late quaternary geological history of the dead sea area israel abstract a 34 5 m borehole which was drilled near the dead sea coast altitude 394 m in the southern part of the fan delta of wadi zeelim reveals the geological history of that area from the latest pleistocene to present the depositional time frame is based on six 14c dates and two u th dates an erosional or nondepositional period is implied by the hiatus between 21 100 yr b p u th age depth 33 m and 11 315 yr b p 14c age depth 32 m a subsequent arid phase is recorded by a 6 5 m thick layer of halite based on 14c dates this phase relates to the abrupt younger dryas cold period reported in temperate to polar regions the fragility of the environment in this region is indicated by the fact that the region experienced such a severe short aridification phase less than 1000 yr evidence of which is found widely in the desert fringes of the middle east and north africa the aragonite found in most of the holocene section indicates that the well site was covered by the lake for most of the holocene exceptions are the intervals at 0 3 and 10 14 m depths which represent low stands of the lake

the effect of base level changes and geological structures on the location of the groundwater divide as exhibited in the hydrological system between the dead sea and the mediterranean sea summary the effects of base sea or lake level changes on the location and elevation of the groundwater divide were examined in the hydrological system between the mediterranean sea and the dead sea steady state simulations were conducted with a 1 d analytical model and transient conditions were simulated using feflow groundwater modeling software two hydrological scenarios were simulated a a transition to a new steady state following the expected drop of 150 m of the dead sea level and b the time of the precursor of the dead sea lisan lake some 20 000 years ago when the lake level was about 250 m above the present day dead sea level and the mediterranean sea level was 120 m below its present one the results of the simulations show that the dead sea level drop has led to a progressive decline in the groundwater level up to several kilometers inland from the shoreline the hydraulic gradient increases and thus the discharge to the lake also increases at the expense of the storage and also due to a small enlargement of the recharge zone by a 600 m shift of the divide broadly the subsurface hydrological system is compartmentalized into several sections separated by low permeability fold structures bounding the mountainous uplands most of the groundwater recharge occurs in the uplands given this geometry and the available water level measurements analytical and numerical modeling results show that only changes in the dead sea level and recharge rate result in dramatic changes for the scenarios examined limited by the low permeability folds the effects of the dead sea level on the groundwater level are most pronounced in the vicinity of the judea desert lowland the folds also greatly limit migration of the groundwater divide associated with changes in the dead sea level transient simulations show a peak increase of 30 in the dead sea groundwater flux in 75 years resulting from drainage of lowland aquifers after more than 500 years the groundwater flux is expected to return to values no more than 4 higher than at the beginning of the simulation this small net increase is consistent with the small shift in the groundwater divide

impact of halite dissolution subsidence on quaternary fluvial terrace development case study of the huerva river ebro basin ne spain abstract this paper analyses the control of evaporite dissolution subsidence on the evolution of the lower 30 km long reach of the huerva river up to its confluence with the ebro river in the study area the huerva river flows across different interfingered lithofacies of the subhorizontally lying ebro basin fill 1 shales and sandstones upstream of cadrete 2 evaporites dominated by gypsum between cadrete and cuarte 3 gypsum with glauberite and halite units in the subsurface downstream of cuarte the halite shows a marked downvalley increase in thickness twelve terrace levels and seven pediment levels correlative to some of the terraces have been mapped in the studied area upstream of cadrete the terrace deposits with a relatively constant thickness less than 4 m and overlying unsoluble bedrock remain undeformed between cadrete and cuarte the deposits of some terraces show local thickening 60 m thick terrace alluvium that fills a 5 km long trough generated by synsedimentary subsidence phenomena caused primarily by the interstratal dissolution of halite the older terraces t1 to t4 show slight thickening 18 m and locally truncate paleocollapse structures ascribed to the interstratal karstification of halite beds the intermediate terraces t5 to t7 correspond to degradation surfaces that grade downstream of cuarte into aggradation flights underlain by the abruptly thickened deposits that fill this 5 km long dissolution trough subsidence migrated episodically downstream during the generation of these terraces and the subsidence aggradation rate was probably large enough to induce a base level drop and knickpoint migration upstream generating strath terraces with convergent longitudinal profiles the sedimentological changes that show the thickened terrace deposits in the subsidence area high proportion of overbank fines 60 including palustrine facies gravel channels with lower width depth ratio multiple fining upward cycles decrease in the calibre of the channel gravels indicate a change in the channel pattern from braided to meandering due to the lowering of the valley slope in the reach affected by subsidence some of the anomalous features of the lower terraces t8 to t12 attributable to dissolution subsidence include 1 steepening of the t8 terrace profile 2 change of the t10 terrace from degradational to aggradational downstream cuarte and 3 thickening recorded beneath the t11 terrace surface

the dead sea sinkhole hazard geophysical assessment of salt dissolution and collapse abstract a geophysical approach is presented for analyzing processes of subsurface salt dissolution and associated sinkhole hazard along the dead sea the implemented methods include seismic refraction srfr transient electromagnetic method tem electric resistivity tomography ert and ground penetration radar gpr the combination of these methods allows the delineation of the salt layer boundaries estimating its porosity distribution finding cavities within the salt layer and identifying deformations in the overlying sediments this approach is shown to be useful for anticipating the occurrence of specific sinkholes as demonstrated on both shores of the dead sea these sinkholes are observed mainly along the edge of a salt layer deposited during the latest pleistocene when lake lisan receded to later become the dead sea this salt layer is dissolved by aggressive water flowing from adjacent and underlying aquifers which drain to the dead sea sinkhole formation is accelerating today due to the rapid fall of the dead sea levels during the last 30 years caused by anthropogenic use of its water

