timing of intraplate deformation northeastern indian ocean abstract seismic stratigraphy and dsdp and odp drilling have demonstrated that two unconformities of early eocene and latest miocene age can be traced over much of the northeastern indian ocean the eocene event was a major hiatus in sedimentation following collision of india with asia and was the time of termination of deposition of a continental rise off the east side of india and the initiation of proximal bengal fan deposition the miocene event was the onset of north south compression in the indian plate during rapid uplift in tibet and the himalayas

contribution of small glaciers to global sea level observed long term changes in glacier volume and hydrometeorological mass balance models yield data on the transfer of water from glaciers excluding those in greenland and antarctica to the oceans the average observed volume change for the period 1900 to 1961 is scaled to a global average by use of the seasonal amplitude of the mass balance these data are used to calibrate the models to estimate the changing contribution of glaciers to sea level for the period 1884 to 1975 although the error band is large these glaciers appear to account for a third to half of observed rise in sea level approximately that fraction not explained by thermal expansion of the ocean

evidence for relative motions between the indian and australian plates during the last 20 m y from plate tectonic reconstructions implications for the deformation of the indo australian plate we use plate tectonic reconstructions to establish whether motions between india and australia occurred since chron 18 43 ma we test the africa antarctica australia india plate circuit closure at chrons 5 10 ma 6 21 ma and 13 36 ma using a compilation of magnetic anomalies and fracture zone traces from the southeast southwest central indian and the carlsberg ridges additional reconstructions at chrons 23 55 ma and 26 61 ma are used to estimate the overall motion between india and australia relative motions between the indian and australian plates are estimated using the plate circuit india africa australia a new statistical approach based on spherical regression analyses is used to assess the uncertainty of the best fitting finite rotations from the uncertainties in the data the uncertainty in a rotation is described by a covariance matrix directly related to the geometry of the reconstructed plate boundary to the distribution and estimated errors of the data points along it our parameterization of the rotations allows for simple combination of the rotation uncertainties along a plate circuit path results for chron 5 are remarkably consistent with present day kinematics in the indian ocean except that the arabian and indian plates are found to be separate plates comparisons of the motions between the indian and african plates across the carlsberg ridge with that between the australian and african plates across the central indian ridge evidence a significant counterclockwise rotation of the australian plate relative to the indian plate about a pole located in the central indian basin the determinations are consistent for chrons 26 13 6 and 5 determination at chron 23 is different but questionable due to the small number of available data we propose two alternative solutions that both predict convergence within the wharton and central indian basins and extension in the vicinity of the chagos laccadive ridge the first solution assumes that all the deformation in the equatorial indian ocean started 7 ma ago as found by ocean drilling program leg 116 hence all the determinations at different times represent the total motion between india and australia the averaged india australia euler vector chrons 5 6 13 and 26 11 1 s 78 0 3 54 lies within the central indian basin and yields a n s contraction of 46 52 km at 85 and 80 63 km at 90 however the difference of the india australia euler vectors at chrons 5 and 6 suggests that the india australia convergence started between 10 and 21 ma following the continent continent collision of india with asia in the early miocene the second averaged solution chrons 6 13 and 26 5 2 s 74 3 e 5 93 predicts a total n s contraction of 123 73 km at 85 e and 178 91 km at 90 e both models are compatible with the deformation pattern observed in the equatorial indian ocean

reconstruction of the central indian ocean abstract sixteen plate tectonic reconstructions are presented illustrating the development of the central indian ocean from the latest cretaceous anomaly 29 to the present the history of seafloor spreading in the indian ocean can be divided into five distinct tectonic epochs 1 1 latest cretaceous early paleocene a29 a27 2 2 middle paleocene early eocene a27 a22 3 3 middle eocene late eocene a22 a18 4 4 late eocene early miocene a18 a8 and 5 5 early miocene recent a8 a5 during each of these tectonic epochs subtle changes took place in the directions and rates of spreading along the central southeast and southwest indian ridges the most dramatic changes in plate motion occurred between a21 and a18 time due to the collision of india and eurasia

mantle dynamics uplift of the tibetan plateau and the indian monsoon convective removal of lower lithosphere beneath the tibetan plateau can account for a rapid increase in the mean elevation of the tibetan plateau of 1000 m or more in a few million years such uplift seems to be required by abrupt tectonic and environmental changes in asia and the indian ocean in late cenozoic time the composition of basaltic volcanism in northern tibet which apparently began at about 13 ma implies melting of lithosphere not asthenosphere the most plausible mechanism for rapid heat transfer to the midlithosphere is by convective removal of deeper lithosphere and its replacement by hotter asthenosphere the initiation of normal faulting in tibet at about 8 3 ma suggests that the plateau underwent an appreciable increase in elevation at that time an increase due solely to the isostatic response to crustal thickening caused by india s penetration into eurasia should have been slow and could not have triggered normal faulting another process such as removal of relatively cold dense lower lithosphere must have caused a supplemental uplift of the surface folding and faulting of the indo australian plate south of india the most prominent oceanic intraplate deformation on earth began between about 7 5 and 8 ma and indicates an increased north south compressional stress within the indo australian plate a tibetan uplift of only 1000 m if the result of removal of lower lithosphere should have increased the compressional stress that the plateau applies to india and that resists india s northward movement from an amount too small to fold oceanic lithosphere to one sufficient to do so the climate of the equatorial indian ocean and southern asia changed at about 6 9 ma monsoonal winds apparently strengthened northern pakistan became more arid but weathering of rock in the eastern himalaya apparently increased because of its high altitude and lateral extent the tibetan plateau provides a heat source at midlatitudes that should oppose classical symmetric hadley circulation between the equator and temperate latitudes and that should help to drive an essentially opposite circulation characteristic of summer monsoons for the simple case of axisymmetric heating no dependence on longitude of an atmosphere without dissipation theoretical analyses by hou lindzen and plumb show that an axisymmetric heat source displaced from the equator can drive a much stronger meridianal monsoonlike circulation than such a source centered on the equator but only if heating exceeds a threshold whose level increases with the latitude of the heat source because heating of the atmosphere over tibet should increase monotonically with elevation of the plateau a modest uplift 1000 2500 m of tibet already of substantial extent and height might have been sufficient to exceed a threshold necessary for a strong monsoon the virtual simultaneity of these phenomena suggests that uplift was rapid approximately 1000 m to 2500 m in a few million years moreover nearly simultaneously with the late miocene strengthening of the monsoon the calcite compensation depth in the oceans dropped plants using the relatively efficient c4 pathway for photosynthesis evolved rapidly and atmospheric co2 seems to have decreased suggesting causal relationships and positive feedbacks among these phenomena both a supplemental uplift of the himalaya the southern edge of tibet and a strengthened monsoon may have accelerated erosion and weathering of silicate rock in the himalaya that in turn enhanced extraction of co2 from the atmosphere thus these correlations offer some support for links between plateau uplift a downdrawing of co2 from the atmosphere and global climate change as proposed by raymo ruddiman and froehlich mantle dynamics beneath mountain belts not only may profoundly affect tectonic processes near and far from the belts but might also play an important role in altering regional and global climates

