a palaeomagnetic study of some basaltoids and ores from the pontic ranges northern turkey palaeogeographic implications the palaeomagnetism of basic rocks and sulphide ores has been studied in the kure area pontic ranges turkey progressive alternating field demagnetization revealed a characteristic remanent magnetization in all investigated rock types except a dacite the following virtual geomagnetic poles were obtained basalt and quartz diabase oldest d 59 i 66 95 4 8 pole 49 n 93 e diabase d 210 i 15 95 15 0 pole 47 n 167 e massive sulphide ores d 107 i 63 95 8 7 pole 18 n 80 e peridotite d 131 i 54 95 10 9 pole 2 s 72 e amphibolitized diabase youngest d 293 i 59 95 12 6 pole 40 s 145 e the longidutinal difference in pole positions between the oldest and the youngest rocks is interpreted as being due to a post permian counterclockwise rotation of the studied region in relation to the african continent in addition there are indications of local rotational movements within the kure area

imaging and modeling the ionospheric airglow response over hawaii to the tsunami generated by the tohoku earthquake of 11 march 2011 1 although only centimeters in amplitude over the open ocean tsunamis can generate appreciable wave amplitudes in the upper atmosphere including the naturally occurring chemiluminescent airglow layers due to the exponential decrease in density with altitude here we present the first observation of the airglow tsunami signature resulting from the 11 march 2011 tohoku earthquake off the eastern coast of japan these images are taken using a wide angle camera system located at the top of the haleakala volcano on maui hawaii they are correlated with gps measurements of the total electron content from hawaii gps stations and the jason 1 satellite we find waves propagating in the airglow layer from the direction of the earthquake epicenter with a velocity that matches that of the ocean tsunami the first ionospheric signature precedes the modeled ocean tsunami generated by the main shock by approximately one hour these results demonstrate the utility of monitoring the earth s airglow layers for tsunami detection and early warning

surface and bed topography of trapridge glacier yukon territory canada digital elevation models and derived hydraulic geometry measurements of ice thickness and surface elevation are prerequisite to many glaci ological investigations a variety of techniques has been develo ped for inter pret ation of these data including means of constructing regularly gridded digital eleva tion models dem s for use in numcrical studies here we present a simple yet stati sti cally sound method for processing ice pe netr ating radar data and descr ibe a tech nique for interpol ating these data onto a regular grid dems generatcd fort rapridge glacier yukon territory canada are used to derive geometric quantities lhal give pre liminary insights into the underlying basin scale hydrol ogical syste m this simple geo metric analysis suggests that at low water press ures a dendrilic drainage netw ork exists that evolves into a uniaxial morphology as water pressure approaches notation these pre dictions are compared to hydraulic connection probabilities based on bore hole drilling

the response of black rapids glacier alaska to the denali earthquake rock avalanches 1 we describe the impact of three simultaneous earthquake triggered rock avalanches on the dynamics of black rapids glacier alaska by using spaceborne radar imagery and numerical modeling we determined the velocities of the glacier before and after landslide deposition in 2002 by using a combination of ers 1 ers 2 tandem radarsat 1 and alos palsar synthetic aperture radar data ice velocity above the debris covered area of the glacier increased up to 14 after the earthquake but then decreased 20 by 2005 within the area of the debris sheets mean glacier surface velocity increased 44 within 2 years of the landslides at the downglacier end of the lowest landslide where strong differential ablation produced a steep ice cliff velocities increased by 109 over the same period by 2007 ice velocity throughout the debris area had become more uniform consistent with a constant ice flux resulting from drastically reduced ablation at the base of the debris without further analysis we cannot prove that these changes resulted from the landslides because black rapids glacier displays large seasonal and interannual variations in velocity however a full stokes numerical ice flow model of a simplified glacier geometry produced a reversal of the velocity gradient from compressional to extensional flow after 5 years which supports our interpretation that the recent changes in the velocity field of the glacier are related to landslide induced mass balance changes

comparison between the hot spot and geomagnetic field reference frames hot spots are located on the earth s surface and are caused by hot plumes of upwelling mantle material they manifest themselves by volcanic activity which changes its location in response to the movement of the lithosphere over the mantle plume it has been suggested1 3 that hot spots are relatively stationary with respect to each other and also that they represent a frame of reference with which to measure the absolute movement of the lithospheric plates over the surface of the earth another frame of reference can be partially defined by the position of the mean magnetic dipole field of the earth as the dipolar field is believed to be closely related to the spin axis this frame of reference automatically gives information about the palaeolatitude and orientation of the lithospheric plates but since the position of the ancient dipole field of the earth does not give any information about palaeolongitude and since in many cases the definition of the field is relatively poor due to less than adequate rock collections during the time of interest hot spot reference frames have been favoured by many people we now report a comparison of the two frames of reference and show that over the past 200 myr there has been relative movement between the two frames of reference of about 20 and that this motion has not been constant with time

deepening of inner gorges through subglacial meltwater an example from the unesco entlebuch area switzerland this paper explores the mechanisms by which inner gorges in the alps were formed it focuses on the ca 1 5 km long 80 m deep and a few hundred meter wide lammschlucht located in the northern foothills of the central alps we reconstructed the glacial cover using lateral moraines and hanging talus cones that record the elevation of the ice surface at the deglaciation stage of the lgm last glacial maximum we used the reconstructed ice thickness patterns to calculate the erosional potential of the subglacial meltwater the applied model is based on the principle of energy conservation and yields the pattern of downstream changes of the dynamic pressure which is considered a measure for erosion potential the model results suggest a maximum of the dynamic pressure at the end of the inner gorge we interpret therefore that the subglacial meltwater scoured the reach toward the end of the lammschlucht because of the enhanced dynamic pressure which was ultimately controlled by the ice overburden post glacial fluvial erosion then resulted in a readjustment through a regressive shift of the erosional front along the inner gorge farther upstream the current location of this front lies almost in the middle of the lammschlucht inner gorge where a step pool channel changes into a straight plane bed channel flowing on a deeply scoured bedrock

paleomagnetism of the istria peninsula yugoslavia 280 core samples were collected from upper jurassic cretaceous and eocene sediments outcropping in the istria peninsula yugoslavia due to the very low intensities of the initial natural remanent magnetizations more than 50 of the collection consisting mainly of rock samples of jurassic and eocene sediments was not suitable for paleomagnetic studies the cretaceous samples yield a mean paleomagnetic pole lat 53 long 275 and 95 4 8 which is significantly different from the african and european paleomagnetic poles of the same age the position of the istria peninsula on the autochthonous adriatic platform allows the result to be interpreted as applicable to all the autochthonous periadriatic region this new paleomagnetic result indicates that the autochthonous adriatic platform rotated counterclockwise over an angle of about 30 with respect to africa in post mesozoic times

