magma is ignored in this case both stable long lived lava lakes and unstable lakes that are prone to sudden draining are predicted the stability of the system is shown to be controlled by lake conduit geometry the solubility and gas expansion laws and the magma s volatile content we show that an unstable lake must collapse to a new stable equilibrium subsequent recharge of the system by for example conduit overturn would promote a return to the original equilibrium giving rise to cyclic behaviour such a mechanism is consistent with lava lake behaviour during the 1983 1984 pu u o o eruption of kilauea when the rise of bubbles through the magma is considered our model predicts that stable lakes must drain over time we therefore deduce that persistently degassing stable lava lakes such as those observed at mt erebus antarctica and mauna ulu kilauea hawaii must have an effective conduit convection mechanism or an exogenous supply of bubbles from depth

bi directional flows in constrained systems we consider the exchange flow of relatively dense viscous fluid in a container connected by a vertical pipe to a container beneath it initially full of relatively light fluid a non dimensional value for the flux of dense fluid down the tube is determined experimentally as a function of the ratio of the two viscosities and the reynolds number the experimental data are satisfactorily collapsed using dimensional analysis and balancing buoyancy inertial and viscous forces as appropriate a theoretical analysis assuming steady axisymmetric motion captures a considerable part but not all of the processes involved the paper discusses quantitative applications of the results to the movement of magma in volcanic conduits the concepts indicate how bi directional convection in the conduit between a lava lake and a magma reservoir deep in the crust is the essential ingredient in the explanation of the long standing problem that the amount of degassing of sulphur dioxide from a lava lake in a volcanic crater can exceed by many orders of magnitude that consistent with the amount of lava solidified in the crater movies are available with the online version of the paper

southern menderes massif an incipient metamorphic core complex in western anatolia turkey in the southern sector of the menderes massif north of selimiye milas augen gneisses interpreted as a deformed peraluminous granite have been dynamothermally metamorphosed and are surrounded by and intrude a regionally metamorphosed palaeozoic envelope the granitic rocks exhibit a moderately dipping mylonitic foliation and nne ssw trending mineral elongation lineation the progressive deformation of the granitic rocks produces a structural sequence typical of an extensional shear zone marked from bottom to top by a very thick extensive zone of mylonites followed in turn by brecciated mylonite and cataclasite the kinematic indicators exhibit a top to the south down dip sense of shear these structures are attributed to exhumation of the granitic rocks of the massif along a major south dipping normal sense shear zone that accommodated crustal extension during late oligocene collapse of the orogen in western turkey thus the southern menderes massif may be interpreted as the exhumed footwall of a major extensional shear zone and possibly as an incipient core complex

miocene recent evolution of the western antalya basin and its linkage with the isparta angle eastern mediterranean abstract interpretation of 9500 km of multichannel seismic reflection profiles showed the presence of two major tectonic histories in western antalya basin spanning from the miocene or older to the pliocene quaternary a prominent fold thrust belt affects the miocene succession in the offshore the thrusts swing from a nw se strike with sw vergence in the northeast of the mapped area to a more northerly strike with westerly vergence at the western shelf edge of the deep basin the miocene deformation appears to continue offshore from the westerly directed thrusting seen onshore that characterizes the eastern edge of the isparta angle the contraction is consistent with the counterclockwise miocene rotation of the western side of the isparta angle determined from paleomagnetic studies the thrust belt forms the western extremity of the wider regional aksu kyrenia misis oroclinal culmination the tectonic activity experienced a period of relative quiescence across the western antalya basin during the messinian a major kinematic change occurred in the pliocene when the regional strain was partitioned into three spatially localized tectonic domains an extensional domain confined to the pliocene quaternary unit 1 occupied the northeastern portion of the study area a predominantly extensional domain with a few re activated pre existing miocene contractional structures occupied the southern and central portion of the study area and an extensional and or transtensional domain occupied the continental shelf and slope in the westernmost antalya basin these complexities relate to strike slip motions as the crustal block within the isparta angle moved northwards relative to the blocks to the north

new geophysical insight into the dynamics of stromboli volcano italy abstract a 56 hour gravity sequence recorded in the crater area of stromboli volcano is presented data were acquired during a period of normal strombolian activity high frequency gravity anomalies up to 20 gal t tens of seconds are observed comparison with independent data reveals that these changes reflect the response of the gravimeter excited by seismic waves during strombolian explosions correlated changes in the energy distribution over time appear in the continuous wavelet transforms of gravity and rms tremor but over different scales corresponding to periods centered at about 50 and 25 min for gravity and tremor respectively we infer that the rate of fresh magma supply to the shallow feeding system controls the energy distribution over time of the coupled components in gravity and rms tremor signals in particular the gravity signal with an average amplitude of 1 2 gal could be induced by temporary accumulations at shallow depth of the volatiles discharged by quiescent degassing changes in the rate of explosions from the summit craters correlate with changes in the amplitude of the coupled gravity and volcanic tremor oscillations implying that even though the slug genesis process behind the explosions occurs at deeper levels it is also controlled by the rate of gas rich magma supply from below negative gravity anomalies of about 20 gal over intervals of some hours are also observed separated by intervals of about 24 h they could be induced by increases in magma vesicularity in the uppermost part of the conduit plexus a view supported by i changes in the time space distribution of tremor amplitudes and ii increases in spattering activity from a summit vent both occurring during the development of the negative gravity anomalies the processes behind mild strombolian explosions do not trigger measurable gravity changes nevertheless the slug ascent before a major explosion could induce a precursory gravity signal

