hydraulic physical and rheological characteristics of rain triggered lahars at semeru volcano indonesia lahars volcanic debris flows have been responsible for 40 of all volcanic fatalities over the past century mount semeru east java indonesia is a persistently active composite volcano that threatens approximately one million people with its lahars and pyroclastic flows despite their regularity the behaviour and the propagation of these rain triggered lahars are poorly understood in situ samples were taken from lahars in motion at two sites in the curah lengkong river on the southeast flank of semeru providing estimates of the particle concentration grain size spectrum grain density and composition this enables us to identify flow sediment from three categories of lahars a hyperconcentrated flow b non cohesive clast and matrix supported debris flow and c muddy flood to understand hyperconcentrated flow sediment transport processes it is more appropriate to sample the active flows than the post event lahar deposits because in situ sampling retains the full spectrum of the grain size distribution rheometrical tests on materials sampled from moving hyperconcentrated flows were carried out using a laboratory vane rheometer despite technical difficulties results obtained on the 63 180 and 400 m fractions of the sampled sediment suggest a purely frictional behaviour importantly and contrary to previous experiments conducted with monodisperse suspensions our results do not show any transition towards a viscous behaviour for high shear rates these data provide important constraints for future physical and numerical modelling of lahar flows copyright 2010 john wiley sons ltd

biological and physical controls on n2 o2 and co2 distributions in contrasting southern ocean surface waters we present measurements of pco2 o2 concentration biological oxygen saturation o2 ar and n2 saturation n2 in southern ocean surface waters during austral summer 2010 2011 phytoplankton biomass varied strongly across distinct hydrographic zones with high chlorophyll a chl a concentrations in regions of frontal mixing and sea ice melt pco2 and o2 ar exhibited large spatial gradients range 90 to 450 atm and 10 to 60 respectively and covaried strongly with chl a however the ratio of biological o2 accumulation to dissolved inorganic carbon dic drawdown was significantly lower than expected from photosynthetic stoichiometry reflecting the differential time scales of o2 and co2 air sea equilibration we measured significant oceanic co2 uptake with a mean air sea flux 10 mmol m 2 d 1 that significantly exceeded regional climatological values n2 was mostly supersaturated in surface waters mean n2 of 2 5 while physical processes resulted in both supersaturation and undersaturation of mixed layer o2 mean o2phys 2 1 box model calculations were able to reproduce much of the spatial variability of n2 and o2phys along the cruise track demonstrating significant effects of air sea exchange processes e g atmospheric pressure changes and bubble injection and mixed layer entrainment on surface gas disequilibria net community production ncp derived from entrainment corrected surface o2 ar data ranged from 40 to 300 mmol o2 m 2 d 1 and showed good coherence with independent ncp estimates based on seasonal mixed layer dic deficits elevated ncp was observed in hydrographic frontal zones and stratified regions of sea ice melt reflecting physical controls on surface water light fields and nutrient availability

particulate organic carbon fluxes to the ocean interior and factors controlling the biological pump a synthesis of global sediment trap programs since 1983 particulate organic carbon poc is vertically transported to the oceanic interior by aggregates and their ballasts mainly caco3 and biogenic opal with a smaller role for lithogenic aerosols through the mesopelagic zone diel migrating zooplankton communities effect vertical transport and remineralization of poc in the upper layers of the ocean below 1 5 km the presence of zooplankton is reduced and thus the aggregates travel mainly by gravitational transport we normalized the fluxes of poc caco3 and biogenic opal from data published on samples collected at 134 globally distributed bottom tethered time series sediment trap ts trap stations to annual mole fluxes at the mesopelagic bathypelagic boundary m b at 2 km and defined them as fm bcorg fm bcinorg and fm bsibio using this global data set we investigated 1 the geographic contrasts of poc export at m b and 2 the supply rate of co2 to the world mesopelagic water column fm bcorg varies from 25 pacific warm pool to 605 divergent arabian sea mmolc m 2 yr 1 fm bcinorg varies from 8 high latitude polar oceans or 15 pacific warm pool to 459 divergent arabian sea mmolc m 2 yr 1 and fm bsibio the most spatially temporally variable flux ranges from 6 north atlantic drift to 1118 pacific subarctic gyre mmolsi m 2 yr 1 the oceanic region exhibiting the highest poc flux over a significantly large region is the area of the north pacific boreal gyres where the average fm bcorg 213 fm bcinorg 126 and fm bsibio 578 mmol m 2 yr 1 fm bcorg and fm bcinorg are particularly high in large upwelling margins including the divergent arabian sea and off cape verde one of the data sets showing the lowest flux over a significant region basin is fm bcorg 39 fm bcinorg 69 and fm bsibio 22 mmol m 2 yr 1 in the north pacific subtropical tropical gyres pan atlantic average fluxes are similar except fm bsibio fluxes are even lower where corg cinorg and sibio cinorg are 1 defines the carbonate ocean and where these ratios are 1 defines the silica ocean the carbonate ocean occupies about 80 of the present world pelagic ocean between the two major oceanographic fronts the north pacific polar front and the antarctic polar front and the silica ocean is found on the polar sides of these fronts the total global annual fluxes of fm bcorg fm bcinorg and fm bsibio at m b calculated by parameterizations of the export flux data from 134 stations are surprisingly similar 36 2 33 8 and 34 6 teramol yr 1 120 112 and 114 mmol m 2 yr 1 respectively resulting in a near uniform binary ratio between the above three elements of about one the global ternary ratios estimated from 152 ts trap samples of the three elements are 35 32 33 from our global fm bcorg and a published model estimate of the global export production we estimate the regeneration rate of co2 through the mesopelagic zone by the biological pump is 441 teramolc yr 1 based on our global fm bcinorg and recently estimated global primary production of pic 36 86 teramolc yr 1 of pic is assumed to be dissolved within the upper 2 km of the water column

rainfall runoff properties of tephra simulated effects of grain size and antecedent rainfall abstract rain triggered lahars rtls are a significant and often persistent secondary volcanic hazard at many volcanoes around the world rainfall on unconsolidated volcaniclastic material is the primary initiation mechanism of rtls the resultant flows have the potential for large runout distances 100 km and present a substantial hazard to downstream infrastructure and communities rtls are frequently anticipated in the aftermath of eruptions but the pattern timing and scale of lahars varies on an eruption by eruption and even catchment by catchment basis this variability is driven by a set of local factors including the grain size distribution thickness stratigraphy and spatial distribution of source material in addition to topography vegetation coverage and rainfall conditions these factors are often qualitatively discussed in rtl studies based on post eruption lahar observations or instrumental detections conversely this study aims to move towards a quantitative assessment of rtl hazard in order to facilitate rtl predictions and forecasts based on constrained rainfall grain size distribution and isopach data calibrated simulated rainfall and laboratory constructed tephra beds are used within a repeatable experimental set up to isolate the effects of individual parameters and to examine runoff and infiltration processes from analogous rtl source conditions laboratory experiments show that increased antecedent rainfall and finer grained surface tephra individually increase runoff rates and decrease runoff lag times while a combination of these factors produces a compound effect these impacts are driven by increased residual moisture content and decreased permeability due to surface sealing and have previously been inferred from downstream observations of lahars but not identified at source water and sediment transport mechanisms differ based on surface grain size distribution a fine grained surface layer displayed airborne remobilisation accretionary pellet formation rapid surface sealing and infiltration excess overland flow generation whilst a coarse surface layer demonstrated exclusively rainsplash driven particle detachment throughout the rainfall simulations this experimental protocol has the potential to quantitatively examine the effects of a variety of individual parameters in rtl initiation under controlled conditions

dissolved iron in the southern ocean atlantic sector abstract we report a comprehensive dataset of dissolved iron fe comprising 482 values at 22 complete vertical profiles along a 1 latitudinal section at the zero meridian in addition a shorter high resolution 00 09 surface section of the southernmost part of the transect 66 00 69 35 s is presented within the upper surface mixed layer the concentrations of dissolved fe vary between 0 1 and 0 3 nm an inverse trend versus fluorescence suggests significant fe removal by plankton blooms vertical mixing and upwelling are the most important supply mechanisms of iron from deep waters to the upper surface mixed layer at lower latitude 42 s there is a distinct maximum of 0 6 0 7 nm in the 2000 3000 m depth range due to inflow of north atlantic deep water in one region 55 s elevated dissolved fe found in the surface mixed layer is ascribed to the recent deposition of aeolian dust originating from south america close to the antarctic continent there is an indication of fe supply in surface waters from icebergs in the deep waters there is a strong indication of a hydrothermal plume of dissolved fe and mn over the ridge in the bouvet region 52 56 s in the weddell gyre basin the dissolved fe in the deep water is 0 47 0 16 nm in the eastward flow at 56 62 s and is lower with a value of 0 34 0 14 nm in the westward flow at high 62 69 s latitude at the edge of the continental ice sheet on the prime meridian the continental margin of the antarctic continent appears to be lesser source of dissolved fe than in any other place in the world this is likely because it is unique in being overlain by the extending continental ice sheet that largely prevents biogeochemical cycling

the seasonal cycle of carbonate system processes in ryder bay west antarctic peninsula the carbon cycle in seasonally sea ice covered waters remains poorly understood due to both a lack of observational data and the complexity of the system here we present three consecutive seasonal cycles of upper ocean dissolved inorganic carbon dic and total alkalinity measurements from ryder bay on the west antarctic peninsula we attribute the observed changes in dic to four processes mixing of water masses air sea co2 flux calcium carbonate precipitation dissolution and photosynthesis respiration this approach enables us to resolve the main drivers of the seasonal dic cycle and also investigate the mechanisms behind interannual variability in the carbonate system we observe a strong asymmetric seasonal cycle in the carbonate system driven by physical processes and primary production in summer melting glacial ice and sea ice and a reduction in mixing with deeper water reduce the concentration of dic in surface waters the dominant process affecting the carbonate system is net photosynthesis which reduces dic and the fugacity of co2 making the ocean a net sink of atmospheric co2 in winter mixing with deeper carbon rich water and net heterotrophy increase surface dic concentrations resulting in ph as low as 7 95 and aragonite saturation states close to 1 we observe no clear seasonal cycle of calcium carbonate precipitation dissolution but some short lived features of the carbonate time series strongly suggest that significant precipitation of calcium carbonate does occur in the bay the variability observed in this study demonstrates that changes in mixing and sea ice cover significantly affect carbon cycling in this dynamic environment maintaining this unique time series will allow the carbonate system in seasonally sea ice covered waters to be better understood

