quantitative roundness analysis of coastal boulder deposits abstract the sedimentology of coastal boulder deposits cbd is little known these deposits and especially the largest clasts within them which commonly weigh many 10s of tonnes are of increasing interest because they attest to extreme energy wave events acting well above the high tide mark in some cases 40 m above high water and 100 m inland recent observations have made clear that storm waves rather than tsunami are important in both creating and activating these deposits but beyond that we know little about their hydrodynamics or the relative frequency of boulder movement and how this might vary with topographic setting roundness is a first order characteristic that preserves a record of deposit reworking it can tell us whether clasts move around much after they have been created from bedrock or whether they are emplaced into cbd with little or no subsequent transport but because roundness has historically been difficult to measure most roundness estimates in the literature are based on qualitative visual assessment and are therefore of limited analytical value fully reproducible roundness measurements are possible however and in the case of boulders they can be acquired quite easily using the kirkbride 2005 device in combination with a trigonometric formula presented here cbd at locations in ireland and scotland provide a test case demonstrating the utility of quantitative boulder roundness measurements the 567 clasts we measured are generally angular but a substantial proportion shows some degree of rounding most importantly there are demonstrable consistent patterns relating topography and roundness there is a strong and unsurprising inverse correlation between clast roundness and deposit elevation there is no first order relationship between roundness and inland distance but there is a power law inverse relationship between rounding and steepness ratio of elevation to distance inland the greatest degree of rounding is found in cbd located at the back of gentle coastal platforms with gradual slopes these relationships provide new insights into cbd sedimentology which we hope will be probed and tested in future studies

rock avalanche geomorphological and hydrological impact on an alpine watershed abstract rock avalanches are large flow like movements of fragmented rock that can cause extensive and rapid topographic changes for which very few quantitative data are available this paper analyses the geomorphological and hydrological impact of the 3 million m 3 thurwieser rock avalanche 2004 italian central alps by using terrestrial laser scanner airborne lidar and gnss data collected from 2005 to 2014 sediment yield with respect to the normal valley regime the dynamic and mass balance of affected glaciers and the reorganization of superficial and groundwater flow networks are quantified in the middle portion of the avalanche deposit a natural sediment trap collected sediments from a new stream channel developed along the upper portion of the deposit and from a lateral drainage basin this made possible to assess the 10 year impact of the rock avalanche on the sediment yield which increased from about 120 to about 400 t km 2 a 1 the rock avalanche partially covered a glacier with a shallow debris layer that acted as a thermal insulator limiting ice ablation and producing a 10 m high scarp between the free surface of the glacier and the debris covered portion a reduction of 75 of ice ablation was observed due to thermal insulation the rock avalanche filled a tributary valley splitting the original drainage basin in two under ordinary flows seepage occurs within the avalanche deposit along the old valley axis during high flow conditions a new stream channel is activated along the middle and lower margin of the deposit which has produced a new alluvial fan on the main valley floor the fan evolution is described up to the present volume of about 2000 m 3

long runout rockslide on glacier at tsar mountain canadian rocky mountains potential triggers seismic and glaciological implications a rhomboidal shaped rockslide with a length of 2 2 km and an area of 1 35 km2 covers 30 of a small clemenceau icefield group cirque glacier by means of remote sensing airborne photography climate and seismic data analysis the extent timing possible trigger mechanisms and rockslide effects on the glacier are discussed an ml 2 0 seismic event on 14 september 2000 represents the rockslide and has a spindle shaped waveform and high energy in the low frequencies based on a strong signal duration of 56 108 seconds the rockslide had an average runout velocity of 22 45 m s 1 stress fatigue and a combination of rain and snow followed by rapid melt and night time freezing could have co triggered the slide additional seismic events with epicentres 40 km from the cirque were recorded 26 times since 1985 and range between ml 0 9 3 3 but none were caused by or triggered large mass movement with a rock source volume of 1 6 106 m3 and a deposited volume of 2 4 106 m3 the sum of bulking and entrainment is between 25 and 150 five melt seasons post event levees 20 30 m wide tower 30 m over the surrounding glacier rockslide characteristics and its fahrboschung of 15 height length h l 0 28 indicate that this rockslide is quite typical for long runout rockslides on glaciers however the basal friction coefficient was higher than found on other glaciers and could relate to the presence of medial moraines transverse to the flowline and to pre slide debris cover the difference between the coefficient of friction in the main flowline 0 11 0 14 and that in a lobe confined between two medial moraines 0 065 suggests that confinement increases mobility by 70 115 apart from reduced ablation under the rock debris effects of the rockslide on the glacier were minimal copyright 2010 john wiley sons ltd

revised palaeoclimatic significance of mueller glacier moraines southern alps new zealand a sequence of late holocene moraines on the foreland of the mueller glacier southern alps new zealand forms part of a local moraine age database used to establish a regional glacier chronology and subsequently to investigate potential intra hemispheric and global climate forcing mechanisms we present new sedimentological and geomorphological evidence that a set of these moraine ridges previously considered to represent individual advances constitutes a single moraine complex the mueller memorial moraine formed by supraglacial transport of a large volume of landslide debris to the glacier terminus because a moraine formed in this way is not necessarily associated with an advance triggered by a climate event we question the palaeoclimatic significance of the mueller memorial moraine as well as that of other moraines in comparable settings our findings suggest that the mode of formation and glacio dynamical context of moraines whose ages contribute to existing palaeoclimate reconstructions need to be re examined in order to assess the reliability of these reconstructions copyright 2015 john wiley sons ltd

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

natural hazards extreme events and mountain topography the hazard of any natural process can be expressed as a function of its magnitude and the annual probability of its occurrence in a particular region here we expand on the hypothesis that natural hazards have size frequency relationships that in parts resemble inverse power laws we illustrate that these trends apply to extremely large events such as mega landslides huge volcanic debris avalanches and outburst flows from failures of natural dams we review quantitative evidence that supports the important contribution of extreme events to landscape development in mountains throughout the world and propose that their common underreporting in the quaternary record may lead to substantial underestimates of mean process rates we find that magnitude frequency relationships provide a link between quaternary science and natural hazard research with a degree of synergism and societal importance that neither discipline alone can deliver quaternary geomorphology stratigraphy and geochronology allow the reconstruction of times magnitudes and frequencies of extreme events whereas natural hazard research raises public awareness of the importance of reconstructing events that have not happened historically but have the potential to cause extreme destruction and loss of life in the future

intense seismicity during the 2014 2015 barðarbunga holuhraun rifting event iceland reveals the nature of dike induced earthquakes and caldera collapse mechanisms

change in surface debris cover on mont blanc massif glaciers after the little ice age termination because of insulation by supraglacial debris the dynamics of debris covered glaciers differ from those of clean glaciers thus changes in debris cover have to be taken into account when interpreting glacier fluctuations in terms of climate forcing three large glaciers in the mont blanc massif were investigated for the period since the termination of the little ice age lia using historical and scientific documents of the eighteenth and nineteenth centuries although debris cover was limited to its frontal area until the 1840s miage glacier exhibited a continuous debris cover in the first decades after the lia increasing to its present extent by the 1930s on the mer de glace a partial debris cover formed by coalescence of two of the four medial moraines at the close of the lia until 1890 these moraines have formed the present veine noire black vein in contrast brenva glacier had a continuous debris cover at the end of the eighteenth century possibly following a rock avalanche in 1767 fo

interferogram formation in the presence of complex and large deformation 1 sierra negra volcano in isabela island galapagos erupted from october 22 to october 30 in 2005 during the 8 days of eruption the center of sierra negra s caldera subsided about 5 4 meters three hours prior to the onset of the eruption an earthquake mw 5 4 occurred near the caldera because of the large and complex phase gradient due to the huge subsidence and the earthquake it is difficult to form an interferogram inside the caldera that spans the eruption the deformation is so large and spatially variable that the approximations used in existing insar software roi roi pac doris gamma cannot properly coregister sar image pairs spanning the eruption we have developed here a two step algorithm that can form intra caldera interferograms from these data the first step involves a rubber sheeting sar image coregistration in the second step we use range offset estimates to mitigate the steep phase gradient using this new algorithm we retrieve an interferogram with the best coverage to date inside the caldera of sierra negra

geomorphology lithofacies and block characteristics to determine the origin and mobility of a debris avalanche deposit at apacheta aguilucho volcanic complex aavc northern chile abstract understanding the evolution of a volcanic edifice is important in establishing its associated geological hazards apacheta and aguilucho volcanoes northern chile formed a volcanic complex with known fumaroles and geothermal potential among the products resulting from the evolution of the apacheta aguilucho volcanic complex aavc a new volcanoclastic deposit has been recognized towards the eastern flank of the volcanic complex this deposit is constituted by fragments of andesitic to dacitic lava and hydrothermally altered lava blocks these fragments which reach up to 5 m in diameter form geomorphological structures such as hummocks levees and ridges using these geomorphological characteristics the distribution of the main lithological facies or lithofacies and fragment features jigsaw cracks and impact marks we proposed that this deposit was generated by a debris avalanche this debris avalanche was triggered by partial collapse of an ancestral volcanic edifice occurred between 100 and 700 ka the collapse of the aavc ancestral edifice was influenced by hydrothermal alteration and the extensional tectonic setting that characterize the cerro pabellon dome area the mobility of the avalanche and the genesis of the main geomorphological features associated with the deposit are related to fragmentation of material during avalanche genesis and movement

