evaluating knickpoint recession along an active fault for paleoseismological analysis the huoshan piedmont eastern china abstract ground rupturing earthquakes can generate tectonic knickpoints within upstream reaches of streams across active fault zones these knickpoints are characteristic of upstream propagation of time related process once generated by an earthquake so analysis of knickpoint series in streams which cross fault zones can be used to infer paleoearthquake events we studied the knickpoints along the huoshan piedmont fault hpf which is an active normal fault in the shanxi faulted basin zone china and demonstrate that analysis of knickpoints shows evidence for two paleoearthquakes in the hpf first we identified knickpoints in bedrock reaches upstream of the hpf using high resolution dems derived from irs p5 stereo images and the stream gradient method after excluding non faulting knickpoints 47 knickpoints were identified in 23 bedrock reaches upstream from the hpf analysis of the most recent knickpoints caused by the 1303 ce hongdong earthquake allowed for local calibration of the retreat rates applying these retreat rates across the study area allows for the estimation of the age of other knickpoints and constrains the age ranges of two knickpoint groups to be 2269 3336 a bp and 4504 5618 a bp these ages constrain the ages of two paleoearthquake events at 2710 102 and 4980 646 a bp the knickpoints along the hpf obey the parallel retreating model in which knickpoint morphology was roughly maintained during retreat so the heights of knickpoints represent the coseismic vertical displacements generated by the earthquakes along the hpf the vertical offsets for these three earthquake events are similar and are approximately 4 m which indicates that the ruptures on the hpf obey a characteristic slip model with a similar slip distribution for several successive earthquakes these results provide additional evidence of paleoearthquakes on the hpf and show that analysis of knickpoint recession along an active fault is a valuable tool for paleoseismology

the 1971 may 12 burdur earthquake sequence sw turkey a synthesis of seismological and geological observations summary it is now widely accepted that the rapid extension observed in western turkey is mainly accommodated by large active normal faults which control the geomorphology the ne sw trending burdur acigol and baklan basins bounded by large faults form a system of half graben whose orientation is evident in both the topography and the tilting of neogene sediments adjacent to them we used long period p and sh waveforms to determine the source parameters of the two largest earthquakes of the 1971 may 12 sequence that occurred in the burdur region the main shock was followed by many aftershocks which were distributed in a broad zone elongated ne sw parallel to the long axes of the basins in the region documented surface breaks of the 1971 event suggest that the northwest dipping faults along the southern margin of the burdur basin are those which moved well exposed fault planes are found dominantly to the south of burdur lake the surface dips of these faults are greater than that of the nw dipping nodal plane obtained for the main shock combined seismological and geological observations suggest that these faults have listric geometries

seismicity normal faulting and the geomorphological development of the gulf of corinth greece the corinth earthquakes of february and march 1981 three major destructive earthquakes of m s 6 7 6 4 6 4 occurred in the eastern part of the gulf of corinth in february and march 1981 associated normal faulting was observed on both the north and the south sides of the gulf examination of teleseismic local seismic surface faulting and geomorpbological data suggests that the first and second of these shocks activated major north dipping normal faults these faults control the topography and bathymetry and are related to the recent uplift and subsidence of the coastline it is probable that the first earthquake occurred on a faultwhich outcrops underwater and the second on a fault which is visible on land it appears that the third shock activated an antithetic normal fault dipping southwards on the north side of the gulf and that the overall structure of the gulf of corinth graben is asymmetric the northern antithetic fault clearly demonstrates the geomorphological changes associated with developing young normal faulting in addition we suggest that observations of recent coastline movement provide a powerful tool for identifying major active fault systems and predicting their historical role in the paleogeography of an area

mass balance of white glacier axel heiberg island n w t canada 1960 91 white glacier is a valley glacier at 79 5 n with an area of 38 7 km 2 its mass balance has been measured over 32 years with a 3 year gap by standard techniques using the stratigraphic system with a stake density of the order of one stake per km 2 errors in stake mass balance are about 200 250 mm due largely to the local unrepresentativeness of measurements errors in the whole glacier mass balance b are of the same order as single slake errors however the lag 1 autocorrelation in the time series of b is effectively zero so it consists of independent random samples and the error in the long term balance normal b is noticeably less b is 100 48 mm the equilibrium line altitude ela averages 970 m with a range of 470 1400 m mass balance is well correlated with ela but detailed modelling shows that the equilibrium line is undetectable on visible band satellite images a reduced network of a few stakes could give acceptable but less accurate estimates of the mass balance as could estimates based on data from a weather station 120 km away there is no evidence of a trend in the mass balance of white glacier to detect a climatologically plausible trend will require a ten fold reduction of measurement error a conclusion which may well apply to most estimates of mass balance based on similar stake densities

disequilibrium partial melting model and its implications for trace element fractionations during mantle melting abstract a model to describe trace element evolutions during partial melting is proposed by assuming surface equilibrium instead of complete equilibrium between mineral grains and melt and by considering the following factors 1 chemical diffusion in minerals 2 melting and melt extraction for mantle melting rates of 10 7 yr 1 inferred from mid ocean ridge spreading rates elements with diffusivities d in minerals of 10 15 cm 2 s be at equilibrium between minerals of 0 5 cm in diameter and melt during mantle melting however the anomalous radioactive excess of 236 ra over 230 th up to 300 in young basalts which cannot be explained by equilibrium melting because of the highly incompatible nature of both elements can be accounted for by the present model only when melting rate is in the orders of 10 6 to 10 5 yr 1 the disequilibrium effect cannot be ignored for elements with d 13 cm 2 s if the melting rate is 10 5 yr 1 disequilibrium melting lowers the incompatibility of an incompatible element the high the incompatibility the more obvious this effect is fractionation of trace elements during disequilibrium melting depends both on their equilibrium partition coefficients k and their diffusivities this has two consequences 1 fractionation of two highly incompatible elements k 0 01 by more than 20 is still possible at melting degree as high as 15 if their diffusivities differ by a factor of 5 or more as compared to the requirement for less than 5 partial melting for the same extent of fractionation by equilibrium melting and 2 the incompatibility order of two incompatible elements can be reversed under certain circumstances i e k 1 k 2 but d 1 d 2 the pb paradox namely that the u pb ratio in mantle sources inferred from pb isotopes has increased during the differentiation of the earth even though pb is less incompatible than u is explainable if the diffusivity of pb is higher than that of u e g by a factor of 10 and if the melting rate is in the order of 10 5 yr 1

area change of glaciers across northern ellesmere island nunavut between 1999 and 2015 using a variety of optical satellite scenes this study quantifies the change in the areal extent of 1773 glaciers across northern ellesmere island between 1999 and 2015 our results show that the regional ice coverage decreased by 1705 3 km 2 over the 16 year period a loss of 5 9 ice shelves had the greatest losses relative to their size of 42 4 glaciers feeding into ice shelves reduced in area by 4 7 while tidewater glaciers reduced in area by 3 3 marine terminating glaciers with floating ice tongues reduced in area by 4 9 and 19 of these 27 ice tongues disintegrated causing these glaciers to retreat to their grounding lines land terminating glaciers lost 4 9 of their 1999 area including the complete loss of three small ice caps 2 our study highlights the high sensitivity of the ice cover of northern ellesmere island to recent climate warming and the continued losses that are likely to occur in the future in particular the ice masses most susceptible to further losses are marine terminating glaciers with floating termini and small land terminating ice caps at low elevations

