effects of deviatoric stress on undrained pore pressure response to fault slip the influence of deviatoric stress on coseismic water level changes is examined using an empirical relation between induced pore pressure and stress skempton 1954 characterized undrained pore pressure response in clayey soils to triaxial loading using two coefficients a and b the undrained pore pressure response under axial loading can be either larger a 1 3 or smaller a 1 3 than that predicted from the mean normal stress alone for indiana limestone the undrained pore pressure response under axial loading is characterized by a 1 3 skempton s equation is generalized to a polyaxial state of stress by making the undrained pore pressure a linear combination of the mean normal stress and the octahedral shear stress which is proportional to the square root of the second invariant of the deviatoric stress tensor dependence of the undrained pore pressure on the deviatoric stress components is consistent with coseismic water level changes observed on the trace of the fault plane near parkfield california for an a value less than 1 3 regions of pore pressure decrease are enlarged relative to regions of pore pressure increase

subsurface imaging of the garlock fault cantil valley california imaging of the garlock fault from seismic reflection data tests tectonic models for the mojave desert region of southern california models developed from geologic and geodetic evidence of fault movement rates disagree on whether the garlock fault should dip north or south such models are further at odds with focal mechanism and dislocation analyses consistent with a vertical strike slip fault our analysis demonstrates a nonvertical southward dip for the garlock fault consortium for continental reflection profiling mojave line 5 collected seismic reflection data across the garlock in cantil valley where the 3 km deep cantil pull apart basin has developed between the southwest and east branches of the fault we analyze the reflection data for evidence of the fault s structure to 5 km depths garlock fault plane reflections on unprocessed shot gathers merge with the first arrival as the source progresses to the surface trace of the east branch explicitly tracing the garlock fault as a seismic reflector from depth to the mapped contemporary fault trace the apparent velocity of these reflections gives a 37 10 south dip for the east branch of the fault a prestack kirchhoff sum migration images the east branch reflector with a 45 south dip our migration process fully accounts for the bending of seismic rays through the strong lateral velocity variations in cantil basin the south dip of the garlock s east branch together with basement steps that decrease to the south suggest that cantil basin developed from a 0 4 1 mm yr component of extension normal to the fault development of the basin by detachment provides a mechanism to widen it as left lateral motion lengthens it allowing the pull apart to maintain the globally constant length to width ratio of 3 detachment by the garlock at cantil valley similarly requires 0 4 1 mm yr of dextral strike slip on a northwest striking fault such as the helendale that cuts the mojave between the garlock and pinto mountain faults such motion is consistent with regional tectonic models

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

the formation of supraglacial debris covers by primary dispersal from transverse englacial debris bands glaciological controls on debris cover formation are investigated from the perspective of primary dispersal of supraglacial debris across a melting ice surface this involves the migration of angled debris septa outcrops across a melting thinning glacier ablation zone three measures of a glacier s ability to evacuate supraglacial debris are outlined 1 a concentration factor describing the focusing of englacial debris into specific supraglacial mass loads 2 the rate of migration of a septum outcrop relative to the local ice surface and 3 a downstream velocity differential between a slower septum outcrop and the faster ice surface velocity measures 1 and 2 are inversely related while measure 3 increases down glacier to explain why slow moving thinning ice rapidly becomes debris covered data from glacier d estelette italian alps are used to illustrate these processes and to explore the potential for debris cover formation and growth in different glaciological environments the transition from a clean transport dominated to a debris covered ablation dominated glacier is explained by the melting out of more closely spaced debris septa in combination with the geometric nteractions of angled septa and ice surface in a field of reducing flow and increasing ablation the growth and shrinkage of debris covers are most sensitive to glaciological changes at glaciers with gently dipping debris bearing foliation but less sensitive at high compression glaciers whose termini are constrained by moraine dams and other forms of obstruc tion these findings show that a variety of debris covered glacier types will show a spectrum of response characteristics to negative mass balance copyright 2013 john wiley sons ltd

accelerating shrinkage of patagonian glaciers from the little ice age ad 1870 to 2011 davies b j glasser n f 2012 accelerating shrinkage of patagonian glaciers from the little ice age similar to ad 1870 to 2011 journal of glaciology 58 212 1063 1084

topographic controls on glacier sediment landform associations around the temperate north patagonian icefield topographic controls on glacier sediment landform associations around the temperate north patagonian icefield

the evolution of the patagonian ice sheet from 35 ka to the present day patice abstract we present patice a gis database of patagonian glacial geomorphology and recalibrated chronological data patice includes 58 823 landforms and 1 669 geochronological ages and extends from 38 s to 55 s in southern south america we use these data to generate new empirical reconstructions of the patagonian ice sheet pis and subsequent ice masses and ice dammed palaeolakes at 35 ka 30 ka 25 ka 20 ka 15 ka 13 ka synchronous with the antarctic cold reversal 10 ka 5 ka 0 2 ka and 2011 ad at 35 ka the pis covered of 492 6 x103 km2 had a sea level equivalent of 1 496 mm was 350 km wide and 2090 km long and was grounded on the pacific continental shelf edge outlet glacier lobes remained topographically confined and the largest generated the suites of subglacial streamlined bedforms characteristic of ice streams the pis reached its maximum extent by 33 28 ka from 38 s to 48 s and earlier around 47 ka from 48 s southwards net retreat from maximum positions began by 25 ka with ice marginal stabilisation then at 21 18 ka which was then followed by rapid irreversible deglaciation by 15 ka the pis had separated into disparate ice masses draining into large ice dammed lakes along the eastern margin which strongly influenced rates of recession glacial readvances or stabilisations occurred at least at 14 13 ka 11 ka 6 5 ka 2 1 ka and 0 5 0 2 ka we suggest that 20th century glacial recession a 1 is occurring faster than at any time documented during the holocene

five decades of triggered earthquakes in koyna warna region western india a review abstract we review reservoir triggered seismicity rts in the koyna warna region of india since the impoundment of the koyna reservoir in 1962 until the year 2015 we include seismicity that occurred farther south in response to the impoundment of warna reservoir in 1993 about 35 km to the south of koyna reservoir the on going earthquake activity for more than five decades in a small seismic volume of about 30 20 10 km3 has characterized the koyna warna region as globally unique and significant to date 22 earthquakes of m 5 about 200 earthquakes of m 4 and several thousand smaller earthquakes have been recorded by a dense network of stations in the region various seismological geophysical and hydrological studies have been carried out to understand the phenomenon of triggered seismicity including source mechanism fault geometry crustal structure earthquake processes causal relationship with reservoir water level changes and anomalous water level fluctuations in cased bore wells the present review takes stock of all such studies undertaken so far to summarise the understanding on various geo scientific issues and milestone achievements with regard to mechanism of triggered seismicity and source processes fault plane solutions commensurate with geometry of faulting source parameters seismogenic depth crustal structure and the role of reservoir water level two stage increase in seismic energy release coinciding with peaks of annual filling and draining cycle of reservoir with one month delay vis a vis spurt of moderate earthquakes m 5 due to i rapid rise in reservoir level 12 m week ii reservoir water level exceeding the previous maxima and iii duration for which high reservoir level is retained are characteristic features numerical models simulating diffusion of pore fluid pressure fronts during the filling stage of reservoir suggest stress perturbations of the order of 0 75 2 25 bar at hypocentral depth triggering earthquakes on critically stressed pre existing faults in the year 2005 a 13 station digital seismometers network became functional that characterized the distribution of epicentres in the area with increased accuracy and suggested four major seismic zones with well defined clusters scientific drilling carried out recently provide several new information regarding the subsurface geology and structure in the koyna region such as i thickness of deccan traps 933 in the koyna area and 1185 m in the warna area ii presence of granite gneiss basement directly underlying the deccan traps iii absence of infratrappean sediments and iv temperature not exceeding 150 c at hypocentral depth it is planned to establish a deep borehole observatory close to the seismic source zone for direct measurements of physical and mechanical properties of rocks pore fluid pressure hydrology thermal condition and other parameters of an intra plate active fault zone in the near field of earthquakes before during and after their occurrence results from such experiment and long term in situ monitoring of critical parameters would enhance our understanding on the mechanism of triggered earthquakes and the role of reservoir water level fluctuations