characterization of alpine rockslides using statistical analysis of seismic signals 1 seismic data analysis is a powerful tool for remote characterization of rock slope failures here we develop quantitative estimates of fundamental rockslide properties e g volume based solely on data from an existing regional seismic network we assembled a data set of twenty known rockslides in the central alps with volumes between 1 000 and 2 000 000 m3 and analyzed their corresponding seismograms common signal characteristics include emergent onsets slowly decaying tails and a triangular spectrogram shape the main component of seismic energy is contained in frequencies below 3 4 hz while higher frequency signals may be caused by block impacts location estimates were generated using automatic arrival time picks and resulted in a mean location error of 10 9 km a linear relationship for the detection limit of a rockslide as a function of volume was identified for our seismic station network to estimate rockslide volume runout distance drop height potential energy and fahrboschung angle of reach we extracted five simple metrics from each seismogram signal duration peak value of the ground velocity envelope velocity envelope area risetime and average ground velocity using multivariate linear regression the combination of duration peak envelope velocity and envelope area best estimated event parameters with r2 values ranging between 0 8 and 0 88 three new rockslides were then used to validate our method and volume runout drop height and potential energy were estimated within the correct order of magnitude when provided with a suitable data set of rockslide events our method can be easily adapted to other regions and seismic networks

the pattern of circumferential and radial eruptive fissures on the volcanoes of fernandina and isabela islands galapagos maps of the eruptive vents on the active shield volcanoes of fernandina and isabela islands galapagos made from aerial photographs display a distinctive pattern that consists of circumferential eruptive fissures around the summit calderas and radial fissures lower on the flanks on some volcano flanks either circumferential or radial eruptions have been dominant in recent time the location of circumferential vents outside the calderas is independent of caldera related normal faults the eruptive fissures are the surface expression of dike emplacement and the dike orientations are interpreted to be controlled by the state of stress in the volcano very few subaerial volcanoes display a pattern of fissures similar to that of the galapagos volcanoes some seamounts and shield volcanoes on mars morphologically resemble the galapagos volcanoes but more specific evidence is needed to determine if they also share common structure and eruptive style

discovery and dating of pre lgm deposits in a high catchment of the dolomites italy new insights on climate related geomorphological processes during the late pleistocene abstract the results from the analysis of a relatively deep stratigraphic sequence from a formerly glaciated plateau in the upper badia valley dolomites italy are discussed and the first insight on late pleistocene sedimentary records and geomorphological evolution of the area are provided the investigated sequence comprises i cohesive sediments interpreted as colluvial eluvial in origin or as stagnant water deposits ii sandy diamicton and dolostone monolithic sediments interpreted as gravity induced deposits possibly owing to debris flows or wash out reworking of rock avalanche deposits from the surrounding dolomite ridges iii silty diamicton interpreted as lodgement till possibly attributed to the last glacial maximum lgm radiocarbon dating results and interpretation of stratigraphic data supported by geomorphological field surveys remote sensing data analyses and palaeo climatic and palaeo environmental data from literature enabled us to conclude that the investigated plateau pralongia ca 2000 m a s l was likely ice free for most of marine isotope stage 3 in particular between 38 ka bp and the inset of full glacial conditions lgm 27 ka bp clastic gravity induced sediments were deposited within the study site supraglacial transport is supposed to have played a role in the emplacement of gravity induced deposits from the surrounding dolomite cliffs to the plateau this study resulted in the first pre lgm record of sedimentation and palaeo environmental conditions inside the eastern dolomites in the 46 to 38 ka bp period

the hattian bala rock avalanche and associated landslides triggered by the kashmir earthquake of 8 october 2005 the kashmir earthquake of the 8 october killed an estimated 87 350 people 25 500 through co seismic landslides the largest landslide associated with the earthquake was the 68 106 m3 hattian bala rock avalanche that destroyed a village and killed around 1000 people the deposit blocks the valley to a depth of 130 m impounding a lake that reached the dam crest in april 2007 an outburst flood now threatens a major settlement 3 km downstream a series of space images reveals landslide clusters in the rock avalanche source area prior to the earthquake the images also reveal a large slow moving landslide with its toe in the lake failure of this landslide may induce dam failure through overtopping and scour eighty five landslides in the hattian bala catchment predate the shaking of 8 october 2005 a further 73 are co seismic with the main shock and 21 postdate it in the period up to october 2006 landslide magnitude frequency distribution plots derived from satellite images allow an assessment of the contribution of seismically triggered events as compared to background rates of activity

evidence of nonlinear elasticity of the crust from the mw7 6 manyi tibet earthquake satellite synthetic aperture radar sar interferometry shows that the magnitude 7 6 manyi earthquake of 8 november 1997 produced a 170 kilometer long surface break with up to 7 meters of left lateral slip reactivating a n76 e quaternary fault in western tibet the radar interferometric map reveals asymmetric along strike displacement profiles between the two sides of the surface rupture a pattern that cannot be explained with linear elastic theory this observation suggests that the elastic moduli of the crust in tension and in compression are different because of the presence of cracks in the crust at shallow depth a model indicates that a ratio of 2 between compressive and tensile elastic moduli can account for the observed asymmetry a ratio that is consistent with laboratory and borehole measurements

interpretation age and significance of a relict paraglacial and periglacial boulder dominated landform assemblage in alnesdalen romsdalsalpane southern norway abstract a boulder dominated landform assemblage in an alpine setting in norway is described interpreted and dated using a combination of schmidt hammer exposure age dating shd and cosmogenic 10be surface exposure dating the origin and formation of these features is determined from their morphology topographic setting and age three main components of the assemblage are recognized first a 300 m long and 160 m wide tongue shaped rock slope failure with a shd age of 11 49 0 82 12 96 0 86 ka is identified on the basis of its planform thickness runout distance and association with a fractured backing scarp this is interpreted as a relict paraglacial landform triggered by deglaciation second a 400 m long unequivocal pronival protalus rampart with an shd age of 6 95 0 97 8 35 1 21 ka is identified on the basis of its narrow ridge form aligned close to the foot of an extensive talus slope although formation of the rampart probably commenced with deglaciation the younger shd ages indicate formation at a diminishing rate through the holocene third a 550 m by 150 m lobate component with transverse ridges longitudinal and transverse depressions and enclosed pits previously identified as a rock glacier is dated to 11 33 0 83 13 33 0 90 ka with the schmidt hammer and between 13 3 2 0 14 7 2 0 ka with 10be this third component may also be a product of rock slope failure but attribution to rock glacier creep associated with either interstitial ice permafrost or buried glacier ice during the allerod interstadial younger dryas stadial and to which one or more rock slope failures contributed debris cannot be rejected the advantages and limitations of compiling such evidence for identifying differentiating and classifying apparently similar boulder dominated colluvial landforms are exemplified

measuring ground displacements from sar amplitude images application to the landers earthquake ers sar amplitude images are utilized to map ground displacements from a sub pixel correlation method it yields a ground two dimensional displacement field with independent measurements about every 128m in azimuth and 250m in range the accuracy depends on the characteristics of the images for the landers test case the 1 uncertainty is 0 8m in range and 0 4m in azimuth we show that this measurement provides a map of major surface fault ruptures accurate to better than 1km and information on coseismic deformation comparable to the 92 gps measurements available although less accurate this technique is more robust than sar interferometry and provides complementary information since interferograms are only sensitive to the displacement in range

diagnostic characteristics and paleodynamics of supraglacial rock avalanches innerdalen western norway abstract misinterpretation of rock avalanche deposits in mountain environments is not uncommon because of the complex interactions between rock avalanches and glaciers this paper for the first time presents a detailed description of suspicious rock boulder deposits which are remnants of a rock avalanche onto a late pleistocene glacier the boulder deposits cover around 1 1 km 2 and are distributed over an area of around 7 5 km 2 and a variety of landforms three closely nested distinct terminal moraines 0 45 km 2 and dislocated terminal moraines 0 34 km 2 entirely built up of large boulders lateral moraines that decrease in elevation over a short distance and connect to the terminal moraines small patches 0 02 km 2 of boulders that occur in islands on a peat dominated valley floor and large patches of boulder fields 0 25 km 2 in size hanging 350 m above the valley floor the latter are disconnected from any potential source area 10 be cosmogenic nuclide ages of the three terminal moraines give an indistinguishable late pleistocene age of 13 6 1 4 ka whereas the largest boulder field that is located on the opposite side of the valley from the failed mountain yields a 10 be age of 14 1 0 4 ka which is slightly older but indistinguishable from the moraine deposits within uncertainty margins all boulder deposits add up to a volume of 31 10 6 m 3 the interpretation of a single rock avalanche source for those landforms is further confirmed by numerical runout modeling using dan3d a failure of the entire volume from skarfjellet mountain would result in a runout pattern that is identical to that of the distributed boulder fields when considering that the valley was filled with a glacier around 350 m thick the rock avalanche would not reach the position of the terminal moraines however a glacial re advance could have transported the boulders to that position the late pleistocene rock avalanche was followed by a holocene rock avalanche with a volume of 23 10 6 m 3 and a typical lobate deposit damming the innerdalen valley and creating a lake 10 be ages indicate that this event occurred 7 97 0 94 ka ago structural measurements performed on high resolution lidar scans show a strongly jointed source rock with three joint sets with dip dip direction 81 034 86 331 and 77 354 and a foliation with 22 003 the kinematic of the failures can thus be a combination of small scale wedge failures and planar sliding on shallow dipping foliation our detailed description can enable a better identification and interpretation of similar deposits in other mountain areas

do debris covered glaciers demonstrate distinctive hydrological behaviour compared to clean glaciers abstract supraglacial debris is known to strongly influence the distribution of glacier surface melt since melt inputs drive the formation and evolution of glacial drainage systems it should follow that the drainage systems of debris covered glaciers will differ from those of debris free glaciers this would have implications for the proglacial runoff regime subglacial erosion and glacier dynamics this paper presents analysis of return curves from 33 successful dye injections into the extensively debris covered miage glacier italian alps it demonstrates that the spatial distribution of supraglacial debris influences the structure and seasonal evolution of the glacial drainage system where the debris cover is continuous melt is lower and the surface topography is chaotic with many small supraglacial catchments these factors result in an inefficient englacial subglacial drainage network beneath continuous debris which drains to the conduit system emanating from the upper ablation zone melt rates are high in areas of clean and dirty ice above the continuous debris runoff from these areas is concentrated by inter moraine troughs into large supraglacial streams which encourages the early season development of an efficient englacial subglacial conduit system downstream of this area drainage efficiency from the debris covered area increases over the melt season but dye trace transit velocity remains lower than from moulins on the upper glacier future runoff models should account for the influence of supraglacial debris on the hydrological system