investigation of a vine matthews magnetic lineation from a submersible the source and character of marine magnetic anomalies we report here the first attempt to map directly the boundary of a vine matthews magnetic stripe on the seafloor our objectives are to study the processes of oceanic crustal accretion as recorded in the reversal transition zone and to investigate the formation of the magnetic source of vine matthews magnetic anomalies our deep tow and alvin based magnetic studies focus on the matuyama brunhes reversal transition on the flanks of the east pacific rise near 21 n while the sea level magnetic anomalies are less than average in clarity for the east pacific rise a three dimensional inversion of deep tow data reveals a sharp strike linear polarity transition less than 1 8 km wide macdonald et al 1980a these measurements have been augmented by mounting a vertical magnetic gradiometer on alvin and making 280 reliable polarity determinations along and across the polarity transition zone even on long traverses across both sides of the boundary we find that nearly every magnetic target has the correct polarity i e the same polarity as the regional magnetic lineation this homogeneity in polarity of the magnetic lineations is surprising the magnetic polarity transition in the outcropping volcanic section is sharp and linear along strike delineated in some cases by a clear geologic contact of opposing flow fronts of different ages several weakly magnetized outcrops mapped within the transition zone may have erupted during the time in which the geomagnetic field was reversing the reversal boundary mapped on the seafloor from alvin is displaced 250 m to 500 m nw away from the spreading axis relative to the position of the average boundary as derived from inversion of the deep tow and sea level magnetic data this offset provides a means for estimating the spillover of lava flows away from the spreading axis during the time the crust was formed the combination of deep tow and alvin measurements suggests that circa 0 7 m y ago the crustal accretion zone magnetized volcanic intrusive and plutonic rocks was 2000 2800 m wide while the zone of recent volcanism alone was only 1000 2000 m wide the determination for the most recent reversal agrees well with submersible observations at the present spreading center where the zone of recent volcanism neovolcanic zone varies between 600 and 2000 m in width this very orderly picture for the formation of magnetic lineations and crustal accretion processes appears to conflict with complex deep sea drilling project dsdp magnetic results from the atlantic we suggest that the crustal generating processes and resulting magnetic structure vary significantly with spreading rate on the slow spreading mid atlantic ridge major episodes of volcanism are likely to be infrequent 104 years the magma chamber may be non steady state and the neovolcanic zone shifts or varies in width considerably this sporadic start and stop spreading process will contribute to a highly heterogeneous and complex crustal and magnetic structure as seen in dsdp holes in addition significant faulting and tilting may disrupt slow spreading crust for intermediate to fast spreading centers more frequent volcanism 50 600 years a nearly steady state magma chamber and a narrow stable neovolcanic zone will create a less complex magnetic and crustal structure both as seen from alvin and as inferred from clear sea level magnetic anomalies in the pacific

using landsat 5 thematic mapper and digital elevation data to determine the net radiation field of a mountain glacier abstract an accurate evaluation of glacier energy balance requires a precise knowledge of surface cover albedo and emittance usually these values are acquired from field measurements however the microclimatological effects in mountainous terrain greatly limit the potential for spatial extrapolation of such a set of values this study overcomes the problem by using the upward radiance values registered on landsat 5 thematic mapper tm images and information on the geometry of ter terrain extracted from a digital elevation model dem studies were performed in the athabasca glacier basin one of the major glacier outlets of the columbia icefield in the canadian rocky mountains the methodology is composed first of an automated procedure for the physiographic description of the glacierized basin cover type elevation slope aspect horizon profiles sky view factor and the level of enclosing topography in order to calculate the effects of topography on the radiation balance for each 30 m pixel because glacier surface covers usually have high reflective behaviors or distinct emission patterns this study puts special emphasis on modelling the amount of terrain reflected or terrain emitted radiation received on a particular surface second the topographic correction is applied to values of irradiance computed using the lowtran 6 code a spectrally based radiative transfer model and atmospheric radiosonde measurements of the vertical temperature air pressure and relative humidity profiles the measured upward radiance values from tm corrected for path effects are used to calculate surface cover albedo and brightness temperature third the daily net radiation field for snow and ice covers is computed to illustrate the contribution of the estimated surface radiative parameters to the glacier snow and ice melt analysis the resultsshow that the irradiance values are accurately modelled within 10 of the radiattion values acquired from a field pyranometer the calculated glacial surface cover reflectance and albedo values compare favorably to published information whereas the measured surface brightness temperature is well within the expected range of values

continental collision slowing due to viscous mantle lithosphere rather than topography the rate of india s convergence with eurasia has decreased exponentially since their collision which suggests that the deforming continental lithosphere creates a type of viscous resistance that affects plate motion irrespective of how topography evolved the forces that control plate motion are fundamental to plate tectonic theory it has generally been thought that deforming and thickening continental crust is responsible for slowing down the convergence between two continental plates marin clark now shows however that the rate of penetration of the indian subcontinent into eurasia has decreased exponentially since the plates collided which suggests that contractional strain across tibet has been constant throughout the collision she infers that this reflects deformation of the mantle lithosphere and that under conditions of constant stress and strength the deforming continental lithosphere creates viscous resistance that affects plate motion irrespective of how topography evolved because the inertia of tectonic plates is negligible plate velocities result from the balance of forces acting at plate margins and along their base1 observations of past plate motion derived from marine magnetic anomalies provide evidence of how continental deformation may contribute to plate driving forces2 3 4 5 6 7 8 a decrease in convergence rate at the inception of continental collision is expected because of the greater buoyancy of continental than oceanic lithosphere2 3 but post collisional rates are less well understood slowing of convergence has generally been attributed to the development of high topography that further resists convergent motion7 8 9 10 however the role of deforming continental mantle lithosphere on plate motions has not previously been considered here i show that the rate of india s penetration into eurasia has decreased exponentially since their collision the exponential decrease in convergence rate suggests that contractional strain across tibet has been constant throughout the collision at a rate of 7 03 10 16 s 1 which matches the current rate a constant bulk strain rate of the orogen suggests that convergent motion is resisted by constant average stress constant force applied to a relatively uniform layer or interface at depth this finding follows new evidence that the mantle lithosphere beneath tibet is intact11 which supports the interpretation that the long term strain history of tibet reflects deformation of the mantle lithosphere under conditions of constant stress and strength the deforming continental lithosphere creates a type of viscous resistance that affects plate motion irrespective of how topography evolved

location of the africa australia india triple junction and motion between the australian and indian plates results from an aeromagnetic investigation of the central indian and carlsberg ridges accepted 1994 june 7 received 1994 may 23 in original form 1993 may 24 summary prior studies have proposed and examined the hypothesis that india and australia are separate rigid plates separated by a wide near equatorial e w striking plate boundary attempts to place narrow limits on the location of the africa australiaindia triple junction have been hindered however by the lack of useful magnetic profiles crossing the eastern carlsberg ridge and northern central indian ridge herein we present near ridge portions of new profiles from an aeromagnetic survey of the carlsberg ridge east of 66 e and of the central indian ridge north of 19 s these new data are used to estimate 35 new spreading rates averaged from the middle of chron 2a 3 03 ma to the present all other plate motion data along the central indian and carlsberg ridges are also analysed to investigate the present kinematics of the indian ocean especially the motion and boundary between the indian and australian plates unlike prior efforts we objectively estimate uncertainties in the strikes of transform faults along the carlsberg and central indian ridges

measurements of glacier variation in the tibetan plateau using landsat data glaciers on the tibetan plateau play an important role in the earth s climate system because of high altitude and difficulties in access regular systematic surveys of glacier variation are almost impossible in some regions of the tibetan plateau as a result remote sensing is at present the primary in many cases the only way to measure the state of glaciers in combination with geographic information system gis it provides an efficient tool to analyze the current state and changes in glaciers we used a technique of integrated remote sensing and gis to map and measure changes in glaciers using a 21 year series of landsat images from 1973 to 1994 and topographic maps of a study site on the tibetan plateau the details of glacier fluctuation such as area of glaciers and changes in the magnitude of recession or advance of a glacier terminus on different dates are described based on the results of image analysis including coregistration classification vector analysis and area calculation within the study area during the 21 years it was determined that the northern glaciers advanced and the southern glaciers retreated the average rate of change was 50 m a 1 to 105 m a 1 the results show that landsat data provide an important source of information for studies of glacier variation

