holocene palaeoclimates from peat stratigraphy macrofossil proxy climate records from three oceanic raised bogs in england and ireland quantified analyses of plant macrofossil remains have been made from three profiles of peat from raised bogs spanning a distance of 425 km from western ireland to northern england the reconstructed vegetation of each profile is related to changing bog surface wetness bsw and since the bogs are ombrotrophic these bsw changes are interpreted in terms of changing climate using age depth models based on a total of 49 radiocarbon dates a number of wetter and drier phases are identified and phase shifts to wetter and or cooler climates are defined prominent coincident changes to wetter conditions are dated in at least two of the profiles to ca 4400 4000 1750 1400 and 1000 cal bp and in all three profiles at 3200 2750 2350 2250 and around 700 cal bp these phases are related to proxy climate changes in other terrestrial data sets from northwest europe and a broad degree of synchroneity is demonstrated

decadal scale change of infiltration characteristics of a tephra mantled hillslope at mount st helens washington the cataclysmic 1980 eruption of mount st helens radically reduced the infiltration characteristics of 60 000 ha of rugged terrain and dramatically altered landscape hydrology two decades of erosional biogenic cryogenic and anthropogenic activity have modified the infiltration characteristics of much of that devastated landscape and modulated the hydrological impact of the eruption we assessed infiltration and runoff characteristics of a segment of hillslope thickly mantled with tephra but now revegetated primarily with grasses and other plants to evaluate hydrological modifications due to erosion and natural turbation eruptive disturbance reduced infiltration capacity of the hillslope by as much as 50 fold between 1980 and 2000 apparent infiltration capacities of plots on the hillslope increased as much as ten fold but remain approximately three to five times less than the probable pre eruption capacities common regional rainfall intensities and snowmelt rates presently produce little surface runoff however high magnitude low frequency storms and unusually rapid snowmelt can still induce broad infiltration excess overland flow after 20 years erosion and natural mechanical turbation have modulated but not effaced the hydrological perturbation caused by the cataclysmic eruption copyright 2005 john wiley sons ltd

a fluid dynamics approach to modelling the 18th march 2007 lahar at mt ruapehu new zealand lahars are water sediment mass flows from a volcanic source they can be triggered by a variety of mechanisms and span a continuum of flow rheology and hydraulic properties even within the same event lahars are extremely powerful landscaping agents and represent a considerable hazard potential however this highly dynamic character and a lack of direct measurements has made modelling lahars difficult this study therefore applies a fluid dynamics model delft3d to analyse the 18th march 2007 dam break lahar at mount ruapehu new zealand the modelled lahar routed through the whangaehu gorge in 30 min crossed the whangaehu fan in 60 min and then over a further 3 h travelled an additional 22 km distance along the whangaehu river to the tangiwai bridge the modelled mean frontal velocity was 6 5 m s 1 along the gorge although peak velocity reached up to 19 6 m s 1 the modelled lahar flow front progressively slowed across the fan but along the river it accelerated from 2 1 3 3 m s 1 calculated peak velocity along the river was 4 5 m s 1 these results generally compare well with gauged records with historical records and with other modelling approaches however discrepancies in frontal velocity and time to peak stage arise due to 1 specifying roughness which arises from slope variations between adjacent computational nodes and which is stage dependant and 2 due to rapid topographic changes that produce frequent hydraulic jumps which are inadequately accommodated in the numerical scheme the overall pattern of discharge attenuation and of relationships between topographic and hydraulic variables is similar to that calculated for lahars on other volcanoes this modelling method could be applied at other similar sites where a likely source hydrograph and high resolution topographic data are available these results have important implications for hazard management at ruapehu and for examining geomorphic and sedimentary impacts of this lahar

coupling glacial lake impact dam breach and flood processes a modeling perspective glacial lake outburst floods glofs are highly mobile mixtures of water and sediment that occur suddenly and are capable of traveling tens to hundreds of kilometers with peak discharges and volumes several orders of magnitude larger than those of normal floods they travel along existing river channels in some instances into populated downstream regions and thus pose a risk to people and infrastructure many recent events involve process chains such as mass movements impacting glacial lakes and triggering dam breaches with subsequent outburst floods a concern is that effects of climate change and associated increased instability of high mountain slopes may exacerbate such process chains and associated extreme flows modeling tools can be used to assess the hazard of potential future glofs and process modeling can provide insights into complex processes that are difficult to observe in nature a number of numerical models have been developed and applied to simulate different types of extreme flows but such modeling faces challenges stemming from a lack of process understanding and difficulties in measuring extreme flows for calibration purposes here we review the state of knowledge of key aspects of modeling glofs with a focus on process cascades analysis and simulation of the onset propagation and potential impact of glofs are based on illustrative case studies numerical models are presently available for simulating impact waves in lakes dam failures and flow propagation but have been used only to a limited extent for integrated simulations of process cascades we present a spectrum of case studies from patagonia the european alps central asia and the himalayas in which we simulate single processes and process chains of past and potential future events we conclude that process understanding and process chain modeling need to be strengthened and that research efforts should focus on a more integrative treatment of processes in numerical models

biomarkers as proxies for plant inputs to peats an example from a sub boreal ombrotrophic bog lipid distributions in modern peat forming plants were determined and compared to biomarkers recovered from a ca 2800 year old peat deposited in a dutch ombrotrophic bog the peat section spans a well constrained shift in local hydrology and vegetation and potential molecular proxies for plant inputs were directly tested against the macrofossil record based on the analyses of modern plants low molecular weight lmw n alkanes c23 c25 and high molecular weight n alkanes c33 are proposed as potential biomarkers for sphagnum and non sphagnum inputs respectively consistent with this in the bargerveen peat core lmw n alkane abundances increase and hmw n alkane abundances decrease coincident with the shift to sphagnum dominated peat additional potential proxies include the abundances of c22 alkanedioic acid and phytenyl phytenoate as sphagnum indicators and the abundances of the triterpenoids taraxer 14 ene and taraxast 20 ene as biomarkers for ericaceae rootlets

incipient granular mass flows at the base of sediment laden floods and the roles of flow competence and flow capacity in the deposition of stratified bouldery sands extraordinary floods commonly produce thick deposits as a result of the entrainment and transport often at high concentrations of large volumes of clastic detritus this paper describes the sedimentology of a stratified bouldery sand deposit generated by a 20 km3 breakout flood from intracaldera lake taupo following the 1 8 ka taupo eruption the proximal deposit is characterised by a strongly bimodal grain size distribution with downstream fining boulders enclosed in a poorly sorted and weakly bedded coarse sand to gravel matrix this combination of characteristics is inferred to reflect simultaneous deposition of small and large particles by two distinct mechanisms i accretion of the sandy matrix from an incipient basal granular mass flow as the flood lost capacity and ii progressive emplacement of the boulders as the flood lost the competence to roll them along the channel floor the first mechanism is a product of a nonlinear particle concentration gradient in the sediment laden flow which caused it to segregate into a basal incipient granular mass flow that formed the transient depositional system indicated by the lithofacies the second mechanism is a function of the superjacent turbulent turbid flow that acted as the primary transporting system this pairing of transport and depositional systems is likely to characterise many sediment laden aqueous flows with clay mineral concentrations too low to develop non newtonian rheologies such as jokulhlaups and lahars that entrain unweathered pyroclastic material qualitative and quantitative differences in the way bedload is transported in the presence of this basal granular mass flow as compared to simple water make impossible accurate estimates of flow competence based on shields entrainment functions for beds of both uniform and mixed grain size distribution

biomarkers as paleoclimate proxies in peatlands in coastal high plains in asturias n spain abstract this study represents an attempt to correlate wet and dry episodes as defined by biomarker parameters in peat profiles of asturias north spain the peats developed in a coastal location on high plains at heights ranging between 115 and 256 m above sea level the peat profiles which cover different holocene intervals exhibit growth rates ranging from 0 05 to 0 56 mm yr and so provide records of different resolution biomarkers have revealed the widespread occurrence of nonadecan 2 one k 19 a characteristic of cantabrian peatlands different periods of dominance by higher plants and bacterial triterpenoids and an alternance of humid and dry periods as reflected in the n alkane ratios a change from a more arboreous vegetation before 4000 cal yr bp in the relatively dry warm climate of the middle holocene to a sphagnum herbaceous dominant vegetation typical of cooler wetter conditions is observed the wet episode between 2200 and 3000 cal yr bp has a widespread occurrence in the studied profiles whereas other dry wet episodes are only recorded in some peat deposits and may be associated with local conditions

computer simulation models of scoria cone degradation abstract long term erosional modifications of the relatively simple morphology of scoria cinder cones are ideally suited for study by field and computer simulation methods a series of temporally distinct cones in the san francisco and springerville volcanic fields of arizona provides the foundation for documenting the degradational evolution of scoria cones in a semi arid climate progressive changes due to erosion are illustrated by the systematic decrease with increasing age of various morphometric parameters including scoria cone height cone height width ratio hco wco crater depth width ratio and slope angle for example holocene latest pleistocene cones in the san francisco field have a mean hco wco value of 0 178 0 041 a mean maximum slope angle of 29 7 4 2 and a mean average slope angle of 26 4 7 3 whereas the group of pliocene cones have values of 0 077 0 024 20 5 5 8 and 8 7 2 7 respectively comparative morphology of scoria cones is a potentially useful dating tool for mapping volcanic fields in order to better understand the degradational modifications of these volcanic landforms we have developed a numerical approach to simulate the surficial processes responsible for the erosion of a typical scoria cone the simulation algorithm can apply either a linear diffusion equation model or a model with a nonlinear transport law using a finite difference formulation the simulation operates upon a three dimensional scoria cone input as a matrix of elevation values utilizing both field and model results the correlation between changing hco wco value cone age and computer time step was expressed graphically to derive comprehensive values of the transport or diffusion coefficient df for both volcanic fields for the san francisco volcanic field df had a calculated value of 21 4 m2 kyr for the linear model and 5 3 m kyr for the nonlinear model while for the springerville volcanic field df had a calculated value of 24 4 m2 kyr for the linear model and 6 3 m kyr for the nonlinear model

preliminary results of extraction experiments in an oil shale abstract soxhlet versus ultrasonic extraction efficiency on the immature puertollano oil shale has been tested the yields from the two methods are compared the extracts were compared by gas chromatography and geochemical parameters such as cpi and pristine phytane ratio calculated the ultrasonic extraction procedure is an effective quick and easy method which does not change the biomarker ratios of the bitumen minor efficiency differences can be observed among the solvents allowing a choice on the basis of handling properties carbon disulfide and chloroform are easiest to eliminate from the extract