irreversible mass loss of canadian arctic archipelago glaciers 1 the canadian arctic archipelago caa contains the largest volume of glacier ice on earth outside of antarctica and greenland in the absence of significant calving caa glacier mass balance is governed by the difference between surface snow accumulation and meltwater runoff surface mass balance here we use a coupled atmosphere snow model to simulate present day and 21st century caa glacier surface mass balance through comparison with gravity recovery and climate experiment mass anomalies and in situ observations we show that the model is capable of representing present day caa glacier mass loss as well as the dynamics of the seasonal snow cover on the caa tundra next we force this model until 2100 with a moderate climate warming scenario ar5 rcp4 5 we show that enhanced meltwater runoff from caa glaciers is not sufficiently compensated by increased snowfall extrapolation of these results toward an ar5 multimodel ensemble results in sustained 21st century caa glacier mass loss in the vast majority 99 of the 7000 temperature realizations

seismic history of a bedrock fault scarp using quantitative morphology together with multiple dating methods a case study of the luoyunshan piedmont fault southwestern shanxi rift china abstract the study of bedrock fault scarps is a useful approach to identify paleo earthquakes and acquire the faulting history in bedrock areas where traditional trench techniques are not applicable here we report a study on the luoyunshan piedmont fault lyspf southwestern shanxi rift china although several studies have analyzed the lyspf its faulting behavior is still under debate for example the tectonic geomorphology fails to determine the frequency of past slips and the elapsed time to address these problems we investigated two bedrock fault surfaces luoyuncun northern segment and weicun southern segment using quantitative morphology analyses together with multiple quaternary dating techniques quantitative morphology analysis shows that both bedrock fault surfaces have the characteristics of vertical segmentation this kind of segmentation indicates that the fault surfaces are exhumed intermittently likely owing to periodic faulting earthquakes therefore earthquake events can be identified as morphological segments and the corresponding co seismic displacement can be determined by the height of these segments according to the results from the quantitative morphology and dating techniques four seismic events with a co seismic vertical displacement of 0 9 m 0 82 m 1 64 to 2 38 m and 2 30 to 2 54 m on the northern segment occurred during the late pleistocene whereas two seismic events with a co seismic vertical displacement of 1 33 m and 1 to 1 08 m are identified on the southern segment occurred during the holocene combined with the results of knickpoint series and trench techniques of the lyspf eight paleo earthquake events were identified since 45 ka with an average recurrence interval of 5 8 kyr the more complete paleo earthquake sequence also showed the possibility that the variation of the slip rate along the lyspf depends on the segment and that the displacement produced by the linfen m 7 earthquake of 649 ce has been recorded at the wc fault surface

roughness of natural fault surfaces the roughness of fault surfaces is important in the mechanics of fault slip and could play a role in determining whether sliding occurs via earthquakes or fault creep we have made preliminary measurements of the power spectral density of several fault surfaces over the wavelength range from 10 5 to 1 m using field and laboratory scale profilimeters the fault surfaces are strongly anisotropic profiles parallel to the slip direction have amplitudes about one order of magnitude lower than those perpendicular to the slip direction over most of the wavelength interval measured fault roughness perpendicular to the slip direction is similar to the roughness of natural joints the greater smoothness in the slip direction presumably represents wear resulting from slip combining our data with previous measurements of the roughness spectrum of the san andreas fault shows that fault surfaces are fractal over nearly eleven orders of magnitude in wavelength

thermal effects of ridge subduction and its implications for the origin of granitic batholith and paired metamorphic belts distribution of temperature and h2o in subduction zones during the course of ridge subduction are investigated numerically in order to constrain the timing and extent of metamorphism and melting within the subducting oceanic crust and the overlying arc crust the model assumes that after ridge subduction the two plates move together without creating a slab window the results suggest that before ridge subduction temperature along the subducting slab starts to rise when the slab is younger than 10 myr a drastic thermal impact occurs associated with subduction of the ridge crest followed by a diffusion stage of the impact the temperature elevation is limited within a few tens of kilometers from the slab crust interface and within 30 myr after ridge subduction although it will last for a longer period if a slab window is formed during the peak stage slab melting occurs and generates a significant amount of granitic melt mainly at depths shallower than 40 km at p t conditions corresponding to low p t metamorphism high p t metamorphism with a significant water flux is also achieved near the interface when a subducting slab is less than 10 myr old before ridge subduction or 20 myr old after ridge subduction consequently the low and high p t metamorphism accompanied by a significant amount of granitic melt is associated closely in time and space with the ridge subduction this model can explain the observed characteristics of the granitic batholith and the paired metamorphic belts through these processes arcs and continents can grow within the short period of time associated with the episodic subduction of ridges

the identification of an active fault by a multidisciplinary study at the archaeological site of sagalassos sw turkey abstract the archaeological site of sagalassos sw turkey is located in a region characterized by the absence of any significant recent seismic activity contrary to adjacent regions however the assessment of earthquake related damage at the site suggests that the earthquakes that have been demonstrated to have struck this pisidian city in ca ad 500 and in the middle or second half of the 7th century ad are characterized by an msk intensity of at least viii and occurred on a fault very close to the city different investigation techniques archaeoseismology remote sensing and geomorphology surface geology and structural data 2d resistivity imaging and palaeoseismological trenching have been applied at the archaeological site and its direct surroundings in search for the causative fault of these earthquakes this multidisciplinary approach shows that each of the different approaches independently provides only partial non conclusive information with respect to the fault identification integration is imperative to give a conclusive answer in the search for the causative fault this study has indeed revealed the existence of a to date unknown active normal fault system passing underneath ancient sagalassos i e the sagalassos fault a historical coseismic surface rupture event on this fault could be identified this event possibly corresponds to the devastating sagalassos earthquakes of ca ad 500 and the middle or second half of the 7th century ad finally this study demonstrates that in the particular geodynamic setting of sw turkey archaeological sites with extensive earthquake related damage form an important tool in any attempt to asses the seismic hazard

glaciological conditions in seven contrasting regions estimated with the degree day model we apply the degree day model to seven glacial regions that offer contrasting conditions and are well documented in the world glacier inventory the regions are axel heiberg island in arctic canada svalbard northern scandinavia southern norway the alps the caucasus and new zealand we estimate the average equilibrium line altitude ela for each half degree latitude longitude grid square from the median elevations of glaciers within the square and we extrapolate temperature from the uea cru climate research unit of the university of east anglia gridded climatology using the degree day model we calculate annual accumulation at the ela equal to ablation at the ela and other quantities like summer mean temperature length of melt season balance gradients and the sensitivity of mass balance to temperature and or precipitation changes glaciers can be characterized on a scale from cold dry axel heiberg island to warm wet new zealand corresponding to the contrast between maritime and continental climates mass balance sensitivities to temperature and or precipitation changes are relatively small for dry cold climate and relatively high for warm wet climate we could extend the approach to other glacier regions but we note that there are large areas for which ela data are not available as they are still not covered by the world glacier inventory