development and validation of a snow albedo algorithm for the modis instrument a prototype snow albedo algorithm has been developed for the moderate resolution imaging spectroradiometer modis it complements existing modis products by providing albedo measurements for areas mapped as snow on a global daily basis by modis cloud detection and atmospheric correction are accomplished using existing modis products models of the bidirectional reflectance of snow created using a discrete ordinate radiative transfer disort model are used to correct for anisotropic scattering effects over non forested surfaces initial algorithm validation is undertaken through comparisons with broadband albedo measurements made at the u s national oceanic and atmospheric administration noaa surface radiation budget network surfrad site in fort peck mt in situ surfrad albedo measurements are compared to daily modis snow albedo retrievals for the period 21 26 november 2000 created from five narrow to broadband albedo conversion schemes the prototype modis algorithm produces reasonable broadband albedo estimates maximum daily differences between the five modis broadband albedo retrievals and in situ albedo are 15 daily differences between the best modis broadband estimate and the measured surfrad albedo are 1 8 however no single conversion scheme consistently provides the closest albedo estimate further validation and algorithm development using data from north america and greenland is ongoing

recession of the southern part of barnes ice cap baffin island canada between 1961 and 1993 determined from digital mapping of landsat tm changes along the margin of the southern half of the 5900 km 2 barnes ice cap have been assessed using 1993 landsat tm imagery in comparison with digitized 1 50 000 nts maps based on 1961 photogrammetry the average recession over the 183 km long southern perimeter was found to be at least 4 m a 1 with no significant difference between the southeast and southwest sectors viewed in conjunction with the sustained retreat previously reported for the northwest margin these results indicate that a general reduction in the size of barnes ice cap is occurring the present retreat phase began under a regional climate warming in the late 19th to early 20th century period and continues while the record of the ablation season temperature since the midcentury has not shown any significant trend

identification of snow ablation rate ela aar and net mass balance using transient snowline variations on two arctic glaciers identification of the transient snowline tsl from high spatial resolution landsat imagery on lemon creek glacier lcg southeast alaska usa and mittivakkat gletscher mg southeast greenland is used to determine snow ablation rates the equilibrium line altitude ela and the accumulation area ratio aar the rate of rise of the tsl during the ablation season on a glacier where the balance gradient is known provides a measure of the snow ablation rate on both lcg and mg snow pits were completed in regions that the tsl subsequently transects this further provides a direct measure of the snow ablation rates for a particular year tsl observations from multiple dates during the ablation season from 1998 to 2011 at lcg and 1999 to 2012 at mg were used to explore the consistency of the tsl rise and snow ablation rate on lcg and mg the satellite derived mean tsl migration rates were 3 8 0 6 and 9 4 9 1md 1 respectively the snow ablation rates were 0 028 0 004 m w e d 1 for lcg and 0 051 0 018 m w e d 1 for mg estimated by applying a tsl mass balance gradient method and 0 031 0 004 and 0 047 0 019 m w e d 1 by applying a snow pitsatellite method illustrating significant agreement between the two different approaches for both field sites also satellite derived ela and aar and estimated net mass balance ba conditions were in agreement with observed ela aar and ba conditions for lcg and mg

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

satellite derived melt season surface temperature of the greenland ice sheet 2000 2005 and its relationship to mass balance 1 mean clear sky surface temperature of the greenland ice sheet was measured for each melt season from 2000 to 2005 using moderate resolution imaging spectroradiometer modis derived land surface temperature lst data product maps during the period of most active melt the mean clear sky surface temperature of the ice sheet was highest in 2002 8 29 5 29 c and 2005 8 29 5 43 c compared to a 6 year mean of 9 04 5 59 c in agreement with recent work by other investigators showing unusually extensive melt in 2002 and 2005 surface temperature variability shows a correspondence with the dry snow facies of the ice sheet a reduction in area of the dry snow facies would indicate a more negative mass balance surface temperature variability generally increased during the study period and is most pronounced in the 2005 melt season this is consistent with surface instability caused by air temperature fluctuations

india eurasia collision chronology has implications for crustal shortening and driving mechanism of plates the motion of the indian plate is determined in an absolute frame of reference and compared with the position of the southern margin of eurasia deduced from palaeomagnetic data in tibet the 2 600 900 km of continental crust shortening observed is shown to have occurred in three different episodes subduction of continental crust intracontinental thrusting and internal deformation and lateral extrusion the detailed chronology of the collision and plate reorganizations in the indian and pacific oceans supports the hypothesis that slab pull is a dominant driving mechanism of plate tectonics

pacific antarctic australia motion and the formation of the macquarie plate summary magnetic anomaly and fracture zone data on the southeast indian ridge seir are analysed in order to constrain the kinematic history of the macquarie plate the region of the australian plate roughly east of 145 e and south of 52 s finite rotations for australia antarctic motion are determined for nine chrons 2ay 3ay 5o 6o 8o 10o 12o 13o and 17o using data limited to the region between 88 e and 139 e these rotations are used to generate synthetic flowlines which are compared with the observed trends of the easternmost fracture zones on the seir an analysis of the synthetic flowlines shows that the macquarie plate region has behaved as an independent rigid plate for roughly the last 6 myr finite rotations for macquarie antarctic motion are determined for chrons 2ay and 3ay these rotations are summed with australia antarctic rotations to determine macquarie australia rotations we find that the best fit macquarie australia rotation poles lie within the zone of diffuse intraplate seismicity in the south tasman sea separating the macquarie plate from the main part of the australian plate motion of the macquarie plate relative to the pacific plate for chrons 2ay and 3ay is determined by summing macquarie antarctic and antarctic pacific rotations the pacific macquarie rotations predict a smaller rate of convergence perpendicular to the hjort trench than the pacific australia rotations the onset of the deformation of the south tasman sea and the development of the macquarie plate appears to have been triggered by the subduction of young buoyant oceanic crust near the hjort trench and coincided with a clockwise change in pacific australia motion around 6 ma the revised pacific australia rotations also have implications for the tectonics of the alpine fault zone of new zealand we find that changes in relative displacement along the alpine fault have been small over the last 20 myr the average rate of convergence over the last 6 myr is about 40 per cent smaller than in previous models

anisotropy of the reflected radiation field over melting glacier ice abstract in this article we analyze the anisotropy of the reflected radiation field over melting glacier ice using 118 ground based radiance measurements in landsat tm bands 2 and 4 the measurements were carried out on the tongue of the morteratschgletscher switzerland on the basis of directional measurements several bidirectional reflectance distribution functions brdfs were derived for dirty and clean glacier ice and for solar zenith angles between 46 and 60 the anisotropic reflectance factor ranges between 0 70 and 1 60 for tm 2 and between 0 56 and 1 72 for tm 4 the brdfs exhibit nadir darkening and maximum brightening near the forward limb dirty and wet ice reflect more anisotropically than clean ice we give an example to illustrate the effect of anisotropic reflectance on the tm derived albedo along a cross section of the glacier for solar zenith angles around 48 and in the nadir viewing direction we found differences of 0 05 in tm 2 and 0 08 in tm 4 between the albedo and bidirectional reflectance r the differences prove to be more or less uniform for both clean ice and dirty ice it is therefore suggested that one can convert r to without having to classify the glacier surface

