model test study on monitoring dynamic process of slope failure through spatial sensor network landslides represent a major type of natural hazards worldwide for development of risk mitigation capabilities an effective system for monitoring dynamic process of slope failure capable of gathering spatially distributed information before during and after a landslide occurrence at real time manner is essential a spatial sensor network ssn which integrates the real time communication infrastructure and observations from in situ sensors and remote sensing platforms offers an efficient and effective approach for such purpose in this paper a ssn based landslide monitoring system was designed and evaluated through a model test study conducted at tongji university china this system munold multi sensor network for observing landslide disaster has been designed as a comprehensive monitoring framework including sensor observations multi channel wireless communication remote data storage visualization data processing and data analysis in this model test study initial experimentation demonstrated the capabilities of the munold system for collecting real time information about the dynamic process and propagation of slope failure innovatively generated from the high speed stereo images the sequential surface deformation vector field can be created and may exhibit the dynamic process during the extremely critical and short period of the slope failure after this model test study the munold system is going to be further improved and extended in a landslide prone region in sichuan province china

a kinematic method for calculating shear displacements of landslides using distributed fiber optic strain measurements abstract deformation monitoring of landslides is of great significance to characterize and understand their evolutions recently the distributed fiber optic strain sensing dfoss technique has emerged as a powerful tool for landslide monitoring by enabling distributed and real time measurement along a sensing optical fiber sof over dozens of kilometers with high strain accuracy however the correlation between landslide displacements and axial strains exerted on an sof remains elusive here we present a preliminary attempt to calculate shear displacements of landslides based on distributed strain measurements via a kinematic method parametric studies on the sliding direction width of shear zone and magnitude of shear displacement indicate that under certain circumstances the shear displacements of a landslide can be well estimated without going much deep into the pattern of shear zone or the slope mass sof coupling condition the proposed calculation method is validated through field shear tests of geologic granular materials and has immediate application to the analysis of the majiagou landslide three gorges reservoir region china the distributed strain measurements captured by a borehole embedded sof allow two sliding surfaces of this landslide to be located one occurred at the contact between surface deposits and bedrock whereas the other was the main sliding surface occurring within bedrock the shear displacements along the main sliding surface are calculated using the proposed method it is revealed that the landslide responds more aggressively to the fluctuation of reservoir water level than to the rainfall over a 1 year period

the bouma division a and the possible duration of turbidity currents abstract experimental data arnott and hand 1989 combined with theoretical arguments suggest that the transition in a turbidite from division a to division b occurs at a deposition rate of unsupported grains of about 6 7 10 4 m s 1 in the case of fine medium quartz sand a second rate may be calculated from properties measured at the transition from division b to division c allen 1971b these rates together permit an estimate to be made of the order of magnitude of the duration of deposition from a turbidity current the calculated order of a few tens of minutes for a mio pliocene turbidite described and interpreted hydraulically by komar 1985 is in broad agreement with his independent estimate based on the sequenc of sedimentary structures

tsunami generation by a rapid entrance of pyroclastic flow into the sea during the 1883 krakatau eruption indonesia 1 the 1883 eruption of krakatau volcano in indonesia was one of the most explosive volcanic events in history it was a marine caldera forming eruption that resulted in voluminous ignimbrite deposits and huge tsunamis we have used numerical simulations to investigate three major mechanisms for tsunami generation caldera collapse phreatomagmatic explosion and pyroclastic flow and have constrained the source parameters computed tsunami characteristics for each hypothesis are compared with observations at locations along the coasts of the sunda strait where tsunami data were obtained immediately after the eruption for the pyroclastic flow hypothesis two types of two layer shallow water models dense and light type models were used under different initial conditions pyroclastic flows are erupted from a circular source following a sine function that assumes waning and waxing phases caldera collapse was performed using a simple piston like plunger model in which collapse duration was assumed to be up to 1 h the phreatomagmatic explosion hypothesis was examined using simple empirical models for underwater explosions in shallow water with explosion energy between 1016 and 1017 j the results show that when a pyroclastic flow with a volume of 5 km3 and an average discharge rate of the order of 107 m3 s enters the sea the computed tsunami heights are broadly consistent with historical records in coastal areas including a tide gauge record at batavia now jakarta we conclude that a pyroclastic flow entering the sea is the most plausible mechanism of the 1883 krakatau tsunami

may 18 1980 mount st helens deposits in south coldwater creek washington beginning at 0832 pacific daylight time pdt mount st helens washington produced a rockslide debris avalanche and a lateral explosion blast that generated a laterally directed pyroclastic surge called here a blast surge the resulting deposits are thickest in the east west trending valley of north fork toutle river immediately north of the volcano but are almost as thick in south coldwater creek a small tributary of the toutle river in the lee of an east west trending ridge johnston ridge just north of the north fork toutle river the avalanche surmounted johnston ridge 300 m relief and flowed down the valley of south coldwater creek closely following the avalanche and in part contemporaneously with it the blast surge left thin up to 0 5 m deposits on johnston ridge and thick up to 15 m deposits in south coldwater creek these deposits have a lower layer layer a1 which is friable massive poorer in fines particles 1 16 mm and more poorly sorted than the upper layer layer a2 layer a2 is less friable because it contains more silt and clay sized material beneath layer a1 is a zone containing a small percentage of debris from the blast surge mixed with products eroded from the underlying surface this zone designated as layer a0 is a poorly mixed layer containing schlieren of soil shattered volcanic fragments and considerable quantities of organic material layer a1 is strongly sorted and fines depleted and is interpreted to have been deposited from just behind the turbulent head of the blast surge layer a2 is interpreted to have been deposited from the body of the blast surge which is believed to have been less turbulent than the head layer a0 is interpreted to have formed by shearing at the base of the head of the blast surge in the region between the front and the back of the head of the blast surge it is concluded that a strongly fines depleted basal layer of a pyroclastic flow or surge deposit underlain by a thin sheared zone is the signature of an extremely high velocity particulate density current

submarine pyroclastic deposits formed at the soufriere hills volcano montserrat 1995 2003 what happens when pyroclastic flows enter the ocean the soufriere hills volcano montserrat west indies has undergone a series of dome growth and collapse events since the eruption began in 1995 over 90 of the pyroclastic material produced has been deposited into the ocean sampling of these submarine deposits reveals that the pyroclastic flows mix rapidly and violently with the water as they enter the sea the coarse components pebbles to boulders are deposited proximally from dense basal slurries to form steep sided near linear ridges that intercalate to form a submarine fan the finer ash grade components are mixed into the overlying water column to form turbidity currents that flow over distances 30 km from the source the total volume of pyroclastic material off the east coast of montserrat exceeds 280 106 m3 with 65 deposited in proximal lobes and 35 deposited as distal turbidites

an overview of lava dome evolution dome collapse and cyclicity at soufriere hills volcano montserrat 2005 2007 1 the third episode of lava dome growth at soufriere hills volcano montserrat was characterised by higher average magma discharge rates than either previous dome growth episode at this volcano and yet fewer collapses during sustained dome growth at moderate high average rates 6 m3 s we identified 2 6 week discharge pulses that each supplied c 20 mm3 magma from depth our observations are consistent with some existing models but we explain discrepancies by a combination of higher volatile contents and higher ascent rates cycles of c 11 16 days were evident in rockfall lp rockfall and shallow lp earthquake counts related to dome growth and degassing we speculate that degassing at the conduit margins together with stick slip conduit flow may drive these cycles only one major collapse 10 mm3 occurred during the third episode on may 20 2006 as a new magma pulse entered the dome and coincided with heavy rainfall