weathering history of an exposed bedrock fault surface interpreted from its topography abstract morphologic features of bedrock fault scarps are underutilized in studying faulting and weathering history partly because of a lack of accurate quantitative parameters for topography the study employs ground based lidar to measure five patches at different levels on the same fault surface and then calculates roughness in the form of power spectral density in directions parallel and perpendicular to the slip the power spectral density and spatial frequency typically follow a power law for each fault patch showing approximately linear relationships in a log log plot however due to additional power introduced by weathering all spectral curves especially those parallel to the slip can be divided into two segments lower frequency wavelengths of several centimeters several meters and higher frequency wavelengths of several centimeters and below domains this shows that the topographic features at different spatial scales are dominated by different mechanical processes faulting abrasion in the lower frequency domain and the weathering process in the higher frequency domain moreover we develop two parameters to quantify the degree of weathering of a fault outcrop which is significant to describe the evolution of the fault scarp and infer the date of faulting under calibration

quantitative morphology of bedrock fault surfaces and identification of paleo earthquakes the quantitative analysis of morphologic characteristics of bedrock fault surfaces may be a useful approach to study faulting history and identify paleo earthquakes it is an effective complement to trenching techniques especially to identify paleo earthquakes in a bedrock area where trenching technique cannot be applied in this paper we calculate the 2d fractal dimension of three bedrock fault surfaces on the huoshan piedmont fault in the shanxi graben china using the isotropic empirical variogram we show that the fractal dimension varies systematically with height above the base of the fault surface exposures indicating a segmentation of the fault surface morphology we interpret this segmentation as being due to different exposure duration of parallel fault surface bands caused by periodical earthquakes and discontinuous weathering we take the average of fractal dimensions of each band as a characteristic value to describe its surface morphology which can be used to estimate the exposure duration of the fault surface band and then the occurrence time of the earthquake that exposed the band combined with previous trenching results we fit an empirical relationship between the exposure duration and the morphological characteristic value on the fault d 0 049 t 2 246 the average width of those fault surface bands can also be regarded as an approximate vertical coseismic displacement of characteristic earthquake similar to the hongdong m8 earthquake of 1303 based on the segmentation of quantitative morphology of the three fault surfaces on the huoshan piedmont fault we identify three earthquake events the coseismic vertical displacement of the characteristic earthquake on the huoshan piedmont fault is estimated to be 3 4 m the average width of these fault surface bands gaps with a width of 0 1 0 3 m between two adjacent bands in which the fractal value increases gradually with fault surface height are inferred to be caused by weathering between two earthquakes or interseismic slip on the fault

image processing and roughness analysis of exposed bedrock fault planes as a tool for paleoseismological analysis results from the campo felice fault central apennines italy abstract morphologic investigations along the campo felice cf fault central apennines italy have been made in order to develop a procedure for the paleoseismological analysis of bedrock fault scarps the cf fault has been responsible for the formation of an impressive limestone fault scarp geomorphologic work on the cf basin and related fault indicated that the scarp originated from tectonic fault displacements three morphologic units have been distinguished along the fault scarp and defined as morphosome m1 lowest part of the scarp m2 and m3 the uppermost part these units display different karstic features which are the result of their different duration of exposure to weathering micromorphologic analyses focused on the morphosome m1 along which the cf fault plane is exposed for a height ranging between 4 and 7 m these analyses were aimed at defining differently weathered bands located at various heights and parallel to the fault scarp top and base the presence of these bands suggests repeated fault movements the exposed fault surface displays a low grade biokarstic weathering due to the action of epilithic and endolithic organisms the biokarst distribution is however inhomogeneous and conditioned by the presence of nourishing elements moisture and by light intensity an area preferentially affected by the biokarstic processes develops as a band at the bedrock soil contact at the base of the scarp roughness and colour analyses were made to identify uplifted bands which previously formed at the bedrock soil contact the roughness analysis was made using a microroughness meter along 20 cm long horizontal transects repeated each 20 cm of fault height for the entire morphosome m1 at various sites along the scarp the roughness variance data plotted vs the fault height failed to identify differently weathered bands of paleoseismological interest this result is probably due to the complex distribution of biokarst along the investigated fault plane more reliable results have been obtained by areal analysis of the variation of the colour rendering of the rocks exposed along the fault plane at different sites photographic images of large portions of fault surfaces have been processed with standard graphic computer programs the variations of colour indicated the presence of bands at various heights along the fault plane two uplifted bands have been recognised at all the investigated sites suggesting two displacement events e1 and e2 a preliminary chronological framework for these two events the youngest of which affected the cf fault can be derived from the paleoseismological data available for the southernmost branch of the regional fault system that includes the cf fault according to these data e1 may have occurred between 860 and 1300 ad while e2 may have occurred at about 1900 bc work is in progress to define surface exposure ages of different parts of the fault plane by means of in situ produced cosmogenic 36 cl this procedure will give further chronological constraints for the age of e1 and e2 and will also permit to test the validity of the micromorphologic analysis of bedrock fault scarps for paleoseismological aims

global glacier mass changes and their contributions to sea level rise from 1961 to 2016 glaciers distinct from the greenland and antarctic ice sheets cover an area of approximately 706 000 square kilometres globally1 with an estimated total volume of 170 000 cubic kilometres or 0 4 metres of potential sea level rise equivalent2 retreating and thinning glaciers are icons of climate change3 and affect regional runoff4 as well as global sea level5 6 in past reports from the intergovernmental panel on climate change estimates of changes in glacier mass were based on the multiplication of averaged or interpolated results from available observations of a few hundred glaciers by defined regional glacier areas7 10 for data scarce regions these results had to be complemented with estimates based on satellite altimetry and gravimetry11 these past approaches were challenged by the small number and heterogeneous spatiotemporal distribution of in situ measurement series and their often unknown ability to represent their respective mountain ranges as well as by the spatial limitations of satellite altimetry for which only point data are available and gravimetry with its coarse resolution here we use an extrapolation of glaciological and geodetic observations to show that glaciers contributed 27 22 millimetres to global mean sea level rise from 1961 to 2016 regional specific mass change rates for 2006 2016 range from 0 1 metres to 1 2 metres of water equivalent per year resulting in a global sea level contribution of 335 144 gigatonnes or 0 92 0 39 millimetres per year although statistical uncertainty ranges overlap our conclusions suggest that glacier mass loss may be larger than previously reported11 the present glacier mass loss is equivalent to the sea level contribution of the greenland ice sheet12 clearly exceeds the loss from the antarctic ice sheet13 and accounts for 25 to 30 per cent of the total observed sea level rise14 present mass loss rates indicate that glaciers could almost disappear in some mountain ranges in this century while heavily glacierized regions will continue to contribute to sea level rise beyond 2100 the largest collection so far of glaciological and geodetic observations suggests that glaciers contributed about 27 millimetres to sea level rise from 1961 to 2016 at rates of ice loss that could see the disappearance of many glaciers this century

on the thermal regime of an arctic valley glacier a study of white glacier axel heiberg island n w t canada from 1974 to 1981 a total of 32 bore holes was drilled on white glacier and vertical ice temperature profiles measured the data obtained allowed the construction of three longitudinal and four transverse profiles of the two dimensional temperature distributions thus an extensive layer of temperate or near temperate ice was discovered close to the bedrock in the lowest part of the glacier tongue it was also found that the temperature distribution cannot be in a steady state since there is a temperature minimum 100 150 m below the glacier surface in the accumulation area a simple numerical model calculation shows that this minimum can be mostly explained by the general climatic warming since 1880 the 10 m temperatures show diffuse relations to climatic conditions and balance zones a simple scheme for extrapolating surface temperatures is discussed