debris transport in a temperate valley glacier haut glacier d arolla valais switzerland hambrey m j goodsell becky glasser n f 2005 debris transport in a temperate valley glacier haut glacier d arolla valais switzerland journal of glaciology 51 172 pp 139 146

contrasting patterns of early twenty first century glacier mass change in the himalayas glaciers are among the best terrestrial climate indicators an important water resource in mountains1 2 and a major contributor to global sea level rise3 4 in the hindu kush karakoram himalaya region hkkh a paucity of appropriate glacier data has prevented a comprehensive assessment of current regional mass balance5 however there are indirect evidences of a complex pattern of glacial responses5 8 in reaction to heterogeneous climate change signals9 here we provide the first coherent data set of detailed glacier thickness changes over the hkkh during 2003 2009 by combining satellite laser altimetry and a global elevation model in the eastern central and south western parts of the hkkh glacier wastage is widespread with regional thinning rates up to 0 66 0 09 m a 1 in the jammu kashmir region conversely in the karakoram glaciers are close to balance with only a slight thinning of 0 07 0 04 m a 1 regionally averaged thinning rates under debris mantled ice are similar to those of clean ice despite insulation by debris covers the 2003 2008 specific mass balance for our hkkh study region is 0 21 0 05 m a 1 water equivalent we significantly less negative than the global average of 0 7 m a 1 we for glaciers and ice caps4 10 this difference is mainly an effect of the balanced glacier mass budget in the karakoram the corresponding hkkh sea level contribution is 0 035 0 009 mm a 1 amounting to 1 of the present day sea level rise11 our 2003 2008 mass budget of 12 8 3 5 gt a 1 is more negative than recent satellite gravimetry based estimates of 5 6 gt a 1 over 2003 2010 ref 12 for the mountain catchments of the indus and ganges basins13 the glacier imbalance contributes 3 5 and 2 0 respectively to the annual average river discharge13 and up to 10 for the upper indus basin14

hydrologic effects on water level changes associated with episodic fault creep near parkfield california as part of the parkfield california earthquake prediction experiment water level is monitored in a well 460 m from the main trace of the san andreas fault on middle mountain in the preparation zone of the anticipated parkfield earthquake the well configuration allows water level to be monitored in two fluid reservoirs at depths of 85 and 250 m below land surface during 1987 water level changes were recorded during 12 of the 18 episodes of accelerated fault creep detected by a creep meter spanning the fault trace 750 m northwest of the well the creep related water level changes in the shallow reservoir have durations of less than 1 day whereas in the deeper reservoir the changes persist for as long as 2 months these data suggest that the transient nature of the water level changes in the shallow interval is due to vertical flow to the water table and is not evidence that creep events propagate past the well phase leads of earth tidal constituents in the water level data from the shallow interval relative to the same constituents in the local volume strain tide support the interpretation of significant flow to the water table at periods of 1 day or less the form of the water level changes in the deep interval is affected by horizontal flow to the well bore this effect can be removed from the water level records using a theoretical response curve constrained by the phases of earth tidal constituents in the deep interval relative to the local volume strain tide for the events where the signal in the shallow interval has been large enough to measure the sizes of the simultaneous water level changes in the two reservoirs are consistent with the same amounts of volume strain occurring at both depths

response of debris covered glaciers in the mount everest region to recent warming and implications for outburst flood hazards abstract in areas of high relief many glaciers have extensive covers of supraglacial debris in their ablation zones which alters both rates and spatial patterns of melting with important consequences for glacier response to climate change wastage of debris covered glaciers can be associated with the formation of large moraine dammed lakes posing risk of glacier lake outburst floods glofs in this paper we use observations of glaciers in the mount everest region to present an integrated view of debris covered glacier response to climate change which helps provide a long term perspective on evolving glof risks in recent decades debris covered glaciers in the everest region have been losing mass at a mean rate of 0 32 m yr 1 although in most cases there has been little or no change in terminus position mass loss occurs by 4 main processes 1 melting of clean ice close to glacier elas 2 melting beneath surface debris 3 melting of ice cliffs and calving around the margins of supraglacial ponds and 4 calving into deep proglacial lakes modelling of processes 1 and 2 shows that everest region glaciers typically have an inverted ablation gradient in their lower reaches due to the effects of a down glacier increase in debris thickness mass loss is therefore focused in the mid parts of glacier ablation zones causing localised surface lowering and a reduction in downglacier surface gradient which in turn reduce driving stress and glacier velocity so the lower ablation zones of many glaciers are now stagnant model results also indicate that increased summer temperatures have raised the altitude of the rain snow transition during the summer monsoon period reducing snow accumulation and ice flux to lower elevations as downwasting proceeds formerly efficient supraglacial and englacial drainage networks are broken up and supraglacial lakes form in hollows on the glacier surface ablation rates around supraglacial lakes are typically one or two orders of magnitude greater than sub debris melt rates so extensive lake formation accelerates overall rates of ice loss most supraglacial lakes are perched above hydrological base level and are susceptible to drainage if they become connected to the englacial drainage system speleological surveys of conduits show that large englacial voids can be created by drainage of warm lake waters along pre existing weaknesses in the ice roof collapses can open these voids up to the surface and commonly provide the nuclei of new lakes thus by influencing both lake drainage and formation englacial conduits exert a strong control on surface ablation rates an important threshold is crossed when downwasting glacier surfaces intersect the hydrological base level of the glacier base level lakes formed behind intact moraine dams can grow monotonically and in some cases can pose serious glof hazards glacier termini can evolve in different ways in response to the same climatic forcing so that potentially hazardous lakes will form in some situations but not others additionally the probability of a flood is not simply a function of lake volume but depends on the geometry and structure of the dam and possible trigger mechanisms such as ice or rockfalls into the lake satellite based measurements of glacier surface gradient and ice velocities allow probable future locations of base level lakes to be identified a base level lake has begun to grow rapidly on ngozumpa glacier west of mount everest and could attain a volume of 10 8 m 3 within the next 2 or 3 decades unless mitigation efforts are undertaken this lake could pose considerable glof hazard potential

