an examination of controls on debris flow mobility evidence from coastal british columbia we characterize and consider controls to runout distance of debris slides and debris flows using 1700 field observations supplemented by air photograph interpretation from coastal british columbia we examine the role of slope on deposition and scour and determine that they occur on steeper and flatter slopes respectively than previously reported mean net deposition occurred on slopes between 18 and 24 for open slope failures and between 12 and 15 for channelized debris flows we demonstrate a practical method for estimating both entrainment and runout in the field and in a gis and provide an example entrainment map for vancouver island british columbia we consider other controls to post failure landslide mobility including the role of gullies and stream channels roads and benches and intact forests shallow landslides that hit streams and gullies at acute angles had a high probability of transforming into a channelized debris flow whereas landslides that hit streams and gullies at obtuse angles did not forests played a substantial role in landslide runout debris flows travelling through a logged slope deposited much of their load when hitting a forest boundary and stopped entirely within 50 m of that boundary in 72 of the cases examined roads also tended to stop or reduce the size of open slope debris flows in 52 of the cases the results are expected to be useful to land management applications in regions with frequent shallow landsliding

debris flows and debris torrents in the southern canadian cordillera in canada debris torrents also referred to as channelized debris flows occur in parts of british columbia alberta and the yukon at least 17 deaths and an estimated 100 million of damage to bridges and property can be attributed to this natural hazard the debris mainly comprises large boulders rock fragments gravel to clay sized material tree and wood mulch materials that accumulate in the mountain creeks to be susceptible to a debris torrent a creek must have a drainage area within a critical range a profile that is sufficiently steep an accumulation of debris and some form of triggering mechanism the most common triggering mechanism is an extreme water discharge which may result from a very intense rainfall or a temporary damming of the creek in western canada the resulting torrents involve masses of debris typically less than 50 000 m3 that travel down creeks at speeds between 3 and 12 m s several passive and active forms of mitigation can be used to reduce the impact of debris to

wildfire disturbance and shallow landsliding in coastal british columbia over millennial time scales a numerical modelling study an algorithm for wildfire occurrence is introduced for incorporation into a numerical model of drainage basin evolution within the model fire return intervals are determined using a stochastic rule set and fire sizes are assigned according to a pareto distribution a weibull distribution was fit to millennial scale lake charcoal data for calibration of fire return intervals in this study while data for the olympic peninsula were used to determine the fire size distribution loss of tree root strength resulting from stand replacing wildfires has been found to be comparable to loss after timber harvesting hence data for increased shallow landslide activity associated with logging were used to calibrate transport equations for years following wildfire incidence a weathering relation is incorporated in the model which drives the supply of sediment when sediment supply is depleted in the model the shallow landsliding module shuts off until new material is available for transport time since last fire analysis indicates that the weibull parameters defined for the clayoquot charcoal data produce results that are weighted too heavily towards recent fires sensitivity analysis was undertaken suggesting alternative values may be more reasonable for further model runs the introduction of a weighted probability factor for aspect whereby south facing slopes have a higher likelihood of fire initiation was not found to significantly affect patterns of fire age in the landscape patterns of net topographic change after 6000 years of model run time indicate that greatest net erosion is found on steep upper slopes with the highest deposition occurring in hillslope hollows and low order channels depositional grid cells in interfluves show a variable response to the inclusion of wildfire in the model net erosion occurs over a relatively low proportion of hillslope area with wildfire model runs showing a strong erosional signal in these locations for stream grid cells the additional deposition due to the inclusion of wildfire in model runs is about 9 10 for 1st to 3rd order streams overall deposition rates increase with decreasing stream order reflecting greater hillslope channel coupling in low order streams

analysis of landslide frequencies and characteristics in a natural system coastal british columbia two hundred and one debris slides and debris ows were analyzed in a 286 km2 study area on the west coast of vancouver island british columbia canada the study area remains essentially untouched by humans and therefore affords a natural setting in which to examine slope processes landslides were identi ed and characterized on aerial photographs from 1 15 000 to 1 31 680 and were then mapped and transferred to a gis for analysis based on detailed landslide surveys we propose a new method to accurately determine volume of landslides of this type by measured total area results indicate average denudation rates of 56 m3 y 1 km 2 and higher natural rates of failure than analogous regions in coastal british columbia in contrast the landslide rates are substantially less than those from forested watersheds landslide distribution is spatially clustered in air photograph epochs and we propose intense storm cells within regional events as the causal mechanism further failures occurred preferentially over the west coast crystalline complex by 1 4 times a metamorphic assemblage of gabbros schists and amphibolites but 1 5 times less often over the island plutonic suite a granitic intrusive formation the former result represents a new nding while the latter corroborates ndings of previous authors we examined magnitude frequency relationships of the data set and present for the rst time a strong argument that the rollover effect is not merely an artefact but is instead a consequence of the physical characteristics of the landslides themselves we subsequently analyzed magnitude frequency relationships from two other complete data sets from coastal british columbia and produced a family of curves corroborating this result copyright 2004 john wiley sons ltd

effect of forest harvesting on hydrogeomorphic processes in steep terrain of central japan abstract forest harvesting activities affect various hydrogeomorphic processes in forest terrain including increases in occurrence of mass movements i e landslides and debris flows and changes in sediment transport rate in channels thus the influence of harvesting on these processes needs to be assessed to protect aquatic ecosystems in steep terrain with frequent mass movement relationships between rainfall magnitude and frequency of mass movements associated with forest harvesting are needed to develop improved strategies for disaster prevention we examined the effects of forest harvesting on the frequency of mass movements in the steep sanko catchment central japan using aerial photographs for six different years covering 1976 to 2003 we also investigated the spatial distribution of sediment stored in the system as well as sediment transport rate in selected subcatchments by field surveys landslides occur during moderate rainfall events return period of daily rainfall 25 years after harvesting the occurrence of mass movements substantially altered the volume of sediment storage in the channel that links sediment supply from hillslopes with sediment yield downstream however the volume and spatial distribution of sediment deposits in headwater channels were not clearly related to forest age because of the redistribution and evacuation of sediment by debris flows bedload transport rate was highly affected by sediment storage volume whereas suspended sediment concentration was affected by the area of exposed sediment along channels that was carved by debris flows thus the effect of harvesting on hydrogeomorphic processes cannot be estimated simply by the elapsed time after forest harvesting rainfall magnitude and the history of mass movements need to be considered to better understand these linkages

reconstructing depositional processes and history from reservoir stratigraphy englebright lake yuba river northern california 1 reservoirs provide the opportunity to link watershed history with its stratigraphic record we analyze sediment cores from a northern california reservoir in the context of hydrologic history watershed management and depositional processes observations of recent depositional patterns sediment transport calculations and 137cs geochronology support a conceptual model in which the reservoir delta progrades during floods of short duration days and is modified during prolonged weeks to months drawdowns that rework topset beds and transport sand from topsets to foresets sediment coarser than 0 25 0 5 mm deposits in foresets and topsets and finer material falls out of suspension as bottomset beds simple hydraulic calculations indicate that fine sand 0 063 0 5 mm is transported into the distal bottomset area only during floods the overall stratigraphy suggests that two phases of delta building occurred in the reservoir the first from dam construction in 1940 to 1970 was heavily influenced by annual prolonged 20 m drawdowns of the water level the second built on top of the first reflects sedimentation from 1970 to 2002 when the influence of drawdowns was less sedimentation rates in the central part of the reservoir have declined 25 since 1970 likely reflecting a combination of fewer large floods changes in watershed management and winnowing of stored hydraulic mining sediment

the effects of logging on frequency and distribution of landslides in three watersheds on vancouver island british columbia abstract three hundred and sixty three landslides in three watersheds that totaled 382 km2 were identified from air photographs beginning at a date that preceded logging to the present the three watersheds all lie on vancouver island however they have different precipitation regimes topography and amounts logged landslide areas in the watersheds varied in size from 200 m2 to more than 1 ha nearly 80 of the landslides were debris slides 15 were debris flows and the remainder primarily rock falls following logging the number of landslides increased substantially in all watersheds although the amount of increase was variable approximately 11 3 and 16 times in macktush creek artlish river and nahwitti river respectively other analyses of changes in landslide density also produced highly variable results with the number of landslides increasing between 2 4 and 24 times further 2 12 times more landslides reached streams following logging activities densities for landslides impacting streams increased for the period of record from 1 5 to 10 times following logging activities the densities were substantially greater where only landslides that reached streams since development began in a watershed were considered roads had the greatest spatial impact in the watersheds compared to their total area with frequencies determined to have increased by 27 12 and 94 times for macktush artlish and nahwitti respectively the results highlight the relative impact of roads and their role in slope stability

estimates of three dimensional rupture surface geometry of deep seated landslides using landslide inventories and high resolution topographic data abstract deep seated landslides cause significant damage to the built environment characterizing the shear surface and volume of these features is often limited to intensive site specific monitoring or at a larger scale generalized empirical relationships developed from change analysis however there is limited means of generalizing regional scale rupture surface information for deep seated landslides where deposits still overlay much of the failure surface herein a method is proposed that uses high resolution bare earth digital elevation models with an inventory of mapped landslide extents to gather first order estimates of three dimensional rupture surface geometries and volumes for rotational and compound landslide features at a regional scale this approach is first calibrated to a suite of well characterized landslides and then applied to over eight hundred deep seated landslides in three different geologic regimes estimates of landslide area volume relationships are proposed that are consistent with previous empirical assessments the aforementioned relationships describe mean landslide thickness added relationships relating landslide area to maximum landslide thickness are proposed the presented results suggest limits on magnitudes of depth with landslide classification and relief between geologic settings consistent with prior research it is observed that landslide area exhibits a first order control on maximum and mean landslide thickness but further insight is provided towards the influence of a limited set of landslide classification which exhibit controls on the range of magnitudes observed for maximum landslide depth associated with failure lastly the implications and limitations of the developed three dimensional mapping approach is discussed

supply and dispersal of flood sediment from a steep tropical watershed hanalei bay kaua i hawai i usa in contrast to many small mountainous watersheds in temperate coastal regions where fl uvial discharge and wave energy commonly coincide deposition and reworking of tropical fl ood sediment can be seasonally decoupled and this has important implications for coral reef ecosystems an understanding of the interaction between tropical fl ood sedimentation and wave climate is essential to identifying and mitigating effects of watershed changes on coral reefs as urbanization and climate change proceed sedimentary facies and isotopic properties of sediment in hanalei bay on the island of kaua i hawai i usa were used to assess deposition and reworking of fldeposits from the hanalei river in a case study demonstrating the potential ecosystem effects of runoff from a steep tropical watershed in hanalei bay the youngest and thickest terrigenous sediment was consistently present near the river mouth and in a bathymetric depression that acted as at least a temporary sediment sink during this 2 yr study the largest fl ood events occurred in late winter and spring 2006 substantial terrestrial sediment delivered by those fl oods still remained in the bay as of june 2006 because oceanic conditions were not suffi ciently energetic to transport all of the sediment offshore additional sediment was deposited in the bay by a summer 2006 fl ood that coincided with seasonal low wave energy in most years fl ood sediment accumulating in the bay and on its fringing reefs would be remobilized and advected out of the bay during winter when the wave climate is energetic turbidity and sedimentation on corals resulting from late spring and summer fl oods during low wave energy could have a greater impact on coral reef ecosystems than fl oods in other seasons an effect that could be exacerbated if the incidence and sediment load of tropical summer fl oods increase due to urbanization and climate change