a review on natural and human induced geohazards and impacts in karst karst environments are characterized by distinctive landforms related to dissolution and a dominant subsurface drainage the direct connection between the surface and the underlying high permeability aquifers makes karst aquifers extremely vulnerable to pollution a high percentage of the world population depends on these water resources moreover karst terrains frequently underlain by cavernous carbonate and or evaporite rocks may be affected by severe ground instability problems impacts and hazards associated with karst are rapidly increasing as development expands upon these areas without proper planning taking into account the peculiarities of these environments this has led to an escalation of karst related environmental and engineering problems such as sinkholes floods involving highly transmissive aquifers and landslides developed on rocks weakened by karstification the environmental fragility of karst settings together with their endemic hazardous processes have received an increasing attention from the scientific community in the last decades concurrently the interest of planners and decision makers on a safe and sustainable management of karst lands is also growing this work reviews the main natural and human induced hazards characteristic of karst environments with specific focus on sinkholes floods and slope movements and summarizes the main outcomes reached by karst scientists regarding the assessment of environmental impacts and their mitigation

viscoelastic damage modeling of sinkhole formation abstract the sinkholes along the dead sea coast are observed in two main sedimentary environments alluvial fan sinkholes which usually form abruptly as deep 20 m and narrow 3 m sinkholes and mud flat sinkholes which usually form as shallow a few centimeters and wide 5 m sinkholes and deepen later the mechanical collapse of all sinkholes is triggered by cavities created by the dissolution of an underlying salt layer by relatively fresh groundwater the processes attributed to the mechanical formation of the sinkholes are viscous flow and brittle fracture failure we use a two dimensional viscoelastic damage rheology numerical model to quantitatively explain the brittle and ductile aspects of collapsed sinkholes three cases of the rheology of the collapsed sediments are simulated 1 damage controlled failure 2 viscoelastic controlled failure and 3 an intermediate damage viscoelastic case results show that viscoelasticity cannot be the sole process acting on the deformed layer because all sinkholes are characterized by sharp boundaries the damage accumulation progresses until arched cavities are created in the soil layer because of the geometric heterogeneity of the layer represented by the heterogeneity of the mesh smaller blocks continue to fall after the first breakup into the cavity advancing the arched cavity upwards this propagation finally stops when the cavity is shallow enough to hold the irregular arch the combination of these two processes creates competition within the stress reduction mechanism that may lead to either magnified or reduced deformation the deformation is magnified in high shear stress locations where the dispersion of the viscous flow spreads damage failure and it is reduced in low shear stress locations where viscous flow disperses shear stress before the onset of damage

oceanographic control of diatom abundances and species distributions in surface sediments of the tropical and southeast atlantic abstract this paper is a descriptive account of the diatomaceous component of pelagic sediments from the tropical and southeast atlantic ocean geographic patterns of diatom abundances whole and fragment forms per gram major species relative abundances and diatom assemblages resolved by q mode factor analysis are presented comparisons drawn to sea surface temperature salinity and productivity distributions suggest that i diatom abundances primarily reflect surface productivity with no apparent dissolution effects due to water depth ii relative abundances of major species vary in their ecologic dependence but do reflect major oceanographic features of the surface waters and iii of the five diatom assemblages resolved four finely delineate the complexity of the low latitude oceanography these assemblages in decreasing order of statistical importance are associated with 1 warm waters of moderate to high primary productivity 2 the oceanward margin of the benguela current a region of high primary production with a maximum in austral summer 3 low salinity waters off the mouths of the zaire and niger rivers and 4 subtropical to tropical waters of lower productivity mostly in the western equatorial atlantic the fifth factor represents the equatorward advection of subantarctic to antarctic diatoms by deep ocean currents

incision of alluvial channels in response to a continuous base level fall field characterization modeling and validation along the dead sea abstract the dramatic lake level drop of the dead sea during the twentieth century 30 m provides a field scale experiment in transport limited incision of gravel bed channels in response to quasi continuous base level fall at approximately constant rate we apply a one dimensional numerical incision model based on a linear diffusion equation to seven ephemeral channels draining into the dead sea the model inputs include the measured twentieth century lake level curve annual shoreline location i e annual channel lengthening following the lake level drop reconstructed longitudinal profiles of each of the channels based on mapped and surveyed terraces and the current profiles of the active channels the model parameters included the diffusion coefficient and the upstream derived sediment flux both were first calibrated using a set of longitudinal profiles of known ages and then validated using additional sets of longitudinal profiles the maximum at station total incision observed at each of the studied channels was significantly less then the total lake level drop and varied in response to both drainage area and lake bathymetry the model applied predicted degradation rates and the pattern of degradation with high accuracy this suggests that sediment flux in the modeled channels is indeed linearly dependent on slope further support for this linear dependency is provided by a linear correlation between the diffusion coefficient and the mean annual rain volume over each basin a proxy for discharge the model presented could be a valuable tool for planning in rapid base level fall environments where incision may risk infrastructure

salt dissolution and sinkhole formation along the dead sea shore 1 the formation of sinkholes at the dead sea area reflects subsurface cavities formed by salt dissolution this dissolution is related to the recession of the dead sea the groundwater level and the fresh saline water interface along the shore decline at a similar rate to the rate of the dead sea recession and brines that used to occupy layers below this interface are flushed out by freshwater our finite element modeling shows that dissolution of this salt layer is a plausible mechanism to explain the rapid creation of subsurface holes that collapse and form sinkholes the positive feedback between the rate of flow the rate of chemical reaction and the change in permeability accelerates the dissolution processes and might result in reactive infiltration instability which is manifested in fingers of cavities into which fluid is channeled and salt is dissolved the spacing between the sinkholes and the rate of their creation is controlled by several factors including properties of lineaments faults incoming groundwater flux the salinity of the incoming groundwater the rate of dissolution the effective specific surface area the permeability of the salt and clay layers the permeability porosity relation the dispersivity and the thickness of the layers we show that the creation of sinkholes occurs only under specific conditions these conditions must cause an unstable dissolution front which then causes formation of cavities and eventually sinkholes the simulations which utilized the best estimated parameters of the studied area yield results that are similar to those exhibited in the field