spatially variable response of himalayan glaciers to climate change affected by debris cover the present state and future evolution of himalayan glaciers has been controversial an analysis of remotely sensed frontal changes and surface velocities from glaciers in the greater himalaya between 2000 and 2008 shows large regional variability in the responses of himalayan glaciers to climate change

classification of debris covered glaciers and rock glaciers in the andes of central chile in the dry andes of chile 17 to 35 s debris covered glaciers and rock glaciers are differentiated from true glaciers based on the percentage of surface debris cover thickness of surface debris and ice content internal ice is preserved by an insulating cover of thick debris which acts as a storage reservoir to release water during the summer and early fall these landforms are more numerous than glaciers in the central andes however the existing legislation only recognizes uncovered or semicovered glaciers as a water resource glaciers debris covered glaciers and rock glaciers are being altered or removed by mining operations to extract valuable minerals from the mountains in addition agricultural expansion and population growth in this region have placed additional demands on water resources in a warmer climate as glaciers recede and seasonal water availability becomes condensed over the course of a snowmelt season rock glaciers and debris covered glaciers contribute a larger component of base flow to rivers and streams as a result identifying and locating these features to implement sustainable regional planning for water resources is important the objective of this study is to develop a classification system to identify debris covered glaciers and rock glaciers based on the interpretation of satellite imagery and aerial photographs the classification system is linked to field observations and measurements of ice content debris covered glaciers have three subclasses surface coverage of semi class 1 and fully covered class 2 glaciers differentiates the first two forms whereas debris thickness is critical for class 3 when glaciers become buried with more than 3 m of surface debris based on field observations the amount of ice decreases from more than 85 to 65 85 to 45 65 for semi fully and buried debris covered glaciers respectively rock glaciers are characterized by three stages class 4 rock glaciers have pronounced transverse ridges and furrows that arch across the surface which indicates flow produced via ice class 5 rock glaciers have ridges and furrows that appear linear in the direction of flow indicating reduced flow from limited internal ice and class 6 rock glaciers have subdued surface topography because the movement of the rock glacier has ceased ice content decreases from 25 45 to 10 25 to 10 from class 4 to 6 respectively examples from digital imagery aerial photographs and field photographs are provided for each class the classification scheme can be used to identify and map debris covered glaciers and rock glaciers to create an inventory this will help improve recognition of these landforms as an important water resource in the dry andes of chile which will aid in sustainable planning and development in basins that hold the majority of the population and support a large share of the economic activity in chile

contribution of the patagonia icefields of south america to sea level rise digital elevation models of the northern and southern patagonia icefields of south america generated from the 2000 shuttle radar topography mission were compared with earlier cartography to estimate the volume change of the largest 63 glaciers during the period 1968 1975 2000 these glaciers lost ice at a rate equivalent to a sea level rise of 0 042 0 002 millimeters per year in the more recent years 1995 2000 average ice thinning rates have more than doubled to an equivalent sea level rise of 0 105 0 011 millimeters per year the glaciers are thinning more quickly than can be explained by warmer air temperatures and decreased precipitation and their contribution to sea level per unit area is larger than that of alaska glaciers

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

rock avalanches that travel onto glaciers and related developments karakoram himalaya inner asia abstract catastrophic rock slope failures in rugged terrain commonly generate rock avalanches when these occur in glacier basins the extent of landslide run out and its emplacement geometry are affected by movement over ice substantial modifications of glacier activity and sedimentation can follow ice activity leads to rapid modification transport and dispersal of landslide debris the nature of these interactions is described from observations over 20 years at bualtar glacier in the karakoram in august 1986 rock avalanches descended onto the ablation zone of the glacier their moisture content and patterns of deposition were affected by travel over ice glacier movement increased sharply at and below the rock avalanche deposits and within a few months the glacier surged a second surge occurred 2 years later major slope failures and debris flows were triggered beyond the ice margins and ponded melt water led to small outburst floods by 2005 the landslide material had been transported some 9 km about one third of this distance in the surges eventually it was fully reworked to become less readily distinguishable from other heavy supraglacial debris a large area of thickened ice persisted where the debris reduced ablation a positive impact on mass balance equivalent to a 20 increase in annual accumulation however it occurred as a moving segment of the ablation zone in 10 years it had in effect replaced the mass transferred in the surges data for the mid 1980s indicate the rock avalanches exceeded pre existing supraglacial debris by roughly five times and over a 30 year period will equal almost 500 years of normal supraglacial transport to the glacier margins other impacts of the episode suggest a doubling of this contribution to denudation similar developments were observed at three other glaciers where recent rock avalanches occurred and at twenty one prehistoric rock avalanches newly identified as having spread over glaciers it seems inadequate to treat such events only as singular extremes or the landslide and glacial processes separately here they are interpreted as contributing to disturbance regime landscapes whose history reflects episodic and regionally specific responses to strong interference among different earth surface processes they generate polygenetic deposits and landforms that are morphologically complex individual episodes involve decades to millennia their numbers and repetition can over ride or redirect geotectonic and climatic conditions it is suggested they are major but hitherto misread or neglected elements of landform evolution in the karakoram and perhaps in other high mountains

possible strain events reflected in water levels in wells along san jacinto fault zone southern california water levels have been monitored in wells along the san jacinto fault zone since 1977 the three largest earthquakes to occur within 30 km of the segment of the san jacinto fault zone being monitored with continuous recorders showed magnitudesm of 4 5 4 8 and 5 5 two wells in borrego valley 31 to 32 km southeast of them 5 5 earthquake on 25 february 1980 showed anomalous spikes recording a probable strain event 88 hours before the earthquake two other wells 12 km northwest of the epicenter showed no water level anomalies no water level anomalies preceded them 4 8 earthquake near anza on 15 june 1982 anomalous water level fluctuations occurred in a well near ocotillo wells 13 km northeast of them 4 5 earthquake on 22 march 1982 19 to 23 days prior to the earthquake similar fluctuations in other wells have not been followed by sizable earthquakes a simultaneous drop in water level occurred in four wells on 8 september 1982 this possible strain event was not associated with a sizable earthquake the presumed strain events occur only in wells that show earth tides and may have been the result of creep on strands of the san jacinto fault zone although water level anomalies have occurred in only one or two wells prior to two out of three moderate m 4 5 5 5 earthquakes the simultaneous drop in water level on 8 september 1982 and the spikes in two wells before them 5 5 earthquake on 25 february 1980 suggest that wells responsive to earth tides may detect strain events

a glacial lake outburst flood associated with recent mountain glacier retreat patagonian andes harrison s glasser n f winchester v haresign e warren c jansson k 2006 a glacial lake outburst flood associated with recent mountain glacier retreat patagonian andes the holocene 16 4 pp 611 620 sponsorship nerc grant ner b s 2002 00282 carnegie trust for the universities of scotland