geodetic and direct mass balance measurements comparison and joint analysis this paper describes a new compilation of both direct and geodetic mass balance measurements develops a procedure to reduce diverse balance measurements over different time spans to common time spans and presents updated estimates of global average balance of small glaciers based on the enlarged compilation although geodetic measurements are fewer than direct measurements they cover four times as many balance years direct and geodetic measurements are unbiased with respect to one another but differences are often substantial the statistical procedure can be understood by imagining that an n year balance measurement is an average of a series of 1 year measurements the series is hypothetical but we can calculate the uncertainty of each of its elements if in addition to its measured average we can also estimate its standard deviation for this claim to be valid the annual series must be stationary and normally distributed with independent roughly uncorrelated elements for which there is reasonable evidence the need to know the standard deviation means that annual direct measurements from a nearby glacier or equally reliable information about variability are indispensable given this information the new methodology results in moderately more negative balances this is probably because tidewater glaciers are better represented in the geodetic data in any case the most recent published estimate of global average balance 0 8 1 0 mm a 1 of sea level equivalent for 2001 04 is now increased substantially to 1 1 1 4 mm a 1 for 2001 05

mass balance of the prince of wales icefield ellesmere island nunavut canada 1 this paper estimates the mass balance of the prince of wales icefield ellesmere island canada averaged over four decades from measurements of surface mass balance smb and iceberg calving shallow ice core net accumulation measurements and annual mass balance stake measurements are used in conjunction with a digital elevation model and knowledge of the location of the dominant moisture source for precipitation over the ice cap to interpolate and extrapolate spatial patterns of smb across the prince of wales icefield the contribution of iceberg calving to the mass balance is calculated from estimates of 1 the annual volume of ice discharged at the major tidewater glacier termini and 2 the annual volume loss or gain due to terminus fluctuations two different approaches to determining the smb conclude that the smb of the ice field is approximately in balance average equals 0 1 0 4 km3 w e a 1 where w e means water equivalent largely because of its proximity to the main year round moisture source that is the smith sound portion of the north open water polynya iceberg calving is a highly significant component of mass loss 1 9 0 2 km3 w e a 1 and is sufficient to make the overall mass balance of the ice field averaged over the period 1963 2003 clearly negative 2 0 45 km3 w e a 1 equivalent to a mean specific mass balance across the ice field of 0 1 m w e a 1 the prince of wales icefield contributes 0 005 mm a 1 to global eustatic sea level rise

dating quaternary fault scarps formed in alluvium using morphologic parameters abstract ages of fault scarps as well as those other types of transport limited slopes can be estimated by comparing their morphology with the morphology of scarps of known age age estimates are derived by fitting the scarp profiles to synthetic profiles generated using a diffusion equation or alternatively by classification using a linear discriminant function the usefulness of morphology derived age estimates depends on the relative importance of non age related morphologic variation data from more than 200 scarp profiles demonstrate that morphologic variation not related to scarp age can introduce significant uncertainties into morphology derived age estimates

surface mass balance of the ward hunt ice rise and ward hunt ice shelf ellesmere island nunavut canada 1 the ward hunt ice rise and ward hunt ice shelf located on ellesmere island canada are two of the northernmost land ice masses on the north american continent surface mass balance measurements excluding calving and subice processes began in 1959 on the ice rise and in 1966 on the ice shelf but were frequently interrupted most recently between 1986 and 2002 the surface balance of the ice rise and ice shelf follows the temporal pattern seen on other measured high arctic glaciers the overall surface mass losses over the last 45 years have been comparatively low 1 68 m water equivalent w eq for the ice rise and 3 1 m w eq for the ice shelf which reflects their proximity to the arctic ocean nevertheless the ice shelf appears to have weakened sufficiently in recent years to raise concerns about its possible disintegration in the near future the 2002 2003 balance year was the most negative year on record 0 33 m w eq for the ice rise and 0 54 m w eq for the ice shelf dynamical stresses related to wind wave and tidal action may further accelerate this process as open water conditions on the arctic ocean become more prevalent the ward hunt ice rise has so far remained in a reasonably healthy state in terms of its overall surface mass balance although its long term survival is also threatened by current and predicted future climatic conditions

quantifying the effects of climate and surface change on glacier mass balance when a mass balance is computed using an outdated map that computation does not reveal the actual mass change but older maps often must be used for practical reasons we present a method by which with a few additional measurements each year a mass balance computed with an outdated map can be transformed into an actual mass change this is done by taking into account the influence of changes in areal extent and changes in the surface elevation of the glacier since the map was made this method is applied to south cascade glacier washington u s a as an example the computed cumulative mass balance from 1970 to 1997 would have been 16 too negative if the 1970 map had not been updated while the actual volume change of a glacier is relevant to hydrological studies the change that would have occurred on a constant or static surface is more relevant to certain glacier dynamics problems and most climate problems we term this the reference surface balance and propose that such a balance which deliberately omits the influence of changes in area and surface elevation is better correlated to climatic variations than the conventional one which incorporates those influences

partial melting of subducting oceanic crust the conditions under which partial melting of subducting oceanic crust occurs can be determined by combining a partial melting model for basaltic compositions with two dimensional thermal models of subduction zones for porosities of 1 containing h20 the amount of partial melt generated at the wet basaltic solidus is limited to 100 mpa can be maintained by rocks close to or above their melting temperatures in the absence of high shear stresses substantial melting of the oceanic crust will only occur during subduction of very young 5 ma oceanic lithosphere partial melting of hydrated basalt amphibolites derived from the mid ocean ridge has been proposed e g 1 3 as being responsible for the generation of certain recent high al andesitic to dacitic volcanic rocks adakites three of these volcanic suites mount st helens southern chile and panama occur in volcanic arcs where oceanic crust 25 ma is being subducted at rates of 1 3 cm yr and the calculated thermal regime is several hundreds of degrees hotter than more typical subduction zone environments however oceanic lithosphere is not currently being subducted beneath baja and new guinea where recent adakites are also present suggesting that some adakite magmas may form by water undersaturated partial melting of underplated mafic lower crust or previously subducted oceanic crust further experimental work on compositions representative of oceanic crust is required to define the depth of possible adakite source regions more accurately

mass loss of greenland s glaciers and ice caps 2003 2008 revealed from icesat laser altimetry data 1 the recently finalized inventory of greenland s glaciers and ice caps gic allows for the first time to determine the mass changes of the gic separately from the ice sheet using space borne laser altimetry data corrections for firn compaction and density that are based on climatic conditions are applied for the conversion from volume to mass changes the gic which are clearly separable from the icesheet i e have a distinct ice divide or no connection lost 27 9 10 7 gt a 1 or 0 08 0 03 mm a 1 sea level equivalent sle between october 2003 and march 2008 all gic including those with strong but hydrologically separable connections lost 40 9 16 5 gt a 1 0 12 0 05 mm a 1 sle this is a significant fraction 14 or 20 of the reported overall mass loss of greenland and up to 10 of the estimated contribution from the world s gic to sea level rise the loss was highest in southeastern and lowest in northern greenland

