magmatic and hydromagmatic conduit development during the 1975 tolbachik eruption kamchatka with implications for hazards assessment at yucca mountain nv abstract xenoliths in pyroclastic fall deposits from the 1975 tolbachik eruption constrain the timing and development of subsurface conduits associated with basaltic cinder cone eruptions the two largest tolbachik vents contain xenoliths derived from magmatic and hydromagmatic processes which can be correlated with observed styles of eruption activity although many basaltic eruptions progress from early hydromagmatic activity to late magmatic activity transient hydromagmatic events occurred relatively late in the 1975 eruption sequence magmatic fall deposits contain 0 01 0 3 vol xenoliths from 500 m depth into the dry out zone around the conduit disrupting and ejecting 10 5 10 6 m 3 of wall rock through hydromagmatic processes with conduits widening to 8 48 m hydromagmatic falls contain 60 75 vol of highly fragmented xenoliths with juvenile clasts displaying obvious magma water interaction features during the largest hydromagmatic event unusual breccia bombs formed containing a wide range of fresh and pyrometamorphic xenoliths suspended in a quenched basaltic matrix hydromagmatic activity during the 1975 tolbachik eruption occurred below likely fragmentation depths for a basalt containing 2 2 wt magmatic water this activity is more likely related to conduit wall collapse rather than variations in conduit flow pressure in contrast larger volume silicic eruptions may have transient hydromagmatic events in response to conduit flow dynamics above the magma fragmentation depth the 1975 tolbachik volcanoes are reasonably analogous to quaternary basaltic volcanoes in the yucca mountain region and can guide interpretations of their poorly preserved deposits the youngest basaltic volcanoes near yucca mountain have cone deposits characterized by elevated xenolith abundances and distinctive xenolith breccia bombs remarkably similar to 1975 tolbachik deposits extrapolation of 1975 tolbachik data suggests conduits for some yucca mountain basaltic volcanoes may have widened locally on the order of 50 m in response to late stage hydromagmatic events

hydrogeology of a complex champlain sea deposit quebec canada implications for slope stability the thick sequences of marine clayey deposits which blanket the st lawrence lowlands in south eastern canada are highly susceptible to landslides with 89 of the population of the province of que

drivers of explosivity and elevated hazard in basaltic fissure eruptions the 1913 eruption of ambrym volcano vanuatu sw pacific abstract fissure eruptions along linear structures can extend for several tens of kilometres with distinct separate manifestations of volcanism along their length they typically involve low viscosity mafic magmas forming long lava flows and cinder cones eruptions in 1894 and 1913 on ambrym volcano vanuatu showed how these mildly explosive eruptions can rapidly transform into violent explosive events producing significant hazard and widespread volcanic ash clouds during the 1913 episode a fissure began in the central caldera and basaltic magmas broke out in a series of locations down the island s western flank in all sites over 100 m in elevation fissure outbreaks produced vigorous lava fountains and highly fluid lava flows that travelled rapidly to the shoreline when the outbreaks propagated along the island s axis into coastal plain areas a climactic series of explosive eruptions occurred producing a 1 2 km long by 600 m wide maar and tephra ring a further small tuff ring was formed later creating a temporary island 400 m offshore the onshore tephra ring destroyed a hospital and associated buildings its last evacuating occupants were close witnesses to the eruption processes deposits exposed in the lower portion of the tephra ring show that this part of the eruption began with a mild phreatomagmatic explosive eruption from a narrow vent followed by a magmatic scoria producing phase subsequently a complex sequence of highly explosive phreatomagmatic eruptions occurred producing pyroclastic surges along with repeated distinctive breccia horizons rich in coral and lava country rock these features tally with eye witness accounts to indicate that the main eruption phase was produced by a periodically shifting locus of phreatomagmatic fragmentation and eruption along a single e w fissure the glassy and vesicle poor pyroclasts produced during this eruption phase were dominantly fragmented in a brittle manner by magma water interaction low volatile content of the magma upon fragmentation is confirmed by ftir analysis showing

reconstruction of landslide movements by inversion of 4 d electrical resistivity tomography monitoring data reliable tomographic inversion of geoelectrical monitoring data from unstable slopes relies critically on knowing the electrode positions which may move over time we develop and present an innovative inverse method to recover movements in both surface directions from geoelectrical measurements made on a grid of monitoring electrodes for the first time we demonstrate this method using field data from an active landslide to recover sequences of movement over timescales of days to years comparison with gps measurements demonstrated an accuracy of within 10 of the electrode spacing sufficient to correct the majority of artefacts that would occur in subsequent image reconstructions if incorrect positions are used over short timescales where the corresponding subsurface resistivity changes were smaller the constraints could be relaxed and an order of magnitude better accuracy was achievable this enabled the onset and acceleration of landslide activity to be detected with a temporal resolution of a few days

from feeder dykes to scoria cones the tectonically controlled plumbing system of the rauðholar volcanic chain northern volcanic zone iceland the rau holar volcanic chain located in the northern volcanic zone of iceland has been variably eroded such that in the northern part the original scoria cones are preserved while the central and southern parts expose their shallow feeders the chain thus offers insight into the inner workings of the near surface feeder system of scoria cones the volcanic chain was mapped in 3d using gps the en echelon arranged volcanic chain can be divided into three parts the southernmost part contains only plugs and necks with a thin pyroclastic cover as well as multi tiered lava flows the central part combines partially eroded scoria cones feeder dyke intersections and welded scoria interbedded within rootless and clastogenic lava flows the welded scoria is composed of different kinds of lithics and bombs the northern part preserves almost intact overlapping scoria cones with voluminous lapilli sized scoriaceous deposits the overall dyke trend is orthogonal but shows radial patterns in individual cone complexes feeder dykes observed to depths of about 200 m below the volcanic chain are up to 8 m thick and flare in to conduits in the uppermost 20 50 m the exposed shallow plumbing system shows that magma pathways through the volcanic edifice are very complex with incremental repeated intrusions we interpret the arcuate shape to be the result of a local change in the orientation of the stress field because the rau holar volcanic chain is located within a major relay structure between volcanoes on the eastern fremrinamur rift arm and a rift extension with grabens on the western periphery

topographic controls on a phreatomagmatic maar diatreme eruption field and numerical results from the holocene dotsero volcano colorado usa we analyze the eruptive products of holocene dotsero volcano colorado usa 4 15 ka which record evidence of a progression from effusive magmatic activity through explosive phreatomagmatic maar forming activity to a final explosive magmatic phase the nature of the deposits suggests that the irregular and mountainous pre eruptive topography strongly influenced the formation of directed pyroclastic density currents pdcs during the phreatomagmatic phase where the topographically high northern crater rim acted as a barrier and promoted transport to the south furthermore the crater shape strongly controlled the grain size of the final deposits providing further evidence that deposit grain size can be a misleading proxy for fragmentation or explosion intensity we test these hypotheses as gleaned from fieldwork by implementing a multiphase numerical model to simulate discrete explosions and their resulting pdcs at maar diatreme volcanoes we confirm that a crater shape where one rim is higher than the other promotes multiple pulses of particle transport in the direction of the lower rim the initial pdcs contain both coarse and fine particles whereas pdcs generated by later pulses contain predominately finer particles this mechanism provides an alternative explanation to the formation of lapilli tuff tuff couplets often found at maar diatreme tephra rings including dotsero volcano additional modeling shows how the crater depth can control grain size of the resulting pdc deposits in the case of a deep crater and a relatively weak explosion it is possible that only the fine particles escape following collapse of the eruptive column resulting in a fine grained deposit this work allows us to improve models developed to describe emplacement of pdcs for different crater geometries and informs on the dynamics of maar diatreme eruptions but also highlights the limitations of our knowledge of key parameters especially those related to the processes of magma water interaction and syn eruptive hydrogeology during such events