characteristics of the displacement of a landslide with shallow sliding surface in a heavy snow district of japan the displacement of a landslide with shallow sliding surface in a heavy snow district was automatically monitored for over 4 years by a newly developed displacement gauge meteorological properties meltwater and or rainfall mr water equivalent of snow and other factors were simultaneously observed pore water pressure was monitored but only for a limited period of time since the displacement of the landslide was too large statistical analyses showed that maximum daily displacements of each year were observed not in snow melting periods but immediately before or at the beginning of a snow cover period there are three types of annual variation pattern with peaks in mid november to mid december mid april and mid july the variation pattern of displacement from the beginning of march to the beginning of june showed the least total displacement of those three types therefore snow cover is likely to affect the displacement of a landslide detailed investigation of the landslide displacement during snow cover periods showed that the rate of displacement slowed as the snow cover deepened meaning a decrease in mr and increase in water equivalent of snow the displacement ratio for the unit antecedent mr effect during snow cover periods dropped when the snow started to accumulate on the ground in all 4 years the reduction was likely attributable to snow load since it was found to have a negative logarithmic relation with the water equivalent of snow changes in pore water pressure and the relationship between pore water pressure and displacement during the snow cover periods differed from those in the other periods therefore the displacement of a landslide that has a shallow sliding surface in a snowy region was considered to be affected by snow accumulation conditions especially water equivalent of snow

syneruptive and intereruptive lithofacies in lacustrine environments the cretaceous beolkeum member wido island korea abstract the cretaceous beolkeum member was deposited in a lacustrine environment affected by explosive volcanism and a number of syneruptive lithofacies are intercalated with lacustrine mudstones the syneruptive lithofacies were formed by primary volcanic processes and resedimented depositional processes during and after eruptions and exhibit unique depositional features which can be grouped into four syneruptive lithofacies assemblages sla 1 to sla 4 from bottom to top primary syneruptive lithofacies are represented by welded massive lapilli tuff in sla 1 and a normally graded lapilli tuff in sla 2 in sla 1 sustained pyroclastic density currents were able to displace lake water and rarely interacted with lake water resulting in the formation of a welded texture and columnar joints in sla 2 unsteady pyroclastic density currents rapidly disintegrated mixed with ambient water and transformed into high density turbidity currents depositing thick normally graded lapilli tuff resedimented syneruptive lithofacies were primarily controlled by volcaniclastic sediment supply after eruptions when volcaniclastic sediments were continuously supplied into the lake by debris flows a volcaniclastic fan can be formed sla 1 resulting in a coarsening upward trend and progradational geometry in case of relatively small amounts of volcaniclastic sediment supply turbidity currents would be a main depositional process depositing a series of normally graded tuff on the primary syneruptive lithofacies sla 2 showing a fining upward trend in sla 3 and sla 4 there are only a few cm thick normally graded tuff reflecting minor volcaniclastic sediment supply however overlying normally graded sandstones in sla 3 showing a coarsening upward trend and a thick normally graded sandstone in sla 4 suggest favorable conditions for the generation of the sediment gravity flows probably due to an increase in volcaniclastic sediment supply after eruptions

quantifying creep behaviour of clay bearing rocks below the critical stress state for rapid failure mam tor landslide derbyshire england abstract the mam tor landslide derbyshire england slips downhill at up to 0 5 m a 1 and offers an excellent opportunity to study time dependent creep in mudstones under in situ conditions annual surveys show that creep rates increase following heavy rainfall but to establish detailed correlation between creep and pore water pressure required spatially and temporally higher resolution monitoring we acquired 3 years of such data at 3 h intervals from wire creep meters borehole piezometers and rainfall monitoring showing that creep is strongly focused into the winter months and correlates well with pore water pressure summer grass and fern growth strongly influence rainfall infiltration recycling much of the rainfall back to the atmosphere explaining the seasonal variability of creep the dependence of creep rate on pore pressure can be recast as a rheological model relating shear strain rate to shear stress using the friction angle for the creeping mudstone to link effective normal stress to shear stress the creep is very non linear following a power law with a stress exponent of 48 this flow law may apply also to shear failure in poorly consolidated mudrocks under high pore pressure conditions for example within some landslides subglacial sediments tectonic fault zones tectonic melanges and accretionary complexes

measuring the in situ deformation of retaining walls by the digital image correlation method in this study the digital image correlation dic method was used to monitor the full field deformation of a retaining wall two retaining walls located in mountainous areas of taiwan were investigated the first fushan slope was characterized by substantial long term deformation and the second bulao slope was located beneath an expressway and was severely damaged by typhoon morakot this paper first describes the preparation procedures for in situ applications of the dic method various environmental factors such as fog rain light direction and spot mark clarity affected measurement precision and consequently produced monitoring images that were unsuitable for further analysis the dic analysis results clearly indicate the deformation pattern of the retaining walls the proposed method is accurate and effective for performing long term monitoring of retaining walls and the results can be used to accurately predict the tendency location and quantity of retaining wall displacement therefore the proposed dic method can be implemented to prevent disasters caused by landslide

tree ring based estimation of landslide block displacement evaluation of a new experimental approach abstract the mechanisms and velocities of landslide movements are important information for assessing hazards associated with landslides this contribution introduces a new approach in reconstructing the past rate of landslide displacement using dendrogeomorphic methods the principle of this method is based on the analysis of exposed roots in tension cracks or scarps of active landslides the identification and dating of anatomical changes in root ring series in various root segments induced by gradual root exposure due to crack spreading enable the estimation of the rate of root exposure and the calculation of the displacement rate of landslide blocks we analysed anatomical reactions of 87 root cross sections in tension cracks of an active landslide the moravskoslezske beskydy mts in the outer western carpathians microscopical analysis of microcuts from cross sections showed the reduction in the earlywood vessel sizes indicating the year of root exposure we identified 17 years of exposure between 1997 and 2015 we calculated the individual displacement rates of the landslide expressed as the segment rate between the two adjacent samples of tension crack spreading and the mean spreading rate for all roots crossing one tension crack the average total spreading rate for each tension crack was 3 2 cm year 1 with a maximum of 4 3 cm year 1 and a minimum of 1 7 cm year 1 although this new approach has some uncertainties and limitations it remains a low cost technique that allows us to reconstruct the minimal past rate of landslide displacement without the need of long term monitoring

resonance oscillations of the soufriere hills volcano montserrat w i magmatic system induced by forced magma flow from the reservoir into the upper plumbing dike abstract short period deformation cycles are a common phenomenon at active volcanoes and are often attributed to the instability of magma flow in the upper plumbing system caused by fluctuations in magma viscosity related to cooling degassing and crystallization here we present 20 min periodic oscillations in ground deformation based on high precision continuous borehole strain data that were associated with the 2003 massive dome collapse at the soufriere hills volcano montserrat west indies these high frequency oscillations lasted 80 min and were preceded by a 4 hour episode of rapid expansion of the shallow magma reservoir strain amplitude ratios indicate that the deformational changes were generated by pressure variations in the shallow magma reservoir and with reversed polarity the adjacent plumbing dike the unusually short period of the oscillations cannot be explained with thermally induced variations in magma properties we investigate the underlying mechanism of the oscillations via a numerical model of forced magma flow through a reservoir dike system accounting for time dependent dilation contraction of the dike due to a viscous response in the surrounding host rock our results suggest that the cyclic pressure variations are modulated by the dynamical interplay between rapid expansion of the magma chamber and the incapacity of the narrow dike to take up fast enough the magma volumes supplied by the reservoir our results allow us to place first order constraints on the viscosity of crustal host rocks and consequently its fractional melt content hence we present for the first time crustal scale in situ measurements of rheological properties of mush zones surrounding magmatic systems

