jokulhlaups a reassessment of floodwater flow through glaciers 1 in glaciated catchments glacier generated floods jokulhlaups put human activity at risk with large sporadic jokulhlaups accounting for most flood related fatalities and damage to infrastructure in studies of jokulhlaup hydrodynamics the view predominates that floodwater travels within a distinct conduit eroded into the underside of a glacier however some jokulhlaups produce subglacial responses wholly inconsistent with the conventional theory of drainage by focusing on icelandic jokulhlaups this article reassesses how floodwater flows through glaciers it is argued that two physically separable classes of jokulhlaup exist and that not all jokulhlaups are an upward extrapolation of processes inherent in events of lesser magnitude and smaller scale the hydraulic coupling of multiple nonlinear components to the flood circuit of a glacier can induce extreme responses including pressure impulses in subglacial drainage representing such complexity in mathematical form should be the basis for upcoming research as future modeling results may help to determine the glaciological processes behind heinrich events moreover such an approach would lead to more accurate predictive models of jokulhlaup timing and intensity

building an island arc crustal section time constraints from a la icp ms zircon study geochronological studies of samples from continuous crustal sections of fossil intra oceanic arcs are paramount for determining the precise timing of major processes that took place during the building of an oceanic island arc crust in this study laser ablation icp ms u pb zircon and conventional rb sr analyses pinpoint the timing of major events responsible for crustal growth of the kohistan paleo island arc northern pakistan inheritance in magmatic rocks is evidence for recycling of intra arc material and indicates that the kohistan arc may have formed as early as 135 4 ma one older inherited grain indicates that the arc developed on a young oceanic lithosphere whose remnants include a c 175 ma old component an interesting consequence is that intra oceanic arc magmas can yield inherited zircons which can be much older than the arc system itself without requiring recycling back into the mantle by subduction processes in the case of the kohistan arc ante arc neotethys oceanic lithosphere was tapped by arc magmas during their way upward into the arc crust the oldest magmatic ages measured in this study fall in the range 101 102 ma 100 9 0 6 and 102 1 0 4 ma this period corresponds to arc build up and thickening of the arc crust leucogranitic melts dated at 89 9 0 4 ma and 90 9 1 0 ma are considered as produced by dehydration melting reaction accompanying granulitisation of the thickened lower arc crust a maximum age for this event is 97 7 0 7 ma the age of emplacement of a garnet meta tonalite affected by granulite facies metamorphism magmatic activity was still ongoing during and after the granulitisation as testified by emplacement of a diorite and a gabbro dated at 89 1 0 6 and 88 2 0 9 ma respectively the upper part of the metaplutonic sequence contains diorite samples dated at 84 6 0 5 ma and 84 3 0 5 ma and as young as 81 1 0 7 ma during this period and based on the present day outcropping sequences the mean crustal growth rate varied from 32 to 65 km 3 km ma volume per unit width along the strike of the arc which is comparable to the range for present day arcs of the western pacific region the correspondence of crustal growth rates observed for present day island arcs and the good preservation of the crustal section in the kohistan arc make this area an exceptional natural laboratory to study arc related processes and to check models of continental crust formation by arc accretion

an assessment procedure for glacial hazards in the swiss alps glacial hazards such as ice avalanches glacial lake outburst floods and debris flows have caused severe damage in populated mountain regions such as the swiss alps assessment of such hazards mus

predictive uncertainty of peak outflow relations for landslides dam breach risk assessment development considering the failure of landslide dams often requires the estimation of peak outflow through the breach the empirical equations based on data from case studies tend to be the first direct approach this paper conducted an uncertainty analysis when these empirical relations were utilized to predict the peak outflow of a breached landslide dam the results suggest that the relations derived from manmade dams or embankments typically overestimate the peak outflow about 1 5 to 3 4 of an order of magnitude and the relations derived from the database of landslide dams have much smaller mean prediction errors and also exhibit broad uncertainty bands application of the uncertainly analysis was illustrated by the tangjiashan landslide dammed lake formed during 2008 wenchuan earthquake in addition the predicted results from eq 1 deduced herein were considered to be the reliable estimate of peak outflow through the breach of landslide dam

a review of catastrophic drainage of moraine dammed lakes in british columbia abstract moraine dammed lakes are common in the high mountains of british columbia most of these lakes formed when valley and cirque glaciers retreated from advanced positions achieved during the little ice age many moraine dams in british columbia are susceptible to failure because they are steep sided have relatively low width to height ratios comprise loose poorly sorted sediment and may contain ice cores or interstitial ice in addition the lakes commonly are bordered by steep slopes that are prone to snow and ice avalanches and rockfalls moraine dams generally fail by overtopping and incision the triggering event may be a heavy rainstorm or an avalanche or rockfall that generates waves that overtop the dam the dam can also be overtopped by an influx of water caused by sudden drainage of an upstream ice dammed lake jokulhlaup melting of moraine ice cores and piping are other possible failure mechanisms failures of moraine dams in british columbia produce destructive floods orders of magnitude larger than normal streamflows most outburst floods are characterized by an exponential increase in discharge followed by an abrupt drop to background levels when the water supply is exhausted peak discharges are controlled by dam characteristics the volume of water in the reservoir failure mechanisms and downstream topography and sediment availability for the same potential energy at the dam site floods from moraine dammed lakes have higher peak discharges than floods from glacier dammed lakes the floodwaters may mobilize large amounts of sediment as they travel down steep valleys producing highly mobile debris flows such flows have larger discharges and greater destructive impact than the floods from which they form moraine dam failures in british columbia and elsewhere are most frequent following extended periods of cool climate when large lateral and end moraines are built a period of protracted warming is required to trap lakes behind moraines and create conditions that lead to dam failure this sequence of events occurred only a few times during the holocene epoch most notably during the last several centuries glaciers built large moraines during the little ice age mainly during the 1700s and 1800s and lakes formed behind these moraines when climate warmed in the 1900s twentieth century climate warming is also responsible for recent moraine dam failures in mountains throughout the world warming from the late 1800s until about 1940 and again from 1965 to today destabilized moraine dams with interstitial or core ice the warming also forced glaciers to retreat prompting ice avalanches landslides and jokulhlaups that have destroyed some moraine dams

high temperature and pressure seismic properties of a lower crustal prograde shear zone from the kohistan arc pakistan anastomosing shear zones exposed in the lower crust of the kohistan palaeoisland arc in pakistan have parageneses indicating increasing pressure during deformation therefore they represent a rare example of strain localization during crustal thickening we investigated the seismic properties of a sheared gabbro with constant bulk chemistry across one of these shear zones the compressional wave velocity was measured at confining pressures of up to 0 5 gpa and temperatures of up to 600 8c the density the average vp compressional p wave velocity and the acoustic impedance at room temperature increase from the undeformed protolith through the strain gradient to the intensely sheared mylonite the seismic anisotropy is largest for the strain gradient the vp dependence of the velocities on temperature is much higher in the mylonite than in the protolith the acoustic impedance contrast between protolith and mylonite is high enough to generate seismic reflections at low temperatures but not at high temperatures this suggests that the seismic reflectivity may also depend on the temperature consequently ductile shear zones can be detected in reflection profiles of crusts with low geothermal gradients and may be transparent in crusts with high geothermal gradients