eruptive style of the young high mg basaltic andesite pelagatos scoria cone southeast of mexico city the eruption of the pelagatos scoria cone in the sierra chichinautzin monogenetic field near the southern suburbs of mexico city occurred less than 14 000 years ago the eruption initiated at a fissure with an effusive phase that formed a 7 km long lava flow and continued with a phase of alternating and or simultaneous explosive and effusive activity that built a 50 m high scoria cone on the western end of the fissure and formed a compound lava flow field near the vent the eruption ended with the emplacement of a short lava flow that breached the cone and was accompanied by weak explosions at the crater products consist of a microlite rich high mg basaltic andesite samples were analyzed to determine the magma s initial properties as well as the effects of degassing induced crystallization on eruptive style although distal ash fallout deposits from this eruption are not preserved a recent quarry exposes a large section of the scoria cone detailed study of exposed layers allows us to elucidate the mode of cone building activity petrological and textural data combined with models calibrated by experimental work and melt inclusion analyses of similar magmas elsewhere indicate that the magma was initially hot 1 200 c gas rich up to 5 wt h2o crystal poor 10 vol fo90 olivine phenocrysts and thus poorly viscous 40 80 pa s during the early phase low magma ascent velocity at the fissure vent allowed low viscosity magma to degas and crystallize during ascent producing lava flows with elevated crystal contents at t 1 100 c and blocky surfaces later the closure of the fissure by cooling dikes focused the magma flow at a narrow section of the fissure this led to an increased magma ascent velocity rapid and shallow degassing 3 km deep triggered 40 vol microlite crystallization limited times for gas escape and higher magma viscosity 6 105 4 106 pa s drove strong explosions of highly 60 80 vol and finely vesicular magma coarse clasts broke on landing which implies brittle behavior due to complete solidification this requires sufficient time to cool and in turn implies ejection heights of over 1 km which is much higher than normal strombolian activity hence magma viscosity significantly impacts eruption style at monogenetic volcanoes because it affects the kinetics of shallow degassing the long lasting eruptions of jorullo and paricutin which produced similar magmas in western mexico were more explosive this can be related to higher magma fluxes and total erupted volumes implications of this study are important because basaltic andesites are commonly erupted to form monogenetic scoria cones of the trans mexican volcanic belt

shallow plumbing and eruptive processes of a scoria cone built on steep terrain abstract dark peak lunar crater volcanic field central nevada usa is an eroded pliocene monogenetic basaltic volcano that exposes intrusions while preserving some pyroclastic deposits and lavas allowing reconstruction of the shallow magma feeding system and its relation to eruptive processes variably welded agglomerates record strombolian and hawaiian fountaining dikes fed degassed magma to a bocca on the lower cone slopes and fed a small lava field the cone was built on the side of a steep ridge with small side drainages had a maximum diameter of about 1 km and was 125 m high above the highest point on the paleotopography the eruption was fed by an 1 km long narrow 1 3 m feeder dike that locally flared in the upper tens of meters to form an 30 m wide conduit around which the cone was built the conduit shape and the transition depth from feeder dike to conduit are consistent with data from other exposed plumbing systems of small volume basaltic volcanoes that were dominated by magmatic volatile driven eruption styles supporting inferences that their conduits are relatively shallow features upper 150 m

aspects of potential magmatic disruption of a high level radioactive waste repository in southern nevada volcanic hazard studies combining standard techniques of hazard appraisal and risk assessment probability x s consequences are being undertaken with respect to storage of high level radioactive waste in southern nevada consequence studies the emphasis of this work are evaluated by tracing the steps of ascent of basaltic magma including intersection and disruption of a repository followed by surface eruption outhern nevada is cut obliquely by a n ne trending belt of basaltic volcanism that contains a number of major volcanic fields separated by areas with scattered basalt centers the basalts of the belt range in age from 8 m y to recent they are primarily of hawaiite composition and a number of the fields exhibit the straddle type associations of the alkalic subsuite the basalts are characterized by high 87 sr 86 sr isotopic ratios 0 707 and high sr contents and are evolved from parental compositions by crystal fractionation theoretical considerations suggest basalt magma ascends

assessment of ground based monitoring techniques applied to landslide investigations a landslide complex in the whitby mudstone formation at hollin hill north yorkshire uk is periodically re activated in response to rainfall induced pore water pressure fluctuations this paper compares long term measurements i e 2009 2014 obtained from a combination of monitoring techniques that have been employed together for the first time on an active landslide the results highlight the relative performance of the different techniques and can provide guidance for researchers and practitioners for selecting and installing appropriate monitoring techniques to assess unstable slopes particular attention is given to the spatial and temporal resolutions offered by the different approaches that include real time kinematic gps rtk gps monitoring of a ground surface marker array conventional inclinometers shape acceleration arrays saa tilt meters active waveguides with acoustic emission ae monitoring and piezometers high spatial resolution information has allowed locating areas of stability and instability across a large slope this has enabled identification of areas where further monitoring efforts should be focused high temporal resolution information allowed the capture of s shaped slope displacement time behaviour i e phases of slope acceleration deceleration and stability in response to elevations in pore water pressures this study shows that a well balanced suite of monitoring techniques that provides high temporal and spatial resolutions on both measurement and slope scale is necessary to fully understand failure and movement mechanisms of slopes in the case of the hollin hill landslide it enabled detailed interpretation of the geomorphological processes governing landslide activity it highlights the benefit of regularly surveying a network of gps markers to determine areas for installation of movement monitoring techniques that offer higher resolution both temporally and spatially the small sensitivity of tilt meter measurements to translational movements limited the ability to record characteristic s shaped landslide movements at hollin hill which were identified using saa and ae measurements this high sensitivity to landslide movements indicates the applicability of saa and ae monitoring to be used in early warning systems through detecting and quantifying accelerations of slope movement

a long term field study for the investigation of rainfall induced landslides a two year monitoring experiment has been conducted on a slope in shallow weathered soils overlying sandstone bedrock in toessegg switzerland water balance and suctions were measured together with the meteorological inputs in preparation for predicting environmental effects on slope stability electrical resistivity tomography proved particularly helpful in establishing the spatial distribution of soil layering with clayey sand overlying silty sand and bedrock this paper describes monitoring of the field measurements and shows that the double layer causes a bi seasonal response with the smallest factor of safety after the wetter winter months

the age of lathrop wells volcanic center an 40ar 39ar dating investigation the sup 40 ar sup 39 ar age spectrum analyses of basalt whole rock and partially degassed sanidine xenocrysts for the lathrop wells volcanic center nevada yield eruption ages of 77 3 plus minus 6 0 and 76 6 plus minus 4 9 ka 2 sigma for the ql sub 1 and ql sub 2 flows respectively basaltic samples were analyzed in four to six replicate runs and yield normally distributed plateau ages miocene ash flow tuff xenoliths were collected from the basaltic units with the majority of samples coming from the ql sub 2 the sanidines from the ql sub 2 xenoliths yielded apparent plateau ages n 10 ranging from 69 plus minus 17 to 309 plus minus 11 ka with a strong cluster n 6 at approximately 77 ka because the diffusion dimension of sanidine is approximated by the physical crystal size cracking of the sanidine following the development of an argon concentration profile may result in complex argon age spectra experimental studies exploring the natural and laboratory argon systematics of degassed sanidine reveal that crystal breakage and hf acid etching lead to anomalously old apparent ages these new ages for the ql sub 1 and ql sub 2 flows are analytically indistinguishable and agree well with published eruption ages determined by sup 3 he and sup 36 cl cosmogenic surface exposure dating methods we conclude that the ql submore 1 and ql sub 2 flows are temporally equivalent additionally the agreement between our eruption ages for these units and the published 76 plus minus 20 ka ital zreda ital et al 1993 sup 36 cl exposure age for the lathrop wells scoria cone qs sub 3 suggests that the cone may be temporally equivalent to the ql sub 1 and ql sub 2 flows we believe the simplest and most reasonable interpretation is that the volcanic center is monogenetic copyright 1999 american geophysical union less

localization of volcanic activity topographic effects on dike propagation eruption and conduit formation magma flow in a dike rising in a crack whose strike runs from a highland or a ridge to an adjacent lowland has been modeled to determine the effect of topography on the flow it is found that there is a distinct tendency for the flow to be diverted away from the highland end of the strike toward the lowland separation of the geometric effect of the topography from its effect on lateral confining stresses on the crack indicates that both contribute to the effect but that the effect of stress is less important although this analysis explains a tendency for volcanic eruptions to occur in low lands it does not preclude eruptions on highlands the particular configuration modeled mimics topography around the proposed nuclear waste repository at yucca mountain nevada so that the results may indicate some reduction in the volcanic hazard to the site