the state of rock debris covering earth s glaciers rock debris can accumulate on glacier surfaces and dramatically reduce glacier melt the structure of a debris cover is unique to each glacier and sensitive to climate despite this debris cover has been omitted from global glacier models and forecasts of their response to a changing climate fundamental to resolving these omissions is a global map of debris cover and an estimate of its future spatial evolution here we use landsat imagery and a detailed correction to the randolph glacier inventory to show that 7 3 of mountain glacier area is debris covered and over half of earth s debris is concentrated in three regions alaska 38 6 of total debris covered area southwest asia 12 6 and greenland 12 0 we use a set of new metrics which include stage the current position of a glacier on its trajectory towards reaching its spatial carrying capacity of debris cover to quantify the state of glaciers debris cover is present on 44 of earth s glaciers and prominent 1 0 km2 on 15 of earth s glaciers 20 have a substantial percentage of debris cover for which the net stage is 36 and the bulk of individual glaciers have evolved beyond an optimal moraine configuration favourable for debris cover expansion use of this dataset in global scale models will enable improved estimates of melt over 10 6 of the global glacier domain a global map of rock debris cover on mountain glaciers shows its spatial distribution and evolution

ice motion of the patagonian icefields of south america 1984 2014 2015 american geophysical union all rights reserved we present the first comprehensive high resolution mosaic of ice velocity of the northern npi and southern patagonian icefields spi from multiple synthetic aperture radar and optical data collected between 1984 and 2014 the results reveal that many of the outlet glaciers extend far into the central ice plateaus which implies that changes in ice dynamics propagate far inside the accumulation area we report pronounced seasonal to interannual variability of ice motion on pio xi and jorge montt a doubling in speed of jorge montt a major slow down of o higgins significant fluctuations of upsala and a deceleration of san rafael which illustrate the need for sustained continuous time series of ice motion to understand the long term evolution of the rapidly thinning icefields the velocity product also resolves major ambiguities in glacier drainage in areas of relatively flat topography illustrating the need to combine topography and flow direction to map drainage basins

tectonic control on rock uplift exhumation and topography above an oceanic ridge collision southern patagonian andes 47 s chile

long term impact of the proglacial lake jokulsarlon on the flow velocity and stability of breiðamerkurjokull glacier iceland

analysis of water level changes induced by fault creep at parkfield california this paper demonstrates that the recovery rates of water level changes due to fault creep can be used to infer the position of the slipping zone relative to the well this technique is applied to five slip related water level changes observed in a well 460 m from the san andreas fault near parkfield california during january 1989 to july 1990 the water level changes are all characterized by a rapid drop in less than 8 hours and a slow recovery of 15 to 30 days the water level drop and the position of the well constrain right lateral slip to be predominantly to the southeast of the well the recoveries are modeled by pore fluid diffusion due to a plane strain dislocation in a porous fluid saturated elastic solid satisfactory agreement with the observations is obtained by assuming slip occurs instantaneously and extends indefinitely to the southeast of the well the extent of the slip northwest of the well which ranges from zero to 322 m is determined by fitting the variations in recovery times among the five events calculations are carried out for the limiting cases of both an impermeable and a permeable fault the permeability of the fault has little effect on inferences about the slip but the inferred horizontal diffusivity differs for the two cases 0 15 m2 s for the impermeable and 0 06 m2 s for the permeable for two of the events the magnitude and distribution of slip inferred from the water level changes agree well with that measured on two nearby creepmeters for a third event the agreement is moderately good discrepancies for the remaining two events suggest that the surface slip measured by the creepmeters may differ significantly from that near the 240 m depth of the well

earth fissures developed within collapsible loess area caused by groundwater uplift in weihe watershed northwestern china abstract earth fissures are geological hazards that frequently occur all over the world and greatly threaten the safety of people s property and lives this paper reports a case from a typical agricultural town in the weihe watershed northwest nw of china dali which has been severely affected from earth fissures in recent years a comprehensive survey was made on the geometric characteristics of the earth fissures developed in the study area through field investigations trial trenches boreholes exploratory wells and laboratory tests the study indicates that fourteen nearly parallel fissures have developed in the area with a fissure to fissure space of 140 350 m and a maximum length of any of the given fissures of 500 m the underlying faults loess joints and the quaternary unconsolidated and collapsible sedimentary loess provide a favorable geological condition for the occurrence of the earth fissures from 2003 to 2012 the groundwater level in the area rose about three meters due to agricultural irrigation and leakage of a water diversion canal collapsible deformation occurred in the loess while seepage erosion expanded the original joints in the soil the earth fissures occurred resulting from multiple geological environmental forces and human activities

mass balance changes of the debris covered glaciers in the langtang himal nepal from 1974 to 1999 thick debris cover on glaciers can significantly reduce ice melt however several studies have suggested that debris covered glaciers in the himalaya might have lost mass at a rate similar to debris free glaciers we reconstruct elevation and mass changes for the debris covered glaciers of the upper langtang valley nepalese himalaya using a digital elevation model dem from 1974 stereo hexagon satellite data and the 2000 srtm shuttle radar topography mission dem uncertainties are high in the accumulation areas due to data gaps in the srtm and difficulties with delineation of the glacier borders even with these uncertainties we obtain thinning rates comparable to those of several other studies in the himalaya in particular we obtain a total mass balance for the investigated debris covered glaciers of the basin of 0 32 0 18 m w e a 1 however there are major spatial differences both between glaciers and within any single glacier exhibiting a very distinct nonlinear mass balance profile with elevation through analysis of surface velocities derived from landsat etm imagery we show that thinning occurs in areas of low velocity and low slope these areas are prone to a general dynamic decay of surface features and to the development of supraglacial lakes and ice cliffs which may be responsible for a considerable increase in overall glacier ablation

experimental determination of a double valued drag relationship for glacier sliding the contribution of glaciers to sea level rise and their effects on landscape evolution depend on the poorly known relationship between sliding speed and drag at the ice bed interface results from experiments with a new rotary laboratory device demonstrate empirically for the first time a double valued drag relationship like that suggested by some sliding theories steady drag on a rigid sinusoidal bed increases peaks and declines at progressively higher sliding speeds due to growth of cavities in the lee sides of bed undulations drag decreases with increased sliding speed if cavities extend beyond the inflection points of up glacier facing surfaces so that adverse bed slopes in contact with ice diminish with further cavity growth these results indicate that shear tractions on glacier beds can potentially decrease due to increases in sliding speed driven by weather or climate variability promoting even more rapid glacier motion by requiring greater strain rates to produce resistive stresses although a double valued drag relationship has not yet been demonstrated for the complicated geometries of real glacier beds both its potential major implications and the characteristically convex stoss surfaces of bumps on real glacier beds provide stimulus for exploring the effects of this relationship in ice sheet models

catastrophic rock avalanches in a glaciated valley of the high atlas morocco 10be exposure ages reveal a 4 5 ka seismic event surface modification processes leading to large debris accumulations in high relief mountain areas are important for understanding landscape evolution especially in some of earth s most active orogens the arroumd rock avalanche at the foot of the nw face of mount aksoual 3912 m above sea level masl in the jebel toubkal area of the high atlas morocco represents one of the largest mass movement landforms in north africa the age and origin of this extensive feature have been contested for over a century late pleistocene moraines are also present in the same valley adjacent to the avalanche debris the mean of six 10 be cosmogenic exposure ages shows that a series of catastrophic rock slope failures occurred at 4 5 0 5 ka while a set of eight exposure ages from two of the three mapped moraines has a far larger spread from 1 5 to 7 5 ka this suggests that the avalanche events were effective agents in modifying the true surface exposure age of the pleistocene moraines in the arroumd valley this has resulted in similar mean 10 be apparent exposure ages for the preexisting late pleistocene moraine surfaces and holocene catastrophic rock slope failures similar rock avalanche deposits are present in other glaciated valleys in the high atlas we conclude that the trigger for collapse was seismic activity related to proximity of the major tizi n test fault these findings have important implications for interpreting and dating glacial landforms in tectonically active settings