high resolution insar constraints on flood related subsidence and evaporite dissolution along the dead sea shores interplay between hydrology and rheology abstract sinkhole generation and land subsidence are commonly attributed to dissolution of subsurface layers by under saturated groundwater and formation of cavities along the dead sea ds shorelines this process also involves seasonal flash floods that are drained into the subsurface by existing and newly formed sinkholes we quantify the contribution of flash floods to salt dissolution and land subsidence using high resolution interferometric synthetic aperture radar insar subsidence rates during a 3 year period 2012 2015 were calculated from 57 cosmo skymed x band interferograms bracketing major flood events and intra flood periods in 21 sinkhole sites the sites are located within channels and alluvial fans along the western shores of the dead sea israel the observed subsidence reaches maximum rates of 2 5 mm day accumulating in specific sites to 500 mm year in most of the sinkhole sites a gradual increase in the annual subsidence rate is observed during the 3 year study period three different modes of response to floods were observed 1 sites where floodwater is not directly channeled into sinkholes do not respond to floods 2 sites adjacent to active channels with sinkholes are unaffected by specific floods but their subsidence rates increase gradually from early winter to mid summer and decay gradually until the following winter and 3 sites in active channels with sinkholes are characterized by an abrupt increase in subsidence rates immediately after each flood by a factor of up to 20 and by a subsequent quasi exponential subsidence decay over periods of several months in these latter sites subsidence rates after each flood are temporally correlated with alternating groundwater levels in adjacent boreholes the rapid rise in groundwater head following floods increases the hydraulic gradient of the under saturated groundwater and hence also the groundwater discharge and the dissolution rate of the subsurface salt layer a subsequent quasi exponential water level drop results in similar deceleration in dissolution and subsidence rates with a similar characteristic decay time of about 150 days the observed subsidence decay pattern may also be explained by viscoelastic relaxation of the overburden in response to instantaneously formed dissolution cavities utilizing a kelvin viscoelastic model we show that the contribution of this process is most probably

hydrochemistry and solution rates in gypsum karst case study from the western ukraine the gypsum karst in the western ukraine spreads through a large territory covering more than 20 000 km2 and is represented by a range of stages evolutionary types from deep seated through subjacent to entrenched correspondingly hydrogeological settings of karst development circulation patterns and chemical characteristics of groundwaters differ substantially between the respective areas based on 1 800 analyses this paper summarises hydrochemistry of the gypsum hosting miocene aquifer the majority of sampling has been performed in conjunction with a study regime of gypsum solution rates by means of standard tablets in this study which included 53 tablet stations representing varying conditions of water rock interaction 644 weight loss measurements were made over the period 1984 1992 the highest rates are characteristic of entrenched karst although active dissolution is localised along well defined sinking streams with short underground courses rare vertical percolation paths and the water table lower but still quite substantial rates are characteristic of subjacent and deep seated confined karst however the overall dissolution removal is greater due to higher flow through the gypsum and the larger area of rock solvent contact the results are generalised in order to derive the approximate solution rates characterising major situations and to be suitable for modeling purposes

sinkhole swarms along the dead sea coast reflection of disturbance of lake and adjacent groundwater systems more than a thousand sinkholes have developed along the western coast of the dead sea since the early 1980s more than 75 of them since 1997 all occurring within a narrow strip 60 km long and 1 km wide this highly dynamic sinkhole development has accelerated in recent years to a rate of 150 200 sinkholes per year the sinkholes cluster mostly over specific sites up to 1000 m long and 200 m wide which spread parallel to the general direction of the fault system associated with the dead sea transform research employing borehole and geophysical tools reveals that the sinkhole formation results from the dissolution of an 10 000 yr old salt layer buried at a depth of 20 70 m below the surface the salt dissolution by groundwater is evidenced by direct observations in test boreholes these observations include large cavities within the salt layer and groundwater within the confined subaquifer beneath the salt layer that is undersaturated with respect to halite moreover the groundwater brine within the salt layer exhibits geochemical evidence for actual salt dissolution na cl 0 5 0 6 compared to na cl 0 25 in the dead sea brine the groundwater heads below the salt layer have the potential for upward cross layer flow and the water is actually invading the salt layer apparently along cracks and active faults the abrupt appearance of the sinkholes and their accelerated expansion thereafter reflects a change in the groundwater regime around the shrinking lake and the extreme solubility of halite in water the eastward retreat of the shoreline and the declining sea level cause an eastward migration of the fresh saline water interface as a result the salt layer which originally was saturated with dead sea water over its entire spread is gradually being invaded by fresh groundwater at its western boundary which mixes and displaces the original dead sea brine accordingly the location of the western boundary of the salt layer which dates back to the shrinkage of the former lake lisan and its transition to the current dead sea constrains the sinkhole distribution to a narrow strip along the dead sea coast the entire phenomenon can be described as a hydrological chain reaction it starts by intensive extraction of fresh water upstream of the dead sea continues with the eastward retreat of the lake shoreline which in turn modifies the groundwater regime finally triggering the formation of sinkholes

a 20 year varve record of siliceous phytoplankton variability in the central gulf of california abstract year to year variability in the structure of the preserved siliceous phytoplankton assemblage is reconstructed from a box core retrieved from the varved sediments along the guaymas slope of the gulf of california a 20 year record from 1953 through 1972 is obtained from interpretation of the varve stratigraphy supported by 210 pb and 228 th dating ecological time series derived from microfossil analysis show a strong coherence with interannual sea level anomalies indicating a response to large scale climatic variability associated with the el nino southern oscillation phenomenon el nino periods are generally marked by increases in preserved abundances of the total siliceous assemblage and in particular by greater numbers of individuals within species whose distribution is limited to tropical and subtropical waters

radar interferometry and its application to changes in the earth s surface geophysical applications of radar interferometry to measure changes in the earth s surface have exploded in the early 1990s this new geodetic technique calculates the interference pattern caused by the difference in phase between two images acquired by a spaceborne synthetic aperture radar at two distinct times the resulting interferogram is a contour map of the change in distance between the ground and the radar instrument these maps provide an unsurpassed spatial sampling density 100 pixels km 2 a competitive precision 1 cm and a useful observation cadence 1 pass month 1 they record movements in the crust perturbations in the atmosphere dielectric modifications in the soil and relief in the topography they are also sensitive to technical effects such as relative variations in the radar s trajectory or variations in its frequency standard we describe how all these phenomena contribute to an interferogram then a practical summary explains the techniques for calculating and manipulating interferograms from various radar instruments including the four satellites currently in orbit ers 1 ers 2 jers 1 and radarsat the next chapter suggests some guidelines for interpreting an interferogram as a geophysical measurement respecting the limits of the technique assessing its uncertainty recognizing artifacts and discriminating different types of signal we then review the geophysical applications published to date most of which study deformation related to earthquakes volcanoes and glaciers using ers 1 data we also show examples of monitoring natural hazards and environmental alterations related to landslides subsidence and agriculture in addition we consider subtler geophysical signals such as postseismic relaxation tidal loading of coastal areas and interseismic strain accumulation we conclude with our perspectives on the future of radar interferometry the objective of the review is for the reader to develop the physical understanding necessary to calculate an interferogram and the geophysical intuition necessary to interpret it