porosity reduction by pressure solution a theoretical model for quartz arenites pressure solution and the subsequent precipitation of the dissolved material may play an important role in the lithification of sandstones and limestones this paper presents a one dimensional model for a well sorted quartz arenite sequence undergoing diagenesis the sedimentary sequence is treated as a saturated porous medium in which pressure solution occurs at individual grain contacts quartz dissolved at grain contacts precipitates on free surfaces of adjacent grains this solution and precipitation process reduces porosity and forces the migration of pore fluid permeability decreases with porosity hindering fluid migration and excess fluid pressures are generated distributions of porosity pore pressure and fluid flow rates are given for several sedimentation rates and thermal gradients complete reduction of the primary intergranular porosity was accomplished in all cases examined by a depth of 3 5 km

least squares inversion of self potential sp data and application to the shallow flow of ground water in sinkholes we propose a least squares inversion algorithm to determine the spatially variable depth of the water table in shallow unconfined aquifers using self potential signals measured on the ground surface traditionally the water table is determined only at few locations using piezometers our approach relates its shape with the distribution of the self potential signals according to a fredholm equation of the first kind the latter is discretized to obtain a linear matrix formulation of the forward problem this new formulation is very general and can account for the resistivity distribution of the vadose zone it is used to setup the inverse problem using the approach of tarantola 1987 for a test site located in normandy france where 225 self potential measurements were performed over an area of 15 400 m2 ground water flows through the loess overlying a low permeability clay with flint weathered chalk at a depth between 1 to 7 meters into sinkholes in chalk bedrock the method determines the water table with a precision of 0 4 m

pliocene quaternary tectonic evolution of the gulf of gokova southwest turkey abstract evolution of the east west trending gokova graben structure is related to the north south extension of the aegean segment of the aegean anatolian microplate the pliocene quaternary successions surrounding the onland portion of the gokova graben as well as coeval successions within the marine portion of the graben are cut by at least three families of faults that strike northwest southeast east west and east northeast west southwest these orientations are inconsistent with a simple north south extensional regime interpretation of seismic reflection profiles multibeam bathymetry and gps vectors indicates that the gokova graben developed as a lazy s shaped graben in the back arc setting north of the hellenic arc a counterclockwise rotation of the aegean segment of the aegean anatolian microplate is the suggested mechanism for this geometry as subduction zone rolled back occurred during the pliocene quaternary the gulf of gokova is the youngest of a series of basins that developed within this large back arc system including the nisyros karpathos and kamilonisi basins collectively named to as the gokova nisyros karpathos graben it is proposed that this graben experienced a scissor like opening initiating from the west during the pliocene and progressing eastward during the quaternary faults that are seemingly un correlated onland and in the marine areas become remarkably aligned when the marmaris rhodes block is progressively rotated by 6 counterclockwise relative to the mugla block using a pole position located within the gulf of gokova the scissor like opening of the westernmost regions of the gokova graben likely occurred during the late pliocene whereas the central and eastern portions of the graben developed during the early middle pleistocene and late pleistocene holocene respectively the onset of the opening of the westernmost segment of the gokova nisyros karpathos graben occurred at a time earlier than the late pliocene