pore pressure changes induced by slip on permeable and impermeable faults pore pressure changes due to a ramp introduction of slip on permeable and impermeable faults in a fluid saturated rock mass are calculated for the purpose of evaluating water well level fluctuations the calculations demonstrate the importance of coupling between deformation and fluid diffusion at observation points less than 5 4ct0 where c is the diffusivity and t0 is the rise time the decay of pore pressure in the results here is due entirely to fluid mass diffusion an approach that neglects diffusion and assumes that the pore pressure is proportional to the mean normal stress would predict a ramp pore pressure response at distances greater than 5 4ct0 the pore pressure decays so slowly that the neglect of diffusion may be appropriate for both permeable and impermeable faults the pore pressure decays more rapidly for shorter slip zone lengths and longer rise times however the pore pressure change calculated for the impermeable fault is larger particularly for observation points near the fault and decays less rapidly than for the permeable fault these differences suggest that fault permeability can be a significant factor in the response of water wells near faults and care should be used in inferring details of the slip distribution if hydrologic conditions are not known these results are applied to a water well level change observed by lippincott et al a satisfactory fit to the data is obtained by uniform slip over a fault length of about 1 5 km and a rise time of 8 hours although the slip magnitude is not well constrained by the fit the range of possible values includes the 0 5 to 1 0 cm inferred by lippincott et al using a different approach

spatial distribution of debris thickness and melting from remote sensing and meteorological data at debris covered baltoro glacier karakoram pakistan a distributed surface energy balance study was performed to determine sub debris ablation across a large part of baltoro glacier a wide debris covered glacier in the karakoram range pakistan the study area is 124 km 2 the study aimed primarily at analyzing the influence of debris thickness on the melt distribution the spatial distribution of the physical and thermal characteristics of the debris was calculated from remote sensing aster image and field data meteorological data from an automatic weather station at urdukas 4022 m a s l located adjacent to baltoro glacier on a lateral moraine were used to calculate the spatial distribution of energy available for melting during the period 1 15 july 2004 the model performance was evaluated by comparisons with field measurements for the same period the model is reliable in predicting ablation over wide debris covered areas it underestimates melt rates over highly crevassed areas and water ponds with a high variability of the debris thickness distribution in the vicinity and over areas with very low debris thickness 0 03 m we also examined the spatial distribution of the energy balance components global radiation and surface temperature over the study area the results allow us to quantify for the study period a meltwater production of 0 058 km 3

distribution and generative mechanisms of ground fissures in china abstract in this study 5002 ground fissures in more than 1500 localities across 22 provinces in china are investigated and mapped to reveal their spatial distribution the distribution of these ground fissures in china exhibits six regular patterns assemblages in north china syngenesis in extensional basins clustering along fault zones distributing along geomorphic boundaries developed on the edge of subsidence areas and clustering in large and medium sized cities combined with regional gps numerical simulations physical model test and in sar monitoring the generative processes of ground fissures are analyzed and discussed in relationship to four mechanisms 1 deep dynamic tectonism controls on the location of ground fissures 2 intracontinental dynamic tectonism resulting in ground fissure assemblages 3 fault stress inducing formation of ground fissures and 4 groundwater overmining resulting in the reactivation and expansion of ground fissures the geological environment is thus responsible for the establishment and appearance of ground fissure more importantly ground fissure propagation in china is the result of the synergistic effects of internal geological dynamic including in deep tectonism intracontinental tectoniim and fault movement coupled with anthropomorphic stress this genetic model can be summarized as one that is tectonically controlled stress driven and affected by regional hydrodynamic

groundwater flow records indicating earthquake occurrence and induced earth s free oscillations significant changes in groundwater flow were observed immediately before and after an earthquake with m 6 6 occurred on march 18 1987 in southwest japan the groundwater flow from a deep borehole well 226 km northeast of the epicenter had begun to increase slightly 15 minutes before the earthquake just after the shock the flow rate increased rapidly and exponentially approached a constant but there were still oscillatory fluctuations even 5 hours later the fluctuations correspond to 0s2 and 0s3 spheroidal modes of free oscillations of the earth the non oscillatory transient flow must be the response to the residual field and or to some non recoverable deformation of the groundwater reservoir resulting from strong ground motions due to seismic waves caused by the earthquake fault model calculations however indicate that the residual strain effect on the transient flow change is unimportant the preseismic flow increase indicates a change in regional stress field preceding the earthquake the present observations illustrate that groundwater responds systematically to minute crustal deformations just before and after an earthquake

rock glaciers and the geomorphological evolution of deglacierizing mountains abstract rock glaciers are an important geomorphic element of glaciated mountain landscapes but our understanding of their distribution and ages controls on their development and their importance in regional mountain hydrology and mountain geomorphic evolution is incomplete in part this incomplete knowledge arises through problems associated with identifying rock glaciers on a morphological basis alone amplified by the multiple ways in which rock glaciers can form in different glacial periglacial and paraglacial settings this study focuses on rock glaciers as a paraglacial mountain landscape element and considers the relationships between rock glaciers and glacial periglacial and paraglacial processes new geomorphic and sedimentary data on different rock glaciers from the khumbu region of nepal are presented these data show that even within a single region rock glaciers may have varied origins and thus likely ages and different climatic and environmental controls we argue that rock glaciers in deglacierizing mountains may have a long residence time in the landscape unlike many other glacially influenced mountain landforms and can undergo significant morphodynamic changes as glaciated landscapes transition into paraglacial landscapes

effect of non migrating bars on dune dynamics in a lowland river as dunes and larger scale bed forms such as bars coexist in rivers the question arises whether dune dynamics are influenced by interaction with the underlying bed topography the present study aims to establish the degree in which dune characteristics in two and three dimensions are influenced by an underlying topography dominated by non migrating bars as a case study a 20km stretch in the waal river in the netherlands is selected which represents a sand bed lowland river at this location longitudinal training dams ltds have recently been constructed to ensure sufficient navigation depth during periods with low water levels and to reduce flood risk by using data covering two year long periods before and after ltd construction the robustness of the results is investigated before ltd construction dune characteristics show large variability both spatially and temporally with dunes being longer lower less steep and having a lower lee side angle when they are located on bar tops the correlation between dune characteristics and the underlying bed topography is disrupted by unsteady conditions for which the dunes are in a state of transition the bar pattern causes tilting of dune crest lines which may result from a transverse gradient in bed load sediment transport as a result of ltd construction the hydraulic and morphological conditions have changed significantly despite this the main conclusions still hold which strengthens the validity of the results

age and nature of paraglacial debris cones along the margins of the san rafael glacier chilean patagonia this study employs sedimentological indices and lichenometric dating on the lichen species plac opsis patagonica to investigate the nature and age of debris cones which have accumulated at the margins of the downwasting san rafael glacier in chilean patagonia these cones appear to have accumulated by the resedimentation of glacigenic deposits by debris flows with debris movement starting in the early 1980s cone activity follows a pattern of intense initial activity and sediment mobilisation followed by increased stability and colonization by vegetation three of the four cones had stabilized within 15 years of sediment movement initiation these features may be seen as being conditioned by glacial activity with second order controls provided by the local climate and sediment supply the cones have accumulated in a paraglacial environment