analysis of landslide dams induced by the 2008 wenchuan earthquake abstract landslide dams caused by earthquakes are extremely hazardous disruptions of the flow of water and sediment in mountain rivers capable of delivering large outburst floods that may devastate downstream areas we analyzed a unique inventory of 828 landslide dams triggered by the m w 7 9 2008 wenchuan tectonic earthquake china constituting 1 4 of the 60 000 coseismic slope failures mapped and attributed to this event while 501 landslides blocked the rivers completely the remainder caused only partial damming or channel diversion the spatial distribution of landslide dams follows the same trend of that of the total landslide distribution with landslide dams being most abundant in the steep watersheds of the hanging wall of the yingxiu beichuan thrust fault and in the northeastern part of the strike slip fault near qingchuan besides the co seismic landslide density the river width also played a key role in determining the landslide dam formation narrow rivers are more prone to be dammed than the wide rivers the correlation between river width and landslide dam volume follows a linear relation which can be used to roughly estimate the dam formation possibility however the applicability of this correlation needs to be validated in other regions the decay failure rate of dams defined here as the percentage of the number and area of landslide dams that have failed over time shows that 25 of dams accounting for 30 of total landslide dam area failed one week after the earthquake these percentages increased to 60 within 1 month and to 90 within 1 year the geomorphometric parameters were analyzed revealing power law relations between landslide area and dam width landslide source area and dam area as well as lake area and lake volume the inventory presented in this study will enrich the worldwide earthquake induced landslide dam database and will also contribute to a better understanding of the post earthquake dam decay

complex flow in lowest crustal anastomosing mylonites strain gradients in a kohistan gabbro northern pakistan 1 strain localization in near paleo moho metagabbros of the kohistan arc northern pakistan produced anastomosing shear zones the two dimensional 2 d analysis of strain gradients in planes parallel to the general flow direction reveals simple shear strain 7 combined with about 50 surface loss the pargasite garnet assemblage of the mylonite has a density 2 8 higher than the protolith which is insufficient to account for the measured surface loss furthermore major and trace element compositions of the gabbro and the mylonite indicate isochemical deformation average vp and acoustic impedance measured at room temperature and up to 300 mpa increase from gabbro through the gradient zone to mylonite they are consistent with density measurements the three dimensional analysis of shape preferred orientation and lattice preferred orientation of sheared and synkinematic minerals indicates that the 2 d surface loss reflects sideways and lengthwise material transfer sideways and lengthwise material transfers take place in widening and lengthening mylonites respectively the anastomosing shear zone pattern impels this complexity of the regional flow we conclude that shear zones with a thinning component are likely representative of deep crustal flow in other tectonic environments

experimental study to identify premonitory factors of landslide dam failures abstract identifying premonitory factors before final failure for long existing landslide dams is of high importance in disaster prevention and risk reduction in this study a series of large scale outdoor experiments were designed and conducted to identify premonitory factors that may be used in failure prediction for actual landslide dams surface deformation especially dam crest settlement dam seepage water turbidity and self potential across the dam crest were selected as the target parameters changes in these parameters showed apparent correlations between each other based on the monitoring data obtained and the observation performed during the tests the deformation and failure sequence of the dam model can be separated into four time sequential periods 1 emergence of seepage water and front wetting in this period the monitoring parameters did not show any obvious changes however wetting was observed in the downstream face 2 hyperconcentrated flow discharge in this period water flowed out of the drainage channel and the vertical deformation of the dam body became obvious while the turbidity of the seepage water increased 3 emergence and development of cracks on the dam crest in this period the dam crest settlement also increased 4 sudden collapse and final failure in this period self potential across the dam crest decreased rapidly and the dam crest settlement reached a peak value therefore dam crest settlement seepage water turbidity and self potential changes can be regarded as premonitory factors of landslide dam failure

earthquake induced chains of geologic hazards patterns mechanisms and impacts large earthquakes initiate chains of surface processes that last much longer than the brief moments of strong shaking most moderate and large magnitude earthquakes trigger landslides ranging from small failures in the soil cover to massive devastating rock avalanches some landslides dam rivers and impound lakes which can collapse days to centuries later and flood mountain valleys for hundreds of kilometers downstream landslide deposits on slopes can remobilize during heavy rainfall and evolve into debris flows cracks and fractures can form and widen on mountain crests and flanks promoting increased frequency of landslides that lasts for decades more gradual impacts involve the flushing of excess debris downstream by rivers which can generate bank erosion and floodplain accretion as well as channel avulsions that affect flooding frequency settlements ecosystems and infrastructure ultimately earthquake sequences and their geomorphic consequences alter mountain landscapes over both human and geologic time scales two recent events have attracted intense research into earthquake induced landslides and their consequences the magnitude m 7 6 chi chi taiwan earthquake of 1999 and the m 7 9 wenchuan china earthquake of 2008 using data and insights from these and several other earthquakes we analyze how such events initiate processes that change mountain landscapes highlight research gaps and suggest pathways toward a more complete understanding of the seismic effects on the earth s surface

remote sensing based assessment of hazards from glacier lake outbursts a case study in the swiss alps glacier lakes are a common phenomenon in high mountain areas outbursts from glacier lakes have repeatedly caused the loss of human lives as well as severe damage to local infrastructure in several high mountain ranges around the world a grave uncertainty about the hazard potential of glacier lakes still exists especially with respect to the effects of accelerating rates of glacier retreat as a consequence of atmospheric warming area wide detection and modeling of glacier lake hazard potentials is therefore a major challenge in this study an approach integrating three scale levels allows for the progressive focus on critical glacier lakes remote sensing methods for application in glacier lake hazard assessment are presented and include channel indexing data fusion and change detection each method matches the requirements of a certain scale level for estimating potential disaster amplitudes assessments must be made of maximum discharge and runout distance of outbursts floods and debris flows existing empirical relations are evaluated and complementary ones as derived from available data are proposed tests with observations from a recent outburst event from a moraine dammed lake in the swiss alps show the basic applicability of the proposed techniques and the usefulness of empirical relations for first hazard assessments in particular the observed runout distance of the debris flow resulting from the outburst does not exceed the empirically estimated maximum runout distance a list of decision criteria and related remote sensing techniques are discussed in conclusion such a list is an essential tool for evaluating the hazard potential of a lake a systematic application of remote sensing based methods for glacier lake hazard assessment is recommended