depositional mechanics and sequences of base surges songaksan tuff ring cheju island korea the songaksan mount in the southwestern part of cheju island korea is a taalian tuff ring produced by phreatomagmatic explosions at an aquifer a detailed analysis of proximal to distal facies changes reveals that the tuff ring sequence can be represented by 21 sedimentary facies one lateral facies sequence lfs and three vertical facies sequences vfs the vfs 1 and 2 are representative of facies relationships in horizontal near vent deposits the vfs 1 comprises scour fill bedded tuff inversely graded tuff massive tuff and laminated tuff from base to top the vfs 2 is a variant of the vfs 1 replaced by an inversely graded lapilli tuff unit at the base the sequences suggest traction carpet suspension and minor traction sedimentation from a high concentration near vent base surge the lfs 1 and the vfs 3 are distilled from outward dipping flank deposits both sequences begin with disorganized lapilli tuff followed successively by stratified lapilli tuff dune bedded lapilli tuff very thinbedded tuff and accretionary lapilli they are suggestive of waning base surge which decreases in particle concentration suspended load fall out rate and flow regimes with an increase in traction and sorting these facies sequences suggest that a base surge experiences flow transformation with its flow characters changing with time and space a near vent base surge is turbulent uniformly mixed and highly concentrated and produces scour fill bedded tuff as capacity decreases the surge transforms into a dense and laminar underflow and a dilute and turbulent upper part gravity transformation depositing inversely graded massive and normally graded lapilli tuff ensuing loss of sediment load and mixing of ambient air result in flow dilution surface transformation stratified and dune bedded units are produced by tractional processes of turbulent and low concentration surge further dilution causes deceleration and cooling and results in precipitation of moistened ash and accretionary lapilli from suspension

holocene vegetation and hydrologic changes inferred from molecular vegetation markers in peat penido vello galicia spain abstract peat molecular chemistry reflects a combination of plant input and decomposition both vegetation community and the degree of decomposition of plant remains are highly dependent on depth and fluctuation of the water table and thus peat organic matter om chemistry reflects past hydrological conditions changes in hydrology according to the om composition by pyrolysis gas chromatography mass spectrometry pyrolysis gc ms in a high resolution sampled monolith of an 8000 years old peat deposit are presented analysis of 18 modern vegetation species resulted in molecular markers for erica spp deschampsia flexuosa juncus bulbosus and carex binervis in addition to more general markers which enabled differentiation between woody grass and moss vegetation factor analysis of 106 pyrolysis products quantified for all peat samples enabled identification of mineral factor 1 and hydrological factor 2 conditions of the bog depth profiles of vegetation markers showed good agreement with those of the scores of both factors and enabled the identification of 14 relatively wet periods dating to 1430 1865 ad 930 1045 ad 640 ad 270 385 ad 190 215 ad 135 ad 45 bc 15 ad 260 140 bc 640 440 bc 1055 960 bc 1505 1260 bc 2300 bc 4190 2945 bc and 5700 5205 bc which show excellent agreement with other palaeoclimatic studies in europe the results emphasize the importance of high resolution sampling in combination with the use of multiple vegetation markers and other peat om characteristics for a proper interpretation of a peat record

impacts of catastrophic volcanic collapse on the erosion and morphology of a distal fluvial landscape hautapu river mount ruapehu new zealand debris avalanches caused by the collapse of volcanic flanks pose a great risk to inhabited areas and may permanently change the surrounding landscape and its drainage systems in this research we explored the interplay between a debris avalanche and a tectonically uplifting surrounding landscape providing insights into the long term consequences of volcanic edifice failures exposures of coarse volcaniclastic sediments along the hautapu river 50 km southeast of mount ruapehu new zealand show evidence of the largest known collapse event of the stratovolcano which was followed by a vigorous regrowth phase that produced numerous pyroclastic eruptions and pumice rich lahars similar diamicton deposits are exposed within the river catchment adjacent to the west cover bed stratigraphy and geochemical correlation of andesitic lava blocks within the debris avalanche deposit with dated lavas exposed on the cone indicate that deposition occurred between 125 and 150 ka the collapse took place during the shift from a glacial to an interglacial climate when glaciers on the cone were in retreat and high pore water pressures combined with deep hydrothermal alteration weakened the cone in addition collapse may have been accompanied by magmatic unrest the 2 3 km3 debris avalanche inundated an area of 260 km2 and entered the proto hautapu catchment where it was channelized within the deeply entrenched valley mass wasting events associated with postcollapse volcanism continued to be channeled into the proto hautapu river for another 10 k y producing long runout lahars subsequently the river catchment was isolated from the volcano by incision of the intervening whangaehu river into the proximal volcaniclastic sediments accompanied by regional faulting and graben deepening around ruapehu at present the volcaniclastic deposits form a distinctive plateau on the highest topographic elevation within the hautapu valley forming a reversed topography caused by preferred incision of the hautapu river into softer late tertiary sediments concurrent with constant uplift

geology and hazard implications of the maraunot notch in the pinatubo caldera philippines the 1991 pinatubo eruption left 5 6 km3 of debris on the volcano slopes much of which has been mobilized into large lahars in the following rainy seasons also during the eruption collapse localized in part along preexisting faults left a caldera 2 5 km in diameter that almost immediately began to accumulate a 1 6 108 m3 lake by 2001 the water had risen to the fault controlled maraunot notch the lowest northwestern portion of the caldera rim comprising the physiographic sill of the caldera lake that year a narrow artificial canal dug into an old volcanic breccia underlying the outlet channel failed to induce a deliberate lake breakout but discharge from heavy rains in july 2002 rapidly deepened the notch by 23 m releasing an estimated 6 5 107 m3 of lake water that bulked up into lahars with a volume well in excess of 1 6 108 m3 lakes in other volcanoes have experienced multiple breakouts providing practical motivation for this study fieldwork and high resolution digital elevation models reveal andesites and ancient lacustrine deposits strongly fractured and deformed along a segment of the maraunot fault a prominent steeply dipping left lateral fault zone that trends n35 40 w within and parallel to the notch seismicity in 1991 demonstrated that the maraunot fault is still active the fault zone appears to have previously been the erosional locus for a large channel filled with avalanche or landslide deposits of an earlier eruption that were exhumed by the 2002 breakout floods the deformed lacustrine sediments with an uncalibrated 14c age of 14 760 40 year bp from a single charcoal sample attest to the existence of an earlier lake possibly within the tayawan caldera rim remnants of which survive as arcuate escarpments that lake may well have experienced one or more ancient breakouts as well the 2002 event greatly reduced the possibility of another such event by scouring away the erodible breccia leaving less erodible fractured andesites and lacustrine rocks and by enlarging the outlet channel and its discharge capacity several lines of evidence indicate however that future lahar generating lake breakouts at the notch may keep populations of botolan municipality downstream at risk 1 a volume of 9 5 107 m3 of lake water remains perched 0 8 km above sea level 2 seismicity in 1991 demonstrated that the maraunot fault is still active and movements of sufficient magnitude could enlarge the outlet and the discharge through it 3 more likely however with or without earthquake activity landslides from the steep to overhanging channel walls could block the channel again and a major rainstorm could then cause a rise in lake level and sudden breakouts 4 intrusion of a new dome into the bottom of the lake possibly accompanied by phreatic explosions could expel large volumes of lahar generating water

evaluation of titan2d modelling forecasts for the 2007 crater lake break out lahar mt ruapehu new zealand abstract following the 1995 1996 eruptions of mt ruapehu the hazard of a dam breakout lahar was immediately recognised because an unstable 7 9 m pile of volcaniclastic ejecta had accumulated over the former stable outlet of the normally 10 106 m3 crater lake prior to the dam breakout lahar of 18 march 2007 a range of flow scenarios down the eastern flanks of mt ruapehu were simulated using the titan2d mass flow numerical code to forecast flow travel times and inundation areas titan2d is a depth averaged code that solves the movement of a granular or two phase mass over digital representations of natural terrains we compared modelled scenarios run before the 18 march 2007 break out lahar of ruapehu to details from the actual event the titan2d models were accurate in predicting both the inundation areas and travel times of the lahar at various key points down the volcano s flanks to 9 km beyond 9 km and a major break in slope the initial model parameters did not cope with the fundamental change that occurred in flow rheology velocity and discharge predicted at a lahar deflection structure the bund at 9 km from the lake were up to 20 less than those of the actual 2007 flow but matched closely those of the largest 1995 lahar at this location predicted paths of flow including sites of avulsion correlated well with those in the march 2007 event in addition the simulations predicted dynamic behaviour such as super elevation of flow in corners and hydraulic ponding that corresponds to real event measurements this application shows that the titan2d model can be used to reliably forecast certain parameters of lahar flow however care must be taken when choosing parameters and flow length scales over which the comparison should be made

volcanism in aboriginal australian oral traditions ethnographic evidence from the newer volcanics province abstract this article collects and presents nineteenth century ethnographic evidence from the newer volcanics province of australia and explores how volcanism was recorded and understood in aboriginal oral traditions it investigates whether aboriginal australian oral traditions can be understood as persistent eyewitness accounts of volcanic eruptions in the newer volcanics province how and what kind of geological and volcanological knowledge was embedded within aboriginal australian oral traditions and considers what value the ethnographic evidence has for understanding both the socio cultural and geological histories of the newer volcanics province

active geodynamics of the central mediterranean sea tensional tectonic evidences in western sicily from mantle derived helium 1 we report results on the measured high 3he 4he isotope ratio in western sicily interpreted together with the heat data the study of this sector of the europe africa interaction is crucial to a better understanding of the tectonics and the geodynamical evolution of the central mediterranean area the estimated mantle derived helium fluxes in the investigated areas are up to 2 3 orders of magnitude greater than those of a stable continental area the highest flux found in the southernmost area near the sicily channel where recent eruptions of the ferdinandea island occurred 20 miles out to sea off sciacca has been associated with a clear excess of heat flow our results indicate that there is an accumulation of magma below the continental crust of western sicily that is possibly intruding and out gassing through roughly n s trending deep fault systems linked to the mantle that have an extensional component although the identification of these faults is not sufficiently constrained by our data they could possibly be linked to the pre existing faults that originated during the mesozoic extensional transtensional tectonic phases

localized and distributed erosion triggered by the 2015 hurricane patricia investigated by repeated drone surveys and time lapse cameras at volcan de colima mexico abstract in october 2015 patricia a major category 5 hurricane made landfall in western mexico resulting in 500 mm cumulated rainfall and lahar generation along the southerly directed montegrande valley of volcan de colima we monitored lahar deposition and erosion using time lapse trail cameras and conducted repeated camera drone overflights two days before and after the hurricane using photogrammetric processing we derive a unique dataset of high resolution digital terrain models and study the geomorphologic impacts of a single lahar event results reveal different types of erosion at 8 km distance from the volcano with overland flow and rill networks developing into major erosion gullies exceeding a depth of 4 m as well as bank collapse oversteepening and marginal erosion we find alternating deposition and erosion zones that depend on general slope and valley width and find that the overland flow related erosion is an important contributor to the bulking process of lahars moreover this study shows that camera monitoring is very useful for studying the relationship between volcano landscape evolution and hydrometeorological extremes and for rapid assessment associated with single lahar events

