debris flows and debris torrents in the southern canadian cordillera in canada debris torrents also referred to as channelized debris flows occur in parts of british columbia alberta and the yukon at least 17 deaths and an estimated 100 million of damage to bridges and property can be attributed to this natural hazard the debris mainly comprises large boulders rock fragments gravel to clay sized material tree and wood mulch materials that accumulate in the mountain creeks to be susceptible to a debris torrent a creek must have a drainage area within a critical range a profile that is sufficiently steep an accumulation of debris and some form of triggering mechanism the most common triggering mechanism is an extreme water discharge which may result from a very intense rainfall or a temporary damming of the creek in western canada the resulting torrents involve masses of debris typically less than 50 000 m3 that travel down creeks at speeds between 3 and 12 m s several passive and active forms of mitigation can be used to reduce the impact of debris to

on the assessment of the management priority of sediment source areas in a debris flow catchment in many alpine catchments the monitoring and hazard mitigation of debris flow events require enormous economic and social resources to confront these problems a subjective estimation of the most hazardous zones of the basin could be useful in the best sustainable planning of protective measures in this paper a new methodology is proposed that develops a management priority index mpi to rank sediment source areas by their quantitative capability to deliver debris flow volumes to a point of interest within the catchment the mpi sets the intervention priority based on a combination of three sub indicators a susceptibility indicator evaluating the overall catchment predisposition to generate debris flow a triggering indicator and a volume budget indicator assessing the rate of deliverable volume to a selected outlet mpi was applied to the basin of the rio gadria catchment venosta valley bolzano italy an alpine basin with an unlimited sediment supply that is characterized by multiple very active shallow landslides and bare soil zones the proposed ranking method was successfully verified using post event surveys and through evidence from consolidation check dams built over many years in the basin copyright 2014 john wiley sons ltd

prediction of debris flow inundation areas using empirical mobility relationships abstract a method proposed for delineating lahar hazard zones in volcanic valleys is adapted to debris flows the original method is based on two predictive equations that relate the lahar volume to the cross sectional inundated area and to the planimetric inundated area these predictive equations were derived by combining a scaling analysis of lahar kinematics with the statistical analysis of data for 27 historical lahars this paper tests the applicability of this approach to debris flow fans forty debris flow basins in the italian alps were surveyed and data on 27 historical debris flow events were collected in the field or by means of aerial photo analysis collected data reveal that the flow area a and the planimetric area b of a debris flow are linearly correlated to the debris flow volume v on a logarithmic scale with high statistical significance moreover the computed regression equations are very similar to those obtained from other published datasets on debris flows leading to the global fitting equations a 0 08 v 2 3 and b 17 v 2 3 these predictive equations are then implemented in an automated code dflowz that delineates the inundated area on a debris flow fan on the basis of a user specified debris flow volume taking the statistical uncertainty in the prediction into account dflowz is simple reproducible and it can handle both confined and unconfined flow the model is tested against 10 historical debris flow events providing a satisfactory agreement between observed and computed inundated areas in spite of the limitations due to dem accuracy and statistical uncertainty of the regression parameters test results show that the method can be useful for practical applications

inferred gas hydrates and clay diapirs near the storegga slide on the southern edge of the voring plateau offshore norway this paper presents a new data set including single channel airgun seismic lines okean long range side scan sonar data and gravity cores acquired on the edge of the voring plateau and in the region of the storrega slide the data acquisition was part of the 8th training through research ttr 8 expedition with r v professor logachev the acoustic profiles clearly show two laterally separated zones characterised by the presence of bottom simulating reflectors bsrs at about 350 ms twt subbottom depth the lower bsr zone is located on the slope of the voring plateau in the immediate vicinity of the northern headwall of the storegga slide and in some places below the slide deposits this zone runs parallel to the general trend of the continental slope the spatial distribution of the upper bsr zone located upslope in an area where diapir like structures are found does not demonstrate any topographic control interpretation of high backscatter patches on the okean sonographs associates the observed structures with fluid escape features on the seabed most of them are pockmarks but in a few places diapirs are cropping out and form dome like elevations after analysing the behaviour of the bsr sometimes crosscutting and its acoustic characteristics reversed polarity and after applying seismic inversion processing to estimate the acoustic velocity change across the bsr this reflector is interpreted to represent the base of the local gas hydrate stability field ghsf this information was used to derive the regional geothermal gradient spatial variations of the inferred geothermal field appeared to be negligible the observation of two separated bsr zones suggests different environmental controls for the growth of the hydrates enhanced reflectors observed in the intermediate zone can be explained by the presence of strata bound free gas accumulations and migration combined with overlying permeability barriers therefore a model for gas hydrate formation in relation to directional fluid migration processes fluid escape features and the presence of diapiric structures is proposed in this paper our model is supported by sedimentological analyses of seafloor samples which demonstrate the presence of stiff clays with evidence of gas migration and by paleontological studies of the cores retrieved from the pockmarks the presence of a bsr in the sedimentary section within the slide scar area implies the repositioning of hydrates to newly established equilibrium conditions after the slide event this observation allows us to simply estimate an upper limit of the fluid migration velocity in the order of several cm year finally the effect of hydrate dissociation on slope instability is considered assuming that the in situ decomposition of hydrates due to instantaneous depressurisation is slow enough to permit the excess volume of released gas and water to be re distributed through the whole sedimentary section above the paleo bsr with consuming heat and increasing pore pressure dissociation tends to shift the pt conditions back to equilibrium values it appears that the dissociation of hydrates due to sliding would cause only 0 2 increase of the pore pressure which would hardly contribute to further slope instability

a new system for acquisition and processing of very high resolution seismic reflection data a new digital seismic data acquisition system and accompanying software have been developed by ifremer to replace the analog equipment commonly used in very high resolution less than 1 m shallow marine seismic reflection surveys the acquisition part based on a hewlett packard 9000 microcomputer is capable of sampling rates of up to 15 khz for one channel signal processing and image processing can be performed either during the survey by the acquisition computer or after the survey with a software system that runs on a sun workstation the system has been developed for the specific requirements of coastal studies understanding of the sediment layers in such studies requires a vertical resolution of around 1 m in the top 10 m of sediment this system has been successfully used for the study of subtidal sand waves off the cherbourg peninsula france the results which revealed the internal structure of sand waves from about 3 m to 8 m high correlated well with synthetic seismograms that were create

mud volcanoes at the shelf margin of the east china sea abstract roughly circular sediment mounds varying from tens to hundreds of meters in diameter and from a few meters up to 40 m in height have been mapped for the first time at the shelf edge of the east china sea ecs high resolution seismic profiles together with swath bathymetric and acoustic data indicate that these features are common on the ecs outer shelf and on the upper western slope of the okinawa trough they are associated with unusually large pockmarks up to 40 m in depth and 600 m in diameter on seismic records bright spots phase inversions and other acoustic anomalies indicate that gas and or fluid escape plays an important role in the formation of these mounds they are often associated with normal faults that occur along the western slope of the okinawa trough these faults acting as conduits for migrating fluid based on regional stratigraphic correlation we propose that the source of mud and fluid is deeper older than 235 ka the seepage process is suspected to be very recent and probably still active based on the facts that 1 despite high sedimentation rate the mounds are not buried by recent sediments and 2 last glacial maximum deposits are reworked at the emplacement of the mounds carbonate cemented sediments and deep water reefs possibly associated with fluid seepage could be the origin of local patches of very high backscattering acoustic facies mapped with the swath bathymetric system

a new estimate of global methane flux from onshore and shallow submarine mud volcanoes to the atmosphere a new estimate of global methane emission into the atmosphere from mud volcanoes mvs on land and shallow seafloor is presented the estimate considered a lower limit is based on 1 new direct measurements of flux including both venting of methane and diffuse microseepage around craters and vents and 2 a classification of mv sizes in terms of area km2 based on a compilation of data from 120 mvs the methane flux to the atmosphere is conservatively estimated between 6 and 9 mt y 1 this emission from mvs is 3 6 of the natural methane sources and is comparable with ocean and hydrate sources officially considered in the atmospheric methane budget the total geologic source including mvs seepage from seafloor microseepage in hydrocarbon prone areas and geothermal sources would amount to 35 45 mt y 1 the authors believe it is time to add this parameter in the intergovernmental panel on climate change official tables of atmospheric methane sources

australian offshore natural hydrocarbon seepage studies a review and re evaluation abstract surprisingly few natural hydrocarbon seeps have been identified in australia s offshore basins despite studies spanning thirty years early studies of natural hydrocarbon seepage around the australian margin were generally based on the geochemical analysis of stranded bitumens water column geochemical sniffer sampling synthetic aperture radar or airborne laser fluorosensor later studies involved the integration of these remote sensing and geochemical techniques with multi channel and shallow seismic a review of these earlier studies indicates that many seepage interpretations need to be re evaluated and that previous data sets when placed in a global context often represent normal background hydrocarbon levels low recent burial and subsidence rates are not favourable for high rates of seepage there are also difficulties in proving seepage on high energy shallow carbonate shelves where seabed features may be rapidly re worked and modern marine signatures are overprinted on authigenic seep carbonates thus the relatively few sites of proven natural hydrocarbon seepage in australia s offshore sedimentary basins can be reconciled relative to their geological occurrences and the dominantly passive margin setting active thermogenic methane seepage on the yampi shelf the only proven documented occurrence in australia is driven by deposition of a thick late tertiary carbonate succession and late miocene tectonic reactivation therefore to increase the success of detecting and correctly interpreting natural hydrocarbon seepage data need to be analysed and integrated within the context of the local geological setting and with an understanding of what is observed globally

yangtze delta eastern china 2 late quaternary subsidence and deformation abstract late quaternary deposits examined on high resolution seismic profiles provide evidence of recent subsidence of the outer yangtze delta in the east china sea deformed late pleistocene strata and mud diapirs tilted bedding and gas deformed structures in holocene sequences record remobilization of underconsolidated sediment within and adjacent to the yangtze depocenter deformation types and their specific position relative to the depocenter record displacement of sediment as a result of quaternary overburden and probable compaction and deep seated tectonic motion the configuration of depositional sequences demonstrates that subsidence in the outer yangtze delta has continued from the late pleistocene to the present