regulation of algal blooms in antarctic shelf waters by the release of iron from melting sea ice during summer 1995 96 we measured iron in the water column and conducted iron enrichment bottle incubation experiments at a station in the central ross sea 76 30 s 170 40 w first in the presence of melting sea ice and 17 days later in ice free conditions we observed a striking temporal change in mixed layer dissolved iron concentrations at this station from 0 72 2 3 nm with sea ice present to 0 16 0 17 nm in ice free conditions these changes were accompanied by a significant drawdown in macronutrients and an approximate doubling of algal diatom biomass our incubation experiments suggest that conditions were iron replete in the presence of sea ice and iron deficient in the absence of sea ice we surmise that bioavailable iron was released into seawater from the melting sea ice stimulating phytoplankton production and the biological removal of dissolved iron from the mixed layer until iron limited conditions developed these observations suggest that the episodic release of bioavailable iron from melting sea ice is an important factor regulating phytoplankton production particularly ice edge blooms in seasonally ice covered antarctic waters

moored sediment trap measurements of carbon export in the subantarctic and polar frontal zones of the southern ocean south of australia sediment trap moorings were deployed from september 21 1997 through february 21 1998 at three locations south of australia along 140 e at 47 s in the central subantarctic zone saz with traps at 1060 2050 and 3850 m depth at 51 s in the subantarctic front with one trap at 3080 m and at 54 s in the polar frontal zone pfz with traps at 830 and 1580 m particle fluxes were high at all the sites 18 32 g m 2 yr 1 total mass and 0 5 1 4 g organic carbon m 2 yr 1 at 1000 m assuming minimal flux outside the sampled summer period these values are similar to other southern ocean results and to the median estimated for the global ocean by lampitt and antia 1997 and emphasize that the southern ocean exports considerable carbon to the deep sea despite its high nutrient low chlorophyll characteristics the saz site was dominated by carbonate 50 of total mass and the pfz site by biogenic silica 50 of total mass both sites exhibited high export in spring and late summer with an intervening low flux period in december for the 153 day collection period particulate organic carbon export was somewhat higher in all the traps in the saz range 0 57 0 84 gc m 2 than in the pfz range 0 31 0 53 with an intermediate value observed at the saf 0 60 the fraction of surface organic carbon export estimated from seasonal nutrient depletion lourey and trull 2001 reaching 1000 m was indistinguishable in the saz and pfz despite different algal communities

rate of sediment yield following small scale volcanic eruptions a quantitative assessment at the merapi and semeru stratovolcanoes java indonesia sediment yields were calculated on the anks of merapi and semeru volcanoes in java indonesia using two different methods during the rst year following the 22 november 1994 eruption of merapi a sediment yield in excess of 1 5 105 m3 km 2 yr 1 was calculated in the boyong river drainage basin based on the volumes of sediment that were trapped by ve check dams at semeru sediment discharges were assessed in the curah lengkong river from direct measurements on the lahars in motion and on the most signi cant stream ows the calculated rate of sediment yield during one year of data in 2000 was 2 7 105 m3 km 2 yr 1 sediment yields are dominated by rain triggered lahars which occur every rainy season in several drainage basins of merapi and semeru volcanoes mostly during the rainy season extending from october to april the return period of lahars carrying sediment in excess of 5 105 m3 is about one year in the curah lengkong river at semeru at merapi the volume of sediments transported by a lahar did not exceed 2 8 105 m3 in the boyong river during the rainy season 1994 95 on both volcanoes the sediments are derived from similar sources pyroclastic ow surges deposits rockfalls from the lava domes and old material from the riverbed and banks however daily explosions of vulcanian type at semeru provide a more continuous sediment supply than at merapi therefore sediment yields are larger at semeru copyright 2004 john wiley sons ltd

luminescence dating of loess palaeosol sequences and coversands methodological aspects and palaeoclimatic implications abstract of the terrestrial archives loess palaeosol sequences provide a most complete record of climatic change this may be compared with the marine oxygen isotope stratigraphy and may help in the reconstruction of past atmospheric circulation patterns numerical chronometry of loess palaeosol sequences has generally been based on correlation of variations in climatic proxies such as magnetic susceptibility and particle sizes with marine isotopic data such chronometric assignments involve implicit assumptions about the constancy of sedimentation rates and particle fluxes through time this review presents a brief survey of the present status methodology outstanding problems and interpretational aspects of luminescence techniques and discusses the import of luminescence ages on global land sea correlations statistical analysis of the ages suggests episodicity of loess accumulation with extended periods of quiescence recent luminescence dating studies on closely spaced samples also lead to a similar inference luminescence ages imply high variability in loess sedimentation rates this conflicts with the assumption made in some current attempts to correlate loess records with marine records of almost constant particle fluxes a review of source proximal coversand deposits of northwest europe is also presented evidence of the onset of coversand deposition at 15 ka with a peak in accretion during the younger dryas and subsequent minor reactivation episodes is discussed

late holocene inland dune activity in the uk a case study from breckland east anglia inland dune fields found in breckland east anglia uk have previously been correlated with the widespread late devensian coversands of the region and a seventeenth century sandflood which is known to have inundated the village of santon downham a programme of optically stimulated luminescence and radiocarbon dating undertaken on the dunes at wangford warren and santon downham reveals that episodic aeolian activity has taken place during the last 7000 years five sand depositional phases on breckland dunes are identified c 6500 c 1600 1100 c 500 c 400 335 and from c 200 30 years before present between c 2120 1840 years ago and within the period 1100 300 years ago quiescent periods allowed the development of fen peat and soils local controlling factors on aeolian activity in breckland appear to be related to anthropogenic activities and livestock sheep and rabbits reducing vegetation cover and decreased precipitation and sea levels which led to lowering of water tables breckland aeolian activity when compared to the national and sub continental holocene aeolian activity record shows a high level of concordance the underlying forcing factor for late holocene dune activity in the uk and elsewhere in europe appears to be climatic instability in the north atlantic associated with both the little ice age and previous similar events which led to increased storminess climatic variability and lower temperatures

biological and physical controls on o 2 ar ar and p co 2 variability at the western antarctic peninsula and in the drake passage abstract using simultaneous sub kilometer resolution underway measurements of surface o2 ar total o2 and pco2 from annual austral summer surveys in 2012 2013 and 2014 we explore the impacts of biological and physical processes on the o2 and pco2 system spatial and interannual variability at the western antarctic peninsula wap in the wap mean o2 ar supersaturation was 7 6 9 1 and mean pco2 supersaturation was 28 22 we see substantial spatial variability in o2 and pco2 including sub mesoscale mesoscale variability with decorrelation length scales of 4 5 km consistent with the regional rossby radius this variability is embedded within onshore offshore gradients o2 in the lter grid region is driven primarily by biological processes as seen by the median ratio of the magnitude of biological oxygen o2 ar to physical oxygen ar supersaturation anomalies relative to atmospheric equilibrium 2 6 however physical processes have a more pronounced influence in the southern onshore region of the grid where we see active sea ice melting total o2 measurements should be interpreted with caution in regions of significant sea ice formation and melt and glacial meltwater input pco2 undersaturation predominantly reflects biological processes in the lter grid in contrast we compare these results to the drake passage where gas supersaturations vary by smaller magnitudes and decorrelate at length scales of 12 km in line with latitudinal changes in the regional rossby radius here biological processes induce smaller o2 ar supersaturations mean 0 14 1 3 and pco2 undersaturations mean 2 8 3 9 than in the wap and pressure changes bubble and gas exchange fluxes drive stable ar supersaturations

sedimentary processes of canadian arctic fjords abstract conceptual models of circulation and sedimentation in arctic fjords are presented to illustrate the current understanding of these environments circulation is a vigorous process in these fjords and is enhanced by the loss of the freshwater cap during the long winter period of near zero inflow the process of brine rejection during the formation of sea ice and the role of glaciers and icebergs injecting freshwater at depth on the other hand the presence of sea ice blocks reduces the mixing action of wind which may otherwise represent the largest input of energy to fjord circulation it also provides a freshwater layer on melting and may in some circumstances damp the amplitude of tides during summer large loads of glacial sediment entering arctic fjords are separated into streams of overflowing suspended load and bed load in the presence of salt water as the concentrations of suspended load in the freshwater are normally much less than required to overcome the density of the salt water deposition occurs throughout the fjord by rapid settling of flocculated particles from the overflowing brackish water and from grain flows in the proximal environment created as the fluvial traction carpet moves over the delta foreset slope after sediment has been deposited it may be remobilized by slides which in turn may develop into fully turbulent flows as they move down the fjord floor a range of deposits from slump debris to minor turbidites are postulated to occur with the flocculated muds although not all have yet been examined in the arctic fjord stratigraphic record sea ice is an important sedimentological agent in arctic fjords it passively carries fluvial aeolian and colluvial material which is subsequently released from the ice during the stage of puddle draining at break up sea ice also actively incorporates fine and coarse sediments up to large boulders during freezing along the shores in winter and by wave and tidal current washing controlled by the presence of the ice during break up

coastal southern ocean a strong anthropogenic co2 sink 1 large scale estimates of the southern ocean co2 sink do not adequately resolve the fluxes associated with antarctic continental shelves using a mechanistic three dimensional biogeochemical model of the ross sea we show that antarctic shelf waters are a strong sink for co2 due to high biological productivity intense winds high ventilation rates and extensive winter sea ice cover net primary production npp in these waters is 0 055 pg c yr 1 some of this carbon sinks to depth driving an influx of co2 of 20 50 g c m 2 yr 1 although currently unaccounted for the total atmospheric co2 sink on the ross sea continental shelf of 0 013 pg c yr 1 is equivalent to 27 of the most recent estimate of the co2 sink for the entire southern ocean given these results these and other highly productive waters around the antarctic continent need to be included in future budgets of anthropogenic co2

contrasts between debris flows hyperconcentrated flows and stream flows at a channel of mount semeru east java indonesia abstract in order to differentiate between different types of sediment laden flows in volcanic channels we carried out observation of debris flows hyperconcentrated flows and stream flows in the curah lengkong river on the southeast slope of mount semeru in east java indonesia the aims of this study are 1 to provide quantitative data for these flows in motion 2 to compare the data for different types of flow that occur in the same river 3 to assess the influence of rainfall on debris flows hyperconcentrated flows and streamflow generation the curah lengkong river transports large volumes of sediment in the range of 1 10 5 to 5 10 5 m 3 per debris flow and 10 3 to 10 5 m 3 per hyperconcentrated flow and stream flow large sediment discharges result from the following factors continuous and voluminous sediment supply of fine juvenile material by daily explosions of the semeru volcano pyroclastic source material emplaced on steep slopes strong erosion of weathered river banks and strong rainfall intensities the occurrence of the flows focuses in the period from november through april and the daily timing of it is the mid to late afternoon nearly all debris flows are triggered by stationary rainfall confined to the upper slopes of mount semeru whereas hyperconcentrated flows and stream flows are mainly generated by migratory or regional rains driven upwards on the eastern slope this slope receives its maximum of annual rainfall 3800 mm at 800 m asl the peak surface velocity of debris flows is always greater than the peak frontal velocity the peak discharge of debris flows occurs several minutes after the passage of the flow front volumetric concentrations of sediment are high 48 to 69 between the debris flow front and the point of peak discharge after the peak discharge it usually decreases gradually contrary to the case of debris flows high concentration of sediment appears in various portion of hyperconcentrated flows and stream flows near the front in the mid point or at the back of flows although the concentration of sediments in them is much less than in of debris flows relationships between sediment discharge total volume and peak discharge show a very strong positive correlation for debris flows and hyperconcentrated flows therefore sediment discharge can be roughly estimated from direct visual observation