mt pelee martinique may 8 and 20 1902 pyroclastic flows and surges abstract the distribution stratigraphic relationships and fragmental components of the may 8 and 20 1902 pyroclastic flows from mt pelee martinique together with eyewitness accounts suggest the following explanation for those eruptions the eruptions were vertically directed magmatic perhaps initiated phreatically and contained abundant juvenile lithics from congealed magma of the dome and neck this resulted in a two part eruption column having 1 a dense lithic charged part which collapsed into the crater and flowed out of a pre existing notch in its side giving rise to pyrochlastic flows and 2 a magmatically derived column containing gases juvenile vitric material and crystals which largely by passed the neck and dome and escaped into the atmosphere all of the energy of the flows was apparently focused through the notch they emerged fully turbulent and flowed down riviere blanche gravity segregation of large and abundant fragments soon resulted in a dense high concentration poorly fluidized block and ash flow confined to the valley leaving above a fully turbulent high energy ash cloud surge as the ash cloud surge moved down the mountain it continued to expand outward the process of gravity segregation continued as the ash cloud surge expanded resulting in secondary block and ash underflows toward st pierre the secondary block and ash flows developed on a gently sloping upland surface 100 m or more above the valley of riviere blanche the turbulent fragment depleted surges above the secondary block and ash flows maintained sufficient energy to devastate the landscape outward to about 3000 m including st pierre the surges refracted around obstacles and in one place moved up a small valley in a direction opposite to the main flows

aggregation in particle rich environments a textural study of examples from volcanic eruptions meteorite impacts and fluidized bed processing aggregation is a common process occurring in many diverse particulate gas mixtures e g those derived from explosive volcanic eruptions meteorite impact events and fluid bed processing it results from the collision and sticking of particles suspended in turbulent gas air to date there is no generalized model of the underlying physical processes here we investigate aggregates from 18 natural deposits 16 volcanic deposits and two meteorite impact deposits as well as aggregates produced experimentally via fluidized bed techniques all aggregates were analyzed for their size internal structuring and constituent particle size distribution commonalities and differences between the aggregate types are then used to infer salient features of the aggregation process average core to rim ratios of internally structured aggregates accretionary lapilli is found to be similar for artificial and volcanic aggregates but up to an order of magnitude different than impact related aggregates rim structures of artificial and volcanic aggregates appear to be physically similar single sub spherical regularly shaped rims whereas impact related aggregates more often show multiple or irregularly shaped rims the particle size distributions psds of all three aggregate types are similar 200 m this proves that in all three environments aggregation occurs under broadly similar conditions despite the significant differences in source conditions particle volume fraction particle size distribution particle composition temperature residence times plume conditions e g humidity and temperature and dynamics of fallout and deposition impact generated and volcanic aggregates share many similarities and in some cases may be indistinguishable without their stratigraphic context

facies architecture of a continental below wave base volcaniclastic basin the ohanapecosh formation ancestral cascades arc washington usa the 800 m thick oligocene ohanapecosh formation records voluminous sedimentation of volcanic clasts in the ancestral cascades arc washington state usa most volcaniclastic beds are dominated by angular pumice clasts and fiamme of andesitic composition now entirely devitrified and altered all beds are laterally continuous and have uniform thickness fine sandstone and mudstone beds have features typical of deposits from low density turbidity currents and suspension settling erosion surfaces cross beds and evidence of bi directional oscillatory currents i e wave ripples and swaley and hummocky cross stratification are almost entirely absent we infer that the setting was subaqueous and below wave base the abundance of angular pumice clasts crystals and dense volcanic clasts and the extreme thickness of several facies suggest they were derived from magmatic volatile driven explosive eruptions the extremely thick beds are ungraded or weakly graded and lack evidence of hot emplacement suggesting deposition from subaqueous water supported high concentration volcaniclastic density currents some of the thickest beds contain coarse rounded dense clasts at their base and are interbedded with accretionary lapilli bearing mudstone these beds are interpreted to be deposits from subaqueous density currents fed by subaerial pyroclastic flows that crossed the shoreline shallow basaltic intrusions and mafic volcanic breccia composed of scoria lapilli indicate the presence of intra basinal scoria cones that may have been partly subaerial the range in facies in the ohanapecosh formation is typical of below wave base continental lacustrine basins that form in proximity to active volcanic arcs and includes eruption fed and resedimented facies extreme instantaneous aggradation rates are related directly to explosive eruptions and sediment pathways reflect the locations of active volcanoes in contrast to conventional sedimentation processes acting in non volcanic environments

the significance of grain size breaks in turbidites and pyroclastic density current deposits turbidite beds and pyroclastic density current deposits commonly show abrupt internal changes in grain size with stepwise upward fining grain size breaks divide a turbidite bed into a lower sandy zone a middle silty zone and an upper muddy zone zone boundaries need not correspond with bouma division boundaries but the sandy zone usually consists of a b and occasionally c divisions the silty zone is composed of one or more of the b c and d divisions and the muddy zone correlates with division e pyroclastic density current deposits likewise display a tripartite zonation with prominent grain size breaks divergence of particle laden gravity currents into a lower dense body and an upper dilute turbulent wake can explain the formation of the lower grain size break fine particles are elutriated into the wake region by ambient entrainment through the current head while coarse grains are transported in the body particle size and concentration stratification is sustained by the turbulence and velocity structure of gravity currents with a velocity maximum and turbulence minimum also dividing currents into two regions two stages of deposition result the upper grain size break may be produced by buoyant lofting with fine particles convected into the water column or atmosphere as the flow wanes

pyroclastic density currents resulting from the interaction of basaltic magma with hydrothermally altered rock an example from the 2006 summit eruptions of mount etna italy after 16 months of quiescence mount etna began to erupt again in mid july 2006 the activity was concentrated at and around the southeast crater sec one of the four craters on the summit of etna and eruptive activity continued intermittently for 5 months during this period numerous vents displayed a wide range of eruptive styles at different times virtually all explosive activities took place at vents at the summit of the sec and on its flanks eruptive episodes which lasted from 1 day to 2 weeks became shorter and more violent with time volcanic activity at these vents was often accompanied by dramatic mass wasting processes such as collapse of parts of the cone highly unusual flowage processes involving both old rocks and fresh magmatic material and magma water interaction the most dramatic events took place on 16 november when numerous rockfalls and pyroclastic density currents pdcs were generated during the opening of a large fracture on the se flank of the sec cone the largest pdcs were clearly triggered explosively and there is evidence that much of the energy was generated during the interaction of intruding magma with wet rocks on the cone s flanks the most mobile pdcs traveled up to 1 km from their source this previously unknown process on etna may not be unique on this volcano and is likely to have taken place on other volcanoes it represents a newly recognized hazard to those who visit and work in the vicinity of the summit of etna