geometry and kinematics of active normal faults south oquirrh mountains utah implication for fault growth the nnw striking south oquirrh mountains normal fault zone consists of four individual faults the individual faults are arranged in a right stepping pattern in the north and a left stepping pattern in the south forming a convex shaped fault zone in map view with the apex towards the hanging wall late quaternary fault activity is characterized by 2 0 4 5 m high discontinuous fault scarps developed in both late quaternary alluvium and bedrock the fault scarps in bedrock contain evidence of two large rupture events the last large earthquake occurred prior to the highstand of the bonneville lake cycle 15 ka based on cross cutting relationship between the bonneville shoreline and the fault scarp and on comparisons of fault scarp morphology cumulative displacement patterns inferred from range crest elevations bouguer gravity data in the adjacent basin and rotation of the subsidiary faults adjacent to the west mercur fault are similar to the pattern of displacements measured across late quaternary fault scarps that is the maximum displacement is near the apex of the convex shaped fault zone where the west mercur fault is located and then tapers off towards both ends of the fault zone fault traces that range from a few meters to tens of kilometers long are characterized by two dominant orientations strike n11 w and n43 w the two orientations are separated from each other by a statistically constant angle of 33 3 slip directions concentrate on a trend of s70 w for both groups of faults perpendicular to the average strike of the fault zone these data indicate that the geometry of the fault surfaces is non cylindrical and may be composed of self similar structural ridges and troughs of variable wavelength and amplitude that are elongated parallel to slip direction the relationships between fault geometry displacement and geomorphology in the south oquirrh mountains fault zone suggests a growth model of normal faults in which apex points on the convex shaped fault sections mark the nucleation points of primary faults secondary faults developed at the ends of the primary fault step into the footwall block as the fault zone grows laterally intersecting regions between two laterally growing fault zones are concave shaped in map view

mass balance of glaciers other than the ice sheets small glaciers appear to have been at equilibrium or shrinking very slightly during 1961 90 according to analysis of an essentially compl ete set of published measurements simple calculations give an average annual mass balance of 195 59 mm a 1 water equivalent but this is too low because of systema tic errors eglect of internal accumulation is respon sible for some tens of millime ters of under esti mate uneven spatial coverage with fewer measurements where mass balances are less negative accounts for about 50 mm a 1 of underestimate this figure derives from spatial interpolati on based on global data on ice extent and on an analysis of correlations between balance time series the eorrelogram shows exponential decay the scale length being about 600 km the largest bias is due to a newly detec ted dependence of mass balance on glacier size among the 231 measured glaciers many arc small and belong to a restricted size range in which balance is negativ e but much of the small glacier extent is accounted for by larger glac iers in a size range where balance is indisti ngui shable from zero correct ing for this size bias increases the average balance to 35 89 mm a i inspection of time series for 1940 95 251 glaciers shows that mass balance was least negative during the 1960s and has varied in broad agreementvith northern hemisphere temperature anomalies smaller small glaciers a 16 km2 appear to be more sensitive than larger small glaciers to changes in thermal forci ng the small glaci er contribution to sea level rise implied by this asse ssment is only 0 06 0 32 mm a i consistent with glaciers in general mak i ng little or no contri bution to sea level change during 1961 90

scales of structural heterogeneity within neotectonic normal fault zones in the aegean region abstract structural heterogeneities within neotectonic normal fault zones in the aegean region are important controls on the geomorphic expression of their uplifted footwall blocks contrasting fault rocks and slip plane phenomena corrugations comb fractures slip parallel fractures and pluck holes are responsible for mesoscopic inhomogeneities within fault scarps along strike disruptions in the continuity of fault scarps step over zones step up zones step down zones footwall cross faults and hangingwall cross faults are products of perturbations in slip plane geometry or intersections with transverse faults large scale variations in range front morphology reflect contrasting patterns of deformation within fault zones some major fault zones and many minor fault zones are characterized by a migration of the active slip plane towards the hangingwall resulting in a distributed network of high angle faults and a range front which is stepped in profile the presence of a localized mass of uneroded bedrock hangingwall salients protruding from the hangingwall of some major fault zones results in intense deformation along a principal slip plane and a range front which is ramp like in profile as a consequence of structural heterogeneities within neotectonic normal fault zones fault scarps and range fronts in the aegean region are subject to a temporally and spatially variable pattern of degradation

reprint of bedrock fault scarp history insight from t lidar backscatter behaviour and analysis of structure changes abstract this paper provides a research approach and develops a methodology that helps natural weathered bedrock fault scarps to be understood in terms of their structural changes and backscatter behaviour when using terrestrial laser scanning t lidar we tested our approach on the pisia fault in greece that ruptured during the 1981 alkyonides earthquake sequence in corinth gulf the method describes how to correlate fault geometry and structural variations with the backscatter signal of t lidar data from naturally exhumed bedrock fault scarps using this method we are able to reconstruct the past slip history we used t lidar for the analysis of the monochromatic laser beam s backscattered signal to define unsupervised classes of unknown objects on fault surface seven classes were created based on the dendrogram technique using the maximum likelihood method these were used to determine their spatial distribution throughout the scarp height and to calculate the terrain ruggedness index tri in the defined classes the combination of these results shows that i the ruggedness increases with the scarp height and ii the ruggedness and backscattering describe different fault plane conditions we found evidence for past earthquakes on the pisia fault at our study site with average displacements in the range of 30 60 cm with corresponding magnitudes of 6 4 6 6 0 1 ms these results help to reconstruct the recent fault history and potential palaeo events and can also be used i to detect appropriate sample sites on the fault plane for absolute dating and ii as an independent constraint on tracing slip events assisting absolute dating techniques this method can significantly reduce the sampling requirements and costs of cosmogenic absolute dating techniques overall it might be a valuable tool for extracting data regarding the faulting history and slip events for defining seismic hazard parameters

experimentally based water budgets for dehydrating slabs and consequences for arc magma generation phase diagrams of hydrous mid ocean ridge mor basalts to 330 km depth and of hydrous peridotites to 250 km depth are compiled for conditions characteristic for subduction zones a synthesis of our experimentally determined phase relations of chlorite lawsonite epidote zoisite amphibole paragonite chloritoid talc and phengite in basalts and of phase relations from the literature of serpentine talc chlorite amphibole and phase a in ultramafics permits calculation of h2o contents in hydrous phase assemblages that occur in natural compositions this yields the information necessary to calculate water budgets for descending slabs starting from low grade blueschist conditions 10 20 km depth with h2o contents between 5 and 6 wt for hydrated oceanic crust complete dehydration is achieved between 70 and 300 km depth as a function of individual slab geotherms hydrous phases which decompose at depth below volcanic arcs are lawsonite zoisite chloritoid and talc phengite in mafic compositions and chlorite and serpentine in peridotite approximately 15 35 of the initially subducted h2o are released below volcanic arcs the contribution of amphibole dehydration to the water budget is small 5 20 and occurs at relatively shallow depth 65 90 km in any predicted thermal structure dehydration is a combination of a stepwise and a continuous process through many different reactions which occur simultaneously in the different portions of the descending slab such a dehydration characteristic is incompatible with single phase dehydration models which focus fluid flow through a unique major dehydration event in order to explain volcanic fronts as a consequence of continuously progressing dehydration water ascending from the slab will be generally available to depth of ca 150 200 km the fluid rising from the subducting lithosphere will cause partial melting in the hot portion of the mantle wedge we propose that the volcanic front simply forms above the mantle wedge isotherm where the extent of melting is sufficient to allow for the mechanical extraction of parental arc magmas thermal models show that such an isotherm ca 1300oc locates below volcanic fronts slab surface depths below such an isotherm are compatible with the observed depths of the slab surface below volcanic fronts 1998 elsevier science b v all rights reserved