the ad 1717 rock avalanche deposits in the upper ferret valley italy a dating approach with cosmogenic 10be on 12 september ad 1717 a rock volume larger than 10 million m3 collapsed onto the triolet glacier mobilized a mass composed of ice and sediment and travelled more than 7 km downvalley in the upper ferret valley mont blanc massif italy this rock avalanche destroyed two small settlements causing seven casualties and loss of livestock no detailed maps were made at the time later investigators attributed accumulations of granitic boulders and irregular ridges on the upper valley floor to either glacial deposition or the ad 1717 rock avalanche or a complex mixture of glacial deposition earlier rock avalanche and ad 1717 rock avalanche origin in this study we present cosmogenic 10be exposure ages from nine boulders in the extensive chaotic boulder deposit with irregular ridges two from holocene glacier free areas and one from a little ice age moraine exposure ages between 330 23 and 483 123 a from eight of nine boulders from the chaotic deposit indicate that at least seven were deposited by the ad 1717 rock avalanche the other three boulders yielded 10be exposure ages of 10 900 400 9700 400 and 244 97 a respectively our results are in good agreement with the existing chronology from dendrochronology and lichenometry and radiocarbon analysis of wood samples but not with older 14c ages from a peat bog in the upper part of the valley based on the new age control the rock avalanche deposits cover the whole bottom of the upper ferret valley copyright 2012 john wiley sons ltd

very high elevation mont blanc glaciated areas not affected by the 20th century climate change 1 this paper analyses the impact of climate change over the last 100 years on high elevation glaciated areas of the mont blanc range comprising ice fields covering the top of the mont blanc 4808 m and dome du gouter 4300 m areas surface ablation is negligible for these high elevation areas and the surface mass balance is mainly controlled by snow accumulation at dome du gouter ice fluxes have been calculated through two transversal sections by two independent methods in order to assess long term surface accumulation a comparison between these results and recent accumulation observations together with the strong relationship between valley precipitation and snow accumulation suggests that surface accumulation rates did not change significantly over the entire 20th century moreover the small ice thickness changes less than 3 m on the average observed at mont blanc and dome du gouter between 1905 and 2005 clearly reveal that these high elevation glaciated areas have not been significantly affected by climate change over the last 100 years

using stereo satellite imagery to account for ablation entrainment and compaction in volume calculations for rock avalanches on glaciers application to the 2016 lamplugh rock avalanche in glacier bay national park alaska

the may 2005 eruption of fernandina volcano galapagos the first circumferential dike intrusion observed by gps and insar the may 2005 eruption of fernandina volcano galapagos occurred along circumferential fissures parallel to the caldera rim and fed lava flows down the steep southwestern slope of the volcano for several weeks this was the first circumferential dike intrusion ever observed by both insar and gps measurements and thus provides an opportunity to determine the subsurface geometry of these enigmatic structures that are common on galapagos volcanoes but are rare elsewhere pre and post eruption ground deformation between 2002 and 2006 can be modeled by the inflation of two separate magma reservoirs beneath the caldera a shallow sill at 1 km depth and a deeper point source at 5 km depth and we infer that this system also existed at the time of the 2005 eruption the co eruption deformation is dominated by uplift near the 2005 eruptive fissures superimposed on a broad subsidence centered on the caldera modeling of the co eruption deformation was performed by including various combinations of planar dislocations to simulate the 2005 circumferential dike intrusion we found that a single planar dike could not match both the insar and gps data our best fit model includes three planar dikes connected along hinge lines to simulate a curved concave shell that is steeply dipping 45 60 toward the caldera at the surface and more gently dipping 12 14 at depth where it connects to the horizontal sub caldera sill the shallow sill is underlain by the deep point source the geometry of this modeled magmatic system is consistent with the petrology of fernandina lavas which suggest that circumferential eruptions tap the shallowest parts of the system whereas radial eruptions are fed from deeper levels the recent history of eruptions at fernandina is also consistent with the idea that circumferential and radial intrusions are sometimes in a stress feedback relationship and alternate in time with one another

snow control on active layer thickness in steep alpine rock walls aiguille du midi 3842 m a s l mont blanc massif since the early 2000s a remarkable amount of rockfalls has been observed in permafrost areas of the mid latitude mountain ranges concurrently to hot summers this study explores the seasonal thaw st in permafrost rock walls of the aiguille du midi site 3842 m a s l mont blanc massif we first analyse six years of temperature records in three 10 m deep boreholes against air temperature at and a four year time series of pictures showing the snow conditions on two rock faces then we test the sensitivity of the active layer against eight snow fall scenarios using the 1 d surface energy balance and heat conduction model cryogrid 3 forced by in situ measurements from a vertical face snow falls occur all the year round at this elevation and play an important role for the active layer thickness alt but the snow cover and its control are highly heterogeneous a long lasting of a snow cover during spring early summer delays the st and reduces the alt the thicker and the more spatially continuous is the snow cover the stronger are the delay and alt reduction convective clouds could also reinforce this pattern the summer at and heat waves are the dominant controlling factors of the alt but summer snow falls can sometimes persist for several days on the rock surface and reduce the effect of the heat waves active layer can thicken during the early fall except if the snow starts to accumulate on the rock surface and favours the refreezing the timing of the snow fall is the most critical parameter to determine the snow effect on the alt this study suggests that the characteristics of the bedrock and snow accumulation steepness surface roughness and sun exposure must be taken into account to better understand the formation and changes of the active layer and its possible implications for rockfall triggering

the influence of glacier surface processes on the short term evolution of supraglacial tree vegetation the case study of the miage glacier italian alps supraglacial debris cover allows vegetation to colonize glacier surface and whenever it is enough stable and thick also shrubs and trees can germinate and grow supraglacial tree growth and distr

caldera morphology in the western galapagos and implications for volcano eruptive behavior and mechanisms of caldera formation abstract caldera morphology on the six historically active shield volcanoes that comprise isabela and fernandina islands the two westernmost islands in the galapagos archipelago is linked to the dynamics of magma supply to and withdrawal from the magma chamber beneath each volcano caldera size e g volumes 2 9 times that of the caldera of kilauea hawai i the absence of well developed rift zones and the inability to sustain prolonged low volumetric flow rate flank eruptions suggest that magma storage occurs predominantly within centrally located chambers at the expense of storage within the flanks the calderas play an important role in the formation of distinctive arcuate fissures in the central part of the volcano repeated inward collapse of the caldera walls along with floor subsidence provide mechanisms for sustaining radially oriented least compressive stresses that favor the formation of arcuate fissures within 1 2 km outboard of the caldera rim variations in caldera shape depth to diameter ratio intra caldera bench location and the extent of talus slope development provide insight into the most recent events of caldera modification which may be modulated by the episodic supply of magma to each volcano a lack of correlation between the volume of the single historical collapse event and its associated volume of erupted lava precludes a model of caldera formation linked directly to magma withdrawal rather caldera collapse is probably the result of accumulated loss from the central storage system without sufficient recharge and as has been suggested for kilauea may be aided by the downward drag of dense cumulates and intrusives

dda validation of the mobility of earthquake induced landslides abstract this paper studies the run out of earthquake induced landslides there are more than 20 mechanical models to explain long run out of rapid landslides including some earthquake induced landslides however notably few of them considered the effect of seismic loading on the run out of landslides in a previous study we have proposed a model which is called the multiplex acceleration model mam to interpret the long run out mechanism and a shaking table test has been performed to verify the mam because the previous mam is a conceptual model and only a single stone has been examined under sine waves by the shaking table test the mam needs to be extended and further verified in this paper the mam was extended by introducing the movement change that was induced by the so called trampoline effect of earthquake loading and the latest practical numerical simulation program discontinuous deformation analysis dda was used to verify the mobility of earthquake induced landslides after a conceptual landslide model was used to verify the effect of seismic loading on the mobility the donghekou landslide which was a typical long run out landslide that was induced by the 2008 wenchuan earthquake was analyzed the results show that the seismic loading could be one of the factors that could eventually help increase the run out of landslides

slopes of western galapagos volcanoes from airborne interferometric radar the distribution of slopes on the six basaltic shield volcanoes in the western galapagos islands is investigated using a digital elevation model derived from airborne interferometric radar topsar data these measurements have a spatial sampling of 10 m pixel a vertical accuracy of 3 to 5 m and constitute the highest resolution most complete topographic data set available for the islands volcano heights are determined to range from 1 124 m sierra negra to 1 710 m wolf over extensive areas of each volcano slopes exceed 25 with the highest slopes being 37 on wolf and 36 on fernandina we confirm that two morphologic subgroups exist cerro azul fernandina and wolf with deep calderas depth between 40 60 of the subaerial height of the volcano and steep 20 maximum slopes at elevations between 60 and 80 of the volcano height and alcedo darwin and sierra negra with shallow calderas depth 25 of subaerial height and slopes that remain 15 until 90 of the total height is reached our data show that steep slopes are not uniquely correlated with the occurrence of arcuate fissures at the summit leaving the origin of the steep slopes unresolved

beyond debuttressing mechanics of paraglacial rock slope damage during repeat glacial cycles cycles of glaciation impose mechanical stresses on underlying bedrock as glaciers advance erode and retreat fracture initiation and propagation constitute rock mass damage and act as preparatory factors for slope failures however the mechanics of paraglacial rock slope damage remain poorly characterized using conceptual numerical models closely based on the aletsch glacier region of switzerland we explore how in situ stress changes associated with fluctuating ice thickness can drive progressive rock mass failure preparing future slope instabilities our simulations reveal that glacial cycles as purely mechanical loading and unloading phenomena produce relatively limited new damage however ice fluctuations can increase the criticality of fractures in adjacent slopes which may in turn increase the efficacy of fatigue processes bedrock erosion during glaciation promotes significant new damage during first deglaciation an already weakened rock slope is more susceptible to damage from glacier loading and unloading and may fail completely we find that damage kinematics are controlled by discontinuity geometry and the relative position of the glacier ice advance and retreat both generate damage we correlate model results with mapped landslides around the great aletsch glacier our result that most damage occurs during first deglaciation agrees with the relative age of the majority of identified landslides the kinematics and dimensions of a slope failure produced in our models are also in good agreement with characteristics of instabilities observed in the field our results extend simplified assumptions of glacial debuttressing demonstrating in detail how cycles of ice loading erosion and unloading drive paraglacial rock slope damage