superposition of replacements in the mafic granulites of the jijal complex of the kohistan arc northern pakistan dehydration and rehydration within deep arc crust abstract a deep level crustal section of the cretaceous kohistan arc is exposed in the northern part of the jijal complex the occurrence of mafic to ultramafic granulite facies rocks exhibits the nature and metamorphic evolution of the lower crust mafic granulites are divided into two rock types two pyroxene granulite orthopyroxene clinopyroxene plagioclase quartz 1 and garnet clinopyroxene granulite garnet clinopyroxene plagioclase quartz 2 two pyroxene granulite occurs in the northeastern part of the jijal complex as a relict host rock of garnet clinopyroxene granulite where the orthopyroxene rich host is transected by elongated patches and bands of garnet clinopyroxene granulite garnet clinopyroxene granulite together with two pyroxene granulite has been partly replaced by amphibolite hornblende garnet plagioclase quartz 3 the garnet bearing assemblage 2 is expressed by a compression dehydration reaction hornblende orthopyroxene plagioclase garnet clinopyroxene quartz h 2 o subsequent amphibolitization to form the assemblage 3 is expressed by two hydration reactions garnet clinopyroxene plagioclase h 2 o hornblende quartz and plagioclase hornblende h 2 o zoisite chlorite quartz the mafic granulites include pod and lens shaped bodies of ultramafic granulites which consist of garnet hornblendite garnet hornblende clinopyroxene 4 associated with garnet clinopyroxenite garnetite and hornblendite field relation and comparisons in modal chemical compositions between the mafic and ultramafic granulites indicate that the ultramafic granulites were originally intrusive rocks which dissected the protoliths of the mafic granulites and then have been metamorphosed simultaneously with the formation of garnet clinopyroxene granulite the results combined with isotopic ages reported elsewhere give the following tectonic constraints 1 crustal thickening through the development of the kohistan arc and the subsequent kohistan asia collision caused the high pressure granulite facies metamorphism in the jijal complex 2 local amphibolitization of the mafic granulites occurred after the collision

analysis and dynamic modeling of a moraine failure and glacier lake outburst flood at ventisquero negro patagonian andes argentina summary although moraine dams are inherently prone to failure because of their often weak structure loose internal composition and lack of an engineered spillway the understanding of dam breaching processes remains largely incomplete and appropriate modeling approaches are scarce this paper analyzes a recent glacier lake outburst caused by the failure of the terminal moraine of ventisquero negro patagonian andes argentina in may 2009 the dam breach trigger breaching and lake emptying processes plus the dynamics of the outburst flood were reconstructed based on field evidence and the application of a dynamic dam break model results indicate that the moraine failure was caused most probably by a rising lake level due to heavy precipitation resulting in high lake outflow which led to dam erosion and finally to dam failure the lake volume of ca 10 106 m3 was released in ca 3 h producing high discharge ca 4100 m3 s 1 debris flows and hyperconcentrated flows as the escaping water entrained large volumes of clastic material the methodology presented in this paper provides valuable insights into complex dam breach and glof processes and closes a critical gap in dynamic dam break modeling aimed at providing the lake outburst hydrograph an accurate determination of outburst hydrographs constitutes one of the most crucial aspects for hazard assessment of unstable lakes and will gain further importance with ongoing glacier retreat and glacier lake formation

analyzing successive landslide dam formation by different triggering mechanisms the case of the tangjiawan landslide sichuan china abstract the catastrophic tangjiawan landslide triggered by the 2008 wenchuan earthquake blocked the duba river impounding one of the most dangerous coseismic barrier lakes in beichuan china the lake was drained by an artificial spillway within one month after the earthquake to minimize the potential dam breach flooding risk however on september 5 2016 this landslide was reactivated and dammed the river again creating a 20 m high dam at the same location and resulting in the formation of a barrier lake with a volume of 0 6 million m3 the day after the event we carried out a field investigation of the landslide and obtained a high resolution image and dem using uav the satellite images from 2005 2008 2010 and 2015 were also collected to analyze the evolution of the landslide together with multi temporal dems the geometry and volumes of the displaced mass and the landslide dams and barrier lakes were calculated using image interpretation and 3d spatial analysis with gis this landslide is of great scientific interest as it presents a good example of multiple reactivation of a pre historical giant landslide under different triggering conditions a reactivation of an older landslide during the wenchuan earthquake and a second reactivation during a rainfall event several years later meanwhile from the hazard assessment and prevention perspective it is also representative as it dammed the river twice in 2008 and 2016 posing threats to both upstream and downstream areas we infer that the successive landslides in this region could be caused by the strong tectonic activities including earthquakes and high average uplifting rate the results of landslide volume analysis using multi temporal dems contribute to the landslide mechanism analysis and suggest that the landslide volume estimation is effected by the landslide type landslide rupture surface location and resolution of dem we also compare the performance of different empirical models of landslide stability and dam breach flood parameters and discuss their application during the quick assessment of the potential hazard of the landslide dams generally the successive landslide dams at the tangjiawan site are caused by the successive landslide reactivations on an anti dip slope controlled by strong tectonic activity and river erosion involve with a mass of loose materials of previous landslide deposition and possess high flood risk to the downstream area the experience gained in this work can be used to assist the hazard assessment and the planning of the emergency measures for similar landslide dams in the future

the maximum discharge of outburst floods caused by the breaching of man made and natural dams the sudden release of water impounded in natural and man made reservoirs has been responsible for some major disasters in mountainous regions of the world recent natural damming events and failures of natural dams have illustrated the need to examine the nature and magnitude of outburst floods and the behaviour of debris dams in general an empirical relationship between maximum discharge qmax and volume of water released during the outburst event vmax is established qmax 0 72vmax0 53 for man made dams and the relationship is thought applicable to the breaching of natural debris dams landslides and moraines this relationship allows a first order estimate to be made of qmax in the vicinity of the breach for a given vmax during the failure of a man made dam or a natural debris dam key words outburst floods man made dams natural dams landslide dam failure