from palaeotectonics to neotectonics in the neotethys realm the importance of kinematic decoupling and inherited structural grain in sw anatolia turkey abstract in order to asses young i e neotectonic fault kinematics and the relation with plate tectonic processes in sw turkey we focused on the questions 1 what produced the structural grain i e how and when are faults generated 2 what was is the kinematic behaviour of these faults and 3 during which period s were these faults active firstly the distribution of faults has been investigated using a lineament analysis performed on satellite imagery and digital elevation models we define five main tectonic domains in sw turkey 1 and 2 the northern and southern western anatolian extensional provinces 3 the eastern hellenic arc including rhodes island and the submarine anaximander mountains 4 the lycian taurides and 5 the western limb of the isparta angle lineament analysis reveals dominance of three lineament groups i e nne ene and wnw trending in all identified domains variations in the relative importance of lineament groups exist and are attributed to the specific tectonic evolution of each domain a synthesis of recently published field data shows that the onset of activity of related fault groups is neither synchronous nor uniform the structural grain for the neotectonic deformation in sw turkey is formed during the last stage of palaeotectonic deformation stage 1 which is dominated by the onset of the menderes massif exhumation along a top n major detachment the datca break away fault seyitoglu g isik v and cemen i 2004 complete tertiary exhumation history of the menderes massif western turkey an alternative working hypothesis terra nova 16 358 364 and related se ward sliding of the lycian nappes in the footwall of this fault this stage is characterized by spatially variable types of deformation that are delineated by from nw to se the datca fault around the menderes lycian contact zone and the lycian frontal thrust zone respectively the kinematic decoupling along these structures explains the co existence of top n detachment type extension in the western anatolian extensional province and ongoing nappe emplacement and piggy back development in the lycian taurides the decoupling also explains the lateral complexity of deformation associated with later neotectonic deformation from late miocene onward stage 2 nne ssw extension dominated the western anatolian extensional province influenced by combined anatolian extrusion and hellenic subduction roll back contemporaneously bidirectional ese wnw and nne ssw extension controls the lycian taurides due to the effects of hellenic arc expansion superposed on extrusion roll back extension the zone of kinematic decoupling is characterized by structural complexity with local transpressional features during stage 3 post late pliocene the same types of extension prevail in the western anatolian extensional province and the lycian taurides although a third tectonic regime becomes gradually more important this regime is associated with a tectonic escape in the hellenic arc that induced forearc slivers to be sheared of the expanding arc along mostly sinistrally displacing ene trending strike slip zones several of these zones have been identified in the coastal zones of sw turkey either through recent seismicity or field observations and are especially focused in the lycian taurides domain here they form what is classically referred to as the fethiye burdur fault zone which becomes gradually penetrated from the sw by oblique or strike slip zones exemplifying the time transgressive nature of the tectonic escape mechanism zones of kinematic decoupling remain persistent throughout the entire early miocene recent tectonic evolution of sw turkey and explain the existence of differently deforming tectonic domains

conditions of magma storage degassing and ascent at stromboli new insights into the volcano plumbing system with inferences on the eruptive dynamics stromboli is known for its persistent degassing and rhythmic strombolian activity occasionally punctuated by paroxysmal eruptions the basaltic pumice and scoria emitted during paroxysms and strombolian activity respectively differ in their textures crystal contents and glass matrix compositions which testify to distinct conditions of crystallization degassing and magma ascent we present here an extensive dataset on major elements and volatiles co2 h2o s and cl in olivine hosted melt inclusions and embayments from pyroclasts emplaced during explosive eruptions of variable magnitude magma saturation pressures were assessed from the dissolved amounts of h2 oa nd co2 taking into account the melt composition evolution both pressures and melt inclusion compositions indicate that 1 ca basaltic melts entrapped in high mg olivines fo89 90 generate stromboli basalts through crystal fractionation and 2 the stromboli plumbing system can be imaged as a succession of magma ponding zones connected by dikes the 7 10 km interval where magmas are stored and differentiate is periodically recharged by new magma batches possibly ranging from ca basalts to basalts with a co2 rich gas phase these deep recharges promote the formation of bubbly basalt blobs which are able to intrude the shallow plumbing system 2 4 km where co2 gas fluxing enhances h2o loss crystallization and generation of crystal rich dense degassed magma chlorine partitioning into the h2o co2 bearing gas phase accounts for its efficient degassing 69 under the open system conditions of strombolian activity paroxysms however are generated through predominantly closed system ascent of basaltic magma batches from the deep storage zone in this situation crystallization is negligible and sulfur exsolution starts at 170 mpa chlorine remains dissolved in the melt until lower pressures only 16 being lost upon eruption finally we propose a continuum in explosive eruption energy from strombolian activity to large paroxysmal events ultimately controlled by variable pressurization of the deep feeding system associated with magma and gas recharges

periodic behavior in lava dome eruptions lava dome eruptions commonly display fairly regular alternations between periods of high activity and periods of low or no activity the time scale for these alternations is typically months to several years here we develop a generic model of magma discharge through a conduit from an open system magma chamber with continuous replenishment the model takes account of the principal controls on flow namely the replenishment rate magma chamber size elastic deformation of the chamber walls conduit resistance and variations of magma viscosity which are controlled by degassing during ascent and kinetics of crystallization the analysis indicates a rich diversity of behavior with periodic patterns similar to those observed magma chamber size can be estimated from the period with longer periods implying larger chambers many features observed in volcanic eruptions such as alternations between periodic behaviors and continuous discharge sharp changes in discharge rate and transitions from effusive to catastrophic explosive eruption can be understood in terms of the non linear dynamics of conduit flows from open system magma chambers the dynamics of lava dome growth at mount st helens 1980 1987 and santiaguito 1922 2000 was analyzed with the help of the model the best fit models give magma chamber volumes of 0 6 km3 for mount st helens and 65 km3 for santiaguito the larger magma chamber volume is the major factor in explaining why santiaguito is a long lived eruption with a longer periodicity of pulsations in comparison with mount st helens