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

earth fissures and localized differential subsidence long linear tension cracks associated with declining groundwater levels at four sites in subsiding areas in south central arizona fremont valley california and las vegas valley nevada occur near points of maximum convex upward curvature in subsidence profiles oriented perpendicular to the cracks profiles are based on repeated precise vertical control surveys of lines of closely spaced bench marks association of these fissures with zones of localized differential subsidence indicates that linear earth fissures are caused by horizontal tensile strains probably resulting from localized differential compaction horizontal tensile strains across the fissures at the point of maximum convex upward curvature ranging from approximately 100 to 700 microstrains 0 01 to 0 07 per year were indicated based on measurements with a tape or electronic distance meter

sedimentological geomorphological and dynamic context of debris mantled glaciers mount everest sagarmatha region nepal abstract this paper presents the sediment landform and dynamic context of four avalanche fed valley glaciers khumbu imja lhotse and chukhung in the mount everest sagarmatha region of nepal all four glaciers have a mantle of debris dominated by sandy boulder gravel that suppresses melting to an increasing degree towards the snout leading to a progressive reduction in the overall slope of their longitudinal profile prominent lateral terminal moraine complexes also comprising sandy bouldergravel enclose the glaciers these terminal moraines originally grew by accretion of multiple sedimentary facies of basal glacial and supraglacial origin probably by folding and thrusting when the glaciers were more dynamic during the little ice age the four glaciers are in various stages of recession and demonstrate a range of scenarios from down wasting of the glacier tongue through morainedammed lake development to post moraine dam breaching khumbu glacier is at the earliest stage of supraglacial pond formation and shows no sign yet of developing a major lake although one is likely to develop behind its 250 m high composite terminal moraine imja glacier terminates in a substantial body of water behind a partially ice cored moraine dam as determined from geophysical surveys but morphologically appears unlikely to be an immediate threat chukhung glacier already has a breached moraine and a connected debris fan and therefore no longer poses a threat lhotse glacier has an inclined free draining tongue that precludes hazardous lake development from the data assembled a conceptual model applicable to other himalayan glaciers is proposed to explain the development of large lateral terminal moraine complexes and associated potentially hazardous moraine dams 2008 elsevier ltd all rights reserved

assessing linkages between spatial facies changes and dimensional variations of glaciers in the upper indus basin western himalaya abstract the present study provides an insight into the heterogeneous response of 45 glaciers in the lidder and sindh river basins western himalaya and explores the linkages between glacier facies variability and changing glacier parameters results show that the region has undergone an overall deglaciation of 12 1 5 11 9 1 4 km 2 from 1996 to 2014 fluctuations in the temperature and precipitation patterns seem to be the primary factor controlling the changes in glacier dimensions r 2 0 82 in all cases glacier facies changes suggest depletion in snow ice cover 18 2 3 and an increase in ice mixed debris 4 1 4 supraglacial debris 6 1 5 and periglacial debris 17 1 2 these glacier facies transitions are possibly the result of ice melting however its relative rate and elevation decides the nature of facies conversion an increase in the proportion of supraglacial debris has led to the conversion of 11 clean glaciers to sparsely debris covered glaciers and 5 sparsely debris covered glaciers to debris covered glaciers the size of the glaciers greatly influenced the rate of conversion of glaciers and glaciers 2 dominated the others in this regard the small glaciers also experienced maximum shrinkage further the glaciers with varying supraglacial debris cover respond differently as sparsely debris covered glaciers exhibit the highest rates of retreat 25 7 3 m y followed by clean 23 7 7 3 m y and debris covered glaciers 13 1 7 3 m y thus the findings of this work clearly show that the climate change driven dimensional changes of glaciers and variations in the spatial distribution of glacier facies have strong mutual control on each other

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

combining satellite multispectral image data and a digital elevation model for mapping debris covered glaciers automated glacier mapping from satellite multispectral image data is hampered by debris cover on glacier surfaces supraglacial debris exhibits the same spectral properties as lateral and terminal moraines fluvioglacial deposits and bedrock outside the glacier margin and is thus not detectable by means of multispectral classification alone based on the observation of low slope angles for debris covered glacier tongues we developed a multisource method for mapping supraglacial debris the method combines the advantages of automated multispectral classification for clean glacier ice and vegetation with slope information derived from a digital elevation model dem neighbourhood analysis and change detection is applied for further improvement of the resulting glacier debris map a significant percentage of the processing can be done automatically in order to test the sensitivity of our method against different dem qualities it was also applied to a dem obtained from aster stereo data additionally we compared our multisource approach to an artificial neural network ann classification of debris using only multispectral data while the combination with an aster derived dem revealed promising results the ann classification without dem data does not

ice sheet growth under dirty conditions implications of debris cover for early glaciation advances abstract debris covered glaciers respond differently to any given set of climatic conditions than clean glaciers this difference stems from change in ablation rate caused by a debris cover approaching zero ablation with sufficiently thick protective cover a mechanism not yet considered in the context of ice sheet growth critical to applying the mechanism to ice sheets is supply of debris we postulate that periods after major interglacials offer the best conditions for dirty advances this is because the volume of debris previously deposited and weathered in interglacial time the latter a function of exposure length should be at a maximum advances of dirty ice sheets generate landforms and in positions deviating from clean ice advances under similar climatic conditions hence inferences of both ice sheet properties inferred from such dirty ice advances and the climate conditions related to such advances must be cautious furthermore modeling of past ice sheets must consider the effect of debris cover whenever indications exist for such a cover