displacement history of a limestone normal fault scarp northern israel from cosmogenic 36cl the abundance of cosmogenic 36 cl measured in 41 limestone samples from a 9 m high bedrock fault scarp allows us to construct the 14 kyr fault displacement history of the nahef east normal fault northern israel 300 m above sea level n33 latitude the nahef east fault is one of a series of fault scarps located along the 700 m high zurim escarpment a major geomorphic feature samples at the top of the scarp have the highest nuclide concentrations 79 x 10 4 atoms g rock 1 samples at the base have the lowest 11 x 10 4 atoms g rock 1 using chemical data from the samples nahef east fault scarp geometry and surface and subsurface production rates for the 36 cl producing reactions we have constructed a numerical model that calculates 36 cl accumulation on a scarp through time given a series of unique displacement scenarios the resulting model 36 cl concentrations are compared to those measured in the scarp samples faulting histories that result in a good match between measured and modeled 36 cl abundances show three distinct periods of fault activity during the past 14 kyr with over 6 vertical meters of motion occurring during a 3 kyr time period in the middle holocene smaller amounts of displacement occurred before and after the period of most rapid motion the episodic behavior of the nahef east fault indicates that the average displacement rate of this fault system has varied through time

field estimate of paleoseismic slip on a normal fault using the schmidt hammer and terrestrial lidar methods and application to the hebgen fault montana usa

a rough guide to limestone fault scarps abstract the surface roughness of limestone fault scarps in central greece is examined with the aim of relating variations in rock weathering to palaeoseismic activity the study employs a micro roughness meter mrm and a carpenter s profile gauge to collect field measurements of scarp roughness presenting the results in terms of roughness indices which permit comparison between different height levels of a scarp the study confirms the increasing degradation of scarps with height thereby inferring the time dependent evolution of fault scarp roughness in addition roughness indices are found to discriminate between fault surfaces exposed during the 1981 corinth earthquakes and those emergent prior to this event

non planarity scale dependent roughness and kinematic properties of the pidima active normal fault scarp messinia greece using high resolution terrestrial lidar data abstract terrestrial lidar tls photogrammetric and field data were collected during the years 2014 2015 and 2017 at a 20 m long limestone scarp locality along the n s striking 70 west dipping active pidima fault messinia sw peloponnese greece this locality presents an artificially exhumed portion of an active fault plane thus providing a unique opportunity to study kinematics and limestone scarp morphology including its curvature and roughness the survey of 2015 offered a high density point cloud of the fault scarp with 6 mm working resolution creating a very close to real life representation 3d model we found that scarp geometry is non planar with increasing convexity up dip and increasing northwesterly dip directions from north towards south along strike non planarity is also recorded from the morphological data along strike with the appearance of several slip parallel troughs and ridges with a mean distance half wavelength of 0 75 m the fault plane roughness absolute values is scale dependent the roughness configuration attains a slip parallel pattern for observation scales above 1 cm at observations scales less than 1 cm a slip normal pattern is weakly visible the obtained tls results agree with field data manual compass measurements and macroscopic observations we infer an earthquake magnitude of 6 2 0 2 for the last event along the pidima fault based on the measured thickness of the smooth stripe that was imaged by t lidar along the non exhumed surface of the scarp

kinematic indicators on active normal faults in western turkey quaternary normal fault zones in western turkey comprise multiple slip planes and zone parallel layers of fault breccia they also contain several little known kinematic indicators that are probably typical of many formed at shallow levels in extending terrains the recent exhumation by contractors of about 2000 m2 of slip planes in a sse dipping fault zone separating quaternary colluvium from bedrock carbonates at yavansu 7 km se of kusadasi permits an unusually complete inventory of the indicators to be compiled the most spectacular indicators are metre scale 69 w pitching corrugations in slip planes and recemented breccia sheets underlying them corrugations characterized by sinusoidal profiles normal to their long axes and less commonly culminations and depression along their axes possibly developed as a result of upwards propagating slip planes seeking undemanding pathways through heterogeneous fault precursor breccias that formed in advance of tip lines parallel to corrugation long axes are those of gutters flat floored sleep sided channels a few centimetres wide probably related to the abrasion of subslip plane breccia sheets centimetre scale tool tracks scored in the uppermost subslip plane breccia sheet by resistant colluvial clasts are irregular at their proximal ends but distally they swing into alignment with corrugation axes frictional wear striae centimetres long but only a few millimetres wide and pitching 78 w are superimposed on the other slip parallel lineations comb fractures nearly perpendicular to slip planes define an intersection lineation which is normal to corrugation axes fault plane solutions of earthquakes on sse dipping active faults in the west anatolian extensional province indicate that mainly normal combined with minor dextral slip is the dominant mode a conclusion in accord with the sense of slip inferred from the indicators exposed on the yavansu slip planes

rock surface roughness as an indicator of degree of rock surface weathering rock surface weathering often leads to increased rock surface roughness but roughness has proved difficult to quantify several instruments are available for micro mapping and recording rock surface profiles but the most appropriate for most purposes is the simple profile gauge short profiles can be recorded quickly and accurately a range of roughness indices has been proposed in other areas of geomorphology and their efficacy as measures of roughness at scales of interest in studies of weathering is assessed some are too complex or labour intensive and others are too sensitive to the scale of roughness to provide reliable measures of magnitude the most appropriate indicator of both the scale and magnitude of roughness is the standard deviation of the differences between height values at a range of set horizontal intervals along a profile the deviogram varying the measurement interval records roughness at different scales a regression approach root mean square roughness provides a reliable measure of the magnitude of roughness at the maximum scale present three case studies confirm the efficacy of these approaches to studies of weathering of different rocks in different environments software is supplied which automates the calculation of roughness indices from gauge profiles

the randolph glacier inventory a globally complete inventory of glaciers the randolph glacier inventory rgi is a globally complete collection of digital outlines of glaciers excluding the ice sheets developed to meet the needs of the fifth assessment of the intergovernmental panel on climate change for estimates of past and future mass balance the rgi was created with limited resources in a short period priority was given to completeness of coverage but a limited uniform set of attributes is attached to each of the 198 000 glaciers in its latest version 3 2 satellite imagery from 1999 2010 provided most of the outlines their total extent is estimated as 726 800 34 000 km 2 the uncertainty about 5 is derived from careful single glacier and basin scale uncertainty estimates and comparisons with inventories that were not sources for the rgi the main contributors to uncertainty are probably misinterpretation of seasonal snow cover and debris cover these errors appear not to be normally distributed and quantifying them reliably is an unsolved problem combined with digital elevation models the rgi glacier outlines yield hypsometries that can be com bined with atmospheric data or model outputs for analysis of the impacts of climatic change on glaciers the rgi has already proved its value in the generation of significantly improved aggregate estimates of glacier mass changes and total volume and thus actual and potential contributions to sea level rise