catastrophic lava dome failure at soufriere hills volcano montserrat 12 13 july 2003 the lava dome collapse of 12 13 july 2003 was the largest of the soufriere hills volcano eruption thus far 1995 2005 and the largest recorded in historical times from any volcano 210 million m3 of dome material collapsed over 18 h and formed large pyroclastic flows which reached the sea the evolution of the collapse can be interpreted with reference to the complex structure of the lava dome which comprised discrete spines and shear lobes and an apron of talus progressive slumping of talus for 10 h at the beginning of the collapse generated low volume pyroclastic flows it undermined the massive part of the lava dome and eventually prompted catastrophic failure from 02 00 to 04 40 13 july 2003 large pyroclastic flows were generated these reached their largest magnitude at 03 35 when the volume flux of material lost from the lava dome probably approached 16 million m3 over two minutes the high flux of pyroclastic flows into the sea caused a tsunami and a hydrovolcanic explosion with an associated pyroclastic surge which flowed inland a vulcanian explosion occurred during or immediately after the largest pyroclastic flows at 03 35 13 july and four further explosions occurred at progressively longer intervals during 13 15 july 2003 the dome collapse lasted approximately 18 h but 170 of the total 210 million m3 was removed in only 2 6 h during the most intense stage of the collapse

relationship between rain and or meltwater pore water pressure and displacement of a reactivated landslide abstract in order to clarify the relationship between rain and or meltwater mr pore water pressure and landslide displacement continuous monitorings were conducted at a reactivated landslide comprised mainly of weathered mudstone of tertiary in age an exponential relationship was found between the total amount of mr at each event and the amount of pore water pressure increment integrated by time impulse of pore water pressure in addition as the total mr increased the difference between the minimum and maximum values of pore water pressure for each event fluctuation range of pore water pressure also increased but the intensity of mr had little effect on the fluctuation range of pore water pressure the correlation coefficient for the fluctuation range of pore water pressure and cumulative landslide displacement and that for the impulse of pore water pressure and cumulative displacement were similar but were only 0 57 to 0 66 on the other hand the correlation coefficient for the total mr and cumulative landslide displacement was large 0 65 0 69 cumulative landslide displacement was very highly correlated with effective mr which shows the estimated water content in the ground for a half life period of 4 days and correlation coefficients were 0 89 0 92 thus the displacement characteristics of this reactivated landslide which has a long history of landsliding can be explained using the hydrological factor of water content rather than the hydraulic characteristics of pore water pressure

ignimbrite depositional facies the anatomy of a pyroclastic flow a model is presented for the depositional regimes in a pyroclastic flow to explain the origin of facies in the taupo ignimbrite and to compare these with other published examples in this model a pyroclastic flow consists of a head a body and a tail the head which is where fluidization caused by air ingestion occurs generates layer 1 deposits on lithological grounds these are divided into layers 1 p which is fines depleted and rich in pumice and 1 h which is fines depleted and rich in lithics and crystals layer 1 p represents material thrown forwards from the flow head and is termed the jetted deposits layer 1 h represents material sedimented from within the flow head and is termed the ground layer the body represents the bulk of the flow and the tail is its trailing part which is slowed by ground friction these parts generate the layer 2 deposits which include the valley pond ignimbrite and its associated ignimbrite veneer deposit localized depositional modes within the body and tail generate distinctive coarse pumice concentration zones and pumiceous lee side lenses behind obstacles at its outer limits all of the flow on interfluves is affected by air ingestion fluidization producing the distant facies which combines features of both layer 1 and 2 deposits one important conclusion of this work is that the thicknesses and compositions of the various facies are not related in any simple way to the thickness and composition of the parent flow

dynamics and deposits generated by the kos plateau tuff eruption controls of basal particle loss on pyroclastic flow transport the explosive eruption of voluminous silicic magmas often produces widespread and massive deposits formed from pyroclastic density currents while these punctuated events dramatically alter the landscape and have potential climate altering impact our understanding of the internal structure and transport dynamics of these eruptions is hampered by a lack of direct observations we utilize the natural boundary conditions encountered by the eruption of the kos plateau tuff to probe its internal structure as well as constrain the neotectonic activity in the region and eruption duration of this moderate to large 60 km3 event at the time of the eruption 161 ka the lower sea level in the mediterranean may have resulted in flows that traversed mostly land to the north of the eruptive vent while flows to the south may have encountered an expanse of water steep topography and overwater transport can impede the transport of the dense basal portions of the flow where particles make multiple or sustained contact with the bed we use an eulerian eulerian lagrangian computational approach coupled with overwater and overland boundary conditions including topography to determine the role of bed load versus suspended load in the transport of these flows we find that a ring vent structure and eruptive fluxes greater than 2 106 m3 s are required for the spatial distribution of the kpt the maximum grain size and deposit locations of the first voluminous ignimbrite unit d can be explained by suspended flow to the south consistent with overwater transport and bed load and suspended load transport to the north consistent with overland transport however the maximum lithic size for the largest and last ignimbrite unit e requires some bed load transport in all directions we propose that the boundary conditions were significantly altered during the course of the eruption through either the in filling of a shallow sea to the south or the development of a thick pumice raft to aid saltation on the basis of the inferred eruptive flux we estimate that the duration of the eruption climax in which most of the material was erupted likely only lasted from a few hours to a day

pyroclastic flows and surges over water an example from the 1883 krakatau eruption pyroclastic deposits from the 1883 eruption of krakatau are described from areas northeast of the volcano on the islands of sebesi sebuku and lagoendi and the southeast coast of sumatra massive and poorly stratified units formed predominantly from pyroclastic flows and surges that traveled over the sea for distances up to 80 km granulometric and lithologic characteristics of the deposits indicate that they represent the complement of proximal subaerial and submarine pyroclastic flow deposits laid down on and close to the krakatau islands the distal deposits exhibit a decrease in sorting coefficient median grain size and thickness with increasing distance from krakatau crystal fractionation is consistent with the distal facies being derived from the upper part of gravitationally segregated pyroclastic flows in which the relative amount of crystal enrichment and abundance of dense lithic clasts diminished upwards the deposits are correlated to a major pyroclastic flow phase that occurred on the morning of 27 august at approximately 10 a m energetic flows spread out away from the volcano at speeds in excess of 100 km h and traveled up to 80 km from source the flows retained temperatures high enough to burn victims on the sw coast of sumatra historical accounts from ships in the sunda straits constrain the area affected by the flows to a minimum of 4x103 km2 at the distal edge of this area the flows were relatively dilute and turbulent yet carried enough material to deposit several tens of centimeters of tephra the great mobility of the krakatau flows from the 10 a m activity may be the result of enhanced runout over the sea it is proposed that the generation of steam at the flow seawater interface may have led to a reduction in the sedimentation of particles and consequently a delay in the time before the flows ceased lateral motion and became buoyantly convective the buoyant distal edge of these ash and steam laden clouds lifted off into the atmosphere leading to cooling condensation and mud rain

inland directed base surge generated by the explosive interaction of pyroclastic flows and seawater at soufriere hills volcano montserrat the largest and most intense lava dome collapse during the eruption of soufriere hills volcano montserrat 1995 2004 occurred 12 13 july 2003 the dome collapse involved around 200 x 106 m3 of material and was associated with a phenomenon previously unknown at this volcano large pyroclastic flows at the peak of the dome collapse interacted explosively with seawater at the mouth of the tar river valley and generated a hot dry base surge that flowed 4 km inland and 300 m uphill the surge was destructive to at least 25 m above the ground and it carbonized vegetation the resulting two layer deposits were as much as 0 9 m thick although the entire collapse lasted 18 h the base surge greatly increased the land area affected by the dome collapse in a few minutes at the peak of the event illustrating the complex nature of the interaction between pyroclastic flows and seawater