the sawqirah contourite drift system in the arabian sea nw indian ocean a case study of interactions between margin reactivation and contouritic processes the relationships between oceanic circulation in the arabian sea and late cenozoic climate changes including variations in monsoon intensity at the million year time scale remain poorly investigated using multibeam and seismic data we provide the first description of a contourite drift in the arabian sea along the south eastern oman margin this contourite drift is referred as the sawqirah contourite drift system late miocene reactivation of the south eastern oman margin resulted in the formation of a complex anticline system which shaped the seafloor topography above which the sawqirah drift subsequently developed the drift resulted from the circulation of bottom currents within the north intermediate indian water major seismic unconformities identified within the sawqirah drift were tied to ocean drilling program odp drill holes and allowed defining distinct episodes of drift construction at least two of these unconformities record reorganizations of the oceanic circulation at 4 5 4 8 ma and 2 4 ma the 4 5 4 8 ma old unconformity is coeval with the onset of upwelling of deep and cold waters in the owen basin the 2 4 ma old unconformity records a major episode of indian monsoon intensification at the million year time scale over the arabian sea indicating strong coupling between oceanic and atmospheric circulation processes

kinematic constraints on distributed lithospheric deformation in the equatorial indian ocean from present motion between the australian and indian plates from an expanded accurate and up to date data set comprising 110 spreading rates 46 transform azimuths and 151 earthquake slip vectors from the indian ocean and gulf of aden we determine a new rigid plate model describing the motion since 3 ma between india and australia the euler vector 0 313 m y about 5 s 78 e lies near the middle of the equatorial diffuse plate boundary dividing the indian from the australian plate and predicts a rate of north south shortening along 85 e of 4 3 mm yr only 30 as fast as predicted by our prior model the new model also predicts north south extension of 6 2 mm yr at 68 e along the western segment of the diffuse plate boundary where our prior model predicted north south contraction using data only along the carlsberg and central indian ridges and no other plate boundaries we show that plate motion data cannot be fit by a single euler vector however the data are well fit by two euler vectors when an east west striking india australia plate boundary is assumed to intersect the central indian ridge near the equator the best location along the central indian ridge for this triple junction is 6 s 3 s with 95 confidence limits of 9 s 4 n just west of a region of intense seismicity the sense of deformation as recorded in earthquake focal mechanisms reverse faults mapped with reflection seismic data and undulations in basement topography surface gravity and the geoid agrees well with the north south extension predicted in the western part and the north south shortening predicted in the eastern part of the india australia boundary the predicted rate of north south shortening between 79 e and 86 e is consistent with the rate of shortening inferred from observed faulting and folding shortening taken up by faulting is 6 to 100 times greater than that taken up by the spectacular basement folds little of the rapid north south shortening predicted east of 86 e is taken up by crustal thickening instead lithosphere is transported northeastward toward the sumatra trench through strike slip faulting and possible clockwise rotation the failure of the convergent segment of the diffuse plate boundary to form a subducting trench provides some new observations that must be satisfied by models for the initiation of subduction a model of separate rigid indian and australian plates divided by a diffuse plate boundary appears to be valid and useful because the predictions of the model agree with independent data and because the predicted velocity of relative motion is statistically significant and comparable with that across other plate boundaries

a high resolution model for eurasia north america plate kinematics since 20 ma summary we derive the first chronologically detailed model of eurasia north america plate motion since 20 ma from ship and airplane surveys of the well expressed magnetic lineations along this slowly spreading plate boundary including previously unavailable dense russian magnetic data from the southern reykjanes ridge and northern mid atlantic ridge near the charlie gibbs fracture zone from more than 7000 crossings of 21 magnetic anomalies from anomaly 1n 0 78 ma to anomaly 6n 19 7 ma we estimate best fitting finite rotations and realistic uncertainties linear regressions of total opening distances versus their reversal ages at different locations along the plate boundary show that reversal boundaries are shifted systematically outwards from the spreading axis with respect to their idealized locations with the outward shift ranging from more than 5 km between iceland and the charlie gibbs fracture zone to 2 km elsewhere this outward displacement which is a consequence of the finite zone of seafloor accretion degrades estimates of the underlying plate motion and is thus removed for the ensuing kinematic analysis the corrected plate motion rotations reveal surprising previously unrecognized features in the relative motions of these two plates within the uncertainties motion was steady from 20 to 8 ma around a pole that was located 600 km north of the present pole with seafloor spreading rates that changed by no more than 5 per cent 1 mm yr 1 along the reykjanes ridge during this period seafloor spreading rates decreased abruptly by 20 2 per cent at 7 5 6 5 ma coinciding with rapid southward migration of the pole of rotation and a5 10 counter clockwise change in the plate slip direction eurasia north america plate motion since 6 7 ma has remained remarkably steady with an apparently stationary axis of rotation and upper limit of 2 per cent on any variations in the rate of angular rotation during this period based on the good agreement between seismotectonic constraints on present deformation in northeast asia and directions of motion that are predicted by our 6 7 ma to present pole we hypothesize that motion has remained steady to the present and attempt to test this hypothesis with published gps estimates for eurasia north america motion we find however that gps estimates that are tied to recent versions of the international geodetic reference frame and rely principally on station velocities from europe give implausible estimates of recent motion with the most recently published gps model predicting convergence along the southern gakkel ridge and in the laptev sea where seafloor spreading occurs an alternative gps estimate that is not tied to the international terrestrial reference frame and employs gps station velocities from northeastern asia is marginally consistent with our 6 7 0 ma motion estimate

a geodynamical view on the steadiness of geodetically derived rigid plate motions over geological time 1 the ability to map ocean floor magnetization is key to infer past plate motions the advent of geodesy in the earth sciences offered an independent snapshot of contemporary plate kinematics averaged over decades early studies suggested plate motions steadiness through geological time because contemporary rates were similar to past 3 myr averages recent data however show that geodetic and paleo magnetic motions exhibit differences beyond confidence ranges which might suggest geodesy samples time scales shorter than a few centuries these differences pose important questions on the character of plate kinematic variability through time here i derive inferences on the steadiness of geodetically derived plate motions by combining geodynamical arguments with kinematic data sets i exploit data sets to build scenarios for the recent evolution of most of the major plates i compare the minimum rate at which torque needs to vary to generate these scenarios with the maximum rate at which geological processes can contribute torque this allows assessing the geodynamical plausibility of each scenario results indicate that plate motion changes recorded since 3 ma must have taken at least 1 myr to occur two exceptions are the pacific and australian plates whose motions changed by less than 5 and therefore required torque variations that might be built over periods as short as 0 1 myr it remains unresolved for how long geodetically derived plate motions kept steady in the geological past however results indicate it is indeed plausible that they did over the past 1 2 myr these inferences call for a shift in the way we regard the figure of geodetic plate motions

surface motions and continental deformation in the indian plate and the india eurasia collision zone the collision of the indian plate with eurasia has played a major role in controlling the dynamics of central asia leading to the world s largest continental deformation zone in order to study the deformation within the indian plate as well as the india eurasia collision zone we model the lithospheric stress field by calculating the two primary sources of stress one arising due to topography and shallow lithospheric structure estimated by gravitational potential energy differences and the other arising from basal tractions derived from density driven mantle convection we use several tomography models to calculate horizontal tractions using the convection code hc for two radially varying viscosity structures we also take into account lateral viscosity variations in the lithosphere model arising from stiff cratons weak plate boundaries and strength variations due to old and young oceanic lithosphere we do a quantitative comparison of our predicted deviatoric stresses strain rates and plate velocities with surface observables and find that the regional tomography model of singh et al 2014 embedded in the global s wave model s40rts does a remarkable job of fitting the observations of gps velocities and strain rates as well as intraplate stress field from the world stress map