sedimentologic characteristics of a fluvial to aeolian succession in weichselian talsand in the emsland f r g abstract a sedimentologic study of a fluvial to aeolian succession in weichselian talsand in the emsland f r g is presented here from bottom to top two fluviatile units an aeolian bed an aeolian lacustrine unit and a second windborne deposit succeed each other in the investigated exposure the aeolian facies represent two distinct styles of deposition by wind the lower aeolian unit with horizontal alternating bedding presumably results from both a periodic change in mean surface wind strength and the spring thawing of seasonally frozen ground the emerged part of the north sea basin was the principle source of sand and silt for this sediment type the upper aeolian unit is characterised by a low dune or sand sheet topography inclined bedding and the predominance of plane bed lamination it was laid down on depositional surfaces normally too dry for the formation of adhesion stratification surface wind speed was generally high and its distribution over the year had become more uniform than before furthermore sand supply was increasingly from local sources close to the depositional site the deposition of the aeolian lacustrine unit is due to lateral migration of the low dunes mentioned above during this process sand was blown into a pool of still water and then subjected to gravitational slumping the change from fluvial to aeolian depositional regime observable in the talsand is tentatively attributed to the combined effect of intensified wind activity and lowering of the groundwater table as a result of permafrost degradation

niveo aeolian deposits and denivation forms with special reference to the great kobuk sand dunes northwestern alaska the geomorphology lithology and chronostratigraphy of extensive late pleistocene inland and river dune sands aeolian sand sheets cover sands and loess deposits of periglacial origin in northwestern europe are well known however the idea that some of these aeolian sediments result from niveo aeolian processes is still an open question as no diagnostic sedimentary features have yet been reported moreover actual niveo aeolian sediments and related denivation forms reported from various cold climate regions are not suitable analogues recent observations in active dune fields in northwestern alaska indicate that interstratification of wind driven snow and sand preferentially occurs on slip faces of transverse barchanoid or parabolic dune ridges annual denivation forms develop e g snow ramparts sinkholes snow hummocks snow meltwater fans and tensional cracks the surface consists of a cracked wet sand layer with a dimpled surface and spongy structure although the preservation potential of these features is low in this specific case similar features may be observed in ancient sediments elsewhere and provide useful palaeoclimatic indicators the niveo aeolian concept should therefore not specifically be related to late pleistocene cover sand deposition in northwestern europe as previously assumed

fluvial sediment transport and deposition following the 1991 eruption of mount pinatubo the 1991 eruption of mount pinatubo generated extreme sediment yields from watersheds heavily impacted by pyroclastic flows bedload sampling in the pasig potrero river one of the most heavily impacted rivers revealed negligible critical shear stress and very high transport rates that reflected an essentially unlimited sediment supply and the enhanced mobility of particles moving over a smooth fine grained bed dimensionless bedload transport rates in the pasig potrero river differed substantially from those previously reported for rivers in temperate regions for the same dimensionless shear stress but were similar to rates identified in rivers on other volcanoes and ephemeral streams in arid environments the similarity between volcanically disturbed and arid rivers appears to arise from the lack of an armored bed surface due to very high relative sediment supply in arid rivers this is attributed to a flashy hydrograph whereas volcanically disturbed rivers lack armoring due to sustained high rates of sediment delivery this work suggests that the increases in sediment supply accompanying massive disturbance induce morphologic and hydrologic changes that temporarily enhance transport efficiency until the watershed recovers and sediment supply is reduced d 2002 elsevier science b v all rights reserved

some thermoluminescence properties and dating of eolian sands from the netherlands abstract bleaching characteristics of late glacial and holocene eolian sands from the netherlands confirm the suitability for tl dating of these sediments a solar simulator has been used for both quartz and potassium feldspar separates a number of bleaching times and dose rate determinations have been used to establish the best plateau for the ed determination and a suitable dose rate respectively in order to date a late glacial cover sand sample

sediment transportation and deposition by rain triggered lahars at merapi volcano central java indonesia abstract a lahar is a general term for a rapidly flowing mixture of rock debris and water other than normal streamflow from a volcano and refers to the moving flow located in the populated area of central java the stratovolcano merapi 2965 m is prone to lahar generation due to three main factors 1 millions of cubic meters of pyroclastic deposits are the product of frequent pyroclastic flows which have occurred on 2 to 4 year intervals 2 rainfall intensity is high often 40 mm in 2 h on average during the rainy season from november to april and 3 drainage pattern is very dense following the 22 november 1994 eruption of merapi 31 rain triggered lahar events were recorded in the boyong river between december 1994 and may 1996 on merapi s slopes instantaneous sediment concentration at any given time of the lahars varies widely over time and space lahars are transient sediment water flows whose properties are unsteady so that the sediment load fluctuates during the flow the boundary between the flow types debris flow with sediment concentration 60 volume or hyperconcentrated flow with sediment concentration ranges from 20 to 60 volume may fluctuate within the flow itself grain size distribution physical composition of sediments shear stress yield stress and water temperature play each a role on this boundary natural self damming and rapid breakout are partly responsible for the sediment variations of the flows debris flow phases at merapi typically last a few minutes to 10 min and are often restricted to the lahar front debris flow surges are sometimes preceded and always followed by longer hyperconcentrated flow phases as a result mean sediment concentration of the lahars is low commonly from 20 to 50 volume besides transient normal streamflow phases sediment concentration low sediment load and frequent transient flows in the merapi channels may result from at least three factors 1 several breaks in slope along the channel increase the deposition rate of sediment and hinder the bulking capacity of the lahars 2 source material is mainly coarse debris of merapi type block and ash flows consequently the remobilization of coarse debris is more difficult and the clast deposition is accelerated 3 variations of rainfall intensity over time and space common in tropical monsoon rainfall also influence the sediment load variations of the lahars sedimentologic analyses of the lahar deposits in the boyong river at merapi encompass clast supported and matrix supported debris flow deposits hyperconcentrated flow deposits and streamflow deposits the stratigraphic succession of massive and stratified beds observed immediately after any given lahar event in the boyong river indicates that the sediment concentration varies widely over time and space during a single lahar event sedimentation rate varies from 3 to 4 5 cm min during relatively long lived surges to as much as 20 cm min during short lived surges these results indicate that the sediment load fluctuates during lahar flow further demonstrating that lahars are transient sediment water flows with unsteady flow properties

a pleistocene sand sea on the alaskan arctic coastal plain a ridge and thermokarst basin landscape that is strikingly portrayed in landsat winter imagery consists of large pleistocene dunes that have been modified by younger eolian activity and thermokarst processes this is the most extensive area of large stabilized dunes yet reported in the north american arctic the landscape is of particular interest because it has been proposed as a first order analog for martian fretted terrain recognition of the large dunes permits a new interpretation for linear and curvilinear trends visible in landsat summer imagery

the late glacial pedogenesis interrupted by aeolian activity in central poland records from the lake gościąz catchment abstract an interdisciplinary study was undertaken to reconstruct the late glacial fluvioglacial and aeolian sediment transformations with a particular focus on soil forming processes the studies included complex pedological research physical and chemical properties x ray diffraction xrd analysis of clay minerals and optically stimulated luminescence osl dating on soil deposit sequences developed within the aeolian landscape of inland dunes in the lake go ci z catchment central poland late glacial buried bwb soil horizons are known as finow soils this paleosol was identified in the central part of inland dunes in vertical perspective developed from aeolian material deposited on fluvioglacial sediments the average content of silt and clay in this paleosols ranged from 7 3 to 41 1 and from 6 7 to 12 6 respectively in other soil horizons within profiles the average content of these granulometric fractions was about 3 and 1 5 respectively the dominance of dioctahedral vermiculite and the higher content of free iron oxides especially oxalate form and aluminium within bwb horizons indicates their pedogenic origin the osl dates suggested that finow soil fossilization began along with the development of aeolian processes in the late glacial cold periods the older dryas and the younger dryas while finow soil development took place in the warmer periods of the late glacial bolling allerod these results were consistent with data from germany other stands in northern poland and the tomsk priobye region se western siberia

downstream dilution of a lahar transition from debris flow to hyperconcentrated streamflow nearly instantaneous melting of snow and ice by the march 19 1982 eruption of mount st helens released a 4 106 m3 flood of water from the crater that was converted to a lahar volcanic debris flow through erosion and incorporation of sediment by the time it reached the base of the volcano over the next 81 km that it traveled down the toutle river the flood wave was progressively diluted through several mechanisms a transformation from debris flow to hyperconcentrated streamflow began to occur about 27 km downstream from the crater when the total sediment concentration had decreased to about 78 by weight 57 by volume the hyperconcentrated lahar runout flood wave transporting immense quantities of sand in suspension continued to experience progressive downstream dilution although turbulence was significantly dampened by the extremely high suspended load very large standing waves and antidune waves were observed the hyperconcentrated lahar runout flow deposited an unusual faintly stratified coarse sand which locally contained small isolated gravel lenses very similar deposits in the quaternary stratigraphy of mount st helens and other cascades volcanoes suggest that lahars may be more frequent than previously recognized