dynamics of fault creep observations along the surface traces of active faults in california and elsewhere indicate that tectonic displacement can occur as seismic slip or as aseismic fault creep fault creep occurs as secular displacement and as displacement episodes called creep events which last a few hours to days and include from a millimeter or less to a few tens of millimeters of displacement instrumental measurements of displacement versus time during creep events show that many events have a characteristic simple form including a steep beginning followed by a gradual decay in the rate of displacement some creep events display small amounts of precursory slip and many seem to be composed of several discrete simple events propagation of creep events along the san andreas calaveras and imperial faults in california has been inferred from the nearly simultaneous observation of creep events at nearby creepmeters and from kinematic modeling of continuous measurements of strain during creep events fault creep can be viewed as arising from the interplay of three factors stress applied to the fault from external sources stress caused by the geometry and distribution of displacement on the fault arising from the elastic response of the surrounding medium to the displacements within the anelastic fault zone itself and the constitutive relations characterizing the resistance to slip on the fault analytic solutions are presented for a simple rectangular dislocation quasi static model of nonpropagating fault creep assuming viscous and quasi plastic power law creep fault zone rheology and for a multi element composed of several rectangular or striplike dislocation surfaces quasi static model assuming a viscous rheology viscous rheology implies solutions composed of exponentials that decay with time the simple one element quasi plastic model is in agreement with the form of creep events observed at melendy ranch california a matrix formulation is presented to calculate dislocation stresses on a fault zone in a half space or plate the formulation involves the division of the dislocation surface into strips or rectangles and the use of published solutions to calculate the stress resulting from displacement on each individual element results from the matrix method agree with analytic results for equilibrium displacements on stress free cracks the matrix formulation is then used as the basis for a numerical method to simulate one and two dimensional propagating creep assuming a quasi plastic rheology on the fault zone results from this method agree reasonably well with observations of afterslip from the 1966 parkfield 1975 oroville and 1979 imperial valley california earthquakes and of a propagating creep event observed along the southern calaveras fault central california during july 1977 this method of analysis and the assumption that creep at each point on the fault zone follows a power law rheology after the applied stress reaches a spatially varying yield stress can explain the secular and episodic nature of fault creep afterslip the simple shape of some individual events and the multiple composite shape of others and the propagation of creep events on the southern calaveras fault observations of propagating creep indicate a yield stress near zero at the surface and throughout much of the fault zone however they also indicate the presence of a zone at a depth of about 0 5 km and about 5 km long with a yield stress of about 15 bars 1 5 mpa the methods of solution presented here should be applicable to many problems in the dynamics of faulting

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

modelling the feedbacks between mass balance ice flow and debris transport to predict the response to climate change of debris covered glaciers in the himalaya many himalayan glaciers are characterised in their lower reaches by a rock debris layer this debris insulates the glacier surface from atmospheric warming and complicates the response to climate change compared to glaciers with clean ice surfaces debris covered glaciers can persist well below the altitude that would be sustainable for clean ice glaciers resulting in much longer timescales of mass loss and meltwater production the properties and evolution of supraglacial debris present a considerable challenge to understanding future glacier change existing approaches to predicting variations in glacier volume and meltwater production rely on numerical models that represent the processes governing glaciers with clean ice surfaces and yield conflicting results we developed a numerical model that couples the flow of ice and debris and includes important feedbacks between debris accumulation and glacier mass balance to investigate the impact of debris transport on the response of a glacier to recent and future climate change we applied this model to a large debris covered himalayan glacier khumbu glacier in nepal our results demonstrate that supraglacial debris prolongs the response of the glacier to warming and causes lowering of the glacier surface in situ concealing the magnitude of mass loss when compared with estimates based on glacierised area since the little ice age khumbu glacier has lost 34 of its volume while its area has reduced by only 6 we predict a decrease in glacier volume of 8 10 by ad2100 accompanied by dynamic and physical detachment of the debris covered tongue from the active glacier within the next 150 yr this detachment will accelerate rates of glacier decay and similar changes are likely for other debris covered glaciers in the himalaya

global sea level contribution from the patagonian icefields since the little ice age maximum the melting of mountain glaciers and ice caps is expected to contribute significantly to sea level rise in the twenty first century 1 3 although the magnitude of this contribution is not fully constrained glaciers in the patagonian icefields of south america are thought to have contributed about 10 of the total sea level rise attributable to mountain glaciers in the past 50 years 3 however it is unclear whether recent rates of glacier recession in patagonia are unusual relative to the past few centuries here we reconstruct the recession of these glaciers using remote sensing and field determinations of trimline and terminal moraine location we estimate that the north patagonian icefield has lost 103 20 7 km 3 of ice since its late holocene peak extent in ad 1870 and that the south patagonian icefield has lost 503 101 1 km 3 since its peak in ad 1650 this equates to a sea level contribution of 0 0018 0 0004 mm yr 1 since 1870 from the north and 0 0034 0 0007 mm yr 1 since 1650 from the south the centennial rates of sea level contribution we derive are one order of magnitude lower than estimates of melting over the past 50 years 3 even when we account for possible thinning above the trimline we conclude that the melt rate and sea level contribution of the patagonian icefields increased markedly in the twentieth century

a new model of rock glacier dynamics abstract rock glaciers have traditionally been described as periglacial landforms and thus associated genetically with the presence of permafrost and a seasonal active layer they have also been described as glacigenic in origin in which the main rock glacier body contains glacier ice at depth other rock glaciers can be considered as relict where they contain no interstitial ice and are functionally inactive although all rock glaciers are to some extent polygenic there is no clear simple test that can be used to distinguish between different rock glacier types this study proposes a simple and testable model for rock glacier classification based on their behaviour from evidence reported from the literature the study then proposes an interpretive evolutionary model describing the temporal evolution of rock glacier surface movement through the year that can inform on its dynamical controls this analysis provides an easily deployed interpretive framework for the origins of rock glaciers

ultra low frequency electromagnetic measurements associated with the 1998 mw 5 1 san juan bautista california earthquake and implications for mechanisms of electromagnetic earthquake precursors abstract ultra low frequency ulf 0 01 10 hz magnetic field anomalies prior to m 6 0 earthquakes have been reported in various regions of the world here we test whether smaller magnitude earthquakes have associated ulf anomalies by using continuous measurements made 9 km above and 2 km ne of the epicenter of the m w 5 1 8 12 98 san juan bautista ca earthquake half hour spectral averages of the magnetic field data in nine different ulf frequency bands show no long term days to weeks magnetic field anomaly prior to the earthquake in addition magnetic and electric field polarization shows no anomalous behavior clearly associated with seismic activity an 0 02 nt increase in activity for 2 h prior to the earthquake is close to the background noise levels precluding identification of a precursor we present scaling calculations to show if precursory ulf anomalies are related to the size of the earthquake the observed 0 02 nt increase is the approximately expected magnetic anomaly prior to the san juan bautista sbj earthquake based on the anomaly observed prior to the 1989 loma prieta lp earthquake our reexamination of previously proposed dilatant conductive and piezomagnetic mechanisms for ulf precursors shows that these effects are consistent with the observations prior to the sjb earthquake based on the observations i e lack of a strong precursor in contrast previously proposed electrokinetic and magnetohydrodynamic mhd mechanisms do not appear to be appropriate for this particular earthquake this analysis further supports the hypothesis that precursory ulf signals are related to the size of the earthquake