motion between the indian capricorn and somalian plates since 20 ma implications for the timing and magnitude of distributed lithospheric deformation in the equatorial indian ocean summary approximately 2200 magnetic anomaly crossings and 800 fracture zone crossings flanking the carlsberg ridge and central indian ridge are used to estimate the rotations of the indian and capricorn plates relative to the somalian plate for 20 distinct points in time since 20 ma the data are further used to place limits on the locations of the northern edge of the rigid capricorn plate and of the southern edge of the rigid indian plate along the central indian ridge data south of and including fracture zone n the fracture zone immediately south of the vema fracture zone which intersects the central indian ridge near 10 s are well fit assuming rigid capricorn and somalian plates while data north of fracture zone n are not in agreement with prior results data north of fracture zone h which intersects the central indian ridge near 3 2 s are well fit assuming rigid indian and somalian plates while data south of and including fracture zone h are not resulting in a smaller rigid indian plate and a wider diffuse oceanic plate boundary than found before the data are consistent with capricorn somalia motion about a fixed pole since 8 ma but require rotation about a pole 15 farther away from the central indian ridge from 20 to 8 ma the post 8 ma pole also indicates capricorn somalia displacement directions that are 7 clockwise of those indicated by the pre 8 ma stage pole in contrast india somalia anomaly and fracture crossings are well fit by a single fixed pole of rotation for the past 20 ma india somalia motion has changed little during the past 20 myr nonetheless astronomically calibrated ages for reversals younger than 12 9 ma allow resolution of the following small but significant changes in spreading rate india somalia spreading slowed from 31 to 28 mm yr 1 near 7 9 ma and later sped up to 31 mm yr 1 near 3 6 ma capricorn somalia spreading slowed from 40 to 36 mm yr 1 near 11 0 ma later sped up to 38 mm yr 1 near 5 1 ma and further sped up to 40 mm yr 1 near 2 6 ma the motion between the indian and capricorn plates is estimated by differencing india somalia and capricorn somalia rotations which differ significantly for all 20 pairs of reconstructions india has rotated relative to the capricorn plate since at least 20 ma if about a pole located near 4 s 75 e the rate of rotation was slow 0 11 0 01 myr 1 95 per cent confidence limits from 20 to 8 ma but increased to 0 28 0 01 myr 1 95 per cent confidence limits at 8 ma the onset of more rapid rotation coincides within uncertainty with the inferred onset at 7 8 ma of widespread thrust faulting in the central indian basin and with the hypothesized attainment of maximum elevation and initiation of collapse of the tibetan plateau at 8 ma the plate kinematic data are consistent with steady india capricorn motion since 8 ma and provide no evidence for previously hypothesized episodic motions during that interval the convergence since 8 ma between the indian and capricorn plates significantly exceeds by 13 to 20 km the convergence estimated from three north south marine seismic profiles in the central indian basin where and how the additional convergence was accommodated is unclear

reconciling plate kinematic and seismic estimates of lithospheric convergence in the central indian ocean the far field signature of the india asia collision and history of uplift in tibet are recorded by sediment input into the indian ocean and the strain accumulation history across the diffuse plate boundary between the indian and capricorn plates we describe the history of india capricorn convergence from updated estimates of india somalia capricorn plate rotations and observations derived from seismic reflection data new india capricorn plate rotations for the past 20 m y are consistent with slow north south convergence from 18 ma about a stationary or nearly stationary pole near the eastern edge of the chagos laccadive ridge simpler than predicted by previous models based on many fewer data the new rotations suggest that convergence began between 18 and 14 ma consistent with marine seismic evidence for an onset of deformation at 15 4 13 9 ma they further show that convergence rates doubled at 8 ma in agreement with a sharp increase in fault activity at 8 7 5 ma seen on seismic reflection profiles a discrepancy between the total strain estimated from kinematic and seismic reflection data can be reconciled if pervasive reverse faulting within the diffuse plate boundary is accompanied by block rotations of 1 3

community infrastructure and repository for marine magnetic identifications magnetic anomaly identifications underpin plate tectonic reconstructions and form the primary data set from which the age of the oceanic lithosphere and seafloor spreading regimes in the ocean basins can be determined although these identifications are an invaluable resource their usefulness to the wider scientific community has been limited due to the lack of a central community infrastructure to organize host and update these interpretations we have developed an open source community driven online infrastructure as a repository for quality checked magnetic anomaly identifications from all ocean basins we provide a global sample data set that comprises 96 733 individually picked magnetic anomaly identifications organized by ocean basin and publication reference and provide accompanying hellingerformat files where available our infrastructure is designed to facilitate research in plate tectonic reconstructions or research that relies on an assessment of plate reconstructions for both experts and nonexperts alike to further enhance the existing repository and strengthen its value we encourage others in the community to contribute to this effort

review of available fluid sampling tools and sample recovery techniques for groundwater and unconventional geothermal research as well as carbon storage in deep sedimentary aquifers sampling fluids from deep wells and subsequent sample treatment prior to gas and liquid analysis requires special equipment and sampling techniques to account for the relatively high temperatures pressures and potential gas content present at depth this paper reviews five major sampling methodologies ranging from different in situ wireline samplers to producing pumps and the u tube and discusses their advantages and drawbacks in the light of three principal applications deep groundwater research unconventional geothermal exploration and carbon storage geochemical modelling is used to investigate the probability of decarbonation and concomitant carbonate scaling during sampling in geothermal and carbon sequestration applications the two principal sample recovery techniques associated with the fluid samplers are also presented

scale dependent analysis of satellite imagery for characterization of glacier surfaces in the karakoram himalaya abstract information regarding process structure relationships and change in the karakoram himalaya is of great importance in studying glacier hydrollogy mass balance and dynamic environmental change such information is not readily available detailed spatio temporal assessment requires field investigation coupled with quantitative remote sensing studies we conducted an investigation of the large batura glacier in pakistan to determine if spectral variability can be quantified and used to characterize glacier surfaces specifically spot panchromatic satellite data were evaluated for differentiating features of glacier structure resulting from ice movement ablation and supraglacial fluvial action image semivariogram analysis was conducted for assessing spectral variability patterns and fractal analysis was used to examine scale dependent variation in the data results indicate that spectral variability from fields of ice seracs can exhibit fractal characteristics although most surface features on the glacier exhibit a change in the fractal dimension over different ranges in scale the fractal dimension was found to be useful for differentiating between glacier surfaces such as white ice and debris covered ice characteristics of the debris load and the scale dependent nature of calculating the fractal dimension ultimately determined the potential of class separability

relating rapid plate motion variations to plate boundary forces in global coupled models of the mantle lithosphere system effects of topography and friction abstract recent high resolution models of past plate motions and their comparison with plate motion models inferred from space geodetic techniques reveal a number of short term variations in global plate velocities over the past 10 myrs such variations serve as powerful probe into the nature and magnitude of plate boundary forces because they are unlikely to originate from changes in mantle buoyancy forces which evolve on longer time scales here we explore the constraints of the velocity record using a novel coupled modeling approach of global neo tectonic simulations combined with realistic plate driving forces obtained from mantle circulation models mcms to arrive at simple global budgets of mantle lithosphere and plate boundary forces we focus on three plate boundary systems along the nazca south america plate margin the aleutian trench and the india australia plate boundary to show that gravitational spreading from high topography in the andes and tibet contributes substantially to the global plate tectonic force balance and that this contribution is sufficient to explain some 35 of recent velocity changes over the earth s surface including among others the observed 30 convergence reduction between the nazca south america plates our models make a number of specific predictions such as significant lateral variations in plate coupling forces along a given margin revealed by trench parallel gravity and bathymetry anomalies and the occurrence of large earthquakes as well as differences by as much as a factor of five from margin to margin they also support the notion of a relatively young plate boundary separating the india and australia plates which has been previously suggested based on independent observations importantly we find that the modeled nazca south america convergence reduction explains recent spreading rate variations in the south atlantic and south pacific which points to the importance of far field effects on the adjacent continents in explaining the spreading record of oceanic basins our numerical results demonstrate a that detailed budgets of forces acting upon plates can be obtained and b support the notion of strong forcing along weak plate boundaries