depositional processes of the suwolbong tuff ring cheju island korea the suwolbong pyroclastic sequence in the western part of cheju island korea comprises partly preserved rim beds of a quaternary basaltic tuff ring whose vent lies about 1 km seaward of the present shoreline the sequence consists of breccia lapillistone lapilli tuff and tuff eighteen sedimentary facies are established and organized into six lateral facies sequences lfs and seven vertical facies sequences vfs the lfs 1 4 and 5 begin with massive lapilli tuff which transforms downcurrent into either planar bedded lfs 1 undulatory bedded lfs 4 or climbing dune bedded lfs 5 lapilli tuff units they are representative of relatively dry base surge whose particle concentration decreases downcurrent with a progressive increase in both tractional processes and sorting the lfs 2 begins with disorganized and massive lapilli tuff and transforms into crudely stratified units downcurrent it results from relatively wet base surge in which sorting is poor due to the cohesion of damp ash the lfs 3 comprises well sorted lapilli tuff and stratified tuff further downcurrent suggestive of deposition from combined fall and surge of relatively dry hydroclastic eruption all seven vertical facies sequences generally comprise two facies units of coarse grained fines depleted lapilli tuff and an overlying fine grained tuff these sequences are suggestive of deposition from base surge that consists of a turbulent head and a low concentration tail depositional processes in the suwolbong tuff ring were dominated by a relatively dry base surge the base surge comprises turbulent and high concentration suspension near the vent whose deposits are generally unstratified due to the lack of tractional transport as the base surge becomes diluted downcurrent through fallout of clasts and mixing of ambient air it develops large scale turbulent eddies and is segregated into coarse grained bedload and overlying fine grained suspension forming thinly stratified units further downcurrent the base surge may be either cooled and deflated or pushed up into the air depending on its temperature the suwolbong tuff ring comprises an overall wet to dry cycle with several dry to wet cycles in it suggestive of overall decrease in abundance of external water and fluctuation in the rate of magma rise

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

petrology and geochemistry of submarine volcanism in the sicily channel rift abstract submarine magmatism in the sicily channel rift began in the early pliocene and lasted until almost 200 yr ago we present here petrological and geochemical data on volcanic rocks dredged from graham and nameless banks and pantelleria seamounts in the pelagian sector of the sicily channel rift petrological evidence suggests that the ascent of magmas to the surface was relatively rapid probably through channels superimposed over the major tectonic discontinuities of the rift major and trace element data indicate an ocean island basalt affinity for graham and nameless bank alkaline lavas and a depleted tholeiitic signature for one pantelleria seamount which had a shallower mantle source sr nd pb isotopic compositions suggest a heterogeneous mantle source involving both focus zone fozo and high himu components lead isotopic compositions are slightly less radiogenic in the tholeiitic basalt and more radiogenic closer to himu in the alkaline lavas we hypothesize that a decompressional me

river responses to the 2010 major eruption of the merapi volcano central java indonesia abstract this study examines the fluvial readjustment of a javanese river impacted by the major eruption of the merapi volcano indonesia in october and november 2010 the basin of the opak river located on the southern flank of the merapi was subject to substantial sediment input related to massive pyroclastic deposits that were remobilized by numerous lahars during the year after the eruption two study sites were equipped in order to evaluate the morphodynamic evolution of the riverbed of the opak river topographic surveys bedload particle marking and suspended sediment sampling revealed an important sediment mobilization during efficient flash floods surprisingly no bed aggradation related to the progradation of a sediment wave was observed two years after the eruptive event marked bed incision was observed the opak river readjustment differs from that of other fluvial systems affected by massive eruptions in two ways firstly local population extracted the sand and blocks injected by the eruption as they represent a valuable economic resource secondly several dams trapped the major part of the sediment load remobilized by lahars

quantifying the geomorphic impacts of a lake breakout lahar mount ruapehu new zealand at 11 18 h new zealand time gmt 12 on 18 march 2007 an impoundment of 0 01 10 6 m 3 of tephra collapsed releasing 1 3 10 6 m 3 of water from crater lake at 2536 m elevation on mount ruapehu the lahar traveled 200 km along the whangaehu river aerial lidar surveys of the upper 62 km of flow path were made before and after the lahar we present here the first large scale quantification of the geomorphic impact of the dam break flood along with the rates and controls on its sediment entrainment and deposition the flood mobilized a net value of 2 5 3 1 10 6 m 3 of boulders gravel and sand over the first 5 km of travel to form a lahar of at least 4 4 10 6 m 3 passing instruments at 6 9 km lidar volume transfer calculations match dynamic measurements made after a logarithmic increase in cumulative net sediment entrainment the lahar appeared to reach its maximum sediment carrying capacity at 22 km patterns of alternating sediment erosion and deposition occurred that dominantly reflect a combination of channel morphology and confinement on the local sediment carrying capacity of the flow

rothenberg scoria cone east eifel a complex strombolian and phreatomagmatic volcano rothenberg scoria cone eifel formed by an alternation of three strombolian and three phreatomagmatic eruptive phases eruptions took place from up to six vents on a 600 m long fissure building an early tuff ring and then two coalescing scoria cones strombolian volcanism dominated volumetrically as the supply of external water was severely limited magma water interaction only occurred during the opening stages of eruption at any vent when discharge rates were low and the fragmentation surface was below the water table the phreatomagmatic deposits consist of relatively well sorted fall beds and only minor surge deposits they contain juvenile clasts with a wide range of vesicularity and grain size implying considerable heterogeneity in the assemblage of material ejected by the phreatomagmatic explosions the transition from phreatomagmatic to strombolian eruption at any vent was rapid and irreversible and strombolian volcanism persisted even when eruption rates are inferred to have waned at the close of each eruptive phase as by then the fragmentation surfaces were high in the growing cones and water was denied access to the magma the strombolian deposits are relatively homogenous consisting of alternating coarser and finer grained well sorted fall beds erupted during periods of open vent eruption and partial blockage of the vent respectively the intervals of strombolian eruption were always a delicate balance between discharge of freely degassing magma and processes such as ponding of degassed magma in the vent collapse of the growing cones and repeated recycling of clasts through the vent clear evidence of the instability of the rothenberg cones is preserved in numerous unconformities within deposits of the inner walls of the cones the close of strombolian phases was probably marked by a decreasing supply of magma to the vents accompanied by ponding and stagnation of lava in the craters

mixed deposits of complex magmatic and phreatomagmatic volcanism an example from crater hill auckland new zealand a series of alternating phreatomagmatic wet and magmatic dry basaltic pyroclastic deposits forming the crater hill tuff ring in new zealand contains one unit m1 which can only be interpreted as the products of mixing of ejecta from simultaneous wet and dry explosions at different portions of a multiple vent system the principal characteristics of m1 are a rapid lateral changes in the thicknesses of and proportions in juvenile components in individual beds and b wide ranges of juvenile clast densities in every sample m1 appears to have been associated with an elongate source of highly variable and fluctuating magma water ratios and magma discharge rates this contrasts with the only other documented mixed wet and dry basaltic pyroclastic deposits where mixing from two point sources of quite different but stable character has been inferred

spatial variability in modern tropical peat deposits from sarawak malaysia and sumatra indonesia analogues for coal petrographic and chemical variability in two tropical low ash domed peat deposits of similar age and physiographic setting but different external morphology were examined as modern analogues for coal both occur in microtidal alluvial to deltaic plain settings support similar arborescent vegetation and have accumulated in the past 5 000 years one deposit is an extremely convex mature done with a surface that rises 10 m above river level the other is a low gradient dome rising only 3 m above river level but with a concave base up to 6 m below both deposits have been eroded by adjacent rivers yet peat in the mature dome has accumulated remote from persistent flooding and exhibits distinctive internal stratigraphy decomposed sapric peat floors the deposits and is overlain by increasingly better preserved woody hemic and a cap of coarse fibrous peat derived from less arborescent vegetation consistent flooding in the low gradient dome has maintained conditions for the accumulation of predominantly woody hemic peat which interfingers with and is overlain by oxidised sapric peat and levee derived clastic sediments peat types in both deposits exhibit distinctive polymodal textures and organo chemical signatures that correspond to botanical input and degree of decay due to the abundance of pre huminite vitrinite macerals in all peat types from these deposits megascopic and microscopic texture is a better discriminator for comparison to ancient coal types it is suggested that the upward vertical sequence of decreasing woodiness and increasing lightness in colour observed in the mature dome might best be compared to sequences observed in tertiary brown coals this typical sequence can be modified or overprinted due to flooding in the burial process

vertical evolution of petrographic and organic geochemical parameters in las duenas mire cantabrian coast north spain abstract las duenas mire has developed on a flat siliceous substrate over the holocene the sedimentary cover has a thickness of around 50 cm and the mire comprises a surface area of 27 ha a core sample obtained using a manual probe was split into sub samples of around 3 4 cm thickness for petrographic and organic geochemical analysis the fen originated by minerogenesis and contains a high concentration of mineral matter throughout its profile which decreases towards the top the present day vegetation is dominated by sphagnum a variety of transparent textinite with intense fluorescence is evidence of the low maturity of the profile which is also confirmed by the presence of low reflecting huminite of the a variety hr 0 15 the fluorescence spectra of sporinite and cutinite are similar and compared with those of transparent textinite they have a lower intensity and are shifted to higher wavelengths the low maturity of the organic matter is also confirmed by the presence of unstable hopane configurations the abundance of hopene and the presence of functionalized hopanoids steroids and other triterpenoids the evolution of the geochemical parameters in the peat profile indicates the presence of more humid conditions in the top 4 cm and at a depth of 11 15 cm these periods are characterized by a high sphagnum higher plant contribution as deduced from the n alkane ratios the low reflectance of huminite at the depth of 11 15 cm could also support less oxidizing condition the sediment at a depth of 22 cm where peaty matter starts to accumulate has been dated as 9603 cal bc whereas the plant fraction at the same depth dates back to a maximum of 200 years sediment reworking derived from radiocarbon dates indicates that this fen is not suitable for palaeoenvironmental studies