geology tectonics and the 2002 2003 eruption of the semeru volcano indonesia interpreted from high spatial resolution satellite imagery abstract the paper illustrates the application of high spatial resolution satellite images in interpreting volcanic structures and eruption impacts in the tengger semeru massif in east java indonesia we use high spatial resolution images ikonos and spot 5 and aerial photos in order to analyze the structures of semeru volcano and map the deposits geological and tectonic mapping is based on two dems and on the interpretation of aerial photos and four spot and ikonos optical satellite images acquired between 1996 and 2002 we also compared two thermal surface kinetic temperature aster images before and after the 2002 2003 eruption in order to delineate and evaluate the impacts of the pyroclastic density currents semeru s principal structural features are probably due to the tectonic setting of the volcano a structural map of the tengger semeru massif shows four groups of faults orientated n40 n160 n75 and n105 to n140 conspicuous structures such as the se trending horseshoe shaped scar on semeru s summit cone coincide with the n160 trending faults the direction of minor scars on the east flank parallels the first and second groups of faults the semeru composite cone hosts the currently active jonggring seloko vent this is located on and buttressed against the mahameru edifice at the head of a large scar that may reflect a failure plane at shallow depth dipping 35 towards the se this failure plane may correspond to a weak basal layer of weathered volcaniclastic rocks of tertiary age we suggest that the deformation pattern of semeru and its large scar may be induced by flank spreading over the weak basal layer of the volcano it is therefore necessary to consider the potential for flank and summit collapse in the future the last major eruption took place in december 2002 january 2003 and involved emplacement of block and ash flows we have used the 2003 aster surface kinetic temperature image to map the 2002 2003 pyroclastic density current deposits we have also compared two 10 m pixel images acquired before and after the event to describe the extent and impact of an estimated volume of 5 45 106 m3 of block and ash flow deposits an ash rich pyroclastic surge escaped from one of the valley confined block and ash flows at 5 to 8 km distance from the crater and swept across the forest and tilled land on the sw side of the bang river valley downvalley the temperature of the pyroclastic surge decreased and a mud rich deposit coated the banks of the bang river valley thus hazard mitigation at semeru should combine 1 continuous monitoring of the eruptive activity through an early warning system and 2 continuous remote sensing of the morphological changes in the drainage system due to the impact of frequent pyroclastic density currents and lahars

pollen diagram from the nebraska sandhills and the age of the dunes abstract radiocarbon dates of organic alluvium beneath as much as 40 m of dune sand along the dismal river have led to the suggestion that the nebraska sandhills date from the holocene rather than the last glacial period on the other hand the basal layers of lake and marsh deposits in interdune depressions at three localities date in the range of 9000 to 12 000 yr b p implying a pre holocene age for the sand dunes a pollen diagram for one of these sites swan lake indicates prairie vegetation throughout the last 9000 yr with no suggestion that the landscape was barren enough to permit the shaping of the massive dunes characterizing the area sand was not transported across the site during the holocene either during the marsh phase which lasted until 3700 yr b p or during the subsequent lake phase the sand that buries the alluvium along the dismal river may represent only local eolian activity or it may indicate that the younger of the two main dune series identified by h t u smith 1965 journal of geology 73 557 578 is holocene in age and the older one late wisconsin in age

sediment yield following severe volcanic disturbance a two decade perspective from mount st helens explosive volcanic eruptions perturb water and sediment fluxes in watersheds consequently posteruption sediment yields can exceed preeruption yields by several orders of magnitude annual suspended sediment yields following the catastrophic 1980 mount st helens eruption were as much as 500 times greater than typical background level and they generally declined nonlinearly for more than a decade although sediment yields responded primarily to type and degree of disturbance streamflow fluctuations significantly affected sediment yield trends consecutive years 1995 1999 of above average discharge reversed the nonlinear decline and rejuvenated yields to average values measured within a few years of the eruption after 20 yr the average annual suspended sediment yield from the 1980 debris avalanche deposit remains 100 times 10 4 mg megagrams km 2 above typical background level 10 2 mg km 2 within five years of the eruption annual yields from valleys coated by lahar deposits roughly plateaued and average yields remain about 10 times 10 3 mg km 2 above background level yield from a basin devastated solely by a blast pyroclastic current diminished to background level within five years these data demonstrate longterm instability of eruption generated detritus and show that effective mitigation measures must remain functional for decades

the dominance of dispersion in the evolution of bed material waves in gravel bed rivers bed material waves are temporary zones of sediment accumulation created by large sediment inputs recent theoretical experimental and field studies examine factors influencing dispersion and translation of bed material waves in quasi uniform gravel bed channels exchanges of sediment between a channel and its floodplain are neglected within these constraints two factors influence relative rates of dispersion and translation 1 interactions between wave topography flow and bed load transport and 2 particle size differences between wave material and original bed material our results indicate that dispersion dominates the evolution of bed material waves in gravel bed channels significant translation requires a low froude number which is uncharacteristic of gravel bed channels and low wave amplitude which for a large wave can be achieved only after substantial dispersion wave material of small particle size can promote translation but it primarily increases bed load transport rate and thereby accelerates wave evolution copyright 2001 john wiley sons ltd

paleoenvironmental and geomorphic significance of bluff top dunes along the au sable river in northeastern lower michigan usa abstract we report on the age and evolution of five well developed parabolic dunes that are perched on high 40 m bluffs along the southern lip of the au sable river valley in northeastern lower michigan u s a these dunes are located on west northwest facing exposures and mantle the jackpines delta which formed when the glacial au sable river system deposited sands and gravels into glacial lake warren in the huron basin sometime between 15 1 and 14 7 ka lake level subsequently fell 35 m as the ice margin retreated northward during the twocreekan interstadial this regression resulted in abandonment of the jackpines delta and incision of the associated surface by the ancestral au sable river lake level subsequently rose 50 m during the algonquin transgression which likely promoted valley widening through channel migration eight samples were collected for osl age determination of the dunes and yielded ages that suggest dune formation occurred mostly between 13 5 ka and 13 ka this result coupled with the landscape position of the dunes i e south side of river west northwest facing bluffs suggests that the dunes largely formed 1 during the algonquin transgression when bluffs were eroded by stream channel migration and 2 by west northwesterly winds that transported eolian sands from exposed bluff faces to the adjacent valley edge this study contributes to the understanding of perched dune formation in the great lakes region and further supports models indicating that westerly winds prevailed within 150 km of the ice margin during the late pleistocene it also demonstrates that interior dunes in this region formed in similar environmental settings to interior dunes in northern europe and suggests that local factors rather than specific climate intervals should also be considered as they relate to dune evolution

eolian sand and loess deposits indicate west northwest paleowinds during the late pleistocene in western wisconsin usa our study adds to the quaternary history of eolian systems and deposits in western wisconsin usa primarily within the lower chippewa river valley thickness and textural patterns of loess deposits in the region indicate transport by west northwesterly and westerly winds loess is thickest and coarsest on the southeastern flanks of large bedrock ridges and uplands similar in some ways to shadow dunes in many areas sand was transported up and onto the western flanks of bedrock ridges as sand ramps presumably as loess was deposited in their lee long linear dunes common on the sandy lowlands of the chippewa valley also trend to the east southeast small depressional blowouts are widespread here as well and often lie immediately upwind of small parabolic dunes finally in areas where sediment was being exposed by erosion along cutbanks of the chippewa river sand appears to have been transported up and onto the terrace treads forming cliff top dunes luminescence data indicate that this activity has continued throughout the latest pleistocene and into the mid holocene together these landforms and sediments paint a picture of a locally destabilized landscape with widespread eolian activity throughout much of the postglacial period

tracing the evolution of 2010 merapi volcanic deposits indonesia based on object oriented classification and analysis of multi temporal very high resolution images abstract we compare identification delineation and recording of freshly erupted deposits around active volcanoes from very high resolution optical images with that done by traditional geologic mapping object oriented classification ooc and normalized difference spectral indices of vegetation moisture and soil redness ndvi ndwi and ndrsi have been applied to sub metric geoeye 1 and pleiades images to identify and map pyroclastic and lahar deposits and trace their spatio temporal evolution over two years following the 2010 eruption of merapi volcano indonesia we could identify several categories of pyroclastic depositional areas and also map the damaged forest and destroyed cultivated terraces and settlements in the gendol and opak river basins on the south flank of the volcano more than 75 of erupted deposits were delineated semi automatically unlike the ground geological map based on photo interpretation of the 2010 geoeye image and field observations a temporal image analysis using bivariate scatter diagrams of the three spectral indices between 2010 and 2012 and a combination of ndwi and ndvi separated areas affected by surges from unscathed vegetation use of ndrsi and ndwi allowed us to differentiate overbank pyroclastic density current deposits from wet lahar deposits ndrsi values close to 0 refer to scoria rich pyroclastic deposits about 40 of the devastated upper catchment was recolonized by vegetation between 2010 and 2012 the recovery also took place in the forested valley margins affected by ash cloud surges the morphometric analysis of the initial drainage network digitized from the 2011 2012 images demonstrated 1 the resurfacing of pristine 2010 pdc deposits by runoff and 2 incision or remobilization by lahars it took two years following the eruption in the rugged upper catchment devastated by high energy surges to fully develop the hydrographic network it is however still rudimentary on gently sloping fans created by overbank pdc deposits in the middle valley thus suggesting the importance of slope gradient grain size permeability and thickness of deposits as much as 35 of the 2010 pdc deposits emplaced in the vicinity of the river channels were remobilized by lahars over the two post eruption rainy seasons and also by constant mining activities studies on the erosion of the pyroclastic deposits after 2012 need to concentrate on the upper reach of the catchment on the south flank

the threat of hazards in the semeru volcano region ineast java indonesia abstract semeru volcano 3676 m the highest volcano in java is one of the most active volcanoes in indonesia its activity has occurred almost continuously since 1967 the activity is manifested by mostly strombolian type eruptions with lava extrusions which extend into a lava tongue in kobokan breach southeast slope of the volcano the lava tongue is unstable after reaching a certain volume the tongue collapses and causes pyroclastic flows to the southeast direction traveling a maximum of about 11 km downslope the collapse is sometimes triggered by volcanic eruptions the main dangers are not due to eruption and collapse of the lava tongue but caused by the secondary dangers the secondary dangers are more destructive and distributed over a wider area tens of kilometres from the source the natural hazards in the semeru region are not only related to volcanic activity which is so called lahar but also non volcanic processes such as debris flow this phenomenon is related to the heavy rainfall which causes landslides in the altered volcanic deposit areas the flow of the mixture of water and landslide materials has devastated large areas the occurrences of the secondary flow is unpredictable and its viscosity is much lower than lahar this flow is distributed over a wide area and threatens cultivated land and densely populated and developing urban areas