geometry bed topography and drainage system structure of the haut glacier d arolla switzerland as part of an integrated study of the hydrology meltwater quality and dynamics of the haut glacier d arolla switzerland the glacier s drainage network structure was determined from patterns of dye recovery in 342 injection experiments conducted from 47 moulins distributed widely across the glacier this structure was compared with theoretical predictions based upon reconstructed patterns of water flow governed by a the subglacial hydraulic potential surface and b the subglacial bedrock surface these reconstructions were based on measurements of ice surface and bedrock topography obtained by a combination of ground survey and radio echo sounding techniques the two reconstructions simulate the drainage system structures expected for a closed channels in which water is pressurized by the overlying ice and b gravity driven open channel flow the closed channel model provides the best fit to the observed structure even though theoretical calculations suggest that under summer discharge conditions open channel flow may be widespread beneath the glacier possible reasons for this apparent discrepancy are discussed

diurnal variability of subglacial drainage conditions as revealed by tracer experiments 1 the morphology of the drainage system of unteraargletscher switzerland and the diurnal variability of drainage conditions were investigated by conducting a series of tracer tests over a number of discharge cycles during the ablation season 2000 dye injections into a moulin were repeated at intervals of a few hours and were accompanied by simultaneous measurements of discharge of supraglacial meltwater draining into the moulin and bulk runoff in the proglacial stream fast transit velocities in conjunction with low dispersion values suggest that the tracer was routed through a hydraulically efficient channelized drainage system however detailed analyses reveal a large diurnal variability in terms of transit velocity and dispersion coefficient this finding underlines the difficulty of detecting a possible drainage system evolution based on single tracer tests conducted at coarse temporal intervals furthermore the obtained velocity discharge relationships display pronounced hysteresis we suggest that the evolution of the cross sectional area of an ice walled conduit and the modulation of inflow at the junction of a tributary moulin to a main subglacial channel are responsible for the observed behavior

first paleomagnetic results from mio pliocene series of the hellenic sedimentary arc abstract paleomagnetic measurements have been conducted on the mio pliocene series along the external sedimentary hellenic arc in order to detect the presence or absence of rotational deformations in different sections of the arc in the central eastern part of the arc crete and rhodes paleomagnetic directions are very closely aligned along the north south direction showing that this portion of the arc has not undergone significant rotation since at least 7 m y for crete and 4 m y for rhodes in the western and northwestern parts results from south peloponnesos zakinthos kephallinia and corfu indicate that this section of the arc has undergone a clockwise rotation detailed analysis of the data from the three ionian islands shows that their rotation began about 5 m y b p and has proceeded since then at roughly 5 m y giving a total amplitude of about 26 it is suggested that the beginning of this rotation is related to the lower pliocene compressive phase which most probably initiated the tectonic activity of the present day ionian margin

time dependent propagation of tsunami generated acoustic gravity waves in the atmosphere abstracttsunami generated linear acoustic gravity waves in the atmosphere with altitude dependent vertical stratification and horizontal background winds are studied with the long term goal of real

kuannersuit glacier revisited constraining ice dynamics landform formations and glaciomorphological changes in the early quiescent phase following the 1995 98 surge event abstract kuannersuit glacier in west greenland experienced a major surge in 1995 1998 where the glacier advanced 10 5 km down valley in this paper we examine how the quiescent phase has progressed until 2015 with respect to ice dynamics landform formations and glaciomorphological changes in the initial quiescent phase 2001 2005 ice velocities along the center flowline were 37 55 higher than ice velocities 6 3 9 0 m yr 1 in 2005 2015 and a linear relationship between ice velocity and distance from the glacier front which existed during the initial quiescent phase had disappeared in 2005 2015 between 2001 and 2015 the post surge glacier tongue thinned by 84 0 6 3 m equal to 6 0 0 5 m yr 1 the 30 m high terminal moraine detached from the active glacier along the uppermost thrust band between 2005 and 2015 after which the glacier front receded 1 5 km between the terminal moraine and the glacier front observations suggested that a proximal outwash plain was forming on top of glacier ice and that glacier naled icing aufeis was incorporated into the outwash plain in less dynamic areas with gently sloping topography along the lateral glacier margins crevasse squeeze ridges were melting out the most prominent glaciomorphological feature in 2015 was a c 1 km long gorge with c 30 40 m high ice cliffs this gorge had formed into the glacier front following the collapse of a series of chasms above the main subglacial channel roof collapse processes above subglacial channels had a significant impact on the glacier s mass loss and on the glaciomorphology during the quiescent phase earlier observations from 1913 suggest that the formation of this gorge is a reoccurring phenomenon during the quiescent phase a lower pothole field on the glacier tongue that existed during the initial quiescent phase had completely disappeared in 2015 while a larger upper pothole field in the reservoir area prevailed during the initial quiescent phase the subglacial drainage system developed into a stable channelized network although a jokulhlaup from a large ice dammed lake occurred this single event was dated to have occurred between 11 and 13 august 2006 and the lake did not refill the spatiotemporal association and evolution of glacial and glaciomorphological landforms at kuannersuit glacier are likely similar to processes at many other surging and rapidly receding glaciers of similar size

from sumatra 2004 to tohoku oki 2011 the systematic gps detection of the ionospheric signature induced by tsunamigenic earthquakes the recent tsunamigenic earthquake in tohoku 11 march 2011 strongly affirms one more time after the sumatra event 26 december 2004 the necessity to open new paradigms in oceanic monitoring detection of ionospheric anomalies following the sumatra tsunami demonstrated that ionosphere is sensitive to the tsunami propagation observations supported by modeling proved that tsunamigenic ionospheric anomalies are deterministic and reproducible by numerical modeling via the ocean neutral atmosphere ionosphere coupling mechanism in essence tsunami induces internal gravity waves propagating within the neutral atmosphere and detectable in the ionosphere most of the ionospheric anomalies produced by tsunamis were observed in the far field where the tsunami signature in the ionosphere is clearly identifiable in this work we highlight the early signature in the ionosphere produced by tsunamigenic earthquakes and observed by gps measuring the total electron content close to the epicenter we focus on the first hour after the seismic rupture we demonstrate that acoustic gravity waves generated at the epicenter by the direct vertical displacement of the source rupture and the gravity wave coupled with the tsunami can be discriminated with theoretical support we illustrate the systematic nature of those perturbations showing several observations nominally the ionospheric perturbation following the tsunamigenic earthquakes in sumatra on 26 december 2004 and 12 september 2007 in chile on 14 november 2007 in samoa on 29 september 2009 and the recent catastrophic tohoku oki event on 11 march 2011 based on the analytical description we provide tracks for further modeling efforts and clues for the interpretation of complex and thus often misleading observations the routine detection of the early ionospheric anomalies following the rupture highlights the role of ionospheric sounding in the future ocean monitoring and tsunami detection

book review paleomagnetism and the continental crust j d a piper open university press milton keynes 1987 434 pp 35 00 isbn 0335 15201 5