sediment transfer by shallow landsliding in the queen charlotte islands british columbia despite the importance of landsliding in routing sediment through mountainous drainage basins few studies have documented landsliding rates over extended time and space scales we have investigated landsliding in surficial material in the queen charlotte islands using a large inventory of events derived from aerial photography covering an area of 166 7 km 2 the mean erosion rate for shallow landsliding is 0 10 mm a 1 which is at the upper end of shallow landsliding rates observed in the pacific northwest and coastal british columbia but several orders of magnitude lower than rock based landsliding rates reported in the literature probability distributions for landslide area and volume are somewhat convex in form flattening of the curve found at low magnitudes may be due to sampling bias or physical mechanisms inhibiting failure and the steepening for high values may exist because the sampling period is not long enough to adequately represent large events landslides generally initiate on hillslope gradients greater than 0 50 0 60 the largest numbers of landslides occur on south to southwest facing slopes and east to northeast facing slopes most events occur on concave and straight hillslopes in upper slope positions landsliding rates were found not to be af fected by rock type hillslopes in the queen charlotte islands are often mantled by weathered quaternary deposits and hence landsliding events are not directly controlled by weathering of bedrock about 31 of landslides identified in this study deposited material in stream reaches with about 83 of these landslides deposited in reaches with gradients between 3 and 10 resume malgre la grande contribution des glissements de terrain a acheminer des sediments a travers des bassins de drainage montagneux peu d etudes ont documente les taux de glissements de terrain sur une longue periode de temps et sur de grandes superficies nous avons fait des recherches sur des glissements de materiaux de surface dans les iles de la reine charlotte en utilisant un grand inventaire d evenements tires de photographies aeriennes couvrant une re

the 17 march 2005 kuzulu landslide sivas turkey and landslide susceptibility map of its near vicinity landslides are common natural hazards in the seismically active north anatolian fault zone of turkey although seismic activity heavy rainfall channel incisions and anthropogenic effects are commonly the main triggers of landslides on march 17 2005 a catastrophic large landslide in sivas northeastern of turkey the kuzulu landslide was triggered by snowmelt without any other precursor the initial failure of the kuzulu landslide was rotational following the rotational failure the earth material in the zone of accumulation exhibited an extremely rapid flow caused by steep gradient and high water content the agnus creek valley where kuzulu village is located was filled by the earth flow material and a landslide dam was formed on the upper part of agnus creek the distance from the toe of the rotational failure down to the toe of the earth flow measured more than 1800 m with about 12 5 million m3 of displaced earth material the velocity of the kuzulu landslide was extremely fast approximately 6 m s the main purposes of this study are to describe the mechanism and the factors conditioning the kuzulu landslide to present its environmental impacts and to produce landslide susceptibility maps of the kuzulu landslide area and its near vicinity for this purpose a detailed landslide inventory map was prepared and geology slope aspect elevation topographic wetness index and stream power index were considered as conditioning factors during the susceptibility analyses the conditional probability approach was used and a landslide susceptibility map was produced the landslide susceptibility map will help decision makers in site selection and the site planning process the map may also be accepted as a basis for landslide risk management studies to be applied in the study area

deep structure of the southern kerguelen plateau southern indian ocean from ocean bottom seismometer wide angle seismic data wide angle seismic data collected during the kerguelen ocean bottom seismometer experiment provide the first images of the deep structure of the southern kerguelen plateau and support a new interpretation of the origin of the plateau velocity models based on travel time inversions and reflectivity synthetic seismograms show a 22 km thick crust composed of 1 6 km of sedimentary cover 5 3 km of upper crust 11 0 km of lower crust and a 4 to 6 km thick reflective zone immediately above moho velocities in the upper crust from 3 8 4 5 km s at top to 6 0 6 5 km s at bottom are consistent with the basaltic nature of this layer the top of which was sampled during the ocean drilling program velocities in the lower crust increase continuously from 6 60 km s at the top to 6 90 km s at 19 5 km depth the reflective zone at the base of the crust identified by wide angle reflections is observed only along the nnw sse direction it consists of alternating high and low velocity layers with an average velocity of 6 70 km s in the nnw sse direction and 6 90 km s in the perpendicular direction strong azimuthal anisotropy is also observed in the upper mantle with velocities of 8 60 and 8 00 km s in the nnw sse and e w directions respectively the absence of high velocities at the base of the crust that characterizes many large volume mafic provinces the reflective lower crust and anisotropy in upper mantle suggest that the southern kerguelen plateau represents a stretched continental fragment overlain by basaltic flows isolated from the antarctic margin during the early opening of the indian ocean

new style of honeycomb structures revealed on 3d seismic data indicate widespread diagenesis offshore great south basin new zealand abstract in the great south basin within the eocene section at time depths around 700 900 ms two way time below the seafloor unusual features are observed on 3d seismic data closely associated with polygonal faults the features referred to as honeycomb structures hs cover an area of 600 km 2 are packed circular oval to polygonal depressions 150 400 m across in plan view and several to 10 m in amplitude polygonal faults rapidly die out at the marshall paraconformity which is overlain by the oligocene penrod formation hence the polygonal faults are inferred to have formed prior to the marshall paraconformity and they cross cut hs features consequently the top of the hs probably formed at burial depths of around 375 500 m which is their decompacted depth below the paraconformity the interval containing hs is about 125 m vertical thick there are several possible origins for the hs the most probable is related to bulk contraction of the sediment volume accompanied by fluid expulsion which suggests a diagenetic origin in particular the opal a ct transition there are actually two polygonal fault systems pfs present in the area the southern tier 1 pfs lies laterally to the hs and overlaps with it the northern pfs tier 2 lies above the hs appears to be independent of the hs and formed in the upper 200 300 m of the sediment column the tier 1 pfs probably formed by shear failure related to the same diagenetic effects that caused the hs

instability in eight sub basins of the chilliwack river valley british columbia canada a comparison of natural and logging related landslides logging causes increased landslide frequency in british columbia in this study the slope type initiation location aspect rate bedrock geology and size of mass movements located in eight logged tributary valleys of the chilliwack river valley are investigated a landslide inventory was created by digitizing landslides identified on aerial photographs dating from 1941 to 2002 this database was analysed using qualitative observations and simple statistical tests and a comparison between natural and logging related landslides was made slope tests displayed a significant difference between natural and logging related events indicating that on average logging related landslides require lower slope gradients to initiate than natural events although aspect initiation location and landslide type did not show a significant relationship between natural and logging related landslides they do suggest subtle differences landslide rate was calculated and compared for natural and logging related landslides it was significantly higher for logging related events attaining a maximum of 31 times the natural rate in 1978 and an overall average increase of nine times the natural rate logging related landslides were on average smaller than natural landslides but this nevertheless resulted in a 3 1 times increase in area affected by logging related landslides compared to natural landslides geology may influence landslide frequency as well it appears to be higher over the less resistive sedimentary rocks of the cultus formation and chilliwack group and lower in granodioritic areas finally roads affected slope stability more than clearcuts in the early decades of the study but this effect decreased over time suggesting a correlation with improved road construction

scratching the surface estimating dimensions of large igneous provinces a study of five major basaltic provinces including oceanic plateaus volcanic passive margins and continental flood basalts shows that they are voluminous constructions of extrusive igneous rock underlain by intrusive rock crustal thickness ranges from 20 to 40 km and lower crust is characterized by high 7 0 7 6 km s seismic velocities volumes and emplacement rates derived for two oceanic plateaus the ontong java and kerguelen broken ridge reveal short lived pulses of increased global crustal production and suggest an origin involving the lower mantle the ontong java rate of emplacement may have exceeded the contemporaneous global production rate of the entire mid ocean ridge system despite the importance off large igneous provinces in studies of mantle dynamics and the global environment scarce age and deep crustal data necessitate intensified efforts in seismic imaging and scientific drilling in a range of such features

quantifying rainfall controls on catchment scale landslide erosion in taiwan landslide erosion is a dominant hillslope process and the main source of stream sediment in tropical tectonically active mountain belts in this study we quantified landslide erosion triggered by 24 rainfall events from 2001 to 2009 in three mountainous watersheds in taiwan and investigated relationships between landslide erosion and rainfall variables the results show positive power law relations between landslide erosion and rainfall intensity and cumulative rainfall with scaling exponents ranging from 2 94 to 5 03 additionally landslide erosion caused by typhoon morakot is of comparable magnitude to landslide erosion caused by the chi chi earthquake mw 7 6 or 22 24 years of basin averaged erosion comparison of the three watersheds indicates that deeper landslides that mobilize soil and bedrock are triggered by long duration rainfall whereas shallow landslides are triggered by short duration rainfall these results suggest that rainfall intensity and watershed characteristics are important controls on rainfall triggered landslide erosion and that severe typhoons like high magnitude earthquakes can generate high rates of landslide erosion in taiwan copyright 2012 john wiley sons ltd

using the sediment record in a western oregon flood control reservoir to assess the influence of storm history and logging on sediment yield abstract dorena lake a flood control reservoir with a 686 km2 watershed in the western cascade mountains of oregon contains a 50 year record of sediment deposition by measuring the amount of lake sediment performing 137cs dating and examining the stratigraphy of sediment cores information was obtained about variations in the sediment yield of the watershed the average yield for 50 years is 108 tons km2 year and rates for shorter time periods vary from 42 to 269 tons km2 year depending on the time of average and the occurrence of large storm events a comparison of sediment yield values with timber harvesting rates and with the number of high discharge days during different time periods implies that sediment yield is controlled primarily by flood magnitude and frequency the amplitude of variation in yield that might be produced by changes in logging rates or methods is too small to be detected with the methods used in this study because in large watersheds 1 the effects of localized events tend to be averaged out and 2 sediment delivery ratios are generally low also the reservoir was constructed after a significant portion of the watershed had been logged so the data cannot be compared with pre disturbance sediment yields this study shows that reservoirs in the western cascades are worthy of further study but information is needed to constrain reservoir trap efficiency and problems of scale in large watersheds may hinder the detection of land use influences on sedimentation