geomorphic and sedimentological signature of a two phase outburst ood from moraine dammed queen bess lake british columbia canada on 12 august 1997 the lower part of diadem glacier in the southern coast mountains of british columbia fell into queen bess lake and produced a train of large waves the waves overtopped the broad end moraine at the east end of the lake and ooded the valley of the west fork of nostetuko river the displacement waves also incised the out ow channel across the moraine stratigraphic and sedimentologic evidence supports the conclusion that the ood had two phases one related to wave overtopping and a second to breach formation empirical equations were used to calculate the peak discharge of the ood at various points along the west fork of the nostetuko valley and to describe the attenuation of the ood wave the velocity of the ood was also calculated to determine the time it took for the ood to reach the main fork of nostetuko river the highest peak discharges were achieved in the upper reach of the valley during the displacement phase of the ood peak discharge declined rapidly just below the moraine dam with little change thereafter for approximately 7 km empirical formulae and boulder measurements indicate a rise in peak discharge in the lower part of the west fork valley we suggest that ow in the upper part of the valley records the passage of two separate ood peaks and that the rise in discharge in the lower part of the valley is due to amalgamation of the wave and breach peaks hydraulic ponding in con ned reaches of the valley extended the duration of the ood in addition erosion of vegetation and sediment in the channel and valley sides may also have exerted an in uence on the duration and nature of ooding sediments were deposited both upstream and downstream of channel constrictions and on a large fan extending out into the trunk nostetuko river valley this study extends our understanding of the variety and complexity of outburst oods from naturally dammed lakes it also shows that simple empirical and other models for estimating peak discharges of outburst oods are likely to yield erroneous results copyright 2005 john wiley sons ltd

the 1786 earthquake triggered landslide dam and subsequent dam break flood on the dadu river southwestern china abstract chinese historic documents recorded that on june 1 1786 a strong m 7 75 earthquake occurred in the kangding luding area sichuan southwestern china resulting in a large landslide that fell into the dadu river as a result a landslide dam blocked the river ten days later the sudden breaching of the dam resulted in catastrophic downstream flooding historic records document over 100 000 deaths by the flood this may be the most disastrous event ever caused by landslide dam failures in the world although a lot of work has been carried out to determine the location magnitude and intensity of the 1786 earthquake relatively little is known about the occurrence and nature of the landslide dam in this paper the dam was reconstructed using historic documents and geomorphic evidence it was found that the landslide dam was about 70 m high and it created a lake with a water volume of about 50 106 m3 and an area of about 1 7 km2 the landslide dam breached suddenly due to a major aftershock on june 10 1786 the peak discharge at the dam breach was estimated using regression equations and a physically based predictive equation the possibility of a future failure of the landslide seems high particularly due to inherent seismic risk and detailed geotechnical investigations are strongly recommended for evaluating the current stability of the landslide

reconstructing historic glacial lake outburst floods through numerical modelling and geomorphological assessment extreme events in the himalaya westoby m j glasser n f hambrey m j brasington j reynolds j m hassan m a a m 2014 reconstructing historic glacial lake outburst floods through numerical modelling and geomorphological assessment extreme events in the himalaya earth surface processes and landforms 39 12 1675 1692

isotopic constraints on the evolution of metamorphic conditions in the jijal patan complex and the kamila belt of the kohistan arc pakistan himalaya

volume calculation and analysis of the changes in moraine dammed lakes in the north himalaya a case study of longbasaba lake glacial lake outburst flood hazards in the himalayan region have received considerable attention in recent years accurate volume estimation for glacial lakes is important for calculating outburst flood peak discharge and simulating flood evolution longbasaba lake a potentially dangerous moraine dammed lake is located on the north side of the himalaya its depth was surveyed using the syqwest hydrobox high resolution echo sounder and 6916 measurements were collected in september 2009 the maximum and average depths of the lake were 102 2 and 48 2 m respectively the morphology of the lake basin was modeled by constructing a triangulated irregular network and the lake was found to have a storage capacity of 0 064 0 002 km 3 multi source remote sensing images from landsat mss landsat tm etm and terra aster and a topographic map were digitized to delineate the outlines of the lake between 1977 and 2009 the results indicate that the length and area of the lake have increased during the past 32 years with a drastic expansion occurring since 2000 based on volume and area data of longbasaba lake in different periods we deduced an empirical equation of the lake volume area relationship that can be used to calculate the storage capacity of similar moraine dammed lakes in the himalayan region

prevention of outburst floods from periglacial lakes at grubengletscher valais swiss alps flood and debris flow hazards at grubengletscher near saas balen in the saas valley valais swiss alps result from the formation and growth of several lakes at the glacier margin and within the surrounding permafrost in order to prevent damage related to such hazards systematic investigations were carried out and practical measures taken the evolution of the polythermal glacier the creeping permafrost within the large adjacent rock glacier and the development of the various periglacial lakes were monitored and documented for the last 25 years by photogrammetric analysis of annually flown high resolution aerial photographs seismic refraction d c resistivity and gravimetry soundings were performed together with hydrological tracer experiments to determine the structure and stability of a moraine dam at a proglacial lake the results indicate a maximum moraine thickness of 100 m extremely high porosity and even ground caverns near the surface may have resulted from degradation of sub and periglacial permafrost following 19th 20th century retreat of the partially cold glacier tongue the safety and retention capacity of the proglacial lake were enhanced by deepening and reinforcing the outlet structure on top of the moraine complex the water level of an ice dammed lake was lowered and a thermokarst lake artficially drained

prehnite as an indicator mineral in the wadi nasb uralitized gabbro south sinai egypt abstract we report the first finding of prehnite in the southern sinai peninsula in a uralitized gabbro developed at the contact of the appinitic gabbro of the wadi nasb mafic intrusion wnmi with younger granitic intrusions subsolidus reactions with hydrothermal fluids caused the gabbro to gain al2o3 and cao while losing sio2 fe2o3 tio2 p2o5 ba nb zr and y uralitization proceeded through two stages of alteration and mineral replacement the early stage includes uralitization of pyroxene formation of new biotite as aggregates of small flakes transformation of primary amphiboles into actinolite and actinolitic hornblende and saussuritization of plagioclase the late stage of alteration is characterized by chloritization of mafic minerals apparent crystallization temperatures of the primary relics of pyroxene hornblende and biotite range from 800 1000 c 865 925 c and 700 c respectively suggesting partial resetting of the biotite exchange thermometer the early biotite forming alteration occurred at moderate temperature 300 450 c while the late chlorite forming alteration occurred at low temperature