the 2009 samoa and 2010 chile tsunamis as observed in the ionosphere using gps total electron content 1 ground based global positioning system gps measurements of ionospheric total electron content tec show variations consistent with atmospheric internal gravity waves caused by ocean tsunamis following two recent seismic events the samoa earthquake of 29 september 2009 and the chile earthquake of 27 february 2010 both earthquakes produced ocean tsunamis that were destructive to coastal communities near the epicenters and both were observed in tidal gauge and buoy measurements throughout the pacific ocean we observe fluctuations in tec correlated in time space and wave properties with these tsunamis using the jet propulsion laboratory s global ionospheric mapping software these tec measurements were band pass filtered to remove ionospheric tec variations with wavelengths and periods outside the typical range for tsunamis observable variations in tec appear correlated with the tsunamis in some locations hawaii and japan but not in others southern california or near the epicenters where variations are observed the typical amplitude tends to be 0 1 0 2 tec units for these events on the order of 1 of the background tec value these observations are compared to estimates of expected tsunami driven tec variations produced by embry riddle aeronautical university s spectral full wave model an atmosphere ionosphere coupled model and are found to be in good agreement significant tec variations are not always seen when a tsunami is present but in these two events the regions where a strong ocean tsunami was observed coincided with clear tec observations while a lack of clear tec observations coincided with smaller sea surface height amplitudes there exists the potential to apply these detection techniques to real time gps tec data providing estimates of tsunami speed and amplitude that may be useful for early warning systems

elucidating changes in the degree of tracer dispersion in a subglacial channel tracer injections into a subglacial channel at unteraargletscher switzer land were repeated at intervals of about 2 hours over two diurnal discharge cycles in august and september 2000 records of dye concentration reveal a pronounced hysteresis in the velocity dispersion relationship thereby indicating alterations in the drainage system theoretical considerations for ro thlisberger channels suggest an evolution of the conduit cross section in response to a diurnally varying discharge we studied the relation between conduit cross section and tracer dispersion with numerical tracerexperiments thevelocity fieldforsteady flow throughagivenconduitgeometry is calculated using a commercial flow solver tracer transport is represented by a scalar volume which is advected by the velocity field experiments were conducted for several scenarios by varying flow velocity conduit geometry and conduit roughness results show only a weak dependence of dispersion on conduit size in contrast changes in roughness of the conduit walls reveal a strong effect on tracer dispersion therefore to explain the observed hysteresis in the velocity dispersion relationship we suggest that the evolution of a subglacial flow path might involve changes in roughness

atmospheric airglow fluctuations due to a tsunami driven gravity wave disturbance 1 a spectral full wave model is used to study the upward propagation of a gravity wave disturbance and its effect on atmospheric nightglow emissions gravity waves are generated by a surface displacement that mimics a tsunami having a maximum amplitude of 0 5 m a characteristic horizontal wavelength of 400 km and a horizontal phase speed of 200 m s the gravity wave disturbance can reach f region altitudes before significant viscous dissipation occurs the response of the oh meinel nightglow in the mesopause region 87 km altitude produces relative brightness fluctuations which are 1 of the mean for overhead viewing the wave amplitudes grow as the wave disturbance propagates upward which causes the thermospheric nightglow emission responses to be large for overhead viewing the brightness fluctuations are 50 and 43 of the mean for the oi 6300 a and o 1356 a emissions respectively the total electron content fluctuation is 33 of the mean for overhead viewing for oblique viewing the relative brightness fluctuations are slightly smaller than those obtained for overhead viewing in spite of this the thermospheric nightglow brightness fluctuations are large enough that oblique viewing could provide early warning of an approaching tsunami thus the monitoring of thermospheric nightglow emissions may be a useful augmentation to other observational techniques of tsunami effects in the thermosphere ionosphere system

ionospheric gps total electron content tec disturbances triggered by the 26 december 2004 indian ocean tsunami 1 tsunami ionospheric disturbances tids of the 26 december 2004 mw 9 3 sumatra earthquake are detected by the total electron content tec of ground based receivers of the global positioning system gps in the indian ocean area it is found that the tsunami waves triggered atmospheric disturbances near the sea surface which then traveled upward with an average velocity of about 730 m s 2700 km hr into the ionosphere and significantly disturbed the electron density within it results further show that the tids which have maximum height of about 8 6 17 2 km periods of 10 20 min and horizontal wavelengths of 120 240 km travel away from the epicenter with an average horizontal speed of about 700 km hr 190 m s in the ionosphere

late paleozoic rotations of corsica and sardinia new evidence from paleomagnetic and k ar studies abstract a detailed paleomagnetic investigation of so called permian volcanics was undertaken in southeastern and northwestern sardinia k ar dating on separate minerals representing 30 sites on corsica and sardinia showed that the first calc alkaline cycle had taken place in westphalo stephanian times and the second alkaline one at the end of the stephanian 246 paleomagnetic specimens from 28 sites of southeastern sardinia and 2 sites from the northwest were demagnetized by alternating field and thermal processes the directions of characteristic magnetizations are d 85 i 6 95 5 for the volcanics of southeastern sardinia and d 126 i 1 for the nurra samples these mean directions differ from those of northwestern corsica and northern sardinia gallura the paleomagnetic results display good grouping for each volcanic complex but exhibit a geographical dispersion of the mean directions this scattering suggests significant motions in late hercynian times

an empirical model of the earth s horizontal wind fields hwm07 1 the new horizontal wind model hwm07 provides a statistical representation of the horizontal wind fields of the earth s atmosphere from the ground to the exosphere 0 500 km it represents over 50 years of satellite rocket and ground based wind measurements via a compact fortran 90 subroutine the computer model is a function of geographic location altitude day of the year solar local time and geomagnetic activity it includes representations of the zonal mean circulation stationary planetary waves migrating tides and the seasonal modulation thereof hwm07 is composed of two components a quiet time component for the background state described in this paper and a geomagnetic storm time component dwm07 described in a companion paper

geometry and flow conditions of subglacial water at south cascade glacier washington state u s a an analysis of tracer injections tracers were injected into south cascade glacier to determine the flow condition and geometry of the subglacial water system results indicate that two distincts drainage basins on the glacier feed the two main streams flowing from the glacier in the largest basin two parallel drainage networks exist one englacial and the other subglacial

kinematic evolution of the romanian carpathians abstract the regional pattern of contraction and extension directions and the evolution of the strain field from paleogene to neogene times enabled a reconstruction of the migration path of the carpathian collision front the carpathian nappes were thrust around the moesian plate during paleogene and early neogene times and protruded into a small oceanic embayment between the moesian and european plates the arc structure of the carpathian fold thrust belt was formed in late neogene times as a result of the eastward escaping tisza dacia block due to n directed convergence of the adriatic plate and the retreating subduction of an oceanic slab brittle deformation structures in the romanian carpathians suggest three tectonic events related to major plate motions 1 paleogene to middle miocene ne to ene contraction caused right lateral curved strike slip faults 2 middle miocene to pliocene fan shaped orientations of contraction directions were caused by right lateral oblique convergence in the southern carpathians frontal convergence in the southern eastern carpathians and left lateral convergence in the northern eastern carpathians 3 pleistocene to holocene general e w extension and n s contraction in the carpathian arc and local ese wnw contraction in the vrancea area is related to the late roll back stage and break off of the subducted slab in the bend area