back arc extension in the okinawa trough the okinawa trough lying to the east of china is a back arc basin formed by extension within continental lithosphere behind the ryukyu trench arc system middle to late miocene uplift associated with normal faulting of the initially adjacent ryukyu nonvolcanic arc and the taiwan sinzi folded belt corresponds to the first rifting phase the timing of rifting is supported by the presence of marine sediments of corresponding age drilled in the northern okinawa trough the rifting occurred after a major early miocene change in the motion of the philippine plate with respect to eurasia and ceased during the pliocene a second rifting phase started about 2 m y ago at the plio pleistocene boundary and has continued until the present time it has proceeded to a more advanced stage in the middle and southern okinawa trough than it has farther north detailed bathymetric sea beam seismic reflection and magnetics data collected during the pop 1 cruise of the r v jean charcot reveal the principal features of the extensional processes the back arc spreading phase started very recently in the southern and middle okinawa trough as exemplified by several en echelon and in some cases overlapping active central graben oriented n70 e n80 e some of these depressions are intruded by volcanic ridges of fresh back arc basalt with associated large magnetic anomalies transform faults between these en echelon active rifts are not obvious we suggest that the major part of the southern okinawa trough is underlain by a thinned continental crust and that except for the system of en echelon rifts of the southern okinawa trough the back arc basin oceanic domain is limited to a width of a few tens of kilometers or less in the axial portion of the trough the system of axial back arc volcanic ridges that occur in the rifts ends at the latitude of okinawa island whereas active volcanoes in the ryukyu arc occur only north of okinawa island we refer to this transition between active arc and back arc volcanism as the volcanic arc rift migration phenomenon vamp globally back arc volcanism propagated from the southern okinawa trough to the okinawa vamp area rifting continues to occur in the northern okinawa trough but is not yet accompanied by associated volcanism the okinawa vamp area is characterized by a series of parallel basaltic ridges oriented n75 e with associated linear magnetic anomalies characteristic of dyke intrusions we suggest that the formation of the back arc oceanic domain took place along the axial back arc extensional zone trending n75 e and that this zone presently ends at the southern extremity of the active volcanic chain the initial phase of formation of back arc basin oceanic crust is non steady state and is characterized by the lack of a developed fracture zone pattern the termination of the vamp area in the direction of the volcanic zone of the arc is consistent with the suggestion of molnar and atwater that the volcanic arc is a fundamental line of weakness which determines where initial back arc spreading occurs apparently back arc extension initially occurred within the continental lithosphere located westward of the ryukyu arc along its whole length but the subsequent back arc volcanism was initiated in the southernmost portion of the region and then moved northward this migration was accompanied by the shutting down of volcanic activity along the abandoned portions of the arc it is this transfer of volcanism that we call the vamp process thus arc and back arc basin volcanism seem to be associated in such a manner that spreading tends to migrate simultaneously with a cessation in volcanic activity along the arc this interplay of arc and back arc activity is probably linked to changes in the parameters of plate convergence since the plate motion in the phillippine sea is oblique to the trench at least in the southern part of the okinawa trough we suggest that the oblique resisting force applied to the edge of the overriding plate engenders the development of en echelon extensional features within and behind the arc the motion of the ryukyu platelet with respect to eurasia is consequently an extensional strike slip motion trending roughly parallel to the okinawa trough

transient modeling of regional rainfall triggered shallow landslides this study investigates the transient modeling of regional rainfall triggered shallow landslides in unsaturated soil using the richards equation to model shallow landslides within a distributed regional scale framework infinite slope stability analysis coupled with the hydrological model with consideration of the fluctuation of time dependent pore water pressure and the soil water characteristic curve proposed by van genuchten was developed the validity of the proposed model is established through several test problems by comparing the numerical results with the analytical solutions a new procedure to set up wide range shallow landslide analysis and to integrate regional distribution variations for input data such as geology groundwater level hydrogeological characteristics and rainfall intensity and duration was presented the results obtained demonstrate that the computed distribution of the safety factor is consistent with the distribution of actual landslides in addition the fluctuation of pore water pressure in unsaturated soil dominates the stability of landslides during typhoons accompanied by heavy rainfall the findings observed in this study are a fundamental contribution to environmental effects for landslides in areas with higher occurrence and vulnerability to extreme precipitation

hydrometeorological and landuse attributes of debris flows and debris floods during typhoon toraji july 29 30 2001 in central taiwan abstract the 921 chi chi earthquake a 7 5 m earthquake with center located near chi chi of nan tou county occurred on september 21 1999 and caused more than 2400 fatalities and totaling billions of dollars losses due to destruction and damages to private and public buildings roads bridges and hydraulic structures in central taiwan this 921 chi chi earthquake also triggered close to 26 000 landslides with a total area of 15 977 ha and severely disturbed mountain slopes thus setting the conditions for occurrence of more landslides and other related disasters post earthquake watershed restoration works progressed without disruptions by major typhoon rainstorms until july 29 30 2001 when typhoon toraji hit eastern and central taiwan with heavy rainfall having peak hourly intensity exceeding 70 mm h this rainstorm caused several major debris flows and debris floods that destroyed or severely damaged dams roads bridges dikes and houses in addition to causing 103 casualties 111 missing presumed dead 189 injured this study 1 explores the characteristics and impacts of debris flows floods and 2 investigates hydrometeorological and land use attributes of debris flows and debris floods associated with this typhoon toraji in central taiwan debris floods different from more familiar debris flows are extreme peak streamflows containing large quantities of muds rocks and debris normally occurring in third and fourth order watersheds data analysis and field investigations revealed that the disastrous debris flows and debris floods during typhoon toraji were essentially caused by very heavy rainfalls on inherently unstable mountain slopes that were loosened further earlier by the 921 chi chi earthquake the extremely intense rainfall of typhoon toraji provided not only additional materials by creating new and reactivating or enlarging old landslides but also high peak stream flows required for occurrence of debris flows and debris floods the destruction and damaging power of debris flows and debris floods witnessed during typhoon toraji suggests that the effectiveness of engineering structures for disaster prevention is limited for disaster mitigation it is required to have more comprehensive strategies such as 1 land use zoning that regulates and restricts human encroachment on hazardous areas and 2 implementation of evacuation drills and relocation plan for people currently living in the hazardous zones

characterisation and correlation of active hydrocarbon seepage using geophysical data sets an example from the tropical carbonate yampi shelf northwest australia abstract for the first time in australia active present day hydrocarbon seepage has been imaged on the tropical carbonate yampi shelf in 50 and 90 m water depth seepage is evidenced by gas plumes in the water column that are associated with seabed features such as clusters of reflective blocks hard grounds pockmark fields and mounds seepage activity and intensity seems to vary with changes in pressure related to macro tidal cycles the seabed features coincide with sub surface features such as areas of seismic signal attenuation under high amplitude reflectors seismic discontinuities and bright spots hydrocarbon migration seepage pathways appear to be controlled by the reactivation of pre existing fractures and dykes within the basement the types of seabed features and their preservation on a tropical carbonate shelf are strongly influenced by the coarse bioclastic nature of sediments and the high energy of macro tidal currents and storm reworking

gas hydrate crystals may help build reefs during a recent cruise in the porcupine basin off southwest ireland we discovered two extensive and hitherto largely unsuspected deep water reef provinces including a giant cluster of hundreds of buried mounds the ring shapes of many reefs suggest that they are caused by an axial fluid expulsion at the sea bed a transient flow well confined in space and time we are exploring various hypotheses but a stimulating avenue for research is opened by a glacially controlled growth pulse and subsequent decay of a shallow layer of gas hydrates as a methane buffer and probably indirectly as a ground for overlying biological communities

detection of gas migration from a deep source by the use of exploration 3d seismic data abstract periods of sustained gas seepage since mid miocene time is indicated in exploration 3d seismic data from the area of the sleipner fields in the north sea buried mounds suspected to be mud volcanoes may have been generated in association with gas migration in mid miocene time minor faults and fractures are present at the same horizon and the mud volcanoes seem to be distributed along some of these seismic chimneys indicate migration of gas from below this level through the faults and fractures and up to the seabed shallow gas accumulations in late pliocene sands above the mud volcanoes may be a result of the gas migration possible buried craters overlying seismic chimneys may have been generated in a period of sustained gas seepage followed by a less active period during which the craters have been buried a large depression at the seabed overlying seismic chimneys indicates a recent period of sustained gas seepage the gas is believed to have migrated from the sleipner gas reservoirs

using gravestones to assess changing rates of weathering in the united kingdom weathering rates were calculated using the height difference between lead lettering and marble on gravestones at three sites in the uk comparison of their regression lines and residuals suggested that two of the sites portsmouth and wolverhampton had similar amounts and rates of weathering over the last 100 150 years gravestones in swansea appear to have weathered much more and much faster than gravestones at the other two sites these differences may be the result of the differing pollution and rainfall histories of the three sites

weathering of coastal defensive structures in southwest england a 500 year stone durability trial historic structures can be viewed as exposure trials of the stone of which they are constructed as such they represent a geomorphological weathering experiment several structures of henrician sixteenth century and greater age on the coast of southwest england have been exposed to coastal salt weathering for 500 600 years long term weathering rates on five different rock groups are derived from careful study of weathering depths and forms there is significant variation in weathering rate between five major rock groups rank ordering of weathering rate values reveals a durability order of these rock groups which is confirmed by local juxtapositions controls on rock durability in the coastal weathering environment include both mechanical and mineralogical characteristics specific density and combined quartz and muscovite content are positively related to durability high feldspar and chlorite content are associated with low durability copyright 2000 john wiley sons ltd

measuring stone weathering in cities surface reduction on marble monuments the purpose of this study was to establish whether measurements of stone weathering recorded by different observers could be aggregated into a single data base for evaluating pollution effects on calcareous building stone apparent differences in recorded weathering rates on marble tombstones were here found to be partly a result of lettering size measured measuring devices used and individual observers

towards an improved understanding of erosion rates and tidal notch development on limestone coasts in the tropics 10 years of micro erosion meter measurements phang nga bay thailand knowledge and understanding of shore platform erosion and tidal notch development in the tropics and subtropics relies mainly on short term studies conducted on recently deposited carbonate rocks predominantly holocene and quaternary reef limestones and aeolianites this paper presents erosion rates measured over a 10 year period on notches and platforms developed on the permian ratburi limestone at phang nga bay thailand in so doing it contributes to informing a particular knowledge gap in our understanding of the erosion dynamics of shore platform and tidal notch development in the tropics and subtropics notch erosion rates on relatively hard ancient limestones measured directly on the rock surface using a micro erosion meter mem over time periods of a decade or more the average intertidal erosion rate of 0 231 mm yr is lower than erosion rates measured over 2 3 years on recent weaker carbonate rocks average erosion rates at phang nga vary according to location and site and are in rank order from highest to lowest mid platform 0 324 mm yr notch floor 0 289 mm yr rear notch wall 0 228 mm yr lower platform 0 140 mm yr notch roof 0 107 mm yr and supratidal 0 095 mm yr the micro relief of the eroding rock surfaces in each of these positions exhibits marked differences that are seemingly associated with differences in dominant physical and bio erosion processes the results begin to help inform knowledge of longer term shore platform erosion dynamics models of marine notch development and have implications for the use of marine notches as indicators of changes in sea level and the duration of past sea levels copyright 2014 john wiley sons ltd