experimental study of a kiglapait marginal rock and implications for trace element partitioning in layered intrusions abstract experiments on a chilled marginal rock from the kiglapait intrusion labrador have been performed in order to constrain the partitioning behaviour of major and trace elements during formation of kiglapait lower zone lz cumulates at 0 1 mpa and f o 2 close to fmq the liquidus is bracketed between 1225 and 1212 c and the only liquidus phases are plagioclase an 73 74 and olivine fo 82 85 in contrast lz troctolites contain fo 67 5 olivine and an 63 4 plagioclase plagioclase melt partition coefficients d s for li ti rb sr y zr ba la and eu determined by ion microprobe analysis of run products are similar to those for other basaltic systems but differ systematically from apparent d s calculated from bulk analyses of lz plagioclases and modelled liquid compositions obtained by summation the discrepancies in d s and phase compositions are inconsistent with diffusion controlled boundary layer growth crystallisation of trapped intercumulus liquid is quantitatively plausible however a the volume of liquid required to reconcile experimental and model d s 20 1 is larger than that estimated from observed proportions of intercumulus phases 11 2 and b this mechanism alone cannot reduce x an in lz plagioclases due to very slow al si interdiffusion the discrepancy between experiment and model is best resolved if the parental melt to lz cumulates was more evolved higher fe mg na ca ree and alkalis lower sr than the summed bulk composition in accord with a recent revision of the kiglapait fe mg based on olivine compositions

sediment production from forest road surfaces erosion on roads is an important source of fine grained sediment in streams draining logged basins of the pacific northwest runoff rates and sediment concentrations from 10 road segments subject to a variety of traffic levels were monitored to produce sediment rating curves and unit hydrographs for different use levels and types of surfaces these relationships are combined with a continuous rainfall record to calculate mean annual sediment yields from road segments of each use level a heavily used road segment in the field area contributes 130 times as much sediment as an abandoned road a paved road segment along which cut slopes and ditches are the only sources of sediment yields less than 1 as much sediment as a heavily used road with a gravel surface

effects of forest harvesting on the occurrence of landslides and debris flows in steep terrain of central japan landslides and debris flows associated with forest harvesting can cause much destruction and the influence of the timing of harvesting on these mass wasting processes therefore needs to be assessed in order to protect aquatic ecosystems and develop improved strategies for disaster prevention we examined the effects of forest harvesting on the frequency of landslides and debris flows in the sanko catchment central japan using nine aerial photo periods covering 1964 to 2003 these photographs showed a mosaic of different forest ages attributable to the rotational management in this area since 1912 geology and slope gradient are rather uniformly distributed in the sanko catchment facilitating assessment of forest harvesting effects on mass wasting without complication of other factors trends of new landslides and debris flows correspond to changes in slope stability explained by root strength decay and recovery the direct impact of clearcutting on landslide occurrence was greatest in forest stands that were clearcut 1 to 10 yr earlier with progressively lesser impacts continuing up to 25 yr after harvesting sediment supply rate from landslides in forests clearcut 1 to 10 yr earlier was about 10 fold higher than in control sites total landslide volume in forest stands clearcut 0 to 25 yr earlier was 5 8 10 3 m 3 km 2 compared with 1 3 10 3 m 3 km 2 in clearcuts 25 yr indicating a fourfold increase compared with control sites during the period when harvesting affected slope stability because landslide scars continue to produce sediment after initial failure sediment supply from landslides continues for 45 yr in the sanko catchment to estimate the effect of forest harvesting and subsequent regeneration on the occurrence of mass wasting in other regions changes in root strength caused by decay and recovery of roots should be investigated for various species and environmental conditions copyright 2007 john wiley sons ltd

erosion in mediterranean mountain landscapes during the last millennium a quantitative approach based on lake sediment sequences iberian range spain abstract land degradation and soil erosion are key environmental problems in mediterranean mountains characterized by both a long history of human occupation and strong seasonality of hydrological regimes experimental monitored catchments have identified main controlling factors on erosion dynamics but because of the short time span of the instrumental measurements they do not integrate the complete temporal and spatial variability of these environments to obtain some long term series of mediterranean landscape evolution we propose a novel strategy based on multi proxy analyses of lake sediments aimed to quantify sediment delivery and erosion dynamics karstic lakes in the iberian range central spain provide an opportunity to reconstruct the depositional evolution of the watersheds and to evaluate the response to both the variable anthropogenic impacts and climate forcings during the last 1000 years the most significant periods of increased sediment delivery 26 483 t km yr 1 in the iberian range sites took place during the 15th 16th and 18th 19th centuries as a result of large land use changes and land clearing positive synergies between increasing human population and more humid periods led to peaks in sediment deliver during some phases of the little ice age recent changes associated with the rural exodus and land abandonment during mid 20th century are more clearly shown in larger watersheds by decreased sediment delivery to the lakes due to the re vegetation of the landscape 6 200 t km yr 1 this new integrated approach based on long term lake sequences provides a longer perspective of erosion processes in mediterranean watersheds and validates the main factors identified in monitoring surveys land cover and surface formations erodibility in both settings lakes and experimental catchments most sediment delivery occurs during flooding events measured and reconstructed values show comparable large ranges underlying the punctuated nature of sediment dynamics in mediterranean landscapes at decadal and centennial scales

linkage of sediment supply and transport processes in miyagawa dam catchment japan 1 linkages between sediment supply by episodic geomorphic processes obtained from aerial photographs and field surveys and sediment transport estimated from changes in sediment deposition behind a large dam were investigated in the miyagawa dam catchment central japan a total of 6667 landslides were confirmed in the period from 1965 to 2000 on the basis of seven temporal pairs of aerial photographs both the occurrence of landslides and discharge into the dam lake affect sediment yield indicating that fluvial systems in miyagawa dam catchment are supply limited with respect to sediment sediment yields are affected by not only the initial failed volume of landslides but also the mobility of landslides and debris flows in miyagawa dam catchment percentages of landslides reaching channels varied from 56 in 1997 2000 to 75 in 1976 1981 and were correlated with maximum hourly rainfall in addition the mobility of debris flows was higher during periods with high maximum instantaneous discharge compared to lower discharge suggesting that the water content both in initially failed materials and transported sediment controlled their mobility topography also affected the mobility of landslides debris flows for catchments 0 1 km2 the percentage of channel network length impacted by debris flows decreased with increasing catchment area due to reduced channel gradient thus both the magnitude of rainfall runoff events and the catchment topography affect how landslide sediment contributes to sediment yield at the large catchment scale

complex mass wasting response of drainage basins to forest management in coastal british columbia the impacts of logging activities on mass wasting were examined in five watersheds in the coastal mountains of british columbia historical aerial photos were used to document mass wasting events and their occurrence was related to logging activities in the study basins logged and forested areas were compared in terms of mass wasting magnitude and frequency with reference to site characteristics the recovery time of the landscape after logging was assessed bedrock type and basin physiography had no identifiable effect on mass wasting frequency and magnitude mass wasting failure was primarily controlled by slope gradient basin vulnerability increased following clearcutting relative to forested areas in that mass wasting was initiated on gentler slopes the volume of sediment produced from logged slopes is of the same order as that from forested areas which are steeper by as much as 10 in both logged and forested areas the size distribution of mass wasting events follows an exponential distribution however the variability in mass wasting size in forested areas is much higher than that obtained for logged areas the recovery time after forest harvesting is over 20 years which confirms published estimates based on vegetation reestablishment continuous disturbance of the basin however may extend the recovery time for the whole basin well beyond 20 years

sources and transport of terrestrial organic matter in vancouver island fjords and the vancouver washington margin a multiproxy approach using d13corg lignin phenols and the ether lipid bit index the branched and isoprenoid tetraether bit index a ratio of marine and terrestrial glycerol dialkyl glycerol tetraether gdgt membrane lipids was recently introduced as a proxy for the fraction of fluvially derived organic carbon oc buried in marine sediments we investigate the source and distribution of terrestrial oc in marine sediments in a large spatial data set that encompasses the washington vancouver island margin vancouver island fjords and puget sound with the goal of comparing the bit index to other traditional measures of terrestrial oc d13 co f oc d13corg and lignin phenols d13corg values and lignin concentrations indicate that the fjords are a significant trap for undegraded wood derived terrestrial material with surface sediments containing up to 76 terrestrial oc these proxies also show significant terrestrial oc contributions to margin sediments up to 54 with most likely an angiosperm source from the columbia river in contrast to d13corg values and lignin concentrations bit index values indicate extremely low terrestrial carbon throughout the study area bit index values range from 0 to 0 28 and are uncorrelated with the other proxies though the bit index did not correlate with other proxies margin gdgt concentrations varied offshore similarly to other terrestrially derived oc and are well correlated with other proxies we suggest that the bit index is best interpreted as a proxy for soil or peat derived oc the majority of terrestrially derived oc delivered to sediment in this area has a lignin rich nonsoil source the disparity between the bit index and other proxies implies that the bit index significantly underestimates terrestrial relative to marine oc input to sediments in areas in which riverine oc input is not soil or peat derived burial of organic carbon oc on continental margins is estimated to account for the majority of the total carbon burial in the ocean and is a significant sink for terrestrial oc hedges and keil 1995 understanding the sources and fate of this terrestrial oc in marine sediments is thus of importance in understanding global biogeochemical cycles in this study we use two traditional proxies for terrestrial oc input to sediments the d 13 c of bulk sedimentary oc d13corg and the concentration of lignin phenols to examine the sources and quantity of terrestrial oc in sediments throughout the washington vancouver island margin vancouver island fjords and puget sound we compare these results to those obtained using a recently introduced proxy for terrestrial oc in marine sediments the branched and isoprenoid tetraether bit index