growth and erosion rates of the east carpathians volcanoes constrained by numerical models tectonic and climatic implications abstract the east carpathian volcanic range experienced an along arc late miocene to quaternary migration of eruptive activity during its 11 ma long activity here a novel and complex methodology is presented that yields new geochronological and geomorphological constraints on the evolution of the 20 volcanic edifices new unspiked k ar ages either constrain their lifespan 6 79 0 10 6 47 0 09 ma for seaca t tarca 5 47 0 08 4 61 0 07 ma for v rghis or date the youngest volcanic activity central c limani in parallel numerical reconstructions of volcanic paleo topographies were performed to quantify their shape at the end of their construction stage the inferred initial volcano size shows a wide range 3 to 592 km3 making up the four main successive volcanic segments 910 880 279 and 165 km3 for c limani gurghiu north harghita and south harghita segment respectively totalizing 2200 km3 and an average growth rate of 200 km3 ma at range scale at the volcano scale with only consideration to their respective time spans i e avoiding repose periods growth rate is characterized by two major trends a moderate growth rate 137 km3 ma for the older volcanoes 11 3 6 ma followed by a lower growth rate 28 km3 ma obtained for the plio quaternary volcanoes comparing reconstructed and current topographies yielded a total eroded volume of 524 125 km3 defining averaged denudation of 22 and a 20 m ma erosion rate erosion rates for major climatic periods were computed which highlight the contrasting climatic contexts since 11 ma the highest erosion rate 38 m ma occurred during transitional moderate subtropical continental climate period 9 5 8 2 ma an intermediate erosion rate 14 m ma characterized a moderate continental climate period 8 2 6 8 ma when conditions became less humid the lowest erosion rate 7 m ma reflects the prevailing continental but occasionally semi arid climate 6 8 5 8 ma the highest erosion rate 28 m ma was obtained for plio quaternary times during the interglacial glacial cycles such a quantitative morphometric and geochronological approach demonstrates its efficiency to study volcanic dynamism including both constructional and erosional processes through time

channel bed mobility response to extreme sediment loading at mount pinatubo since the 1991 eruption of mount pinatubo the specific sediment yields from watersheds draining its slopes have been the highest ever recorded in spite of this overwhelming sediment load rivers inundated by pyroclastic flow deposits delivered almost half of the initial deposits to downslope alluvial and or debris fans by 1996 although most of this transport occurred by hyperconcentrated flows and debris flows lahars very high sediment transport rates also characterize low flow measured flow velocities and depths channel properties and the size of both mobile and stable clasts in the sacobia and pasig potrero rivers indicate median bed surface grain sizes of 2 to 8 mm grain size independent dimensionless critical shear stresses c of 0 016 to 0 041 and manning s n values of 0 017 to 0 024 values well below those previously reported for steep mountain channels the dramatic bed surface fining bed mobility and selective transport in these extremely sediment rich channels indicate that changes in grain size c values and bed roughness can increase transport capacity in response to high sediment supply our observations also suggest viewing the apparently contradictory concepts of an equal threshold of bed mobility and grain size dependent selective transport as end member concepts that apply to channels with low or intermittent and high or continuous sediment supply respectively

spatial distribution of pco2 δo2 ar and dimethylsulfide dms in polynya waters and the sea ice zone of the amundsen sea antarctica we report the first simultaneous measurements of surface water pco2 biological oxygen saturation o2 ar and dimethylsulfide dms concentrations in polynya waters and the sea ice zone of the amundsen sea antarctica across our survey region we observed large spatial variability in surface water gas concentrations tied to strong gradients in hydrography and phytoplankton biomass variability in sea surface temperature and salinity was attributed to the interacting effects of surface ocean circulation and heat fluxes sea ice melt and the upwelling of relatively warm saline and nutrient rich modified circumpolar deep water phytoplankton biomass ranged from 1 g l 1 to 40 g l 1 chlorophyll a chl a with the highest values observed in regions of shallow mixed layer depths phytoplankton assemblages were dominated by the colonial haptophyte phaeocystis antarctica at most sampling stations with lesser abundances of diatoms found throughout the polynya and sea ice zone cryptophytes were abundant at a few stations along the continental shelf break across the open polynya waters and sea ice zone o2 ar ranged from 40 to 40 mean 8 6 pco2 ranged from 80 to 530 atm mean 250 atm and dms concentrations varied from 1 nm to 350 nm strong gradients in gas concentrations were observed over short i e 10 km spatial scales the distribution of pco2 and o2 ar across our survey transects reflected the balance between deep water entrainment and net community production with a significant imprint of air sea exchange chl a concentrations were significantly correlated to both pco2 and o2 ar and the slope of the o2 ar vs pco2 relationship was consistent with photosynthetic stoichiometry 1 25 mol o2 evolved per mol dic removed dms and chl a concentrations were also correlated in surface waters but the spatial distribution of dms was often uncoupled from pco2 and o2 ar likely due to complex microbial cycling processes sea surface temperature and salinity were related to surface gas concentrations through their effects on mixed layer depth and as tracers of upwelling during the time of our cruise the amundsen sea acted as an overall net sink for co2 mean sea air flux 15 9 mmol m 2 d 1 and a dms source mean sea air flux 23 1 mol m 2 d 1 sea air co2 and dms fluxes were more than 2 fold higher in open polynya waters relative to the overall cruise means simple calculations suggest that the amundsen sea contributes 5 of total southern ocean co2 fluxes and 1 of dms fluxes

comparison of quartz osl protocols using lateglacial and holocene dune sands from brandenburg germany abstract we present the results obtained using various different protocols in the quartz optically stimulated luminescence dating of a late glacial and holocene aeolian dune sequence near eberswalde north of berlin germany the allerod finow palaeosol and the laacher see tephra layer serve as chronostratigraphic markers and further independent age control is provided by eight 14 c ages the application of the single aliquot regenerative dose protocol using blue light stimulation and the multiple aliquot regenerative dose and additive dose protocols using broad band blue and green light stimulation are discussed a comparison of radionuclide analyses using high resolution gamma spectrometry and neutron activation analysis is also presented it is concluded that the two dosimetry methods give indistinguishable results although the gamma spectrometry data are more precise in contrast the single aliquot regenerative dose protocol is between 2 and 10 times more precise than the multiple aliquot protocols and systematic differences in performance are also observed the uncertainties in the dosimetry calculations are the largest contributor to the overall age uncertainties the accuracy of the resulting ages is considered very satisfactory when tested against the independent age controls over the entire age range from the present to 15 ka

iron from melting glaciers fuels the phytoplankton blooms in amundsen sea southern ocean iron biogeochemistry dissolved iron dfe and total dissolvable fe tdfe were measured in january february 2009 in pine island bay as well as in the pine island and amundsen polynyas amundsen sea southern ocean iron fe has been shown to be a limiting nutrient for phytoplankton growth even in the productive continental shelves surrounding the antarctic continent however the polynyas of the amundsen sea harbor the highest concentrations of phytoplankton anywhere in antarctica here we present data showing the likely sources of fe that enable such a productive and long lasting phytoplankton bloom circumpolar deep water cdw flows over the bottom of the shelf into the pine island bay where dfe and tdfe were observed to increase from 0 2 to 0 4 nm dfe and from 0 3 4 0 to 7 14 nm tdfe respectively at the southern end of pine island bay the cdw upwelled under the pine island glacier bringing nutrients including fe to the surface and melting the base of the glacier concentrations of dfe in waters near the pine island glacier and the more westward lying crosson dotson and getz ice shelves varied between 0 40 and 1 31 nm depending on the relative magnitude of upwelling turbulent mixing and melting these values represent maximum concentrations since associated ligands which

characterization of debris flows by rainstorm condition at a torrent on the mount yakedake volcano japan abstract we analyzed rainstorm control on debris flow magnitude and flow characteristics using the 14 sets of rainstorm and debris flow data obtained from 1980 to 2005 at the kamikamihorizawa creek of mount yakedake with the principal component analysis on five parameters of debris flows frontal velocity peak velocity peak flow depth peak discharge and total discharge and with video record of boulder dams in motion and the preceding rainfall intensities we conclude that the 14 debris flows could be categorized into three groups the flows in the first group have large hydraulic magnitude and massive and turbulent boulder dams filled with slurry matrix the flows in the second group have small hydraulic magnitude and boulder dams scarcely filled with slurry matrix and the dam is observed to alternate between stopping and starting the flows in the third group have small hydraulic magnitude and boulder dams filled with slurry matrix analysis of hillslope hydrology and debris flow data asserted that the antecedent rainfall conditions control not only the hydraulic magnitude of debris flows but also the boulder dam features large rainstorms of high intensity and durations as short as 10 minutes induces fast and large storm runoff to the headwaters and the source reaches of debris flow while rainstorms with durations as long as 24 h raises water content in the bottom deposits along the debris flow growth reaches and generates substantial runoff from the tributaries classification of the three groups is done based on water availability to debris flows on the source and growth reaches at the occurrence of debris flow

a revised chronology for aeolian activity in subarctic fennoscandia during the holocene detailed sedimentological studies and parallel sampling for 14c and infra red stimulated luminescence age assays were undertaken at six sites lying beyond and below the tree line with the objective of establishing the historical development of aeolian landforms in lapland the main issues were a the timing of dune activity and processes of stabilization b the specific processes responsible for the past and contemporary activity new data indicate that many of the primary dunes were active for several millennia after deglaciation diachronous stabilization at both local and regional scales appears likely initial stabilization occurred in local interdune areas and where regional dune fields were colonized by pine generally before 7 ka local large dunes and some regional dunefields only became stable around 4 3 ka when the regional groundwater table rose and late pine colonization was possible the latest episode of aeolian activity dates from ad 1100 1650 across the area a unique deflation trigg

coastal aeolian dune development solheimasandur southern iceland abstract a coastal aeolian dune field on the distal parts of solheimasandur southern iceland is currently undergoing active construction ongoing sand deflation in the foreshore is demonstrated by the preservation of sand ridges in the downwind lee of obstacles while a backshore sandsheet is characterised by actively accumulating long wavelength wind ripples the main region of aeolian accumulation is in the immediate backshore where sand has accumulated to a thickness of up to 8 m and is largely stabilized by vegetation surrounding interdune areas have undergone repeated flooding by fluvial incursions from the adjacent jokulsa river and are characterised by mud drapes which lap against the lower flanks of neighbouring dunes widespread sand adhesion structures testify to the often damp nature of the substrate over 1200 vegetated and stabilized dunes nebkhas occupy a 5 km 2 area of wind deflated gravel sandur plain downwind from the main site of aeolian accumulation the nebkhas show strong relationships between plan form shape and height indicating that they have attained equilibrium morphology for the prevailing climatic conditions within the nebkha field dunes demonstrate a predictable downwind decrease in height spatial concentration and degree of sand stabilization a time series of aerial photographs documents the temporal evolution of the dune field and demonstrates that aeolian accumulation commenced about 1940 and has been ongoing to the present day prior to 1940 repeated outburst floods associated with catastrophic lake drainage events from the solheimajokull glacier 8 km inland were of sufficient magnitude to repeatedly destroy any incipient aeolian bedforms that developed although strong onshore winds and high rates of sediment supply promote aeolian sediment transport dune field development is rare in humid boreal and sub arctic climates as encountered in southern iceland because the availability of sediment for aeolian transport is usually severely limited by damp substrate conditions thus the airflow tends to be undersaturated with respect to its potential sand transporting capacity and dune construction can only occur because of the stabilizing influence of vegetation