petrology and geochemistry of metamorphosed komatiites and basalts from the sula mountains greenstone belt sierra leone the sula mountains greenstone belt is the largest of the late archaean greenstone belts in the west african craton it comprises a thick 5 km lower volcanic formation and a thinner 2 km upper metasedimentary formation komatiites and basalts dominate the volcanic formation and komatiites form almost half of the succession all the volcanic rocks are metamorphosed to amphibolite grade and have been significantly chemically altered two stages of alteration are recognised and are tentatively ascribed to hydrothermal alteration and later regional amphibolite facies metamorphism ratios of immobile trace elements and ree patterns preserve for the most part original igneous signatures and these are used to identify five magma types these are low ti komatiites depleted in light ree low ti komatiites with flat ree patterns high ti komatiitic basalts with flat ree low ti basalts depleted in light ree high ti basalts with flat ree patterns much of the variation between the magma types can be explained in terms of different melt fractions of the mantle source although there were two separate mantle sources one light ree depleted the other not the interleaving of the basalts and komatiites produced by this melting indicates that the two mantle sources were melted simultaneously the simplest model with which to explain these complex melting processes is during melting within a rising mantle plume in which there were two different mantle compositions the very high proportion of komatiites in the sula mountains relative to other greenstone belts suggests either extensive deep melting and or the absence of a thick pre existing crust which would have acted as a filter to komatiite eruption

magnesian andesites nb enriched basalt andesites and adakites from late archean 2 7 ga wawa greenstone belts superior province canada implications for late archean subduction zone petrogenetic processes magnesian andesites ma occur with normal tholeiitic to calc alkaline basalt andesite suites in four greenstone belts of the 2 7 ga wawa subprovince canada collectively the magnesian andesites span ranges of sio2 56 64 wt mg number 0 64 0 50 with cr and ni contents of 531 106 and 230 21 ppm respectively relative to normal andesites the magnesian andesites form distinct trends on variation diagrams with relatively high th and lree contents uniform yb over a range of mgo more fractionated hree and lower nb thpm and nb lapm ratios niobium enriched basalts and andesites neba nb 7 16 ppm and an al enriched rhyolite adakite suite are associated in space and time with the magnesian andesites nb enriched basalts and andesites are characterized by high tio2 p2o5 th and zr contents variably high zr hf 36 44 ratios and more fractionated hree gd ybcn 1 3 4 1 compared to the normal tholeiitic to calc alkaline basalt andesite suites the adakite suite has the high al al2o3 16 18 wt high la ybcn 21 43 and low yb 0 4 1 2 ppm of archean tonalite trondhjemite granodiorite ttg suites and cenozoic adakites indicative of liquids derived mainly from slab melting the basalt andesite suites are not characterized by normal tholeiitic or calc alkaline fractionation trends of major or trace elements rather compositional trends can be accounted for by some combination of fractional crystallization and variable degrees of metasomatism of the source of basalt and or andesites by adakitic liquids the occurrence of magnesian andesites nb enriched basalts andesites and adakites has been described from certain phanerozoic arcs featuring shallow subduction of young and or hot oceanic lithosphere adakites likely represent slab melts magnesian andesites the product of hybridization of adakite liquids with mantle peridotite and nb enriched basalts andesites melts of the residue from hybridization geological similarities between the late archean wawa greenstone belts and certain cenozoic transpressional orogens with the ma neba adakite association suggest that subduction of young hot oceanic lithosphere may have played an important role in the production of this arc related association in the late archean

sharply increased mass loss from glaciers and ice caps in the canadian arctic archipelago the canadian arctic archipelago contains one third of the global volume of land ice outside the ice sheets but its contribution to sea level change is largely unknown gardner et al use three independent techniques to reveal that mass loss from the archipelago was 92 12 gigatonnes per year in 2007 09 about three times greater than in 2004 06 and coincident with warmer summer temperatures the record is too short to allow a firm conclusion on longer term trends but it is clear that the canadian arctic archipelago is a significant contributor to sea level rise mountain glaciers and ice caps are contributing significantly to present rates of sea level rise and will continue to do so over the next century and beyond1 2 3 4 5 the canadian arctic archipelago located off the northwestern shore of greenland contains one third of the global volume of land ice outside the ice sheets6 but its contribution to sea level change remains largely unknown here we show that the canadian arctic archipelago has recently lost 61 7 gigatonnes per year gt yr 1 of ice contributing 0 17 0 02 mm yr 1 to sea level rise our estimates are of regional mass changes for the ice caps and glaciers of the canadian arctic archipelago referring to the years 2004 to 2009 and are based on three independent approaches surface mass budget modelling plus an estimate of ice discharge smb d repeat satellite laser altimetry icesat and repeat satellite gravimetry grace all three approaches show consistent and large mass loss estimates between the periods 2004 2006 and 2007 2009 the rate of mass loss sharply increased from 31 8 gt yr 1 to 92 12 gt yr 1 in direct response to warmer summer temperatures to which rates of ice loss are highly sensitive 64 14 gt yr 1 per 1 k increase the duration of the study is too short to establish a long term trend but for 2007 2009 the increase in the rate of mass loss makes the canadian arctic archipelago the single largest contributor to eustatic sea level rise outside greenland and antarctica

compositional changes of minerals associated with dynamic recrystallizatin the rate of compositional and isotopic exchange between minerals may be enhanced significantly if the rock is deformed simultaneously the enhanced exchange rate may result from a reduction in grain size shorter distance for volume diffusion dissolution and growth of grains by diffusion creep pressure solution or the movement of high angle grain boundaries through strained grains during recrystallization in the dislocation creep regime the migration of high angle grain boundaries provides high diffusivity paths for the rapid exchange of components during recrystallization the operation of the latter process has been demonstrated by deforming aggregates consisting of two plagioclases an1 and an79 at 900 c 1 gpa confining pressure and a strain rate of 2x10 6s 1 the polygonal recrystallized grains were analyzed using an analytical transmission electron microscope and have a variable but often intermediate composition at the conditions of these experiments the volume interdiffusion rate of nasi caal is too slow to produce any observable chemical change and microstructural chemical relations indicate that the contribution from diffusion creep was insignificant except for initially fine grained 2 10 m aggregates these results indicate that strain induced recrystallization can be an effective mechanism for enhancing the kinetics of metamorphic reactions and for resetting the isotope systematics of minerals such as feldspars pyroxenes and amphiboles

recent elevation changes of svalbard glaciers derived from icesat laser altimetry abstract we have tested three methods for estimating 2003 2008 elevation changes of svalbard glaciers from multi temporal icesat laser altimetry a linear interpolation of crossover points between ascending and descending tracks b projection of near repeat tracks onto common locations using digital elevation models dems and c least squares fitting of rigid planes to segments of repeat track data assuming a constant elevation change rate the two repeat track methods yield similar results and compare well to the more accurate but sparsely sampled crossover points most glacier regions in svalbard have experienced low elevation thinning combined with high elevation balance or thickening during 2003 2008 the geodetic mass balance excluding calving front retreat or advance of svalbard s 34 600 km2 glaciers is estimated to be 4 3 1 4 gt y 1 corresponding to an area averaged water equivalent w e balance of 0 12 0 04 m w e y 1 the largest ice losses have occurred in the west and south while northeastern spitsbergen and the austfonna ice cap have gained mass winter and summer elevation changes derived from the same methods indicate that the spatial gradient in mass balance is mainly due to a larger summer season thinning in the west and the south than in the northeast our findings are consistent with in situ mass balance measurements from the same period confirming that repeat track satellite altimetry can be a valuable tool for monitoring short term elevation changes of arctic glaciers