modeling the three dimensional structure of macroscopic magma transport systems application to kilauea volcano hawaii we report the results of modeling the three dimensional internal structure of kilauea s magmatic passageways the approach uses a clear plexiglass model containing equally spaced levels upon which well located seismic hypocenters are plotted application of constraining geologic and geophysical criteria to this distributed volume of earthquakes permits the interpretation of seismic structures produced by fracturing in response to locally high fluid pressures four magma transport and storage structures have been identified within and beneath kilauea 1 primary conduit the conduit transporting magma into kilauea s summit storage reservoir rises from the model base 14 6 km to the 6 5 km depth level it is a zone of intense fracturing and inferred intrusion whose horizontal sections are elliptical in planform over its height the average major axis of the component horizontal sections is 3 3 km with an average minor axis of 1 7 km this yields an aspect ratio of 0 52 at the 14 6 km level the strike of the major axis is n67 e during passage from the upper mantle through the oceanic crust this axis rotates in a right handed sense until the strike is n41 w at the 6 5 km level 2 magma chamber complex floor the interval from 6 5 to 5 7 km immediately over the primary conduit is aseismic this suggests differentially high fluid to rock ratios and relatively weak pathways for further vertical transport into higher levels of the storage complex as well as lateral leakage eastward into the mauna ulu staging area for later vertical ascent beneath the upper east rift zone seismicity within the immediately subjacent rocks that form the top of the primary conduit at 6 5 km suggests that this inferred magma rich horizon forms the effective floor of the summit storage complex 3 magma chamber crown intense seismicity over the 1 1 1 9 km depth interval defines an elliptical region in plan view the top of this region has a broad apex with an average major axis of 1 5 km and an average minor axis of 1 1 km producing an aspect ratio of 0 73 this region coincides with the epicentral position of summit vertical displacement maxima during inflationary deformation and is interpreted as a region of intense diking crowning the summit storage complex 4 upper east rift zone pipe from a depth of 5 7 km a cylindrical region of seismicity rises beneath the upper east rift zone to the 1 9 km level where it merges with the subhorizontal upper east rift zone duct this pipe like zone has a mean diameter of 1 4 km and a vertical axis that pierces the surface of the volcano at the intersection of the koae fracture system and the upper east rift zone we suggest this pipe forms a principal connection between the base of the summit storage reservoir and near surface storage compartments and ducts in the upper east rift zone in this role the pipe is suggested to have contributed heavily to mauna ulu s magma supply during 1969 1974 the model of magma transport and storage thus constructed provides a context in which other types of data e g ground deformation and electrical conductivity may be interpreted as well as a means of refining petrological inferences based on lava chemistry

long term modelling of landslides for different forest management practices long term effects of different forest management practices on landslide initiation and volume were analysed using a physically based slope stability model the watershed based model calculates the effects of multiple harvesting entries on slope stability by accounting for the cumulative impacts of a prior vegetation removal on a more recent removal related to vegetation root strength and tree surcharge four sequential clearcuts and partial cuts with variable rotation lengths were simulated with or without leave areas and with or without understorey vegetation in a subwatershed of carnation creek vancouver island british columbia the combined in nite slope and distributed hydrologic models used to calculate safety factor revealed that most of the simulated landslides were clustered within a 5 to 17 year period after initial harvesting in cases where suf cient time c 50 years lapsed prior to the next harvesting cycle partial cutting produced fewer landslides and reduced landslide volume by 1 4 to 1 6 fold compared to clearcutting approximately the same total landslide volume was produced when 100 per cent of the site was initially clearcut compared to harvesting 20 per cent of the area in successive 10 year intervals a similar nding was obtained for partial cutting vegetation leave areas were effective in reducing landsliding by 2 to 3 fold retaining vigorous understorey vegetation also reduced landslide volume by 3 8 to 4 8 fold the combined management strategies of partial cutting increasing rotation length provision of leave areas and retention of viable understorey vegetation offer the best alternative for minimizing landslide occurrence in managed forests copyright 2003 john wiley sons ltd

quantification of controls on regional rockfall activity and talus deposition kananaskis canadian rockies abstract rockfall is a significant geomorphic process in many mountainous regions that also poses a notable natural hazard risk most previous studies of rockfall erosion have investigated the mechanics and rates of local rockwall retreat and talus deposition with only a few investigations of rockfall and or associated talus considering larger spatial scales i e drainage basin mountain range the purpose of the current research is to investigate the areal extent of rockfall talus and controlling factors of its distribution over regional spatial scales of order 102 km2 in kananaskis canadian rockies to inform our understanding of its significance in mountain development to achieve this goal a large talus inventory is collected and analyzed for 11 steep tributaries of the kananaskis river canadian rockies talus accumulations associated with rockfall provide evidence about the nature and rates of rockfall activity that supplies sediment to these deposits and are the focus of the present study to quantify the controls of rockfall talus activity in this region we analyze the association of talus deposits with structural geology glacial topography and temperature related weathering i e frost cracking a total of 324 talus polygons covering a surface area of 28 51 km2 are delineated within the 11 study basins with the number of talus polygons in each study basin ranging from 1 to 73 analysis of the talus inventory shows that cirques and glacially sculpted valleys are locations of notable talus accumulation in kananaskis with other locations of significant talus deposition being associated with thrust faults we also found that the upper elevations at which talus deposits are typically found are the general range of elevations experiencing a notable number of days in the frost cracking window when this window is defined as 3 to 15 c no such association is found for the frost cracking window of 3 to 8 c estimates of average erosion rates for all study basins combined are between 0 15 mm y 1 lower estimate to 3 1 mm y 1 upper estimate rockfall activity is expected to have been most active for the several millennia following deglaciation during the paraglacial period when hillslopes were oversteepened

magma mixing recharge and eruption histories recorded in plagioclase phenocrysts from el chichon volcano mexico operative throughout the 200 ky history of the el chichon magma consistent core to rim decreases of sr sr ratios and coincident system increases in sr concentrations in plagioclase phenocrysts of varying size 1 cm to 2 mm are reported from samples of the 1982 and pre 1982 200 ka eruptions of el chichon volcano maximum sr sr ratios of 0 7054 significantly higher than the wholerock isotopic ratios 0 7040 0 7045 are found in the cores

a gis based automated procedure for landslide susceptibility mapping by the conditional analysis method the baganza valley case study italian northern apennines among the many gis based multivariate statistical methods for landslide susceptibility zonation the so called conditional analysis method holds a special place for its conceptual simplicity in fact in this method landslide susceptibility is simply expressed as landslide density in correspondence with different combinations of instability factor classes to overcome the operational complexity connected to the long tedious and error prone sequence of commands required by the procedure a shell script mainly based on the grass gis was created the script starting from a landslide inventory map and a number of factor maps automatically carries out the whole procedure resulting in the construction of a map with five landslide susceptibility classes a validation procedure allows to assess the reliability of the resulting model while the simple mean deviation of the density values in the factor class combinations helps to evaluate the goodness of landslide density distribution the procedure was applied to a relatively small basin 167 km2 in the italian northern apennines considering three landslide types namely rotational slides flows and complex landslides for a total of 1 137 landslides and five factors namely lithology slope angle and aspect elevation and slope bedding relations the analysis of the resulting 31 different models obtained combining the five factors confirms the role of lithology slope angle and slope bedding relations in influencing slope stability

the effect of pressure on dsr plag melt and dcr opx melt implications for anorthosite petrogenesis the crystal liquid partition coefficients for sr and cr dsr and dcr have been determined from electron microprobe analyses of plagioclase liquid and orthopyroxene liquid pairs produced in melting experiments run at pressures from 1 bar to 27 kbar on two compositions relevant to anorthosite petrogenesis one is a primitive jotunite hypersthene monzodiorite tj the other is a sample of an anorthositic dyke 500b results indicate that dsr plag liq remains nearly constant with increasing pressure tj 1 7 to 2 6 500b 0 9 to 1 4 this modest variation apparently results from the combined and opposing effects of crystal chemistry and pressure dsr increases with the albite content of plagioclase which itself increases with pressure along a composition s liquidus so pressure must have an intrinsic negative effect the two models for dsr j blundy b wood geochim cosmochim acta 55 1991 193 209 i bindeman a davis m drake geochim cosmochim acta 62 1998 1175 1193 that take into account the strong correlation between dsr and plagioclase composition overestimate dsr at high pressure whereas the two models that ignore plagioclase composition s morse geochim cosmochim acta 56 1992 1735 1738 r nielsen comput geosci 18 1992 773 788 underestimate it moreover since none of these models takes into account any pressure effect the discrepancies between predicted and observed dsr increase with pressure for all models the new results also show that dcr opx liq increases significantly with pressure dcr 2 at 1 atm and 14 2 at 10 kbar these new data confirm earlier less precise determinations of dcr that were used to infer a high pressure origin for al and cr rich orthopyroxene megacrysts the calculated sr and cr concentrations of liquids in equilibrium at 10 kbar with plagioclase and orthopyroxene megacrysts from anorthosite massifs sr 370 to 610 ppm and cr 20 to 130 ppm are in the range of what is observed in high al gabbros and primitive jotunites the inferred parent magmas of massive anorthosites fl 2000 published by elsevier science b v all rights reserved

mineral chemistry of mildly alkalic basalts from the 25 ma mont crozier section kerguelen archipelago constraints on phenocryst crystallization environments phenocryst compositions and mineral melt equilibria in the mildly alkalic basalts from the 25 ma mont crozier section on the kerguelen archipelago are used to estimate the depths at which magmas stalled and crystallized and to constrain the rule of crustal structure in the evolution of magmas produced by the kerguelen mantle plume the crozier section of nearly 1000m height consists of variably porphyritic flows up to 21 vol phenocrysts dominated by plagioclase clinopyroxene olivine fe ti oxides feldspars show an extreme range of compositions from high ca plagioclase an to sanidine and variable textures that are related to extensive fractionation degassing and mixing in relatively low pressure sub volcanic magma chambers although clinopyroxene is a minor phenocryst type 0 3 vol its non quadrilateral components principally al 1 9 8 6 wt al o vary widely the results of clinopyroxene liquid thermobarometry and clinopyroxene structural barometry indicate that the crozier magmas crystallized at pressures ranging from 1 kbar to 11 12 kbar with high al clinopyroxene recording the highest pressures of crystallization high al clinopyroxene rich cumulates may represent an important component of the seismic crust to mantle transition zone at 14 16 km depth high pressure high al clinopyroxene crystallization became important in the mildly alkalic basaltic magmas from the kerguelen archipelago as ascending magmas stalled and fractionated at or near the crust mantle interface which became deeper as a result of progressive crustal thickening as the archipelago moved from a ridge centered setting at 40 ma to an intraplate position by 25 ma

inventory fluxes and residence times from the depth profiles of naturally occurring 210pb in marine sediments of mumbai harbor bay measurements of the vertical concentration profile of deposited 210pb and its parent 226ra in cores of recent marine sediment of mumbai harbor bay mhb were made to determine the various depth distribution parameters sedimentation rate age of sediment total inventory fluxes residence times scavenging rate linear attenuation coefficient and relaxation mass depth overall the profile distributions of 226ra and 210pb showed a decreasing trend with increasing the depth the mean of sedimentation rate in the studied area was obtained to be about 0 76 cm year 1 which corresponds to average age of sediment of about 56 years the average total deposited 210pb for the studied sediment profile was 9 68 k bq m 2 and correspondingly the average value of fluxes of total 210pb and excess 210pb atmospheric flux were 0 59 and 0 32 k bq m 2 year 1 respectively the residence time of 210pb was in the range of 26 226 years throughout the sediment profile and showed generally an increasing trend from top to bottom the mean relaxation mass depth h0 derived from the depth profile of 210pb at the studied area was about 190 kg m 2 the negative association between clay content of cores and the h0 of 210pb indicates that as the clay content increases the penetration depth of deposited 210pb in sediment profile decreases