indian ocean floor deformation induced by the reunion plume rather than the tibetan plateau the central indian ocean is considered the archetypal diffuse oceanic plate boundary data from seismic stratigraphy and deep sea drilling indicate that the contractional deformation of the indian ocean lithosphere commenced at 15 4 13 9 ma but experienced a sharp increase at 8 7 5 ma this has been maintained through to the present day with over 80 of the shortening accrued over the past 8 myr here we build on previous efforts to refine the form timing and magnitude of the regional plate motion changes by mitigating the noise in reconstructed indian and capricorn plate motions relative to somalia our noise mitigated reconstructions tightly constrain the significant speed up of the capricorn plate over the past 8 myr and demonstrate that the history of the indian ocean floor deformation cannot be explained without this plate motion change we propose that the capricorn plate motion change is driven by an increase in the eastward directed asthenospheric flow associated with the adjacent reunion plume and quantitatively demonstrate the viability of this hypothesis our inference is supported by volcanic age distributions along the reunion hotspot track the anomalously high residual bathymetry of the central indian ridge full waveform seismic tomography of the underlying asthenosphere and geochemical observations from the central indian ridge these findings challenge the commonly accepted link between the deformation of the indian ocean floor and the tibetan plateau s orogenic evolution and demonstrate that temporal variations in upwelling mantle flow can drive major tectonic events at the earth s surface deformation of the indian ocean floor over the past 8 million years was caused by a change in plate motions linked to flow of the reunion mantle plume according to analyses of forces upon plates

the seafloor spreading rate dependence of the anomalous skewness of marine magnetic anomalies summary we have determined the anomalous skewness of marine magnetic anomalies other than anomaly 33 34 in slow spreading regimes in the arctic atlantic and indian oceans and found a significant dependence of the anomalous skewness on the spreading rate the anomalous skewness is highest for slow spreading and insignificant for spreading above 6 cm yr 1 also the anomalous skewness of anomaly 33 34 is significantly larger than that of anomalies 25 26 and 20 21 whether or not anomalies m2 m4 exhibit anomalous skewness is uncertain because of the large variability in their shapes to facilitate the study of anomalous skewness of marine magnetic anomalies we have developed an analytic method based on functions calculated directly from the magnetic profiles that does not require a priori knowledge about the exact locations of magnetization contrasts

owen fracture zone the arabia india plate boundary unveiled we surveyed the owen fracture zone at the boundary between the arabia and india plates in the nw indian ocean using a high resolution multibeam echo sounder owen cruise 2009 for search of active faults bathymetric data reveal a previously unrecognized submarine fault scarp system running for over 800 km between the sheba ridge in the gulf of aden and the makran subduction zone the primary plate boundary structure is not the bathymetrically high owen ridge but is instead a series of clearly delineated strike slip fault segments separated by several releasing and restraining bends despite an abundant sedimentary supply by the indus river flowing from the himalaya fault scarps are not obscured by recent deposits and can be followed over hundreds of kilometres pointing to very active tectonics the total strike slip displacement of the fault system is 10 12 km indicating that it has been active for the past 3 to 6 ma if its current rate of motion of 3 1 mm yr 1 has remained stable we describe the geometry of this recent fault system including a major pull apart basin at the latitude 20 n and we show that it closely follows an arc of small circle centred on the arabia india pole of rotation as expected for a transform plate boundary

constraints on indian plate motion since 20 ma from dense russian magnetic data implications for indian plate dynamics we use more than 230 000 km of russian marine magnetic and bathymetric data from the carlsberg and northern central indian ridges comprising one of the most geographically extensive dense shipboard surveys anywhere in the ocean basins to describe in detail seafloor spreading since 20 ma along the trailing edge of the indian plate india somalia plate rotations for 1 myr intervals over the past 20 myr are derived from inversions of more than 6600 crossings of 20 magnetic reversals and 1400 crossings of fracture zones that offset these two ridges statistical analysis of the numerous data indicates that outward displacement of reversal boundaries due to finite seafloor emplacement widths and correlated noise for anomaly crossings from individual spreading segments constitute two distinct sources of systematic bias in the locations of magnetic anomaly crossings contrary to the often made assumption that random gaussian distributed noise dominates the error budget seafloor spreading rates slowed gradually by 30 from 20 ma to 10 1 ma about a relatively stationary pole of rotation from 11 ma to 9 ma the rotation axis migrated several angular degrees toward the plate boundary modestly increasing the spreading gradient along the plate boundary india somalia kinematic data for times since 9 ma are consistent with remarkably steady motion with no evidence for a change in either the rotation pole or rate of angular opening within the few percent precision of our data the timing and nature of changes in india somalia motion since 20 ma closely resemble those for the capricorn somalia plate pair indicating that india and capricorn plate motions are strongly coupled we speculate that the slowdown in seafloor spreading at the trailing edges of the indo capricorn composite plate from 20 ma to 10 1 ma resulted from the increasing amount of work that was needed to build topography in the himalayan collisional zone the transition to stable india somalia and capricorn somalia seafloor spreading at 10 9 ma corresponds well with the onset at 8 ma of folding and faulting across an equatorial plate boundary separating the indian and capricorn plates suggesting that the latter may have played a fundamental role in restoring equilibrium between the torques that were driving and resisting the northward motions of the indian and capricorn plates

confidence intervals for motion and deformation of the juan de fuca plate finite rotation parameters for 17 isochrons from anomalies 1 4a for the juan de fuca pacific plate pair are reported comparison of confidence intervals for plate rotations derived by different techniques indicates that a single plate misfit criterion significantly underestimates the confidence region defining the confidence interval by a threshold level of misfit determined by an f statistic gives similar results to the technique of bootstrap resampling for internally consistent data bootstrap resampling offers far greater robustness in the case of inconsistent data precision of about 1 km in the direction normal to isochrons is available for the younger anomalies this precision allows confident recognition of 2 5 km of eastward deformation of the pacific plate 50 100 km south of the active sovanco transform slight deformation of the northern juan de fuca plate adjacent to the nootka fault zone is also apparent east of the northern gorda ridge younger 3 ma anomalies do not show measurable deformation near the blanco fracture zone but older anomalies are up to 30 km east of their position predicted by rigid behavior of the juan de fuca plate reconstruction of the overlap geometry of past propagators shows no evidence that the extent of overlap has ever exceeded 70 km even with offset of 75 km in one case and 140 km in another new techniques for testing for intervals of constant plate motion require at least two changes in instantaneous motion at 99 confidence a clockwise change in motion direction at about 5 ma and an increase in the gradient of spreading rate since 2 ma two other changes in gradient since 5 ma are required at 95 confidence