small slope tilts caused by meteorological effects and vital processes of trees on a wooded slope in hidegviz valley hungary abstract long term measurements were carried out to investigate the relationship between ground tilts and variations of meteorological temperature precipitation and hydrological soil moisture content parameters in the area of the sopron mountains on a wooded slope of the hidegviz valley hungary the connection between surface tilts and the vital processes of the trees was also studied on the basis of the reference evapotranspiration calculated for the study area long and short term variations were separated a long term ground temperature change of 1 c caused a 4 rad tilt in the se direction short term temperature effects can be neglected the fluctuation of temperature around the freezing point caused tilts of about 10 rad c 1 the soil water content variation had the largest effect on the ground tilt 0 5 rad mm 1 its contribution to the total ground tilt in the investigated period was about 70 rad 65 of the total tilt of 107 rad toward the sse the contribution of the wind speed to the ground tilt was about 20 rad m s 1 toward the sse depending on the water content of the soil the wind did not cause a permanent ground tilt the magnitude of the daily tilt variations in the active growing period of trees from march to october is 1 2 rad while in the dormant period with no canopy the tilt variations were less than 0 4 rad the admittances between the evapotranspiration and the ground tilts were 0 3 0 5 rad mm 1 and 0 1 0 2 rad mm 1 in the active and dormant period of the trees respectively these small effects superimposed on each other can significantly contribute to slope failures the results of this study provide information which can be useful in the modelling of landslide movements and for the mitigation of landslide hazards

sediment laden gravity currents with reversing buoyancy there are many natural occurrences of sediment laden gravity currents in which the density of the interstitial fluid is less than that of the ambient fluid although the bulk density of the current is greater such currents are driven by the excess density of suspended particles however after sufficient particles have sedimented the current will become buoyant cease its lateral motion and ascend to form a plume examples of such currents include brackish underflows in deltas turbidity currents and pyroclastic flows experimental studies are described which show that due to sedimentation sediment laden gravity currents decelerate more rapidly than saline currents of the same density there is little difference in the experiments between a sediment laden current with neutrally buoyant interstitial fluid and one with buoyant interstial fluid until sufficient sediment has been lost to cause the latter kind of current to lift off a marked deceleration is then observed and a plume is generated with lift off occurring along the length of the current the resulting buoyant plume then generates a gravity current below the upper surface of the fluid in the tank the deposit from a current with buoyant fluid shows a fairly abrupt decrease in thickness beyond the lift off distance and has a flatter profile than that from a simple sediment current a theoretical model is presented which is based on the two layer shallow water equations and incorporates a model of the sedimentation in which particles are assumed to be uniformly suspended by the turbulence of the current the model shows good agreement with the observed lengths of the experimental currents as a function of time and predicts the lift off distance reasonably well these processes have implications for the behaviour of turbidity currents the interpretation of turbidites mixing processes in the oceans and the lift off of pyroclastic flows

facies variation of eruption units produced by the passage of single pyroclastic surge currents hopi buttes volcanic field usa abstract base surges are a significant volcanic hazard associated with phreatomagmatism but their transport and depositional dynamics are incompletely understood stratigraphic analysis and lateral tracing of surge eruption units produced by the passage of single base surges from haskie tuff ring hopi buttes volcanic field usa extend to 1 km from the vent and show similar downcurrent changes in lithofacies within 200 m of the vent eruption units are primarily disorganized lapilli tuff that is rich in juvenile pyroclasts at distances 200 m from the vent eruption units transform into a couplet of juvenile rich lapilli that grades upward into bedform bearing ash tuff at distances 900 m upper and lower beds of the eruption unit couplet transform into planar stratified beds at distances 1100 m couplets composing different eruption units are almost entirely composed of planar beds and amalgamate to form almost identical planar bedded ash tuff the collapse of dense eruption columns following explosive magma wet sediment interaction generated turbulent surge currents as the surges traveled away from the haskie vent they expanded and partitioned into a basal juvenile rich traction carpet and overlying accidental rich ash cloud surge near the limit of their runout the surges cooled and lost their pyroclastic load leaving planar beds of accidental rich ash the deposition of multiple surge eruption units with similar lateral and vertical facies transitions and a paucity of interbedded fallout suggests an eruption characterized by recurring phreatomagmatic explosions of similar size and the generation of surges with similar flow characteristics

unprecedented pressure increase in deep magma reservoir triggered by lava dome collapse 1 the collapse of the soufriere hills volcano lava dome on montserrat in july 2003 is the largest such event worldwide in the historical record here we report on borehole dilatometer data recording a remarkable and unprecedented rapid 600s pressurisation of a magma chamber triggered by this surface collapse the chamber expansion is indicated by an expansive offset at the near dilatometer sites coupled with contraction at the far site by analyzing the strain data and using added constraints from experimental petrology and long term edifice deformation from gps geodesy we prefer a source centered at approximately 6 km depth below the crater for an oblate spheroid with overpressure increase of order 1 mpa and average radius 1 km pressurisation is attributed to growth of 1 3 of gas bubbles in supersaturated magma triggered by the dynamics of surface unloading recent simulations demonstrate that pressure recovery from bubble growth can exceed initial pressure drop by nearly an order of magnitude

effects of the foot evolution on the behaviour of slow moving landslides the paper presents a time dependent 2d numerical model which has been developed with the purpose of highlighting the effects of the slope foot evolution on the behaviour of slow moving landslides the model allows to quantitatively analyse how foot mass variations can influence the stability and the movement rates of the landslide the landslide body is modelled as composed of two rigid blocks sliding on two different planes and interacting through a common boundary which position is assumed fixed during the analysis a finite difference approach is used to discretize the time for each time increment changes in model parameters are allowed including variations in shearing resistances groundwater level and block masses in order to simulate foot erosion during each iteration the overall stability of the system is checked computing the safety factor assuming that the percentage of mobilized shear strength is the same for the three surfaces if the system is not stable or if it is not at rest the velocity of the system is computed solving the momentum equations for the two blocks taking into account destabilising and resisting forces the mechanical interaction between the blocks and viscous components computed velocities are iteratively used to compute mass accumulation at the foot which in turn results in a change of the stability condition of the system examples are provided in order to highlight the roles of the model parameters finally the application to a real landslide vallcebre spain is presented which shows the advantage of considering the foot mass in the analysis of the displacement trends and the possibility to take into account the foot erosion in the long term behaviour of the slope

geotechnical characteristics of large slow very slow and extremely slow landslides based on a study of 45 large slow moving landslides it is apparent that for a landslide to travel slowly after failure the sliding is most likely to be active or reactivated on a basal rupture surface at or close to residual strength the likelihood of slow movement after failure is also increased when the inclination of the basal rupture surface is less than the residual friction angle the slow moving landslides are all of low rock mass strength with varying degrees of disaggregation or they possess soil strength the influence of lateral margins on landslide restraint is generally small with landslide movement typically controlled by fluctuations in piezometric pressure the most commonly observed slow large landslides are mudslides and translational debris rock slides followed by particular forms of translational rock slides and internally sheared compound slides some mudslides display evidence of short periods of up to moderate velocities