environmental impact of the 1 8 ka taupo eruption new zealand landscape responses to a large scale explosive rhyolite eruption abstract large scale ignimbrite eruptions from rhyolitic caldera volcanoes can trigger geologically instantaneous changes in sedimentary systems over huge areas by either burying existing environments or overloading them with vast quantities of unconsolidated particulate material the post eruption readjustment of the landscape to such perturbations is one of the most dramatic processes in physical sedimentology exemplified here by the 1 8 ka taupo eruption in the central north island of new zealand this eruption generated voluminous fall deposits then climaxed with emplacement of a c 30 km 3 non welded ignimbrite over a near circular area of c 20 000 km 2 approximately 90 of the area but the headwaters of many of the north island s largest rivers were impacted by both the primary pyroclastic fall and flow material large scale post eruption remobilisation of this material coupled with the re establishment of fluvial systems occurred in a distinct sequence as recorded by the evolution of sedimentary facies in different sub environments following an initial period dominated by mass flows re establishment of fluvial systems began with the headward erosion of box canyons through the ponded ignimbrite deposits a process often associated with the break out of temporary lakes aggradational streams developed in these channels rapidly evolved from shallow ephemeral sediment laden outbursts associated with flash flood events to deeper permanent braided rivers before declining sediment yields led to retrenchment of single thread rivers and a return to pre eruption gradients and bedloads years to decades later typically the modern profile of many streams and rivers follow closely their pre eruption profiles and incision and erosion is overwhelmingly confined to the deposits of the eruption itself although the general remobilisation pattern is similar for all impacted river systems detailed studies of the waikato rangitaiki mohaka ngaruroro and whanganui catchments show that the relative timing and scale of each eruption response phase differs between each catchment these reflect differences in catchment physiography and hydrology and the volume and type of pyroclastic material deposited in each ultimately the landscape response reflects the relative spatial distributions of and the volumetric ratios between the volumes of pyroclastic debris water and accommodation space in the basin cf kataoka and manville this volume

the coalescence and organization of lahars at semeru volcano indonesia we present multi parameter geophysical measurements of rainfall induced lahars at semeru volcano east java using two observation sites 510 m apart 11 5 km from the summit our study site in the curah lengkong channel is composed of a 30 m wide box valley with a base of gravel and lava bedrock representing an ideal geometry for high density measurements of active lahars instrumentation included pore pressure sensors stage a broad band seismograph arrival times vibrational energy and turbulence video footage and direct bucket sampling a total of 8 rainfall induced lahars were recorded with durations of 1 3 h heights 0 5 2 m and peak velocities 3 6 m s flow types ranged from dilute to dense hyperconcentrated flows these recorded flows were commonly composed of partly coalesced discrete and unsteady gravity current packets represented by multiple peaks within each lahar these packets most likely originate from multiple lahar sources and can be traced between instrument sites those with the highest concentrations and greatest wetted areas were often located mid lahar at our measured reach accelerating towards the flow front as these lahars travel downstream the individual packets thus coalesce and the flow develops a more organised structure observations of different degrees of coalescence between these discrete flow packets illustrate that a single mature debris flow may have formed from multiple dynamically independent lahars each with different origins

defining conditions for bulking and debulking in lahars through measurements at semeru volcano east java we define the conditions under which bulking entrainment of sediment and pore water and debulking dilution and sedimentation occur in rain triggered volcanic floods lahars two observation sites were installed 510 m apart along the curah lengkong river 11 5 km southeast of semeru s summit this 30 m wide box valley with a gravel and lava base represents a real world flume analogy pore pressure sensors provided stage measurements a broad band seismograph gave insight into sediment content and frictional collisional behavior video cameras were used to measure surface velocities and direct bucket samples were taken eight rainfall induced lahars were recorded lasting 1 3 h with heights of 0 5 2 m peak velocities of 3 7 m s and discharges of 25 250 m3 s flows ranged from typical 40 wt sediment to coarse and dense hyperconcentrated flows 50 60 wt sediment multiple distinct flow packets occurred within the complex lahars and were used to determine internal changes between sites from the multiparameter data set at each site volumetric bulking and wave shortening due to portions of the lahar accelerating toward the flow front are identified initial debulking of lahars between sites may reflect drainage into the dry substrate estimates of discharge and volume at each site lead to the quantification of bulking and debulking by these actively flowing lahars along the channel reach from this we observe that bulking can be localized to certain parts of lahars resulting in intraevent increases in peak discharge that are greater than what would occur if bulking was evenly distributed throughout the flow such data are essential for the development of numerical descriptions and hazard models for mass flows

eolian deflation by ancient katabatic winds a late quaternary example from the north alaska range strong katabatic winds are frequently generated in glaciated mountain valleys of the alaska range by downglacier gravitational flow of chilled air stronger katabatic winds probably occurred during late quaternary time when glaciers were more extensive and such winds may have greatly influenced eolian sedimentation in nenana river valley and in most of adjacent teklanika river valley the entire 1 to 2 m thick eolian cap is postglacial in age and the beginning of loess deposition coincides almost exactly with rapid recession of late wisconsin ice previously deposited loess and bluff edge dunes were apparently deflated during the last glaciation between 25 000 and 12 000 yr b p loess deposition in these mountain valleys thus is exclusively an interglacial phenomenon glacial phases are characterized by deflation meteorological modeling of katabatic winds generated during the last glaciation predicts that paleowind velocities greatly exceeded the entrainment thresholds required for eolian deflation when both nenana river and teklanika river valleys are compared theoretical differences in the potential for generating katabatic winds and differences in valley physiography explain why pre holocene loess is preserved in downstream reaches of teklanika river valley and not nenana river valley the presence of strong katabatic winds in mountain valleys beyond former glacier limits has significant implications for late pleistocene paleoecology and archeology

ice melt influence on summertime net community production along the western antarctic peninsula the western antarctic peninsula wap is a highly productive marine environment that is undergoing rapid change with consequences for productivity and total ecosystem carbon cycling we present continuous underway o2 ar estimates of net community production ncpo2ar in austral summer 2012 2013 and 2014 at sub kilometer horizontal resolution within the palmer long term ecological research pal lter grid region of the wap substantial spatial variability is observed with ncpo2ar ranging from 0 to 790 mmol o2 m 2 d 1 and considerable interannual variability with mean values in the grid region of 54 4 48 5 44 6 40 5 and 85 6 75 9 mmol o2 m 2 d 1 in 2012 2013 and 2014 respectively based on a strong correlation r2 0 83 between residence time integrated ncpo2ar and ncpdic derived from seasonal dic drawdown we find the observed ncpo2ar spatial and interannual variability to be consistent with the december january ncpdic magnitude seeking to explain the mechanistic drivers of ncp in the wap we observe a linear relationship between ncpo2ar and meteoric water content derived from 18o and salinity this correlation may be due to fe supply from glacial melt and or strengthening of stratification and relief of light limitation elevated surface fe availability as indicated by fv fm and measurements of surface water dissolved fe and mn a rough proxy for recent potential fe availability and shallower more stable mixed layers are present where meteoric water and or sea ice melt is high near the coast light limitation is evident in the wap when mixed layer depths are greater than 40 m additionally we document hotspots of ncp associated with submarine canyons along the wap while it is difficult to predict how the physical biological system might evolve under changing climatic conditions it is evident that ncp and potentially carbon flux out of the mixed layer along the wap will be sensitive to shifts in meltwater input and timing

volcanic hazards at mount semeru east java indonesia with emphasis on lahars mt semeru the highest mountain in java 3 676 m is one of the few persistently active composite volcanoes on earth with a plain supporting about 1 million people we present the geology of the edifice review its historical eruptive activity and assess hazards posed by the current activity highlighting the lahar threat the composite andesite cone of semeru results from the growth of two edifices the mahameru old semeru and the seloko young semeru on the se flank of the summit cone a n130 trending scar branched on the active jonggring seloko vent is the current pathway for rockslides and pyroclastic flows produced by dome growth the eruptive activity recorded since 1818 shows three styles 1 the persistent vulcanian and phreatomagmatic regime consists of short lived eruption columns several times a day 2 increase in activity every 5 to 7 years produces several kilometer high eruption columns ballistic bombs and thick tephra fall around the vent and ash fall 40 km downwind dome extrusion in the vent and subsequent collapses produce block and ash flows that travel toward the se as far as 11 km from the summit and 3 flank lava flows erupted on the lower se and e flanks in 1895 and in 1941 1942 pyroclastic flows recur every 5 years on average while large scale lahars exceeding 5 million m3 each have occurred at least five times since 1884 lumajang a city home to 85 000 people located 35 km e of the summit was devastated by lahars in 1909 in 2000 the catchment of the curah lengkong river on the ese flank shows an annual sediment yield of 2 7 105 m3 km 2 and a denudation rate of 4 105 t km 2 yr 1 comparable with values reported at other active composite cones in wet environment unlike catchments affected by high magnitude eruptions sediment yield at mt semeru however does not decline drastically within the first post eruption years this is due to the daily supply of pyroclastic debris shed over the summit cone which is remobilised by runoff during the rainy season three hazard prone areas are delineated at mt semeru 1 a triangle shaped area open toward the se has been frequently swept by dome collapse avalanches and pyroclastic flows 2 the s and se valleys convey tens of rain triggered lahars each year within a distance of 20 km toward the ring plain 3 valleys 25 km s se and the ring plain 35 km e toward lumajang can be affected by debris avalanches and debris flows if the steep sided summit cone fails

past and future evolution of the marine carbonate system in a coastal zone of the northern antarctic peninsula abstract it is arduous to gather a good spatial and temporal dataset of marine carbonate properties especially in the southern ocean in this study we have reconstructed the carbonate system in the gerlache strait a coastal zone of the northern antarctic peninsula we also analyzed the impact of ocean acidification by calculating the tipping points of the calcium carbonate saturation states and ph i e when saturation state and ph goes below one and 7 respectively hydrographic and carbonate data from three distinct data sets goal 2013 2016 fruela 1996 and world ocean database 1965 2004 have been joined and used to reconstruct the carbonate system from the past 50 years temporal annual mean trends were determined depending on the water column depth layer the northern gerlache strait showed a significant increasing trend of total inorganic carbon concentrations 1 0024 0 34 mol kg 1 and related ph decreasing trend 0 0026 0 0009 sws in the surface mixed layer 60 m the properties variability is relatively different magnitudes and signs between the northern and southern sectors of the gerlache strait which indicate that adjacent regions to the gerlache strait to the southwest and north respectively may major influence the regional carbonate dynamics results also show that episodic under saturation conditions in relation to aragonite within the surface mixed layer may already occur especially in regions close to large glaciers