the micro erosion meter use and limitations detection of anomalies in measurements of low rates of limestone surface lowering with a traversing micro erosion meter mem led to temperature controlled laboratory and field investigations of some sources of error in the method regressions for the correction of temperature change in the instrument and in the stud rock interface were obtained probe erosion tests permitted a correction to be devised and also provided information whereby a measure of operational irregularity was adopted corrections and error terms were applied to field measurements from two southern new south wales karsts and a collection of australian limestone slabs exposed at one site examination of these results and of published mem rates from other parts of the world validated the mem method marine platforms are lowered at such gross rates that these error sources may be neglected there however limestone lowering in terrestrial environments cannot be assumed to proceed at rates which permit this and recommendations are made about procedures to ensure that investigations are prosecuted within the limitations of the method

volcaniclastic debris flows at la fossa volcano vulcano island southern italy insights for erosion behaviour of loose pyroclastic material on steep slopes abstract this paper describes a qualitative model of erosion of loose volcaniclastic material on steep slopes of la fossa cone vulcano island italy that generates small volume debris flows the loose volcaniclastic cover rests on an almost impermeable substratum which comprises a fine grained hydromagmatic tuff morphologically three sectors were distinguished 1 a water supply zone slope 32 where rain water is enriched in mud and concentrated in the initiation zone 2 an initiation zone or source area sensu stricto slope with 30 where debris flows form and 3 a transport and deposition zone where debris flows deposited levees and terminal lobes slope 30 main episodes of erosion of loose volcaniclastic cover and debris flow generation occur in response to thunderstorms the erosion of tuff from superficial water added a significant amount of fines mud fraction to the initiating flows debris flow stoppage on steep slopes was interpreted as the result of a loss of mass estimated between 35 and 53 of total mass to form levees from field and laboratory data the density of debris flows was estimated at about 1950 kg m3 morphological data matrix texture mass number nm and clay content of debris flow deposits suggest that they were deposited by saturated granular slurries

the role of debris supply conditions in predicting debris flow activity debris flow frequency and magnitude were determined for 33 basins in southwest british columbia basins were first classifiedaseitherweathering limitedortransport limitedusingadiscriminantfunctionbasedondebris contributingarea an area weighted terrain stability number and drainage density multiple regression was used to predict magnitude peak discharge frequency and activity frequency times magnitude within each group of basins model performance was improved by stratifying the total sample of debris flow basins into weathering and transport limited groups explained varianceincreasedbyanaverageof15percentinthetransport limitedsample indicatingthatsedimentsupplyconditionsin themoreactivebasinsarefundamentalinpredictingdebrisflowactivity anindependenttestoftheregressionmodelswith 11basinsyieldedgenerallygoodresultsfordebrisflowmagnitudeandpeakdischarge predictionofdebrisflowfrequency provedproblematicalinweathering limitedbasins themethodsdevelopedhereprovideestimatesofdebrisflowattributes in basins for which few data on past events are available copyright 1999 john wiley sons ltd

measuring erosion with the micro erosion meter contributions to understanding landform evolution abstract we review the contribution made to understanding landform evolution through the use of the micro erosion meter mem and the variant the traversing micro erosion meter tmem the mem has allowed the direct measurement of bedrock erosion in terrestrial and coastal settings as well as of building stone as recorded in mem measurements world wide the average rate of surface lowering on shore platforms is 1 486 mm a 1 and on terrestrial rock surfaces measured lowering rates are on average 0 903 mm a 1 reported means obscure significant variation in rates from a range of environmental settings and lithologies the mem has in a number of examples allowed the identification of the contribution of individual processes in polygenetic settings particularly in shore platform studies the dynamic nature of rock weathering has been highlighted where the tmem has revealed rock surfaces swelling and contracting at time scales ranging from hours to years the mem will continue to provide useful data on erosion rates and processes but the most fruitful investigations will be those that combine the t mem with other techniques that transcend time and space scale issues in erosion and process measurement

quaternary seismic stratigraphy and paleoenvironments on the continental shelf of the east china sea abstract paleoenvironments and stratigraphy have been interpreted from 4380 km of seismic profiling collected during a geological and geophysical cruise on the continental shelf of the east china sea ecs undertaken in 1996 the geophysical data are correlated with a borehole situated on the outer shelf obtained by shanghai marine geology bureau indicating that six seismic units have been preserved since oxygen isotope stage 6 including four regressive transgressive cycles seismic units u2 u3 u4 u5 u6 and u7 are interpreted to correspond respectively to oxygen isotope stages 1 3 5 and 6 implying that sediment partitioning and sequence architecture in the ecs have been controlled by glacio eustasy and global climate changes alternating continental and marine strata corresponding to glaciation and interglaciation are well preserved on the outer shelf of the ecs most of the cold environment strata which formed on the outer shelf during oxygen isotope stages 2 and 4 are too thin to be recognized on sig 600j because of resolution but corresponding erosion surfaces exist seismic unit u7 is widespread over the shelf extending to the continental edge and showing little variation in thickness as the regression was pronounced and lasted a long time thus u7 can be used as a marker layer for correlation of quaternary strata on the shelf of the ecs post glacial transgression is obvious in the ecs marine strata with varied thickness were developed in the shallow sea of the inner shelf thinning toward the outer shelf the continental shelf of the ecs has been influenced by pacific tide wave systems for a long time forming tidal sand ridge sequences developed during transgressions corresponding to oxygen isotope stages 7 or 9 5 3 and 1

structural features of mud volcanoes and the fold system of the mediterranean ridge south of crete abstract new information on the geometry of the mud volcanoes folds and faults located in the central part of the mediterranean ridge is provided from long range and deep tow sidescan sonar images high resolution seismic and low frequency echosounder profiles and gravity cores obtained on the r v gelendzhik during the 1993 unesco esf training through research cruise symmetrical gentle folds with a mean wavelength of 750 m deform predominantly pliocene quaternary sediments but also perhaps as old as messinian in most areas of the mediterranean ridge the north northeast directed subduction of the african plate below the eurasian plate at the hellenic arc produces folds with hinge lines subparallel to the trend of the ridge however the hinge lines of the folds curve around the southern part of the area with highest concentration of mud volcanoes and produce an irregular u shape fold belt some of the folds show an intrusive nucleus and in some of them mud breccia appears to have flowed from the flanks of the folds into the troughs the mud volcanoes consist of domes of interlayered pelagic sediments and mud breccias containing sediments and rock fragments of late aptian to pleistocene ages mud breccia flows are mainly extruded radially from vents although rare fissure extrusions are also observed the mud volcanoes have an irregular to elliptical shape with diameters up to 16 km the distribution of mud volcanoes in the area is irregular but they are more frequent in an area called the olimpi field faults in the uppermost part of the mediterranean ridge are rare most of the faults are normal and subparallel to fold limbs in addition n20 e and n100 e subvertical faults are found controlling the shape of the mud volcanoes

morphological evolution of a mud capped dredge pit on the louisiana shelf nonlinear infilling and continuing consolidation abstract buried sandy paleo river channels on the continental shelf can be accessed through dredging for the restoration of beaches and barrier islands which are under the threat of land loss and rising sea levels however our knowledge on post dredging evolution of paleo river channels is still very limited in this study we focus on infilling rate sediment acoustic characteristics slope change and surficial morphology all of which have implications for the management of seafloor oil and gas infrastructure bathymetric data collected during nine bathymetric surveys over 13 years were used to study the long term changes of the peveto channel dredge pit which is 5 km offshore of holly beach in western louisiana usa this pit was constructed in 2003 and was completely infilled in or before 2016 initial pit infilling rates began at 214 cm year from 2003 to 2004 and then rapidly decreased to an average rate of only 33 cm year from 2006 to 2016 this corresponds volumetrically to 418 753 and 80 816 m3 year for the same intervals pit wall margins displayed small lateral migration moving

gully recharge rates and debris flows a combined numerical modeling and field based investigation haida gwaii british columbia abstract rainfall snowmelt and or other mass movements are possible triggers to initiate debris flows in supply limited landscapes clastic and organic materials together termed debris accumulate in the gully via various geomorphic processes that occur on gully sidewalls the conceptualization of this phenomenon has been termed the gully recharge rate with several recent field studies measuring such rates in coastal british columbia in the present study a simple numerical model is introduced to estimate debris flow volumes in haida gwaii british columbia based on debris flow recurrence intervals gully recharge rates and factors affecting deposition of debris flow material debris flow volumes obtained in model runs are somewhat lower than field based values by about half which is a reasonable result for this exploratory study the annual erosion rate clastic material for debris flows in the model run is 0 031 mm yr 1 this value is about 0 57 of the field based value and is lower than the erosion rate for debris slides in haida gwaii of 0 1 mm yr 1 deposition of debris flows in the model occurs in 60 of cases due to a decrease in channel gradient with deposition resulting from high stream junction angles being less common locations for initiation of debris flow deposition were situated in stream orders 3 and 4 in 60 of cases sensitivity analysis shows that in comparison to other model variables recharge rate has the greatest effect on the statistics and frequency distributions of debris flow volumes and total debris flow volume summation of all debris activity in a basin over the study time period

geomorphic coupling between hillslopes and channels in the swiss alps the coupling relationships between hillslope and channel network are fundamental for the understanding of mountainous landscapes evolution here we applied dendrogeomorphic methods to identify the hillslope channel relationship and the sediment transfer dynamics within an alpine catchment at the highest possible resolution the schimbrig catchment is located in the central swiss alps and can be divided into two distinct geomorphic sectors to the east the schimbrig earth flow is the largest sediment source of the basin while to the west the rossloch channel network is affected by numerous shallow landslides responsible for the supply of sediment from hillslopes to channels to understand the connectivity between hillslopes and channels and between sources and sink trees were sampled along the main rossloch stream on the schimbrig earth flow and on the rossloch depositional area geomorphic observations and dendrogeomophic results indicate different mechanisms of sediment production transfer and deposition between upper and lower segments of the channel network in the source areas upper part of the rossloch channel system sediment is delivered to the channel network through slow movements of the ground typical of earth flow shallow landslides and soil creep contrariwise in the depositional area lower part of the channel network the mechanisms of sediment transfer are mainly due to torrential activity floods and debris flows tree analysis allowed the reconstruction of periods of high activity during the last century for the entire catchment the collected dataset presents a very high temporal resolution but we encountered some limitations in establishing the source to sink connectivity at the catchment wide scale despite these uncertainties for decennial timescales the results suggest a direct coupling between hillslopes and neighbouring channels in the rossloch channel network and a de coupling between sediment sources and sink farther downstream with connections possible only during extraordinary events

acoustic scattering from mud volcanoes and carbonate mounds submarine mud volcanoes occur in many parts of the world s oceans and form an aperture for gas and fluidized mud emission from within the earth s crust their characteristics are of considerable interest to the geology geophysics geochemistry and underwater acoustics communities for the latter mud volcanoes are of interest in part because they pose a potential source of clutter for active sonar close range single interaction scattering measurements from a mud volcano in the straits of sicily show scattering 10 15db above the background three hypotheses were examined concerning the scattering mechanism 1 gas entrained in sediment at near mud volcano 2 gas bubbles and or particulates emitted in the water column 3 the carbonate bio construction covering the mud volcano edifice the experimental evidence including visual acoustic and nonacoustic sensors rules out the second hypothesis at least during the observation time and suggests that for this particular mud volcano the dominant