permafrost in steep bedrock slopes and its temperature related destabilization following climate change permafrost in steep bedrock is abundant in many cold mountain areas and its degradation can cause slope instability that is unexpected and unprecedented in location magnitude frequency and timing these phenomena bear consequences for the understanding of landscape evolution natural hazards and the safe and sustainable operation of high mountain infrastructure permafrost in steep bedrock is an emerging field of research knowledge of rock temperatures ice content mechanisms of degradation and the processes that link warming and destabilization is often fragmental in this article we provide a review and discussion of existing literature and pinpoint important questions ice filled joints are common in bedrock permafrost and possibly actively widened by ice segregation broad evidence of destabilization by warming permafrost exists despite problems of attributing individual events to this phenomenon with certainty convex topography such as ridges spurs and peaks is often subject to faster and deeper thaw than other areas permafrost degradation in steep bedrock can be strongly affected by percolating water in fractures this degradation by advection is difficult to predict and can lead to quick and deepdevelopment of thaw corridors along fractures in permafrost and potentially destabilize much greater volumes of rock than conduction would although most research on steep bedrock permafrost originates from the alps it will likely gain importance in other geographic regions with mountain permafrost

multiple origins of large hummock deposits in alai valley northern pamir implications for palaeoclimate reconstructions abstract this paper interprets the origin of several of the largest hummocky landform assemblages in the alai valley northern pamir a formerly glaciated intermontane depression the vast hummocky deposits in the koman suu and achik tash river catchments are found to be of two contrasting modes of formation glacial hummocks deposited during koman and lenin glaciers withdraw and avalanche hummocks produced during catastrophic koman and lenin rock avalanches the origins of the deposits we assessed through remote and field based geomorphological mapping as well as sedimentological investigations which included clast analysis and the identification of micro scale agglomerates indicative of rock avalanche emplacement both the koman and lenin rock avalanches were large catastrophic events with run outs of 34 and 24 km respectively and a volume over 1 109 m3 each that occurred subsequent to glacier withdrawal from the area the complex conditions on the moment of the rock avalanche emplacement promoted unusual deposits geomorphology and extensive run outs the landslide landforms formed over the pre existing glacial hummocks and fluvial deposits and are geomorphologically and sedimentologically distinct from the larger glacial hummocks the reconstruction of this sequence of events has implications for how hummock dating should be interpreted this research illustrates large scale catastrophic landsliding in the glacial environment and adds to the ongoing debate about the misidentification of rock avalanche deposits as of glacial origin and their relevance to palaeoclimatological and palaeoseismological reconstructions

evidence for a rock avalanche origin for the hillocks moraine otago new zealand abstract a landform in otago new zealand previously interpreted as a glacial deposit has been investigated described and reinterpreted as a rock avalanche deposit the hillocks is a conspicuous cluster of small conical hills on the dart river floodplain the landform is protected under a local bylaw because of its identification as an outstanding example of a glacial kame deposit however the geological and geomorphological setting and the deposit morphology sedimentology and lithology suggest that it was formed by a large c 22 5 10 6 m 3 rock avalanche subsequent to glacial retreat and that the deposit temporarily dammed the dart river valley relative age dating evidence suggests that it is at least several hundred years old but younger than ca 7500 b p this work highlights the problem of paleoclimatic reconstructions using moraines as indicators of regional climate events despite similarities in form and in some cases sedimentology by applying an understanding of landslide initiation runout and depositional process we demonstrate that it is possible to distinguish the deposits produced by landslides from those produced by glacial deposition

minor inheritance inhibits the calibration of the 10be production rate from the ad 1717 val ferret rock avalanche european alps to calibrate the in situ 10be production rate we collected surface samples from nine large granitic boulders within the deposits of a rock avalanche that occurred in ad 1717 in the upper ferret valley mont blanc massif italy the 10be concentrations were extremely low and successfully measured within 10 analytical uncertainty or less the concentrations vary from 4829 448 to 5917 476 at g 1 using the historical age exposure time we calculated the local and sea level high latitude i e 60 cosmogenic 10be spallogenic production rates depending on the scaling schemes these vary between 4 60 0 38 and 5 26 0 43 at g 1 a 1 although they correlate well with global values our production rates are clearly higher than those from more recent calibration sites we conclude that our 10be production rate is a mean and an upper bound for production rates in the massif region over the past 300 years this rate is probably influenced by inheritance and will yield inaccurate e g too young exposure ages when applied to surface exposure studies in the area other independently dated rock avalanche deposits in the region that are approximately 103 years old could be considered as possible calibration sites

the landslide response of alpine basins to post little ice age glacial thinning and retreat in southwestern british columbia abstract the role of post little ice age lia neoglacial retreat on landslide activity is investigated in 19 alpine basins along the upper lillooet river valley british columbia we examine how neoglacial scouring and glacial recession have modified hillslope form and slope stability and construct a decision making flowchart to identify landslide hazards associated with glacial retreat this work is based on field mapping gis analysis statistical associations between landslides and terrain attributes and a comparison between neoglaciated and non neoglaciated terrain within each basin the bedrock landslide response to glacial retreat varies appreciably according to lithology and the extent of glacial scour below the lia trimline valleys carved in weak quaternary volcanics show significant erosional oversteepening and contain deep seated slope movement features active rock fall rock slides and rock avalanches near glacial trimlines basins in stronger granitic rock rarely show increased bedrock instability resulting from post lia retreat except for shallow seated rock slides along some trimlines and failures on previously unstable slopes in surficial materials landslides associated with post lia retreat originate in till or colluvium as debris slides or debris avalanches and are concentrated along lateral moraines or glacial trimlines significant spatial association was also observed between recent catastrophic failures gravitational slope deformation and slopes that were oversteepened then debuttressed by glacial erosion eight out of nine catastrophic rock slope failures occurred just above glacial trimlines and all occurred in areas with a previous history of deep seated gravitational slope movement implying that this type of deformation is a precursor to catastrophic detachment

physical volcanology and structural development of sierra negra volcano isabela island galapagos archipelago sierra negra is the most voluminous of the western galapagos shields and exhibits many unusual morphologic features extensive lower flank apron steep upper flanks a broad summit plateau a large complex caldera ubiquitous occurrence of aa and radial and circumferential fissures a field based investigation of the volcano was conducted in order to establish the distribution and characteristics of eruptive zones and associated flow fields and to construct a volcano wide surface flow stratigraphy geochronologic data were used to determine the age of the units and combined with flow volume calculations to estimate both the historic and total volcano eruption rates ninety one kilometers of radial and circumferential fissures were mapped and grouped into four eruptive zones which form a volcano wide east northeast trending rift system that deflects around the caldera the eruptive zones are restricted spatially and temporally and document long term changes in the volcano s development long fluid lava flows are broadly distributed among five ages resulting in a subdued flank profile by the development of an extensive lower flank apron around the volcano ten historical eruptions have occurred with eruption rates of 44 to 248 m3 s and an average growth rate of 12 106 m3 yr age determinations of lava flows by 14c and cosmogenic 3he range from 400 to 6900 yr the total volcano growth rate is estimated to be 1 106 m3 yr these results confirm the young age of sierra negra lavas and the validity of the relative ages determined from stratigraphic study in total the volcano has undergone over 90 resurfacing in the past 4500 yr the summit of sierra negra is entirely occupied by a shallow elliptical 7 10 km caldera near vertical ring faults circumscribe the summit and expose 100 to 140 m of lava flows subparallel sets of caldera growth faults cut the western and southern caldera walls and are not associated with eruptive activity the inclination of remnant magnetism and the attitudes of the flows exposed in the caldera walls indicate that the lavas have not been appreciably deformed nor have they been intruded by dikes or sills the caldera interior is structurally complex and contains a 14 km long c shaped sinuous ridge composed of a complex set of normally faulted blocks with inward dipping 20 60 flow tops the sinuous ridge is interpreted to have formed gradually as the caldera floor pivoted in a trap door fashion jammed its western edge and then fractured in several places concomitant with the long term vertical and lateral growth of the volcano a regional tectonic stress field superimposed upon the galapagos platform appears to have exerted primary control on the location of sierra negra including the early development of the east northeast rift system intervolcano stresses have controlled the distribution of eruptive zones only where significant subaerial overlap of adjacent volcanoes occurs large volume high discharge rate eruptions from fissures along the east northeast rift system are responsible for the development of an extensive coastal apron flow stacking at mid flank elevations and generally subdued slopes in comparison to other western galapagos volcanoes the summit caldera and underlying magma chamber are subordinate in influencing the distribution of lower flank stress but dominate the development of the summit stress field and orientation of eruptive fissures the absence of summit deformation together with the ubiquitous occurrence of short stubby summit flows indicates that the steep upper flanks are constructional in origin

entrainment of debris in rock avalanches an analysis of a long run out mechanism many rock avalanches entrain and liquefy saturated soil from their paths evidence for this includes mud displaced from the margins of rock avalanche deposits substrate material smeared along the base of deposits extrusion of liquefied soil upward through the deposits and increases of volume a hypothesis first suggested in 1881 and since reinforced by several authors suggests that entrainment of substrate material increases mobility although the process has been discussed in the literature for more than 100 years few detailed and quantitative descriptions exist the main purpose of this paper is to describe two recent cases from british columbia canada where rockslides entrained substrate on a very large scale influencing the character of the events estimated volume balance curves based on detailed field mapping are provided for both cases dynamic analyses are carried out using a numerical model and using the same set of rheological parameters the mechanism of material entrainment and displacement is discussed the data suggest that rapid rock failures entraining very large quantities of saturated substrate material represent a special type of landslide transitional between rock avalanche and debris avalanche many rock avalanches can thus be seen as end members of a continuum of phenomena involving rock failure followed by interaction with saturated substrate