styles and rates of long term denudation in carbonate terrains under a mediterranean to hyper arid climatic gradient abstract carbonate minerals unlike silicates have the potential to dissolve almost completely and with high efficiency thus in carbonate terrains denudation rate and style the governing process of denudation mechanical or chemical should be more sensitive to climatic forcing using 36 cl measurements in 39 carbonate bedrock and sediment samples we calculate long term denudation rates across a sharp climatic gradient from mediterranean to hyper arid conditions our samples were collected along the arugot watershed which drains the eastern flank of the judea range central israel to the dead sea and is characterized by a pronounced rain shadow denudation rates of flat lying bedrock outcrops sampled along interfluves differ by an order of magnitude from 20 mm ka 1 in the mediterranean zone to 1 3 mm ka 1 in the hyper arid zone these rates are strongly correlated with precipitation and thus reflect the importance of carbonate mineral dissolution in the overall denudation process in contrast denudation rates of steep bedrock surfaces depend on the hillslope gradient but only in the hyper arid climate zone indicating that mechanical processes dominate the overall hillslope denudation within this zone the dominance of slope dependent mechanical erosion in the hyper arid zone is also reflected by an increase in spatially average denudation rates from 17 19 mm ka 1 in the mediterranean semi arid zones to 21 25 mm ka 1 in the hyper arid zone these higher rates are attributed to clast contribution from steep slopes under arid climate this suggests an increased importance of mechanical processes to the overall denudation in the hyper arid zone we demonstrate that the transition between chemically dominated denudation to mechanically dominated denudation occurs between 100 and 200 mm of mean annual precipitation long term denudation rates across the judea range indicate that between mediterranean and hyper arid climates chemical weathering rates are limited by precipitation nevertheless in more humid climates chemical weathering rates are apparently limited by the rates of carbonate mineral dissolution this study demonstrates that carbonate terrains have the capacity to shift between mechanically and chemically dominated denudation in response to changes in precipitation similar transitions in response to changes in temperature or the level of tectonic activity have been previously reported we suggest that the abrupt nature of such transitions can be primarily attributed to the efficiency of carbonate dissolution processes and the competition between surface and subsurface drainage systems in carbonate terrains

aquifer characteristics derived from the interaction between water levels of a terminal lake dead sea and an adjacent aquifer the water level of the dead sea a terminal hypersaline lake total dissolved solids approximately 340 g l has decreased at an average rate of 0 5 m yr since 1960 and by 0 8 m yr between 1981 and 1989 the dramatic long term water level variation of the dead sea and the seasonal short term fluctuations are accompanied by parallel variations of groundwater levels in an adjacent aquifer a general methodology based on a simplified yet reliable one dimensional flow model together with continuous measurements of groundwater levels in observation wells enables analysis of aquifer structural and hydraulic properties furthermore this analysis enables prediction of future groundwater levels in unconfined and confined aquifers due to future changes in lake levels

ocean swells along the global coastlines and their climate projections for the twenty first century abstractremotely generated swell waves are the dominant contributor of the coastal wind wave climate along most of the world coastlines in this work we describe the characteristics of swells from

are sedimentary salt layers always impermeable we report here for the first time the finding of a 24 to 31 m deep 10 000 y old water saturated and highly hydraulically conductive salt layer composed of idiomorphic halite crystals in the coastal area of the dead sea the high hydraulic conductivity of the layer was evidenced by laboratory and field tests and by the rapid fluctuations of the water table in a well penetrating the layer following variations in the water level of the dead sea such layers may lead to intensive and rapid flow of water and non polar liquids

on concepts and methods for the estimation of dissolutional denudation rates in karst areas abstract the paper discusses methods and principles used to estimate dissolutional denudation rates in karst areas surface lowering can be measured directly by micro erosion meters or calculated from the mass loss in rock tablets exposed to dissolution in different environments indirect approaches are based on the measurements of solute load leaving the catchment area geomorphological investigations and methods of cosmogenic nuclides particularly 36 cl calculations based on the solute load measurements generally give higher denudation rates than direct measurements on the surface of limestone terrains this can be explained by the fact that only about 30 of water s dissolution potential is used on the exposed surfaces and the rest is done deeper in the fracture system the role of endokarst dissolution is demonstrated with a denudation model of rock column where dissolution rate depends solely on the distance from the surface the denudation rates of a uniform rock column approach maximal when the thickness of the removed rock is about twice an e folding length for the dissolution rates the model also gives possible mechanisms for differential denudation in regions with different infiltration intensity and fracture density

variability of the winter wind waves and swell in the north atlantic and north pacific as revealed by the voluntary observing ship data this paper analyses secular changes and interannual variability in the wind wave swell and significant wave height swh characteristics over the north atlantic and north pacific on the basis of wind wave climatology derived from the visual wave observations of voluntary observing ship vos officers these data are available from the international comprehensive ocean atmosphere data set icoads collection of surface meteorological observations for 1958 2002 but require much more complicated preprocessing than standard meteorological variables such as sea level pressure temperature and wind visual vos data allow for separate analysis of changes in wind sea and swell as well as in significant wave height which has been derived from wind sea and swell estimates in both north atlantic and north pacific midlatitudes winter significant wave height shows a secular increase from 10 to 40 cm decade 1 during the last 45 yr however in the north atlantic the patterns of trend changes for wind sea and swell are quite different from each other showing opposite signs of changes in the northeast atlantic trend patterns of wind sea swell and swh in the north pacific are more consistent with each other qualitatively the same conclusions hold for the analysis of interannual variability whose leading modes demonstrate noticeable differences for wind sea and swell statistical analysis shows that variability in wind sea is closely associated with the local wind speed while swell changes can be driven by the variations in the cyclone counts implying the importance of forcing frequency for the resulting changes in significant wave height this mechanism of differences in variability patterns of wind sea and swell is likely more realistic than the northeastward propagation of swells from the regions from which the wind sea signal originates