identifying past earthquakes on carbonate faults advances and limitations of the rare earth element method based on analysis of the spili fault crete greece abstract recent work carcaillet et al 2008 manighetti et al 2010 has utilised a well established earthquake record on a normal fault in italy the magnola fault to successfully test a new method for identifying paleoearthquakes on carbonate rocks that of chemical analysis of their exhumed fault planes here we take the next natural step applying this novel method on a notionally active normal fault in greece the spili fault for which no paleoearthquake record exists despite the blind sampling data reveal an outstanding record of systematic fluctuations in the concentrations of rare earth elements ree and yttrium y upscarp which closely resemble those recorded on the magnola fault chemical analysis of 35 core samples extracted from a 10 m high section of the exhumed spili fault plane records upscarp depletion in the ree y concentrations at an average rate of ca 9 3 m depletion is overprinted by locally increased ree y concentrations upscarp a minimum of four such concentration fluctuations with wavelengths ranging from 0 5 to 3 m are recorded each fluctuation is interpreted to be generated by at least one paleoearthquake that episodically exhumed a zone of the fault plane each zone consists of an upper domain that is enriched in ree y and a lower un enriched domain ree y enrichment is due to the prolonged at least few 100 s of years contact of the limestone with the soil whereas the un enriched domain reflects instantaneous uplift from depths greater than the base of the soil during the same earthquake the ree y analytical method cannot resolve individual small sized earthquakes with slip less than the thickness of the soil cover and or individual large and small sized earthquakes which are clustered in time repeat time

on the thermo kinetic consequences of slab melting 1 ree abundances in melts produced by partial melting of a hornblende bearing eclogite were examined using a dynamic disequilibrium melting model and following the p t path of a young subducting slab model calculations show that melts produced by small degrees of slab melting at 700 900 c are more likely affected by sluggish kinetics and have lower la yb ratios higher li2o and na2o abundances than melts produced by large degrees of melting at higher temperatures the extent of disequilibrium depends on deformation and melting histories of the slab and effective grain sizes and transport properties of the minerals the lree abundances in the large degree melts are broadly similar to those in adakites if kinetics is important in slab melting the degrees of melting required to generate adakites may be higher than values predicted by equilibrium partial melting models and ree abundances in the melts

revised estimates of recent mass loss rates for penny ice cap baffin island based on 2005 2014 elevation changes modified for firn densification repeat airborne or satellite measurements of surface elevation over ice caps are often used tocalculate glacier wide surface mass changes over time however these measurements typically do notacco

metastable mantle phase transformations and deep earthquakes in subducting oceanic lithosphere earth s deepest earthquakes occur as a population in subducting or previously subducted lithosphere at depths ranging from about 325 to 690 km this depth interval closely brackets the mantle transition zone characterized by rapid seismic velocity increases resulting from the transformation of upper mantle minerals to higher pressure phases deep earthquakes thus provide the primary direct evidence for subduction of the lithosphere to these depths and allow us to investigate the deep thermal thermodynamic and mechanical ferment inside slabs numerical simulations of reaction rates show that the olivine spinel transformation should be kinetically hindered in old cold slabs descending into the transition zone thus wedge shaped zones of metastable peridotite probably persist to depths of more than 600 km laboratory deformation experiments on some metastable minerals display a shear instability called transformational faulting this instability involves sudden failure by localized superplasticity in thin shear zones where the metastable host mineral transforms to a denser finer grained phase hence in cold slabs such faulting is expected for the polymorphic reactions in which olivine transforms to the spinel structure and clinoenstatite transforms to ilmenite it is thus natural to hypothesize that deep earthquakes result from transformational faulting in metastable peridotite wedges within cold slabs this consideration of the mineralogical states of slabs augments the traditional largely thermal view of slab processes and explains some previously enigmatic slab features it explains why deep seismicity occurs only in the approximate depth range of the mantle transition zone where minerals in downgoing slabs should transform to spinel and ilmenite structures the onset of deep shocks at about 325 km is consistent with the onset of metastability near the equilibrium phase boundary in the slab even if a slab penetrates into the lower mantle earthquakes should cease at depths near 700 km because the seismogenic phase transformations in the slab are completed or can no longer occur substantial metastability is expected only in old cold slabs consistent with the observed restriction of deep earthquakes to those settings earthquakes should be restricted to the cold cores of slabs as in any model in which the seismicity is temperature controlled via the distribution of metastability however the geometries of recent large deep earthquakes pose a challenge for any such models transformational faulting may give insight into why deep shocks lack appreciable aftershocks and why their source characteristics including focal mechanisms indicating localized shear failure rather than implosive deformation are so similar to those of shallow earthquakes finally metastable phase changes in slabs would produce an internal source of stress in addition to those due to the weight of the sinking slab such internal stresses may explain the occurrence of earthquakes in portions of lithosphere which have foundered to the bottom of the transition zone and or are detached from subducting slabs metastability in downgoing slabs could have considerable geodynamic significance metastable wedges would reduce the negative buoyancy of slabs decrease the driving force for subduction and influence the state of stress in slabs heat released by metastable phase changes would raise temperatures within slabs and facilitate the transformation of spinel to the lower mantle mineral assemblage causing slabs to equilibrate more rapidly with the ambient mantle and thus contribute to the cessation of deep seismicity because wedge formation should occur only for fast subducting slabs it may act as a parachute and contribute to regulating plate speeds wedge formation would also have consequences for mantle evolution because the density of a slab stagnated near the bottom of the transition zone would increase as it heats up and the wedge transforms to denser spinel favoring the subsequent sinking of the slab into the lower mantle

petrogenesis of a voluminous quaternary adakitic volcano the case of baru volcano the origin of adakite magmas remains controversial because initially the term adakite had petrogenetic significance implying an origin by direct melting of the eclogitized subducting oceanic crust many models have been produced for their origin and until now there has not been a straightforward method to discriminate between these models in a given adakite suite here we use detailed chronological and geochemical studies of selected adakitic edifices that allows for the determination of the magmatic output rate parameter qe which has been correlated with the rates of magma generation deep within subduction zones by providing temporal and eruption rate estimates we provide constraints on the possible petrogenetic processes involved in the generation of adakite like signatures adakite magmas derived from the melting of the subducting slab should be volumetrically insignificant when compared to the adakite like magmas produced by typical arc magma generation processes in this study we use this observation and the extraordinary stratigraphic exposure from miocene to present in an adakitic volcano in panama and to study the temporal and chemical variation in erupted magmas to estimate rates of magma generation detailed chemical and geochronological analyses of baru volcano indicate that the volcanic edifice was constructed in its entirety during the quaternary and magmas display adakite like features such as steep rare earth elements patterns pronounced depletions in the heavy rare earth elements low y high sr and high sr y the magmatic output rates qe that we have calculated show that compared to other typical adakitic volcanoes most of the volcanic edifice of baru volcano was constructed extremely rapidly 213 k a and in time frames that are similar to typical arc volcanoes the observed chemical and mineralogical variation coupled with the high magma production rates indicate that baru volcano is more representative of a typical arc volcano than a small volume melt of the subducting oceanic crust the technique we outline may have broader application in determining the petrogenetic conditions of other adakite suites