field monitoring of the corvara landslide dolomites italy and its relevance for hazard assessment the corvara landslide is an active slow moving rotational earth slide earth flow located uphill of the village of corvara in badia one of the main tourist centres in the alta badia valley in the dolomites province of bolzano italy present day movements of the corvara landslide cause national road 244 and other infrastructures to be damaged on a yearly basis the movements also give rise to more serious risk scenarios for some buildings located in front the toe of the landslide for these reasons the landslide has been under observation since 1997 with various field devices that enable slope movements to be monitored for hazard assessment purposes differential gps measurements on a network of 47 benchmarks has shown that horizontal movements at the surface of the landslide have ranged from a few centimetres to more than 1 m between september 2001 and september 2002 over the same period vertical movements ranged from a few centimetres to about 10 cm with the maximum displacement rate being recorded in the track zone and in the uppermost part of the accumulation lobe of the landslide borehole systems such as inclinometers and tdr cables have recorded similar rates of movement with the depths of the major active shear surfaces ranging from 48 m to about 10 m from these data it is estimated that the active component of the landslide has a volume of about 50 million m3 in this paper the monitoring data collected so far are presented and discussed in detail to prove that the hazard for the corvara landslide considered as the product of yearly probability of occurrence and magnitude of the phenomenon can be regarded has as medium or high if the velocity or alternatively the volume involved is considered finally it is also concluded that the monitoring results obtained provide a sound basis on which to develop and validate numerical models manage hazard and support the identification of viable passive and active mitigation measures

the use of surface monitoring data for the interpretation of landslide movement patterns the tessina landslide is a large seasonally active slope failure located on the southern slopes of mt teverone in the alpago valley of ne italy consisting of a complex system that has developed in tertiary flysch deposits the landslide which first became active in 1960 threatens two villages and is hence subject to detailed monitoring with high quality data being collected using piezometers inclinometers extensometers and through the use of a highly innovative automated electronic distance measurement edm system which surveys the location of a large number of reflector targets once every 6 h these systems form the basis of a warning system that protects the villages but they also provide a very valuable insight into the patterns of movement of the landslide in this paper analysis is presented of the movement of the landslide concentrating on the edm dataset which provides a remarkable record of surface displacement patterns it is proposed that four distinct movement patterns can be established which correspond closely to independently defined morphological assessments of the landslide complex any given block of material transitions through the four phases of movement as it progresses down the landslide with the style of movement being controlled primarily by the groundwater conditions the analysis is augmented with modelling of the landslide undertaken using the itasca flac code the modelling suggests that different landslide patterns are observed for different parts of the landslide primarily as a result of variations in the groundwater conditions the model suggests that when a movement event occurs displacements occur initially at the toe of the landslide then retrogress upslope

microstructures within a modern debris flow deposit derived from quaternary glacial diamicton a comparative micromorphological study abstract examination of a modern debris flow in comparison with a quaternary diamicton from which it has been derived reveals significant differentiating sedimentological characteristics the two sediments were examined using micromorphological analyses thin sections of the debris flow show distinct primary microstructure sets that appear indicative of debris flow processes of turbate micro deformation during flow and subsequent flow deceleration comparison of the micromorphological character of both sediments reveal many similarities but the differences seem indicative of flow processes within the active debris flow large turbate structures are common within the debris flow sediment and although many more turbate structures occur within the in situ diamicton they are smaller in size possibly indicative that those structures within the debris flow sediment are not inherited but are neo formed perhaps the most distinctive and individual characteristic separating the debris flow sediment from the older diamicton is the presence of tiled structures these structures result from downslope flow deceleration and dewatering resulting in transverse bands of clays developing in rhythmic like patterns likewise the debris flow sediment exhibits a marbled appearance presumably indicative of intense deformation a characteristic not found in the in situ quaternary diamicton

cliff retreat and talus development at the caldera wall of mount st helens computer simulation using a mathematical model abstract to simulate the landform evolution at the caldera wall of mount st helens usa a mathematical model for talus development was applied to model the topographic change during the 11years from the volcanic eruption i e from formation of the cliff simulated results show that the topographic change is predicted to be large for about 10years after the eruption and to decline thereafter if snow accumulation in the talus slope deposits is negligible the talus top will not reach the cliff top within 300years after the eruption talus growth in mount st helens was much faster than that in the chichibu basin japan this may indicate the low strength and or high weathering rate of the rockwall of mount st helens resulting in rapid production of debris and rapid retreat of the cliff

space time evolution of monogenetic volcanism in the mafic garrotxa volcanic field ne iberian peninsula we reconstructed the evolution of the volcanic activity within the central garrotxa monogenetic volcanic field the youngest volcanic area of the iberian peninsula by investigating the stratigraphy of the volcanic successions and the morphology of the monogenetic eruptive centres analysis of this volcanic succession has been conducted following the unconformity bounded stratigraphic units criteria the detailed stratigraphy of the volcanic successions shows that the central garrotxa volcanic field gvf evolved through four main periods of volcanic activity synthems represented by the eruptive products of the mafic monogenetic volcanoes and associated syn eruptive reworked deposits eruptive units and by the inter eruptive deposits epiclastic units the distribution and the morphologies of the monogenetic volcanoes suggest that feeder dykes were emplaced under influence of the present stress filed and along pre existing fractures of the basement our facies analysis of the deposits and their distribution shows that migration of volcanism toward the centre of the basin was accompanied by a trend of increasing explosivity episodic hydromagmatism in central garrotxa occurred without a specific geographic locus or obvious temporal correlation finally by integrating field data with the stratigraphy extracted from water wells we determined the volume of the volcanic deposits the small average volume of products emitted during each eruptive period and the long quiescence separating them allow us to classify the gvf as a low output rate volcanic field

landslide monitoring with high resolution tilt measurements at the dollendorfer hardt landslide germany abstract to continuously monitor ground movement at the dollendorfer hardt landslide in konigswinter bonn germany a borehole and a platform tiltmeter both with a resolution of 0 1 rad were installed the station is complemented with two pressure transducers to control pore pressure and four thermistors installed at different depths precipitation data is from frankenforst manor about 2 km away the data shows clear correlation between tilt pressure and precipitation as well as daily temperature induced tilt oscillations to decompose the tilt signal we first differentiated the series three times with respect to time to separate the trend we then expanded the remaining signal into a fourier series that was truncated to cutoff signal corresponding to shorter periods than 10 days this way we separate the seasonal variation from the shorter period residual component the trend is predominantly linear amounting to a 1000 rad down slope tilt per year the residual is characterized by rainfall events we attempt to describe the tilt response to rain by a linear system with precipitation data as input and tilt signal as output the analysis shows that this model qualitatively explains several features of the tilt signal but there is also a dependence of the tilt signal on pore pressure and temperature the study shows that a continuous high resolution monitoring of slope deformation allows decomposition into different processes and is thus a reasonable basis to verify theoretical models

physical processes of shallow mafic dike emplacement near the san rafael swell utah some 200 shonkinite dikes sills and breccia bodies on the western colorado plateau of south central utah were intruded from approximately 3 7 to 4 6 ma contemporaneous with mafic volcanism along the nearby plateau margin thicknesses of dikes range to about 6 m the log normal mean thickness is 85 cm despite the excellent exposures of essentially all dikes in strata of the jurassic san rafael group their number is indeterminate from their outcrop and spacing because they are everywhere greatly segmented by our grouping of almost 2000 dike segments most dikes are less than 2 km in outcrop length the longest is 9 km because the san rafael magmas were primitive and probably ascended directly from the mantle dike lengths in outcrop are much less than their heights the present exposures probably lie along the irregular upper peripheries of dikes that lengthen and merge with depth orientations of steps on dike contacts record local directions of dike fracture propagation about half of the measurements plunge less than 30 showing that lateral propagation at dike peripheries is as important as the vertical propagation ultimately responsible for ascent the san rafael dikes now exposed after erosion of about 0 5 1 5 km appear to thicken and shorten upward probably because near surface vesiculation enhanced magmatic driving pressures propagation likely ceased soon after the first dike segments began to feed nearby sills or vented to initiate small volume eruptions most of the dikes are exposed in clastic strata of the jurassic san rafael group they probably acquired their strikes however while ascending along well developed joints in massive sandstones of the underlying glen canyon group rotation of far field stresses during the emplacement interval cannot account for disparate strikes of the dikes which vary through 110 most lying between north and n25 w rather the two regional horizontal principal stresses were probably nearly equal and so the dominant n75 e direction of dike opening was not strongly favored across the center of the swarm about 10 to 15 dikes overlap and produce 15 20 m of dilation many are in sufficient proximity that later dikes should be thinner than earlier ones if neither the magma pressures nor regional stresses were changing during the emplacement interval however dike thicknesses vary systematically neither along the length of the swarm nor in proportion to the number of neighboring dikes it appears that crustal extension during the magmatic interval relieved compressive stresses localized by intrusion