the lowest place on earth is subsiding an insar interferometric synthetic aperture radar perspective since the early 1990s sinkholes and wide shallow subsidence features wssfs have become major problems along the dead sea shores in israel and jordan sinkholes are readily observed in the field but their locations and timing are unpredictable wssfs are often difficult to observe in the field however once identified they delineate zones of instability and increasing hazard in this study we identify characterize and measure rates of subsidence along the dead sea shores by the interferometric synthetic aperture radar insar technique we analyze 16 sar scenes acquired during the years 1992 to 1999 by the european remote sensing ers 1 and ers 2 satellites the interferograms span periods of between 2 and 71 months wssfs are observed in the lisan peninsula and along the dead sea shores in a variety of appearances including circular and elongate coastal depressions a few hundred meters to a few kilometers in length depressions in ancient alluvial fans and depressions along salt diapir margins phase differences measured in our interferograms correspond to subsidence rates generally in the range of 0 20 mm yr within the studied period with exceptional high rates that exceed 60 mm yr in two specific regions during the study period the level of the dead sea and of the associated ground water has dropped by 6 m this water level drop within an aquifer overlying fine grained marly layers would be expected to have caused aquifer system consolidation resulting in gradual subsidence comparison of our insar observations with calculations of the expected consolidation shows that in areas where marl layers are known to compose part of the upper 30 m of the profile estimated consolidation settlements are of the order of the measured subsidence our observations also show that in certain locations subsidence appears to be structurally controlled by faults seaward landslides and salt domes gradual subsidence is unlikely to be directly related to the sinkholes excluding the use of the wssfs features as predictable precursors to sinkhole formation

anticipating and managing engineering problems in the complex karst environment karst environments are characterized by distinctive landforms and a peculiar hydrologic behavior dominated by subsurface drainage karst systems can be extremely complex heterogeneous and unpredictable due to the wide range of geological and hydrological controlling factors the great variability results in serious problems for engineers and in difficulties to characterize the karstified rock masses and in designing the engineering works to be performed the design and development of engineering projects in karst environments require specific approaches aimed at minimizing the detrimental effects of hazardous processes and environmental problems further karst aquifers that provide approximately 20 25 of the world s drinking water are extremely vulnerable to pollution due to the direct connection between the surface and the subsurface drainage the rapidity of the water flow in conduit networks and the very low depuration capability sinkholes are the main source of engineering problems in karst environments and may cause severe damage in any human structure the strategies and solutions that may be applied to mitigate sinkhole problems are highly variable and largely depend on the kind of engineering structure the karst setting and the typology and size of the sinkholes a sound geological model properly considering the peculiarities of karst and its interactions with the human environment is essential for the design of cost effective and successful risk reduction programs due to the unique direct interaction between surface and subsurface environments and the frequent ground instability problems related to underground karstification management of karst environments is a very delicate matter disregarding such circumstances in land use planning and development inevitably results in severe problems with high economic impacts karst environments require specific investigation methods in order to properly manage and safeguard the sensitive geo ecosystems and natural resources associated with them

a displaced neritic diatom delphineis karstenii in pelagic sediments of the southeast atlantic this paper documents the occurrence ofdelphineis karstenii a neritic diatom in pelagic sediments of the northern cape and southern angola basins southeast atlantic ocean maximum abundances are found in the southern angola basin although the source area appears to be the diatomaceous sediments which blanket much of the namibian continental shelf the observed pattern implies large scale displacement ofd karstenii valves first northward along the continental margin and then westward into deep waters transport evidently occurs in the surface waters of the benguela current which flow northward along the namibian coast and then turn westward away from the coast of angola and out into the angola basin these observations suggest thatdelphineis valves and perhaps other shallow water diatom valves may be displaced downslope on other continental margins failure to recognize such displacement could lead to incorrect ecological and paleoecological interpretations

a genetic classification of sinkholes illustrated from evaporite paleokarst exposures in spain this contribution analyses the processes involved in the generation of sinkholes from the study of paleokarst features exposed in four spanish tertiary basins bedrock strata are subhorizontal evaporites and in three of the basins they include halite and glauberite in the subsurface our studies suggest that formation of dolines in these areas results from a wider range of subsidence processes than those included in the most recently published sinkhole classifications a new genetic classification of sinkholes applicable to both carbonate and evaporite karst areas is thus proposed with the exception of solution dolines it defines the main sinkhole types by use of two terms that refer to the material affected by downward gravitational movements cover bedrock or caprock and the main type of process involved collapse suffosion or sagging sinkholes that result from the combination of several subsidence processes and affect more than one type of material are described by combinations of the different terms with the dominant material or process followed by the secondary one e g bedrock sagging and collapse sinkhole the mechanism of collapse includes any brittle gravitational deformation of cover and bedrock material such as upward stoping of cavities by roof failure development of well defined failure planes and rock brecciation suffosion is the downward migration of cover deposits through dissolutional conduits accompanied with ductile settling sagging is the ductile flexure of sediments caused by differential corrosional lowering of the rockhead or interstratal karstification of the soluble bedrock the paleokarsts we analysed suggest that the sagging mechanism not included in previous genetic classifications plays an important role in the generation of sinkholes in evaporites moreover collapse processes are more significant in extent and rate in areas underlain by evaporites than in carbonate karst primarily due to the greater solubility of the evaporites and the lower mechanical strength and ductile rheology of gypsum and salt rocks