the impacts of logging on landslide activity at clayoquot sound british columbia abstract the objective of this study was to investigate the impacts of logging on landslide activity in clayoquot sound on the west coast of vancouver island british columbia a total of 1004 landslides were documented in order to test the hypothesis that areas affected by logging activities show different density frequency and magnitude characteristics of landsliding than areas unaffected by logging the frequency of landslides in logged terrain was found to be nine times higher than in undisturbed forest an exponential increase in landslide frequency within the area logged was observed on a large watershed scale failures in logged terrain occur on gentler slopes than in natural terrain partly because fewer slopes steeper than 40 have been logged debris slides and debris flows are the most frequently occurring mass movements initiating mostly from road fill failures and from within cutblocks most landslides initiated on se facing slopes with the highest landslide frequency near the coast and diminishing exponentially further inland this pattern of activity most likely reflects the greater impact of severe storms arriving from the pacific with winds dominating from the southeast concave and straight slopes are most susceptible to landslide initiation a preliminary examination of geologic control on the frequency of landslides suggests that the quatsino formation the island plutonic suite and the sicker group are significantly above the average rate further work is needed to identify and quantify factors confounding the trends and correlations identified in this overview study results obtained in this study will be used to implement changes in forest management

kilometer scale chemical reaction boundary patterns and deformation in sedimentary rocks abstract we use three dimensional 3d seismic data to image patterns developed by kilometer scale chemical reaction boundaries to demonstrate that chemical patterns are scaleable phenomena the patterns develop in biosiliceous marine successions due to the dissolution of opal a biogenic silica and reprecipitation as opal ct crystobalite and tridymite during burial the reaction boundary patterns comprise roughly circular regions where the reaction boundary has preferentially advanced these regions are up to 2 7 km wide and c 50 200 m in height and are termed cells the cells form by amalgamation with adjacent juvenile cells they also form by the incorporation of much smaller regions surrounding the cells where the chemical change has already occurred that we term satellites 50 m wide the reaction results in enhanced rates of sediment compaction hence differential advancement of reaction boundaries causes differential subsidence of the overburden inducing folding and faulting of the overburden above the cellular promontories we propose three potential mechanisms for the development of kilometer scale reaction boundary patterns a mass transport of silica by advection b perturbation of isotherms as a result of convective or conductive heat transport or c establishment of a positive feedback loop between fluid production due to the reaction hydraulic fracturing and the upward and lateral transport of fluids this study provides the first insights into how strongly patterned diagenetic reaction boundaries evolve at a basin scale an initial conceptualization of the potential range of reaction boundary morphologies that could exist in this diagenetic system and the likely mechanisms that could control them furthermore it demonstrates that the discipline of seismic diagenesis could represent a completely new approach for the study of chemical diagenetic processes in sedimentary rocks

geologic and physiographic controls on bed material yield transport and channel morphology for alluvial and bedrock rivers western oregon the rivers of western oregon have diverse forms and characteristics with channel substrates ranging from continuous alluvial gravel to bare bedrock analysis of several measurable morphologic attributes of 24 valley reaches on 17 rivers provides a basis for comparing nonalluvial and alluvial channels key differences are that alluvial reaches have greater bar area greater migration rates and show systematic correlation among variables relating grain size to bed material transport capacity we relate these differences between channel types to bed material transport rates as derived from a coupled regional analysis of empirical sediment yield measurements and physical experiments of clast attrition during transport this sediment supply analysis shows that overall bed material transport rates for western oregon are chiefly controlled by 1 lithology and basin slope which are the key factors for bed material supply into the stream network and 2 lithologic control of bed material attrition from in transport abrasion and disintegration this bed material comminution strongly affects bed material transport in the study area reducing transport rates by 50 90 along the length of the larger rivers in the study area a comparison of the bed material transport estimates with the morphologic analyses shows that alluvial gravel bed channels have systematic and bounding relations between bed material transport rate and attributes such as bar area and local transport capacity by contrast few such relations are evident for nonalluvial rivers with bedrock or mixed bed substrates which are apparently more influenced by local controls on channel geometry and sediment supply at the scale of western oregon the physiographic and lithologic controls on the balance between bed material supply and transport capacity exert far reaching influence on the distribution of alluvial and nonalluvial channels and their consequently distinctive morphologies and behaviors differences germane for understanding river response to tectonics and environmental perturbations as well as for implementing effective restoration and monitoring strategies

discriminating between onlap and lithologic interfingering in seismic models of outcrops seismic models of outcrops have shown that near the limits of resolution the seismic reflection tool records rapid facies changes as false lap outs we examined one such outcrop the triassic platform flank of picco di vallandro durrenstein in northern italy to develop criteria for recognizing false lap out patterns using measured sections photo mosaics of the continuous outcrop and petrophysical measurements on samples two contrasting impedance models were constructed one model supported by field observation shows interfingering between basin marls and slope carbonates the second model shows onlap of basin marls against slope carbonates but with similar overall geometries to the first model vertical incidence seismic models were produced at frequencies between 50 and 150 hz and with displays of seismic amplitude as well as two seismic attributes instantaneous phase and reflection strength at 50 hz the two lithologic models are seismically indistinguishable both showing onlap of basin units onto the slope at 90 hz displays of instantaneous phase begin to reveal the stratigraphic interfingering whereas seismic amplitude displays require frequencies of 150 hz to do so reflection strength accurately portrays the distribution of the two major facies in the entire range of examined frequencies but does not show sufficient detail to reveal interfingering vs onlap the same trends were visible with finite difference modeling of the full waveform here the differences between interfingering and onlap become visible at 150 hz in the phase model where seismic amplitude displays at this frequency are still ambiguous the phase model however fails to differentiate between slope dip and the basin sediment wedge whereas this wedge is clearly mapped by the reflection strength a combination of instantaneous phase and reflection strength provides a decisive advantage over conventional amplitude displays in recognizing rapid facies changes in seismic reflection data

on the value of seismic stratigraphy and seismic geomorphology comments on development patterns of an isolated oligo mesophotic carbonate buildup early miocene yadana field offshore myanmar by teillet et al 2020 abstract the paper by teillet et al 2020b constitutes a detailed sedimentological study of the upper part of the yadana carbonate platform offshore myanmar however the limited consideration and integration of the 3d seismic data results in a study lacking critical context with the authors concluding that the yadana platform developed under strict oligo mesophotic conditions and presents a layer cake architecture with laterally continuous lithofacies we suggest that the interpretations of teillet et al 2020b are not adequately supported because 1 lithostratigraphic principles are applied to correlate the main lithofacies from four wells using core data across a wide platform 10 20 km 2 the core data presented are restricted spatially as well as in depth and are not laterally and vertically representative of the entire platform hence these core data cannot be solely used to justify the lateral continuity of lithofacies and absence of euphotic depositional environments in the yadana platform 3 the study is not integrated within a comprehensive chronostratigraphic framework and sedimentological observations are not connected in a systematic way and 4 information extracted from the analysis of seismic facies and seismic geomorphology are ignored even though lateral variability is observable on seismic within the platform i e variability in depositional features and geometries seismic stratigraphy and seismic geomorphology should be considered because they allow the integration of any paleogeographic study into a comprehensive chronostratigraphic framework where 3d seismic data are available these comments aim at stimulating a discussion on the value of seismic stratigraphy and seismic geomorphology which should not be dismissed to better document the evolution of carbonate platforms through time and space and accurately assess controls on platform architecture and evolution

plagioclase residence times at two island arc volcanoes kameni islands santorini and soufriere st vincent determined by sr diffusion systematics the diffusive relaxation of trace element profiles in plagioclase phenocrysts may provide important constraints on magma residence times in crustal magma chambers initial trace element profiles in plagioclase phenocrysts are governed by variations in the concentration of a trace element in the melt and by the plagioclase melt partition coefficient trace element diffusion will subsequently act to modify this initial profile and given enough time produce a profile that is in equilibrium with the anorthite variations within the crystal we argue that the trace element partition coefficient da b between two parts a and b of a plagioclase crystal of variable anorthite content is equal to the ratio of their crystal liquid partition coefficients and that the equilibrium profile of the crystal can be calculated the time required to establish diffusive equilibrium is dependent on the wavelength and amplitude of the initial trace element concentration range and on the diffusivity of the trace element in plagioclase strontium plagioclase melt partition coefficients and diffusivities are calculated for a range of magmatic temperatures and plagioclase compositions a one dimensional diffusion model is developed that describes the diffusive destruction of oscillatory trace element zoning with time and allows the calculation of upper limits for plagioclase crystal residence times in a magma reservoir the model is tested using major and trace element concentrations measured along crystal traverses of plagioclase phenocrysts from the kameni island dacites santorini and from the 1979 soufriere andesite st vincent three out of eight plagioclase phenocrysts have sr concentration profiles that are not in diffusive equilibrium for these the diffusion model is employed to calculate maximum crystal residence times from incomplete diffusive equilibration of trace element zoning in plagioclase maximum crystal residence times range from 100 to 450 years this is in good agreement with estimates from crystal size distribution and from ra th disequilibrium studies for the kameni islands for soufriere however such short residence times are incompatible with u th mineral errorchron data that suggest residence times of 40 ka in a thermally buffered magma reservoir to reconcile these apparently different ages we invoke a more complicated magmatic history for soufriere where an initially buffered magma reservoir is disturbed by magma mixing and suffers limited additional crystal fractionation prior to eruption

historical change in lake sedimentation in lake takkobu kushiro mire northern japan over the last 300 years abstract environmental degradation including shallowing deterioration of aquatic habitat and water pollution has arisen from the inflow of fine sediment to lake takkobu in northern japan the lake has experienced gradual environmental degradation due to agricultural development which has introduced both fine sediment and sediment associated nutrients into the lake we have reconstructed the history of sediment yield to lake takkobu in kushiro mire over the last 300 years and have examined trends with reference to land use development fifteen lake sediment core samples were obtained and various physical variables of lake sediments were analyzed and dated using 137cs and tephrochronology the physical variables showed that all points contained mainly silt except for two points close to the river mouths where the mean diameter was

a honeycomb seafloor morphology in carbonate sediment of the carnegie ridge offshore ecuador formation and potential geodynamic significance based on swath bathymetry two dimensional high resolution seismic reflection profiles and ocean drilling program deep sea drilling project odp dsdp data we describe a seafloor honeycomb pattern and propose a model for its formation in pliocene miocene carbonate deposited on the uneven oceanic basement of the carnegie ridge offshore ecuador hydrothermal fluids derived from the basement aquifer fractured and dissolved carbonate sediment creating seafloor pits above basements highs fluids expelled along polygonal faults may have assisted the nucleation of seafloor depressions at the pliocene pleistocene boundary strong bottom currents scoured previously damaged sediments enlarging the initial depressions and producing the seafloor honeycomb pattern this regional erosive episode was contemporaneous with the final closing of the isthmus of panama and the clogging of the ecuador trench by the subduction of the carnegie ridge so that the honeycomb pattern may be viewed as a regional marker of these two geodynamic events