sidescan sonar images of mud volcanoes from the mediterranean ridge possible causes of variations in backscatter intensity abstract a survey of a large field of mud diapirs on the mediterranean ridge south of crete was carried out using both okean 9 5 khz and mak 1m 30 khz sidescan sonar systems during leg 2 of the third training through research cruise of r v gelendzhik in june and july 1993 high backscatter intensities were recorded by both systems to different degrees over the mud diapirs and their immediate surroundings causes of variations in the backscatter intensity are considered to be the spatial distribution of mud breccia associated with the mud domes both the burial depth of the mud breccia beneath hemipelagic drape and its areal extent and its physical properties along with contributions from seafloor roughness and the topography of the mud domes significant sources of volume scattering of the sidescan sonar sound signal are considered to be mud breccia inhomogeneities represented by millimetric centimetric clasts of various lithologies and free gas bubbles distributed through the mud matrix a good general relationship is established between these sources and the observed backscatter variations through analysis of ground truth data from core samples with 5 khz deep tow subbottom profiler records and seafloor video observations as well as the sidescan sonar records but a fully quantitative assessment of this relationship would require acoustic modelling and additional ground truth data

comparative characteristics of the black sea and mediterranean ridge mud volcanoes morphological and structural characteristics of the black sea and mediterranean ridge mud volcanoes studied during several unesco esf cruises of the r v gelendzhik 1991 1994 are compared on the basis of single and multi channel seismic and sidescan sonar observations morphologically three types of mud volcanoes were distinguished in the black sea and six types in the mediterranean they differ in size shape and presence of the mud flows some types from both localities are very similar to each other but in any case their deep structure is very distinctive this difference in deep structure is explained by their development in different geological conditions under an extensional regime with high terrigenous input in the black sea and under strong lateral compression on the mediterranean ridge

pleistocene forced regressions and tidal sand ridges in the east china sea abstract tidal sand ridges are common features on modern shelves but only few examples of such preserved sand bodies are described in pleistocene deposits in the stratigraphic record some sand bodies encased in shales previously interpreted as sand ridges have been reinterpreted as shoreface deposits more than 5000 km of high resolution seismic data from the east china sea correlated to geotechnical boreholes and shallow cores demonstrate the potential of sand ridge preservation and allow reconstruction of the depositional history of pleistocene fourth order 100 kyr depositional sequences a high subsidence rate of about 300 m myr allows the preservation of three elementary sedimentary facies constitutive of a motif which was repeated during glacio eustatic cycles they consist of 1 regressive marine prodeltaic prograding wedges 2 estuarine and continental deltaic facies and 3 transgressive sand ridges similar in shape and orientation to modern sand ridges major discontinuities traceable over the entire outer continental shelf along distances of hundreds of kilometers are transgressive and regressive surfaces of marine erosion whereas sequence boundaries formed by fluvial erosion are difficult to identify on this low gradient shelf because of the asymmetry of the pleistocene glacio eustatic cycles most of the preserved sedimentary record with the exception of sand ridges corresponds to forced regressive deposits deposits that formed during a seaward shift of the shoreline due to relative sea level lowering

an empirical approach to studying debris flows implications for planetary modeling studies 1 high resolution images acquired by the mars global survey mars orbiter camera show gullies on the walls of impact craters and valley systems on mars depositional aprons associated with these gullies have been interpreted by malin and edgett 2000 to be characteristic of debris flow and to indicate the presence of sources of liquid water at shallow depths below the martian surface by focusing on a terrestrial debris flow we test the application of chezy type modeling to provide more direct estimates of the dynamics of proposed debris flows on mars traditionally planetary scientists constrained by available remotely sensed data have used a range of flow models to gain insights from deposits into the behavior and rheologic nature of features such as lava flows debris flows and gravity driven flows on the basis of these model results broad interpretations of the physics governing flows of granular materials have been tempting based on limited field derived data this study tests and validates the extent to which the absolute value and relative variations of empirical parameters derived from the chezy type models describe the behavior of the general s slide debris flow 38 24 n 78 23 w in madison county virginia the results indicate that extreme caution must be taken when interpreting model results for turbulent flows of granular materials we obtained high precision topographic profiles superelevation data sedimentary facies and sedimentary textural properties over the debris flow this study focuses on the empirical parameter c whose value gauges energy dissipation in a flow thereby called flow resistance using field observations both variations and absolute values of c along the debris flow have been computed using two approaches 1 assuming constant volumetric flow rate q where only topography and high resolution images are required to compute channel dimensions and 2 a variable q calculated using field derived data assuming near newtonian flow conditions in the debris flow estimated values of c range from 0 035 to 0 099 when q is fixed c decreases as a function of distance downstream when q varies and c is computed from field derived flow speeds its value tends to increase downstream slightly these opposite results have been compared to the field observations to determine which best describes the behavior of the flow the variations in c downstream obtained using the flow speeds are most consistent with the geomorphic evidence for erosion of material by the debris flow and the presence of bends in the channel the average values of c 0 036 0 33 for the general s slide have been compared with computed c values for newtonian and near newtonian flows to assess the rheology of the flow during emplacement our terrestrial study demonstrates that advances in understanding of the dynamics of debris flows on the mars depends on obtaining debris flow speeds in addition to channel topography and flow thickness rather than just on channel topography flow thickness and the assumption that q is constant mars orbiter camera moc and mars observer laser altimeter mola data can be used to derive channel topography flow thickness and possibly flow speeds such data will provide more direct estimates of the dynamics of debris flows on mars than are currently available

fault associated seabed mounds carbonate knolls off western ireland and north west australia abstract groups of seabed mounds suspected to be modern carbonate knolls or bioherms have been located on reflection seismic data in the porcupine basin off western ireland and in the vulcan sub basin off north west australia the size of these mounds is impressive often being over 1 km across and over 100 m high in the porcupine basin they occur in water depths of 650 1000 m whereas in the vulcan sub basin they occur in water depths of 200 350 m shallow seabed coring in the porcupine basin has provided data on the age lithological composition and hydrocarbon concentrations in the upper 3 m layer of sediment both on and off the mounds in both basins the mounds occur close to faults which may provide conduits for upward migrating hydrocarbons the seepage of hydrocarbons is suspected to have caused local eutrophication or fertilization by providing nutrients to bacteria which in turn are part of the food chain for higher organisms the dominant organism in the porcupine basin examples appears to be the deep water coral lophelia sp whereas in the vulcan sub basin the mounds appear to be halimeda dominated

do carbonate reefs form due to fluid seepage buried carbonate reefs are favoured hydrocarbon prospecting targets mainly due to their high porosity and potential for containing large quantities of petroleum the question of the true relationship between reef structure and the internally trapped fluids hydrocarbons is here raised as one of cause and effect in other words which came first the hydrocarbons or the carbonate reef itself modern bioherms and seabed carbonate reefs in amongst other locations the north sea and the gulf of mexico are shown to form in close association with active hydrocarbon seepages mainly based on results from ecological studies at deep ocean vent communities a new model for carbonate reef formation is promoted that such reefs form at locations containing high concentrations of bacteria and other microorganisms suspended in the water column as a result of seeping fluids solutions and gases that provide some of the energy basis and carbon source for ecosystems independently of photosynthesis therefore on burial and effective sealing capping these carbonate reefs become hydrocarbon reservoirs trapping and accumulating the very minerals on which they in the first place were dependent

simulation of the dissolution of weathered versus unweathered limestone in carbonic acid solutions of varying strength a simulation was undertaken within a climatic chamber to investigate limestone dissolution under varied carbonic acid h2co3 strengths as a possible analogue for future increases in atmospheric co2 arising from global warming twenty eight samples cut from a block of bath box hill limestone from somerville college oxford which had been removed during restoration after 150 years in an urban environment were weighed and placed in closed bottles of thin plastic containing varying concentrations of h2co3 half of the stone samples were derived from exposed surfaces of the stone block weathered while the others were obtained from the centre of the block on unexposed surfaces unweathered the purpose of this was to compare dissolution of previously weathered versus unweathered surfaces in strong ph 4 73 versus weak ph 6 43 solutions of h2co3 a temperature of c 19 c was maintained within the chamber representing a plausible future temperature in oxford for the year 2200 given current warming scenarios the simulation lasted 25 days with a few stone samples being removed midway stone samples show reduced weight in all cases but one there was greater dissolution of stone samples in a strong h2co3 solution as conveyed by higher concentrations of total hardness and ca2 in the water samples as well as enhanced microscopic dissolution features identified using sem the simulation confirms that enhanced atmospheric co2 under global warming given adequate moisture will accelerate dissolution rates particularly of newly replaced limestone building stones however previously weathered surfaces such as those on historical stone exposed for a century or more appear to be less susceptible to the effects of such increased rainfall acidity conservation techniques which remove weathered surfaces such as stone cleaning may accelerate future decay of historical limestone structures by increasing their susceptibility to dissolution copyright 2006 john wiley sons ltd

mud volcanoes in deepwater nigeria abstract detailed study of 3d seismic data from deepwater nigeria has revealed the presence of features interpreted to be mud volcanoes they occur in an upper slope environment seen as 1 2 km circular features at the seabed seabed cores from the mud volcanoes contain oil gas and sand shale clast content richer than the seabed background pliocene fossils have been identified in the cores demonstrating transport of material from depth the features show a high seabed seismic amplitude above a chimney of chaotic seismic reflections and data wipe out the mud volcanoes in the study area shows two distinct clusters located over deeper structural culminations four active mud volcanoes area 1 are located above a rollover anticline in the central part of the area cuspate listric faults reach the seabed on the up slope side of these mud volcanoes four abandoned mud volcanoes have also been identified with progressively older ages towards the crest of the underlying structure these abandoned features are associated with an extremely chaotic seismic signature a combination of over pressured carrier beds and low integrity top seals are believed to be responsible for the formation of these mud volcanoes it is further believed that gas expansion subsequent to seal failure was the main driving force for what must have been violent eruptions the long lived mud volcano activity over the deep structural closure suggests a plumbing system that focuses on escaping compaction water and hydrocarbons through time in the south west of the study area another cluster of five mud volcanoes is located above a shale diapir the seabed expression of the members of this cluster is more varied some show a positive relief at the seabed while others show circular depressions the largest feature represents an assemblage of many smaller mud volcanoes with a common root system their seismic expression is also different from that of area 1 with a well defined sediment wedge at surface and a shallower root system these features are believed to represent a less violent type of mud volcano characterised by ductile flow tectonic stress due to growth of the underlying diapir is thought to have played an important role during eruption in addition to focused methane escape and the low mechanical strength of the overburden