shallow plumbing systems for small volume basaltic volcanoes 2 evidence from crustal xenoliths at scoria cones and maars abstract monogenetic basaltic volcanoes record complex eruption processes and the relationships between those processes and shallow plumbing are poorly understood this paper explores these relationships building upon earlier studies of exposed shallow plumbing in the upper hundreds of meters of crust beneath volcanoes produced by magmatic eruption processes and those produced by phreatomagmatic processes such as scoria cones and maars respectively eruptive facies and xenolith abundances are described at three scoria cones and at tephra rings around two maars in the san francisco volcanic field arizona usa well constrained subvolcanic sedimentary stratigraphy provides constraints on the depths of origin of xenoliths of different types sedimentary xenolith contents at scoria cones are

arrested diatreme development standing rocks east hopi buttes navajo nation usa abstract maar diatreme volcanoes defined by their relatively large pyroclastic debris filled subsurface structures and craters that cut into the pre eruptive land surface are typically found in small volume mafic to ultramafic monogenetic volcanic fields diatremes are associated with strong explosions throughout most of their development focused along feeder dikes and generally attributed to magma water interaction or high magmatic volatiles detailed mapping of the magnificently exposed standing rocks east sre diatreme shows evidence of additional eruptive complexity and offers new insights into how the plumbing and vent structures of small volume volcanoes evolve during an eruption sre is part of a larger basanitic volcanic complex that includes several diatremes formed along a series of irregular offset nw se trending dikes exposed 300 m below the pre eruptive land surface its similarly oriented elliptical shaped diatreme structure comprises predominantly country rock lithic rich breccia of coarse inhomogeneously mixed wall rock blocks sourced from above and below the current surface plus sparse juvenile material domains of pyroclastic deposits crosscut the country rock breccia deposits and the best exposed is the nw massif rising 35 m above the current erosional surface it represents a cross section of an evolving crater floor and comprises matrix rich lapilli tuff and spatter deposits cut by irregularly distributed dikes some with very complex textures the most significant deposit in terms of volume is an unbedded lapilli tuff that is poorly sorted and has a well mixed population of wall rock and juvenile clast varieties thus resembling deposits typical of diatremes it is overlain by and locally intercalated with spatter deposits and this irregular contact demarcates the base of what was during eruption an uneven evolving crater floor the generally massive variably welded spatter deposits constitute mostly lapilli sized juvenile clasts with fluidal folded over shapes and ropy surfaces subordinate thermally altered wall rock and variegated domains of lapilli tuff sre shows a progressive transition from fissure to diatreme and overall evolution from more explosive to weakly explosive eruption styles recorded at the conduit crater transition diatreme development was initiated by deep quarrying explosive eruptions along a fissure to form the country rock rich breccia only parts of the fissure remained active as magma feeding the highly explosive eruptions along the fissure localized into discrete point sources forming the matrix rich lapilli tuff deposits these superimposed deposits record the passage of multiple debris jets and subvertical fallback from shallow cratering arising from explosions triggered by magma water interaction at numerous discrete sites however instead of continuing to build a well formed diatreme the system switched to weak spattering with intermittent explosive activity and near surface dike emplacement into the unconsolidated anisotropic pyroclastic debris of the crater floor dominant spatter from strombolian style bursts accumulated on the topographically varied evolving unstable syn eruptive crater floor and led to local failure and remobilization this study demonstrates how the combination of fissure behavior and sensitivity of the shallow plumbing system to local conditions during an eruption can lead to a decrease in eruptive footprint within the diatreme structure and an overall decrease in explosivity resulting in the arrested development of an immature diatreme

the national landslide database of great britain acquisition communication and the role of social media the british geological survey bgs is the national geological agency for great britain that provides geoscientific information to government other institutions and the public the national landslide database has been developed by the bgs and is the focus for national geohazard research for landslides in great britain the history and structure of the geospatial database and associated geographical information system gis are explained along with the future developments of the database and its applications the database is the most extensive source of information on landslides in great britain with over 17 000 records of landslide events to date each documented as fully as possible for inland coastal and artificial slopes data are gathered through a range of procedures including incorporation of other databases automated trawling of current and historical scientific literature and media reports new field and desk based mapping technologies with digital data capture and using citizen science through social media and other online resources this information is invaluable for directing the investigation prevention and mitigation of areas of unstable ground in accordance with government planning policy guidelines the national landslide susceptibility map geosure and a national landslide domains map currently under development as well as regional mapping campaigns rely heavily on the information contained within the landslide database assessing susceptibility to landsliding requires knowledge of the distribution of failures an understanding of causative factors their spatial distribution and likely impacts whilst understanding the frequency and types of landsliding present is integral to modelling how rainfall will influence the stability of a region communication of landslide data through the natural hazard partnership nhp and hazard impact model contributes to national hazard mitigation and disaster risk reduction with respect to weather and climate daily reports of landslide potential are published by bgs through the nhp partnership and data collected for the national landslide database are used widely for the creation of these assessments the national landslide database is freely available via an online gis and is used by a variety of stakeholders for research purposes

predicting the sliding behavior of rotational landslides based on the tilting measurement of the slope surface abstract the surface displacements of slopes have been considered as a significant indicator in landslide investigations in last several decades while in recent years the tilting of slope surfaces is also being recognized as an important index in landslide monitoring however the slope surface tilting has been rarely examined so far and requires detailed investigations in this paper a series of laboratory tests and a field test were performed to investigate the surface tilting in rotational landslides as well as the correlation between tilt angles and displacements of slope surfaces in the laboratory tests slope models were constructed with different shapes of pre designed slip surfaces and tested under varying test conditions the tilting behavior of the slope surfaces in laboratory tests was measured using tilt sensors embedded into the slopes while the surface displacement was obtained by tracing the movement of marked points set on the slope surfaces near to the tilt sensors the test results revealed a linear relationship between the tilt angles and displacements of slope surfaces in the process of slope failure and this linear relationship was validated by a field test in which the slope failure was triggered by artificial rainfall the test results also indicated that the coefficient of the linear relation is consistent with the value of real distance between the locations of tilt sensors and the centers of slip surfaces an equation that relates the slope surface tilting and displacements was proposed in this study furthermore a method to estimate the geometry of the slip surface was also developed which was deduced from the observation that the path of the sliding masses was parallel to the slip surface according to the results of laboratory tests additionally an acceleration stage of surface tilting was observed in slope failure induced by artificial rainfall which implies that the surface tilting measurement can be used to predict the potential development of a rotational landslide or its reactivation

geophysical monitoring of moisture induced landslides a review author s whiteley js chambers je uhlemann s wilkinson pb kendall jm abstract 2018 the authors geophysical monitoring of landslides can provide insights into spatial and temporal variations of subsurface properties associated with slope failure recent improvements in equipment data analysis and field operations have led to a significant increase in the use of such techniques in monitoring geophysical methods complement intrusive approaches which sample only a very small proportion of the subsurface and walk over or remotely sensed data which principally provide information only at the ground surface in particular recent studies show that advances in geophysical instrumentation data processing modeling and interpretation in the context of landslide monitoring are significantly improving the characterization of hillslope hydrology and soil and rock hydrology and strength and their dynamics over time this review appraises the state of the art of geophysical monitoring as applied to moisture induced landslides here we focus on technical and practical uses of time lapse methods in geophysics applied to monitoring moisture induced landslide the case studies identified in this review show that several geophysical techniques are currently used in the monitoring of subsurface landslide processes these geophysical contributions to monitoring and predicting the evolution of landslide processes are currently underrealized hence the further integration of multiple parametric and geotechnically coupled geophysical monitoring systems has considerable potential the complementary nature of certain methods to map the distribution of subsurface moisture and elastic moduli will greatly increase the predictive and monitoring capacity of early warning systems in moisture induced landslide settings