dynamics of two phase conduit flow of high viscosity gas saturated magma large variations of sustained explosive eruption intensity the ascent of gas saturated magma in a conduit can lead to the transition from the laminar flow of a bubble rich melt to the turbulent flow of particle rich hot gas in upper part of the conduit this process is investigated with a help of a disequilibrium two phase flow model for steady and unsteady conditions for the description of different gas magma flow regimes in the conduit separated sets of equations are used the main difference from previous conduit flow models is the consideration of the pressure difference between a growing bubble and the surrounding melt for a bubbly liquid to evolve into a gas particle flow a critical overpressure value must be exceeded this transition region is simulated by means of a discontinuity namely by a fragmentation wave the magma flow calculations are carried out for a given conduit length and overpressure between the magma chamber and the atmosphere the steady solution of the boundary problem is not unique and there are up to five distinct steady regimes corresponding to fixed eruption conditions within the framework of the quasi steady approach governing parameters being varied monotonically the transition from one regime to another can take place suddenly and is accompanied by the fundamental restructuring of the conduit flow resulting in rapid or abrupt changes in the intensity of explosive eruptions abrupt intensification of an explosive eruption occurs when the chamber pressure becomes sufficiently less than saturation pressure and therefore corresponds to the case of shallow depth magma chamber and high initial water content a regime with minimum flow rate may relate to the growth of a lava dome following the explosive phase of eruption these models can explain geological observations that imply large and sudden changes of discharge rate in large magnitude explosive eruptions particularly at the transition between plinian phase and ignimbrite formation

dynamics of degassing at kilauea volcano hawaii at kilauea volcano hawaii the recent long lived eruptions of mauna ulu and pu u o o have occurred in two major stages defining a characteristic eruptive pattern the first stage consists of cyclic changes of activity between episodes of fire fountaining and periods of quiescence or effusion of vesicular lava the second stage consists only of continuous effusion of lava we suggest that these features reflect the dynamics of magma degassing in a chamber which empties into a narrow conduit in the volcano chamber gas bubbles rise through magma and accumulate at the roof in a foam layer the foam flows toward the conduit and its shape is determined by a dynamic balance between the input of bubbles from below and the output into the conduit the foam thickness is proportional to lq e2 l g 1 4 where l and l are the viscosity and density of magma e is the gas volume fraction in the foam g is the acceleration of gravity and q is the gas flux the bubbles in the foam deform under the action of buoyancy and the maximum permissible foam thickness is hc 2 e lgr where is the coefficient of surface tension and r is the original bubble radius if this critical thickness is reached the foam collapses into a large gas pocket which erupts into the conduit foam accumulation then resumes and a new cycle begins the attainment of the foam collapse threshold requires a gas flux in excess of a critical value which depends on viscosity surface tension and bubble size hence two different eruption regimes are predicted 1 alternating regimes of foam buildup and collapse leading to the periodic eruption of large gas volumes and 2 steady foam flow at the roof leading to continuous bubbly flow in the conduit the essential result is that the continuous process of degassing can lead to discontinuous eruptive behavior data on eruption rates and repose times between fountaining phases from the 1969 mauna uiu and the 1983 1986 pu u o o eruptions yield constraints on three key variables the area of the chamber roof must be a few tens of square kilometers with a minimum value of about 8 km2 magma reservoirs of similar dimensions are imaged by seismic attenuation tomography below the east rift zone close to the roof the gas volume fraction is a few percent and the gas bubbles have diameters lying between 0 1 and 0 6 mm these estimates are close to the predictions of models for bubble nucleation and growth in basaltic melts as well as to the observations on deep submarine basalts the transition between cyclic and continuous activity occurs when the mass flux of gas becomes lower than a critical value of the order of 103 kg s in this model changes of eruptive regime reflect changes in the amount and size of bubbles which reach the chamber roof

compaction and crystallization in magma chambers towards a model of the skaergaard intrusion the geochemical variations within the skaergaard intrusion provide an opportunity to discover what features of the intrusion can be understood using the simplest form of the equations governing the two phase flow of melt and matrix the equations governing the conservation of mass momentum and energy are first simplified by using the extended boussinesq approximation and then solved numerically to study the time dependent behaviour of a compacting solidifying layer at the base of a magma chamber when variations in the horizontal plane can be neglected the most important result is that the concept of a trapped liquid fraction which has been widely used to model the bulk composition of layered intrusions is a useful concept to describe the steady state behaviour of compacting layers this result is at first sight surprising because there is relative movement between the melt and crystals during compaction and the system is therefore open the reason why it is useful is because both the melt and the crystals are moving downwards in a frame fixed to the upper surface of the compacting layer because the mass of all elements must be conserved what goes into the top of the layer as melt and solid must come out of its bottom as a solid when the behaviour is not time dependent however when time dependent behaviour occurs the concept of a trapped liquid fraction ceases to be useful the governing equations are used to model the concentration of phosphorus uranium and rubidium in the lower part of the skaergaard intrusion where they behave incompatibly the observed behaviour requires the viscosity of the solid part of the compacting layer to have a value of 10 pa s