estimating the mud depth of debris flow in a natural river channel a theoretical approach and its engineering application mud depth of debris flow is an essential parameter for assessing the hazard magnitude in an event however direct prediction of mud depth in a natural river channel is a scientific challenge because current methods often treat the complex relief of bed surface as a rectangular one which makes the prediction illogical in this paper we propose a new theoretical approach the so called numerical integral method based approach for estimating the maximum mud depth of debris flow at a complex cross section in a natural river channel given a predefined peak discharge of the debris flow event the numerical integral method based iteration algorithm uses the riemann method to search for an approximate mud depth in contrast to the previous methods the presented approach addresses an important issue namely it takes into account the complex shape of the bed surface and superelevation at the bend for natural channels two cases are used to illustrate the performance and advantages of the presented approach one is a well documented event in the previous study and the other is a debris flow event after ms 8 0 wenchuan earthquake an engineering application regarding the rational design of a debris flow canal is subsequently discussed the canal was completely destroyed in a debris flow event in 2008 we used the proposed method to back analyze the mud depth and velocity in the canal it was found that the abrupt decrease of mud depth from the natural channel to the concrete canal significantly reduced the transportation capability thereby causing blockage in the canal the canal was modified and reconstructed in 2009 with suggested improvements from the proposed method and successfully transported subsequent debris flow in 2011

gaia s breath global methane exhalations abstract methane ch 4 is the most abundant organic compound in the earth s atmosphere where it acts as a greenhouse gas and thus has implications for global climate change the current atmospheric ch 4 budget however does not take into account geologically sourced ch 4 seepage geological sources of ch 4 include natural macro and micro seeps mud volcanoes and other miscellaneous sources such as gas hydrates magmatic volcanoes geothermal regions and mid ocean ridges macro seeps contribute 25 tg teragrams ch 4 yr to the atmosphere whereas micro seepage contributes perhaps 7 tg ch 4 yr mud volcanoes emit 5 tg ch 4 yr and miscellaneous sources emit 8 tg ch 4 yr to the atmosphere thus the total contribution to the atmosphere from geological sources is estimated to be 45 tg ch 4 yr which is significant to the atmospheric organic carbon cycle and should be included in any global inventory of atmospheric ch 4 we argue that the atmospheric ch 4 global inventory of the interplanetary panel on climate change must be adjusted in order to incorporate geologically sourced ch 4 from naturally occurring seepage

mud volcano field seaward of the barbados accretionary complex a deep towed side scan sonar survey a 30 km2 diapiric field has been identified near 13 50 n up to 12 km seaward of the deformation front of the barbados accretionary complex using a deep towed side scan sonar with a 3 5 khz profiler we identified 31 different diapiric structures based on seismic stratigraphy we show that this field has been active for 200 000 years and that it is a transient feature triggered by the seaward propagation of the high pore fluid pressure associated with the decollement beneath the accretionary complex both basement and decollement in this area are anomalously shallow due to the presence of a n110 basement ridge the height of the diapirs above seafloor does not exceed 40 50 m and can be related to the pressure head of the mud below the decollement two types of structures are identified mud volcanoes and massively emplaced diapirs and ridges on the one hand enigmatic circular very flat mud pies and conical mounds on the other hand the second type of structures has steeper slopes and appears to be associated with very active venting as confirmed by a submersible exploration reported in a companion paper le pichon et al this issue b the venting results in the formation of a stiff carbonate crust and of large subsiding basins around the mud pies continuous active fluid expulsion through these structures indicates that an efficient piping system still connects them to the zone of anomalously high pore pressure below the protodecollement

mud diapirism and subcretion in the barbados ridge accretionary complex the role of fluids in accretionary processes mud diapirism has recently been recognized in several modern accretionary wedges it provides an important means of dewatering accretionary wedges and should be regarded as an important process for producing the melanges found in both modern and ancient accretionary terranes mud diapirism affects a large area of the barbados ridge accretionary complex the distribution of the mud diapirs appears to be primarily controlled by the presence of underconsolidated terrigenous submarine fan deposits that are being accreted to the complex the frequency of diapir occurrence decreases northward as the fan becomes thinner mud diapirs are absent from the very eastern most part of the complex formed from sediments accreted at its toe with the exception of a few mud volcanoes on the ocean floor in front of the complex the initiation of diapirism appears to be spatially coincident with the onset of subcretion or underplating of sediment to the base of the complex at a ramp between two levels of decollement it is proposed that the release of mud and pore water from the subcreted sediments is a direct or indirect cause of most of the mud diapirism in the accretionary complex there is a range of diapiric form dependent on the viscosity of the mud from mud volcanoes fed by low viscosity mud to higher viscosity mud ridges the diapirs in the eastern areas of the complex are generally mud volcanoes with narrow conduits feeding a surface mound mud ridges are prominent in the western parts of the complex this is interpreted as reflecting a general westward decrease in the fluid content of the accretionary complex bottom simulating seismic reflectors formed by gas hydrate are commonly developed in the areas of mud volcano occurrences the presence of the hydrate indicates that large volumes of methane are being generated at depth in these regions the generation of methane may be contributing to zones of overpressuring in the wedge methane may also be partly responsible for driving the diapiric material to the surface to form mud volcanoes ridges in the subducting oceanic crust beneath the accretionary complex locally enhance diapirism above their crests and southern flanks faults formed later in the development of the complex are more commonly associated with diapirism than those resulting from accretion at the toe of the wedge these later faults play an important role in controlling the sites of individual mud volcanoes chains of mud volcanoes and mud ridges

transgressive and highstand systems tracts and post glacial transgression the east china sea abstract the late pleistocene holocene depositional sequence on the shelf in the east china sea ecs is interpreted on the basis of the analyses of four sediment cores and high resolution seismic reflection sub bottom profiler records along a ne sw across shelf transect sedimentary strata deposited above a lowermost planar erosional surface that was formed during sea level fall of the last glacial are divided into two units along a ne sw across shelf transect changjiang okinawa the lower unit is characterized by seaward dipping tangential clinoforms with a thickness of 30 40 m at mid shelf depths and less than 30 m beneath the outer shelf prograding clinoforms are more obvious in mid shelf environments the upper unit is characterized by an upper transparent layer that is formed into ridge and swale topography the boundary between the upper and lower units is sharp and erosional surficial sediments taken by cores from the central ecs shelf are also divided into two facies a sandy facies consisting of sand or sandy gravel with moderately abundant molluscan shell fragments and a muddy facies comprising mud intercalated with thin sand layers the sandy facies is widely distributed on the middle to outer shelf seafloor and has a measured thickness of 30 cm up to several metres radiocarbon ages of molluscan shells in this sediment are less than approximately 10 ka bp except for ages from basal shell lag deposits which are 10 40 ka bp the muddy facies underlies the sandy facies and has radiocarbon ages of 2 7 2 9 ka bp previous work and 20 38 ka bp this study and tl ages of 27 50 ka bp previous work the boundary between these lithologic units is an erosional sharp contact the sandy and muddy facies are correlated with the upper and lower seismic units respectively the lower unit is characterized by prograding clinoforms and is interpreted to represent deltaic or nearshore tidal ridge sediments of the paleo changjiang river that were deposited during the last glacial lowstand of sea level as a lowstand systems tract the underlying erosional surface is interpreted to be a sequence boundary formed as a regressive marine erosional surface during the fall of sea level the erosional boundary between the lower and upper units is interpreted as a transgressive surface of erosion formed during the subsequent rise of sea level the upper unit has a modern sand ridge topography and is interpreted to represent offshore shelf sand ridges of the transgressive to highstand systems tract

seabed morphology and gas venting in the black sea mudvolcano area observations with the mak 1 deep tow sidescan sonar and bottom profiler abstract the central part of the black sea was investigated with the mak 1 deep tow acoustic system providing sidescan observations and acoustic profiling subsequently underwater tv recordings and bottom sampling was done in an area with extensive mudvolcanism the mud volcanoes can be divided into three types according to their dimensions and morphology the first type has a seabed diameter of more than 2 km reaches a height of 100 150 m has a complex top with a crater like structure and gentle slopes and reflects massive mudflows in the crater and at its flanks the second type has smaller dimensions is more conical in cross section almost without relief on its relatively steep slopes and is characterised by small radial mudflows the third type is made up by the only mud volcano with a partially collapsed rim and with massive and liquid mudflows the first type expectedly is in a mature relatively passive stage the latter two types seem to be younger and more active various types of low relief slides are found in the area and are related to the presence of shallow subbottom gas 40 100 m below the seafloor or mudvolcano activity evidence for the presence of gas in the mudvolcano area is shown by gas venting acoustic turbidity acoustic masking numerous pockmarks acoustic voids and acoustic windows gashydrates do occur associated with some of the mudvolcanoes

volcaniclastic debris flows in the clanio valley campania italy insights for the assessment of hazard potential abstract the rugged and steep slopes of the clanio valley campania southern italy mantled by volcaniclastic deposits from explosive eruptions of somma vesuvius and phlegraean fields volcanoes have a great potential for generating volcaniclastic debris flows during the well known meteorological event of may 5 6 1998 which triggered tens of debris flows causing enormous damage and casualties in the area of sarno quindici siano bracigliano sqsb the clanio valley was also affected by these hazardous phenomena debris flows were triggered by the failure of the volcaniclastic cover of the carbonate relief in the form of soil slips mainly on the sides of steep valleys slope between 26 and 45 a map of the hazard potential was created on the basis of both field and computer assisted morphometric data three classes characterised by a high medium and low hazard potential were distinguished within the higher class a better and more detailed zonation was obtained by studying the shape of the disrupted and undisrupted basins during the may 5 6 1998 event in the nearby sarno quindici siano bracigliano area this type of morphometric analysis can be applied rapidly by using a digital elevation model dem which allows a rapid investigation of large scale areas such an approach can be useful in areas characterised by similar geological and geomorphological settings

inscription legibility method for estimating rock weathering rates abstract relative legibility of dated inscription is closely associated with measured surface recessions for 3895 vermont marble tombstones and the resulting ordinal to ratio transfer function allows weathering rates to be computed for many exposed rock surfaces that cannot be measured by more accurate methods case studies demonstrate applications of the technique 1 surfaces of horizontal ground level marble plaques have dissolved at steady rates of 1 3 mm 100 yr in providence ri and 1 1 mm 100 yr in richmond va despite reports of increasing acid rain 2 vertical faces of century old marble tombstones in upper midwestern united states small towns have receded 10 times faster 1 4 mm 100 yr than have stones in less polluted environments 3 vertical faces of limestone monuments have receded at half the rate 0 5 mm 100 yr of vermont marble tombstones 0 9 mm 100 yr in louisville ky 4 aspect differences have not affected recession rates of marble pillar surfaces near philadelphia pa 5 aspect is important to sandstone granular weathering rates at inscription rock nm where north facing cliffs recede 3 times faster 0 9 mm 100 yr than do southeast facing cliffs 6 horizontal pre weathered quartizite surfaces at a scenic overlook in maryland recede at 0 6 mm 100 yr