boundary layer crystallization in a basaltic magma chamber evidence from rishiri volcano northern japan the evolution of basaltic magma by mushy boundary layer processes introduction in a magma chamber is documented for an alkali basalt kutsugata the evolution of magma chambers is of major petrologic lava from rishiri volcano northern japan on the basis of zoning interest and has been studied extensively experimental patterns of plagioclase phenocrysts and their spatial distribution in and theoretical studies that have investigated the cooling the lava plagioclase phenocrysts with complex zoning patterns can of magma chambers have demonstrated that a magma be divided into four types type 1 is characterized by an extremely chamber solidifies through formation of a mushy boundan rich core an71 90 which is commonly corroded and filled with ary layer composed of crystals and interstitial melt along sodic plagioclase type 2 has an ab rich core surrounded by a calcic the chamber walls e g brandeis jaupart 1986 turner mantle characteristic of partial dissolution type 3 is characterized by et al 1986 marsh 1988 tait jaupart 1992 layered igneous complexes e g morse 1969 shirley 1987 an ab rich core that is commonly surrounded by a reversely zoned mcbirney 1996 provide useful information on how slightly calcic mantle type 4 has an ab rich core without a calcic mafic magma chambers evolve and consolidate but they mantle the an rich cores of the type 1 plagioclase are too calcic do not offer much insight into the instantaneous state of to have crystallized from a liquid represented by any whole rock a chamber because those intrusions integrate processes composition at the estimated temperatures of the kutsugata magma that occurred over long solidification times mcbirney system the an rich cores are inferred to have been formed in a noyes 1979 tait 1988 volcanic products such as mushy boundary layer along the wall of a magma chamber where lava flows and tephra deposits can sample the inthe magma was relatively cool and rich in water because of significant stantaneous state of a magma chamber there are a few olivine fractionation and possibly because of addition of water studies along this line of approach tait 1988 de silva expelled from the chilled margin and or groundwater from the 1989 nakada et al 1994 these studies focused on surrounding crust the ab rich cores of types 2 4 plagioclase crystal aggregates in volcanic products and concluded phenocrysts are interpreted to have crystallized in the main magma that the crystal formation in a mushy boundary layer body of the reservoir the types 2 and 3 ab rich cores were brought plays a dominant role in magmatic evolution in a magma to the mushy layer by convection the temporal and spatial variations reservoir however these studies were mostly on silicic of zoning patterns of plagioclase phenocrysts in basaltic lava flows magmas and there are significant differences in physical give useful information on the evolution of mafic magma chambers and chemical features between silicic and mafic magma chambers in this paper the magmatic evolution of an alkali basalt kutsugata lava from rishiri volcano northern japan is studied the kutsugata lava is divided into three lava flows on the basis of whole rock chemical

autopsy of a reservoir facies architecture in a multidam system elwha river washington usa the 2011 2014 removal of two large dams on the elwha river washington state the largest dam removal yet completed globally created extensive cutbank exposures of reservoir sediments allowing the first characterization of the facies architecture of sediments through direct observation in reservoirs worldwide and providing an unparalleled opportunity to assess the relationship between environmental influences such as changes in sediment supply and their expression in the stratigraphic record using a combination of facies description from observation of 49 measured sections and 100 exposures and analysis of digital elevation models and historic aerial photographs we delineated the characteristic depositional zones of each reservoir and mapped the evolution of the subaerial delta over the life span of the reservoir former lake mills the younger upstream reservoir was characterized by a tripartite subaerial gilbert style delta that prograded 1 km into the main reservoir from 1927 to 2011 sediments were composed of coarse grained topset beds steeply dipping foreset beds and a fine grained gently dipping prodelta while individual event horizons were discernible in fine grained sediments of former lake mills their number and spacing did not correspond to known drawdown or flood events former lake aldwell impounded from 1913 to 2011 was initially defined by the rapid progradation of a gilbert style subaerial delta prior to the upstream completion of glines canyon dam however the 1927 closure of glines canyon dam upstream caused the delta to evolve to a fine grained mouth bar type delta indicative of low finer grained sediment this evolution combined with a previously unrecognized landslide deposit into the upper delta plain suggests that understanding the exogenic influences on reservoir sedimentation is critical to interpretation and prediction of the sedimentation within individual systems

crustal forensics in arc magmas abstract the geochemical characteristics of continental crust are present in nearly all arc magmas these characteristics may reflect a specific source process such as fluid fluxing common to both arc magmas and the continental crust and or may reflect the incorporation of continental crust into arc magmas either at source via subducted sediment or via contamination during differentiation resolving the relative mass contributions of juvenile mantle derived material versus that derived from pre existing crust of the upper plate and providing these estimates on an element by element basis is important because 1 we want to constrain crustal growth rates 2 we want to quantitatively track element cycling at convergent margins and 3 we want to determine the origin of economically important elements and compounds traditional geochemical approaches for determining the contributions of various components to arc magmas are particularly successful when applied on a comparative basis studies of suites from multiple magmatic systems along arcs for which differentiation effects can be individually constrained can be used to extrapolate to potential source compositions in the lesser antilles arc for example differentiation trends from individual volcanoes are consistent with open system evolution however such trends do not project back to a common primitive magma composition suggesting that differentiation modifies magmas that were derived from distinct mantle sources we propose that such approaches should now be complemented by petrographically constrained mineral scale isotope and trace element analysis to unravel the contributing components to arc magmas this innovative approach can 1 better constrain true end member compositions by returning wider ranges in geochemical compositions among constituent minerals than is found in whole rocks 2 better determine magmatic evolution processes from core rim isotopic or trace element profiles from the phases contained in magmas and 3 constrain rates of differentiation by applying diffusion controlled timescales to element profiles an example from nguaruhoe volcano new zealand underscores the importance of such a microsampling approach showing that mineral isotopic compositions encompass wide ranges that whole rock isotopic compositions are consequently simply element weighted averages of the heterogeneous crystal cargo and that open system evolution is proved by core rim variations in sr isotope ratios nguaruhoe is just one of many systems examined through microanalytical approaches the overwhelming conclusion of these studies is that crystal cargoes are not truly phenocrystic but are inherited from various sources the implication of this realization is that the interpretation of whole rock isotopic data including the currently popular u series needs careful evaluation in the context of petrographic observations

geological significance of seismic reflections and imaging of the reservoir architecture in the malampaya gas field philippines the integration of petrographic analyses of cores and thin sections petrophysical measurements and well logs demonstrates that variations in acoustic impedance in the malampaya buildup upper eocene to lower miocene offshore northwest palawan are related to vertical changes in porosity and pore type which are dominantly controlled by diagenetic processes the nido limestone was subdivided into 10 50 m 30 150 ft thick units characterized by specific diagenetic patterns and petrophysical properties diagenetic units the alternation between tight and porous diagenetic units is mainly controlled by meteoric diagenesis leaching and pedogenesis and by late burial cementation and leaching well to seismic ties show that the main seismic reflectors within the buildup interior reflect the boundaries between diagenetic units most of the negative amplitude reflectors are related to unconformities whereas positive amplitude reflectors have a more questionable chronostratigraphic value and may represent the bases of cemented lenses that can crosscut time lines comparison with other southeast asian tertiary buildups indicates different origins of seismic reflections related to distinct patterns of diagenetic evolution the identification of such seismodiagenetic units and of their controlling factors is of paramount importance for the architecture and the petrophysical characterization of carbonate reservoirs

book reviewmoraines and varves origin genesis classification ch schluchter editor a a balkema rotterdam 1979 441 pp dfl 85 00 u s 45 00

landslide inventory in a rugged forested watershed a comparison between air photo and field survey data abstract landslide inventories are routinely compiled by means of aerial photo interpretation api when examining photo pairs the forest canopy notably in old growth forest hides a population of not visible landslides in the present study we attempt to estimate how important is the contribution of landslides not detectable from aerial photographs to the global mass of sediment production from mass failures on forested terrain of the capilano basin coastal british columbia api was coupled with intensive fieldwork for identification and measurement of all landslides a 30 year framework was adopted we show that not visible landslides can represent up to 85 of the total number of failures and account for 30 of the volume of debris mobilised such percentages display high sub basin variability with rates of sediment production varying by one order of magnitude between two sub basins of the study area this is explained qualitatively by gis based analysis of slope frequency distributions drainage density and spatial distribution of surficial materials such observations find further support in the definitions of transport limited and supply limited basins as a practical consideration to land managers we envisage that supplementary fieldwork for landslide identification is mandatory in transport limited systems only fieldwork has demonstrated that gully related failures have a greater importance than one could expect from api

estimating accumulation rates and physical properties of sediment behind a dam englebright lake yuba river northern california 1 studies of reservoir sedimentation are vital to understanding scientific and management issues related to watershed sediment budgets depositional processes reservoir operations and dam decommissioning here we quantify the mass organic content and grain size distribution of a reservoir deposit in northern california by two methods of extrapolating measurements of sediment physical properties from cores to the entire volume of impounded material englebright dam completed in 1940 is located on the yuba river in the sierra nevada foothills a research program is underway to assess the feasibility of introducing wild anadromous fish species to the river upstream of the dam possible management scenarios include removing or lowering the dam which could cause downstream transport of stored sediment in 2001 the volume of sediments deposited behind englebright dam occupied 25 5 of the original reservoir capacity the physical properties of this deposit were calculated using data from a coring campaign that sampled the entire reservoir sediment thickness 6 32 m at six locations in the downstream 3 4 of the reservoir as a result the sediment in the downstream part of the reservoir is well characterized but in the coarse upstream part of the reservoir only surficial sediments were sampled so calculations there are more uncertain extrapolation from one dimensional vertical sections of sediment sampled in cores to entire three dimensional volumes of the reservoir deposit is accomplished via two methods using assumptions of variable and constant layer thickness overall the two extrapolation methods yield nearly identical estimates of the mass of the reservoir deposit of 26 106 metric tons t of material of which 64 7 68 5 is sand and gravel over the 61 year reservoir history this corresponds to a maximum basin wide sediment yield of 340 t km2 yr assuming no contribution from upstream parts of the watershed impounded by other dams the uncertainties and limitations of the estimates of overall sediment quantities are discussed implications for watershed management and future reservoir sedimentation studies are also presented