changes in geometry and subglacial drainage derived from digital elevation models unteraargletscher switzerland 1927 97 digital elevation models of the bed and surface of unteraargletscher switzerland are used to reconstruct the theoretical pattern of basal water drainage for the years 1927 1947 1961 and 1997 during which period the glacier was thinning and receding the theoretical drainage pattern for 1997 compares well in a broad sense with the locations of active moulins and the hydraulic connection status of boreholes drilled to the glacier bed changes in the basal water flow pattern over the period 1927 97 that are revealed by the theoretical reconstructions of the subglacial drainage system structure are likely to have resulted from changes in glacier geometry concurrent with the retreat and thinning of the glacier the height of medial moraines increased probably due to the insulating effect of the debris cover reducing the melt of the underlying ice this increase of moraine heights has led to the formation of hydraulic barriers at the glacier bed such that water flow has become channelized beneath the ice along drainage axes that parallel the course of the medial moraines on the glacier surface

paleomagnetic studies on sedimentary jurassic rocks from southern bulgaria abstract paleomagnetic investigations were performed on jurassic sediments sampled in the mobile area of bulgaria comprising srednogorie kreiste and stranja the main carriers of magnetic properties of rocks studied are pigmentary haematite and goethite of post sedimentary origin the characteristic component of natural remanence carm isolated by means of analysis of demagnetization procedure is secondary and was acquired after the main tectonic event that took place in this area during the upper cretaceous the carm directions before tectonic correction are close to the results for upper cretaceous magmatic rocks from srednogorie the mean carm direction and the corresponding polar position obtained for the whole region studied are compared with reference data for the eurasian platform the difference between the reference and our data implies anticlockwise rotation of southern bulgaria relative to eurasia by 10 20 and a northward tilt of the region under study by 10 15 after acquisition of carm

reappraisal of paleomagnetic data from gargano south italy vandenberg j 1983 reappraisal of paleomagnetic data from gargano south italy in e mcclelland brown and j vandenberg editors palaeomagnetism of orogenic belts tectonophysics 98 29 41 the platform limestones of apulia italy outcropping in the gargano peninsula have been restudied paleomagnetic research has been carried out on upper cretaceous lower cretaceous and jurassic rocks despite the low intensities of the nrm 10 100 pa m all samples 268 could be cleaned by stepwise a f and or thermal demagnetization treatments nrm directions could be determined accurately and reproducibly for 85 of the samples using a sct cryogenic magnetometer and double precision measuring procedures nrm of the jurassic limestone is carried by secondary haematite and the results are therefore rejected from further consideration the upper and lower cretaceous limestones have an nrm carried by magnetite minor bedding tilt corrections improve the grouping of the site mean results the upper cretaceous scaglia limestone turonian senonian reveals a characteristic mean direction of decl 327 7 incl 38 2o a ss 4 3 21 sites while the lower cretaceous maiolica limestone neocomian aptian albian reveals a characteristic mean direction of decl 303 1 o incl 35 1 as s 8 7o 8 sites the cretaceous results show a post aptian albian counterclockwise rotation of about 25 which is expressed by the smeared distribution of the late cretaceous site mean results and a post senonian i e tertiary counterclockwise rotation of the same amount with respect to the pole these results are in excellent agreement with contemporaneous paleomagnetic results from other peri adriatic regions a tertiary counterclockwise rotation of all the stable adriatic block is strongly supported by the new results

upper palaeozoic palaeomagnetic results from algeria and tunisia abstract igneous and sedimentary rocks of devonian carboniferous and permian age from algeria and tunisia show evidence for remagnetisations that are partially removed or reduced by thermal demagnetisation although alternating magnetic fields were ineffective in removing this effect from igneous rocks nonetheless the remaining devonian data are too sparse for adequate interpretation carboniferous sediments contain a magnetic component that can be isolated successfully and which appears to define a genuine mid to late carboniferous shallow southeasterly geomagnetic field direction although demagnetisation of carboniferous igneous rocks was less successful the same component appeared to be present in these rocks permian and permo triassic sediments show only poorly defined high blocking temperature directions and those of permian age do not appear to be magnetically consistent with other african data it is thought that some of the directions isolated may be indicators of local tectonic rotations but that it is premature to use these observations to define such rotations in the north african region

structure morphology and water flux of a subglacial drainage system midtdalsbreen norway digital elevation models of the surface and bed of midtdalsbreen norway are used to calculate subglacial hydraulic potential and infer drainage system structure for a series of subglacial water pressure assumptions ranging from atmospheric to ice overburden a distributed degree day model is used to calculate the spatial distribution of melt on the glacier surface throughout a typical summer which is accumulated along the various drainage system structures to calculate water fluxes beneath the glacier and exiting the portals for the different water pressure assumptions in addition 78 dye tracing tests were performed from 33 injection sites and numerous measurements of water discharge were made on the main proglacial streams over several summer melt seasons comparison of the calculated drainage system structures and water fluxes with dye tracing results and measured proglacial stream discharges suggests that the temporally and spatially averaged steady state water pressures beneath the glacier are 70 of ice overburden analysis of the dye return curves together with the calculated subglacial water fluxes shows that the main drainage network on the eastern half of the glacier consists of a hydraulically efficient system of broad low channels average width height ratio 75 the smaller drainage network on the west consists of a hydraulically inefficient distributed system dominated by channels that are exceptionally broad and very low average width height ratio 350 the even smaller central drainage network also consists of a hydraulically inefficient distributed system dominated by channels that are very broad and exceptionally low average width height ratio 450 the channels beneath the western and central glacier must be so broad and low that they can essentially be thought of as a linked cavity system

a refined apparent polar wander curve for the transdanubian central mountains and its bearing on the mediterranean tectonic history abstract recently obtained palaeomagnetic data have given a fairly detailed apparent polar wander a p w curve for the mesozoic of the transdanubian central mountains which has been compared with other a p w curves from the mediterranean area the similarity of the a p w curves enabled a unified a p w curve to be constructed for the central mediterranean region it has been shown that the new mediterranean a p w curve is in full agreement even in details with the updated a p w curve for africa this confirms the existence during the entire mesozoic of a single central mediterranean megatectonic unit rigidly attached to africa its positions with respect to the pole can now be traced back in more detail than before