the vesicular layer and carbonate collars of desert soils and pavements formation age and relation to climate change abstract the vesicular fine grained a horizon av is the widespread ubiquitous surficial horizon of desert soils in diverse landforms and parent materials of varying ages now known to form mostly through accumulation of eolian dust recent studies show that dust accumulation and concomitant soil development are genetically linked to stone pavement formation changes in the magnitude of eolian activity and effective leaching related to quaternary climatic changes are also hypothesized to have influenced the evolution of the av horizon numerical modeling geochronologic and field laboratory studies elucidate the nature of pedogenic processes controlling compositional evolution of av how the changing av horizon increasingly influences soil infiltration and carbonate translocation and accumulation and the control that clasts of the evolving pavement exert on pedogenic processes results of a model that determines soil bulk chemical composition based on mixing of estimated proportions of externally derived eolian material and parent materials imply that the evolution of the soil bulk composition is strongly influenced by av horizon formation the early development of a weakly to moderately developed av horizon directly over gravelly parent material in late and middle holocene soils moderately influences soil infiltration but significant leaching of very soluble materials and some carbonate in dust are permitted in older pleistocene soils however the texturally more mature av and underlying cumulic nongravelly horizons more strongly limit the rate and depth of leaching and soil bulk composition therefore more closely approximates a simple mixture of dust and parent material other aspects of av horizon development and its relations to the pavement are evaluated through studies of pavement clasts with coatings of soil carbonate referred to as carbonate collars development of a numerical model that integrates soil hydrology a co2 production diffusion model calcite kinetics and thermodynamic considerations composition and thermal characteristics of pavement clasts and the textural and structural properties of the surface horizon provides the basis for testing a hypothesis of collar formation model results combined with results of 13c and 18o analyses of collar carbonate demonstrate how precipitation of calcite on pavement clasts and within the av is favored at a depth much shallower than that indicated by the classic carbonate depth climate relationship of jenny and leonard jenny h j leonard c d 1935 functional relationships between soil properties and rainfall soil science 38 363 381 and arkley arkley r j 1963 calculations of carbonate and water movement in soil from climatic data soil science 96 239 248 or simulated by numerical models of carbonate accumulation simultaneous development of thick carbonate collars and the av horizon requires the sustained pavement clast av horizon coupling for at least centuries to possibly millennia new thermoluminescence ages also indicate that much of the av horizon formed in the holocene and that it is certainly much younger than the older pleistocene pavements this supports the previously proposed hypothesis that increased dust flux during the pleistocene to holocene transition triggered and or greatly accelerated av horizon development an understanding of the genesis of collars provides not just an understanding of how carbonate can accumulate in surface environments but it also provides important clues into processes of pavement evolution and preservation of av horizons during long glacial periods the av horizon is not merely an insignificant surficial zone of recent dust accretion instead its development profoundly influences the genesis of desert soils and pavements

the auckland volcanic field new zealand geophysical evidence for structural and spatio temporal relationships abstract geophysical data from the monogenetic auckland volcanic field reveal complex structural and spatio temporal relationships at different scales the volcanic field is coincident with regional magnetic and gravity anomalies that mark a major crustal suture and with a discontinuity marking a significant structural asperity here the linear regional magnetic anomaly splays into a wide band of nnw trending lineaments arising from serpentinised shear zones in the upper crust that matches the extent of the volcanic field and that may reflect a region of crustal weakness creating preferential permeability however there appears to be no simple correlation between the locations of individual vents and these lineaments that might delineate more shallow structural controls with this orientation probably as a consequence of other structural influences high resolution aeromagnetic data over the volcanic field show that the volcanoes have a wide range of magnetic signatures indicating a variability of subsurface structure scoria cone volcanoes typically have strong anomalies up to several 100 nt whilst tuff ring volcanoes typically have weak anomalies less than 50 nt though the surface geology is not always an indicator of the nature and extent of the subsurface deposits both cone and tuff ring volcanoes in the auckland field appear to be underlain by subsurface bowl shaped bodies of basalt implying that their eruption histories commonly involve lava ponding into early excavated craters the present geophysical data give no evidence for subsurface dyke like structures or for substantial near surface volumes of basaltic rocks where there are no known eruption centres or buried flows aeromagnetic and palaeomagnetic data suggest that a number of adjacent vents with an implied structural linkage may be contemporaneous though other examples occur where vents of clearly different ages exploit the same apparent structure a unique feature of the auckland field is that at least 5 widely separated and structurally unrelated volcanoes are contemporaneous these observations highlight the spatial and temporal heterogeneities that can occur in monogenetic fields and have an important bearing on recurrence rates and temporally linked eruptions which are probably more common than is generally supposed and are key factors in statistically based hazard assessments

clast size controls and longevity of pleistocene desert pavements at lathrop wells and red cone volcanoes southern nevada formation of desert pavement and accretionary soils are intimately linked in arid environments well sorted fallout scoria lapilli at lathrop wells 75 80 ka and red cone ca 1 ma volcanoes southern nevada formed an excellent parent material for pavement allowing infiltration of eolian silt and fine sand that first clogged the pore space of underlying tephra and then aggraded and developed vesicular a av horizons variations in original pyroclast sizes provide insight into minimum and maximum clast sizes that promote pavement and soil formation pavement becomes ineffective when clasts can saltate under the strongest winds while clasts larger than coarse lapilli are unable to form an interlocking pavement that promotes silt accumulation necessary for av development contrary to predictions that all pavements above altitudes of 400 m would have been reset in their development after late pleistocene vegetation advances the soils and pavements show clear differences in maturity between the two volcanoes this indicates that either the pavements and or soils develop slowly over many tens of thousands of years and then are very stable or if they are disrupted by vegetation advances subsequent pavements are re established with successively more mature characteristics

modeling magma drift interaction at the proposed high level radioactive waste repository at yucca mountain nevada usa we examine the possible ascent of alkali basalt magma containing 2 wt percent water through a dike and into a horizontal subsurface drift as part of a risk assessment for the proposed high level radioactive waste repository beneath yucca mountain nevada usa on intersection of the dike with the low pressure horizontal drift the ascending magma will be diverted into the drift the fragmenting mixture expands down the drift to reach speeds of order 100 300 m s after this initial disruptive activity parts of the repository can be filled with magma within a matter of hours until a pathway is found to allow the magma to vent magma flow through the drift network will cause intense heating of any waste canisters located along the pathway between the dike and the surface conduit the assessments suggest a greater number of waste packages may be adversely affected than previously recognized

jointly reconstructing ground motion and resistivity for ert based slope stability monitoring author s boyle a wilkinson pb chambers je meldrum pi uhlemann s adler a abstract the authors 2017 published by oxford university press on behalf of the royal astronomical society electrical resistivity tomography ert is increasingly being used to investigate unstable slopes and monitor the hydrogeological processes within but movement of electrodes or incorrect placement of electrodes with respect to an assumed model can introduce significant resistivity artefacts into the reconstruction in this work we demonstrate a joint resistivity and electrode movement reconstruction algorithm within an iterative gauss newton framework we apply this to ert monitoring data from an active slow moving landslide in the uk results show fewer resistivity artefacts and suggest that electrode movement and resistivity can be reconstructed at the same time under certain conditions a new 2 5 d formulation for the electrode position jacobian is developed and is shown to give accurate numerical solutions when compared to the adjoint method on 3 d models on large finite element meshes the calculation time of the newly developed approach was also proven to be orders of magnitude faster than the 3 d adjoint method and addressed modelling errors in the 2 d perturbation and adjoint electrode position jacobian