modelling outburst floods from moraine dammed glacial lakes in response to climatic change the size and number of moraine dammed supraglacial and proglacial lake systems have increased dramatically in recent decades given an appropriate trigger the natural moraine dams that impound these proglacial lakes are breached producing catastrophic glacial lake outburst floods glofs these floods are highly complex phenomena with flood characteristics controlled in the first instance by the style of breach formation downstream glofs typically exhibit transient often non newtonian fluid dynamics as a result of high rates of sediment entrainment from the dam structure and channel boundaries combined these characteristics introduce numerous modelling challenges in this review the historical contemporary and emerging approaches available to model the individual stages or components of a glof event are introduced and discussed a number of methods exist to model the stages of a glof event dam breach models can be categorised as being empirical analytical or numerical in nature with each method having significant advantages and shortcomings empirical relationships that produce estimates of peak discharge and time to peak are straightforward to implement but the applicability of these models is often limited by the nature of the case study data from which they are derived furthermore empirical models neglect the inclusion of basic hydraulic principles that describe the mechanics of breach formation analytical or parametric models simulate breach development using simplified versions of the physically based equations that describe breach enlargement whilst complex physically based codes represent the state of the art in numerical dam breach modelling to date few of the latter have been applied to investigate the moraine dam failure problem despite significant advances in the physical complexity and availability of higher order hydrodynamic solvers the majority of published accounts that have attempted to reconstruct or predict glof characteristics have been limited often by necessity to the use of relatively simplistic models this is in part attributable to the unavailability of terrain models of many high mountain catchments at the fine spatial resolutions required for the effective application of numerically sophisticated codes and their proprietary and often cost prohibitive nature however advanced models are experiencing increasing use in the glacial hazards literature in particular the suitability of emerging mesh free particle based methods for simulating dam breach and glof routing may represent a solution to many of the challenges associated with modelling this complex phenomenon sources of uncertainty in the glof modelling chain have been identified by various workers however to date their significance for the robustness of reconstructive and predictive modelling efforts have been largely unexplored and quantified in detail these sources include the geometric and material characterisation of moraine dam complexes including lake bathymetry and the presence and extent of buried ice initial conditions freeboard precise spillway dimensions spatial discretisation of the down valley domain hydrodynamic model dimensionality and the dynamic coupling of successive components in the glof model cascade

crustal thickening of the lower crust of the kohistan arc n pakistan deduced from al zoning in clinopyroxene and plagioclase the lower crustal rocks of the kohistan complex northern pakistan are mostly composed of metabasic rocks such as pyroxene granulites garnet granulites and amphibolites we have investigated p t trajectories of the relic two pyroxene granulites which are the protolith of the amphibolites within the kamila amphibolite belt aluminous pyroxene retains igneous textures such as exsolution lamellae developed in the core the significant amount of al in clinopyroxene is buffered by breakdown reactions of plagioclase accompanied by film like quartz as a product at grain boundaries between plagioclase and clinopyroxene distinct al zoning profiles are preserved in pyroxene with exsolution lamellae in the core and in plagioclase adjacent to clinopyroxene in pyroxene granulites in the northern part of the kamila amphibolite belt al in clinopyroxene increases towards the rim and abruptly decreases at the outer rim and anorthite in plagioclase decreases towards the rim and abruptly increases near the grain boundary between plagioclase and clinopyroxene in the southern part of the kamila amphibolite belt al in clinopyroxene and anorthite in plagioclase simply increase towards the margins of the grains the anorthite zoning in plagioclase is in agreement with the zoning profiles of ca tschermaks and jadeite components inferred from variations of al na ti and fe3 in clinopyroxene assuming that the growth surface between them was in equilibrium geothermobarometry based on al zoning in clinopyroxene coexisting with plagioclase indicates that metamorphic pressures significantly increased with increasing temperature under granulite facies metamorphism the peak of granulite facies metamorphism occurred at conditions of about 800 c and 800 1100 mpa these prograde p t paths represent a crustal thickening process of the kohistan arc during the early to middle cretaceous the crustal thickening of the kohistan arc was caused by accretion of basaltic magma at mid crustal depths

assessing the internal structure of landslide dams subject to possible piping erosion by means of microtremor chain array and self potential surveys abstract an integrated geophysical approach comprising microtremor chain array and self potential surveys was used to assess the internal structure of landslide dams subject to possible piping erosion in selected sites in japan and kyrgyzstan the non invasive geophysical approach is cost effective environmentally friendly and portable and hence it has proven to be valuable for the geotechnical assessment of landslide dams where piping can trigger failure of the dam while the microtremor chain array survey results revealed the internal structure of the landslide dam the self potential survey results indicated the path of anomalous seepage zones in the surveyed sites of long existing landslide dams the presence of a seepage path in the dam was confirmed by a good correlation between the areas of low phase velocity and large negative self potential anomalies in summary this integrated geophysical approach could be useful for the early risk assessment of landslide dams and prediction of landslide dam failure by piping

significance of zr in rutile thermometry for deducing the decompression p t path of a garnet clinopyroxene granulite in the moldanubian zone of the bohemian massif

assessment of dam failure flood and a natural high magnitude flood in a hyperarid region using paleoflood hydrology nahal ashalim catchment dead sea israel 1 a dam failure flood in 1993 with a peak discharge of 600 700 m3 s 1 volume of 0 5 106 m3 and a natural rainfall runoff flood with a peak discharge of 420 m3s 1 volume of 2 0 106 m3 in 2004 in the nahal ashalim catchment 75 km2 in the hyperarid dead sea region were comparatively analyzed the two floods which caused serious damage to the dead sea works industries were analyzed for magnitude and frequency using regional analysis extrapolation from the short systematic record rainfall runoff modeling and paleoflood hydrology the 7600 year paleoflood record was reconstructed at the ashalim cave at the upper nahal ashalim peak discharges in this high gradient mountainous wadi are highly sensitive to the roughness coefficient and the flow regime the dam failure peak discharge is lower than the envelope curves of measured floods of the dead sea region and of paleofloods of the negev and the dead sea deserts the probability of the dam failure flood and the natural flood were estimated by various methods at 1 to 0 2 and 0 5 respectively adding the peak discharge of the october 2004 flood increased the probability from 0 2 to 0 5 0 2 the long paleoflood record encompasses different hydrological regimes related to climatic fluctuations which are not relevant to the present hydrological regime therefore the chosen period for frequency analysis was a d 1673 1996

outburst flood sedimentation on the proglacial tuttle canyon alluvial fan owens valley california u s a abstract surface deposits of the tuttle canyon alluvial fan eastern sierra nevada piedmont california mainly accumulated during a catastrophic outburst flood probably triggered by the failure of a moraine dammed lake in the steep 16 4 high relief 2361 m and high elevation to 4275 m catchment moraines of the catchment and upper fan facies a comprise unsorted sand to blocks derived from the granitic bedrock the main flood facies b is texturally like the moraine consisting of unsorted matrix supported sandy pebbly cobbly blocky boulder gravel in a single unit 3 to 8 m thick distributed across most of the 10 5 km long and 28 1 km2 fan facies b was deposited during the initial outburst flood phase as a high volume noncohesive sediment gravity flow ncsgf instigated by water rapidly descending over moraine it differs from the moraine by a planar unit geometry and a slope transverse long axis alignment of boulders ncsgf deposition was followed by a water flood phase caused by continued lake drainage subsequent to removal of loose sediment in the flood path this discharge carved channels 2 22 m deep and 5 60 m wide around and across fan ncsgf deposits with channels departing from various points along tuttle creek horseshoe separation scours also formed around bedrock spurs and laminated pebbly sand accumulated on the channel beds facies d flood discharge expanded on the distal fan into a sheetflood that first deposited a boulder unit facies e and then 4 m of cobbly sandy pebble gravel in planar beds 5 20 cm thick facies f the final flood phase entailed incision of tuttle creek wherein bouldery cobble gravel facies c was concentrated post flood modification of these deposits has been limited to secondary processes such as eolian deposition facies g and bioturbation outburst floods on fans of the sierra nevada piedmont ultimately are caused by the glacial transfer of colluvium from the upper catchment slopes into moraines on the valley floors that dam drainage to form lakes outburst floods differ from meteorological floods in the valley by the high water and sediment discharge achieved during a single event by deposition of massive ncsgf beds and by causing major changes to the landscape such as the carving of channels these differences produce fans with distinctive facies and hazards the former allowing their recognition in either modern or ancient settings