1500 years of lake sedimentation due to fire earthquakes floods and land clearance in the oregon coast range geomorphic sensitivity to floods during timber harvest period

landslides affecting sedimentary characteristics of reservoir basin typhoons aere 2004 and matsa 2005 caused high nephelometric turbidity in the shihmen reservoir in northern taiwan jeopardizing the operation of the reservoir for several days and ultimately impacting the living conditions and economy of the downstream residents the torrential rains caused landslides and debris flows in upland areas and flowed into riverbeds likely contributing significantly to the suspended sediment yields in the reservoir this investigation elucidates how upland landslides affect sediment attributes in the reservoir basin study methods including field observations spatial analysis in gis and aerial photo interpretation are adopted to trace the sediment sources and contributing factors to the landslide torrential rains induced landslides and debris flows upland causing river incisions and soil erosion in landslide areas lacking vegetation these factors together with the conditions of the engineered structures and geologic vulnerabilities of the area caused suspended sediment yield in the reservoir the high nephelometric turbidity could potentially reoccur with masses of landslide derived sediment remaining upland and in the riverbed

dynamics of a complex mass movement triggered by heavy rainfall a case study from nw turkey abstract following a period of heavy precipitation a large and complex mass movement namely the dagkoy landslide occurred in the west black sea region of turkey on may 21 1998 this paper describes the conditioning factors of the landslide and interprets the mass transport processes in terms of a movement scenario geology geomorphology and vegetation cover were considered as the conditioning factors of the failure observations showed that the gently sloping about 10 area is mostly covered by dense forest trees at the crown where the motion initiated significant intersection of the collapsed slope with dip of the local marls seems to have contributed to the formation and geometry of the landslide the distance from the crown down to the toe of the landslide measured more than 600 m with about 0 6 km 3 total earth material displaced the landslide has both a block sliding characteristics in the upper portions and a debris flow soil flow component around the margins of the sliding blocks in the middle parts and at the toe the proposed scenario for the landslide reveals that the movement was initiated near crown as a result of the excess water content in the marls at the end of 3 days of heavy rainfall the early perturbations transverse cracks ridges etc lasted for 6 7 h after which the central part of the zone started to move as a soil flow in which very large intact blocks were transported even though the movement was very rapid 1 2 m min there was no loss of life however the movement destroyed 38 houses one mosque and a considerable amount of farmland

assessment of landslide susceptibility for a landslide prone area north of yenice nw turkey by fuzzy approach regional landslide susceptibility assessments pose complex problems to solve these problems numerous approaches such as statistical analysis geotechnical engineering approach geomorphologic approach and fuzzy logic have been employed however all the available methods for regional landslide susceptibility assessments have some uncertainties due to a lack of knowledge and variability minimizing these uncertainties provides realistic approaches use of the fuzzy logic approach to produce a landslide susceptibility map of a landslide prone area in nw turkey is the main purpose of the present study for this purpose the study includes five main stages these being the preparation of a landslide inventory of the study area the application of factor analysis the extraction of fuzzy if then rules the use of a geographical information system and the control of the reliability of the resulting landslide susceptibility map slope angle slope aspect land use weathering depth water conditions and topographical elevation were considered as landslide conditioning factors for the study area a total of 23 if then rules was extracted from the field data employing these rules fuzzified index maps representing each parameter were obtained finally combining these maps the landslide susceptibility map of the area was prepared when compared with the landslide susceptibility map the landslides identified in the area were found to be located in the very high and high susceptibility zones as far as the performance of the fuzzy approach for processing is concerned the images appear to be quite satisfactory the zones determined on the map being zones of relative susceptibility

the middle triassic evolution of the bangong nujiang tethyan ocean evidence from analyses of oib type basalts and oib derived phonolites in northern tibet in this paper we present new major and trace element chemical data for the basalts and phonolites of the nare ocean island fragment naoi as well as zircon u pb age data and hf isotope compositions for the naoi phonolites in the middle segment of the bangong nujiang suture zone northern tibet our aim is to assess the genesis of these rocks and to reconstruct the middle triassic evolution of the bangong nujiang tethyan ocean bnto the naoi retains an ocean island type double layered structure comprising a basaltic basement and an oceanic sedimentary cover sequence conglomerate and limestone the latter accompanied by layers of erupted phonolite near the top of the sequence the basalts in the naoi are enriched in light rare earth elements and high field strength elements nb ta zr hf and ti and they exhibit chondrite normalized ree patterns and primitive mantle normalized trace element patterns similar to those of ocean island basalts taking into consideration their high dy yb sm yb and la sm ratios we conclude that the naoi basalts were derived from the partial melting of garnet peridotite in the mantle the naoi phonolites have lree enriched chondrite normalized ree patterns with negative eu anomalies eu eu 0 41 0 43 and primitive mantle normalized trace element patterns with enrichments in nb ta zr and hf and depletions in ba u sr p and ti given the high contents of nb 172 256 ppm ta 11 8 16 0 ppm zr 927 1117 ppm and hf 20 8 26 9 ppm and the very low contents of mgo 0 11 0 25 wt the very low mg values 5 10 and the near zero contents of cr 1 27 7 59 ppm ni 0 43 7 19 ppm and co 0 11 0 38 ppm and the small and homogeneously positive e hf t values 4 9 to 9 5 we infer that the naoi phonolites were formed by the fractional crystallization of an oib derived mafic parent magma the phonolites of the naoi contain zircons that yielded u pb ages of 239 and 242 ma indicating that the naoi formed during the middle triassic these data combined with data from modern ocean islands e g canary islands cape verde fernando de noronha tristan da cunha and gough in the atlantic ocean and society and austral cook in the pacific ocean lead us to infer that the bnto was open for a long time before the middle triassic and that the ocean had already developed into a mature ocean with a thick oceanic lithosphere by at least the middle triassic

the role of woody vegetation in stabilizing slopes in the cincinnati area ohio tree roots markedly stabilize colluvium on steep hillsides in the cincinnati area ohio according to detailed analysis of a landslide complex on the south side of rapid run creek a tributary of the ohio river the shear surface of the slide developed near the interface between bouldery silty clay colluvium and underlying calcareous ordovician shale and it broke woody roots that penetrated through the colluvium and into the underlying bedrock measurements of positions sizes and tensile strengths of the roots indicate that the average shear strength contributed by the roots was about 5 7 kn m 2 of the shear surface the average strength contributed by residual friction of the soil was about 0 7 kn m 2 the tree roots increased the factor of safety against sliding nine fold root strength allows forested colluvium mantled hillslopes in the cincinnati area to resist sliding at slope angles as high as 35 whereas similar slopes devoid of trees are subject to sliding at slope angles of 12 to 14 the contribution of tree roots to slope stability should be evaluated before removal of trees for development of hillsides

the dynamics of kerguelen plateau magma evolution new insights from major element trace element and sr isotope microanalysis of plagioclase hosted in elan bank basalts abstract the kerguelen plateau and broken ridge in the southern indian ocean together represent one of the most voluminous large igneous provinces lips ever emplaced on earth a scientific objective of ocean drilling program odp leg 183 was to constrain the post melting magma evolution of kerguelen plateau magmas in an effort to better understand this evolution isotopic and trace element analysis of individual plagioclase crystals hosted within two kerguelen plateau basalts recovered from elan bank were undertaken previous whole rock studies established that the two host basalts investigated in this study are samples of crustally contaminated lower group and relatively uncontaminated upper group basalt plagioclase phenocrysts from the uncontaminated basalt are dominantly normal zoned and exhibit a 87sr 86sri range of 0 704845 0 704985 which overlaps uncontaminated group whole rock values previously reported plagioclase crystals from the contaminated basalt are dominantly reverse zoned and exhibit a 87sr 86sri range of 0 705510 0 705735 which all lie within contaminated group whole rock values previously reported there are no systematic within crystal core to rim variations in 87sr 86sri from either group with the exception that contaminated group crystal rims have overall less radiogenic 87sr 86sri than other zones these observations indicate that crustal assimilation occurred before the formation of unit 10 plagioclase phenocrysts which is supported by parent magma trace element abundance data inverted using carefully calculated partition coefficients trace element diffusion modeling indicates that the upper group basalt unit 4 experienced a more vigorous eruptive flux than the lower group basalt unit 10 we suggest that plagioclase phenocrysts in both the upper and lower group basalts originated from the shallowest section of what was likely a complex magma chamber system we contend that the magmatic system contained regions of extensive plagioclase dominated crystal mush crustal assimilation was not a significant ongoing process in this portion of the elan bank magmatic system both basalts exhibit compelling evidence for remobilization and partial resorption of crystalline debris e g reverse zoned crystals glomerocrysts we suggest unit 4 and 10 magmas ascended different sections of the elan bank magma system where the unit 10 magmas ascended a section of the magma system that penetrated a stranded fragment of continental crust

effects of planetary thermal structure on the ascent and cooling of magma on venus magellan radar images of the surface of venus show a spatially broad distribution of volcanic features models of magmatic ascent processes to planetary surfaces indicate that the thermal structure of the interior significantly influences the rate of magmatic cooling and thus the amount of magma that can be transported to the surface before solidification in order to understand which aspects of planetary thermal structure have the greatest influence on the cooling of buoyantly ascending magma we have constructed magma cooling profiles for a plutonic ascent mechanism and evaluated the profiles for variations in the surface and mantle temperature surface temperature gradient and thermal gradient curvature results show that for a wide variety of thermal conditions smaller and slower magma bodies are capable of reaching the surface on venus compared to earth primarily due to the higher surface temperature of venus little to no effect on the cooling and transport of magma are found to result from elevated mantle temperatures elevation dependent surface temperature variations or details of the thermal gradient curvature the enhanced tendency of magma to reach the surface on venus may provide at least a partial explanation for the extensive spatial distribution of observed volcanism on the surface

the role of landslides in mountain range evolution abstract we review the role of landslides in current concepts of the topographic development of mountain ranges we find that many studies in this field address basin or orogen scale competition between rock uplift and fluvial bedrock erosion hillslopes in general and bedrock landslides in particular are often assumed to respond rapidly to incision and development of the fluvial drainage network this leads to a one sided view of the geomorphic coupling between hillslopes and rivers that emphasizes the fluvial control of hillslopes but ignores the alternative view that landslides can affect the fluvial network there is growing evidence that landslides are a dominant source of sediment in mountain belts and that they exert a direct geomorphic control on fluvial processes landslides can influence the river network in a variety of ways from determining basin area and drainage divide positions to setting streamwise variations in sediment load and calibre the geomorphic legacy of large landslides on hillslope and channel morphologies may persist for up to 104 yr adding considerable variability to fluvial erosion and sedimentation patterns over these timescales we identify a number of questions for future research and conclude that a better understanding and quantification of the geomorphic feedbacks between landslides and river channels builds an important link between short term 105 yr landscape evolution models