mud volcano field seaward of the barbados accretionary complex a submersible survey we describe a 0 55 km2 semicircular mud pie and three adjacent diapiric mounds explored using the submersible nautile near 13 50 n 12 km seaward of the barbados accretionary complex deformation front this diapiric field had been previously explored with an acoustically navigated deep towed side scan sonar thus providing an accurate base map the mud pie is situated at a depth of 4938 m in addition to visual observations water rock sediment and biological sampling we measured temperature gradients and made geochemical analyses of the samples fluid venting associated with chemosynthetic animal communities is widespread on all four structures but is maximal in the central third of the mud pie the chemosynthetic life distribution on the mud pie displays a concentric zonation which we relate to an increase in venting activity toward the center as evidenced by thermal gradients recent mud flows are present in the centralmost part of the mud pie the simplest interpretation of the structure is that it is a mud lake covered by a mechanically resistant carbonate crust we determine that approximately 106 m3 of fluid are advected upward through the crust of the mud lake every year this large amount of fluid implies large scale lateral transport

twenty year weathering remeasurements at st paul s cathedral london microerosion meter mem measurements of the surface height of the balustrade of st paul s cathedral london have been repeated in the year 2000 following earlier measurements in 1980 1981 1985 and 1990 methodological sources of error mean that while the measurements were made to 0 0001 mm the data are reliable to two decimal places there was a reduction in the mean erosion rate on horizontal sites from 0 045 mm a1 in the period 1980 1990 to 0 025 mm a1 in 1990 2000 decreases in atmospheric so2 levels from 20 25 ppb in 1980 1982 to around 10 ppb in 1990 2000 offer a causal explanation the surface topography evolved more erratically in 1990 2000 than before with much but not all of the more microelevated areas showing greater and often more variable erosion there are also indications of less erosion and more surface rises in low lying microareas on horizontal sites which is interpreted as possible deposition and or microfloral growth in wetter depressions the pattern being largely absent on a well drained vertical site

geomorphology s role in the study of weathering of cultural stone abstract great monumental places petra giza angkor stonehenge tikal macchu picchu rapa nui to name a few are links to our cultural past they evoke a sense of wonderment for their aesthetic fascination if not for their seeming permanence over both cultural and physical landscapes however as with natural landforms human constructs are subject to weathering and erosion indeed many of our cultural resources suffer from serious deterioration some natural some enhanced by human impact groups from the united nations to local civic and tourism assemblies are deeply interested in maintaining and preserving such cultural resources from simple rock art to great temples geomorphologists trained in interacting systems process and response to thresholds rates of change over time and spatial variation of weathering processes and effects are able to offer insight into how deterioration occurs and what can be done to ameliorate the impact review of recent literature and case studies presented here demonstrate methodological and theoretical advances that have resulted from the study of cultural stone weathering because the stone was carved at a known date to a baseline or zero datum level some of the simplest methods e g assessing surface weathering features or measuring surface recession in the field provide useful data on weathering rates and processes such data are difficult or impossible to obtain in natural settings cultural stone weathering studies demonstrate the importance of biotic and saline weathering agents and the significance of weathering factors such as exposure microclimate and human impact more sophisticated methods confirm these observations but also reveal discrepancies between field and laboratory studies this brings up two important caveats for conservators and geomorphologists for the conservator are laboratory and natural setting studies really analogous and useful for assessing stone damage for the geomorphologist does cultural stone data have any real relevance to the natural environment these are questions for future research and debate in any event cultural stone weathering studies have been productive for both geomorphologists and conservators continued collaboration and communication between the geomorphic historic preservation archaeological and engineering research communities are encouraged

cold water corals are they hydrocarbon seep related numerous cold water ahermatypic coral reefs so called lophelia reefs up to 30m high 150m wide and 400m long occur at waterdepths from 100 to 350 m off mid norway after the discovery of relatively high interstitial methane concentrations 204 ppb in sediments collected at the base of one of these reef structures a causative link between the presence of the reefs and local micro seepage through seabed of light hydrocarbons is here suggested shallow seismic records gathered across this and other reef colonies off mid norway also indicate the existence of gas charged sediments below the reefs

gas hydrate destabilization enhanced dewatering benthic material turnover and large methane plumes at the cascadia convergent margin mixed methane sulfide hydrates and carbonates are exposed as a pavement at the seafloor along the crest of one of the accretionary ridges of the cascadia convergent margin vent fields from which methane charged low salinity fluids containing sulfide ammonia 4he and isotopically light co2 escape are associated with these exposures they characterize a newly recognized mechanism of dewatering at convergent margins where freshening of pore waters from hydrate destabilization at depth and free gas drives fluids upward this process augments the convergence generated overpressure and leads to local dewatering rates that are much higher than at other margins in the absence of hydrate discharge of fluids stimulates benthic oxygen consumption which is orders of magnitude higher than is normally found at comparable ocean depths the enhanced turnover results from the oxidation of methane hydrogen sulfide and ammonia by vent biota the injection of hydrate methane from the ridge generates a plume hundreds of meters high and several kilometers wide a large fraction of the methane is oxidized within the water column and generates 13c anomalies of the dissolved inorganic carbon pool

debris flows some physical characteristics and behaviour field observations on 449 debris flows in the queen charlotte islands british columbia are summarized movement of debris is classified according to seven characteristic types designated for the purposes of the study data on the physical characteristics of the events are presented an analysis of the data is made with reference to event initiation yield and deposition using both mechanistic and morphological criteria for those events which initiate on an open slope the infinite slope model is used to establish a relationship between field drainage class and slope angle for assumed frictional and cohesive soil strength parameters the field drainage classes are directly related to the postulated location of the groundwater surface within the depth of the rupture plane deposition of channelized events is found to be influenced by the ratio of channel width to channel gradient with the onset of deposition expected when the ratio exceeds unity five classes of depositional area are proposed the mag

sedimentological processes in lahars insights from optically stimulated luminescence analysis abstract a lahar is a sediment laden flow capable of major destructive impacts on infrastructure and human life how lahars transport sediment is thus a key issue for understanding lahar sedimentology and behavior especially in terms of the lahar s hydraulic and rheological properties which can be substantially altered as the lahar gains or loses material during its travel in this research we analyze lahar entrainment processes by evaluating luminescence signals total photon counts from lahar sediments using blue luminescence signals blsl a portable osl reader that analyzes several grams of polymineral and polygrain size samples was applied we use data from three lahars in the tenenepanco and huiloac gorges on popocatepetl volcano mexico to elucidate the ways in which lahars may gain lose and transport sediment during flow sediment samples for luminescence analysis were taken through the full thickness of the lahar deposits at eight different sites for two lahars 1997 and 2001 and at one site for a lahar that occurred 500 yrs ago mean luminescence values obtained for the 1997 lahar help to evaluate the relationship between the lahar entrainment processes and the drainage at the different sites for the 2001 lahar this relationship was also established taking into account the channel slope the main conclusion is that luminescence signals total photon counts can be used to detect entrained material in the flow because the bulked materials modify the final osl signals the application of this type of luminescence analysis thus has the potential to provide a better understanding of sediment entrainment in these sediment laden flows

the mediterranean ridge and related mud diapirism a background abstract the mediterranean ridge stretching from the calabrian rise to the florence rise is the largest structural unit of the eastern mediterranean sea it is directly related to ongoing convergence and collision of the african and eurasian plates starting in the oligocene and is considered to be a giant accretionary complex consisting of intensively folded and faulted rocks of the african margin since its origin in the late miocene the ridge continued to grow up and outward experiencing more deformation because of the developing collision the mud diapirism and mud volcanism are usual and wide spread phenomena for the mediterranean ridge that developed as a result of an intensive tectonic overburden due to stacking of rock units by thrusting and strong lateral compressional stress pressing up and squeezing plastic sedimentary series out onto the seafloor

the concept of transport capacity in geomorphology the notion of sediment transport capacity has been engrained in geomorphological and related literature for over 50 years although its earliest roots date back explicitly to gilbert in fluvial geomorphology in the 1870s and implicitly to eighteenth to nineteenth century developments in engineering despite cross fertilization between different process domains there seem to have been independent inventions of the idea in aeolian geomorphology by bagnold in the 1930s and in hillslope studies by ellison in the 1940s here we review the invention and development of the idea of transport capacity in the fluvial aeolian coastal hillslope debris flow and glacial process domains as these various developments have occurred different definitions have been used which makes it both a difficult concept to test and one that may lead to poor communications between those working in different domains of geomorphology we argue that the original relation between the power of a flow and its ability to transport sediment can be challenged for three reasons first as sediment becomes entrained in a flow the nature of the flow changes and so it is unreasonable to link the capacity of the water or wind only to the ability of the fluid to move sediment secondly environmental sediment transport is complicated and the range of processes involved in most movements means that simple relationships are unlikely to hold not least because the movement of sediment often changes the substrate which in turn affects the flow conditions thirdly the inherently stochastic nature of sediment transport means that any capacity relationships do not scale either in time or in space consequently new theories of sediment transport are needed to improve understanding and prediction and to guide measurement and management of all geomorphic systems

gas hydrate associated with mud diapirs in southern okinawa trough many mud diapirs have been recognized in southern okinawa trough by a multi channel seismic surveying on r v kexue i in 2001 gas hydrates have been identified by the seismic reflection characteristics the velocity analysis and the impedance inversion geothermal heat flow around the central of the mud diapir has been determined theoretically by the bottom simulating reflectors bsrs comparing the bsr derived and the measured heat flow values we infer that the bsr immediately at the top of the mud diapirs indicate the base of the saturated gas hydrate formation zone bsghfz but not as we ordinarily know the base of the gas hydrate stability zone bghsz which could be explained by the abnormal regional background heat flow and free gas flux associated with mud diapirs as a result it helps us to better understand the generation mechanism of the gas hydrates associated with mud diapirs and to predict the gas hydrate potential in the southern okinawa trough

millennium long recession of limestone facades in london historical data on the temperature and precipitation data for london has been combined with output from the hadley model to estimate the climate of london for the period 1100 2100 ce this has been converted to other parameters such as freeze thaw frequency and snowfall relevant to the weathering of stone facades the pollutant concentrations have been estimated for the same period with the historical values taken from single box modelling and future values from changes likely given current policy within the metropolis these values are used in the lipfert model to show that the recession from karst weathering dominates across the period while the contributions of sulphur deposition seem notable only across a shorter period 1700 2000 ce observations of the late seventeenth century suggest london architects witnessed a notable increase in the recession rate and attributed fretting quality to smoaks of the sea coal the recession rates measured in the late twentieth century lend some support to the estimates from the lipfert model the recession looks to increase only slightly and frost shattering will decrease while salt weathering is likely to increase

quantitative analysis of debris torrent hazards for design of remedial measures debris torrents which are rapid flows of soil and organic debris down steep mountain channels are a major natural hazard in many parts of british columbia a series of recent occurrences along the

on the pullout resistance of geosynthetics pullout tests are reported on geosynthetic test specimens embedded in a relatively dense coarse sand sample the tests are displacement controlled and are performed at different vertical effective