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

ice loss rates at the northern patagonian icefield derived using a decade of satellite remote sensing abstract we use a satellite based survey of glacier surface elevation changes speeds and surface melt conditions between 2000 and 2011 to quantify mass loss from the northern patagonian icefield npi chile a history of ice elevation change is found by differencing aster digital elevation models dems relative to a void filled version of the dem collected by the shuttle radar topography mission srtm in february 2000 thinning rates have accelerated at lower elevations while above the equilibrium line altitude ela recent thinning rates are not significantly different from those observed in previous studies a volumetric change of 4 06 0 11 km 3 yr is found by summing surface elevation changes over all glaciers in the npi this is regarded as a lower bound because volume loss due to frontal retreat and sub aqueous melting is not included this volume change is converted to a mass loss of 3 40 0 07 gt yr taking into account density differences above and below the equilibrium line we find that the npi is providing at least 0 009 0 0002 mm yr to ongoing sea level change in agreement with previous estimates sub pixel offset tracking of aster image pairs is used to produce glacier displacements over intervals typically ranging from 6 days to 18 months the first whole icefield composite velocity map is presented the terminus of the san rafael glacier on the western side of the npi sustained a peak calving front speed of 19 7 1 2 m day for 7 days in the austral fall of 2007 passive microwave observations indicate that the surface of the accumulation basin of the glacier was wet during this period of rapid motion suggesting that the fast speed may be a consequence of a rise in sub glacial water pressure sourced from melt or rainwater making its way to the glacier bed and reducing basal friction several other outlet glaciers including the benito and hpn1 glaciers on the isolated western side of the icefield accelerated while thinning between 2007 and 2011 marked acceleration also occurred after 2007 at the front of the san quintin glacier the largest outlet glacier of the npi the paucity of thickness measurements at the outlet glaciers means it is impossible to accurately gauge the mass flux of the icefield and thus give a full estimate of the mass balance

planimetric and volumetric glacier changes in the khumbu himal nepal since 1962 using corona landsat tm and aster data multitemporal space imagery from 1962 corona kh 4 1992 landsat tm 2001 and 2005 terra aster was used to investigate the glacier changes in the khumbu himal nepal the ice coverage in the investigation area decreased by about 5 between 1962 and 2005 with the highest retreat rates occurring between 1992 and 2001 the debris coverage increased concomitantly with the decrease in total glacier area the clean ice area decreased by 10 digital terrain model dtm generation from the early corona kh 4 stereo data in this high relief terrain is time consuming and the results still contain some elevation errors however these are minor in the snow free areas with gentle slopes thus comparison of the surfaces of the debris covered glacier tongues based on the corona dtm and an aster dtm is feasible and shows the downwasting of the debris covered glaciers the highest downwasting rates more than 20 m 0 5 m a 1 can be found near the transition zone between the active and the stagnant glacier parts of the debris covered glacier tongues the downwasting is lower but still evident in the active ice areas and at the snout with thick debris cover all investigated debris covered glaciers in the study area show similar behaviour the estimated volume loss for the investigated debris covered glacier tongues is 0 19 km 3

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

effects of rock avalanches on glacier behaviour and moraine formation although large rock avalanches are infrequent sediment production in active orogens is dominated by such events which may strongly influence geomorphic processes where rock avalanches fall onto glaciers they may affect glacier behaviour and moraine formation we outline the processes of rock avalanche initiation and motion and show that supraglacial deposits of rock avalanche debris have distinct sedimentological and thermal properties laboratory experiments on the effects of such debris on ice ablation are supplemented by field data from two rock avalanches in the southern alps new zealand their effects are compared with those of the thinner supraglacial debris that results from small rockfalls and melt out of englacial debris implications of rock avalanche debris cover for glacier behaviour are explored using a mass balance model of the franz josef glacier in new zealand demonstrating a likely supraglacial rock avalanche origin for the waiho loop moraine and considering the potential hazard of a large rock avalanche onto the present day glacier

recent movement on the garlock fault as suggested by water level fluctuations in a well in fremont valley california water levels have been continuously recorded since march 1978 in a well in fremont valley where several strands of the adjacent garlock fault zone have exhibited both left lateral displacement and components of normal displacement differences in water levels indicate that a fault segment lies between the observation well and a nearby irrigation well during the 4 year recording period six sharp fluctuations or spikes were noted these fluctuations occurring over 2 to 4 day periods have amplitudes of 15 30 cm they appear to be the result of creep events on a nearby fault two types of creep events are plausible 1 normal slip on an en echelon trace of the garlock fault less than 300 m south of the well with the north side up relative to fremont valley or 2 left lateral slip on the same fault because of the nature of the fluctuations we favor the latter interpretation dislocation models utilizing exponential arc tangent and skewed cosine functions were used to analyze the water level fluctuations associated pressure distribution and fault displacements the results suggest that creep on the fault ranges from several millimeters to a centimeter for individual events estimates of cumulative creep for the period 1978 1982 range from 20 to 50 mm depending on the particular model employed

interpretation of changes in water level accompanying fault creep and implications for earthquake prediction quantitative calculations for the effect of a fault creep event on observations of changes in water level in wells provide an approach to the tectonic interpretation of these phenomena for the pore pressure field associated with an idealized creep event having an exponential displacement versus time curve an analytic expression has been obtained in terms of exponential integral functions the pore pressure versus time curves for observation points near the fault are pulselike a sharp pressure increase or decrease depending on the direction of propagation is followed by more gradual decay to the normal level after the creep event the time function of the water level change may be obtained by applying the filter derived by a g johnson and others to determine the influence of atmospheric pressure on water level to the analytic pore pressure versus time curves the resulting water level curves show a fairly rapid increase or decrease and then a very gradual return to normal the results of this analytic model do not reproduce the steplike changes in water level observed by johnson and others if the procedure used to obtain the water level from the pore pressure is correct these results suggest that steplike changes in water level are not produced by smoothly propagating creep events but by creep events that propagate discontinously by changes in the bulk properties of the region around the well or by some other mechanism in addition simplistic calculations show that significant pressure field variations and water level changes near the surface may be expected to accompany a propagating creep event on a buried fault water level changes of as much as several meters may be expected at the surface for a creep event having a dislocation amplitude of l m on a semi infinite dislocation surface extending downward from a depth of 10 km and propagating horizontally at a rate of 10 km day the maximum near surface effect should be observed at a horizontal distance from the fault about equal to the depth of the top of the dislocation surface these results are consistent with the observations made in china of large water level changes preceding large earthquakes if some sort of aseismic creep event at depth precedes these earthquakes

patagonia icefield melting observed by gravity recovery and climate experiment grace 1 using recently released reprocessed gravity solutions from the gravity recovery and climate experiment grace we estimate the ice loss rate for the patagonia icefield pif of south america for the period april 2002 through december 2006 after postglacial rebound and hydrological effects are corrected the estimated rate is 27 9 11 km 3 year equivalent to an average loss of 1 6 m year ice thickness change if evenly distributed over the entire pif area the estimated contribution to global sea level rise is 0 078 0 031 mm year this is an independent confirmation of relatively large melting rate estimates from earlier studies employing topographic and cartographic data

rock avalanches on a glacier and morainic complex in haut val ferret mont blanc massif italy abstract deposits in upper val ferret mont blanc massif italy have been attributed to glacier advances and to a rock avalanche of 12 september ad 1717 we review evidence for the timing and mode of emplacement of the deposit and present a new geomorphic interpretation and relative and absolute dating to show that the ad 1717 deposit is less extensive than previously thought the landslide was deflected along one side of the valley floor preserving older slope and morainic sediments along the other side an earlier rock avalanche onto the triolet glacier occurred before ad 1000 the deposits of these landslides partly cover older moraine several kilometres downstream from the present glacier front and have affected the glacier regimen and construction of its moraines this study highlights the geomorphic impact of rock avalanches in glacierized high mountains