late miocene recent evolution of the finike basin and its linkages with the beydaglari complex and the anaximander mountains eastern mediterranean abstract interpretation of 2500 km of high resolution multi channel seismic reflection profiles shows that the finike basin evolved during the pliocene quaternary as the result of dramatic subsidence associated with loading of large imbricate thrust panels that carry the western tauride mountains in the north in the late miocene the stacked seaward prograded quaternary deltas presently resting at 1000 1500 m water depths corroborate the rapid subsidence of the region the ubiquitous presence of evaporites in the 2000 2400 m deep antalya basin and their absence in the 3000 3200 m deep finike basin suggest that the morphology of the finike basin and environs must have been considerably different during the messinian and that this region must have remained above the depositional base of evaporites during this time the transition from the messinian to the pliocene quaternary is marked by partitioning of stress into several discrete spatial domains a dextral strike slip fault zone developed along the western antalya basin extending from the apex of the isparta angle southward into the anaximander mountains this fault zone referred to as the antalya fault zone transected the anaximander mountains sensu lato separating the anaxagoras mountain from the anaximander and anaximenes mountains hence the finike basin sirri erinc plateau and the anaximander and anaximenes mountains remained part of the onland beydaglari block and experienced 20 counterclockwise rotation during the late miocene we envisage the boundaries of the beydaglari block as the burdur fethiye fault zone in the west the newly delineated antalya fault zone in the east and the east west trending sector of the sirri erinc plateau in the southwest kinematic evaluation of the structural elements mapped across the finike basin and the sirri erinc plateau suggest that two additional strike slip zones developed during the pliocene quaternary relaying the stress between the antalya fault zone in the east and the pliny strabo fault zone in the west

evolution of the bababurnu basin and shelf of the biga peninsula western extension of the middle strand of the north anatolian fault zone northeast aegean sea turkey abstract the generally transpressional character of the north anatolian fault zone in western turkey implies a transtensional character in the northern aegean sea the geological evolution of the basins lying above and immediately adjacent to this fault zone is still poorly understood similarly little information exists regarding the tectonic configurations created by the westerly and southerly extension of the middle and southern strands of the north anatolian fault zone into the northern aegean sea other than what has been inferred using somewhat speculative maps onland this study combines 1600 km of single channel seismic reflection profiles and piston core data with detailed land mapping to develop a comprehensive evolutionary model we suggest that the tectonic system of the biga peninsula and the northeastern aegean sea are characterized by transpressional broken slat geometry onland and transtensional broken slat geometry at sea the system includes a set of prominent ne sw striking faults with considerable strike slip component in the east northwestern turkey and eastern aegean sea and a second set of major nw se striking extensional faults in the west eastern greece we further suggest that rotational wedges form the link between the ne sw and nw se striking faults detailed mapping of the seismic data and fault linkages with the onland geology demonstrate that the middle strand of the north anatolian fault zone exits into the aegean sea near the town of behramkale and that it extends into the bababurnu pull apart basin in the northeastern aegean sea as a right releasing step over active during the quaternary

heterogeneous shear zone evolution the role of shear strain hardening softening mathematical models are proposed to describe heterogeneous shear zones characterized by variation thickness with time these models take into account several combinations of deformation type regime simultaneous simple shear pure shear and volume change and degree of strain localization increasing or decreasing shear zone thickness results respectively from strain hardening where deformation progressively diffuses into the host rock and strain softening where deformation gradually localizes within a narrow zone shear zone models are made of a series of layers each characterized by homogenous strain a quantitative evaluation of displacement thickness relationship and finite strain development may be obtained from each model temporal evolution depends on the following parameters i rate of shear strain hardening softening ii initial shear strain increment imposed to the system and iii thickness of homogenously deformed units within a layered shear zone based on data coming from natural shear zones displacement rates may be obtained independently of shear zone thickness

miocene to quaternary tectonostratigraphic evolution of the middle section of the burdur fethiye shear zone south western turkey implications for the wide inter plate shear zones abstract the burdur fethiye shear zone bfsz is a 75 to 90 km wide and 300 km long transtensional left lateral shear zone which is located in one of the most tectonically active regions in south western turkey a considerable number of studies suggested contradictory models of the evolution and neogene stratigraphy of the bfsz and in most cases the local river and alluvial fan deposits were mapped together with the lacustrine sediments and assigned a pliocene age we present new field data fault kinematic analyses and dem and earthquake data to characterize the tectonic controls and extent of the middle section of the bfsz including acipayam cameli and golhisar basins our field observations revealed two distinct sedimentary sequences that unconformably overlie the pre neogene basement the first sequence begins with middle upper miocene meandering and braided river sediments of the golhisar formation which transition upward into lacustrine sediments of the upper miocene lower pliocene ibecik formation this sequence is overlain by upper pliocene lower quaternary alluvial fan conglomerates mudstones and claystones of the dirmil formation the basin deposits located in the middle section of the bfsz consist of lacustrine sediments of a late miocene lake that likely evaporated due to the messinian salinity crisis fault kinematic analysis and dem and earthquake data indicate that the middle bfsz can be characterized as a heterogeneous left lateral transtensional shear zone rather than a major fault system our findings suggest that the middle section of the bfsz developed under the influence of progressive counter clockwise rotation of south western turkey the aegean graben system and the cyprus and hellenic arcs since the middle miocene