stabilized dune ridges in northern saskatchewan stabilized dune ridges occurring in northern saskatchewan have previously been identified as variedly as ice crack moraines and longitudinal dunes investigations of their morphological structural and sedimentary attributes reveal that they are indeed of eolian origin but they form a particular group within the parabolic dune association namely the cree lake type dune ridges the ridges occur in association with other types of parabolic dunes and other eolian features such as loess and wind abraded glacial blocks and bedrock outcrops the dunes and the associated eolian features were all formed by southeasterly paleowinds of uniform direction the dune ridges developed from primary parabolic dunes of simple and composite types through the process of dune elongation at the same time exposed rock surfaces were abraded by the wind and loess was deposited downwind from the developing dune fields the southeasterly direction of the paleowinds which is almost directly opposite to the direction of

on the relationship between fronts of the antarctic circumpolar current and surface chlorophyll concentrations in the southern ocean 1 we reexamine the relationship between circulation bathymetry and surface chlorophyll in the southern ocean using new high resolution maps of the frontal structure of the antarctic circumpolar current acc derived from satellite altimetry the maps reveal that the acc consists of multiple filaments or jets by averaging surface chlorophyll measurements along streamlines we show that the fronts define the limits of zones with similar concentrations and seasonality of surface chlorophyll the overall pattern of surface chlorophyll is consistent with strongest upwelling of nutrient rich deep water south of the polar front pf however the distribution of chlorophyll in the southern ocean is concentrated in a number of persistent blooms observed downstream of islands and bathymetric features in contrast to previous studies we find little evidence that the fronts of the acc are associated with enhanced productivity at least where the fronts are distant from topography rather we find that most regions of elevated chlorophyll in the open southern ocean can be explained by upwelling of nutrients both macronutrients and micronutrients where the acc interacts with topography followed by downstream advection the upwelling is shown to be the consequence of the bottom pressure torque established by the large scale flow rather than being due to small scale instabilities of the jets the interaction of the flow with the topography therefore establishes both the large scale dynamical balance of the acc and determines the productivity of the open southern ocean

spatial and temporal patterns in fluvial recovery following volcanic eruptions channel response to basin wide sediment loading at mount pinatubo philippines the june 1991 eruption of mount pinatubo philippines was one of the largest volcanic eruptions of the twentieth century emplacing 5 6 km 3 of pyroclastic fl ow material on the fl anks of the volcano the combination of abundant relatively fi ne grained easily erodible material and intense tropical rainfall led to numerous lahars immediately following the eruption even after major lahars ended sediment yields in some basins remained orders of magnitude above pre eruption levels using data collected from 1996 through 2003 we investigated fi ve basins that experienced varying amounts of sediment loading in the 1991 eruption from 1 to 33 of the basin area covered by valley fi lling pyroclasticfl ow deposits from measurements of fl ow and bed characteristics made through time we developed a general conceptual model for channel recovery following basin wide sediment loading initially fi ner grained sediment and pumice are mobilized preferentially through selective transport once the bed is coarse enough for gravel size clasts to interact with one another clast structures develop increasing form roughness and critical shear stress and inhibiting initial clast mobility as sediment inputs continue to decline the channel incises into valley bottom sediments progressively armoring through winnowing at pinatubo incision and armoring occur fi rst as dry season phenomena due to reduced sediment inputs eventually moving to year round low fl ow bed stability observed timing of the onset of in channel biological recovery suggests that reestablishment of channel stability helps catalyze aquatic ecosystem recovery

ocean acidification and calcium carbonate saturation states in the coastal zone of the west antarctic peninsula the polar oceans are particularly vulnerable to ocean acidification the lowering of seawater ph and carbonate mineral saturation states due to uptake of atmospheric carbon dioxide co2 high spatial variability in surface water ph and saturation states for two biologically important calcium carbonate minerals calcite and aragonite was observed in ryder bay in the coastal sea ice zone of the west antarctic peninsula glacial meltwater and melting sea ice stratified the water column and facilitated the development of large phytoplankton blooms and subsequent strong uptake of atmospheric co2 of up to 55 mmol m 2 day 1 during austral summer concurrent high ph 8 48 and calcium carbonate mineral supersaturation aragonite 3 1 occurred in the meltwater influenced surface ocean biologically induced increases in calcium carbonate mineral saturation states counteracted any effects of carbonate ion dilution accumulation of co2 through remineralisation of additional organic matter from productive coastal waters lowered the ph 7 84 and caused deep water corrosivity aragonite 0 9 in regions impacted by circumpolar deep water episodic mixing events enabled co2 rich subsurface water to become entrained into the surface and eroded seasonal stratification to lower surface water ph 8 21 and saturation states aragonite 1 8 relative to all surface waters across ryder bay uptake of atmospheric co2 of 28 mmol m 2 day 1 in regions of vertical mixing may enhance the susceptibility of the surface layer to future ocean acidification in dynamic coastal environments spatially resolved studies are essential to elucidate the natural variability in carbonate chemistry in order to better understand and predict carbon cycling and the response of marine organisms to future ocean acidification in the antarctic coastal zone

contemporary glacigenic inputs to the dust cycle the importance of glacigenic dust in the earth s system during glacial periods is widely acknowledged under contemporary conditions the world s largest dust sources are in low lying hot arid regions and this is where most aeolian research is focused however the processes of dust production and emissions are still operating in cold climate regions particularly in proglacial areas this paper assesses current understanding of the relationship between glacierised landscapes and dust emissions and inputs to the global dust cycle it focuses on how elements in the glacial and aeolian geomorphic sub systems interact to determine the magnitude frequency and timing of aeolian dust emissions and on feedback mechanisms between the systems where they have been measured dust emission intensity and deposition rates in glacierised catchments are very high in some cases far exceeding those in lower latitudes however few studies span long time scales the impact of future glacier retreat on the balance between sediment supply availability and aeolian transport capacity and implications for glacigenic dust emissions is also considered this balance depends on relative spatial and temporal changes in meltwater suspended sediment concentration and wind strengths which promote dust emissions and patterns and rates of soil development and vegetation succession on recently deglaciated terrain which protect sediments from deflation retreat of the antarctic ice sheet could mean that in future glacigenic contributions to the dust cycle exceed those of non glacigenic sources in the southern hemisphere copyright 2012 john wiley sons ltd

optical dating of holocene dune sands in the ferris dune field wyoming abstract optical dating of late quaternary quartz dune sands from the clear creek portion of ferris dune field wyoming demonstrates the considerable potential of the technique as a chronostratigraphic tool a sequence of radiocarbon dated holocene interdune strata permit optical dating of the intercalated dune sand to be tested the concordance is good the optical dates for the aeolian deposits not datable by radiocarbon suggest that aeolian sedimentation at clear creek peaked during two relatively short phases at ca 8500 and 4000 yr b p the dates indicate that aeolian accumulation maxima at least in the clear creek area may not be synchronous with previously defined phases of marked aridity

ancient and modern cold climate aeolian sand deposition a review although partly active aeolian sand sheets and dunes cover large areas in the zones of dis continuous permafrost little precise information is available about the influence of cold climate conditions on modern aeolian processes this means that palaeoenvironmental reconstructions in the stabilised mainly late pleistocene dune fields and cover sand regions in the sand belts of the european lowlands and the northern great plains of the usa and canada are necessarily still based on ancient evidence cold climate wind deposits are typically derived from areas of abundant sediment supply like unvegetated flood plains glacial outwash plains till plains and lake shores the common parabolic and transverse dune forms resemble those observed in temperate regions although a variety of periglacial features has been identified in late pleistocene dune and cover sands none of them indicate that permafrost is crucial to aeolian activity specific structures in aeolian strata permit tentative interpretation of the moisture content of depositional sand surfaces the nature of annual sedimentation cycles and the processes by which strata were deposited and or contorted but surprisingly little is known about the role of vegetation in the process of sand accumulation dunes are most informative with respect to reconstructions of past wind regimes which offer important data for verification of palaeoclimatic simulations

the origin of horizontal alternating bedding in weichselian aeolian sands in northwestern europe abstract periglacial acolian sands of weichselian age are widespread in the lowlands of western and central europe one facies of this sediment type corresponding to the coversand sensu stricto is characterised by a wavy parallel bedding and a generally horizontal position of the strata since this layering results from an alternation of finer and coarser grained beds horizontal alternating bedding is the appropriate designation for it by a detailed analysis of representative lacquer peels eight characteristic stratification types could be distinguished these units are the smallest fundamental building blocks constituting the sediment under consideration an idealised annual cycle of sedimentation is proposed in summer light and variable winds carry silt in suspension to the site of deposition whilst the sandy saltation load is left behind in a throughput zone farther upwind upon settling the fines adhere to the surface which is wet or damp due to the thawing of the seasonally frozen ground in winter wind strength is generally greater so that deposition of sand prevails in the area whereas the fine grained suspension load settles downwind deposition by snow free winds results in the accretion of patches of well sorted sand snow flurries on the other hand produce niveo aeolian strata of generally more poorly sorted sand in the cycle it is implied that 1 the aeolian sedimentation basin must have been large and uniform enough to permit areal separation of sand and loess like material and 2 a seasonal shift in the centres of sand and silt deposition was inherent to the atmospheric pressure system of the formative period the exposed part of the northern and eastern north sea floor as it existed around the middle weichselian glacial climax assumedly was the principal source area for the deposits the relationships between the periglacial aeolian sands with horizontal alternating bedding loess and their integrades as described from the belgian lowlands and niedersachsen can be interpreted in the context of the proposed depositional cycle

erosion and aggradation on persistently active volcanoes a case study from semeru volcano indonesia erosion processes on active volcanoes in humid climates result in some of the highest sediment yields on earth episodic sediment yields after large eruptions have been evaluated but not the long term and continuous patterns on persistently active volcanoes we have used high spatial resolution satellite imagery and dems dsms along with field based geologic mapping to assess accurately sediment budgets for the active semeru volcano in java indonesia patterns of aggradation and degradation on semeru differ from that of other active volcanoes because 1 both episodic pyroclastic density currents pdc and continuous supplies of tephra generate pulses of sediment 2 sediment is transferred via cycles of aggradation and degradation that continue for 15 years in river channels after each pdc producing eruption and 3 rain triggered lahars remove much greater material than fluvial transport during long intense rainfall events the geomorphic response of two of semeru s rivers to volcanic sediment migration indicates that 1 each river experiences alternating aggradation and degradation cycles following pdc producing eruptions and 2 spatial patterns of sediment transfer are governed by geomorphic characteristics of the river reaches usually high degradation in the steep source reach is followed by a long bypassing middle reach aggradation predominates in the depositional reaches further down valley on the ring plain average sediment yields 103 105 t km2 year at persistently active volcanoes are two to three orders of magnitude lower than sediment yields after large and infrequent eruptions but the continuous and steady sediment transfer in rivers removes more sediment on a mid term 10 years to long term 30 years basis in contrast to the trend observed on composite cones after large and infrequent eruptions decay of sediment yields is not exponential and river channels do not fully recover at steadily active volcanoes as episodic inputs from baf eruptions superimposed on the background remobilization of daily tephra have a greater cumulative effect