comparison of in situ and landsat derived reflectance of alaskan glaciers abstract calculation of snow and ice albedo is necessary for developing physically realistic simulations of the earth s climate using general circulation models and useful for analysis of glacier mass balance change using remote sensing reflectances calculated from tm data and corrected for atmospheric effects correspond with in situ measured reflectances in the nadir viewing mode and are shown to be related to a glacier s mass balance if measured over a period of years a reflectance of 0 895 for a test site in the wrangell mountains alaska was calculated from tm band 4 0 76 0 90 m data and corrected for atmospheric effects this value was comparable to the in situ reflectance of 0 90 measured in the same 0 76 0 90 m wavelength region for the same site a reflectance value of 0 79 derived from integrating over most 0 40 3 0 m of the reflective portion of the electromagnetic spectrum was quite different from the integrated reflectance of 0 95 calculated for the spectral range 0 40 1 0 m this demonstrates the importance of using the full reflective energy spectrum for calculating the albedo of snow and for obtaining a meaningful computation of a glacier s energy and mass balance change

evidence for long term diffuse deformation of the lithosphere of the equatorial indian ocean the presence of large earthquakes east west striking folds and thrust faults in sediments and east west striking undulations of wavelength 200 km in topography and gravity shows that the equatorial indian ocean is the locus of unusual deformation1 2 3 4 5 6 7 8 this deformation has been interpreted as a diffuse boundary between two tectonic plates9 10 11 12 13 seismic stratigraphy and deep sea drilling at two locations in the bengal fan indicate that the deformation began 7 5 8 0 myr ago3 14 15 here however we show using plate reconructions that motion across this diffuse oceanic plate boundary began more than 10 myr earlier than previously inferred and that the amount of north south convergence across the boundary through the central indian basin has been significantly greater than the convergence estimated from seismic profiles the relative plate velocity accommodated across the central indian basin has varied with time and has been as fast as 6 mm yr 1 about half the separation rate of earth s slowest spreading mid ocean ridge the earliest interval of measurable motion which began more than 18 myr ago may coincide with rapid denudation of the tibetan plateau from 21 myr to 15 17 myr ref 16 the present motion across the central indian basin began no earlier than 11 myr following an earlier interval of slower motion from 18 to 11 myr and may have begun at 8 myr when the tibetan plateau is thought to have attained its maximum elevation16 17

validation of avhrr and modis derived albedos of snow and ice surfaces by means of helicopter measurements we describe the validation of surface albedos of snow and glacier ice as derived from advanced very high resolution radiometer avhrr and moderate resolution imaging spectrometer modis satellite data for this purpose we measured surface albedos from a helicopter over vatnajokull iceland and the kangerlussuaq transect western part of the greenland ice sheet in thematic mapper tm bands 2 and 4 and avhrr bands 1 and 2 and converted these values to measured albedos in three modis bands relative to other validation methods our helicopter measurements have the advantages of larger spatial coverage and of almost direct measurements in satellite sensor spectral bands we found the smallest differences between the satellite derived and helicopter albedos for the kangerlussuaq transect for avhrr data a mean difference of 0 01 in both bands with the satellite in near nadir position and for two modis images a mean difference of 0 00 0 02 for bands 2 and 4 and 0 03 for band 1 for two avhrr images of vatnajokull we found mean differences of up to 0 06 differences are primarily due to errors in the satellite derived albedos which in turn are mainly caused by errors in the calibration coefficients of the satellite sensors and insufficient knowledge of the angular distribution of the radiation reflected by snow and ice satellite data obtained from view zenith angles larger than 50 55 appeared to be unsuitable

neotectonics of the owen fracture zone nw indian ocean structural evolution of an oceanic strike slip plate boundary the owen fracture zone is a 800 km long fault system that accommodates the dextral strike slip motion between india and arabia plates because of slow pelagic sedimentation rates that preserve the seafloor expression of the fault since the early pliocene the fault is clearly observed on bathymetric data it is made up of a series of fault segments separated by releasing and restraining bends including a major pull apart basin at latitude 20 n some distal turbiditic channels from the indus deep sea fan overlap the fault system and are disturbed by its activity thus providing landmarks to date successive stages of fault activity and structural evolution of the owen fracture zone from pliocene to present we determine the durability of relay structures and the timing of their evolution along the principal displacement zone from their inception to their extinction we observe subsidence migration in the 20 n basin and alternate activation of fault splays in the vicinity of the qalhat seamount the present day owen fracture zone is the latest stage of structural evolution of the 20 myr old strike slip fault system buried under indus turbiditic deposits whose activity started at the eastern foot of the owen ridge when the gulf of aden opened the evolution of the owen fracture zone since 3 6 myr reflects a steady state plate motion between arabia and india such as inferred by kinematics for the last 20 myr period the structural evolution of the owen fracture zone since 20 myr including fault segments propagation and migration pull apart basin opening and extinction seems to be characterized by a progressive reorganisation of the fault system and does not require any major kinematics change

restoration of cenozoic deformation in asia and the size of greater india a long standing problem in the geological evolution of the india asia collision zone is how and where convergence between india and asia was accommodated since collision proposed collision ages vary from 65 to 35 ma although most data sets are consistent with collision being underway by 50 ma plate reconstructions show that since 50 ma 2400 3200 km west to east of india asia convergence occurred much more than the 450 900 km of documented himalayan shortening current models therefore suggest that most post 50 ma convergence was accommodated north of the indus yarlung suture zone we review kinematic data and construct an updated restoration of cenozoic asian deformation to test this assumption we show that geologic studies have documented 600 750 km of n s cenozoic shortening across and north of the tibetan plateau the pamir hindu kush region accommodated 1050 km of n s convergence geological evidence from tibet is inconsistent with models that propose 750 1250 km of eastward extrusion of indochina approximately 250 km of indochinese extrusion from 30 to 20 ma of indochina suggested by se asia reconstructions can be reconciled by dextral transpression in eastern tibet we use our reconstruction to calculate the required size of greater india as a function of collision age even with a 35 ma collision age the size of greater india is 2 3 times larger than himalayan shortening for a 50 ma collision the size of greater india from west to east is 1350 2600 km consistent with robust paleomagnetic data from upper cretaceous paleocene tethyan himalayan strata these estimates for the size of greater india far exceed documented shortening in the himalaya we conclude that most of greater india was consumed by subduction or underthrusting without leaving a geological record that has been recognized at the surface

the motion and boundary between the capricorn and australian plates the motions between the somalian antarctic and australian plates the three plates believed to meet at the rodrigues triple junction in the indian ocean are inconsistent with the assumption that all three plates are rigid the discrepancy is best explained if the australian plate contains two component plates thus the traditionally defined indo australian plate consists of three component plates and multiple diffuse plate boundaries the pattern of present deformation indicates that the boundaries between the three component plates are two unconnected zones accommodating divergence and a larger zone which we interpret as three diffuse convergent plate boundaries and a diffuse triple junction

snow mapping and classification from landsat thematic mapper data use of satellite multi spectral remote sensing data to map snow and estimate snow characteristics over remote and inaccessible areas requires that we distinguish snow from other surface cover and from clouds and compensate for the effects of the atmosphere and rugged terrain because our space borne radiometers typically measure reflectance in a few wavelength bands for climate modeling we must use inferences of snow grain size and contaminant amount to estimate snow albedo throughout the solar spectrum although digital elevation data may be used to simulate typical conditions for a satellite image precise registration of an elevation data set with satellite data is usually impossible instead an atmospheric model simulates combinations of thematic mapper tm band radiances for snow of various grain sizes and contaminant amounts these can be recognized in tm images and snow can automatically be distinguished from other surfaces and classified into clean new snow older metamorphosed snow or snow mixed with vegetation