megacrystals track magma convection between reservoir and surface abstract active volcanoes are typically fed by magmatic reservoirs situated within the upper crust the development of thermal and or compositional gradients in such magma chambers may lead to vigorous convection as inferred from theoretical models and evidence for magma mixing recorded in volcanic rocks bi directional flow is also inferred to prevail in the conduits of numerous persistently active volcanoes based on observed gas and thermal emissions at the surface as well as experiments with analogue models however more direct evidence for such exchange flows has hitherto been lacking here we analyse the remarkable oscillatory zoning of anorthoclase feldspar megacrystals erupted from the lava lake of erebus volcano antarctica a comprehensive approach combining phase equilibria solubility experiments and melt inclusion and textural analyses shows that the chemical profiles are best explained as a result of multiple episodes of magma transport between a deeper reservoir and the lava lake at the surface individual crystals have repeatedly travelled up and down the plumbing system over distances of up to several kilometers presumably as a consequence of entrainment in the bulk magma flow our findings thus corroborate the model of bi directional flow in magmatic conduits they also imply contrasting flow regimes in reservoir and conduit with vigorous convection in the former regular convective cycles of 150 days at a speed of 0 5 mm s 1 and more complex cycles of exchange flow and re entrainment in the latter we estimate that typical 1 cm wide crystals should be at least 14 years old and can record several from 1 to 3 complete cycles between the reservoir and the lava lake via the conduit this persistent recycling of phonolitic magma is likely sustained by co 2 fluxing suggesting that accumulation of mafic magma in the lower crust is volumetrically more significant than that of evolved magma within the edifice

volcanism and the dynamics of open magma chambers the repeated eruption of many volcanoes is now accounted for by events taking place in a subterranean magma chamber which is open in the sense that the inflow of material to the chamber from below leads to a magma pressure p which exceeds the lithostatic pressure pl by an amount greater than the tensile strength of the chamber walls before the contents of the magma chamber have reached thermodynamic and geochemical equilibrium this is the condition which must be satisfied when an eruption occurs we have now derived a relationship giving the critical volume of added material v required to cause an eruption as a function of magma compressibility and the volume by which the chamber expands

a unified approach to geopressuring low permeability zone formation and secondary porosity generation in sedimentary basins geopressuring secondary porosity and low permeability zones occur in many of the world s sedimentary basins and are often associated with major petroleum reservoirs we present a mechanical model which simultaneously reproduces these phenomena assuming pressure solution to be the dominant rock deformation mechanism a solid state rock skeleton viscosity is introduced which relates the deformation of the rock skeleton to the effective stress numerical solutions for compaction indicate that a soft sedimentary layer preferentially compacts to form a low permeability zone there is a large liquid pressure gradient through the low permeability zone in the more slowly compacting region beneath the low permeability zone the pressure gradient remains hydrostatic but the absolute pressure can exceed the lithostatic pressure in the absence of hydraulic fracturing this results in the formation of secondary porosity

different stress states in the burdur isparta region sw turkey since late miocene times a reflection of a transient stress regime abstract the burdur isparta region is a transitional zone between two distinct neotectonic domains in turkey the burdur graben system as the northeastern part of the fethiye burdur fault zone and the kovada graben at the apex of the isparta angle each domain represents a particular stress regime fault data from unconsolidated pliocene and quaternary deposits were combined with stress states deduced from pre pliocene consolidated rocks in order to reconstruct the stress field evolution in the study area since late miocene different stress states were identified they were put in a stratigraphic framework and u th dating of fault related calcite precipitates proved to be an additional tool in constraining the history of the stress states the reconstructed history reflects a transient stress regime the evolving stress field indicates that the influence of the kovada stress regime fades through time and that the influence of the burdur stress regime is gaining importance suggesting a northeastwards progression of the fethiye burdur fault zone

complete tertiary exhumation history of the menderes massif western turkey an alternative working hypothesis the main exhumation of the menderes massif western turkey occurred along an originally n dipping datca kale main breakaway fault that controlled depositions in the kale and the gokova basins during the oligocene early miocene interval the isostatically controlled upward bending of the main breakaway fault brings the lower plate rocks to the surface in the early miocene e w trending n and s dipping graben bounding faults fragmented the exhumed dome shaped massif the development of half grabens by rolling master fault hinges has allowed further exhumation of the central menderes massif after the pliocene high angle normal faults cut all of the previous structures this model suggests that the menderes massif is a single large metamorphic core complex that has experienced a two stage exhumation process