seasonal changes in the morphology of the subglacial drainage system haut glacier d arolla switzerland dye tracing techniques were used to investigate the glacier wide pattern of change in the englacial subglacial drainage system of haut glacier d arolla during the ablation seasons of 1990 and 1991 analysis of breakthrough curve characteristics indicate that over the course of a melt season a system of major channels developed by headward growth at the expense of a hydraulically inefficient distributed system by the end of the melt season this channel system extended at least 3 3 km from the snout of the 4 km long glacier and drained the bulk of supraglacially derived meltwater passing through the glacier the upper limit of the channel system closely followed the retreating snowline up glacier rates of headward channel growth reached c 65 m d 1 although these rates decreased in the upper 1 km of the glacier where snowline retreat exposed a patchy firn aquifer it appears that the removal of snow with its high albedo and significant water storage capacity from the glacier surface resulted in a dramatic increase in the volume of runoff into moulins and in the peakedness of daily runoff cycles this induced transient high water pressures within the distributed drainage system which caused it to evolve rapidly into a channelised system it is therefore likely that at a local scale channel growth occurred down glacier from moulins and that the overall up glacier directed pattern of channel formation was caused by the retreating snowline exposing new moulins and crevasses to inputs of ice derived meltwater damping of diurnal melt inputs by storage in the firm aquifer accounts for the slowing of channel growth in the upper glacier 1998 john wiley sons ltd

paleomagnetism of the samail ophiolite oman 1 the sheeted dike complex at ibra we have studied the rock magnetism and paleomagnetism of 200 oriented samples from the middle cretaceous sheeted dike sequence of the samail ophiolite oman the samples are from 28 sites spanning a cross strike distance of 30 km most of the dikes have undergone green schist metamorphism the natural remanent magnetization nrm of the samples is about 1 a m and qn is also near 1 thermal and alternating field demagnetization treatment resolves both normal north and reversed south polarities about one third of the samples have low median destructive fields mdf less than 100 oe 7 96 103 a turn m these low mdf samples have scattered directions and are classified as undetermined polarities u hysteresis measurements show pseudo single domain carriers predominate in all samples although the low mdf samples are suggested to have the largest grains in the samples studied thermomagnetic curves show both magnetite and minor maghemite thermal demagnetization and microscopic study reveals that hematite is abundant and is the carrier of the r remanence in addition several dikes exhibit both n and r polarities these facts coupled with the degree of metamorphism indicate that part of the remanence is secondary and could be due to hydrothermal metamorphism below the seafloor we suggest that the n polarity is primary and resides in exsolved magnetite while the r polarity is secondary and resides primarily in metamorphic origin hematite several short r events observed in the albian through cenomanian magnetostratigraphic record are candidates for the r event in the ophiolite if the r polarity originated near the spreading center alternately nonreproducible self reversal is another possible origin for the r polarity regardless of whether the reversal originated at the spreading center secondary magnetization in the dikes considerably increases the directional dispersion another major factor affecting dispersion is viscous remanent magnetization vrm in the larger magnetite grains this extreme dispersion disallows the samail ophiolite dike layer as a significant source for marine magnetic anomalies regardless of the strength of the nrm or the value of q the stable n and r directions yield a paleomagnetic pole which is far sided suggesting northward movement of the ophiolite however the paleomagnetic pole is not as far sided as the contemporaneous africa pole which suggests a component of north south closure between the ophiolite and africa prior to northward movement

mesozoic palaeomagnetism of the transdanubian central mountains and its tectonic implications abstract the mesozoic apparent polar wandering apw of the transdanubian central mountains determined from thermally isolated natural remanences at 13 localities shows a remarkable similarity to the mesozoic apw of africa in that they both exhibit the same loop like movement moreover the difference between the two apw s can practically be eliminated by a 35 clockwise rotation of the palaeodeclinations it is concluded therefore that the region of the transdanubian central mountains was part of the african adriatic plate up to some time in the cenozoic when it moved to its present position resulting in a 35 anticlockwise rotation relative to africa

paleomagnetic results from mio pliocene marine sedimentary series in crete abstract paleomagnetic measurements have been conducted on mio pliocene marine sedimentary series from crete in order to detect any eventual rotation of this island the results obtained from 14 stable sites of tortonian age 7 m y yield a paleomagnetic pole not significantly different from either the european or the african ones showing that crete has not undergone any significant rotation since that epoch

effect of stair step and piecewise linear topography on internal wave propagation in a geophysical flow model 1 the paper describes the effect of a stair step representation of bottom topography common in most numerical models on the propagation of internal waves in a geophysical flow an analytical solution was used to predict the effect of stair step and piecewise linear representations of topography on the reflection and transmission of internal waves the estuary lake and coastal model elcom was used to simulate the transmission of a train of small amplitude internal gravity waves propagated along a variable depth rectangular channel containing a linearly stratified fluid the effect of the different obstacle approximations was examined in terms of the interference of the resulting wave number content and hence the associated reflection coefficients which could be directly compared to the analytical theory it was shown that for gaussian obstacles of varying lengths and heights the full bottom cells and partial bottom cells solutions from elcom agree with the stair step and piecewise linear solutions from the theory respectively it was shown that when gaussian obstacles with weak slopes are represented by stair steps an aliasing that is similar to that in discrete fourier transform can occur resulting in reflection coefficients that are much higher than the exact solution on the other hand piecewise linear approximations produce significantly attenuated aliasing an immersed boundary technique that enforces a no flux condition at the actual sloping bottom similar to that of the analytical solution is found not to produce better numerical results

palaeomagnetism of permo triassic rocks from northern slovenia yugoslavia and the eastern margin of the adriatic plate abstract in northern slovenia yugoslavia 15 e 46 n 41 sites of permo triassic red sandstones and volcanic rocks have been sampled for a palaeomagnetic study the rock units are situated either in the southern alps or in the transition zone between the southern alps and the dinarides more than half of the sampled sites revealed that the primary remanence was seriously affected by partial or entire magnetic overprint in connection with the alpine orogeny this was manifested by either too steep inclinations or too weak or inconsistent and unstable remanence only fourteen sites revealed the typical flat inclinations of permo triassic rocks a group of six sites in northwestern slovenia west of ljubljana gave a remanence direction n 6 r 5 431 d 151 4 i 11 4 k 8 8 95 19 3 which is in agreement with the mean permian remanence direction of the bolzano rhyolites in the italian part of the southern alps d 148 i 20 after zijderveld and van der voo 1973 indicating that this zone is still part of the adriatic plate however a group of eight sites in northeastern slovenia east of ljubljana has a remanence direction n 8 r 6 991 d 225 9 i 15 0 k 6 9 95 18 8 which is more in agreement with the central european permo triassic direction of remanence d 204 i 14 it is therefore concluded that the eastern margin of the adriatic plate crosses the region of ljubljana in an approximately north south direction

proglacial erosion rates and processes in a glacierized catchment in the swiss alps in the swiss alps climatic changes have not only caused glacier retreat but also likely increased sedimentation downstream of glaciers this material either originates from below the glacier or from periglacial environments exposed as glaciers retreat and often consist of easily erodible sediment griesgletscher s catchment in the swiss alps was examined to quantify erosion in theproglacial area possible hydrological drivers and contributions of the sub and periglacial sources digital elevation models created from annual aerial photographs were subtracted to determine annual volume changes in the proglacial area from 1986 to 2014 these data show a strong increase in proglacial erosion in the decade prior to 2012 coincident with increasing proglacial area size however examination of the gradient between discharge and sediment evacuation and the modeled sediment transport could suggest that the proglacial area began to stabilize and sediment supply is limited the large influx of sediment into the proglacial reservoir which is roughly 2 5 times greater than the amount of sediment eroded from the proglacial area demonstrates the importance of subglacial erosion to the catchment s sediment budget although far more sediment originates subglacially erosion rates in the proglacial area are over 50 times greater than the rest of the catchment in turn both sub and periglacial processes in addition to constraining sediment supply must be considered forassessing future sediment dynamics as glacier area shrinks and proglacial areas grow