40ar 39ar ages of six apollo 15 impact melt rocks by laser step heating we have obtained 15 high resolution 21 51 step 40ar 39 age spectra on six apollo 15 impact melt rocks of different compositions using a continuous laser system on submilligram subsamples and on single crystal plagioclase clasts four of the six samples gave reproducible age spectra with well defined intermediate temperature plateaus over 48 or more of the 39ar released the plateaus are interpreted as crystallization ages samples 15304 7 69 15294 6 21 and 15314 26 156 gave virtually identical plateau ages whose weighted mean is 3 870 6 ma these three melt rocks differ in composition and likely formed in three separate impact events sample 15356 9 gave replicate plateau ages that average 3 836 12 ma and date a fourth and younger impact event the age spectra for samples 15308 9 and 15414 3 36 increase with increasing increment temperature and may have been formed in or affected by impacts at about 2 700 ma and 3 870 ma respectively so far there continues to be no convincing evidence in the lunar record for impact melts older than about 3 9 ga

anatomy of a submarine pyroclastic flow and associated turbidity current july 2003 dome collapse soufriere hills volcano montserrat west indies the 12 to 13 july 2003 andesite lava dome collapse at the soufriere hills volcano montserrat provides the first opportunity to document comprehensively both the sub aerial and submarine sequence of events for an eruption numerous pyroclastic flows entered the ocean during the collapse depositing approximately 90 of the total material into the submarine environment during peak collapse conditions as the main flow penetrated the air ocean interface phreatic explosions were observed and a surge cloud decoupled from the main flow body to travel 2 to 3 km over the ocean surface before settling the bulk of the flow was submerged and rapidly mixed with sea water forming a water saturated mass flow efficient sorting and physical differentiation occurred within the flow before initial deposition at 500 m water depth the coarsest components 60 of the total volume were deposited proximally from a dense granular flow while the finer components 40 were efficiently elutriated into the overlying part of the flow which evolved into a far reaching turbidity current

tephra deposits associated with a large lava dome collapse soufriere hills volcano montserrat 12 15 july 2003 abstract the 12 13 july 2003 dome collapse at soufriere hills volcano montserrat was the largest event of its kind during the eruption thus far 1995 2005 involving the removal of 210 million m 3 of the lava dome complex over 18 h less than 2 of the total volume of material involved in the dome collapse was deposited on land a pyroclastic density current deposit alongshore and inland from the tar river fan was generated from a single blast originating at the shoreline the blast was caused by the interaction of pyroclastic flows with seawater we propose that at the peak of the lava dome collapse a sharp increase in the volume flux of pyroclastic flows caused substantial displacement of seawater from the shoreline followed by inrush of seawater when the flux decreased a few minutes later the tsunami allowed penetration of seawater into the main body of the pyroclastic flow at the shoreline which led to explosive fragmentation of pyroclastic blocks tephra fall deposits accumulated at a high rate on montserrat causing extensive damage to vegetation and buildings their stratigraphy recorded fallout from high co pyroclastic flow clouds from a vulcanian explosion cloud at the peak in collapse rate caused by the fragmentation of degassed lava dome and from four vulcanian explosion clouds after the dome collapse caused by fragmentation of bubbly magma in the conduit the total tephra fall volume is estimated at 10 20 million m 3

the lateral facies of ignimbrites at laacher see volcano valley fill ignimbrites of the middle laacher see tephra mlst in the proximal depositional fan south of laacher see volcano are laterally continuous with fine grained overbank facies deposits 0 5 1 5 m thick covering higher elevations and interfluves between the paleovalleys the overbank deposits consist of up to 12 ash layers each 4 10 cm thick which show internal structures typical of ash flow transport such as poor sorting reverse size grading of pumice local normal grading of coarse ash sized lithics above a fine grained basal layer cross stratification behind obstacles and erosional unconformities thickness median grain size and number of individual layers decrease systematically with distance from the vent overbank ash layers thicken at the valley slopes and form discrete valley fill ignimbrite flow units in the paleochannels with median grain size increasing from 63 m to 350 m toward the center of paleochannels however the well defined overbank facies is obscured by mutual erosion of individual flow units overlapping data fields in ternary grain size variation diagrams indicate the overbank facies to have evolved from ash flows chiefly through depletion of lapilli and coarse ash overbank facies ash layers do not represent dust layers resulting from elutriation clouds of ash flows co ignimbrite ash or surge deposits developed on higher ground due to low concentration of solids they are similar in some parameters to taupo type ignimbrite veneer deposits but are interpreted differently the thin fine grained laacher see ash layers are thought to have been deposited from diluted portions of the flow proceeding directly from the eruption column while the main pyroclastic flows were confined to the paleovalleys radiating away from the eruptive center the wide distribution of the thin ash layers is attributed to the balance of deposition from various flow parts and turbulent entraining and heating of ambient air that sustained sufficient mobility of the diluted flows to spread across hills and level ground

origin of accretionary lapilli within ground hugging density currents evidence from pyroclastic couplets on tenerife aggregation of airborne particles is an important way in which the atmosphere is cleansed of fine dust particles such as following explosive eruptions and meteorite impacts we identify successive stages in the growth history of particle aggregates based upon well preserved ash aggregate bearing pyroclastic layers on tenerife the layers are persistently organized into couplets made up of a lower ignimbrite layer and an upper widespread coignimbrite ash fall layer the upper part of each ignimbrite contains whole and fragmented concentric laminated accretionary lapilli whereas the overlying coignimbrite ash fall layer lacks accretionary lapilli and is composed of framework supported smaller and nonlaminated ash pellets sometimes slightly deformed or partly disaggregated the pellets resemble the cores of the larger accretionary lapilli in the underlying ignimbrite layer these field relations are repeated numerous times in several different successions and they indicate that ash pellets not accretionary lapilli form within the coignimbrite ash plumes some pellets fell directly to the ground producing coignimbrite ash fall layers but others settled into pyroclastic density currents where they accreted successive concentric laminations of fine ash as they circulated through the variously turbulent levels of the stratified current and heat of the lower part of the current dried and partly lithified them into brittle accretionary lapilli the fully formed whole and broken accretionary lapilli were then deposited from the current along with ash and pumice lapilli numerous ignimbrite veneers on tenerife have the form of ash layers a few centimeters thick that drape topography and locally contain matrix supported accretionary lapilli most volcanoes lack laterally continuous field exposure and such accretionary lapilli bearing layers might be mistaken for ash fall deposits we highlight the value of careful distinction between different types of ash aggregate facies when interpreting the origin of pyroclastic deposits for example during hazard assessments

thrust sequences in the eastern spanish pyrenees detailed mapping of the south pyrenean zone in the eastern spanish pyrenees shows that a great number of alpine thrusts affect the basement and the cover the geometry of the thrust structures and their propagation sequence can be interpreted from balanced sections the folding dies out downwards from the higher thrust sheets to the lower ones and demonstrates a piggy back thrusting sequence these thrusts form a duplex the sole thrust of this duplex is the vallfogona thrust the roof thrust is rooted somewhere within the axial zone the thrusts climb southwards from the axial zone basement up into tertiary cover sediments these thrusts have been folded so that they now dip to the south and form the southern side of the axial zone antiformal stack locally smaller antiformal stacks developed and produced strong folds in the higher thrust sheets the south pyrenean zone studied is equivalent to the gavarnie nappe and the connection between them below the detached south pyrenean central unit may be the nogueres zone