influences of eolian and pedogenic processes on the origin and evolution of desert pavements well developed desert pavements are present above eolian deposits that mantle flows of the cima volcanic field located in the mojave desert california soil stratigraphic data and geochemical data demonstrate that eolian and pedogenic processes play major roles in the evolution of these pavements eolian dust 1 accelerates mechanical fragmentation of flow rock providing the source material for pavements and 2 accumulates slowly below basaltic colluvium in flow depressions eventually promoting development of cumulate soils below the evolving stone pavement an increase in dust flux during the holocene has raised ancient pleistocene pavements as much as 20 cm above the former land surface the results of our studies demonstrate for the first time that most desert pavements do not form by deflation by overland flow or by upward migration of stones through a slowly formed clayey argillic horizon desert pavements are born and maintained at the surface

multiphase magmatic flows at yucca mountain nevada 1 the proposed yucca mountain radioactive waste repository is sited in southern nevada in a region that has experienced sporadic basaltic volcanism since the late miocene volcanic risk assessment for the proposed repository requires estimating the consequences of a new monogenetic volcano intersecting the underground facility during its 104 106 year performance period we report numerical studies aimed at understanding the range of processes and dynamic parameter values that could accompany intersection of an open repository drift by a volatile rich trachybasaltic magma as it ascends in a dike we focus on one end member type of magmatic behavior namely a fragmented magmatic mixture under pressure interacting with an underground cavity initial and boundary conditions are based upon field data and previous modeling studies of the interaction between vertically propagating dikes and a repository opening the calculations are two dimensional and time dependent and are conducted with the multiphase hydrodynamics code gmfix calculations indicate that gas particle mixtures as they rise from below and interact with horizontal openings form complex flow patterns involving varying degrees of recirculation and deposition of pyroclasts dynamic pressures are up to 106 pa but are more typically on the order of 103 to 104 pa the geometry and number of outlets play a key role in determining the types of flow patterns as do volatile contents and the degree of fragmentation the detailed numerical simulations provide information that will be used to confirm the adequacy of simplified probabilistic consequence models used in risk assessments

assessing tephra total grain size distribution insights from field data analysis abstract the total grain size distribution tgsd of tephra deposits is crucial for hazard assessment and provides fundamental insights into eruption dynamics it controls both the mass distribution within the eruptive plume and the sedimentation processes and can provide essential information on the fragmentation mechanisms tgsd is typically calculated by integrating deposit grain size at different locations the result of such integration is affected not only by the number but also by the spatial distribution and distance from the vent of the sampling sites in order to evaluate the reliability of tgsds we assessed representative sampling distances for pyroclasts of different sizes through dedicated numerical simulations of tephra dispersal results reveal that depending on wind conditions a representative grain size distribution of tephra deposits down to 100 m can be obtained by integrating samples collected at distances from less than one tenth up to a few tens of the column height the statistical properties of tgsds representative of a range of eruption styles were calculated by fitting the data with a few general distributions given by the sum of two log normal distributions bi gaussian in units the sum of two weibull distributions and a generalized log logistic distribution for the cumulative number distributions the main parameters of the bi lognormal fitting correlate with height of the eruptive columns and magma viscosity allowing general relationships to be used for estimating tgsd generated in a variety of eruptive styles and for different magma compositions fitting results of the cumulative number distribution show two different power law trends for coarse and fine fractions of tephra particles respectively our results shed light on the complex processes that control the size of particles being injected into the atmosphere during volcanic explosive eruptions and represent the first attempt to assess tgsd on the basis of pivotal physical quantities such as magma viscosity and plume height our empirical method can be used to assess the main features of tgsd necessary for numerical simulations aimed to real time forecasting and long term hazard assessment when more accurate field derived tgsds are not available

volcanic geomorphological classification of the cinder cones of tenerife canary islands spain this paper proposes a method to establish a morphological classification of tenerife s cinder cones on the basis of a dual analysis of qualitative existence geometry and disposition of craters and quantitative morphometric parameters major and minor diameters and cone elongation major and minor diameters and crater elongation the result obtained is a morphological classification of the cinder cones of tenerife which can be sub divided into four types ring shaped cones horseshoe shaped volcanoes multiple volcanoes and volcanoes without crater in tenerife there is a clear dominance of horseshoe shaped volcanoes 69 0 over ring shaped cones 13 1 volcanoes without craters 11 4 and multiple volcanoes 6 4 the classification presented in this paper is characterized by its simplicity which makes it possible to include all morphological types of volcanoes found in tenerife this fact also renders our classification a useful tool to apply in other both insular and continental volcanic areas to eventually analyze and systematize the study of eruptive edifices with similar traits

quantification of landslide velocity from active waveguide generated acoustic emission acoustic emission ae has become an established approach to monitor stability of soil slopes however the challenge has been to develop strategies to interpret and quantify deformation behaviour from the measured ae ae monitoring of soil slopes commonly utilizes an active waveguide that is installed in a borehole through the slope and comprises a metal waveguide rod or tube with a granular backfill surround when the host slope deforms the column of granular backfill also deforms and this generates ae that can propagate along the waveguide results from the commissioning of dynamic shear apparatus used to subject full scale active waveguide models to simulated slope movements are presented the results confirm that ae rates generated are proportional to the rate of deformation and the coefficient of proportionality that defines the relationship has been quantified e g 4 4 105 for the angular gravel examined it is demonstrated that slope velocities can be quantified continuously in real time th

early time multiphase interactions between basaltic magma and underground openings at the proposed yucca mountain radioactive waste repository 1 we investigate the interaction between yucca mountain repository drifts horizontal emplacement tunnels and a hawaiitic magma in three scenarios 1 a single feeder dike that extends above an intersected drift 2 same as 1 but with an additional secondary dike extending upward from the drift 3 same as 1 with the drift initially filled with pyroclasts and gas under high pressure which is then decompressed as might happen if some blockage is rapidly removed in the volcanic system above the drift our results indicate that the drift is likely to experience dynamic pressure waves from expansion of rising magma and subsequent pyroclastic flows with a maximum possible dynamic pressure of 107 pa a secondary dike above the drift has negligible effects upon the flow dynamics in the third scenario particles settle fairly quickly along the floor of the drift suggesting that a swift decompression within the drift will not be able to remove all the magmatic materials

determination of the internal structure of alpine talus deposits using different geophysical methods lechtaler alps austria abstract the total thickness and structure of alpine talus accumulations were investigated in a study area in the northern alps using ground penetrating radar gpr completed by 2d geoelectric ert and seismic refraction soundings the loose steep talus cones of the parzinn cirque are situated at an elevation of 2100 2300 m a s l and end downslope at late glacial protalus ramparts the surrounding rockwalls consist of hauptdolomit a brittle dolostone in most of the gpr profiles the bedrock surface was clearly recognizable from the radargrams total talus thicknesses of up to 45 m were estimated the uppermost talus layer is characterized by surface parallel radar reflection patterns intermediate resistivities 4 10 k m and low seismic velocities 400 500 m s these deposits are interpreted as stratified debris built up during the holocene by rockfall deposits occasionally resorted by debris flows below this unit a zone of more irregular radar reflection patterns and enhanced electrical resistivities follows the combined results lead to the assumption of very coarse grained paraglacial rockfall deposits or to a core of basal moraine beneath the talus some zones of especially high resistivity 25 k m may be related to sporadic permafrost occurrence in the depressions between the talus and the moraine ridges striped radar structures are also recognizable in the moraine bodies the stratified sediments give evidence for glaciofluvial transport or debris flows as an agent of protalus rampart formation however these features probably result from a combination of different processes including periglacial creep gpr turned out to be a powerful tool for the determination of debris volumes and internal structures however supporting geoelectric and seismic investigations are advisable to validate the results and to facilitate and improve the interpretation the results point to an average holocene rockwall retreat of 500 to 800 mm ka which is roughly three times higher than recent backweathering rates

evaluating suitability of a tephra dispersal model as part of a risk assessment framework in volcanic risk assessment it is necessary to determine the appropriate level of sophistication for a given predictive model within the contexts of multiple sources of uncertainty and coupling between models a component of volcanic risk assessment for the proposed radioactive waste repository at yucca mountain nevada usa involves prediction of dispersal of contaminated tephra during violent strombolian eruptions and the subsequent transport of that tephra toward a hypothetical individual via surface processes we test the suitability of a simplified model for volcanic plume transport and fallout tephra deposition ashplume coupled to a surface sediment transport model far that calculates the redistribution of tephra and in light of inherent uncertainties in the system the study focuses on two simplifying assumptions in the ashplume model 1 constant eruptive column height and 2 constant wind speed and direction during an eruption variations in tephra dispersal resulting from unsteady column height and wind conditions produced variations up to a factor of two in the concentration of tephra in sediment transported to the control population however the effects of watershed geometry and terrain which control local remobilization of tephra overprint sensitivities to eruption parameters because the combination of models used here shows limited sensitivity to the actual details of ash fall a simple fall model suffices to estimate tephra mass delivered to the hypothetical individual