correlation of late quaternary moraines impact of climate variability glacier response and chronological resolution abstract the last decade has seen a global surge in the number and resolution of well dated geomorphological reconstructions of mountain glacier fluctuations and former ice sheet extents this has been facilitated by the widespread deployment of large samples of terrestrial cosmogenic nuclide dating tcnd allowing more sophisticated probability analyses for reducing the statistical uncertainty of moraine ages and testing of correlations at local regional and hemispheric scales geochronological advances in the field laboratory and on model calibration have taken place in parallel with modelling of palaeoclimate based on glacier reconstructions and of glacier sensitivity to temperature and precipitation forcing in spite of these advances basic conceptual issues remain this review questions whether the technical leap forward in dating has encouraged us to over reach our interpretive limits particularly in terms of the concept and practice of correlation we propose that to enable reliable correlation glacier chronologies should first be examined for their climatic integrity spatial coherence and chronological robustness even with excellent dating interpretive complexity remains due to complex climate signals and glacier response characteristics and to erosion censoring of the landform record all are issues which must be addressed to avoid either spurious lumping correlation or splitting differentiation of glacier chronologies and thus misinterpretation of the climatic significance of reconstructed glacier advances we suggest that the reliability of correlation is no better than the weakest link in the chain of reasoning which connects climatic fluctuations with dated landforms and sediments improved dating means that poor chronological resolution is less likely to be the limiting factor for correlation but shifts the focus onto other less quantifiable sources of uncertainty these conceptual statements are exemplified with reference to holocene glacial chronologies of contrasting mid latitude environments in southern norway iceland and new zealand

debris thickness patterns on debris covered glaciers abstract many debris covered glaciers have broadly similar debris thickness patterns surface debris thickens and tends to transition from convex to concave up down glacier we explain this pattern using theory analytical and numerical models paired with empirical observations down glacier debris thickening results from the conveyor belt like nature of the glacier surface in the ablation zone debris can typically only be added but not removed and from the inevitable decline in ice surface velocity toward the terminus down glacier thickening of debris leads to the reduction of sub debris melt and debris emergence toward the terminus convex up debris thickness patterns occur near the up glacier end of debris covers where debris emergence dominates ablation controlled concave up debris thickness patterns occur toward glacier termini where declining surface velocities dominate velocity controlled a convex concave debris thickness profile inevitably results from the transition between ablation control and velocity control down glacier debris thickness patterns deviating from this longitudinal shape are most likely caused by changes in hillslope debris supply through time by establishing this expected debris thickness pattern the effects of climate change on debris cover can be better identified

a physically based method for estimating supraglacial debris thickness from thermal band remote sensing data in order to account for the effects of debris cover in model scenarios of the response of glaciers to climate change and water resource planning it is important to know the distribution and thickness of supraglacial debris and to monitor its change over time previous attempts to map surface debris thickness using thermal band remote sensing have relied upon time specific empirical relationships between surface temperature and thickness limiting their general applicability in this paper we develop a physically based model that utilizes advanced spaceborne thermal emission and reflection radiometer aster thermal band remotely sensed imagery and is based on a solution of the energy balance at the debris surface the model is used to estimate debris thickness on miage glacier italy and is validated using field debris thickness measurements and a previously published debris thickness map the temporal transferability of the model is demonstrated through successful application to a separate aster image from a different year using reanalysis meteorological input data this model has the potential to be used for regional scale supraglacial debris thickness mapping and monitoring for debris up to at least 0 50 m thickness but improved understanding of the spatial patterns of air temperature aerodynamic roughness length and thermal properties across debriscovered glaciers is needed

volcano deformation and eruption forecasting recent advances in global positioning system gps tilt and interferometric synthetic aperture radar insar have greatly increased the availability of volcano deformation data these measurements combined with appropriate source models can be used to estimate magma chamber depth and to provide information on chamber shape and volume change however kinematic models cannot constrain magma chamber volume and provide no predictive

fault slip distribution of the 1999 mw 7 1 hector mine california earthquake estimated from satellite radar and gps measurements we use a combination of satellite radar and gps data to estimate the slip distribution of the 1999 m w 7 1 hector mine earthquake a right lateral strikeslip earthquake that occurred on a northwest southeast striking fault in the southern california mojave desert the data include synthetic aperture radar interferograms insar from both ascending and descending orbits radar amplitude image offset fields sario for both ascending and descending azimuth directions and campaign gps observations from 55 stations provided by agnew et al 2002 we model the fault with nine segments derived from the field mapped fault rupture the sario data and aftershock locations we first estimate the dip of each fault segment as well as a single constant strike slip component across each segment resulting in an average dip of 83 to the northeast and slip of up to 5 6 m then we fix the optimal fault segment dip discretize the fault segments into 1 5 km 1 5 km patches and solve for the variable slip distribution using a nonnegative least squares method that includes an appropriate degree of smoothing our preferred solution has both right lateral strike slip and reverse faulting the estimated geodetic moment is 5 93 10 19 n m m w 7 1 similar to seismological estimates indicating that there are insignificant interseismic and postseismic deformation signals in the data we find strike slip displacements of up to 6 0 m and reverse faulting of up to 1 6 m with the maximum slip located just northwest of the epicenter most of the slip is concentrated northwest and south of the epicenter little slip is found on the northeastern branch of the fault the sario data and our modeling indicate that the amount and extent of surface fault rupture were underestimated in the field

quaternary moraines vs catastrophic rock avalanches in the karakoram himalaya northern pakistan a history and conception of glacial events for the central karakoram himalaya proposed some 80 years ago by giotto dainelli are largely accepted today however certain deposits identified as terminal moraine complexes marking glacial episodes were actually emplaced by rock avalanches in the skardu and shigar intermontane basins of baltistan at least 15 rock avalanche events were previously mapped as moraine or till criteria used for distinguishing these catastrophic landslide deposits emphasize homogeneous lithology of rubble and matrix clast shape facies characteristics the large scale unity of emplacement and morphological relations to valley topography the deposits of three events at katzarah satpura and the north end of shigar valley have been reconstructed in detail thick supraglacial debris does not result in similar deposits extensive valley fills river terraces large sediment fans and lacustrine sediments formerly attributed to late glacial conditions are reinterpreted as postglacial events involving rock avalanches that interrupted fluvial development existing reconstructions of glaciations are left in doubt especially late glacial events in the central karakoram as are the roles assigned to karakoram main indus valley and western himalayan ice

mechanical modeling of circumferential and radial dike intrusion on galapagos volcanoes a distinctive and unusual pattern of eruptive fissures is observed on the active volcanoes of the galapagos islands reflecting circumferential dike intrusion near the calderas and radial dike intrusion on the volcano flanks elastic finite element models were used to investigate how a stress field could be produced and maintained to promote both circumferential and radial dike emplacement modeling results show that magma reservoirs of galapagos volcanoes are probably diapiric because this shape promotes both circumferential and radial intrusions but magma pressure alone cannot create the observed pattern of dikes loading by volcano growth and magma reservoir pressure could produce a stress field of suitable orientation but insufficient magnitude the intrusion of circumferential dikes could alter the stress field in a way that promotes future radial diking and vice versa faulting or slumping within the calderas or on the volcano flanks in response to repeated intrusions could also create a stress field conducive to continued intrusion

a shallow dipping dike fed the 1995 flank eruption at fernandina volcano galapagos observed by satellite radar interferometry satellite radar interferometry data reveal strong localized uplift in a semi circular pattern on the southwest flank of fernandina volcano galapagos where an eruption took place in january to april 1995 the observations show a maximum decrease in radar range of 0 75 m and they are consistent with a model of a shallow dipping dike intrusion feeding this fissure eruption we solve for the best fit single rectangular dislocation dike source using non linear inver sion techniques where simulated annealing searching algo rithm is used to avoid local minima the best fit dike is 3 8 km long 2 3 km high 0 86 m thick and with a 34 dip the total dike volume 7 5 x 10 3 km 3 is 40 of the vol ume of extrusive materials estimated to have been produced during the eruption the data do not permit a sub vertical dike implying that the least principal stress direction is not horizontal as is usually assumed

imaging rapidly deforming ocean island volcanoes in the western galapagos archipelago ecuador using local body wave arrival time tomography methods to determine 3 d seismic velocity structure we imaged the plumbing system of sierra negra volcano galapagos this hot spot volcanic chain includes some of the fastest deforming volcanoes in the world making this an ideal location to study shield volcano plumbing systems we inverted p and s wave arrivals recorded on a 15 station temporary array between july 2009 and june 2011 using an a priori 1 d velocity model constrained by offshore refraction studies with local seismicity from nearby volcanoes as well as the ring fault system the model resolution is good between depths of 3 and 15 5 km the propagation of s waves throughout this volume argues against any large high melt accumulations although a shallow melt sill may exist above 5 km we image a broad low velocity region 25 km laterally below sierra negra at depths 8 15 km no large regional velocity increase is found within the limits of good resolution suggesting that crust is thicker than 15 km beneath the western galapagos archipelago our results are consistent with crustal accretion of mafic cumulates from a large volume magma chamber that may span the boundary between preplume and accreted crust the similarity between our results and those of hawaii leave open the possibility that the crust has also been thickened by under plating

emplacement of dikes sills and crustal magma chambers at divergent plate boundaries abstract a model of dike emplacement at divergent plate boundaries is developed which predicts that below the uppermost 1 3 km of the oceanic crust the number and lengths of dikes in any particular swarm should increase but that the thickness should decrease with depth in the crust these predictions are supported by field observations it is proposed that rapid injections of dikes at divergent plate boundaries may temporarily alter the normal stress field in such a way that at a certain level in the crust subsequent dikes change into sills such sills may develop into crustal magma chambers either when many nearby sills combine into a large one or when an initial sill absorbs the magma of many dikes that enter it in a rapid succession while the sill is liquid for the fastest spreading ridges the initial thickness of a sill that is to develop into a crustal chamber need only attain 20 m whereas at the slowest spreading ridges the initial thickness must exceed 170 m because thin sills are much more likely to form than thick sills the probability of sills developing into crustal chambers increases with dike intrusion frequency hence with spreading rate furthermore the model predicts first that with increasing spreading rate the length of the chamber along the ridge axis should increase and second that the most likely site for magma chambers is at depths of 2 4 km both these predictions are supported by available data