piercement shale diapirism in the deep water vema dome area voring basin offshore norway abstract within the norwegian 15th round deep water production licence no 217 on the voring plateau on the norwegian continental slope there is an unusually rugged seafloor topography our study addresses new 2d 3d and bathymetric data acquired in the vema dome area where evidence for active piercement shale diapirism is found the cores of the shale diapirs consist of coccolith oozes deposited during the paleocene and miocene individual shale diapirs and diapiric escarpments rise up to 70 m above the general sea floor at 1200 m water depth one of the key questions in our study has been to find out why diapirism is triggered over the vema dome and not over the nearby nyk high which has similar buried deposits of coccolith oozes on the basis of interpretations of the new data we conclude that the triggering is caused by a combination of at least three factors a a buried low density high porosity layer of deformable material the coccolith ooze b a doming substratum which causes extension and faulting c migration of light hydrocarbons through some of the faults and fault zones a fourth factor which probably contributes to triggering is tectonic instability the one factor that discriminates the vema dome area from the neighbouring nyk high area is the dome itself we therefore suspect that this in some way is the main factor responsible for the triggering furthermore we conclude that the process of piercement shale diapirism in the vema dome area is probably still active but because the movement of the sediments is suspected to be very slow it should be of only minor concern to future oil field development

morpho acoustic characterization of a shallow water mud volcano offshore scoglio d affrica northern tyrrhenian sea responsible for a violent gas outburst in 2017 abstract a violent gas outburst occurred offshore the scoglio d affrica islet tuscan archipelago northern tyrrhenian sea on march 16th 2017 with local fishermen observing columns of dirty water rising up to 10 m above the sea surface the integration of video footage and dissolved ch4 measurements collected 5 days after the event with high resolution multibeam data collected 4 months later allowed us to characterize the source area of the outburst corresponding to a shallow water mud volcano the mud volcano covers an area of ca 170 000 m2 has a vertical relief of ca 30 m with respect to the surrounding seafloor and an estimated volume of ca 1 106 m3 based on bathymetric reconstruction the elongated nnw sse shape of the mud volcano is compatible with local structural trends indicating a tectonic control for its development the mud volcano is made up of two mounds whose tops are located at a depth of ca 10 m the southern mound was responsible for the 2017 outburst as testified by a 15 20 m wide circular crater on its summit where a large amount of mud breccia and diffuse seepage from small pockmarks were observed in video footage the flanks of the mud volcano are steep and characterized in the upper part by a hummocky morphology and multiple sediment flows on the western flank the characterization of the mud volcano and the deposits associated with the 2017 gas outburst provides insight into seafloor shaping processes linked to fluid seepage in shallow water sectors this is a particularly relevant issue considering both the paucity of studies on shallow water mud volcanoes as well as the hazard associated with violent gas outbursts in such settings as witnessed by the march 16th 2017 event

landslide inventory in a rugged forested watershed a comparison between air photo and field survey data abstract landslide inventories are routinely compiled by means of aerial photo interpretation api when examining photo pairs the forest canopy notably in old growth forest hides a population of not visible landslides in the present study we attempt to estimate how important is the contribution of landslides not detectable from aerial photographs to the global mass of sediment production from mass failures on forested terrain of the capilano basin coastal british columbia api was coupled with intensive fieldwork for identification and measurement of all landslides a 30 year framework was adopted we show that not visible landslides can represent up to 85 of the total number of failures and account for 30 of the volume of debris mobilised such percentages display high sub basin variability with rates of sediment production varying by one order of magnitude between two sub basins of the study area this is explained qualitatively by gis based analysis of slope frequency distributions drainage density and spatial distribution of surficial materials such observations find further support in the definitions of transport limited and supply limited basins as a practical consideration to land managers we envisage that supplementary fieldwork for landslide identification is mandatory in transport limited systems only fieldwork has demonstrated that gully related failures have a greater importance than one could expect from api

morphometric comparison of weathering features on side by side carbonate rock surfaces with different exposure ages a case from the croatian coast this study presents the comparison of morphometry of karren features developed on two rock surfaces located side by side having different exposure times cosmogenic 36cl analyses were used to determine the age of a rock surface exposed after a rockslide that occurred 2400 years ago whereas the rock surface not affected by the slide was exposed to weathering for a longer time period clint and grikes trittkarren rillenkarren solution pits and kamenitzas were measured comparatively less density of grikes on the surface affected by the slide made it having a fresh appearance most of the grikes were inherited from previous weathering stage and exposure time since the rockslide event has not been sufficient to homogenize these features between both rock surfaces tritkarren and rillenkarren were preferentially found on the rockslide surface indicating that their genesis is likely to occur at decadal to centennial timescale solution pits and kamenitzas were found on both surfaces and some of their size parameters were indistinguishable between the populations of both rock surfaces area and depth parameters of both forms were clearly correlated and we define a morphometric index a d ratio as the slope between these two parameters within each population after an initial stage preferential weathering occurs along the vertical axis in solution pits and laterally in kamenitzas thus we suggest that the a d ratio is related to the evolution relative age of the karren features thus under rock surfaces affected by the same weathering conditions lower a d ratios of solution pits and higher a d ratios of kamenitzas indicate longer time exposed to weathering thus although solution pits and kamenitzas are likely to be developed in decadal to centennial timescales their morphology changes through time at millennial timescale and it can be tracked by morphometric analysis

recent tectonic activity in the south barbados prism deep towed side scan sonar imagery abstract data collected during the diapisar cruise nov 1990 using the french deep towed side scan sonar s a r are presented these data provide clear evidence of recent tectonic activity in the southern part of the barbados accretionary prism many markers as linear lineaments or sigmoidal features which are observed on diagenetically indurated sea floor are the surficial traces of faults or folds and networks of conjugate fractures where fluids are released through the structures and provide very active venting these markers can serve as a basis for detailed mapping of some of the tectonic structures and for an analysis of their kinematic evolution their geometry suggests the occurrence of reworked folds and shear zones this domain is affected by abundant clay diapiric tectonics due to the interaction between 1 the sedimentological context characterized by the important terrigenous supplies coming from the orinoco river and building a wide prodelta in which levels of clay supersaturated in water can act as decollement layers and 2 the geodynamic context of the area situated in the connection zone of three different types of margins the data presented show that on the eastern end of the south caribbean wrench fault system shear stresses can rework either en echelon folds associated with this system or compressional structures due to subduction the most recent structures seem largely due to the influence of shearing and correspond to transpressive or transtensive deformations rather than pure compressional structures

stratigraphic framework and evolution of the mid late quaternary since marine isotope stage 8 deposits on the outer shelf of the east china sea abstract the east china sea ecs is a vast river dominated depositional basin because of its broad shelf and extensive river sediment supply this study investigated the mid late quaternary stratigraphic framework and evolution of the outer ecs shelf based on a borehole core dh02 and seismic profiles seven sedimentary facies were recognized in the core sediments according to lithology grain size composition sediment structure and microfossil assemblages while eight unconformity bounded major stratigraphic units were identified in the seismic profiles based on seismic core correlations dating data radiocarbon and optically stimulated luminescence and comparison between sedimentary cycles and sea level curves the 100 m thick strata below the seafloor were divided into three sequences corresponding to glacial interglacial sea level cycles of marine isotope stage mis 1 2 mis 3 6 and mis 7 8 sq1 sq3 from top to bottom in particular sq1 is developing in the present sea level highstand and consists mainly of deposits of transgressive systems tract tst including tide influenced river tidal flat and tide dominated estuarine facies sq2 and sq3 consist mainly of prodelta and related inner shelf facies of forced regressive systems tract frst and transgressive deposits similar to those of sq1 for all three sequences a thin sand sheet layer of open shelf facies represents deposits of highstand systems tract hst deposits of lowstand systems tract lst were typically represented by river facies in addition comprehensive analyses of seabed sand ridge distribution core sediment characteristics and ridge deposition mechanism suggest that the occurrence of a paleoestuary with transgression determined the development of a tidal sand ridge field based on all these results a conceptual stratigraphic sequence model in association with the deposition of lst tst hst and frst was constructed overall our stratigraphic framework along with a comparison of the sequence stratigraphy to that of other shelves suggested that glacial interglacial sea level fluctuations huge amounts of river sediment supply active subsidence gentle shelf topography and marine erosion processes transgression and regression controlled the mid late quaternary stratigraphic development of the ecs shelf

the contribution of geomorphological mapping to sediment transfer evaluation in small alpine catchments the assessment of sediment transfer processes is necessary to understand the hydro geomorphological functioning of small alpine watersheds prone to channelised debris flows because their occurrence often depends on the amount of debris available in the gully systems therefore sediment budgets should be studied through the identification of erosion transport and deposition processes sediment transfer processes were investigated in a small catchment by field measurements and more specifically through the application of a process based geomorphological mapping method the proposed methodology is based on data directly derived from gis analysis using high resolution dem field measurements and aerial photograph interpretations it has been conceived to estimate sediment transfer dynamics taking into account the role of different sediment stores in the torrential system the proposed geomorphological mapping methodology is quite innovative in comparison with most legend systems that are not adequate for mapping comprehensively active and complex geomorphological systems such as debris flow catchments maps representing the various sediment storages and their relationships can be used for hydro geomorphological hazard mitigation

acid rain damage to carbonate stone a quantitative assessment based on the aqueous geochemistry of rainfall runoff from stone an onsite experimental procedure was used to identify and quantify acid rain damage to carbonate stone based on the change in rain runoff chemical composition observed changes in runoff from stone are attributed to the interaction of acidic species present in the rain with the stone surface onsite data obtained during the summer and fall of 1984 at three locations in the northeastern united states indicate that carbonate stone surface recession is related to acid deposition although the study is continuing current data are not adequate to distinguish differences in the acid stone reaction between limestone and marble nor among the three study sites a single linear relation between carbonate stone surface recession the dependent variable and hydrogen ion loading to the stone surface the independent variable appears to describe the data set

methane seepage inferred from pore water geochemistry in shallow sediments in the western slope of the mid okinawa trough abstract widely distributed cold seeps are crucial sources of carbon to the seawater whereas anaerobic oxidation of methane aom and precipitation of authigenic carbonate might change the compositions of the methane rich fluids and thus reduce the outputs of dissolved carbon to seawater in this work we analyze the pore water compositions of four gravity cores with high methane concentration abnormalities in pore water or in overlying seawater in the western slope of the mid okinawa trough for the northern research area active weak methane seepage through the seafloor is identified in the vicinity of mud volcanoes sites c01 and c10 and strong emissions of gas and fluids may occur in the central mud volcanoes in a submarine canyon at the south c23 site exhibits rarely methane seepage while high rate transportation of methane from deep sediments and associated aom are identified at site c25 where small vertical faults and gas bearing layers are developed at the surrounding aom at site c25 is indicated by 1 quasi linearly decrease of sulfate concentrations with depths 2 intense increases of dissolved inorganic carbon dic concentrations and 3 significantly negative 13c values vary from 7 2 to 26 3 of dic organoclastic degradation in the shallow sediments is not obviously recognized in the study area because of the low concentrations of nh4 as well as negligible sulfate consumption at three of the four sites our data reveal that the cold systems are one of the dic sources the fluxes are ca 11 2 mmol m2 yr to the seawater in the okinawa trough which can be tracked by high depletion of 13c 13cdic ranges from 7 2 to 26 3 vpdb