magnitude and timing of downstream channel aggradation and degradation in response to a dome building eruption at mount hood oregon a dome building eruption at mount hood oregon starting in a d 1780 and lasting until ca 1793 produced dome collapse lithic pyroclastic flows that triggered lahars and intermittently fed 10 8 m 3 of coarse volcaniclastic sediment to sediment reservoirs in headwater canyons of the sandy river mobilization of dominantly sandy sediment from these reservoirs by lahars and seasonal floods initiated downstream migration of a sediment wave that resulted in a profound cycle of aggradation and degradation in the lowermost reach of the river depositional reach 61 87 km from the source stratigraphic and sedimentologic relations in the alluvial fill together with dendrochronologic dating of degradation terraces demonstrate that 1 channel aggradation in response to sediment loading in the headwater canyons raised the river bed in this reach at least 23 m in a decade or less 2 the transition from aggradation to degradation in the upper part of this reach roughly coincided with the end of the dome building eruption 3 fluvial sediment transport and deposition augmented by one lahar achieved a minimum average aggradation rate of 2 m yr 4 the degradation phase of the cycle was more prolonged than the aggradation phase requiring more than half a century for the river to reach its present bed elevation and 5 the present longitudinal profile of the sandy river in this reach is at least 3 m above the pre eruption profile the pattern and rate of channel response and recovery in the sandy river following heavy sediment loading resemble those of other rivers similarly subjected to very large sediment inputs the magnitude of channel aggradation in the lower sandy river greater than that achieved at other volcanoes following much larger eruptions was likely enhanced by lateral confinement of the channel within a narrow incised valley a combination of at least one lahar and winter floods from frequent moderate magnitude rainstorms and infrequent very large storms was responsible for flushing large volumes of sediment to the depositional reach these conditions permitted a sedimentation response in the sandy river that approached the magnitude of channel aggradation resulting elsewhere from large explosive eruptions and high intensity rainfall regimes despite the fact that the sandy river aggradation was in response to an unremarkable dome building eruption in a climate dominated by low to moderate rainfall intensities

peak flow responses to landscape disturbances caused by the cataclysmic 1980 eruption of mount st helens washington years of discharge measurements that precede and follow the cataclysmic 1980 eruption of mount st helens washington provide an exceptional opportunity to examine the responses of peak fl ows to abrupt widespread devastating landscape disturbance multiple basins surrounding mount st helens 300 1300 km 2 drainage areas were variously disturbed by 1 a debris avalanche that buried 60 km 2 of valley 2 a lateral volcanic blast and associated pyroclastic fl ow that destroyed 550 km 2 of mature forest and blanketed the landscape with silt capped lithic tephra 3 debris fl ows that reamed riparian corridors and deposited tens to hundreds of centimeters of gravelly sand on valley fl oors and 4 a plinian tephra fall that blanketed areas proximal to the volcano with up to tens of centimeters of pumiceous silt sand and gravel the spatially complex disturbances produced a variety of potentially compensating effects that interacted with and infl uenced hydrological responses changes to water transfer on hillslopes and to fl storage and routing along channels both enhanced and retarded runoff rapid posteruption modifi cations of hillslope surface textures adjustments of channel networks and vegetation recovery in conjunction with the complex nature of the eruptive impacts and strong seasonal variability in regional climate hindered a consistent or persistent shift in peak discharges overall we detected a short lived 5 10 yr increase in the magnitudes of autumn and winter peak fl ows in general peak fl ows were larger and moderate to large fl ows q 2 yr were more substantively affected than predicted by early modeling efforts proportional increases in the magnitudes of both small and large fl ows in basins subject to severe channel disturbances but not in basins subject solely to hillslope disturbances suggest that eruptioninduced modifi cations to fleffi ciency along alluvial channels that have very mobile beds differentially affected fl ows of various magnitudes and likely played a prominent and additional role affecting the nature of the hydrological response

posteruption suspended sediment transport at mount st helens decadal scale relationships with landscape adjustments and river discharges received 11 december 2002 revised 30 september 2003 accepted 18 november 2003 published 17 january 2004 1 widespread landscape disturbance by the cataclysmic 1980 eruption of mount st helens abruptly increased sediment supply in surrounding watersheds the magnitude and duration of the redistribution of sediment deposited by the eruption as well as decades to centuries old sediment remobilized from storage have varied chiefly with the style of disturbance posteruption suspended sediment transport has been greater and more persistent from zones of channel disturbance than from zones of hillslope disturbance despite the severe landscape disturbances caused by the eruption relationships between discharge magnitudes and frequencies and suspended sediment transport have been remarkably consistent discharges smaller than mean annual flows generally have transported 5 but locally 15 of the annual suspended sediment loads and infrequent p 0 01 large floods have transported as much as 50 of the annual suspended sediment loads in a single day however moderate magnitude discharges those greater than mean annual flows but less than 2 year floods have transported the greatest amounts of sediment from all disturbance zones such discharges have transported on average 60 to 95 of the annual suspended sediment loads usually within cumulative periods of 1 3 weeks each year although small magnitude and largemagnitude discharges have locally and episodically transported considerable amounts of suspended sediment there has not been any notable change in the overall nature of the effective discharges moderate magnitude flows have been the predominant discharges responsible for transporting the majority of suspended sediment during 20 years of posteruption landscape adjustment index terms 1824 hydrology geomorphology 1625 1815 hydrology erosion and sedimentation 1860 hydrology runoff and streamflow keywords sediment yield suspended sediment transport mount st helens erosion volcano geomorphology

climatic control on quaternary fluvial sedimentology of a fenland basin river england understanding and interpreting climate response from ancient fluvial deposits requires a combined approach of detailed sedimentological description and interpretation local climate proxies and the accurate comparison of these sequences with further independent climate records application of these multiple lines of evidence is particularly effective in the quaternary period where higher resolution and more detailed palaeoenvironmental reconstruction are possible this paper presents results from a devensian weichselian age sequence in northern fenland england that integrates these approaches detailed sedimentological description has identified three fluvial facies associations overlain by a period of ice wedge cast formation fossil plant and coleopteran material within these sediments have been studied to provide palaeoenvironmental reconstructions for the local landscape including quantitative temperature estimates using the mutual climatic range method on fossil coleoptera in addition joint application of radiocarbon and optically stimulated luminescence osl dating allows this sequence to be compared with the stacked marine isotope record although dates do not agree well at the limit of the radiocarbon technique sedimentological interpretations palaeoenvironments and global ice volume variations a proxy for climatic severity are all in agreement and show clearly how the river nene responded to subtle changes in climate and vegetation cover during the devensian weichselian stage the level of detail possible in this reconstruction shows the importance of this approach in understanding fluvial response to past climate changes

the postglacial pleistocene of the northern russian mainland abstract the paper summarizes the results of recent studies of late pleistocene postglacial geological events which occurred in the flatlands of northern russia stretching from the timan ridge to the laptev sea coast the available sedimentary record includes thawed and perennially frozen subaerial sediments and in places lacustrine and fluvial formations hundreds of geochronometric measurements by radiocarbon and luminescence techniques place this record within the time span of 50 11 ka bp which confirms an early mid weichselian age of the underlying glacial complex first established by the queen programme the spectrum of proxies includes sedimentary facies pollen data plant macrofossils oxygen isotope values megafauna remains insect assemblages traces of dna paleosols and permafrost properties together they indicate a continental progressively deteriorating climate with very cold winters and warmer than present summers through the second half of the late pleistocene minor climatic fluctuations are largely due to slightly changing humidity during mis 3 these changes are more pronounced in periglacial european russia in the vicinity of the barents kara ice sheet where the mid weichselian biotic maximum contrasts with conditions in the late weichselian polar desert in siberia the periglacial environments were more stable and beneficial for biota inspite of the increased continentality the recent data accumulated by various researchers are incompatible with the conventional correlation of the karginsky interglacial strata of siberia with mis 3 or any part of the european pleniglacial

simulation of the climate of 18 000 years bp results for the north american north atlantic european sector and comparison with the geologic record of north america abstract the large ice sheets in north america and europe and the extensive sea ice cover in the north atlantic at the time of the last glacial maximum must have greatly modified the surface temperature patterns and in turn the location and intensity of the surface winds and jet streams a general circulation model was used to simulate the january and july patterns of temperature precipitation and wind for 18 ka bp boundary conditions for the model consisting of ice sheet location and height sea ice location and sea surface temperature were prescribed from climap 1981 the model results are illustrated and described for the north american north atlantic european sector the jet stream splits around the north american ice sheet and the southern branch strengthens considerably compared to present over the southern portion of the united states the sea ice margin of the north atlantic and the southern edge of the european ice sheet geologic evidence principally from north america of wind temperature and moisture conditions is assessed from sand dune and loess records estimates of snowline depression pollen records and lake level studies the geologic evidence is generally compatible with the model simulation

dust transport and palaeoclimate during the oldest dryas in central europe implications from varves lake constance this paper evaluates evidence for seasonal loess deposits in peri alpine lake constance at the end of the last glacial oldest dryas chronozone the usefulness of such lacustrine deposits for palaeoclimatic interpretations is discussed the sedimentology of laminated couplets comprising yellow and grey silts has been investigated to test the hypothesis that the couplets are varves i e annual rhythmites comprising alternations of loess and glacial silt and clay the laminae are mostly less than 1 mm thick and include from bottom to top 1 a matrix of well sorted non graded fine yellow silt with sand size intraclasts 2 coarsening upward grey silt with a cap of fining upward silt to clay the latter is typical for varves in modern proglacial lakes and reflects summer and winter deposits silt and clay respectively we propose that the lack of grading and the matrix supported fabric is indicative of aeolian transport and therefore interpret the yellow laminae as loess deposits volcanic glass intraclasts in the loess layers are probably derived from volcanic terrain to the west of the lake indicating an easterly palaeowind direction deposition of loess in the lake occurred regularly at the beginning of each annual cycle suggesting that the palaeowinds were associated with winter and or spring conditions two transport scenarios are suggested to explain the sand grains scattered in this deep water lacustrine record 1 the grains may have been transported as bedload over the annual winter ice cover of the lake under moderate wind strengths frozen into the ice and released for deposition during spring melt 2 the sand grains were blown directly out onto the lake water by very strong winds during spring the first scenario is contrary to the general view that loess was transported during summer and that loess deposits thus reflect summer conditions only loess input to the lake shows a transitional decrease after ca 14 3 kyr bp and cessation at ca 14 kyr bp probably as a result of a change of wind behaviour increased humidity and or vegetational changes during the oldest dryas in central europe