variability of holocene diatom assemblages in laminated sediments near walvis bay southwest africa abstract silica rich muds along the southwest african coast contain a mixture of neritic and oceanic diatoms lighter colored laminae contain a higher percentage of neritic forms and reflect strong upwelling and augmented primary productivity in contrast darker laminae indicate reduced upwelling and incursion of lower nutrient offshore waters the ratio of delphineis karstenii to the thalassiosira eccentrica group is generally higher in lighter colored laminae and thus appears to increase with increasing primary productivity the laminae are probably varves with lighter laminae forming during austral spring and summer when upwelling is most frequent and most intense and darker laminae forming in the winter months the diatomaceous muds appear to contain a detailed record of climatic change during the late holocene

collapse sinkholes and radar interferometry reveal neotectonics concealed within the dead sea basin 1 the dead sea ds pull apart basin is one of the more seismically active segments of the ds transform plate boundary in the last decade hundreds of collapse sinkholes have been formed along the ds coastlines in israel and jordan causing severe damage to the regional infrastructure the formation of these sinkholes is attributed to the dissolution of a buried salt layer by fresh groundwater due to the drop of the ds and the associated groundwater levels here we show that the sinkhole distribution combined with gradual land subsidence measured by radar interferometry insar track young fault systems suspected as active concealed within the fill of the ds rift this notion is supported by 1 sinkholes clustering along discrete lineaments with a striking trend similarity to that of the exposed rift margin faults 2 prominent discontinuities in seismic reflection profiles offsetting young sediments several kyrs old below sinkhole lines and 3 straight boundaries of gradual subsidence features that coincide with or parallel sinkhole lines combined the sinkhole lineaments and the insar measurements reveal a zigzag pattern of buried faults within the ds rift fill

self accelerated development of salt karst during flash floods along the dead sea coast israel we document and analyze the rapid development of a real time karst system within the subsurface salt layers of the ze elim fan dead sea israel by a multidisciplinary study that combines interferometric synthetic aperture radar and light detection and ranging measurements sinkhole mapping time lapse camera monitoring groundwater level measurements and chemical and isotopic analyses of surface runoff and groundwater the 1 m yr drop of dead sea water level and the subsequent change in the adjacent groundwater system since the 1960s resulted in flushing of the coastal aquifer by fresh groundwater subsurface salt dissolution gradual land subsidence and formation of sinkholes since 2010 this process accelerated dramatically as flash floods at the ze elim fan were drained by newly formed sinkholes during and immediately after these flood events the dissolution rates of the subsurface salt layer increased dramatically the overlying ground surface subsided a large number of sinkholes developed over short time periods hours to days and salt saturated water resurged downstream groundwater flow velocities increased by more than 2 orders of magnitudes compared to previously measured velocities along the dead sea the process is self accelerating as salt dissolution enhances subsidence and sinkhole formation which in turn increase the ponding areas of flood water and generate additional draining conduits to the subsurface the rapid terrain response is predominantly due to the highly soluble salt it is enhanced by the shallow depth of the salt layer the low competence of the newly exposed unconsolidated overburden and the moderate topographic gradients of the ze elim fan

biogenic and abiogenic components of laminated hemipelagic sediments in the central gulf of california abstract alternating light and dark submillimeter to millimeter thick layered sediments rhythmites are found along the slopes of the central and southern gulf of california where a strong oxygen minimum zone intersects the sediment water interface two short intervals of distinct alternations were sampled lamina by lamina from two cores in the central gulf both cores are from the slope of the guaymas basin one core is from the mainland side the other core is from the baja side each lamina sample was analyzed for its opal micro floral assemblage textural character trace metal and bulk chemical cu mn fe ni zn ca k al sio2 and c org content and mineralogy on both sides of the gulf the light laminae contain more diatom frustules up to 90 and less terrigenous and organic material than the dark laminae the sediment is predominantly silt sized the dark laminae contain more terrigenous material which is primarily clay size on both sides of the gulf the light laminae apparently represent sedimentation during the dry winter season of northwesterly winds whereas the dark laminae represent the wet summer season of southeasterly winds

sinkhole precursors along the dead sea israel revealed by sar interferometry the water level in the dead sea israel and jordan has been dropping at an increasing rate since the 1960s exceeding one meter per year during the last decade this drop has triggered the formation of sinkholes and widespread land subsidence along the dead sea shoreline resulting in severe economic loss and infrastructural damage in this study the spatiotemporal evolution of sinkhole related subsidence and the effect of human activities and land perturbation on sinkhole development are examined through interferometric synthetic aperture radar measurements and field surveys conducted in israel during 2012 interferograms are generated using cosmo skymed satellite images and a high resolution 0 5 m pixel elevation model obtained from lidar measurements as a result of this unique combination of high resolution data sets millimeter scale subsidence has been resolved in both natural and human disturbed environments precursory subsidence over a period of a few months occurred before the collapse of all three sinkhole sites reported in this study the centers of the subsiding areas migrated possibly due to progressive dissolution and widening of the underlying cavities filling of newly formed sinkholes with gravel and mud injections into drill holes seem to enhance land subsidence enlarge existing sinkholes and form new sinkholes apart from shedding light on the mechanical process the results of this study may pave the way for the implementation of an operational sinkhole early warning system

diatom taphocoenoses in the coastal upwelling area off south west africa abstract the diatom floral composition of 124 sediment samples from the south east atlantic records the influence of coastal upwelling on sediment composition off south west africa inner shelf samples between 19 and 24 s are rich in diatom valves and the patterns of diatom species distribution in these samples are related to the coastal upwelling process comparison with recent phytoplankton data shows that the sediment assemblages preserve many of the important species of the diatom biocoenoses including chaetoceros resting spores delphineis karstenii thalassiosira eccentrica and thalassionema nitzschioides delphineis karstenii a pioneer species in enriched coastal water occurs nearshore and chaetoreros resting spores are widespread with highest relative abundance values in some more offshore samples the abundance of the thalassiosira eccentrica group and of thalassionema nitzschioides in sediment samples in and near walvis bay reflects the recurrence of intense upwelling off this part of the coast an abundance of large centric species has been reported in hydrological conditions characteristic of newly upwelled waters and correspondingly actinocyclus octonarius and some large coscinodiscus species occur in the sediments in nearshore patches or belts