rising ela and expanding proglacial lakes indicate impending rapid retreat of brady glacier alaska brady glacier is a large alaskan tidewater glacier that is beginning a period of substantial retreat examination of 27 landsat and modis images from the period 2003 to 2011 indicates that brady glacier has a mean equilibrium line altitude ela of 745 m and accumulation area ratio aar of 0 40 the zero balance ela is 600 m and equilibrium aar 0 65 the negative mass balance associated with the increased ela has triggered thinning of 20 100 m over most of the glacier below the ela from 1948 to 2010 the thinning has caused substantial retreat of seven calving distributary termini of the glacier thinning and retreat have led to an increase in the width of and water depth at the calving fronts in contrast the main terminus has undergone only minor retreat since 1948 in 2010 several small proglacial lakes were evident at the terminus by 2000 a permanent outlet river issuing from trick lake had developed along the western glacier margin initial lake development at the terminus combined with continued mass losses will lead to expansion of the lakes at the main terminus and retreat by calving the glacier bed is likely below sea level along the main axis of brady glacier to the glacier divide retreat of the main terminus in the lake will likely lead to a rapid calving retreat similar to bear excelsior norris portage and yakutat glaciers copyright 2013 john wiley sons ltd

some geometrical aspects of uncertainties in combined plate reconstructions the uncertainties in both the position of a pole of rotation and the rotation angle describing a plate reconstruction depend not only on the number and quality of data used but also on two geometrical factors the length of plate boundary represented by the data and the distance from the best fit pole to the center of the data region we describe a simple geometrical method that can be used to calculate minimum uncertainties in reconstructions based on positions of magnetic anomalies and fracture zones with finite uncertainties uncertainties in pole positions and angles corresponding to 10 km uncertainty in individual data points can when combined yield uncertainties in reconstructed positions greatly in excess of 10 km per rotation for example an uncertainty of 10 km in anomaly 6 reconstructions in the south pacific southeast indian northwest indian and north atlantic oceans would result in uncertainty of up to 190 km in the reconstructed position of the pacific plate with respect to north america at 19 8 m y b p existing data show that the realistic uncertainties for this case are twice as large as the calculated minimum uncertainties

recent spatial and temporal variations in debris cover on patagonian glaciers abstract supraglacial debris cover is an important component of glacier mass balance especially in areas characterised by widespread glacier recession mapping of the spatial and temporal changes in debris cover on the surface of the receding outlet glaciers of the temperate north patagonian icefield npi in southern south america between 1987 and 2015 shows that the total amount of debris cover has increased over time from 168 km2 in 1987 to 307 km2 in 2015 the number of debris covered glaciers increased from 24 in 1987 to 31 in 2001 and 32 out of 43 studied glaciers in 2015 the proportion of debris covered area has also increased from 4 1 in 1987 to 7 9 in 2015 with the largest proportional increases occurring east of the ice divide where 15 2 of the glacier ice is now debris covered over this time the total area of the npi decreased from 4133 to 3887 km2 the area occupied by proglacial and ice proximal lakes also increased from 112 to 198 km2 between 1987 and 2015 the terminal environment of many of the outlet glaciers of the npi changed from land terminating to lake calving and these glaciers are now receding into terminal lakes the change in the area of debris covered ice is influenced by the loss of ice at debris covered termini and by an increase in debris cover at higher elevations the glaciers of the npi remain highly dynamic as they recede and are therefore behaving very differently to high elevation glaciers such as those of the himalaya where debris cover leads to glacier stagnation at the termini

evidence for multiphase folding of the central indian ocean lithosphere long wavelength 100 300 km folding in the central indian ocean associated with the diffuse plate boundary separating the indian australian and capricorn plates is earth s most convincing example of organized large scale lithospheric deformation to test the timing and mechanics of this deformation as implied by plate kinematic and deformation models we present a new analysis of the seismic stratigraphy of the bengal fan sediments this analysis shows that the folding of the oceanic lithosphere was multiphase with major events occurring in the miocene 8 0 7 5 ma pliocene 5 0 4 0 ma and pleistocene 0 8 ma the miocene phase was the most intense and involved deformation of an area south of 1 s whereas in the pliocene the activity shifted northward in the final phase pleistocene the activity was focused in the equatorial region no evidence was found for deformation prior to 8 0 7 5 ma the spatial extent of the pleistocene folding event overlaps the pliocene and or miocene folding events and coincides with both the area of most active faulting and the zone of greatest historical seismicity the seismic data show that the timing of reverse faulting and thus more significant shortening of the lithosphere generally coincided with the phases of folding but there are examples of folding of the oceanic lithosphere without associated reverse faulting

india asia collision and the cenozoic slowdown of the indian plate implications for the forces driving plate motions the plate motion of india changed dramatically between 50 and 35 ma with the rate of convergence between india and asia dropping from 15 to 4 cm yr this change is coincident with the onset of the india asia collision and with a rearrangement of plate boundaries in the indian ocean on the basis of a simple model for the forces exerted upon the edges of the plate and the tractions on the base of the plate we perform force balance calculations for the precollision and postcollision configurations we show that the observed euler poles for the indian plate are well explained in terms of their locations and magnitudes if 1 the resistive force induced by mountain building in the himalaya tibet area is 5 6 10 12 n m 2 the net force exerted upon the indian plate by subduction zones is similar in magnitude to the ridge push force 2 5 10 12 n m and 3 basal tractions exert a resisting force that is linearly proportional to the plate velocity in the hot spot reference frame the third point implies an asthenospheric viscosity of 2 5 10 19 pa s assuming a thickness of 100 150 km synthetic euler poles show that crustal thickening in the tibetan plateau was the dominant cause of the cenozoic slowdown of the indian plate

relative motions of the pacific rivera north american and cocos plates since 0 78 ma we use magnetic anomaly and fracture zone crossings from 3 n 24 n along the east pacific rise to define the boundaries and relative velocities of the rigid pacific rivera north american and cocos plates since 0 78 ma and to test several hypotheses regarding the nature of deformation between these plates crossings of the 0 78 ma isochron from the pacific rivera rise north of 22 0 n are significantly better fit by the 0 0 78 ma pacific north america rotation than by a pacific rivera rotation thereby supporting a recently proposed model for accretion of the northern part of the rivera plate to north america a significant misfit of the pacific cocos rotation to crossings of anomaly ln from the east pacific rise north of 16 4 n suggests that seafloor north of 16 n moves relative to the rigid pacific or cocos plates we also find that nine crossings of the eastern rivera fracture zone and eight crossings of anomaly ln flanking the manzanillo spreading segment are fit well by a pacific rivera rotation the rivera cocos angular velocity derived from the best fitting pacific cocos and pacific rivera angular velocities predicts 19 3 mm yr 1 95 confidence limit of n s convergence near the center of the rivera cocos boundary nearby left lateral strike slip earthquakes with north trending fault planes suggest that convergence is accommodated via sinistral shear along a north trending zone the unambiguous kinematic and seismologic evidence for significant rivera cocos motion indicates that the absence of a well defined rivera cocos plate boundary cannot be interpreted as evidence that rivera cocos motion is slow or zero as is postulated in several previous studies the rivera cocos angular velocity predicts oblique rivera cocos convergence at the el gordo graben and beneath the manzanillo trough and southern colima graben any extension across these features since 0 78 ma thus cannot have resulted from divergence between the subducting rivera and cococs plates

a diffuse plate boundary model for indian ocean tectonics it is suggested that motion along the virtually aseismic owen fracture zone is negligible so that arabia and india are contained within a single indo arabian plate divided from the australian plate by a diffuse boundary the boundary is a zone of concentrated seismicity and deformation commonly characterized as intraplate the rotation vector of australia relative to indo arabia is consistent with the seismologically observed 2 cm yr of left lateral strike slip along the ninetyeast ridge north south compression in the central indian ocean and the north south extension near chagos