interaction between particles transported by fallout and surge in the deposits of the agnano monte spina eruption campi flegrei southern italy abstract the agnano monte spina tephra amst is a complex sequence of beds generated by contrasting fragmentation and transportation dynamics the 4 1 ka eruption was accompanied by a volcano tectonic collapse part of which is the present agnano plain the pyroclastic sequence is subdivided into members and submembers each characterized by different lithological and sedimentological features plinian subplinian fallout deposits frequently alternate with base surge beds of phreatomagmatic origin analysis of lateral facies variations and vertical facies associations of correlated layers of submembers b2 d2 and e2 reveals that during some eruption phases the contrasting eruptive dynamics were almost contemporaneous base surge deposits of submember b2 formed during the declining stage of a plinian column they resulted from highly energetic and steady pyroclastic density currents that traveled long distances from the vent area and surmounted topographic obstacles such as the posillipo hill 150 m and the northern sector of the camaldoli hill 250 m submember d2 pyroclastic density currents formed when contemporaneous fallout from an eruptive column was present coarse particles from the column settled throughout the pyroclastic density current determining a significant increase of the solid load of the base surge the consequent increase of supply rate from the transportation to the depositional zone of the base surge led to the formation of unsteady flows that could not efficiently transport the solid load and did not have the ability to travel long distances base surge deposits of submember e2 were fed by a pulsating phreatomagmatic activity which was punctuated by a short lived fallout phase fallout material which was incorporated as an additional load to the base surges was partially transported by low energy steady pyroclastic density currents that traveled over the agnano plain but did not surmount either the camaldoli or the posillipo hills only the very fine material in continuous suspension in the upper no shearing part of the base surge cloud was dispersed higher in the atmosphere and quietly settled over a large area outside the caldera rim the phreatomagmatic origin of base surges which contrasts with the magmatic origin of fallout activity suggests that the pyroclastic density currents of the agnano monte spina eruption did not result from eruption column collapses they were most likely related to radially spreading clouds which were contemporaneous with fallout activity but issued from distinct zones in the vent area the turbulent nature and the high expansion of base surges made them capable under certain conditions of passing over high topographic obstacles with hazardous effects in distal areas

sedimentary signatures of cyclic growth and destruction of stratovolcanoes a case study from mt taranaki new zealand abstract the long term behaviour of andesite stratovolcanoes is characterised by a repetition of edifice growth phases followed by collapse this cyclic pattern represents a natural frequency at varying timescales in the growth dynamics of stratovolcanoes worldwide around the 130 ka mt taranaki egmont volcano new zealand coastal cliff successions at 20 40 km distance comprise repeating packages of lithologically and sedimentologically distinctive mass flow deposits varying depositional mechanisms and source properties of these units record growth and collapse cycles of the central edifice these are used to construct a model for cyclic volcaniclastic sedimentation in the surrounds of stratovolcanoes during edifice construction phases thick packages of tabular predominantly monolithologic hyperconcentrated flow and debris flow deposits accumulate with intercalated tephra beds the mass flow units commonly contain large proportions of fresh pumice or juvenile lithic andesite intervals of quiescence separating eruptive periods are characterised by landscape re adjustment accompanied by deposition of fluvial and aeolian sediments along with steady accretion of medial ash in contrast brief episodes of destruction are marked by wide spread distinctively clay rich polylithologic debris avalanche deposits and related marginal debris flow units the growth stages can be terminated by an eruption triggered sector collapse or by external forces once the edifice exceeds a critical stable height or profile dependent on eruptive style and local geo tectonic conditions once the edifice becomes metastable regional tectonic earthquakes or shallow level intrusion events are likely triggers for collapse although the resulting debris avalanches represent the greatest individual hazard from such andesite stratovolcanoes their frequency is relatively low compared with other types of mass flows generated during edifice growth phases accurate forecasts of future hazard from mass flow events are therefore dependent on recognition of both the frequency of a stratovolcano s growth cycle and its current position in that cycle

depositional record of historic lahars in the upper whangaehu valley mt ruapehu new zealand implications for trigger mechanisms flow dynamics and lahar hazards mt ruapehu in the central north island of new zealand is one of the most lahar prone volcanoes in the world since historic observations began in 1861 ad more than 50 individual lahars have been recorded in the whangaehu valley alone the natural outlet to the summit crater lake these lahars have been triggered by a variety of mechanisms including explosive eruptions that displaced crater lake water over the outlet or ejected it onto the snow clad summit area of the volcano rain remobilisation of tephra deposits on steep slopes displacement over the outlet as a result of syn eruptive changes in lake bathymetry and lake break outs from crater lake following impoundment of excess water behind temporary barriers of tephra and or ice emplaced over the outlet however only 9 lahar deposits can be distinguished in the upper whangaehu valley on sedimentological stratigraphic geomorphic and petrological grounds and these are skewed towards either the largest or the most recent flows in some cases magnitude can be reconstructed from deposit geometry with the largest lahars producing the highest level terraces the coarsest deposits and crossing drainage divides into normally inactive channels this under representation of historic events reflects the low preservation potential of unconsolidated deposits in a steep alpine environment and the overprinting and recycling effect of large magnitude lahars that rework material down to bedrock and effectively reset the stratigraphic record development of magnitude frequency relationships for ruapehu lahars therefore requires the identification of lahar deposits in proximal medial and distal settings in order to ensure that the full range of events is represented

comparative study of lahars generated by the 1961 and 1971 eruptions of calbuco and villarrica volcanoes southern andes of chile abstract the villarrica and calbuco volcanoes of the andean southern volcanic zone are two of the most active volcanoes in chile and have erupted several times in the xx century the 1961 eruption at calbuco volcano generated lahars on the north east and southern flanks while the 1971 eruption at villarrica volcano generated lahars in almost all the drainages towards the north west and south of the volcano the deposits from these eruptions in the voipir and chaillupen river villarrica and the tepu river calbuco are studied the 1971 lahar deposits on villarrica volcano show a great number of internal structures such as lamination lenses grading of larger clasts and a great abundance of large floating blocks on top of the deposits the granulometry can be unimodal or bimodal with less than 5 by weight of silt clay material sem images reveal a great variety of forms and compositions of clasts the 1961 lahar deposits on calbuco volcano have a scarce number of internal structures steeper margins and features of hot emplacement such as semi carbonized vegetal rests segregation pipes and a more consolidated matrix the granulometry usually is bimodal with great quantities of silt clay material 10 by weight sem images show a uniformity of composition and forms of clasts differences on deposits reveal different dynamics on both lahars the villarrica lahar was generated by sudden melt of ice and snow during the paroxysmal phase of the 1971 eruption when a high fountain of lava was formed the melted water flowed down on the flanks of the volcano and incorporated sediments to become transition flows highly energetic and were emplaced incrementally dilution of the flows occurs when the lahars reached unconfined and flatter areas in cases where the lahar flow found large water streams dilution is enhanced the calbuco lahars were generated by the dilution of block and ash pyroclastic flows by flowing over the ice or snow or by entering active rivers transforming to debris flows the differences on dynamics of both flows show the importance to understand initiation processes of lahars in order to make better hazard assessment due to laharics flows

human induced changes on wetlands a study case from nw iberia abstract wetlands are exceptional ecosystems that contribute to biodiversity and play a key role in the hydrological and carbon cycles knowledge of their long term ecology is essential for a proper understanding of these valuable ecosystems we present the application of multi proxy analyses to a 115 cm thick core from la molina mire alto de la espina located in nw iberia with a chronology spanning since 500 bc the mire is located in an area intensively mined for gold during the roman period and close to a water canalization system used for mining operations at that time our aim was to get insights into the development of the wetland by combining palynological records of hydro hygrophytes non pollen palynomorphs and geochemical analyses supported by 14c datings and multivariate statistics the results indicate a complex pattern of ecological succession during the local iron age the wetland was minerotrophic since 20 ad it was subjected to dramatic hydrological changes due to a rise of the water table fluctuating between the presence of open water and phases of drawdown finally by 745 ad the wetland experienced a rapid evolution towards ombrotrophic conditions high grazing pressure was detected for the last decades the significant change occurred during early roman empire seems to have been the consequence of the direct use of the wetland as a water reservoir of the canalisation system used for gold mining thus the current nature of the mire may be the result of human impact although multiple human and climate induced causes were potentially linked to the detected shifts however the system seems to have been resilient successfully buffering the changes without substantial alterations of its functioning our investigation shows that palaeoecological research is necessary to understand modifications in the structure of wetland ecosystems their long term ecology and the role of human induced changes

geomorphological evolution of a fluvial channel after primary lahar deposition huiloac gorge popocatepetl volcano mexico abstract popocatepetl volcano 19 02 n 98 62 w 5424 m began its most recent period of volcanic activity in december 1994 the interaction of volcanic and glacier activity triggered the formation of lahars through the huiloac gorge located on the northern flank of the volcano causing significant morphological changes in the channel the most powerful lahars occurred in april 1995 july 1997 and january 2001 and were followed by secondary lahars that formed during the post eruptive period this study interprets the geomorphological evolution of the huiloac gorge after the january 2001 lahar variations in channel morphology at a 520 m long research site located mid way down the gorge were recorded over a 4 year period from february 2002 to march 2005 and depicted in five geomorphological maps scale 1 200 for 14 february and 15 october 2002 27 september 2003 9 february 2004 and 16 march 2006 a gis was used to calculate the surface area for the landforms identified for each map and detected changes and erosion deposition processes of the landforms using the overlay function for different dates findings reveal that secondary lahars and others types of flows like sediment laden or muddy streamflows caused by precipitation rapidly modified the gorge channel following the january 2001 non eruptive lahar a period associated with volcanic inactivity and the disappearance of the glacier once located at the headwall of the gorge field observations also confirmed that secondary flows altered the dynamics and geomorphological development of the channel these flows incised and destroyed the formations generated by the primary lahars 1997 and 2001 causing a widening of the channel that continues today after february 2004 a rain triggered lahar and other flows infilled the channel with materials transported by these flows the deposits on the lateral edges of the channel form terraces a recent lull in lahar activity contrasts with the increasing instability of the edges of the channel and the continuous edification and destruction of recent lahar terraces

step pool evolution in the rio cordon northeastern italy the principle that formative events punctuated by periods of evolution recovery or temporary periods of steady state conditions control the development of the step pool morphology has been applied to the evolution of the rio cordon stream bed the rio cordon is a small catchment 5 km2 within the dolomites wherein hydraulic parameters of floods and the coarse bedload are recorded detailed field surveys of the step pool structures carried out before and after the september 1994 and october 1998 floods have served to illustrate the control on step pool changes by these floods floods were grouped into two categories the first includes ordinary events which are characterized by peak discharges with a return time of one to five years 1 8 5 15 m3 s 1 and by an hourly bedload rate not exceeding 20 m3 h 1 the second refers to exceptional events with a return time of 30 50 years a flood of this latter type occurred on 14 september 1994 with a peak discharge of 10 4 m3 s 1 and average hourly bedload rate of 324 m3 h 1 step pool features were characterized primarily by a steepness parameter c h ls s the evolution of the steepness parameter was measured in the field from 1992 to 1998 the results indicate that maximum resistance conditions are gradually reached at the end of a series of ordinary flood events during this period bed armouring dominate the sediment transport response however following an extraordinary flood and unlimited sediment supply conditions the steepness factor can suddenly decrease as a result of sediment trapped in the pools and a lengthening of step spacing the analogy of step spacing with antidune wavelength and the main destruction and transformation mechanism of the steps are also discussed copyright 2001 john wiley sons ltd