a geological and paleomagnetic study of the hyblean volcanic rocks sicily abstract the geological and paleomagnetic study of the hyblean volcanic rocks in southeastern sicily permits the following conclusions 1 1 the upper cretaceous volcanics are considerably more extensive than earlier studies indicated they stretch from north of augusta to the vicinity of siracusa their magnetization is identical to that of the better known outcrops around capo passero of the two new age dates reported here one is younger than any so far reported 2 2 the upper tortonian flows are normally magnetized suggesting a correlation of the carlentini formation with magnetic interval 7 the flows at the top of the tellaro formation are also normally magnetized and are tentatively correlated with the carlentini formation flows shorter reversed intervals within interval 7 may be represented by two less well dated flows 3 3 the lowest pliocene flows have an adequate stratigraphie control and their magnetization is consistent with the extrusion of the pillow lavas during the mammoth event the militello flow sequence together with the francofonte flows appear by indirect argument to lie within the oldest reversed interval i e pre kaena of the matuyama epoch the individual flows in which both normal and reversed directions have been found cannot be assigned positions in magneto stratigraphie scale 4 4 the geomagnetic pole positions are consistent with that of the african plate during the cretaceous and a european plate location during both pliocene and miocene time the pole positions are upper cretaceous 212 3 e 69 3 n upper miocene 200 9 e 82 1 n pliocene 339 3 e 85 9 n

the relationship between subglacial water pressure and velocity of findelengletscher switzerland during its advance and retreat findelengletscher switzerland advanced about 250 m between 1979 and 1985 and retreated thereafter subglacial water pressure surface velocity and surface strain rate were determined at several sites the measurements were made early in the melt seasons of 1980 1982 1985 and 1994 and in the autumn of 1983 and the winter of 1984 changes of surface geometry were assessed from aerial photographs the estimated basal shear stress changed little between 1982 and 1994 nevertheless large changes in the relationship of subglacial water pressure and surface velocity were observed which cannot be reconciled with the most commonly used sliding law unless it is modified substantially consideration of possible reasons indicales that a change in the subglacial drainage system occurred probably involving a change in the degree of cavity interconnection isolated cavities damp the variations in sliding velocity that normally result from changes in water pressure because the pressure in isolated cavities decreases as the sliding speed increases in contrast by transmitting water pressure fluctuations to a larger area of the bed interconnected cavities amplify the effect of water pressure fluctuations on sliding speed thus we suggest that an observed decrease in velocity for a given water pressure between 1982 and 1994 was a consequence of a decrease in the interconnectedness of the subglacial cavity system

estimating rates of basal motion and internal ice deformation from continuous tilt measurements over a two year period continuous measurements of temporal changes in tilt conducted with a string of tilt meters in a borehole on unteraargletscher bernese alps switzerland have been used to estimate the basal motion component this estimation is based on a comparison of the measurements with synthetic tilt curves computed using a parameterization of a simplified flow field the best agreement is found for a ratio of basal motion to forward motion due to ice deformation slip ratio equal to about 1 2 measured tilt curves exhibit a number of different transient features while an overall increase in tilt angle is observed at every tilt meter location two of the sensors recorded anomalous tilt behaviour these anomalies are characterized by sudden and drastic variations in tilt a particularly intriguing example of such short term tilt variations was recorded with a tilt meter positioned 40 m above the bed during the 1997 summer melt season

ionospheric gravity waves detected offshore hawaii after tsunamis 1 on board satellites techniques provide global coverage and could play an important role in the continuous oceanic survey to prevent the damage produced by powerful tsunamis we report here new ionospheric observations related to three significant transpacific tsunami events triggered by the 2006 kuril earthquake the 2009 samoa earthquake and the 2010 chile earthquake total electron content tec variations extracted from data recorded by a dense global positioning system gps network based in hawaii show ionospheric disturbances within the hours following the tsunami wave passage at sea level for each event we observe ionospheric gravity waves propagating with velocity direction and arrival time coherent with the tsunami the tsunamigenic signature in the ionosphere is also compared to in situ sea level measurements these observations provide new examples of the sensitivity of the ionosphere to tsunamigenic gravity waves and confirm that ionospheric monitoring by gps can provide complementary information on tsunami propagation

high resolution measurements of spatial and temporal variations in surface velocities of unteraargletscher bernese alps switzerland data from automated in situ measurements of surface displacements on unteraargletscher bernese alps switzerland made a few times a day from late june until late october 1998 are presented two short term speed up events were observed and partial evidence for a third motion event was seen short term motion events are thus not limited to the start of the melting season strong correlation between the timing of the motion events and periods of heavy rainfall in conjunction with the large size of the area of the glacier which becomes activated during the events both point towards an external triggering mechanism in the time periods between two motion events surface velocities do not vary significantly with time after a motion event surface velocities do not return to previous values suggesting that the events have a lasting effect on the structure of the subglacial drainage system

paleomagnetism in northwestern bulgaria geological implications of widespread remagnetization abstract two different paleomagnetic directions have been obtained in several formations in northwestern bulgaria one of them found only in upper permian lower triassic red sandstones is very likely a primary magnetization a secondary magnetization of eocene age appears as either pre syn or post folding depending on the site the identification of the timing of remagnetization with respect to folding allows us to distinguish areas among the first deformed during tertiary tectonics within each superimposed structural unit of the west balkan the deformation spread from south to north the boundary between the srednogorie and balkan zones appears to be a major tectonic structure in bulgaria the balkan likely underwent a clockwise rotation relative to stable europe since the beginning of the main middle eocene orogenesis

three dimensional waveform modeling of ionospheric signature induced by the 2004 sumatra tsunami 1 the sumatra december 26th 2004 tsunami produced internal gravity waves in the neutral atmosphere and large disturbances in the overlying ionospheric plasma to corroborate the tsunamigenic hypothesis of these perturbations we reproduce with a 3d numerical modeling of the ocean atmosphere ionosphere coupling the tsunami signature in the total electron content tec data measured by the jason 1 and topex poseidon satellite altimeters the agreement between the observed and synthetic tec shows that ionospheric remote sensing can provide new tools for offshore tsunami detection and monitoring

lower jurassic palaeomagnetic results from yorkshire england and their implications palaeomagnetic study of middle liassic siltstones shows a stable magnetization with a mean direction of d 12 3 i 64 6 n 60 k 26 95 3 9 corresponding to a palaeomagnetic pole at 79 8 n 125 6 e similar to that for southern germany and confirming predictions based on palaeogeographic reconstructions using north american data sideritic concretions of lower liassic age show a higher magnetic stability with a mean direction of d 12 6 i 61 4 n 125 k 50 95 1 8 which is not significantly different from the siltstones this confirms the sedimentological evidence that suggests that such concretions grew very shortly after deposition i e within the liassic and suggests that similar concretions of other ages could thus be used for palaeomagnetic studies although the liassic palaeomagnetic pole 76 9 n 134 7 e based on this work appears valid it is still not possible to evaluate a sensible mesozoic polar wandering curve for the north atlantic bordering continents