age evaluation and causation of rock slope failures along the western margin of the antrim lava group alg northern ireland based on cosmogenic isotope 36cl surface exposure dating the temporal pattern of postglacial rock slope failure in a glaciated upland area of ireland the western margin of the antrim lava group was evaluated using both 36cl exposure dating of surface boulders on run out debris and 14c dating of basal organic soils from depressions on the debris the majority of the 36cl ages 21 15 ka indicate that major failures occurred during or immediately following local deglaciation 18 17 ka other ages 14 9 ka suggest some later smaller scale failures during the lateglacial and or early holocene the 14c ages 2 36 0 15 cal ka bp indicate the very late onset of organic accumulation and do not provide close limiting age constraints rock slope failure during or immediately following local deglaciation was probably in response to some combination of glacial debuttressing slope steepening and paraglacial stress release later failures may have been triggered by seismic activity associated with glacio isostatic crustal uplift and or permafrost degradation consequent upon climate change the 36cl ages support the findings of previous studies that show the deglacial lateglacial period in northwest ireland and scotland to have been one of enhanced rock slope failure

a surge of bualtar glacier karakoram range pakistan a possible landslide trigger bualtar glacier karakoram range northern pakistan surged during the spring and early summer of 1987 this followed a major episode of three landslides which impacted part of the glacier ablation zone on 30 31 july 1986 in may 1987 surface velocities of 7 m d 1 were measured at one profile down glacier from the landslide deposits where in 1986 velocities were an order of magnitude less surface and hydrological characteristics of the glacier in and down glacier from the landslide deposit were also indicative of surge like behavior in 1987 and a return to pre surge conditions by 1988

repeated holocene rock avalanches onto the brenva glacier mont blanc massif italy a chronology infrequent rock avalanches volume 1 mm3 are long runout processes especially when travelling onto a glacier that may threaten populated mountain valleys rock avalanches also have strong implications are for relief generation and destruction though time both consequences make reconstruction and dating of past events crucial but dense clusters of events documented in one basin that may improve our knowledge of rock avalanche frequency and triggering are very rare here we propose a chronology of seven of the rock ice avalanches that affected a steep glacier basin on the southeast side of the mont blanc during the late holocene a geomorphological study of the runout deposits on the valley floor and the opposite side was combined with the analysis of historical sources and the use of absolute and relative dating methods especially surface exposure dating with cosmogenic nuclides of 18 granite boulders from two deposits these rock ice avalanches are dated ad 1997 and 1920 with a rock volume in the range 2 4 3 6 and 2 106 m3 respectively ad 1767 with a slightly shorter runout ad 1000 1200 with a longer runout c ad 500 the runout of which is uncertain c 2500 bp the determination of which is indirect and c 3500 years with the longest runout there is no distinct relationship between climatic periods and occurrence of these rock avalanches even for the two best documented ones modelling suggests that the 1997 scar was characterized by a permafrost close to 0 c whereas in contrast the 1920 scar was on the contrary located in cold permafrost

modelling rock avalanche propagation onto glaciers abstract ice rock avalanches which occur in glacial environments are controlled by the presence of snow and ice in the moving material and by possible propagation onto icy basal surfaces all these factors contribute to enhancing the flow mobility mixing with ice and snow hampers block collisions and favours dense flow behaviour ice melting reduces granular friction by saturation of the basal material and fluidization effects propagating onto glaciers offers a smooth surface with low shear resistance this work is a review of the best documented ice rock avalanches and focuses on evaluating their mobility for hazard analysis purposes by providing a set of calibrated cases the rock avalanches have volumes ranging from 5 10 6 m 3 to 25 10 6 m 3 we replicate these events by using sph and fem numerical methods assuming frictional and voellmy basal rheologies the voellmy rheology best performs at replicating the landslide propagation among the back analyzed cases the frictional coefficient ranges in the interval 0 03 0 1 the turbulent coefficient within 1000 m s 2 2000 m s 2 the bulk basal friction angle ranges within 2 75 and 14 with values inversely related to event volumes forward selection of the basal friction angle based on event volume allows the replication of the mount cook ice rock avalanche predicting a maximum runout which is less than 4 larger than observed in the perspective of forward modelling large uncertainty is related to the reconstruction of the post event topographies particularly for the sliding surface mixing with ice and snow reduces basal friction proportionally to ice and snow content pure ice has a basal friction which is reduced by about 75 than basal friction of pure rock melting of ice during rock avalanche propagation has been evaluated for the sherman event the frictional heat generated at the glacier surface results in the melting of 86 2 5 9 kg m 2 which could have contributed to a minimum 20 35 10 reduction of the material friction angle through the sole pore pressure generation within a 40 and 20 cm thick shear layer respectively the largest uncertainty is related to the area of contact between rock and ice

automatic detection of alpine rockslides in continuous seismic data using hidden markov models data from continuously recording permanent seismic networks can contain information about rockslide occurrence and timing complementary to eyewitness observations and thus aid in construction of robust event catalogs however detecting infrequent rockslide signals within large volumes of continuous seismic waveform data remains challenging and often requires demanding manual intervention we adapted an automatic classification method using hidden markov models to detect rockslide signals in seismic data from two stations in central switzerland we first processed 21 known rockslides with event volumes spanning 3 orders of magnitude and station event distances varying by 1 order of magnitude which resulted in 13 and 19 successfully classified events at the two stations retraining the models to incorporate seismic noise from the day of the event improved the respective results to 16 and 19 successful classifications the missed events generally had low signal to noise ratio and small to medium volumes we then processed nearly 14 years of continuous seismic data from the same two stations to detect previously unknown events after postprocessing we classified 30 new events as rockslides of which we could verify three through independent observation in particular the largest new event with estimated volume of 500 000 m3 was not generally known within the swiss landslide community highlighting the importance of regional seismic data analysis even in densely populated mountainous regions our method can be easily implemented as part of existing earthquake monitoring systems and with an average event detection rate of about two per month manual verification would not significantly increase operational workload

mass movements and tree rings a guide to dendrogeomorphic field sampling and dating abstract trees affected by mass movements record the evidence of geomorphic disturbance in the growth ring series and thereby provide a precise geochronological tool for the reconstruction of past activity of mass movement the identification of past activity of processes was typically based on the presence of growth anomalies in affected trees and focused on the presence of scars tilted or buried trunks as well as on apex decapitation for the analyses and interpretation of disturbances in tree ring records in contrast clear guidelines have not been established with largely differing or no thresholds used to distinguish signal from noise at the same time processes with a large spatial footprint e g snow avalanches landslides or floods will likely leave growth anomalies in a large number of trees whereas a falling rock would only cause scars in one or a few trees along its trajectory based on the above considerations we examine issues relating to the interpretation and dendrogeomorphic dating of mass movements particular attention is drawn to sampling in terms of sample distribution across a study site the actual selection of trees as well as to sample size i e number of trees sampled based on case studies from snow avalanche debris flow and landslide sites we demonstrate that thresholds can indeed improve dating quality and at the same time minimize noise in time series we also conclude that different thresholds need to be used for different processes and different periods of the reconstruction especially for the early stages of the reconstruction when the number of potentially responding trees will be much smaller this paper seeks to set standards for dendrogeomorphic fieldwork analysis and interpretation for different processes of mass movements

landslide inventories for climate impacts research in the european alps landslides present a geomorphological hazard in alpine regions threatening life infrastructure and property here we present the development of a new regional landslide inventory ri for the european alps this database provides a substantial temporal and spatial picture of landsliding in the alps with particular focus on the swiss and french alps we use segmented models to evaluate recording bias in the temporal record we use scaling relationships to calculate landslide area based on a given volume for similar types of landslide with the result of this being that 9 5 of the landslides recorded in the ri now have area data recorded these landslide area data are then used to examine the log linear trend which exists between landslide area and frequency in inventories we show that this relationship is present for this historical dataset however none of the individual databases nor a unification of these contain a complete record with the small and larger landslides being recorded more consistently the use of segmented models on the temporal distribution of landslides in the ri shows that the post 1970 portion of the database is more reliable highlighted through an improved power law relationship although the frequency of medium sized landslides is still underestimated we show that creating a unified database ri can increase the reliability of datasets and consistency in recording for the use by researchers for attribution and detection studies

interactions between rock avalanches and glaciers in the mont blanc massif during the late holocene rock avalanches are common in the mont blanc massif which is bordered by valleys with large resident and tourist populations and important highways this paper combines historical data with detailed geomorphological mapping stratigraphic observation and absolute and relative dating to interpret several deposits resulting from rock avalanching onto glaciers nineteen rock falls and rock avalanches are described ranging in volume from 10 000 m3 to 10 106 m3 they occurred between 2500 bp and ad 2007 at six sites the events at three sites miage and drus glaciers and tour des grandes jorasses are characterised by short travel distances those at brenva triolet and frebouge glaciers exhibit excessive travel distances interactions between rock avalanches and glaciers are of four types i rock avalanche triggering where glacial and paraglacial controls include debuttressing of rockwalls due to glacier thinning and retreat oversteepening of rock slopes by glacial erosion and effects of glaciers on permafrost ii rock avalanche mobility in which mobility and travel distance are modified by channelling of rock avalanche debris by moraines and valleys incorporation of ice and snow often 50 for large events and irregularities on the glacier surface iii deposit sedimentology where melting of incorporated ice transforms the final deposit by reducing its thickness typically to 5 m and debris of variable thicknesses is juxtaposed in a hummocky deposit with chaotic piles of angular rock debris and iv glacier dynamics where insulating debris deposited upon a glacier produces a debris covered glacier of different dynamics and high elevated scars can favour the formation of small glaciers