coupled fluid dynamics sediment transport modelling of a crater lake break out lahar mt ruapehu new zealand summary lahars and other sudden onset floods are highly dynamic with temporally and spatially evolving sediment loads numerical models of sudden onset flood behaviour particularly those applied to real world events have tended to neglect sediment transport processes this is a serious though perhaps understandable shortcoming given a lack of field measurements on flow bed interactions the extra computational complexity required and the problem of iteratively updating plastic channel boundaries this paper applies a fluid dynamics model with suspended sediment and bedload transport to calculate flow conditions and rapid landscape change due to an initially dilute lahar from mt ruapehu new zealand we take advantage of an unprecedented dataset of net topographic changes determined from pre and post lahar airborne lidar surveys and time series of hydrological measurements to run and validate the model a sensitivity analysis of key controls on water surface elevation and final sediment thickness illustrates how the flow was supply limited in the upper reaches it was capable of transporting a greater volume and calibre of material than that available modelled patterns of net erosion and deposition can replicate those observed r 2 0 79 and are dominantly controlled by channel gradient and topographic

lipid biomarkers in the zoige hongyuan peat deposit indicators of holocene climate changes in west china abstract lipid biomarkers extracted from a peat core obtained from the northeast edge of the tibetan plateau have provided a 13 kyr record of regional climate change a period of warmer climate corresponding to the holocene optimum between 9 ka and 5 ka is evident in greater alteration of n alkanoic acids and n alkanols and in the appearance of biomarkers indicative of greater microbial activity concomitant increases in local precipitation that raised the water level of the peat bog are recorded by increases in the proportions of c23 and c25 n alkanes that are mainly derived from submerged floating plants alternations in submergent and emergent plant n alkane proxies reveal multi decimeter scale rises and falls in the bog water level that relate to variation in precipitation on the tibetan plateau during the holocene major low water level events occurred around 12 6 11 3 10 7 9 4 8 3 6 0 4 5 3 1 2 1 and 1 0 ka these events correlate well with cold dry events recorded in same region from other climatic proxies that reflect millennial scale holocene instability in the asian monsoon system our biomarker results also indicate that peat accumulation and preservation on the tibetan plateau are more sensitive to variability in monsoonal precipitation than in annual temperature

toward a model for the bulking and debulking of lahars 1 the incorporation and loss of material sediments or water during the advance of a lahar can significantly influence the advance rate mobility rheology and inundation limits of the flow and therefore these processes have consequences for destructive potential we have developed a theoretical treatment based on the conservation of flow volume and mass to describe the influence of such processes on the depth discharge and density during transit we apply our model to a common scenario of lahar generation and evolution the formation of an initially dilute flow by catastrophic breaching or ejection of a volcanic summit crater lake followed by bulking due to incorporation of substrate materials and later debulking due to sediment deposition the key features of our model are time dependence and the inclusion of two terms describing the influx or efflux of sediments to or from the flow for lahars triggered by crater lake water we derive the time evolution of flow behavior for comparison with the well documented 1953 lahar of mount ruapehu new zealand our model demonstrates the importance of these processes on observable quantities such as flow depth density and deposit profiles hydrograph evolution and transformations between rheologic density regimes

a prehistoric lahar dammed lake and eruption of mount pinatubo described in a philippine aborigine legend the prehistoric eruptions of mount pinatubo have followed a cycle centuries of repose terminated by a caldera forming eruption with large pyroclastic flows a post eruption aftermath of rain triggered lahars in surrounding drainages and dome building that fills the caldera and then another long quiescent period during and after the eruptions lahars descending along volcano channels may block tributaries from watersheds beyond pinatubo generating natural lakes since the 1991 eruption the mapanuepe river valley in the southwestern sector of the volcano has been the site of a large lahar dammed lake geologic evidence indicates that similar lakes have occupied this site at least twice before an ayta legend collected decades before mount pinatubo was recognized as a volcano describes what is probably the younger of these lakes and the caldera forming eruption that destroyed it

distinguishing base surge deposits and volcaniclastic fluviatile sediments an ancient example from the lower devonian snowy river volcanics south eastern australia a 500 m long road cutting in the lower devonian snowy river volcanics srv eastern victoria australia exposes phreatomagmatic units and volcaniclastic sediments based on bed geometry sorting and sedimentary structures it was possible to distinguish base surge deposits from ephemeral fluvial deposits in this relatively well exposed ancient succession where the base surge deposits infill irregular topography bed sets mantle the pre existing surface but thicken into topographic lows in contrast where the fluvial deposits infill topographic depressions beds onlap laterally against channel walls in addition curvi planar slide surfaces within the base surge deposits generated by inter eruptive slumping indicate rapid emplacement as a constructional tuff rampart maar the base surge deposits are always poorly sorted and commonly contain accretionary lapilli reflecting their deposition from turbulent low particle concentration steam rich pyroclastic currents in contrast the fluvial deposits are relatively well sorted reflecting hydraulic sorting and winnowing during tractional transport and deposition there are significant differences in the types of sedimentary structures present 1 bedding in the base surge deposits is entirely tabular and beds can be traced laterally to the limits of the outcrop in contrast the fluvial deposits have abundant internal scour surfaces that result in beds bedding intervals lensing out laterally over intervals of the order of 5 10 m 2 cross beds with relatively high angle foresets are restricted to the fluvial deposits 3 laterally persistent tabular beds that contain abundant densely packed accretionary lapilli are restricted to the base surge deposits in summary although base surge deposits and ephemeral fluvial deposits can appear superficially similar it is possible to apply facies models carefully to distinguish between them even in ancient successions

n alkan 2 one distributions in a northeastern china peat core spanning the last 16 kyr abstract most research on long chain methyl ketones has focused on their origins and distributions their application in paleoclimate studies is less common than that of other n alkyl lipids the goal of this research was to explore this potential by studying n alkan 2 ones from the hani peat sequence in northeastern china they were identified using gas chromatography mass spectrometry gc ms and showed a distribution ranging from c 19 to c 31 with a strong odd even predominance this type of distribution is considered to derive from sphagum and microbial oxidation of n alkanes comparison with climate sensitive indicators and macrofossil analysis shows that microbial oxidation of n alkanes derived from higher plants was enhanced during the warm early holocene period this led us to develop three n alkan 2 one proxies c 27 c 23 31 c 27 hmw ket carbon preference index cpi h ket and average chain length acl 27 31 ket as possible indicators of paleoclimate in the peat forming environment these proxies in combination with c 27 n alkane d values and peat cellulose 18 o records might allow examination of paleo ecosystem behavior during climatic evolution in northeastern china over the past 16 000 yr

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

the 2007 eruption of kelut volcano east java indonesia phenomenology crisis management and social response we focus in this paper on the processes and consequences of an unusual volcanic eruption at kelut volcano east java in november 2007 after two months of worrying precursor signs kelut volcano erupted but neither explosions nor the usual hazards observed during the historic eruptions happened e g ash falls volcanic bombs and pyroclastic flows instead of an explosive eruption the 2007 eruption was extrusive given than such an eruption could not be predicted the authorities had to manage a new situation we conducted interviews with nine stakeholders of the crisis management team and undertook a questionnaire based survey in the settlement nearest to the crater in order to understand how the authorities managed the crisis and how people reacted inquiries and questionnaires were carried out shortly after the end of the evacuation process when the volcano was still under surveillance for fear of an explosive phase the results display a real gap in what it takes to manage a crisis or live through a crisis this suggests that the unusual eruption pattern of kelut volcano was not the only factor of the misunderstanding between the authorities and the population these problems stem from more structural causes such as the lack of communication and information when there is a need to adapt to a new scenario in such a situation the inability of the crisis management system to take decisions underscored the intrinsic vulnerability of the population despite a hierarchical and strategic top down crisis management approach

early agriculture and palaeoenvironmental history in the north of the iberian peninsula a multi proxy analysis of the monte areo mire asturias spain a multi proxy study pollen and npps geochemical composition and radiocarbon dating combined with principal components analysis was applied to a core sampled in the monte areo mire asturias n spain which covers the last 11 600 years cal bp both signals of holocene climate change and transformations by human activities were recorded the cooler stage of the early holocene the hypsithermal and the neoglaciation periods were indentified but later holocene abrupt climate changes seem not to have been recorded due to the particular evolution of the fen mire system and the impact of human activities on the local hydrology evidence for human activity included a first phase of pastoralism by 7300 cal bp and an extraordinary record of adoption and establishment of agriculture the first evidence of cereal pollen dated to approximately 6700 cal bp represents one of the earliest records of agriculture in northern spain contrary to previous studies which based on assumed biogeographical limitations proposed a late adoption of agriculture in the area our results indicate a rapid expansion of agriculture in northern spain from the eastern to the westernmost areas more in agreement with recent archaeobotanical investigations zapata et al 2004 zapata et al 2005 the research also indicates that climate and human activities interplayed to determine the evolution of the studied area and that a multi proxy approach applied to natural archives appropriately located in areas with evidence of past human occupation is a productive way to obtain circumstantial evidence of early human activity

formal subdivision of the holocene series epoch a discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommission on quaternary stratigraphy international commission on stratigraphy this discussion paper by a working group of intimate integration of ice core marine and terrestrial records and the subcommision on quaternary stratigraphy sqs of the international commission on stratigraphy ics considers the prospects for a formal subdivision of the holocene series epoch although previous attempts to subdivide the holocene have proved inconclusive recent developments in quaternary stratigraphy notably the definition of the pleistocene holocene boundary and the emergence of formal subdivisions of the pleistocene series epoch mean that it may be timely to revisit this matter the quaternary literature reveals a widespread but variable informal usage of a tripartite division of the holocene early middle or mid and late and we argue that this de facto subdivision should now be formalized to ensure consistency in stratigraphic terminology we propose an early middle holocene boundary at 8200 a bp and a middle late holocene boundary at 4200 a bp each of which is linked to a global stratotype section and point gssp should the proposal find a broad measure of support from the quaternary community a submission will be made to the international union of geological sciences iugs via the sqs and the ics for formal ratification of this subdivision of the holocene series epoch copyright 2012 john wiley sons ltd

sedimentology of a sandur formed by multiple jokulhlaups kverkfjoll iceland abstract the kverkfjoll sandur in north iceland is the furthest upstream of a suite of fluvial landforms extending for 200 km along the jokulsa a fjollum river incision of the sandur exposes over 3 km of sedimentary sections up to 15 m in height a sandur wide well bedded succession of matrix rich cobble gravel and pebble granule gravel with individual beds 0 2 to 0 5 m thick indicates that the sandur is primarily the product of sandur wide sheet floods with sediment rich hyperconcentrated flows and also some debris flows and channelised turbulent flows this interpretation is evidenced by bedded hyperconcentrated flow deposits occurring as laterally extensive tabular depositional units that dominate the entire sandur reflecting the unconfined nature of the flow clast supported boulder gravel units interpreted as the product of macroturbulent flow occur in relatively narrow but deep channels the sedimentary succession is interpreted as the product of at least six volcanically generated catastrophic outburst floods jokulhlaups during the little ice age the sedimentology of these little ice age flood deposits on a small high gradient sandur contrasts strongly with the deposits of volcanically generated jokulhlaups on large low gradient coastal sandar and sandar associated with retreating glaciers which have been the basis for most previous models of jokulhlaup sedimentation