a new hierarchical bayesian approach to analyse environmental and climatic influences on debris flow occurrence abstract how can debris flow occurrences be modelled at regional scale and take both environmental and climatic conditions into account and of the two which has the most influence on debris flow activity in this paper we try to answer these questions with an innovative bayesian hierarchical probabilistic model that simultaneously accounts for how debris flows respond to environmental and climatic variables in it full decomposition of space and time effects in occurrence probabilities is assumed revealing an environmental and a climatic trend shared by all years catchments respectively clearly distinguished from residual random effects the resulting regional and annual occurrence probabilities evaluated as functions of the covariates make it possible to weight the respective contribution of the different terms and more generally to check the model performances at different spatio temporal scales after suitable validation the model can be used to make predictions at undocumented sites and could be used in further studies for predictions under future climate conditions also the bayesian paradigm easily copes with missing data thus making it possible to account for events that may have been missed during surveys as a case study we extract 124 debris flow event triggered between 1970 and 2005 in 27 catchments located in the french alps from the french national natural hazard survey and model their variability of occurrence considering environmental and climatic predictors at the same time we document the environmental characteristics of each debris flow catchment morphometry lithology land cover and the presence of permafrost we also compute 15 climate variables including mean temperature and precipitation between may and october and the number of rainy days with daily cumulative rainfall greater than 10 15 20 25 30 40 mm day 1 application of our model shows that the combination of environmental and climatic predictors explained 77 of the overall variability of debris flow occurrences in this data set occurrence probabilities depend mainly on climatic variables which explain 44 of the overall variability through the number of rainy days and maximum daily temperature this important time component in the variability of overall debris flow occurrence is shown to be responsible for a significant increase in debris flow activity between 1970 and 2005 at regional scale environmental variables which account for 33 of the overall variability includes mostly the morphometric variables of the debris flow catchments

magnetic inversion in the east china sea and okinawa trough tectonic implications abstract in order to better understand continental rifting along the eastern margin of the eurasian plate we have performed a magnetic inversion to reveal the distribution and characteristics of the belts and basins in the east china sea and okinawa trough equivalent magnetizations are obtained by assuming a constant thickness of 5 km of the magnetized layer whose top surface is assigned to the sea floor and taking into account the present day geomagnetic field because of absence of magnetic reversals in the study area a high magnetization zone can reflect a shallow and or highly magnetized basement in contrast a low magnetization zone generally corresponds to a rifted basin with thick sediments the belts in the east china sea shelf basin are in general below sea level and correspond to shallow basement with thin sediments the inversion results show that the belts are parallel and trending about n075 this regular trend suggests a simple southeastward rifting pattern of the east china sea shelf basin the belt trend changes from n075 to n095 at the eastern side of the taiwan sinzi belt southwest of the taiwan sinzi belt the belts in the ryukyu subduction system are parallel to the ryukyu trench it implies that rifting of the middle and northern okinawa trough was initiated along the eastern side of the taiwan sinzi belt then the rifting has been mainly controlled by the oblique subduction of the philippine sea plate beneath the ryukyu arc the southern end of the taiwan sinzi belt terminates at the nw se trending miyako yandang high magnetization zone the southern okinawa trough rifted since early pleistocene is distinct from the middle and northern okinawa trough by the miyako yandang high magnetization zone the southern okinawa trough consists of two rifting patterns east of 123 5 e the backarc rifting is quasi symmetric as evidenced by symmetrically high magnetization zones on both sides of the yaeyama depression in contrast west of 123 5 e the volcanism or high magnetization zones developed along existing nw se trending strike slip faults have generally occurred at the northern margin of the southern okinawa trough the ryukyu arc west of 123 5 e exhibits low magnetization reflecting its non volcanic nature of the upper crust east of 123 5 e the present day ryukyu arc volcanism is expressed by relatively high magnetization

discovery of the southwest dongsha island mud volcanoes amid the northern margin of the south china sea abstract the dongsha basin circling dongsha island that is amid the northern margin of the south china sea is characterized by thin 0 5 km cenozoic sediments veneering on thick up to 5 km mesozoic strata recently several geophysical and geological surveys including multiple channel reflection seismic sub bottom profiling and benthic dredging have been conducted on the slope southwest to the dongsha island where the water depth varies from 400 m to 2000 m a novel discovery is numerous submarine mud volcanoes of various sizes over there typically 50 200 m high and 0 5 5 km wide geophysical profiles document their unusual features e g roughly undulating seafloor high amplitude seabed reflectivity foggy hyperbolic diffractions up to 50 m in water column above seabed and internal reflection chaos and wipe out down to 2 3 km level or deeper below the seabed benthic dredging from the mud volcanoes gives abundant faunas of high diversity e g scleractinian stony coral gorgonian black coral thiophil tubeworm glass sponge bryozoan etc indicating booming chemosynthetic community among which the lophelia pertusa like coral and the euretidae like glass sponges are the first reports in the south china sea concomitantly with them there are also abundant authigenic carbonate nodules and slabs raw brecciated and breccias with bio clasts congregation besides there coexist massive mudflows and allogenic coarse grained quartz feldspar and tourmaline most likely brought out by mud volcanism geochemical analysis of the bottom water samples give dissolved methane concentration up to 4 times higher than the background average these results lend comprehensive evidences for the ongoing and historical mud volcanism the escaping methane gas is inferred to source mainly from the mesozoic strata occupying a large province of the deep water slope ca 1000 km 2 or more the mud volcanoes is prospective for gas hydrate and natural gas for the dongsha basin

geomorphology in context dispatches from the field abstract field research enables a researcher to view geomorphic systems in broader contexts than those envisioned while at a desk and can yield unanticipated insights that change the course of an investigation or affect the interpretation of results geomorphological field research often produces aha moments epiphanies that enhance understanding and lead toward more complete explanation of the processes and landforms under study this paper uses examples from aha moments in the field to demonstrate the importance of field observation as a way of gaining information about the broader contexts of research sites especially in process geomorphology spatial contexts include the scales of processes and features linkages between a study site and its surroundings and information observed in the field about other processes anthropogenic activities or unexpected factors that might affect a study temporal contexts not as evident in the field place a research site in a longer term history of changes and adjustments finally exploring an abstract set of mental contexts reveals reasons that expectations differ from the realities encountered in the field constraints and biases that a researcher may not have noted and the possibility that the unexpected can potentially advance geomorphic research time spent in the field complements scientific reductionism and provides opportunities to appreciate the richness and complexity of earth surface systems

rainfall control of debris flow triggering in the real torrent southern french prealps abstract this paper investigates the occurrence of debris flow due to rainfall forcing in the real torrent a very active debris flow prone catchment in the southern french prealps the study is supported by a 4 year record of flow responses and rainfall events from three high frequency monitoring stations equipped with geophones flow stage sensors digital cameras and rain gauges measuring rainfall at 5 min intervals the classic method of rainfall intensity duration id threshold was used and a specific emphasis was placed on the objective identification of rainfall events as well as on the discrimination of flow responses observed above the id threshold the results show that parameters used to identify rainfall events significantly affect the id threshold and are likely to explain part of the threshold variability reported in the literature this is especially the case regarding the minimum duration of rain interruption mdri between two distinct rainfall events in the real torrent a 3 h mdri appears to be representative of the local rainfall regime a systematic increase in the id threshold with drainage area was also observed from the comparison of the three stations as well as from the compilation of data from experimental debris flow catchments a logistic regression used to separate flow responses above the id threshold revealed that the best predictors are the 5 min maximum rainfall intensity the 48 h antecedent rainfall the rainfall amount and the number of days elapsed since the end of winter used as a proxy of sediment supply this emphasizes the critical role played by short intense rainfall sequences that are only detectable using high time resolution rainfall records it also highlights the significant influence of antecedent conditions and the seasonal fluctuations of sediment supply

a high resolution approach in the recent sedimentation processes at the head of zakynthos canyon western greece the recent sedimentation processes at the head of zakynthos canyon in western greece have been re examined using a dense grid of high resolution seismic reflection profiles and sediment cores the current survey has revealed three new sediment sources that contribute considerably to the filling of the canyon floor that were not detected in previous surveys these sediment sources are a a string of five large pockmarks and b a large slide both along the north killini shelf and c a canyon arcoudi canyon dissecting the central killini shelf slope furthermore the erosional depositional area which was found to lie at the centre of the canyon floor extends downslope and seems to be actively receiving material mainly from the killini side three potential salt diapir locations were found and steeper slope gradients were proved to border the canyon head in contrast to the results of the older surveys mass movements affect almost the entire part of the slopes bounding the canyon head and can be distinguished in slides mass flows and turbidity currents the subbottom structure of the canyon floor confirms this evidence since it is constructed of alternating mass flow and turbidity current deposits the sedimentation processes are obviously affected by the high seismicity of the area although salt diapirism and associated high slope inclinations ascending gas from deeper sedimentary layers and homoclinal stratification seem to be dominant contributing factors sediment sources are classified according to their priority in the filling of the canyon floor

predictions of the acoustic scattering response of free methane bubbles in muddy sediments the response of the sediments of eckernfoerde bay germany to acoustic remote sensing previously has been attributed qualitatively to gas features which were postulated to exist in situ within the sediment the existence of features as small as 0 5 mm equivalent spherical radius has now been confirmed by x ray computed tomography of cores taken and scanned at in situ pressures the interaction of an acoustic pulse from the acoustic sediment classification system ascs with this type of gassy sediment was modeled and the results are presented here the bubble scattering response model includes both the effects of nonspherical bubbles and of sediment resistance to shear deformation as expressed by the dynamic shear modulus model predictions made using the observed gas bubble distribution agree with normal incidence ascs data exhibiting extended returns i e greater than the source pulse length from the seafloor bubble layers as well as high attenuation within the bubble layers spectrograms of ascs and modeled return pulses were also similar these results suggest that the acoustic return characteristics of the near surface sediments of eckernfoerde bay are dominated by scattering from a distribution of gas bubbles with depth

a morphological study of greenschist weathering on dated coastal structures south devon uk three dated structures up to 450 years in age display the effects of coastal weathering of the greenschist of which they are constructed a variety of weathering forms is present the various topographic surfaces of the structures create variation in weathering environments and consequent weathering processes and rates weathering is enhanced by direct exposure to salt bearing spray and by humid conditions and apparently limited by direct exposure to solar radiation the maximum rates of weathering on the three surfaces approximate to 0 6 mm a 1 over this period consistent with measured contemporary weathering rates for a natural surface formed by this rock type in a nearby coastal location 1997 by john wiley sons ltd