hydrology and denudation rates of halite karst salt karst terrains exist mainly in arid climates where rock salt outcrops may escape complete destruction by dissolution such is the case with mount sedom on the sw shore of the dead sea one of the most arid parts of israel many small catchments developed over the relatively insoluble cap rock which overlies the highly soluble rock salt the catchments were surveyed and classified some 57 of the surface area is drained by an underground karst system water samples from various points in the system were analysed and water development was inferred waters in cave conduits do not reach saturation during flood flow unless the water is ponded for at least several hours based on the available evidence regional karst denudation is tentatively estimated to be about 0 5 0 75 mm year 1 occurring mainly within the rock salt

the decay rate of ocean swell observed by altimeter abstractaltimeter data from transects across the southern ocean are analyzed to determine the decay of oceanic swell the resulting decay rate is shown to be proportional to wavenumber squared and swell amplitude cubed such a decay relationship is consistent with turbulent interaction with the background either in the air or water the present data cannot distinguish between these two cases the results are consistent with the limited previous studies and present a source term suitable for use in wave prediction models

evolution of sinkholes over wink texas observed by high resolution optical and sar imagery abstract two caprock and cover collapse sinkholes wink sinks 1 and 2 in winkler county texas collapsed in 1980 and 2002 respectively they are located in a region underlain by the salado formation on the eastern edge of the delaware basin the sinkhole collapses were associated with intense hydrocarbon drilling and production activities in the hendrick oilfield production records and prior investigations imply the sinkholes developed after salt dissolution due to freshwater intrusion cavity formation roof failure and successive upward cavity migration high resolution 1 m aerial photography shows the ensuing expansion of wink sink 2 from 2002 through 2010 and relative stability of the ground surface after 2010 very high resolution 25 cm staring spotlight mode terrasar x reveals the spatiotemporal details of wink sinkhole deformations the vicinities around the two existing sinkholes wink sinks 1 2 deformed at a rate of 5 cm yr in line of sight los direction from october 2015 to march 2016 and the deformation was possibly caused by the gradual deposit of the debris from overlying unconsolidated alluvium and santa rosa sandstones infilling the cavity after the sinkhole collapse specifically the largest deformation of 53 cm yr in los direction was found 1 km east of wink sink 2 our study suggests that severe drought in 2011 widened and created fractures as well as ground fissures in the rocks overlying and underlying the salt formation due to the increased effective stress fractures ground fissures and the abandoned unplugged boreholes or improperly completed wells opened one or more vertical pathways of freshwater from groundwater flow and precipitation toward the salt bed finally causing the rapid salt dissolution and the opening of new cavities to explain the onset of a rapid subsidence near the wink sinkholes our study considers the combined effect of natural perturbation i e drought rock fractures ground fissures subsurface drainage precipitation and anthropogenic effects i e improper well control our method to explore high resolution imagery can be applied to characterize the sinkhole deformation and mitigate sinkhole related geohazards

varves in marine sediments a review the global compilation of reported marine varved sedimentary records throughout the quaternary contains 52 sites marine varve deposition and preservation typically depend on environmental and sedimentological conditions such as a sufficiently high sedimentation rate severe depletion of dissolved oxygen in bottom water to exclude bioturbation by macrobenthos and a seasonally varying sedimentary input to yield a recognizable rhythmic varve pattern additional oceanographic factors include the strength and depth range of the oxygen minimum zone omz and regional anthropogenic eutrophication from point sources such as large polluted rivers quaternary marine varves are not only found in those parts of the open ocean that comply with these conditions but also in fjords embayments and estuaries with thermohaline density stratification and nearshore marine lakes with strong hydrologic connections to ocean water this review critically describes settings and sedimentological characteristics of marine sites where varves have been reported broader applications of marine varve records are discussed for example in terms of radiocarbon calibration on high resolution time scales constraining paleoceanographic variability and global change teleconnections diagnosing factors affecting modern fish population dynamics based on past performance detailing biogeochemical cycles and deciphering complex factors influencing marine productivity varves in saline water bodies without hydrologic connection to the global ocean are not included in this review and instead pertain to the companion review on lacustrine varves where also general and fundamental principles of varve deposition classification and dating are covered zolitschka et al 2015 the postulated occurrence of varves in pre quaternary rocks is critically discussed in this review with representative examples in the case of non evaporitic laminations in fine grained ancient marine rocks such as banded iron formations and black shales laminations may not be varves but instead may have multiple alternative origins such as event beds or formation via bottom currents that transport and sort silt sized particles clay floccules and organic mineral aggregates in the form of migrating bedload ripples

a study of erosion rates on salt diapir surfaces in the zagros mountains se iran salt exposures and weathering residuum on several salt diapirs in different geographic climatic settings were studied anhydrite gypsum hematite calcite dolomite quartz and clay minerals are the main constituents of the weathering residuum covering the salt diapirs in various thicknesses erosion rates of residuum as well as of rock salt exposures were measured at selected sites for a period of 5 years by plastic pegs as benchmarks recorded data were standardized to a horizontal surface and to long term mean precipitation for the rock salt exposures the following long term denudation rates were determined of 30 40 mm a 1 for coastal diapirs and up to 120 mm a 1 for mountain salt diapirs long term mean superficial denudation rate measured on weathering residuum of low thickness reached 3 5 mm a 1 on coastal diapirs the total denudation rate estimated for the thin residuum is close to 4 7 mm a 1 based on apparent correlation with the uplift rate on hormoz and namakdan diapirs denudation of rock salt exposures is much faster compared to parts of diapirs covered by weathering residuum the extent of salt exposures is an important factor in the morphological evolution of salt diapirs as it can inhibit further expansion of the diapir salt exposures produce huge amounts of dissolved and clastic load thus affecting the surrounding of the diapir