giant tuff cone and 12 km wide associated caldera at ambrym volcano vanuatu new hebrides arc abstract ambrym in the new hebrides arc has been considered as an effusive basaltic volcano the present paper discusses the general structure of this edifice which consists of a basal shield volcano topped by an exceptionally large tuff cone surrounding a 12 km wide summit caldera dacitic pyroclastic flow deposits are exposed in the lower part of the tuff series they grade upward into composite sequences of bedded surtseyan type hyaloclastites ash flow deposits and fallout tephra which are essentially basaltic in composition in such a way that the tuff cone may be considered as mainly basaltic the relationship between the eruption of pyroclastics and the collapse event precludes a classical model of caldera formation at a basaltic volcano in which quiet subsidence i e kilauea type is the dominant mechanism interpretation of the tuff series implies intervention of external water and suggests both explosive and collapse mechanisms a model of caldera formation which assumes an enlargement of the ring fracture during a first plinian and dacitic then essentially hydrobasaltic eruption is proposed

amplified hazard of small volume monogenetic eruptions due to environmental controls orakei basin auckland volcanic field new zealand orakei maar and tuff ring in the auckland volcanic field is an example of a basaltic volcano in which the style and impacts of the eruption of a small volume of magma were modulated by a fine balance between magma flux and groundwater availability these conditions were optimised by the pre 85 ka eruption being hosted in a zone of fractured and variably permeable plio pleistocene mudstones and sandstones orakei maar represents an end member in the spectrum of short lived basaltic volcanoes where substrate conditions rather than the magmatic volatile content was the dominant factor controlling explosivity and eruption styles the eruption excavated a crater 80 m deep that was subsequently filled by slumped crater wall material followed by lacustrine and marine sediments the explosion crater may have been less than 800 m in diameter but wall collapse and wave erosion has left a 1 000 m diameter roughly circular basin a tuff ring around part of the maar comprises dominantly base surge deposits along with subordinate fall units grain size texture and shape characteristics indicate a strong influence of magma water and magma mud interactions that controlled explosivity throughout the eruption but also an ongoing secondary role of magmatic gas driven expansion and fragmentation the tuff contains 70 of material recycled from the underlying plio pliestocene sediments which is strongly predominant in the 2 fraction the magmatic clasts are evolved alkali basalt consistent with the eruption of a very small batch of magma the environmental impact of this eruption was disproportionally large when considering the low volume of magma involved dre 0 003 km3 hence this eruption exemplifies one of the worst case scenarios for an eruption within the densely populated auckland city destroying an area of 3 km2 by crater formation and base surge impact an equivalent scenario for the same magma conditions without groundwater interaction would yield a scoria spatter cone with a diameter of 400 550 m destroying less than a tenth of the area affected by the orakei event

volcanoes and human history abstract the study of volcanic hazards leads inevitably to questions of how past cultures have lived in volcanically active regions of the world here we summarize linkages between volcanological archaeological and anthropological studies of historic and prehistoric volcanic eruptions with the goal of evaluating the impact of past eruptions on human populations to better prepare for future events we use examples from papers collected in this volume to illustrate ways in which volcanological studies aid archaeological investigations by providing basic stratigraphic markers and information about the nature and timing of specific volcanic events we then turn to archaeological perspectives which provide physical evidence of the direct impacts of volcanic eruptions such as site abandonment and human migration as well as indirect impacts on local cultures as reflected in human artifacts finally we review anthropological studies of societal responses to past and recent volcanic eruptions we pay particular attention to both the psychological impact of catastrophic events and records of these impacts encoded within oral traditions taken together these studies record drastic short term eruption impacts but adaptation to volcanic activity over the longer term largely through strategies of adaptive land use

developing a simplified geographical information system approach to dilute lahar modelling for rapid hazard assessment in this study we present a geographical information system gis based approach to enable the estimation of lahar features important to rapid hazard assessment including flow routes velocities and travel times our method represents a simplified first stage in extending the utility of widely used existing gis based inundation models such as laharz to provide estimates of flow speeds laharz is used to determine the spatial distribution of a lahar of constant volume and for a given cell in a gis grid a single direction flow routing technique incorporating the effect of surface roughness directs the flow according to steepest descent the speed of flow passing through a cell is determined from coupling the flow depth change in elevation and roughness using manning s formula and in areas where there is little elevation difference flow is routed to locally maximum increase in velocity application of this methodology to lahars on montserrat west indies yielded support for this gis based approach as a hazard assessment tool through tests on small volume 5 000 125 000 m3 dilute lahars consistent with application of manning s law dominant flow paths were mapped and for the first time in this study area velocities magnitudes and spatial distribution and average travel times were estimated for a range of lahar volumes flow depth approximations were also made using modified laharz and these refined the input to manning s formula flow depths were verified within an order of magnitude by field observations and velocity predictions were broadly consistent with proxy measurements and published data forecasts from this coupled method can operate on short to mid term timescales for hazard management the methodology has potential to provide a rapid preliminary hazard assessment in similar systems where data acquisition may be difficult

dynamic interactions between lahars and stream flow a case study from ruapehu volcano new zealand discussion and reply reply the discussion of manville et al highlights several interesting points about interpreting observations of the 1995 whangaehu lahars at ruapehu we would like to add to some of these points and to clarify some of the issues raised by the discussion whereas the three lahars we described were part

bedforms and sediment transport processes in the ephemeral streams of kobo basin northern ethiopia abstract bedforms and channel deposits architecture were studied in the ephemeral streams of the structural basin of kobo in northern ethiopia the froude numbers calculated at bankfull flow for a few of the study reaches are in agreement with the extensive occurrence of horizontal planar lamination small bedforms not previously reported in the literature are found and described as produced mainly by scouring rather than accretion processes equations to predict particle entrainment proved that large individual boulders standing scattered on the stream bed can be transported at bankfull flow for long distances direct inspection of the old alluvium and the modern channel deposits allow to identify a typical arrangement within a single bed consisting of divisions with specific characteristics this model of division association is explained in terms of vertical distribution of shear stress and compared with hyperconcentrated flow and traction carpet models in contrast with recent theories of flat asymmetrical bed waves progradation at froude numbers close to unity

dynamic interactions between lahars and stream flow a case study from ruapehu volcano new zealand discussion and reply discussion cronin et al 1999 1 presented details of an unusual data set obtained from observations of active lahars made during the 1995 eruptions of ruapehu volcano new zealand this data set includes both visual observations and time series variations in stage height and gauged discharge made on

revealing climatic variability of the last three millennia in northwestern iberia using pollen influx data climatic variability of the last 3 millennia in nw iberia has been documented using high resolution pollen analysis of vir 18 core retrieved from the ria de vigo 42degrees14 07 n 8degrees47 37 w the depth age model is based on two accelerator mass spectrometry c 14 dates and three historically dated botanical events in galicia the expansion of juglans and pinus as well as the introduction of eucalyptus during the last 3000 years the relative pollen record demonstrates the occurrence of an open deciduous oak forest indicating a humid and temperate climate in northwestern iberia two step forest reduction since 975 cal bc suggests climate as the main cause rather than major socio economic changes documented in historical archives absolute pollen influx has been compared with instrumental summer and winter temperatures and tentatively used as a proxy of short decadal scale and low amplitude similar to 1degreesc temperature variations this new approach allows us to detect for the first time in nw iberia the millennial scale climatic cyclicity suggested by north atlantic records challenging the apparent climatic stability reflected by the relative pollen record the little ice age is recorded as low pollen influx values between 1400 and 1860 cal ad with a cold maximum at 1700 cal ad maunder minimum the roman and medieval warm periods are detected through high pollen influx values at 250 cal bc 450 cal ad and 950 1400 cal ad respectively c 2003 elsevier science b v all rights reserved

energy growth in laharic mass flows lahars debris flows and sediment rich floods are frequent and deadly hazards at all mountain forming volcanoes their hazard potential is traditionally assessed through mass conserving closed system models where peak conversion rates of potential energy to mechanical energy and hence maximum destruction potential are predicted to occur on the steepest volcano flanks this belies evidence of extremely high energy and deadly catastrophes caused by such flows at large distances from volcanoes here we use the first high resolution record of a moving lahar to develop a new model of the temporally and spatially variable mass flow structure we show that bulk flow energy can grow dramatically in such systems over tens to hundreds of kilometers via momentum transfers from the lahar into water and particles along its path we also demonstrate that dynamic transformations of such flows and their ultimate runout are primarily controlled by the mass flow front

changes in whangaehu river lahar characteristics during the 1995 eruption sequence ruapehu volcano new zealand abstract during the 1995 ruapehu eruptive sequence multiple lahars occurred in the whangaehu river which drains ruapehu s crater lake during the earlier phreatic and phreatomagmatic eruptions lahars were generated by expulsion of waters from the lake but once the lake had emptied lahars were formed by remobilisation of seasonal snowpack laden with saturated freshly erupted tephra four types of lahars occurred during the eruptive sequence 1 initial snow slurry lahars composed of granular snow and ice incorporated by eruptively expelled crater lake waters which left behind frozen deposits with 2 5 20 clastic sediment 2 large dilute lahars generated as the volumes of ejected lake water increased and removed much of the readily available snow at least one third of the pre eruption crater lake volume was expelled during one day producing the largest lahars of the series these lahars were hyperconcentrated flows for up to 84 km from source leaving extensive deposits along the channel margins 3 concentrated lahars smaller volume lahars generated as the frequency of eruptions and volumes of expelled water declined these lahars were able to maintain high sediment concentrations measured at 46 52 by volume suspended sediment at 42 km from source their high sediment concentrations were maintained by erosion and incorporation of sand from the deposits of earlier flows which were lining the channel margins 4 remobilised tephra lahars generated following the two largest tephra eruptions of the sequence seasonal snowpack was covered by water saturated tephra warmer spring temperatures and heavy rainfall events caused collapse and remobilisation of snow and tephra producing several lahars in catchments draining eastern ruapehu