arc crustal differentiation mechanisms abstract the detailed vertical compositional and thermal structure of the entire kohistan arc section is constructed using 63 p t constraints and 209 plutonic whole rock analyses the aim is to better understand the nature of the chemical differentiation in the plutonic arc crust at different crustal levels results indicate that a distinct difference in character exists between the upper and lower plutonic arc crust plutonic rocks in the lower crust 25 30 km have whole rock chemical characteristics that indicate mineral accumulation and residual melt loss in these cumulate rocks there is a systematic chemical stratification of decreasing incompatible trace elements with depth e g rb k2o in contrast the plutonic rocks of the upper crust represent mainly frozen liquids and show no systematic relationship between chemical composition and intrusion depth these results clearly indicate that magmatic differentiation in the kohistan arc dominantly occurred in the deeper arc crust 30 km consistent with the lower crustal hot zone model to understand the role of density barriers for melt stagnation in the crust and thereby for the observed chemical stratification the detailed density structure of the plutonic arc crust is compared to melt densities calculated for plutonic rocks with near liquid compositions results indicate that melts are consistently less dense than rocks and there is no evidence for a neutral buoyancy line controlling melt emplacement it is speculated that melt stagnation in the lower arc crust and subsequent chemical differentiation of a felsic upper and mafic lower continental crust is dominantly controlled by temperature and to a lesser extent to density or rheological barriers

uncertainty of predictions of embankment dam breach parameters risk assessment studies considering the failure of embankment dams often require the prediction of basic geometric and temporal parameters of a breach or the estimation of peak breach outflows many of the relations most commonly used to make these predictions were developed from statistical analyses of data collected from historic dam failures the prediction uncertainties of these methods are widely recognized to be very large but have never been specifically quantified this paper presents an analysis of the uncertainty of many of these breach parameter and peak flow prediction methods application of the methods and the uncertainty analysis are illustrated through a case study of a risk assessment recently performed by the bureau of reclamation for a large embankment dam in north dakota

metagabbros of the gangdese arc root south tibet implications for the growth of continental crust abstract the gangdese batholith of the southern tibet is regarded as a principal component of the pre himalayan collision andean type continental margin however the gangdese arc root remains poorly understood because most of previous studies concentrated on granitoids from the middle and upper crust of the arc in this paper we report new petrochemical and geochronological characteristics of metagabbros occurred as a part of the late cretaceous lilong batholith in the eastern gangdese arc the gabbros with protolith ages of 82 95 ma underwent slightly late 68 77 ma granulite facies metamorphism and nearly coeval anatexis typical of lower arc crusts the metagabbros and diorites of the lilong batholith show geochemical features of juvenile crust in continental magmatic arcs and an original magmatic differentiation trend with gabbros formed as the cumulates whereas diorites as the crystalline products of evolved magmas the lilong batholith forms an arc crustal section with a possible thickness of 20 30 km and may have an overall andesitic composition providing a support for the andesite model of continental crust growth

shear strain localization from the upper mantle to the middle crust of the kohistan arc pakistan shear structures from mantle to middle crust levels of the kohistan palaeo island arc in pakistan are described pre himalayan ductile shear zones show a wide variety in size and shape and developed from gabbro subsolidus to amphibolite facies conditions their lithological context and geological history give insights into mechanisms that initiate shear strain localization factors that control stabilization of deformation in shear zones and flow properties at the mantle crust transition shear strain localization began within compositional gradients gabbros were more prone to localization into anastomosing patterns than diorites and granites which show more homogeneous strain shear strain localization during cooling led to less numerous but longer and thicker shear zones viscous heating within shear zones resulted in melt production and segregation in deformation structures and seems to have taken part in the plutonic history of the arc using kohistan as an example we suggest that the plutonic lower crust of arcs is strongly affected by subhorizontal synmagmatic shear zones probably consistent with the bulk flow direction of the subduction zone these features can obviously be preserved in collision orogens and may be mistaken for structures documenting the continental collision

pre collisional anastomosing shear zones in the kohistan arc nw pakistan ductile strain localisation commonly forms a pattern of shear zones anastomosing around lenses of less deformed rock initiation and development history of anastomosing shear zones which are little documented are studied through the description of the structures and the deformation history of plutonic rocks that form the lower crust of the kohistan complex structures and textures developed in these rocks result from primary magmatic to solid state regional strain overprinted by anastomosing shear zones the primary strain was mainly acquired during magmatic emplacement at 100 90 ma strain localisation took place continuously from magmatic emplacement to solid state deformation during cooling of the plutons and formed 3 successive sets of shear zones set 1 is composed of associated discrete riedel and thrust shear zones developed above solidus conditions during sw ward thrusting continuous deformation from solidus to amphibolite facies conditions between 100 and 83 ma formed the second set of shear zones the lower amphibolite facies set 3 shear zones are differentiated by larger strain recorded in the thicker mylonitic zones and enlargement of the spacing between shear zones during cooling the anastomosing pattern of shear zones described here probably represents arc related deformation during subduction of the tethys oceanic lithosphere below the kohistan arc complex

multiple mantle sources during island arc magmatism u pb and hf isotopic evidence from the kohistan arc complex pakistan this paper presents high precision u pb ages and initial hf isotopic compositions of zircon from mafic to felsic rocks of the kohistan arc complex pakistan three magmatic pulses tapping geochemically different reservoirs are distinguished partial melting of mantle with morb type isotopic characteristics generated 99 92 ma old magmas plutonism around 85 ma tapped a more fertile mantle source most likely consisting of a 600 ma old metasomatically enriched mantle or of mantle contaminated by an old sedimentary component 82 ma old felsic peraluminous dykes have morb type isotopic compositions considered to be inherited from remelting earlier magmas in the deep base of the arc the isotopic results demonstrate several and rather rapid changes in melt source region during arc development they also show that there was subordinate continental influence and negligible importance of slab components for the hf budget during the generation of the kohistan arc complex