the role of recent tectonics and hydrological processes in the evolution of recurring landslides on the danube s high bank in dunafoldvar hungary abstract there are high loess banks prone to landslide along the river danube in hungary one of these is the high loess bank in dunafoldvar where several landslides occurred in the last decades quantitative relationships between the movements of the high loess bank and the variation of the water level of the river danube the ground water table precipitation and temperature are investigated by two borehole tiltmeters and a vertical borehole extensometer the twelve year long observation from 2002 to 2014 made it possible to distinguish between the high bank movements due to slow recent tectonic and geomorphologic processes and the short period from hours to months movements caused by hydrometeorological effects the results revealed that besides geomorphologic processes recent tectonics can play an important role in the recurrence of landslides in the area in the investigated period the total tilt of the high bank was 162 rad in the sse direction according to the geomorphologic and recent tectonic processes in the surroundings of dunafoldvar investigations of the relationships between the high bank movements and the water level of the river danube ground water table changes and the precipitation revealed that the tilt magnitudes caused by the ground water table variations are two orders of magnitude greater than the tilts caused by the water level regime of the river and the direct effect of the precipitation on the high bank tilts can be disregarded

decreasing magmatic footprints of individual volcanoes in a waning basaltic field the distribution and characteristics of individual basaltic volcanoes in the waning southwestern nevada volcanic field provide insight into the changing physical nature of magmatism and the controls on volcano location during pliocene pleistocene times the volumes of individual volcanoes have decreased by more than one order of magnitude as have fissure lengths and inferred lava effusion rates eruptions evolved from hawaiian style eruptions with extensive lavas to eruptions characterized by small pulses of lava and strombolian to violent strombolian mechanisms these trends indicate progressively decreasing partial melting and length scales or magmatic footprints of mantle source zones for individual volcanoes the location of each volcano is determined by the location of its magmatic footprint at depth and only by shallow structural and topographic features that are within that footprint the locations of future volcanoes in a waning system are less likely to be determined by large scale topography or structures than were older larger volume volcanoes

biogeomorphological influence of slope processes and sedimentology on vascular talus vegetation in the southern cascades california abstract the vascular vegetation of alpine talus slopes between 2035 and 3095 m altitude was studied at lassen volcanic national park california in the cascade range taluses show a diverse flora with 79 plant species growth forms include coniferous trees shrubs suffrutices herbs graminoids and ferns spatial patterns of plant distribution were studied along 40 point intercept transects plant cover was low 0 32 7 on all slopes spatially variable and showed no consistent trends sedimentological characteristics were determined by photosieving next to 1500 plants this census indicated preferential plant growth on blocks and cobbles with 43 2 and 23 3 of the plants growing on these stones respectively fewer specimens were rooted on pebbles 13 or on stone free gravel areas 20 5 growth forms displayed different substrate preferences 92 5 of the shrubs and 83 of the suffrutices colonized blocks or cobbles but only 57 2 of the herbs and 59 8 of the graminoids grew on large stones plants are associated with large clasts because 1 coarse talus is more stable than fine sediment areas which are more frequently disturbed by various geomorphic processes and 2 large stones help conserve substrate water beneath them while moisture quickly evaporates from fine debris root patterns were studied for 30 plant species 10 specimens for each species were excavated and inspected and several root growth ratios calculated all species exhibited pronounced root asymmetry as roots for most plants grew upslope from their shoot base for 23 species all specimens had 100 of their roots growing upslope for the other 7 species 92 2 99 3 of below ground biomass extended uphill this uneven root distribution is ascribed to continual substrate instability and resulting talus shift as cascading debris progressively buries roots and stems plants are gradually pushed and or stretched downhill various disturbance events affect root development slope erosion following rubble removal often exposes plant roots debris deposition can completely bury plants some may survive sedimentation producing new shoots that grow through accumulated debris shrubs may propagate by layering as adventitious roots develop along buried stems or produce new clones along their roots slope processes may damage and transport plant pieces downhill some species can sprout from severed displaced root or stem fragments vegetation interacts with several geomorphic processes including debris flows grain flows rockfall snow avalanches frost creep and runoff larger plants may alter local patterns of debris movement and deposition damming cascading debris on their upslope side and deflecting sediments laterally to plant margins where they form narrow elongated stone stripes

correlation of acoustic emissions with patterns of movement in an extremely slow moving landslide at peace river alberta canada the peace river region alberta canada has experienced extensive landslide activity since deglaciation shear zones within weak lacustrine silt and clay layers typically experience continuous cre

global patterns of loss of life from landslides global loss of life from landslides is poorly quantifi ed a global data set of fatalities from nonseismically triggered landslides that resulted in loss of life between a d 2004 and 2010 permits for the fi rst time proper quantifi cation of impacts and spatial distributions in total 2620 fatal landslides were recorded worldwide during the 7 yr period of the study causing a total of 32 322 recorded fatalities these total numbers of landslides and victims are an order of magnitude greater than other data sets have indicated but analysis of the data suggests that it may still slightly underestimate the true human costs the majority of human losses occur in asia especially along the himalayan arc and in china this geographical concentration dominates the annual landslide cycle which peaks in the northern hemisphere summer months finally numbers of fatalities per event show a fat tailed power law distribution with the density of landslides being moderately correlated with the population density on a national basis

four dimensional imaging of moisture dynamics during landslide reactivation landslides pose significant risks to communities and infrastructure and mitigating these risks relies on understanding landslide causes and triggering processes it has been shown that geophysical surveys can significantly contribute to the characterization of unstable slopes however hydrological processes can be temporally and spatially heterogeneous requiring their related properties to be monitored over time geoelectrical monitoring can provide temporal and volumetric distributions of electrical resistivity which are directly related to moisture content to date studies demonstrating this capability have been restricted to 2d sections which are insufficient to capture the full degree of spatial heterogeneity this study is the first to employ 4d i e 3d time lapse resistivity imaging on an active landslide providing long term data three years highlighting the evolution of moisture content prior to landslide reactivation and showing its decline post reactivation crucially the time lapse inversion methodology employed here incorporates movements of the electrodes on the unstable surface although seasonal characteristics dominate the shallow moisture dynamics during the first two years with surficial drying in summer and wetting in winter in the months preceding reactivation moisture content increased by more than 45 throughout the slope this is in agreement with independent data showing a significant rise in piezometric heads and shallow soil moisture contents as a result of prolonged and intense rainfall based on these results remediation measures could be designed and early warning systems implemented thus resistivity monitoring that can allow for moving electrodes provides a new means for the effective mitigation of landslide risk

the micromorphology of unconsolidated sediments this paper aims to describe the use of thin sections micromorphology in the sedimentology of unconsolidated sediments it provides examples of the use of thin sections in a variety of sedimentary environments from fault gouge through caves and volcanics to aeolian fluviatile marine periglacial and glacial it demonstrates that in the latter three fields the use of micromorphology is relatively widespread and that in glacial sedimentology it has revolutionised our way of thinking about subglacial sediments although micromorphology has been mainly descriptive so far methods of quantification observations are demonstrated some of the important aspects of micromorphology are its use for microstratigraphy and the possibility of relating observations to documented processes thereby allowing a more robust sedimentological interpretation of modern and ancient sediments

eruptive styles and inferences about plumbing systems at hidden cone and little black peak scoria cone volcanoes nevada u s a we describe two small scoria cone volcanoes hidden cone and little black peak ages between 320 390 ka in the southwestern nevada volcanic field and discuss their eruption mechanisms and inferences about their plumbing systems cone forming pyroclastic deposits are consistent with eruptive styles ranging from strombolian to violent strombolian and lavas emanated from near the bases of the cones the volcanoes are monogenetic rather than polycyclic as allowed by previous geomorphic interpretations vents at each volcano appear to coincide with pre existing normal faults consistent with observations at older deeply eroded volcanoes in the region the existence of these two volcanoes on a topographically high area particularly hidden cone provides evidence for short feeder dike lengths 500 m at the surface we infer that this short length reflects the small length scale of the mantle source region that was tapped to feed each volcano