unique and remarkable dilatometer measurements of pyroclastic flow generated tsunamis pyroclastic flows entering the sea may cause tsunamis at coastal volcanoes worldwide but geophysically monitored field occurrences are rare we document the process of tsunami generation during a prolonged gigantic collapse of the soufriere hills volcano lava dome on montserrat on 12 13 july 2003 tsunamis were initiated by large volume pyroclastic flows entering the ocean we reconstruct the collapse from seismic records and report unique and remarkable borehole dilatometer observations which recorded clearly the passage of wave packets at periods of 250 500 s over several hours strain signals are consistent in period and amplitude with water loading from passing tsunamis each wave packet can be correlated with individual pyroclastic flow packages recorded by seismic data proving that multiple tsunamis were initiated by pyroclastic flows any volcano within a few kilometers of water and capable of generating hot pyroclastic flows or cold debris flows with volumes greater than 5 10 6 m 3 may generate significant and possibly damaging tsunamis during future eruptions

submarine pyroclastic deposits formed during the 20th may 2006 dome collapse of the soufriere hills volcano montserrat the 20th may 2006 lava dome collapse of the soufriere hills volcano montserrat had a total non dense rock equivalent non dre collapse volume of approximately 115 106 m3 the majority of this volume was deposited into the ocean the collapse was rapid 85 of the mobilized volume being removed in just 35 min giving peak pyroclastic flow flux of 66 103 m3 s 1 channel and levee facies on the submarine flanks of the volcano and formation of a thick steep sided ridge suggest that the largest and most dense blocks were transported proximally as a high concentration granular flow of the submerged volume 30 was deposited from the base of this granular flow forming a linear high relief ridge that extends 7 km from shore the remaining 70 of the submerged volume comprises the finer grain sizes which were transported at least 40 km by turbidity currents on gradients of 2 at several localities the may 2006 distal turbidity currents ran up 200 m of topography and eroded up to 20 cm of underlying substrate multiple turbidites are preserved representing current reflection from the graben margins and deflection around topography the high energy of the may 2006 collapse resulted in longer submarine run out than the larger 210 106 m3 soufriere hills dome collapse in july 2003

measurement of landslide displacements using a wire extensometer a continuous recording of landslide displacements is often required in order to better understand the complex relationship between the triggering factors and the dynamics of the movement in this paper we discuss the performance of the borehole wire extensometer and the interpretation of its results the analysis for the case of a translational slide shows that the displacements measured with the wire extensometer are systematically smaller than the movements observed at the ground surface a relationship between the wire readings and the horizontal component of the landslide movement has been established by means of three equations representing different stages of the wire displacement within the borehole the applicability of these equations and the interpretation of the wire extensometer readings have been successfully checked at two landslide sites vallcebre in the eastern pyrenees and alvera in the dolomites

landslides in sado island of japan part i case studies monitoring techniques and environmental considerations abstract a sufficient knowledge on the kinematics and development of landslides helps to adopt proper measures that can be used to protect slopes and the environment in general this can be achieved by adequate monitoring programs this paper presents the findings of intensive monitoring activities carried out on shiidomari and katanoo landslides found in sado island of japan more than one year of observation of the two landslides allowed defining some peculiar futures of their kinematics and style of development the problem of slope instability in the two areas is generally accredited to various factors but both landslides were triggered by heavy rainfalls and snowmelt because of the outline of the area and the presence of relict topographic features the shiidomari landslide is considered to be a large scale reactivation of old slope failures the katanoo landslide is however a first time case geophysical investigations and drilling activities in shiidomari indicated the presence of two slip planes the deepest 80 100 m of these is controlled by existing lineaments monitoring data suggests that the body of the landslide has subsided as much as 1 16 m just below the main scarp but a centimeter in the central region the toe sector also experienced a significant amount of subsidence but this was counter balanced by an uplift on the opposite side of the landslide hence the landslide seems not any more active along the deepest slip surface although it may extend upward and define a series of shallow shear planes around the crown in the case of katanoo the landform characteristics differential weathering the road cut and groundwater fluctuations appeared to contribute much to determine the exact location of the landslide extensional cracks that preceded the landslide can be related to heavy rainfalls and the cold and warm cycles thereafter subsurface investigations and monitoring works indicated that the landslide has two slide blocks with different slip planes during the observation period the upper part of the landslide responded more effectively to rainfall and snowmelt than the middle and lower sections the corresponding movements however appeared to settle about three months after failure there were also little strain transmissions in boreholes and no significant change in the characteristics of the landslide the kinematics of deformation of many of the slopes in sado island resembles that of shiidomari landslide but mass movements along highways and mountain roads are usually similar to katanoo landslides of the type like shiidomari may not show sudden and drastic failures but are usually long lasting and can reactivate repeatedly along new shallow shear planes monitoring works and long term supervisions in these types of landslides are useful to identify impending failures and take the right measures before they brought about large scale destruction to the environment

sedimentology of the krakatau 1883 submarine pyroclastic deposits the majority of tephra generated during the paroxysmal 1883 eruption of krakatau volcano indonesia was deposited in the sea within a 15 km radius of the caldera two syneruptive pyroclastic facies have been recovered in scuba cores which sampled the 1883 subaqueous pyroclastic deposit the most commonly recovered facies is a massive textured poorly sorted mixture of pumice and lithic lapilli to block sized fragments set in a silty to sandy ash matrix this facies is indistinguishable from the 1883 subaerial pyroclastic flow deposits preserved on the krakatau islands on the basis of grain size and component abundances a less common facies consists of well sorted planarlaminated to low angle cross bedded vitric enriched silty ash entrance of subaerial pyroclastic flows into the sea resulted in subaqueous deposition of the massive facies primarily by deceleration and sinking of highly concentrated deflated components of pyroclastic flows as they traveled over water the basal component of the deposit suggests no mixing with seawater as inferred from retention of the fine ash fraction high temperature of emplacement and lack of traction structures and no significant hydraulic sorting of components the laminated facies was most likely deposited from low concentration pyroclastic density currents generated by shear along the boundary between the submarine pyroclastic flows and seawater the krakatau deposits are the first well documented example of true submarine pyroclastic flow deposition from a modern eruption and thus constitute an important analog for the interpretation of ancient sequences where subaqueous deposition has been inferred based on the facies characteristics of encapsulating sedimentary sequences

temporal occurrence and activity of landslides in the area of cortina d ampezzo dolomites italy abstract this article shows the results of research on landslides carried out in the area of cortina d ampezzo dolomites italy within the framework of the epoch project of the european community the investigated area where tourism activities and infrastructures are highly developed has been affected by several landslides since the retreat of the wurnian glaciers and is at present still affected by active slides and flows which endanger some villages after a geological and geomorphological description the distribution in space and time of landslides which occurred in the surroundings of cortina d ampezzo is presented the type activity frequency and when possible the age of mass movements have been outlined furthermore special attention is focused on the landslides active at present which are reactivations of ancient movements the results from the monitoring systems which were installed in order to survey kinematic and hydrogeologic parameters and define the movement rate are shown the research enables the reconstruction of the post wurmian geomorphological evolution of a site in the dolomites that appears to be very peculiar both on account of the wide distribution of landslides and the intense human activity