the 2000 yigong landslide tibetan plateau rockslide dammed lake and outburst flood review remote sensing analysis and process modelling abstract in april 2000 a large scale rock avalanche dammed the yigong zangpo river forming an extensive rockslide dammed lake the impoundment lasted for 62 days before a catastrophic breaching caused a massive outburst flood in the yarlung zangpo tibet and the dihang rivers india that travelled downstream to the main floodplain of the brahmaputra in northeastern india in response to discrepancies in the published literature on the event we present a review and re evaluation of the characteristics of the rock avalanche and associated landslide dammed lake we use digital topographical data srtm 3 and dynamic landslide modelling dan w and dan3d to determine the salient characteristics of the damming landslide and to characterise its behaviour our analysis indicates that the volume of the damming rockslide was ca 115 mm3 including 91 mm3 from the initial rockslope failure bulked during disaggregation to 109 mm3 and 6 mm3 from entrainment during its 10 1 km travel down zhamulong gully the debris travelled with an average velocity of 15 18 m s and resulted in a landslide dam on the yigong river with a minimum height of about 55 m using landsat 7 imagery obtained before during and after impoundment in conjunction with an srtm 3 dem we reproduced the filling of the lake we determine that the landslide dam formed an extensive reservoir with an impounded volume of 2 015 gm3 and a maximum possible lake level of 2264 m asl rounded to 2265 m asl our figures differ from those previously published but are believed to be well constrained verifiable estimates of the volumes of the 2000 yigong events the outburst occurred after an attempt by army personnel to manually dig a spillway over the landslide debris and resulted in the entire volume of the lake draining in about 12 h the outburst flood travelled over 500 km south into india with a recorded rise in river level of 5 5 m at the pasighat gauging station 462 km downstream in terms of historical outburst volumes from rockslide dammed lakes the volume of the 2000 yigong event is only exceeded by that of the 1841 outburst flood from the indus river rockslide dammed lake northern pakistan

influence of textural properties on the failure mode and process of landslide dams abstract the failure of a landslide dam is a sudden geo hazard which can significantly threatens the lives and property of local residents in this study 11 experiments were designed to reproduce the failure process of landslide dams with different grain size distributions and hydrodynamic conditions in order to fully consider the influence of seepage on the stability of landslide dams with different textural properties the inflow discharge was small in these tests by analyzing the experimental data we found that the textural properties plays a key role in the failure modes and process of landslide dams the eleven tests produced five different results the landslide dam in experiment 1 and 8 remained stable the landslide dam in experiment 2 partially failed in experiments 3 6 the dams failed due to overtopping and erosion while in experiment 7 the dam failed due to overtopping and soil collapse in experiment 9 11 the dams failed due to piping overtopping and erosion in addition the evolution of the outflow discharge and density also varied for the different textural properties of the dam materials based on the experimental results the landslide dam materials were classified as coarse matrix controlled medium particle controlled fine matrix controlled and balanced composition the failure modes and process as well as the evolution characteristics of the outflow discharge and flow density were all summarized providing a scientific reference for disaster prevention and mitigation research of landslide dams

late pleistocene subaerial debris flow facies of the bow valley near banff canadian rocky mountains a thick late pleistocene sequence comprising multiple beds of massive diamict facies resting on outwash gravels occurs along the bow river near banff alberta diamicts have a simple sheet like geometry which dip downvalley at between 5 and 10 with largely conformable bedding contacts the sediments are strongly bimodal in texture consisting of clasts supported by a silty sand matrix prolate clasts show a weak a axis alignment parallel and transverse to the trend of the bow valley with a weak imbrication clasts of soft sediment are common the diamict sequence has a maximum thickness of 30 m infills the valley floor over an area of approximately 12 km2 and buries a channelled topography cut on the surface of underlying outwash gravels abandoned braided channels veneered by windblown sand containing volcanic tephra dated at 6600 yr bp occur on the infill surface diamict facies were emplaced as subaerial debris flows derived by the mixing and remobilization of large volumes of outwash and glaciolacustrine sediment orientation data from clasts and a few basal grooves indicate that debris was derived upvalley and from adjacent valleyside slopes a major episode of debris flow sedimentation may have been triggered by the abrupt drainage of lakes in tributary valleys as the bow valley glacier retreated downslope resedimentation of large volumes of sediment resulted in braided river aggradation downstream along the bow river and can be dated to between 12 000 and 10 000 yr bp similar conditions probably occurred during deglaciation throughout the canadian cordillera and many other alpine areas where poorly sorted late glacial debris flow facies have been mistaken for tills deposited directly by glaciers the late glacial setting identified in this paper provides a basis of comparison with ancient continental glacial facies preserved in areas of active tectonism and high relief

an unusual jokulhlaup resulting from subglacial volcanism solheimajokull iceland jokulhlaups glacial outburst floods are frequent in glaciated terrain jokulhlaups exhibiting a sudden rise to peak discharge have not been subject to detailed investigation a volcanically generated flood burst from solheimajokull iceland in july 1999 this paper accounts for the causes characteristics and impacts of this flood pre and post flood fieldwork was carried out at solheimajokull allowing the reconstruction of mean flow velocities and peak discharge flood onset was rapid rising to a peak discharge of 4 4 x 103 m3s 1 1 2 x 103 m3s 1 within one hour high basal water pressures resulted in floodwater bursting through the glacier surface ice rip up clasts containing glacial diamict provided evidence of floodwater contact with the glacier bed within the glacier jokulhlaup sedimentation occurred within hydrofractures and conduits generating complex hydrofracture fills and esker ridges in the proglacial zone regions of flow expansion associated with rapid reductions in sediment transport capacity controlled the locations of major jokulhlaup sedimentation a large fan composed of material of up to boulder size was deposited at the glacier snout two ice marginal basins filled and drained during the jokulhlaup one of the basins jokulsargil emptied rapidly during the flood via ice dam flotation accentuating peak jokulhlaup discharge high rates of downstream peak discharge attenuation during the july 1999 jokulhlaup provides an analogy with flash flood hydrographs in semi arid regions and the catastrophic failure of man made dams the july 1999 jokulhlaup was initially triggered by the subglacial volcanic eruption but the characteristics of the flood were accentuated by within event meltwater storage and release this unusual jokulhlaup provides an important addition to our understanding of the spectrum of distinctive jokulhlaup characteristics