paleomagnetic implications on the evolution of the tethys belt from the atlantic ocean to the pamirs since the triassic abstract we first re examined the apparent polar wander curves for stable eurasia and africa since the triassic these curves were then combined together with curves of north and south america according to the kinematics of the atlantic ocean and a synthetic polar wander curve was given then most of the paleomagnetic results from the tethys mobile belt from the atlantic to the pamirs were analysed several groups of plates microplates and blocks can be seen first relatively stable regions like maghreb and sicily which have not moved much then we have a group formed by iberia sardinia italy and to a lesser extent corsica and the western and central alps for these blocks movements are anticlockwise rotations chiefly driven by the anticlockwise rotation of africa but they are sometimes stronger to the east a major change takes place the north of the aegean sea and the ionian zone are clockwise rotated and these rotations are recent oligocene miocene for the first part pliocene to the present for the second part a major problem arises in turkey caucasus and iran paleomagnetic results indicate a position far to the south of eurasia and at the same time geological evidence is in favour of a position close to eurasia we discuss these discrepancies

paleomagnetism and potassium argon age of the messejana dike portugal and spain angular limitation to the rotation of the iberian peninsula since the middle jurassic abstract a paleomagnetic and potassium argon dating investigation has been carried out on a 530 km long dike system which transects the western iberian peninsula in a northeasterly direction the k ar age determinations were made on mineral separates exclusively they range between 160 and 200 ma and the authors suppose that this reflects the actual time interval of the intrusion in accord with previous results the paleomagnetic pole derived from 12 sites regularly distributed along the dike 71 n 236 e coincides well with other mesozoic paleomagnetic poles from the western africa a contemporaneous pole from stable europe is tentatively deduced from african and north american late triassic early jurassic poles using different reconstruction models around the north atlantic ocean the divergence between this pole and the iberian pole corresponds to the result obtained for permian poles

polythermal glacier hydrology a review 1 the manner by which meltwater drains through a glacier is critical to ice dynamics runoff characteristics and water quality however much of the contemporary knowledge relating to glacier hydrology has been based upon and conditioned by understanding gleaned from temperate valley glaciers globally a significant proportion of glaciers and ice sheets exhibit nontemperate thermal regimes the recent growing concern over the future response of polar glaciers and ice sheets to forecasts of a warming climate and lengthening summer melt season necessitates recognition of the hydrological processes in these nontemperate ice masses it is therefore timely to present an accessible review of the scientific progress in glacial hydrology where nontemperate conditions are dominant this review provides an appraisal of the glaciological literature from nontemperate glaciers examining supraglacial englacial and subglacial environments in sequence and their role in hydrological processes within glacierized catchments in particular the variability and complexity in glacier thermal regimes are discussed illustrating how a unified model of drainage architecture is likely to remain elusive due to structural controls on the presence of water cold ice near glacier surfaces may reduce meltwater flux into the glacier interior but observations suggest that the transient thermal layer of near surface ice holds a hydrological role as a depth limited aquifer englacial flowpaths may arise from the deep incision of supraglacial streams or the propagation of hydrofractures forms which are readily able to handle varied meltwater discharge or act as locations for water storage and result in spatially discrete delivery of water to the subglacial environment the influence of such drainage routes on seasonal meltwater release is explored with reference to summer season upwellings and winter icing formation moreover clear analogies emerge between nontemperate valley glacier and ice sheet hydrology the discussion of which indicates how persistent reassessment of our conceptualization of glacier drainage systems is required there is a clear emphasis that continued integrated endeavors focused on process glaciology at nontemperate glaciers are a scientific imperative to augmenting the existing body of research centered on ice mass hydrology

measurements of ice deformation at the confluence area of unteraargletscher bernese alps switzerland an experimental study of ice deformation at the confluence area of unteraargletscher bernese alps switzerland has been carried out surface velocities were measured by repeatedly surveying stakes and with the use of remote sensing methods the variation of the vertical strain rates with depth was measured in boreholes the confluence center line is subjected to longitudinal horizontal extension which is exceeded in magnitude by a concomitant transverse compression vertical strain rates change from positive extension at the surface to negative compression in the lowest layers of the glacier

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

no significant post eocene rotation of the moesian platform and rhodope bulgaria implications for the kinematic evolution of the carpathian and aegean arcs abstract the region located between the carpathian balkan and aegean arcs the moesian platform and bulgarian rhodope is generally assumed to have been stably attached to the east european craton during the cenozoic evolution of these arcs the kinematic evolution of this region is however poorly constrained by paleomagnetic analysis in this paper we provide new paleomagnetic data 800 volcanic and sedimentary samples from 12 localities showing no significant post eocene rotation of the moesian platform and rhodope with respect to eurasia therefore confirming the stability of this region we compare this result to a provided review of paleomagnetic data from the south carpathians tisza block and the aegean region the tisza block underwent 68 4 16 7 of middle miocene 15 10 ma clockwise rotation with respect to the moesian platform in line with previous rotation estimates based on structural geology the stability of the moesian platform during middle miocene eastward emplacement of the tisza block into the carpathian back arc supports dextral shear along the southern carpathians recorded by 13 6 ma clockwise strike slip related rotations in foreland deposits the new reference direction for the moesian platform and rhodope allows accurate quantification of the rotation difference with the west aegean domain at 38 0 7 2 occurring between 15 and 8 ma to accommodate this rotation we propose that the pivot point of the west aegean rotation was located approximately in the middle of the rotating domain rather than at the northern tip as previously proposed this new scenario predicts less extension southeast of the pivot point in good agreement with estimates from aegean structural geology northwest of the pivot point the model requires contraction or extrusion that can be accommodated by the coeval motion of the tisza block around the northwestern edge of the moesian platform

the propagation of tsunami generated acoustic gravity waves in the atmosphere abstracttsunami generated acoustic gravity waves have been observed to propagate in the atmosphere up to the ionosphere where they have an impact on the total electron content the authors simulate numerically the propagation of two dimensional linear acoustic gravity waves in an atmosphere with vertically varying stratification and horizontal background winds the authors goal is to compare the difference in how much energy reaches the lower ionosphere up to an altitude of 180 km where the atmosphere is assumed to be anelastic or fully compressible the authors consider three specific atmospheric cases a uniformly stratified atmosphere without winds an idealized case with a wind jet and a realistic case with an atmospheric profile corresponding to the 2004 sumatra tsunami results show that for the last two cases the number and height of turning points are different for the anelastic and compressible assumptions and the net result is that compressibility enhances the total transmission of energy