syneruptive features and sedimentary processes associated with pyroclastic currents entering the sea the ad 79 eruption of vesuvius bay of naples italy the ad 79 plinian eruption of vesuvius that buried pompeii and herculaneum began with pumice falls deposited towards the se of the volcano followed by pyroclastic currents directed towards the sw these currents reached herculaneum and rapidly entered the sea forming a fan the interpretation of seismic reflection profiles and gravity cores collected off herculaneum documents a submarine fan shaped pyroclastic body at 10 140 m water depth that we interpret as the submarine counterpart of the onshore pyroclastic current deposits this fan c 0 3 km 3 in volume displays a chaotic seismic facies that changes seaward to parallel reflectors and then to wavy reflectors gravity cores reveal a succession consisting of centimetre thick sand or silt sized ash couplets followed by a graded gravelly sand sized bed up to 180 cm thick containing shell fragments and beach derived pebbles overlain by centimetre thick graded and laminated sandy ash layers the depositional textures and sedimentary structures of the submarine pyroclastic fan have been interpreted as the product of the interactions between pyroclasts water waves and tsunamis induced by the ad 79 pyroclastic density currents into the bay of naples

the spatial and temporal distribution of grain size breaks in turbidites grain size breaks are surfaces where abrupt changes in grain size occur vertically within deposits grain size breaks are common features in turbidites around the world including ancient and modern systems despite their widespread occurrence grain size breaks have been regarded as exceptional and not included within idealized models of turbidity current deposition this study uses ca 100 shallow sediment cores from the moroccan turbidite system to map out five turbidite beds for distances in excess of 2000 km the vertical and spatial distributions of grain size breaks within these beds are examined five different types of grain size break are found type i in proximal areas between coarse sand and finer grained structureless sand type ii in proximal areas between inversely graded sand overlain by finer sand type iii in proximal areas between sand overlain by ripple cross laminated finer sand type iv throughout the system between clean sand and mud and type v in distal areas between mud rich debrite sand and mud this article interprets types i and v as being generated by sharp vertical concentration boundaries controlled by sediment and clay concentrations within the flows whilst types ii and iii are interpreted as products of spatial temporal fluctuations in flow capacity type iv are interpreted as the product of fluid mud layers which hinder the settling of non cohesive grains and bypasses them down slope decelerating suspensions with sufficient clay will always form cohesive layers near to bed promoting the generation of type iv grain size breaks this may explain why type iv grain size breaks are widespread in all five turbidites examined and are commonplace within turbidite sequences studied elsewhere therefore type iv grain size breaks should be understood as the norm not the exception and regarded as a typical feature within turbidite beds

timing and emplacement dynamics of newly recognised mass flow deposits at 8 12ka offshore soufriere hills volcano montserrat how submarine stratigraphy can complement subaerial eruption histories this contribution describes two mass movement deposits total volume 0 5 km3 identified in seven marine cores located 8 to 15 km offshore southern montserrat west indies the deposits were emplaced in the last 35 ka and have not previously been recognised in either the subaerial or distal submarine records age constraints provided by radiocarbon dating show that an explosive volcanic eruption occurred at ca 8 12 ka emplacing a primary eruption related deposit that overlies a large 0 3 km3 reworked bioclastic and volcaniclastic flow deposit formed from a shelf collapse between 8 and 35 ka the origin of these deposits has been deduced through the correlation of marine sediment cores component analysis and geochemical analysis the 8 12 ka primary volcanic deposit was likely derived from a highly erosive pyroclastic flow from the soufriere hills volcano that entered the ocean and mixed with the water column forming a water supported density current previous investigations of the eruption record suggested that there was a hiatus in activity at the soufriere hills volcano between 16 and 6 ka the ca 8 12 ka eruptive episode identified here shows that this hiatus was shorter than previously hypothesised and thus highlights the importance of obtaining an accurate and complete marine record of events offshore from volcanic islands and incorporating such data into eruption history reconstructions comparisons with the submarine deposit characteristics of the 2003 dome collapse also suggests that the 8 12 ka eruptive episode was more explosive than eruptions from the current eruptive episode

using global positioning system techniques in landslide monitoring the precise determination of point coordinates with conventional global positioning system gps techniques often required observation times of one to several hours in the last few years new gps methods have been developed among them the fast static and real time kinematic with higher productivity and good theoretical precision the main objective of this paper is to ascertain the performance of these methods in landslide monitoring practice we present first of all the basic principles of the gps the equipment and working procedures we discuss afterwards the applicability of the gps to the monitoring of landslide surface displacements compared with the classical surveying methods the gps allows a larger coverage and productivity with similar accuracy furthermore it can work in all kinds of weather conditions and a direct line of sight between stations is not required finally we present an example of the performance of the gps equipment in the landslide of vallcebre eastern pyrenees spain this landslide has been periodically monitored since 1987 with terrestrial photogrammetry and geodetic measurements theodolite electronic distance metres edm the movement extends over an area of 0 8 km2 and has experienced displacements as large as 1 6 m during the period 1996 1997 14 campaigns over a period of 26 months using both static and kinematic gps methods have been carried out the gps measurements have been compared with the results obtained with the edm inclinometers and wire extensometers and checked against fixed stable points the precision achieved with the gps measurements is 12 to 16 mm in the horizontal plane and 18 to 24 mm in elevation 2000 elsevier science b v all rights reserved

entrance of hot pyroclastic flows into the sea experimental observations the entrance of hot pyroclastic flows into water has been observed in a series of experiments in which shooting granular flows of hot ignimbrite ash 403 c of bulk density near that of water run down a smooth chute and enter a water filled tank at an angle of 26 flows of relatively cool ash 250 c mixing across the water surface over some distance from shore generates steam explosions forming fountains of wet and dry ash and convectively rising fine ash plumes steam explosions increase in strength and lateral extent towards higher ash temperatures and mass fluxes the explosions generate water waves that remain driven by massive fountain fallout across some distance from shore the ash fountains feed pyroclastic surges which advance down tank over water at high speeds underwater plumes of sediment falling from the ash fountains and surges drop coarse load onto the floor whereas the finer load forms a turbidity current high temperature and poor size sorting of pyroclastic flows are key parameters that determine the processes of interaction with water and the associated hazards poor sorting allows for the formation of ash cloud surges moving over water even from cool flows high temperatures cause littoral explosions and facilitate extensive mass transport over water all flows generate tsunami waves by different mechanisms

application of actualistic models to unravel primary volcanic control on sedimentation taveyanne sandstones oligocene northalpine foreland basin abstract this work is focused on the taveyanne sandstones gres de taveyanne an oligocene volcaniclastic turbidite sequence cropping out in the northern alpine molassa between se france and central switzerland with the aim to investigate the temporal relationship between volcanic activity and sediment supply detailed stratigraphic sedimentological and petrographic xrd analyses on mudstones and point counts on sandstones studies conducted on three sections col de l oulette and flaine in se france taveyanne in sw switzerland allow a discrimination of three main facies among which only one is extremely enriched in volcaniclastic detritus and characterized by features similar to those of disaggregated pyroclastic density current deposits the other two facies are characterized by variable to no volcanic detritus but supplied by crystalline and sedimentary detritus such sediment trends are similar to those of modern volcanically controlled source to sink systems this allows a reinterpretation of the taveyanne sandstones as a syn volcanic turbidite system episodically supplied by large amounts of volcanic detritus which periodically modified the drainage paths moreover the well known temporal and spatial persistence of such modifications in modern settings leads to conciliate the syn volcanic supply with the location of the volcanic centers in the internal part of the alps without invoking particular climatic and tectonic conditions controlling foreland sedimentation