syn and post eruptive erosion gully formation and morphological evolution of a tephra ring in tropical climate erupted in 1913 in west ambrym vanuatu abstract syn and post eruptive erosion of volcanic cones plays an important role in mass redistribution of tephra over short periods descriptions of the early stages of erosion of tephra from monogenetic volcanic cones are rare particularly those with a well constrained timing of events in spite of this lack of data cone morphologies and erosion features are commonly used for long term erosion rate calculations and relative age determinations in volcanic fields this paper offers new observations which suggest differing constraints on the timing of erosion of a tephra ring may be operating than those conventionally cited in 1913 a tephra ring was formed as part of an eruption in west ambrym island vanuatu and is now exposed along a continuous 2 5 km long coastal section the ring surrounds an oval shaped depression filled by water it is composed of a succession of a phreatomagmatic fall and base surge beds interbedded with thin scoriaceous lapilli units toward the outer edges of the ring base surge beds are gradually replaced in the succession by fine ash dominated debris flows and hyperconcentrated flow deposits the inter fingering of phreatomagmatic deposits with syn volcanic reworked volcaniclastic sediments indicates that an ongoing remobilisation of freshly deposited tephra was already occurring during the eruption gullies cut into the un weathered tephra are up to 4 m deep and commonly have c 1 m of debris flow deposit fill in their bases there is no indication of weathering vegetation fragments or soil development between the gully bases and the basal debris flow fills gully walls are steep and superficial fans of collapsed sediment are common most gullies are heavily vegetated although some active ephemeral channels occur these observations suggest that the majority of the erosion of such tephra rings in tropical climates takes place directly during eruption and possibly for only a period of days to weeks afterward after establishment of the gully network tephra remobilisation is concentrated only within them therefore the shape of the erosion modified volcanic landform is predominantly developed shortly after the eruption ceases this observation indicates that gully erosion morphology may not necessarily relate to age of such a landform different intensities of erosion during eruption related to water supply or rainfall are probably the major influence on gully spacing modal depth and form longer term post eruption processes that could be indicators of relative age may include internal gully deepening below basal debris flow fill sediments and possibly widening and side slope lowering due to undercutting and side collapse

geographical information system approaches for hazard mapping of dilute lahars on montserrat west indies many research tools for lahar hazard assessment have proved wholly unsuitable for practical application to an active volcanic system where field measurements are challenging to obtain two simple routing models with minimal data demands and implemented in a geographical information system gis were applied to dilute lahars originating from soufriere hills volcano montserrat single direction flow routing by path of steepest descent commonly used for simulating normal stream flow was tested against laharz an established lahar model calibrated for debris flows for ability to replicate the main flow routes comparing the ways in which these models capture observed changes and how the different modelled paths deviate can also provide an indication of where dilute lahars do not follow behaviour expected from single phase flow models data were collected over two field seasons and provide 1 an overview of gross morphological change after one rainy season 2 details of dominant channels at the time of measurement and 3 order of magnitude estimates of individual flow volumes modelling results suggested both gis based predictive tools had associated benefits dominant flow routes observed in the field were generally well predicted using the hydrological approach with a consideration of elevation error while laharz was comparatively more successful at mapping lahar dispersion and was better suited to long term hazard assessment this research suggests that end member models can have utility for first order dilute lahar hazard mapping

landscape evolution on the eastern part of lombok indonesia related to the 1257 ce eruption of the samalas volcano abstract one of the most powerful eruptions of the holocene known as the samalas eruption had a vei of 7 and took place on lombok eastern indonesia in 1257 ce thick tephra fall covered the entire island and pyroclastic density currents pdcs up to 50 m thick buried almost half of lombok until now there has been no detailed study of the geomorphological evolution of lombok related to this eruption especially for the eastern part of lombok the main goal of this paper is therefore to reconstruct the paleo topography on the eastern part of lombok before the eruption of the samalas volcano in 1257 ce and to analyse the subsequent landscape evolution following this eruption data were collected from more than 1300 points in order to gather geomorphological geological and geochemical information for the eastern part of lombok over the last millennium data were obtained from wells which are widespread in the studied area natural outcrops mainly cliffs along the shoreline and the rivers and human made outcrops in quarries as well as from the two dimensional resistivity profiling dipole dipole array carried out on eastern lombok in 2016 and 2017 we estimate that 4435 5 5 106 m3 of pumice rich pdc over a surface of 171 km2 buried the eastern part of lombok in the aftermath of the 1257 ce eruption and as a result of this rapid pumice rich pdc deposition there has been some aggradation of the shoreline at some points resulting in most of the pre 1257 coral reef being buried after several intense rainfall events the deposited volcanic material was probably eroded during the first decades following the 1257 ce eruption by mountain streams producing lahars we estimate that the remaining volume of pumice rich pdc deposits following this erosion is 625 5 5 106 m3 over a surface of 89 km2 which is equivalent to 14 of the initial volume

the strait of sicily continental rift systems physiography and petrochemistry of the submarine volcanic centres abstract new morphological geophysical mineralogical and petrochemical data on the submarine volcanic centres of the strait of sicily continental rift systems lead to the following conclusions magma types both in the rift valleys pantelleria and linosa and plateau areas adventure bank suggest mantle sources and fractionation processes comparable to those of the ethiopian afar section of the east african rift despite their different tectonic regimes however the volume of the erupted magmas less than 2000 3000 km 3 indicates the similarity with low volcanicity dry rifts this is probably related to the peculiar tectonic setting of the pelagian block african foreland dominated by extensional transcurrent motions connected with a strong neogene compressive dextral e w megashear along the sicilian collisional front in the plateau regions the most evolved rocks are hawaiites graham bank which formed by fractionation in the uppermost mantle probably at the base of the crust magma types vary from quartz tholeiites to basanites in the rift valleys the range of magma types is more restricted transitional to alkali basalts and a considerable volume of highly evolved magmas particularly in the axial volcanic complex of the pantelleria rift was produced in crustal magma chambers isotopic trace element evidence suggests the involvement of transitional to enriched morb and oib type mantle sources in the genesis of the quartz tholeiites alkali basalts and basanites throughout the strait of sicily continental rift system including the iblean plateau

turbulent boundary layer shear flows as an approximation of base surges at campi flegrei southern italy abstract small volume base surge deposits of astroni and agnano monte spina eruptions at campi flegrei consist of sets of beds formed by the passage of multiple pyroclastic density currents each set is made by a fining upward sequence consisting from base to top of 1 an inversely graded layer made of bombs and lapilli 2 a finely laminated layer with wavy bedforms made of coarse ash and fine lapilli 3 a structureless fine ash bed lack of discontinuities at layer contacts allows us to hypothesize that each set of beds represents the passage of one pyroclastic density current the sequence formed as a function of the decreasing particle transportation capability of the base surge during the waxing sustained waning phases of flowage we make the simplifying assumptions that the flow on passing from the deposition of the inversely graded layer to the deposition of the finely laminated layer had low particle concentration was quasi steady and incompressible by such assumptions some of the equations that regulate sediment mechanics are applicable to the base surges of campi flegrei to reconstruct flow density and shear velocity in between the deposition of the two layers structural and textural features of deposits stress the importance of shear and turbulence during transportation and suggest that the turbulent boundary layer shear flow is a good approximation to such pyroclastic density currents we used the coles formula to reconstruct velocity as a function of flow height during the formation of the finely laminated layer of astroni and agnano monte spina base surges the methodology we used allows the reconstruction of flow parameters just at a particular point in time and space of base surge evolution and does not provide the complete picture of the flow history of pyroclastic density currents nevertheless flow velocity and density data as obtained with the proposed approach point to dynamic pressure values that are compatible with those reported for similar currents on other volcanoes we conclude therefore that the results obtained give approximate but helpful information on the nature of such hazardous events at campi flegrei

lateral facies variations in hydromagmatic pyroclastic deposits at linosa italy abstract the linosa volcano less than a million years old located in the sicilian channel is formed by a series of coalescing tuff cones tuff rings spatter cones and lava flows among which the fossa cappellano produced a succession of surges the fossa cappellano 2 deposits which travelled up to 1225 m the lapilli and coarse ashes in the deposits are generally mud coated accretionary lapilli are common and the tuffs are frequently vesiculated suggesting that the surges responsible for the deposits were wet the continuous lateral exposures from the interior of the fossa to the extreme edge of the island show facies evolving in the direction of transport from a massive in the most proximal section to one dominated by cross laminated beds in the most distal section passing by a parallel laminated plane bed facies in each facies mean bed thickness and grain size decrease regularly down current in the cross laminated facies mega ripple wavelength and amplitude decrease in the direction of transport in the coarser sizes there is a significant increase in the direction of transport of the lower density scoriae coupled with a decrease of the non vesiculated lithics in the finer sizes there is a significant increase in relative abundance of the lower density feldspar crystals relative to the fe mg crystals the composition texture and primary structure variations of the fossa deposits are identical to those observed in turbidite sequences and are similar to the characteristics observed in dry surge deposits recently described from korea they are interpreted similarly in terms of decreasing flow power in the direction of transport

maceral composition and molecular markers of two condensed middle holocene peat profiles in n spain abstract this study deals with the palaeohydrological information obtained from lipids composition and vegetal tissue preservation of two peat cores from asturias north spain the two profiles differ in the type of peatland raised bog in la borbolla and blanket bog in buelna and the type of organic matter being more bryophytic in the raised bog and more herbaceous in the blanket bog the peatlands are located close to the coast on impermeable old flat erosion surfaces which favoured peat accumulation within a distance of 3 5 km from each other the accumulation rate varied between 0 05 and 0 07 mm yr and the records extend from around 9000 to 2500 cal yr bp the main differences between the two peat sites can be summarized as follows the raised bog has lower mineral matter content and h c atomic ratio and higher c n ratio and extraction yields compared to the blanket bog it has also a higher tissue preservation index for huminite macerals and increasing inertodetrinite index with depth regarding biomarkers the raised bog has a relatively higher concentration of n alkane 2 ones compared to the corresponding n alkane of similar carbon number higher concentration of medium vs high molecular weight methyl ketones and higher triterpenoids steroids ratio than the blanket bog alternating humid dry periods have been recorded in both profiles based on lipid concentrations indicating that the sphagnum rich intervals in the raised bog are more sensitive than the herbaceous blanket peat record to climatic variations the main humid intervals identified are dated as 5000 7500 cal yr bp in the blanket bog and as 6000 3500 cal yr bp and last 2500 cal yr bp in the raised bog and correlate with the humid periods traced in other peatlands locations in this region the transition middle to late holocene is characterized by humid conditions in the region which favoured the sphagnum growth in the peats the reflectance of huminite in these records appears to be more related with differences in the oxidative conditions than with variation of peat maturity it is higher in the layers with high mineral matter content at the beginning of organic matter accumulation and also in the upper part of the profile subjected to seasonal desiccation a more intense biochemical gelification coincides with higher concentration of hopanoids derived from bacteria in the upper part of the profile acrotelm high amount of nonadecan 2 one k 19 and high concentrations of triterpenyl acetates which are also determined in other peat profiles from northern spain are also detected in these profiles this indicates that the specific conditions required for the formation of these compounds probably associated to wet temperate climate dominated throughout the region

particle fabric and sedimentation of structureless sand southern iceland abstract the interpretation of structureless sand units in terms of flow character and associated depositional mechanism is notoriously difficult to deduce from localized outcrop because such units offer no macroscopic features with which to make distinctions of flow parameters this investigation assesses the significance of directional properties of particle fabric samples taken both vertically and horizontally within structureless sand units deposited by jokulhlaups glacier outburst floods in southwest iceland known to be macroturbulent phenomena based on eyewitness accounts and inferences made from the large scale sedimentary architectures of the deposits given this framework we use particle fabric to verify flow character and depositional mechanism highlighting its potential application to deposits where prior knowledge of conditions is unknown vertical and horizontal trends in particle fabric indicate a causative mechanism that is manifested both spatially and temporally within visually structureless units this data indicates sedimentation onto an aggrading bed beneath a turbulent flow which conforms to the documented turbulent character of the jokulhlaup we demonstrate that cryptic information related to flow parameters can be gleaned from visually structureless sand units through detailed particle fabric analysis and clarify aspects of hyperconcentrated flow behavior and sedimentation