shallow plumbing systems for small volume basaltic volcanoes eruptive dynamics in basaltic volcanoes are controlled in part by the conduit geometry however uncertainties in conduit shape and dike to conduit transition geometry have limited our predictive capability for hazards assessments we characterize the subvolcanic geometry of small volume basaltic volcanoes magmatic volatile driven eruptions 0 1 to 0 5 km3 based on a synthesis of field studies of five basaltic volcanoes exposed to varying degrees by erosion and exhibiting feeder dikes conduits and vent areas 250 m depth study areas include east grants ridge new mexico usa basalt ridge east basalt ridge paiute ridge and southeast crater flat nevada usa basaltic feeder dikes 250 to 100 m deep have typical widths of 4 12 m with smooth host rock contacts rhyolite tuff at depths less than 100 m heterogeneities in the host rock form preferential pathways for small dike splays and sills resulting in a 30 m effective width at 50 m depth the development of a complex conduit at depths less than 70 m is reflected in bifurcating dikes and brecciation and incorporation of the country rock the overall zone of effect at depths less than 50 m is 110 m wide 220 m elongated along the feeder dike based on comparisons with theoretical conduit flow models the width of the feeder dike at depths from 250 to 500 m is expected to range from 1 to 10 m and is expected to decrease to about 1 2 m at depths greater than 500 m the flaring shape of the observed feeder systems is similar to results of theoretical modeling using lithostatic pressure balanced flow conditions sizes of observed conduits differ from modeled dimensions by up to a factor of 10 in the shallow subsurface 50 m depth but at depths greater than 100 m the difference is a factor of 2 to 4 this difference is primarily due to the fact that observed eroded conduits record the superimposed effects of multiple eruptive events while theoretical model results define dimensions necessary for a single steady eruption phase the complex details of magma host rock interactions observed at the study areas contact welding brecciation bifurcating dikes and sills and stoping represent the mechanisms by which the lithostatic pressure balanced geometry is attained the similarity in the normalized shapes of theoretical and observed conduits demonstrates the appropriateness of the pressure balanced modeling approach consistent with the conclusions of wilson and head j geophys res 86 2971 3001 1981 for this type of volcano

some mudslide movement patterns a study has been made of the mechanisms of movement in a mudslide and the interrelationships between the controlling variables detailed monitoring has been conducted on a mudslide developed in the wealden beds a cretaceous mudrock the parameters which govern mudslide instability have been continuously monitored using electronic datalogging techniques slip can be divided into four components small multiple stick slip movements which are grouped temporally gradual or graded slip within defined temporal limits rapid surge events which occur over a short time interval and involve large displacements and unexplained random movements each of these four components occurs with varying frequency and at different times in the seasonal record slip is usually separated by periods of little or no change each component of mudslide movement displays characteristic patterns of pore water pressure change

thermoluminescence dating of the british coversand deposits abstract coversand deposits thought to be of lateglacial age are found in britain in north lincolnshire south west lancashire and central east anglia a comprehensive dating study of them using thermoluminescence tl techniques is currently underway in an attempt to link the british coversand deposits to the european coversand chronology initial results from four of the british coversand sites sampled are presented the 26 tl dates from 14 samples show that in lincolnshire aeolian deposition took place from 12 5 ka to i1 ka cessation of the initial sand deposition was synchronous with this in lancashire but sand deposition occurred significantly earlier in east anglia the upper layers of aeolian sand in lancashire are much younger and are attributed to holocene reworking on the basis of these dates lincolnshire and lancashire coversand deposition occurred at a similar time to the younger coversand ii whilst east anglian coversand deposition coincided with the younger coversand i phase in the european coversand chronology

volcano load control on dyke propagation and vent distribution insights from analogue modeling 1 the spatial distribution of eruptive vents around volcanoes can be complex and evolve as a volcano grows observations of vent distribution at contrasting volcanoes from scoria cones to large shields show that peripheral eruptive vents concentrate close to the volcano base we use analogue experiments to explore the control of volcano load on magma ascent and on vent location results show that the local loading stress field favors eruption of rising magma away from the volcano summit if a central conduit is not established or is blocked two sets of scaled experiments are developed with contrasting rheological properties to analyze similarities and differences in simulated magma rise below a volcano 1 golden syrup magma analogue is injected into a sand plaster mixed layer crust analogue under a cone 2 water or air magma analogues is injected into gelatin under a sand cone rising dykes approaching the cone stress field are stopped by the load compressive stress with continued intrusion dyke overpressure builds up dykes extend laterally until their tips are able to rise vertically again and to erupt in the flank or at the base of the volcano lateral offset of the extrusion point relative to the edifice summit depends on substratum thickness volcano slope and dyke overpressure the 3d geometry of golden syrup intrusions varies with experimental parameters from cylindrical conduits to dyke and sill complexes experimental results are compared with illustrative field cases and with previously published numerical models this comparison enables applications and limitations of the analogue models to be highlighted and allows us to propose a conceptual model for the evolution of vent distribution with volcano growth

a comprehensive framework of tdr landslide monitoring and early warning substantiated by field examples abstract due to the climate change and hazardous geological environment in taiwan real time landslide monitoring for safety of adjacent tribes or infrastructures is much conspicuous time domain reflectometry tdr is considered as valuable technology for continuously capturing dynamics and locations of shear deformations with high temporal and spatial coverages in this study a comprehensive framework was proposed by integrating up to date procedure of installation guide data acquisition sliding deformation identification and early warning processing the advantages of the proposed framework were then examined and substantiated via field cases the first case is at a large colluvium slope in lushan central taiwan the colluvium is still active after heavy rainfall events but limited evidence of sliding characteristic was collected previously by manual inclinometer logging therefore the tdr framework was deployed and multiple landslide surfaces at great depths were timely observed movement of colluvium mass was thereby interpreted as a buckling fold additionally creep occurred among the colluvium layer during the monsoon season because of strength weakening influenced by pore pressure fluctuations monitoring results of the second landslide case in jufan northern taiwan reported the dynamics of a thin sliding plane captured with tdr high temporal resolution this unique behavior was further applied for devising of a novel early warning strategy in terms of time variation of tdr response validating that the comprehensive framework of tdr landslide can effectively contribute to early warning

three dimensional geophysical anatomy of an active landslide in lias group mudrocks cleveland basin uk a geoelectrical investigation of a slow moving earth slide earth flow in lower jurassic lias group rocks of the cleveland basin uk is described these mudrock slopes are particularly prone to failure and are a major source of lowland landslides in the uk but few attempts have been made to spatially or volumetrically characterise the subsurface form of these slides the primary aim of this study was to consider the efficacy of fully three dimensional geoelectrical imaging for landslide investigation with reference to a geological setting typical of lias group escarpments the approach described here included a reconnaissance survey phase using two dimensional electrical resistivity tomography ert resistivity mapping self potential sp profiling and mapping followed by a detailed investigation of an area of the landslide using three dimensional 3d ert and self potential tomography spt interpretation of the geophysical data sets was supported by surface observations aerial lidar and differential gps geomorphological surveys and intrusive investigations boreholes and auger holes the initial phase of the study revealed the existence of a strong sp signature at the site consistent with a streaming potential source and established the relationships between the main geological units the geomorphologic expression of the landslide and the resistivity of the materials in and around the study area the 3d spt model generated during the second phase of the study indicated drainage patterns across the landslide and preferential flow from the low permeability mud rocks into the underlying more permeable sandstone formation because of favourable resistivity contrasts between the clay rich whitby mudstone formation landslide material and the underlying staithes sandstone formation the volumetric 3d ert image allowed a number of surface and subsurface landslide features to be identified and spatially located these included the lateral extent of slipped material and zones of depletion and accumulation the surface of separation and the thickness of individual earth flow lobes and the dipping in situ geological boundary between the whitby mudstone and staithes sandstone bedrock formations