lithosphere tearing at step faults response to edges of subduction zones abstract slab edges are a relatively common feature in plate tectonics two prominent examples are the northern end of the tonga subduction zone and the southern end of the new hebrides subduction zone near such horizontal terminations of subduction trenches ongoing tearing of oceanic lithosphere is a geometric consequence we refer to such kinks in the plate boundary as a subduction transform edge propagator or step other steps are the north and south ends of the lesser antilles trench the north end of the south sandwich trench the south end of the vrancea trench and both ends of the calabria trench volcanism near steps is distinct from typical arc volcanism in some cases slab edges appear to coincide with mantle plumes using 3d mechanical models we establish that step faults are stable plate tectonic features in most circumstances in the probably rare cases that the resistance to fault propagation is high slab break off will occur relative motion along the transform segment of the plate boundary often is non uniform and the step is not a transform plate boundary in the rigid plate tectonics sense of the phrase step propagation may result in substantial deformation rotation topography and sedimentary basins with a very specific time space evolution surface velocities are substantially affected by nearby steps

late cenozoic stress field in the cameli basin sw turkey a history of deformation has been determined for the cameli basin located in the western part of the major fethiye burdur fault zone interpreted as the on land continuation of pliny strabo fault system e g eastern boundary of the hellenic arc inversion of fault slip vectors affecting mio pliocene to quaternary formations in the cameli basin in the southwestern segment of the transtensional fethiye burdur fault zone yields two different normal faulting stress regimes characterized by a roughly orthogonal set of extensional axes a nw se n129 19 e 3 axis and a ne sw n50 16 e 3 axis the orientation of fault sets is predominantly around the ne sw direction in the major fethiye burdur fault zone making the extension nw se the mean r values are 0 74 and 0 69 for both extensions indicating a triaxial stress state which is clearly different from radial extension and from transitional to strike slip stress state the nw se extension is probably responsible for the formation of the cameli basin during mio pliocene time in contrast the inversion of focal mechanism solutions of shallow earthquakes occurring within the cameli basin identifies a present day predominantly extensional stress regime characterized by an approximately n s n184 e 3 axis which has an r value of 0 637 indicating a triaxial stress state the nearly orthogonal extensional stress regimes seem to have been acting contemporaneously with each other at different intensities from the mio pliocene onwards in sw turkey this may be attributed to the geodynamic effects related to the subduction of the african plate beneath anatolia diffusing along hellenic and cyprus arcs and in the west southwestward extrusion of anatolia our hypothesis is that the cause of the early nw se extension is the slab pull force due to the subduction process along the cyprus arc considered to be dominant up to plio quaternary the later ne sw to present day n s extension dominant since the plio quaternary is related to the combined forces of the anatolian extrusion and the subduction process along the hellenic arc

tectonic analysis of fault slip data sets using data that include the direction and the sense of motion on individual fault surfaces determined by slickenside lineations it is possible to reconstruct reduced stress tensors that correspond to the orientation of stress axes and to the ratio 2 3 1 3 between principal stress values 1 2 3 compression being positive no assumption is made concerning the orientation of fault planes relative to stress axes so that reactived faults are taken into account as well as newly created ones qualitative and quantitative methods for analysis of fault slip data were developed during the last 10 years the practical limitation of the methods and the necessity for critical field observations are emphasized these methods can be applied to focal mechanisms of earthquakes a more complex analysis of heterogeneous data sets involving an iterative separation of different stress systems is also discussed this analysis enables one to distinguish successive faulting events careful qualitative study in the field is in all cases essential

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

the role of volatiles in magma chamber dynamics many andesitic volcanoes exhibit effusive eruption activity1 with magma volumes as large as 107 109 m3 erupted at rates of 1 10 m3 s 1 over periods of years or decades during such eruptions many complex cycles in eruption rates have been observed with periods ranging from hours to years2 3 4 5 6 7 longer term trends have also been observed and are thought to be associated with the continuing recharge of magma from deep in the crust and with waning of overpressure in the magma reservoir here we present a model which incorporates effects due to compressibility of gas in magma we show that the eruption duration and volume of erupted magma may increase by up to two orders of magnitude if the stored internal energy associated with dissolved volatiles can be released into the magma chamber this mechanism would be favoured in shallow chambers or volatile rich magmas and the cooling of magma by country rock may enhance this release of energy leading to substantial increases in eruption rate and duration

magma oscillations in a conduit reservoir system application to very long period vlp seismicity at basaltic volcanoes 2 data inversion and interpretation at kīlauea volcano