tectonic stacking of back arc formations in the thelichi section indus valley of the kohistan arc northern pakistan abstract metamorphosed volcanic and sedimentary rocks of the jaglot group are exposed along the west bank of the indus river near thelichi the structural bottom unit the thelichi formation is composed of metavolcaniclastic metavolcanic metapelitic and metacalcareous rocks bedding planes of the thelichi formation trend e w or nw se and dip steeply to the n the middle unit gashu confluence volcanics is composed of metavolcaniclastic metavolcanic and metacalcareous rocks bedding planes trend nw se and dip moderately to the n the top unit the gilgit formation is composed of interlayered metapsammitic and metapelitic rocks graded bedding cross bedding and pillow structures are preserved in these metamorphic rocks of the jaglot group those indicate clastic sedimentary and volcanic origins there is no major repetition of layers due to folding so called the jaglot syncline as is evidenced by the consistent northward younging of the beds the three lithological units constitute a north dipping tectonic stack the tectonic stack was provably caused by the northward subduction of the back arc basin under the asian margin and subsequent collision between the asia and the kohistan the closure of back arc basin

formulas for the peak discharge from breached earthfill dams abstractalthough advanced physically based models have been presented in the last years there is still much interest in equations for predicting the peak discharge indeed simple relations are very useful for technical purposes especially when rough calculations are acceptable this paper presents new equations for assessing the peak discharge of the flood hydrograph caused by the gradual erosion of earth dams the equations are obtained by a regression analysis carried out on the peak discharges provided by a physically based numerical model the approach proposed in this paper has the advantage of taking into account some parameters usually neglected by common best fit equations that have strong influence on the peak discharge in particular the equations discussed in this paper take into account the susceptibility to erosion of the dam the shape of the reservoir and the ratio of filling of the reservoir for failures caused by piping the usefulness of the equations is shown through a comparison w

sedimentary evidence of outburst deposits induced by the diexi paleolandslide dammed lake of the upper minjiang river in china abstract this study reveals that a distinct damming incident occurred during a prehistory period approximately 30 ka bp in the upper minjiang river at the southeastern margin of the tibetan plateau which formed a giant dammed lake it can be inferred that paleoseismic induced major landslides were the direct cause of the river damming the dammed lake breached and caused a large outburst flood at about 27 ka bp between the section of the prehistoric ancient dam body and its downstream areas 5 km an abundance of diamicts consisting of a poor sorted wide range of particle sizes including gravel sand and minor silt and clay have been observed the outburst deposits in the diexi area maybe divided into two periods the thick outburst deposits represented the earlier and largest dammed break event and the deposit terrace was due to the subsequent and smaller dammed break event the sedimentary structures of the outburst deposits included imbrication cavitation matrix and massive structures as well as gravel support stacked structures furthermore a special sedimentary structure became evident consisting of a rhythmite interbedded structure composed of a coarser gravel layer and a finer sand and gravel layer with no sand lens formed within the layers this special structure can potentially provide an important original criterion for the outburst deposits in this area the two types of facies associations have been recorded which indicate contrasting sediment transport regimes the characteristics of boulder facies were most likely associated with hyperconcentrated flood flows however the finer grained gm gfm grm facies which overlaid the bcm facies were determined to represent the waning stage of the flooding events the delicate structures as well as the absence of coarse components in the sh facies indicated an episode of accumulations which was subsequent to the deposition of the underlying bcm facies the results of this study potentially provide important implications for the interpretation of the diamicts in the diexi area the grain size frequency curves of the outburst deposits in the diexi area were found to all be bimodal a main peak and an inconspicuous sub peak these findings indicated a poorly sorted sedimentary structure it was found that from the upstream segment to the downstream segment the gravel sediment became gradually lessened while the fine grained sediment increased additionally the outburst flood hydrodynamic intensity was found to have gradually become weakened

petrography and mineral chemistry of the composite deboullie pluton northern maine u s a implications for the genesis of cumo mineralization abstract biotite and apatite mineral chemistry particularly halogen abundances and ratios are used to investigate the relation of the two contrasting parts of the deboullie composite pluton syenite granodiorite located in northern maine biotite mineral chemistry helps to classify the weakly developed porphyry style mineralization cu mo associated with syenitic rocks of the deboullie pluton unmineralized syenite consists of k feldspar plagioclase quartz biotite hornblende clinopyroxene and minor amounts of apatite titanite magnetite zircon and allanite biotite and apatite occur within the matrix of the rocks and within small multiphase inclusions hosted by clinopyroxene the inclusions are interpreted to be crystallized melt inclusions rather than solid inclusions that were trapped by clinopyroxene during growth the multiphase inclusions consist of k feldspar quartz biotite apatite magnetite the f contents of biotite display a strong positive correlation with the phlogopite component or xphl xphl mg sum octahedral cations biotites from the multiphase inclusions have higher f contents and higher values of f f cl oh and xphl than biotites in the matrix that presumably formed later during crystallization and or re equilibrated with late stage fluids contents of tio2 largely overlap for the inclusion and matrix biotite apatite compositions plot within the fluorapatite field f f cl oh 0 57 0 99 apatites in the multiphase inclusions have higher cl contents than apatites in the matrix or those enclosed in biotite biotite apatite geothermometry for the multiphase inclusions yields magmatic or near magmatic temperatures 725 850 c biotite apatite pairs outside the inclusions yield temperatures that range from near magmatic 600 775 c to much lower x f x cl and xphl was used to infer hf hcl fugacity ratios in associated hydrothermal fluids and indicates that biotite from the deboullie pluton is strikingly similar to biotite from the porphyry cu deposit at santa rita new mexico but distinctly different from biotite from the porphyry mo deposit at henderson colorado the assemblage quartz magnetite titanite implies an oxidation state for the deboullie pluton well above the quartz magnetite fayalite buffer which is also consistent with magmas associated with porphyry cu deposits on a regional scale biotite compositions from granitic plutons in maine do not vary in a systematic manner this implies that biotite compositions no longer directly reflect source compositions finally biotite and apatite compositions of the syenite and granodiorite are different compositional ranges in the granodiorite are more restricted than those in the syenite this provides evidence that the two parts of this composite pluton had different origins and are not related by crystal fractionation

methods for predicting peak discharge of floods caused by failure of natural and constructed earthen dams floods from failures of natural and constructed dams constitute a widespread hazard to people and property expeditious means of assessing flood hazards are necessary particularly in the case of natural dams which may form suddenly and unexpectedly we revise statistical relations derived from data for past constructed and natural dam failures between peak discharge qp and water volume released v0 or drop in lake level d but assert that such relations even when cast into a dimensionless form are of limited utility because they fail to portray the effect of breach formation rate we then analyze a simple physically based model of dam breach formation to show that the hydrograph at the breach depends primarily on a dimensionless parameter kv0 gl 2d7 2 where k is the mean erosion rate of the breach and g is acceleration due to gravity the functional relationship between qp and takes asymptotically distinct forms depending on whether 1 relatively slow breach formation or small lake volume or 1 relatively fast breach formation or large lake volume theoretical predictions agree well with data from dam failures for which k and thus can be estimated the theory thus provides a rapid means of predicting the plausible range of values of peak discharge at the breach in an earthen dam as long as the impounded water volume and the water depth at the dam face can be estimated