drowned islands downstream from the galapagos hotspot imply extended speciation times the volcanic islands of the galapagos archipelago are the most recent products of a long lived mantle hotspot1 2 little is known however of the submarine galapagos platform on which the islands are built or of the cocos and carnegie submarine ridges produced by past motion of the cocos and nazca plates across the hotspot3 4 in 1990 we surveyed selected areas around the galapagos platform and as far east as 85 30 w on the carnegie ridge where we dredged abundant well rounded basalt cobbles from a small sea mount with a terraced summit region cobbles were also dredged from several other seamounts we interpret these features especially the presence of cobbles as evidence for erosion near sea level and conclude that these seamounts were volcanic islands before subsiding to their present depths radiometric ages for these drowned islands range from 5 to 9myr consistent with predicted plate motions they indicate that the time available for speciation of galapagos organisms is much longer than the age range of the existing islands

sedimentary structures on the bengal shelf a multi scale approach to sedimentary fabric interpretation abstract sedimentary structures on the bengal shelf are examined using x radiographic thin section and scanning electron microscopic sem techniques which reveal contrasting depositional processes for the inner and middle shelf as well as for either side of a major submarine canyon indenting the western shelf margin the inner shelf is characterized by tidally produced interlaminated silts and muds that reveal a neap spring cyclicity the cyclicity is more pronounced for the winter season when high discharge monsoon conditions do not obscure the tidal signature on the middle shelf alternating beds of silts and muds probably represent high discharge and low discharge conditions respectively silty beds on the western margin of the submarine canyon are thinner than those found on the eastern margin the western margin receives predominantly fine grained ganges sediments in contrast to the eastern area which receives both ganges and coarser brahmaputra sediments these observations indicate that the submarine canyon presently intercepts westward along shelf sediment transport muddy beds and laminae that appear internally homogeneous in the x radiographs and exhibit faint bedding in thin sections often are composed of resistant protruding and less resistant recessed microlaminae as observed with the sem on the inner shelf resistant microlaminae are composed of fine grained polymineralic equant particles the less resistant microlaminae are composed of large platy illite grains rimmed by smaller platy or lath like illite particles resistant and less resistant microlaminae within middle shelf muddy sediments have the same textural characteristics observed on the inner shelf however both types essentially are monomineralic on the middle shelf the smallest particles within the less resistant microlaminae exhibit an open flocculated structure that may result from higher salinity and or decreased bottom shear stress associated with tidal currents biological structures predominantly occur on the western inner and middle shelf particularly in intervals of high smectite concentrations this relationship may exist because of a preferential organic affinity for expandable minerals providing a favorable substrate for benthic organisms

widespread uplift and trapdoor faulting on galapagos volcanoes observed with radar interferometry volcanic uplift caused by the accumulation of magma in subsurface reservoirs is a common precursor to eruptions1 2 but for some volcanoes uplift of metres or more has not yet led to an eruption3 here we present displacement maps of volcanoes in the galapagos islands constructed using satellite radar interferometry that might help explain this dichotomy we show that all but one of the seven volcanoes on the islands of isabela and fernandina deformed during 1992 99 cerro azul and fernandina erupted4 5 6 during the observation period and show evidence of inflation co eruptive deflation and shallow dyke intrusion in contrast the largest volcano sierra negra has not erupted yet exhibits spatially and temporally variable deformation with a maximum uplift of 2 7 m between 1992 and 1999 which can be modelled by a shallow inflating sill inflation during 1997 98 however was accompanied by trapdoor faulting on a steeply dipping fracture system within the caldera repeated trapdoor faulting over geological time has formed an arcuate intra caldera ridge within sierra negra and may have acted to relax stresses above the magma chamber inhibiting summit eruptions similar processes may help explain large uplift unaccompanied by eruptive activity at other volcanoes

an overview of recent large catastrophic landslides in northern british columbia canada at least thirty eight large catastrophic landslides each either larger than 0 5 m m 3 or longer than 1 km have occurred in northern british columbia in the last three decades the landslides include low gradient flowslides in cohesive sediments long runout rock slides rock avalanches and complex rock slide flows the flowslides have occurred in a variety of sediments including glaciolacustrine silt clay rich till and clay rich colluvium the rock failures have happened in weak shale overlain by sandstone and volcanic rocks the frequency of large landslides in northern british columbia appears to be increasing suggesting a link to climate change d 2005 elsevier b v all rights reserved

a new technique for identifying rock avalanche sourced sediment in moraines and some paleoclimatic implications moraine chronologies are widely used to infer local climate change events and to correlate these events globally based on the assumption that moraines always reflect climatic drivers however this assumption is unreliable in tectonically active terrain because moraines can also be formed by large landslide rock avalanche deposits on glaciers these can affect glacier motion and cause moraines to form while requiring no climate variation and can thus cause significant errors in climatic signals extracted from moraine chronologies to eliminate such errors requires a method for identifying moraines that have been influenced by rock avalanches herein we present and test a new diagnostic technique that unambiguously identifies rock avalanche sediments using newly discovered fine sediment signatures characteristic of rapid high stress comminution we test this technique on holocene moraines in the southern alps new zealand which have previously been interpreted as climatic indicators and demonstrate that some of them unambiguously contain rock avalanche material so their climatic significance is questionable

large rock avalanches triggered by the m 7 9 denali fault alaska earthquake of 3 november 2002 the moment magnitude m 7 9 denali fault alaska earthquake of 3 november 2002 triggered thousands of landslides primarily rock falls and rock slides that ranged in volume from rock falls of a few cubic meters to rock avalanches having volumes as great as 20 10 6 m 3 the pattern of landsliding was unusual the number and concentration of triggered slides was much less than expected for an earthquake of this magnitude and the landslides were concentrated in a narrow zone about 30 km wide that straddled the fault rupture zone over its entire 300 km length despite the overall sparse landslide concentration the earthquake triggered several large rock avalanches that clustered along the western third of the rupture zone where acceleration levels and ground shaking frequencies are thought to have been the highest inferences about near field strong shaking characteristics drawn from interpretation of the landslide distribution are strikingly consistent with results of recent inversion modeling that indicate that high frequency energy generation was greatest in the western part of the fault rupture zone and decreased markedly to the east d 2005 elsevier b v all rights reserved

on origin of near axis volcanism and faulting at fast spreading mid ocean ridges at fast and superfast spreading mid ocean ridges such as the east pacific rise a plate boundary is defined by a narrow tens to hundreds of meters wide neovolcanic zone within which the bulk of the upper oceanic crust is created however detailed near bottom observations indicate that the volcanic construction may occasionally persist several kilometers off of the ridge axis it has been proposed that off axis volcanism manifests tapping of a wide melting region that supplies magma to the ridge axis or spatial migration of magmatic sources in the crust and upper mantle we demonstrate that off axis eruptions may be a natural consequence of variations in magma supply rate even if the ridge axis is stationary in space and the magma delivery is perfectly focussed at the ridge axis theoretical modeling and field observations indicate that off axis volcanism may result from magma emplacement in sills that propagate toward the surface after their characteristic horizontal size exceeds their emplacement depth volcanic construction and faulting due to sill intrusions may contribute to the formation of abyssal hills arguably the most abundant relief form on earth fl 2001 elsevier science b v all rights reserved

dynamics of the 2008 earthquake triggered wenjiagou creek rock avalanche qingping sichuan china abstract the wenjiagou creek rock avalanche was triggered by the 2008 wenchuan earthquake it traveled 4 6 km and left a granular deposit of 1 5 108 m3 in wenjiagou creek valley the dynamics of the rock avalanche were studied through field and laboratory investigations and remote sensing the dynamic course was divided into three segments 1 failing the original slope failed due to the huge earthquake ground accelerations acting on a rock mass weakened by severe karstification 2 falling the rock mass experienced several drops due to abrupt changes in slope and broke into granular debris during collisions with the ground and mountain flanks and 3 flow the broken granular mass flowed approximately 3 km down the valley of wenjiagou creek the transport mechanism of the granular mass of debris was studied by analyzing the structure of the deposit and through ring shear tests a gully incised into the deposit by rainfall runoff and debris flows enabled the internal structure of the deposit to be examined and sampled in cross section the exposed deposit was finest near the base and gradually became coarser towards the surface inverse grading in longitudinal section deposits near the base and on the surface both became finer with increasing travel distance near the base the granular debris experienced the maximum normal and shear stresses and fragmented into the finest grains both normal and shear stresses between the grains gradually decreased from near the base to the surface samples were sheared in a ring shear apparatus to simulate the shearing within the granular debris shear resistance between grains was found to decrease as grains became finer due to pervasive fragmentation which is one of the possible mechanisms by which the granular debris was able to travel a long distance at a high speed