mechanisms of unrest and eruption at persistently restless volcanoes insights from the 2015 eruption of telica volcano nicaragua many of earth s volcanoes experience well defined states of quiescence and unrest with unrest occasionally culminating in eruption some volcanoes however experience an unusually protracted i e decades long period of noneruptive unrest and are thus categorized as persistently restless volcanoes prvs the processes that drive persistently restless volcanism are poorly understood as our knowledge of prvs is currently based on a small number of case studies here we examine multidisciplinary observations of the 2015 eruptive episode at telica volcano nicaragua in the context of its long term behavior we suggest that the latter phases of the 2015 eruption were ultimately driven by destabilization of its shallow magma reservoir based on previous geodetic seismic studies of telica geirsson et al 2014 https doi org 10 1016 j jvolgeores 2013 11 009 rodgers et al 2013 https doi org 10 1016 j jvolgeores 2013 08 010 and 2015 https doi org 10 1016 j jvolgeores 2014 11 012 and on multiparameter observations at telica over a 7 year period we propose that three distinct states of unrest occur at telica over decadal timescales a stable open state involving steady conduit convection and two distinct unstable states that may lead to eruptions in the weak sealing state phreatic explosions result from steady conduit convection underlying a weak seal in the destabilized state destabilization of the top of the convecting magma in the conduit leads to rapid accumulation of high pressures leading to strong impulsive phreatomagmatic explosions our observations and interpretations suggest that continuous seismic ground based deformation gas emission and thermal monitoring and interpretation of these data within a paradigm of sustained conduit convection modulated by episodes of sealing and destabilization of shallow magma reservoirs may allow robust forecasting of eruption potential energy and duration at telica and similar prvs worldwide

counter current convection in a volcanic conduit abstract volcanoes of strombolian type are able to maintain their semi permanent eruptive states through the constant convective recycling of magma within the conduit leading from the magma chamber in this paper we study the form of this convection using an analytic model of degassing two phase flow in a vertical channel we provide solutions for the flow at small grashof and large prandtl numbers and we suggest that permanent steady state counter current convection is only possible if an initial bubbly counter current flow undergoes a regime transition to a churn turbulent flow we also suggest that the magma in the chamber must be under pressured in order for the flow to be maintained and that this compromises the assumed form of the flow

the late early miocene acipayam piggy back basin refining the last stages of lycian nappe emplacement in sw turkey abstract alluvial fan to shallow marine sedimentation in the acipayam piggy back basin took place in the hinterland zone of the se facing lycian nappe stack and constrains the age and style of late stage advance of these nappes syn orogenic sedimentation commenced in burdigalian time and is marked by coarse grained alluvial fan deposits that directly overlie mesozoic ophiolitic rocks palaeocurrent data obtained from these coarse clastic units suggest a south southeastward drainage the succession fines upwards and passes into fluvial deposits that become increasingly enriched in carbonate clasts derived from tectonically deeper seated nappes suggesting progressive unroofening of the nappe pile upwards the succession is transitional to a late burdigalian early langhian marginal marine succession consisting of off shore fines with coal seams that overly both the coarse clastic sediments and basement rocks clastic sedimentation ceased at the end of early langhian based on reef carbonates that cap the succession shallow marine deposits and overlying reef carbonates confirm a marine transgression that has been reported from elsewhere in the tauride belt detailed sedimentology of the acipayam basin fill succession its age and overall tectonic setting imply that during burdigalian time the succession was deposited in a piggy back basin located in the hinterland zone of actively moving thrust sheets we propose a model in which thick skinned thrusting invoked inversion of early extensional faults in the autochthon and may explain the generation of large open folds with thick sedimentary sequences in their core the formation of these large folds may have importantly influenced the frontal accretion such that active shortening moved into the hanging wall resulting in episodic nappe advanced of structurally higher nappes in a mode similar to thin skin thrusting the tectonosedimentary evolution of the acipayam piggy back is strongly dependent on its position relative to the hinge of the large open fold the absence of any compressional signatures in the basin fill succession indicates that these thrust translations ceased shortly after aquitanian time by serravallian the succession was interrupted and the region was uplifted to its present elevation probably by gravitationally isostatic orogenic rebound of the nappe stack after these episodes tectonic extension predominated and the succession became dissected by nappe front parallel normal faults that bound the present cameli basin

exhumed conduit records magma ascent and drain back during a strombolian eruption at tongariro volcano new zealand field evidence from a basaltic andesite dyke preserved in the eroded wall of a scoria cone at red crater tongariro volcano new zealand records a history of up conduit magma flow during a strombolian eruption subsequent drain back and final cessation of flow the dyke intrudes pre strombolian andesite lavas and the overlying proximal basaltic andesite scoria deposits associated with contemporaneous lavas which are in turn overlain by laminated lapilli tuff and large blocks textural and kinematic evidence of ductile shear recorded in basaltic andesite at the dyke margins records magma deformation imposed by bypassing movement of magma up the centre of the conduit during the eruption whereas the basaltic andesite occupying the central part of the lowermost exposures of the dyke preserves ductile flow folds with the opposite down flow shear sense the evidence indicates that the downward magma flow followed the eruption and this draining left the central part of the dyke empty unfilled at uppermost levels we discuss the kinematic constraints in the context of the criteria for up flow of mafic magma and present the factors most likely to result in a final drain back event with reference to experimental and numerical work we propose a draining model for the end of this eruption and that magmatic drain back may feature commonly during closing stages of strombolian eruptions at mafic volcanoes drain back which leaves large cavities in a volcanic edifice could result in hazardous structural instabilities