abrupt aridities and salt deposition in the post glacial dead sea and their north atlantic connection abstract abrupt arid events in the post glacial 17 4 10 kyr bp dead sea basin dsb were recorded by significant lake level declines in lake lisan and massive deposition of gypsum and salt between 17 4 and 16 kyr cal bp the lake level dropped from its late mis2 stand of 260 m below mean sea level m bmsl to 330 m bmsl depositing a thick sequence of gypsum between 16 and 15 kyr cal bp the lake level recovered but dropped abruptly again at 14 kyr cal bp to below 465 m bmsl probably the lowest late pleistocene stand then between 13 and 11 kyr cal bp the younger dryas time interval the lake rose above 400 m bmsl and declined at 11 10 kyr cal bp depositing a thick sequence of salt the abrupt lake level drops and salt deposition coincided with times of ice and meltwater discharges into the north atlantic na heinrich event h1 and meltwater pulse mwp1a similar coincidence between ice and meltwater discharges in the na e g h events and arid episodes at the levant was recorded during the colder last glacial period demonstrating a persistent effect of the north atlantic hydrology and sea ice advances on the levant climate the climatically turmoil post glacial period was accompanied by significant developments in human culture the collapse of the natufian culture during the bolling allerod and the rise of the pre pottery neolithic cultures ppn a and b around the 11 10 kyr cal bp salt deposition interval marking the initiation of the neolithic revolution in the region

radar interferogram filtering for geophysical applications the use of sar interferometry is often impeded by decorrelation from thermal noise temporal change and baseline geometry power spectra of interferograms are typically the sum of a narrow band component combined with broad band noise we describe a new adaptive filtering algorithm that dramatically lowers phase noise improving both measurement accuracy and phase unwrapping while demonstrating graceful degradation in regions of pure noise the performance of the filter is demonstrated with sar data from the ers satellites over the jakobshavns glacier of greenland

dead sea sinkholes an ever developing hazard sinkhole development along the western shore of the dead sea became a major concern in 1990 with the appearance of a series of holes 2 15 m diameter and up to 7 m deep in the newe zohar area one of these sinkholes below the asphalt surface of the main road along the western shore of the dead sea was opened by a passing bus repeated infilling and collapse of these holes indicated the extent of this ongoing process and the significance of this developing hazard since then sinkholes have developed in other areas including qalia ein samar ein gedi and mineral beach

mediterranean flash flood transfer through karstic area karstic aquifers influence flash floods propagation in mediterranean countries near montpellier southern france discharge data are recorded on the coulazou river upstream and downstream of the aumelas causse two gauging stations are used to describe the hydrodynamics of this binary karstic system the first station characterizes the non karstic catchment area the second one is representative of the karstic part of the watershed records since april 2004 are used to understand how the river interacts with a karstic aquifer hydrograph analysis of three flash flood events is described corresponding discharge time series recorded at the two gauging stations are used to describe the modification of the hydrographs by auto and crosscorrelations analyses finally linear system analyses are used to provide the transfer functions of this binary karstic system according to the three flood events characteristics initial conditions volume spatial distribution of rainfall etc theses functions summarize the hydrodynamic behaviour of the system their shapes are indicative of the dynamics of the storage the release and the contribution to surface waters

the impact of hydroclimate and dam construction on terrigenous detrital sediment composition in a 250 year santa barbara basin record off southern california abstract the recurrence and magnitude of southern california hydroclimate extremes are poorly resolved due to the relatively short duration

dynamic dissolution of halite rock during flow of diluted saline solutions 1 the dynamic dissolution pattern of halite salt rocks taken from coreholes near the dead sea was studied in laboratory scale experiments when unsaturated solution with respect to halite flowed through salt cores dissolution developed along preferential flow pathways in a channel structure the channel structure was related to the salt s properties and internal heterogeneities flow velocity and impact of gravity preferential dissolution pathways developed in areas of minimum resistance to flow such as large pore networks and cracks nevertheless in many cases no structural heterogeneity was observed along the dissolution channels prior to the experiments the initial formation of channels took place above a critical flow velocity below this threshold dissolution developed as a slowly propagating front in these cases salt re precipitation resulted in clogging and cessation of flow through a few of the salt cores solution density was found to be important as evidenced by the fact that more channels developed upward than downward due to gravitational fractionation the development of dissolution channels could have very important implications for the overall permeability of the salt layer in general and the use of salt formations for industrial waste storage and the development of sinkholes along the dead sea shore in particular

river response to quaternary subsidence due to evaporite solution gallego river ebro basin spain abstract the stream terrace evolution of the gallego river during the quaternary was controlled by both climatic change and subsidence quaternary terrace deposits overlying tertiary clay and limestone are between 2 and 5 m thick whereas above evaporite formations the alluvial deposits may be as much as 110 m thick chronologically the first period of alluvial thickening involved the stream terraces t2 105 m above the present thalweg t3 95 m and t4 85 m which have been dated by paleomagnetic reversals as matuyama pre 780 000 the second subsidence period affected the deposits of the stream terrace t9 30 dated as brunhes post 780 000 in both thickening periods the subsidence was due to solution of the underlying evaporite formations halite and gypsum presumably during intervals of high water flow in the proposed model the valley subsidence was balanced by stream aggradation maintaining the river equilibrium profile the subsidence recorded in the alluvial deposits shows a complex spatial and temporal evolutionary pattern and total subsidence was assumed to be equal to the alluvial thickening for each subsidence period reaching up to 165 and 25 m respectively

gypsum karstification induced subsidence effects on alluvial systems and derived geohazards calatayud graben iberian range spain abstract the karstification of the tertiary gypsum formations in the calatayud graben has given rise to synsedimentary and postsedimentary subsidence phenomena in both the neogene sediments of the endorheic graben fill and in the quaternary alluvial sediments deposited under exorheic conditions in the so called maluenda and perejiles areas covering 4 4 and 12 km 2 respectively the neogene sedimentary units stratigraphically above the gypsum have subsided due to the karstification of the underlying evaporites the maximum subsidence in both areas has reached at least 200 m the jalon jiloca perejiles alluvial system has been affected by karstic subsidence during its quaternary evolution ten stepped alluvial levels pediment terrace have been identified as a consequence of synsedimentary karstic subsidence the deposit of an alluvial level can be locally thickened changing in a short distance from less than 10 m to more than 100 m in thickness thus the deposit of an individual terrace can be locally superimposed on the deposits of older terraces the palaeokarst recorded in the sediments of the different alluvial levels shows how the karstic subsidence has controlled the dynamics of the sedimentary system the alluvial karstic subsidence is currently active in the flood plains affecting fluvial channels buildings communication ways irrigation ditches and the calatayud gypsum scarp