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

the topsar interferometric radar topographic mapping instrument the authors have augmented the nasa dc 8 airsar instrument with a pair of c band antennas displaced across track to form an interferometer sensitive to topographic variations of the earth s surface during the 1991 dc 8 flight campaign data were acquired over several sites in the us and europe and topographic maps were produced from several of these flight lines analysis of the results indicate that statistical errors are in the 2 4 m range while systematic effects due to aircraft motion are in the 10 20 m range the initial results from development of a second generation processor show that aircraft motion compensation algorithms reduce the systematic variations to 2 m while the statistical errors are reduced to 2 3 m

quantifying variable erosion rates to understand the coupling of surface processes in the teton range wyoming short term geomorphic processes fluvial glacial and hillslope erosion and long term exhumation control transient alpine landscapes long term measurements of exhumation are not sufficient to capture the processes driving transient responses associated with short term climatic oscillations because of high variability of individual processes across space and time this study compares the efficacy of different erosional agents to assess the importance of variability in tectonically active landscapes responding to fluctuations in quaternary climate we focus on the teton range where erosional mechanisms include hillslope glacial and fluvial processes erosion rates were quantified using sediment accumulation and cosmogenic dating bedrock and stream sediments results show that rates of erosion are highly variable with average short term rockfall rates 0 8 mm y occurring faster than either apparent basin averaged 0 2 mm y and long term ridge erosion rates 0 02 mm y examining erosion rates separately also demonstrates the coupling between glacial fluvial and hillslope processes apparent basin averaged erosion rates amalgamate valley wall and ridge erosion with stream and glacial rates climate oscillations drive the short term response of a single erosional process e g rockfalls or other mass wasting that may enhance or limit the erosional efficiency of other processes glacial or fluvial while the teton landscape may approach long term equilibrium stochastic processes and rapid response to short term climate change actively perpetuate the transient ruggedness of the topography

on trapdoor faulting at sierra negra volcano galapagos abstract rapid uplift observed during 1992 1997 at sierra negra volcano western galapagos was followed by deformation that we have previously interpreted as trapdoor faulting on an intra caldera fracture system at that time no direct evidence for the trapdoor faulting was available to support this interpretation here we report field evidence of recent faulting at sierra negra and provide direct measurements of the faulting using pixel offsets between satellite radar amplitude backscatter images our field observations carried out in 2001 indicate that recent faulting occurred along the southern part of the intra caldera fault system with maximum offset of at least 0 5 1 m differences between two satellite radar amplitude images show 1 4 0 2 m range change across this fault system this suggests that 1 5 0 2 m of faulting occurred assuming vertical ground displacements consistent with our previous modeling results results of numerical modeling indicate that growing sills can cause faulting of the intrusion roof on outward dipping or nearly vertical faults this occurs at high excess magma pressure when the lateral extent half length of the sill becomes greater than its depth the derived 2 km deep sierra negra sill exhibits trapdoor faulting 3 km south of the center of the sill therefore these modeling results provide a plausible mechanical explanation for the trapdoor fault at sierra negra

unraveling driving factors for large rock ice avalanche mobility large rock ice avalanches have attracted attention from scientists for decades and some of these events have caused high numbers of fatalities a relation between rock slope instabilities in cold high mountain areas and climate change is currently becoming more evident and questions about possible consequences and hazard scenarios in densely populated high mountain regions leading beyond historical precedence are rising to improve hazard assessment of potential rock ice avalanches their mobility is a critical factor this contribution is an attempt to unravel driving factors for the mobility of large rock ice avalanches by synthesizing results from physical laboratory experiments and empirical data from 64 rock ice avalanches with volumes 1x106 m3 from glacierized high mountain regions around the world the influence of avalanche volume water and ice content low friction surfaces and topography on the apparent coefficient of friction as a measure of mobility is assessed in laboratory experiments granular ice in the moving mass was found to reduce bulk friction up to 20 while water led to a reduction around 50 for completely saturated material compared with dry flows evidence for the effects of water as a key driving factor to enhance mobility was also found in the empirical data while the influence of the ice content could not be confirmed to be of much relevance in nature besides liquefaction it was confirmed that mobility increases with volumes and that frictional surface characteristics such as flow paths over glaciers are also dominant variables determining mass movement mobility effects of the topography along the flow path as well as channeling are assumed to be other critical factors the results provide an empirical basis to roughly account for different path and flow characteristics of large rock ice avalanches and to find appropriate ranges for friction parameters for scenario modeling and hazard assessments copyright 2011 john wiley sons ltd

dynamics mobility controlling factors and transport mechanisms of rapid long runout rock avalanches in china abstract the dynamics and occurrence conditions of 43 rapid and long run out rock avalanches in china were summarized their dynamics were classified into 5 types the standard dynamic type was designated to be fail squirt and flow where part of the landslide path always has a parabolic airborne course because the slide body has an initial speed and the toe of the surface of rupture projects the landslide into the air the occurrence conditions of rock avalanches of the standard dynamic type are huge kinetic energy elevated toe to the surface of rupture and enough transport space to run out into the occurrence conditions of the other four types were then compared with the standard dynamic type statistical analysis showed that volume topography huge kinetic energy and an elevated toe to the surface of rupture were the principal factors controlling mobility in the rock avalanches four of the rapid long run out rock avalanches each in a different geological setting were then examined in more detail to reveal the transport mechanisms leading to their high speed and long runout the results suggested that besides their huge kinetic energy high pore water pressure produced by undrained shear and elastic energy released by grain fragmentation were the main transport mechanisms contributing to the long travel distances and high speeds of rock avalanches field investigation indicated that air was involved during the transport but whether it influenced the transport or how much the influence was is still much disputed

the impact of supraglacial debris on proglacial runoff and water chemistry debris is known to influence the ablation topography and hydrological systems of glaciers this paper determines for the first time how these influences impact on bulk water routing and the proglacial runoff signal using analyses of supraglacial and proglacial water chemistry and proglacial discharge at miage glacier italian alps debris does influence the supraglacial water chemistry but the inefficient subglacial system beneath the debris covered zone also plays a role in increasing the ion contribution to the proglacial stream daily hydrographs had a lower amplitude and later discharge peak compared to clean glaciers and fewer diurnal hydrographs were found compared to similar analysis for haut glacier d arolla we attribute these observations to the attenuating effect of the debris on ablation smaller input streams on the debris covered area a less efficient subglacial system and possible leakage into a raised sediment bed beneath the glacier strongly diurnal hydrographs are constrained to periods with warmer than average conditions average weather conditions result in a hydrograph with reverse asymmetry conductivity and discharge commonly show anti clockwise hysteresis suggesting the more dilute rapidly routed melt component from the mid glacier peaks before the discharge peak with components from higher up glacier and the debris covered areas arriving later at the proglacial stream the results of this study could lead to a greater understanding of the hydrological structure of other debris covered glaciers with findings highlighting the need to include the influence of the debris cover within future models of debris covered glacier runoff

catastrophic landslide deposits in the karakoram himalaya in july 1986 three catastrophic landslides deposited about 20 x 106 cubic meters of debris on bualtar glacier in the karakoram himalaya a sudden acceleration and superficial breakup of the glacier provided an opportunity to examine the fresh deposits in depth beneath a surface layer of large boulders finer materials mainly sand and silt made up half of the total volume the fine materials were formed during the rock avalanche from mostly intact massive rock of the source zone velocity estimates suggest that this disaggregation occurred in less than 2 minutes coarse materials remained in bands of uniform lithology but the fine materials had diffused throughout the landslides a small amount of carbonate appears to have been calcined by frictional heating presumably at the base of the initial sliding masses these observations are relevant to understanding the mechanisms of catastrophic landslides other nearby rock avalanche deposits indicate that landslides are an important geomorphic process in the area and that they pose a continuing risk to human activity

a distributed energy balance melt model of an alpine debris covered glacier distributed energy balance melt models have rarely been applied to glaciers with extensive supraglacial debris cover this paper describes the development of a distributed melt model and its application to the debris covered miage glacier western italian alps over two summer seasons sub debris melt rates are calculated using an existing debris energy balance model deb model and melt rates for clean ice snow and partially debris covered ice are calculated using standard energy balance equations simulated sub debris melt rates compare well to ablation stake observations melt rates are highest and most sensitive to air temperature on areas of dirty crevassed ice on the middle glacier here melt rates are highly spatially variable because the debris thickness and surface type varies markedly melt rates are lowest and least sensitive to air temperature beneath the thickest debris on the lower glacier debris delays and attenuates the melt signal compared to clean ice with peak melt occurring later in the day with increasing debris thickness the continuously debris covered zone consistently provides 30 of total melt throughout the ablation season with the proportion increasing during cold weather sensitivity experiments show that an increase in debris thickness of 0 035 m would offset 1 c of atmospheric warming

the alps with little ice evidence for eight holocene phases of reduced glacier extent in the central swiss alps glacially deformed pieces of wood organic lake sediments and clasts of reworked peat have been collected in front of alpine glaciers since ad 1990 the palaeoglaciological interpretation of these organic materials is related to earlier phases of glacier recession surpassing that of today s shrunken glaciers and to tree growth and peat accumulation in the valleys now occupied by the glaciers glacial transport of the material is indicated by wood anatomy incorporated silt sand and gravel particles missing bark and deformed treerings a total of 65 samples have been radiocarbon dated so far and clusters of dates provide evidence of eight phases of glacier recession 9910 9550 9010 7980 7250 6500 6170 5950 5290 3870 3640 3360 2740 2620 and 1530 1170 calibrated years bp allowing for the timelag between climatic fluctuations glacier response and vegetation colonization these recession phases may lag behind climatic changes by 100 200 years

stress interaction between magma accumulation and trapdoor faulting on sierra negra volcano galapagos abstract understanding the state of stress within volcanoes and how it changes with active geophysical processes is important to assess when and where magma may propagate to the surface and initiate an eruption observations of volcanic deformation help to constrain parameters of models that can be used to describe these processes and to calculate the resulting stress changes within volcanoes here i use geodetic observations to constrain elastic dislocation models of magma accumulation and faulting at sierra negra volcano galapagos in the years before the october 2005 eruption which was the first eruption at sierra negra since 1979 both insar and gps data document a remarkable story of 5 m pre eruption uplift during 1992 2005 which was accompanied by at least three trapdoor faulting events on an intra caldera fault system in january 1998 april 2005 and just before the eruption in october 2005 the pattern of uplift observed in the insar data from different time periods during 1992 2005 is consistent with filling and pressurization of a 2 2 km deep sill under the caldera modeling results for the trapdoor faulting in april 2005 on the other hand indicate that slip occurred on a thrust fault that dips steeply 71 in towards the center of the caldera and extends from the surface down to the sill at 2 2 km depth independently the calculated stress changes caused by the inflating sill show that the coulomb failure stress change cfs at the fault s location is maximized on a 72 dipping thrust fault agreeing almost exactly with the deformation modeling result and implying that the inflation triggered the faulting the calculations also show that the cfs for optimally oriented faults any strike and dip is significantly larger in the southern part of the caldera where the faulting took place than at any other location the trapdoor faulting in turn relieved the pressure within the sill but caused compression to the south of the faults this suggests that while the faulting provides a mechanism for the sill to thicken and postpone eruptions it also prevents the sill from growing to the south

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