pseudo unconformities in seismic models of large outcrops traditionally seismic modeling has concentrated on one dimensional borehole modeling and two dimensional forward modeling of basic structural stratigraphic schemes which are directly compared with real seismic data two dimensional seismic models based on outcrop observations may aid in bridging the gap between the detail of the outcrop and the low resolution of seismic lines examples include the dolomites north italy the vercors se france and the high atlas morocco the seismic models are generally constructed using the following procedure a construction of a detailed lithologic model based on direct outcrop observations b division of the lithologic model into lithostratigraphic units c assignment of petrophysical properties to these lithostratigraphic units d ray tracing to compute time or depth sections of reflectivity e convolution of the reflectivity sections with source wavelets of different frequencies the lithologic detail modeled in the case studies led to some striking results particularly the discovery of pseudo unconformities pseudo unconformities are unconformities in seismics but correspond to rapid changes of dip and facies in outcrop none of the outcrop geometries studied were correctly portrayed seismically at 25 hz peak frequency however in some instances the true relationship would gradually emerge at peak frequencies of 50 100 hz the examples given in this study demonstrate that detailed outcrop derived seismic models can reveal what stratigraphic relationships and features are likely to be resolved under ideal or less ideal conditions and what pitfalls may befall the interpreter of real seismic data

rapid reservoir erosion hyperconcentrated flow and downstream deposition triggered by breaching of 38 m tall condit dam white salmon river washington condit dam on the white salmon river washington a 38 m high dam impounding a large volume 1 8 million m3 of fine grained sediment 60 sand 35 silt and clay and 5 gravel was rapidly breached in october 2011 this unique dam decommissioning produced dramatic upstream and downstream geomorphic responses in the hours and weeks following breaching blasting a 5 m wide hole into the base of the dam resulted in rapid reservoir drawdown abruptly releasing 1 6 million m3 of reservoir water exposing reservoir sediment to erosion and triggering mass failures of the thickly accumulated reservoir sediment within 90 min of breaching the reservoir s water and 10 of its sediment had evacuated at a gauging station 2 3 km downstream flow increased briefly by 400 m3 s 1 during passage of the initial pulse of released reservoir water followed by a highly concentrated flow phase up to 32 sediment by volume as landslide generated slurries from the reservoir moved downstream this hyperconcentrated flow analogous to those following volcanic eruptions or large landslides draped the downstream river with predominantly fine sand during the ensuing weeks suspended sediment concentration declined and sand and gravel bed load derived from continued reservoir erosion aggraded the channel by 1 m at the gauging station after which the river incised back to near its initial elevation at this site within 15 weeks after breaching over 1 million m3 of suspended load is estimated to have passed the gauging station consistent with estimates that 60 of the reservoir s sediment had eroded this dam removal highlights the influence of interactions among reservoir erosion processes sediment composition and style of decommissioning on rate of reservoir erosion and consequent downstream behavior of released sediment

magma evolution revealed by anorthite rich plagioclase cumulate xenoliths from the ontong java plateau insights into lip magma dynamics and melt evolution abstract petrologic studies of igneous rocks often rely on whole rock analyses alone to deduce source and melting histories whole rock compositions represent a mixture of the processes responsible for the final texture and composition of the rock but do not emphasize the evolutionary processes that the rock may have experienced we examine the major minor and trace element compositions of plagioclase phenocrysts and plagioclase rich cumulate xenoliths from a sequence of kwaimbaita pillow basalt and massive flows recovered from ocean drilling program odp site 1183 on the expansive 122 ma ontong java plateau ojp and from subaerial outcrops on the island of malaita solomon islands these data are used to reconstruct equilibrium liquid compositions to understand magma dynamics magma evolution and the distribution basalt types across the ojp results reveal that crystals frequently are out of equilibrium with their host basalt two distinct compositional zones are present in plagioclase phenocrysts and xenolith crystals an80 86 and an65 79 equilibrium magma compositions derived from each of these zones are distinct in relative terms the following distinctions are made an80 86 sr y and eu richer ba and lree depleted higher sr ti lower ba sr and la y an65 79 sr y and eu poorer ba and lree enriched lower sr ti higher ba sr and la y we observed several an65 79 parent magmas with higher la y lower sr and higher lree than the majority of an65 79 zones which suggests that they grew from highly fractionated magmas the an80 86 zones of both xenolith crystals and phenocrysts appear to have crystallized relatively early and are attributed to growth in magmas more primitive than parent magmas of an65 79 zones or the host magma using melts modeling we demonstrate a significant role for h2o is not necessary to form an rich crystals from known ojp magma types these types of zones can instead form when relatively primitive ojp magmas ascend and partially crystallize at low pressures crystal mush layers are rheological elements of multiply saturated solidification fronts and conditions for extreme fractionation are met deep with thermally and mechanically insulated mush solidification fronts conditions in a homogenous magma body alone cannot generate the range of magma compositions and textures recorded in ojp plagioclase crystals we suggest that the ojp magma chamber system consisted of crystal mush dominated regions and liquid dominated regions in a laterally and vertically extensive system of interconnected dikes and sills solidification front disruption was common during magma recharge and transport which freed debris to mix with ojp magmas the volume of crystalline debris from disrupted solidification fronts was small relative to the overall magma volume which leads to little change of bulk magma chemistry this can explain the dominance of the kwaimbaita basalt type across the ojp evidence of solidification front disruption is best preserved as allochthonous crystals both more and less primitive than bulk magma chemistry both of which were observed in ojp basalts coincident with a zone of neutral buoyancy the shallow ojp magma chamber system existed at a depth of 0 7 km the ojp magma chamber system was thinner near the plateau margins which provided less density filtration of magmas this allowed more diverse magma types to reach the surface along the margins it is envisaged that as the ojp formed the zone of neutral buoyancy slowly migrated upward leading to slow yet pervasive assimilation of overlying seawater altered basalt at the base of the lava pile

influence of landslides on biophysical diversity a perspective from british columbia landslides have long been overlooked or underestimated as important natural disturbance agents in particular the ecological role of landslides in maintaining biological diversity has been largely ignored here we provide a western canadian british columbian perspective on the influences of landslides on biophysical diversity which is related in several ways to biological diversity we recognize several types of biophysical ecological diversity site diversity soil diversity and the derivative habitat or ecosystem including aquatic ecosystems diversity there are also a variety of landslide types depending on materials and on the rate and style of movement we discuss the roles of different landslide types on various aspects of terrestrial diversity landslides are simultaneously depositional and erosional processes that influence sites by redistributing materials and changing surface expression usually creating a complex microtopography that can include very dry ridges and hummocks and sometimes depressions with standing water landslide impacts to site also influence soil and soil development portions of landslides with exposed parent material are set back to the initial stages of soil development and ecological succession landslides can also change soil density structure porosity surface texture chemistry and microclimate by changing site and soil landslides also influence habitat landslides influence habitat diversity by engendering a mosaic of seral stages often both primary and secondary and in overwhelmingly forested landscapes often create nodes or hotspots of non forested habitat and biota in some areas like the boreal forest there is an important interplay between landslides and fire while on the coast of british columbia debris and snow avalanches can be the dominant disturbance agent low gradient and deep seated landslides are often opportunistically colonized by beaver and other water and shrub loving fauna sag ponds and impounded streams provide aquatic habitat often with standing dead trees landslide rubble and scarps provide denning nesting habitat escape terrain and cliff habitat for vertebrates

provenance of proterozoic garnet biotite gneiss recovered from elan bank kerguelen plateau southern indian ocean at elan bank of the kerguelen plateau in the southeast indian ocean leg 183 of the ocean drilling program recovered clasts of garnet biotite gneiss in a fluvial conglomerate intercalated with basalt flows u pb and pb pb dates of zircons and monazites in these clasts and an overlying sandstone range from 534 to 2547 ma which is much older than the surrounding indian ocean seafloor these dates show that old continental crust resides in the shallow crust of the oceanic kerguelen plateau and that the breakup of gondwana dispersed continental fragments into the nascent indian ocean lithosphere

hydrologic modeling of flood conveyance and impacts of historic overbank sedimentation on west fork black s fork uinta mountains northeastern utah usa abstract this study assesses historic overbank alluvial sedimentation along a low gradient reach of west fork black s fork in the northern uinta mountains utah in this previously glaciated setting an alluvial floodplain that is approximately 400 m wide by 1500 m long has been modified by the combined effects of valley morphometry and the recent history of clear cut logging during the late 19th and early 20th centuries to quantify the effects on sedimentation and flow conveyance three natural streambank exposures were sampled and analyzed for nuclear bomb fallout 137 cs the distribution of 137 cs within the three profiles suggests that a remnant outwash terrace exerts a first order control over the deposition of overbank alluvium upstream from a constriction in the floodplain caused by the terrace remnant as much as 40 cm of overbank alluvium has been deposited since the beginning of clear cut logging immediately downstream of that constriction no evidence exists for any overbank sedimentation during that same period vibracore samples and oakfield soil probe sampling throughout the study reach quantified the geographic extent and thicknesses of the historic alluvial package flood conveyance through the study area was modeled using the u s army corps of engineers hec ras modeling program model simulations were run for modern conditions using surveyed topography and for prehistoric conditions using the modern topography less the historic alluvial package determined by 137 cs analyses model results indicate that the floodplain constriction caused a significant impediment to flood conveyance at even modest discharges during prehistoric conditions this promoted ponding of floodwaters upstream of the constriction and deposition of alluvium this has increased bank heights upstream of the constriction to the point that under modern conditions 1 to 5 year recurrence interval floods are largely confined within the channel these results confirm the validity of this new approach of combining 137 cs dating of alluvial sediments with hec ras flow modeling to compare flood conveyance along a single stream reach prior to and since an abrupt change in alluvial sedimentation patterns

minor and trace element zoning in plagioclase implications for magma chamber processes at parinacota volcano northern chile textural and compositional zoning in plagioclase phenocrysts in a sample from parinacota volcano chile was investigated using backscattered electron images and electron microprobe analysis of major and trace elements large 2 mm oscillatory zoned crystals type i with resorption surfaces of moderate an discontinuities 10 an and decreasing trace element contents sr mg ti towards the rim reflect melt differentiation and turbulent convection in the main magma body early recharge with a low sr mafic magma is seen in the core small scale sr variations in the core indicate limited diffusion and thus residence and differentiation times of the magma shorter than a few thousand years smaller crystals type ii with low trace element an ratio reflect the influence of an h2o rich melt probably from a differentiated boundary layer closed system in situ crystallisation mafic magma recharge and the role of a water rich differentiated boundary layer can be distinguished from the an trace element relationships crystals apparently move relatively freely between different parts and regimes in the magma chamber evidence for convective crystal dispersion high sr type ii crystals indicate an earlier input of sr rich mafic magma recharge of two distinct mafic magma types is thus identified high sr and low sr which must have been present at increasing recharge rates with time in the plumbing system throughout the volcano s history