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

lahar hazard assessment using titan2d for an alluvial fan with rapidly changing geomorphology whangaehu river mt ruapehu abstract rapid changes in small areas at the apex of alluvial fans may have devastating consequences by directing downstream flood or lahar impacts into catchments of widely varying population or infrastructure vulnerability during a series of lahars in 1995 at mt ruapehu new zealand aggradation of the whangaehu fan apex draining the eastern edifice caused the onset of avulsion of flows northward into the highly vulnerable tongariro catchment an earth training dike or bund was constructed to protect this catchment by retaining flows on the southern side and the normal lahar outlet path to the south surveys in 2001 late 2005 and following a major lahar in march 2007 now show net degradation of a channel in the whangaehu fan apex bordered by the bund this indicates a net increase in the channel capacity at this site and shows that the bund remains at its effective design capacity past hydrological modelling used for the bund design provided a large range of discharge estimates but lacked precise constraints on the size and nature of lahars from eruption and lake breakout events new modelling has been carried out using titan2d to examine the impacts of a 6 106 m3 volume granular flow down this catchment this simulates either an eruption or a lake breakout induced lahar with a historically typical volumetric bulking factor of 4 these simulations predict minimum discharges between 1800 and 2100 m3 s at the bund site by comparison the largest 1995 flow at this site was estimated at around 1200 m3 s further any single modelled flow from the normal outlet channel of crater lake could not be induced to overtop the bund because discharge appears to be limited by the narrow upper reaches of the whangaehu gorge theoretical discharge levels required to overtop the bund are estimated to be 6800 m3 s assuming no aggradation of the channel by the decelerating flow maximum potential discharge at the bund site is additionally modified by potential bifurcation of lahars above a certain size threshold at a point 2 5 km upstream of the bund a major side channel the chute effectively diverts part of the flows away to the southern side of the whangaehu fan this potential for splitting of the flow appears to have increased since 1995 from aggradation of lahar deposits and reworked sediment in the area immediately upstream of the divide despite remaining at design capacity for lahar events in the whangaehu erosion of new channels following the 2007 lahar renders the bund vulnerable to undercutting

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

dynamic interactions between lahars and stream flow a case study from ruapehu volcano new zealand three lahars were sampled in the whan gaehu river on the eastern flank of ruapehu volcano new zealand at 23 5 and 42 km from the source as they were flowing on september 27 and 29 and october 6 1995 the lahars were generated by water explosively ejected from the highly mineralized crater lake we used the chemical contrast between the lahars and resident stream water in their paths to describe a four phase model of a noncohesive lahar wave in a river channel 1 ambient stream water pushed ahead of the lahar in a process of miscible displacement due to hydrodynamic dispersion 2 a zone of mixing between the stream water and the lahar that increases in length with distance from source 3 a remnant of the original lahar least diluted by stream water that decreases in length and dilutes downstream 4 the tail of the lahar surge peak discharge occurs at the end of phase 1 as water is pushed ahead of the lahar peak sediment concentration occurs at the end of phase 2 where debris entrainment by the flow is at its greatest i e in front of the lahar proper deposits record only phases 2 and 3 of the lahar wave phase 1 flow left only a tide line of organic debris and phase 4 deposits were rapidly eroded by later streamflow downstream dilution by stream water eventually caused transformation of phases 2 and 3 of the lahars from debris flow to hyperconcentrated streamflow and then to normal streamflow as the flows became progressively finer grained and more turbulent

debris flow evolution and the activation of an explosive hydrothermal system te maari tongariro new zealand abstract analysis of the pre and post eruption topography together with observations of the avalanche deposition sequence yields a triggering mechanism for the 6 august 2012 eruption of upper te maari the avalanche was composed of a wedge of c 683 000 774 000 m 3 of coarse breccia spatter and clay rich tuffs and diamictons which slid from the western flanks of the upper te maari crater the failure plane is considered to be a hydrothermally altered clay layer this landslide led to a pressure drop of up to 0 5 mpa enough to generate an explosive eruption from the hydrothermal system below which had been activated over the months earlier by additional heat and gas from a shallow intrusion the landslide transformed after c 700 m into a clay rich cohesive debris flow eroding soils from steep narrow stretches of channel before depositing on intermediate broad flatter reaches after each erosive reach the debris flow contained greater clay and mud contents and became more mobile at c 2 km flow distance however the unsaturated flow stopped due to a lack of excess pore pressure this volume controlled flow deposited thick steep sided lobes behind an outer levee accreting inward and upward to form a series of curved surface ridges

organic geochemical evidence of postglacial paleoenvironmental evolution of the comeya peatland asturias n spain abstract comeya peatland is located in picos de europa national park n spain at 851 m above sea level representing the continuous postglacial infill of a hollow growth rate 0 4 mm yr during the last 15 000 cal yr bp three intervals can be distinguished in the profile the bottom one with ash content close to 90 which is previous to the peatland installation in the area and is followed by an interval with oscillating ash content 30 60 probably related to alluvial fan sedimentation the uppermost one corresponds to the peat deposit with ash content generally close to 10 the present day vegetation consists of sphagnum species with herbaceous plants and heathers the study comprises the analysis of some biomarkers with potential as palaeoenvironmental proxies quantified by gas chromatography mass spectrometry supported by bulk 13 c and 15 n isotopic the biomarker assemblage is dominated by the n alkanes and methyl ketones with medium to high molecular weight and odd number of carbons the biomarker ratios indicate an enrichment in sphagnum characteristic compounds at 120 250 cm 3150 6350 cal yr bp reflecting more humid conditions this episode coincides with higher c n atomic ratio higher values of 13 c and lower of 15 n the wetter conditions of this interval are also shown by the depleted d values of the n alkane particularly those related with mosses as n c 23 and n c 25 and the enriched 13 c values of both n alkanes and methyl ketones segregation of 13 c values has been observed for homologues series in comeya peat with medium molecular weight n alkanes typical of mosses living in waterlogged environments being enriched in 13 c values compared with higher molecular weight n alkanes typical of woody and herbaceous plants of drier habitats this study has shown a slight enrichment of 13 c values of methyl ketones compared to n alkanes the differences being not conclusive to support a common or different origin for both compound classes

shallow seated controls on styles of explosive basaltic volcanism a case study from new zealand abstract the pyroclastic deposits of many basaltic volcanic centres show abrupt transitions between contrasting eruptive styles e g hawaiian versus strombolian or dry magmatic versus wet phreatomagmatic these transitions are controlled dominantly by variations in degassing patterns magma ascent rates and degrees of interaction with external water we use crater hill a 29 ka explosive effusive monogenetic centre in the auckland volcanic field new zealand as a case study of the transitions between these end member eruptive styles the crater hill eruption took place from at least 4 vents spaced along a nne trending 600 m long fissure that is contained entirely within a tuff ring generated during the earliest eruption phases early explosive phases at crater hill were characterised by eruption from multiple unstable and short lived vents later dominantly extrusive volcanism took place from a more stable point source most of the crater hill pyroclastic deposits were formed in 3 phreatomagmatic p and 4 dry magmatic m episodes forming in turn the outer tuff ring and maar crater p1 m1 p2 and scoria cone 1 m2 m4 this activity was followed by formation of a lava shield and scoria cone 2 purely wet activity is represented by the bulk of p1 and p2 and purely dry activity by much of m2 m4 however m1 and parts of m2 and m4 show evidence for simultaneous eruptions of differing style from adjacent vents and rapid variations in the extent and timing of magma water interaction at each vent the nature of the wall rock lithics and these rapid variations in inferred water magma ratios imply interaction was occurring mostly at depths of 80 m and the vesicularity patterns in juvenile clasts from these and the p beds imply that rapid degassing occurred at these shallow levels we suggest that abrupt transitions between eruptive styles in time and space at crater hill were linked to changes in the local magma supply rate and patterns and vigour of degassing during the final metres of ascent

landscape and sedimentary response to catastrophic debris avalanches western taranaki new zealand abstract catastrophic volcanic debris avalanches reshape volcanic edifices with up to half of pre collapse cone volumes being removed deposition from this debris avalanche deposit often fills and inundates the surrounding landscape and may permanently change the distribution of drainage networks on the weakly incised mt taranaki ring plain volcanic debris avalanche deposits typically form a large wedge shape in plan view over all flat lying fans following volcanic debris avalanches a period of intense re sedimentation commonly begins on ring plain areas particularly in wet or temperate climates this is exacerbated by large areas of denuded landscape ongoing instability in the scarp source region damming of river stream systems and in some cases inherent instability of the volcanic debris avalanche deposits in addition on mt taranaki the collapse of a segment of the cone by volcanic debris avalanche often generates long periods of renewed volcanism generating large volumes of juvenile tephra onto unstable and unvegetated slopes or construction of new domes with associated rock falls and block and ash flows the distal ring plain impact from these post debris avalanche conditions and processes is primarily accumulation of long run out debris flow and hyperconcentrated flow deposits with a variety of lithologies and sedimentary character common to these post debris avalanche units is evidence for high water content flows that are typically non cohesive hence sedimentary variations in these units are high in lateral and longitudinal exposure in relation to local topography the post collapse deposits flank large scale fans and hence similar lithological and chronological sequences can form on widely disparate sectors of the ring plain these deposits on mt taranaki provide a record of landscape response and ring plain evolution in three stages that divide the currently identified warea formation 1 the deposition of broad fans of material adjacent to the debris avalanche unit 2 channel formation and erosion of stage 1 deposits primarily at the contact between debris avalanche deposits and the stage 1 deposits and the refilling of these channels and 3 the development of broad tabular sheet flows on top of the debris avalanche leaving sediments between debris avalanche mounds after a volcanic debris avalanche these processes represent an ever changing and evolving hazard scape with hazard maps needing to be regularly updated to take account of which stage the sedimentary system is in