hydraulic and mechanical properties of glacial sediments beneath unteraargletscher switzerland implications for glacier basal motion the force on a ploughmeter and subglacial water pressure have been measured in the same borehole at unteraargletscher switzerland in order to investigate ice sediment coupling and the motion at the base of a soft bedded glacier a strong inverse correlation of the recorded pressure and force fluctuations in conjunction with a significant time lag between the two signals suggests that pore water pressures directly affect the strength of the subglacial sediment the lag is interpreted to reflect the time required for the water pressure wave to propagate through the pores of the sediment to the depth of the ploughmeter analysis of the propagation velocity of this pressure wave yielded an estimate of the hydraulic diffusivity a key parameter necessary to characterize transient pore water flow furthermore the inferred inverse relationship between pore water pressure and sediment strength implies that coulomb plastic deformation is an appropriate rheological model for the sediment underlying unteraargletscher however the sediment strength as derived from the ploughmeter data was found to be one order of magnitude smaller than that calculated for a coulomb frictional material using the water pressure measurements this significant discrepancy might result from pore water pressures in excess of hydrostatic down glacier from the ploughmeter as the ploughmeter is dragged through the sediment sediment is compressed if the rate of this compression is large relative to the rate at which pore water can drain away excess pore water pressures will develop that have the potential to weaken the sediment the same process could lead to highly fluid sediment down glacier from clasts that protrude into the glacier sole and thus would otherwise provide the roughness to couple the glacier to its bed iverson 1999 rapidly sliding glaciers overlying sediments might therefore move predominantly by ploughing which tends to focus basal motion near the glacier sole rather than at depth in the bed

identification of erosional mechanisms during past glaciations based on a bedrock surface model of the central european alps the bedrock topography beneath the quaternary cover provides an important archive for the identification of erosional processes during past glaciations here we combined stratigraphic investigations of more than 40 000 boreholes with published data to generate a bedrock topography model for the entire plateau north of the swiss alps including the valleys within the mountain belt we compared the bedrock map with data about the pattern of the erosional resistance of alpine rocks to identify the controls of the lithologic architecture on the location of overdeepenings we additionally used the bedrock topography map as a basis to calculate the erosional potential of the alpine glaciers which was related to the thickness of the lgm ice we used these calculations to interpret how glaciers with support by subglacial meltwater under pressure might have shaped the bedrock topography of the alps we found that the erosional resistance of the bedrock lithology mainly explains where overdeepenings in the alpine valleys and the plateau occur in particular in the alpine valleys the locations of overdeepenings largely overlap with areas where the underlying bedrock has a low erosional resistance or where it was shattered by faults we also found that the assignment of two end member scenarios of erosion related to glacial abrasion plucking in the alpine valleys and dissection by subglacial meltwater in the plateau may be adequate to explain the pattern of overdeepenings in the alpine realm this most likely points to the topographic controls on glacial scouring in the alps the flow of lgm and previous glaciers were constrained by valley flanks while ice flow was mostly divergent on the plateau where valley borders are absent we suggest that these differences in landscape conditioning might have contributed to the contrasts in the formation of overdeepenings in the alpine valleys and the plateau

the prediction of hillslope flow paths for distributed hydrological modelling using digital terrain models the accuracy of the predictions of distributed hydrological models must depend in part on the proper specification of flow pathways this paper examines some of the problems of deriving flow pathways from raster digital terrain data in the context of hydrological predictions using topmodel distributed moisture status is predicted in topmodel on the basis of spatial indices that depend on flow path definition the sensitivity of this index to flow path algorithm and grid size is examined for the case where the surface topography is a good indicator of local hydraulic gradients a strategy for the case where downslope subsurface flow pathways may deviate from those indicated by the surface topography is described with an example application

quantitative analysis of land surface topography land surface topography significantly affects the processes of runoff and erosion a system which determines slope aspect and curvature in both the down slope and across slope directions is developed for an altitude matrix also the upslope drainage area and maximum drainage distance are determined for every point within the altitude matrix a fortran 66 program performs the analysis

the ice thickness distribution of unteraargletscher switzerland results from 15 years of work on glacier bed mapping by radio echo soundings on finsteraar lauteraar and unteraargletscher switzerland are summarized and a new and greatly improved map of the ice thickness distribution presented in contrast to the tongue of unteraargletscher its two main tributaries lauteraar and finsteraar are both deep and narrow and ice thickness determination depends on the detection of more than just the primary reflection migrating the data led to considerably improved bed determination wherever possible additional information on ice thicknesses gained from numerous hot water drillings to the glacier bed is used as an independent verification of the results of the radar measurements and a fair agreement is found

changes in geometry and subglacial drainage of midre lovenbreen svalbard determined from digital elevation models digital elevation models dems of the bed and surface of the polythermal midre lovenbreen svalbard are used to identify changes in glacier geometry between 1977 and 1995 the calculated mean annual mass balance 0 61 m water equivalent w e a 1 is more negative than that derived from field measurements 0 35 m w e a 1 although the error associated with this value 0 7 m a 1 suggests that the difference may be accounted for by errors however similar discrepancies between dem based and field based measurements of mass balance have been reported elsewhere in svalbard although errors may be responsible patterns of surface elevation change may also be explained in terms of patterns of ablation accumulation and dynamics the theoretical structure of the subglacial drainage system is modelled using different assumptions about subglacial water pressure in 1977 and 1995 these reconstructions are compared with the observed positions of proglacial outlet streams decreasing subglacial water pressure results in a decrease in the influence of surface morphology and an increase in the role of the bed topography on drainage routing which generally leads to more dispersed drainage long term changes in the position of proglacial outlet streams occur as a result of changes in glacier geometry but short term changes may also occur in response to early season water pressures controlled by meteorological and hydrological conditions copyright 2003 john wiley sons ltd

geomagnetic dependence of ionospheric disturbances induced by tsunamigenic internal gravity waves summary a series of ionospheric anomalies following the sumatra tsunami has been recently reported in the literature these anomalies show the signature in the ionosphere of tsunami generated internal gravity waves igw propagating in the neutral atmosphere over the ocean all these anomalies observed in the total electron content tec measured by gps or altimeters show geographical heterogeneity in the perturbed tec amplitude and suggest a dependence on geomagnetic latitude this latitudinal dependence has been taken into account in the previous 3 d modelling used for the interpretation of the tec topex and jason data here we present an accurate description of the ocean atmosphere ionosphere coupling method and focus on the properties of the propagation of tsunamigenic igw in the neutral atmosphere and their interaction with the ionospheric plasma the analytical dependence on the geomagnetic field in the neutral plasma coupling discussed in detail and quantitative modelling is used to describe the propagation of a simple tsunami wave at the global scale what emphasize the role of geomagnetic field within the neutral plasma coupling at the equatorial and mid latitude regions the results presented here in terms of electron density and tec variations show a strong geometric dependance involving the magnetic field inclination and the propagative direction of the tsunami if the strongest electron density and tec perturbations are located around 15 0 and 15 north the structure and amplitude of the modelled perturbation changes in the two