the flank margin model for dissolution cave development in carbonate platforms the bahama islands contain many abandoned dissolution caves at elevations between two and seven metres above current sea level the development of dissolution caves in tropical carbonate islands is dependent on the position and nature of the freshwater lens lens position is controlled by sea level which in stable carbonate platforms like the bahamas is a function of glacioeustatic sea level still stands caves in the bahamas that are currently subaerial must have developed during past higher sea levels during the late quaternary sea levels higher than present have been relatively short lived and that limits the amount of time that a freshwater lens could be situated at the elevation required for the cave formation the bahama islands are low lying landforms where only aeolian ridges extend to elevations higher than six metres above current sea level past high sea level events greatly reduced the exposed land area of the bahama islands thus also limiting both the catchment for and size of freshwater lenses caves must be younger than the rock in which they are developed most subaerial bahamian caves are found in limestones that are less than 150000 years old development of large dissolution caves under these limitations of time and lens size requires a powerful dissolutional mechanism the mixing of discharging freshwater with tide pulsed incoming marine water under the flanks of emergent dune ridges may have produced the conditions necessary bahamian caves formed by this process are phreatic chambers with complex interconnections and blind tubes their presence demonstrates that significant dissolution can occur rapidly as a result of the mixing of fresh and marine waters beneath small carbonate islands

a sinkhole susceptibility zonation based on paleokarst analysis along a stretch of the madrid barcelona high speed railway built over gypsum and salt bearing evaporites ne spain abstract this paper presents a methodology for producing sinkhole susceptibility zonations along linear infrastructures based on the analysis of the subsidence and dissolution features exposed in the adjacent cuttings and the distribution of karstic depressions the proposed approach have been applied to a 24 km long stretch of the high speed madrid barcelona railway built on halite and glauberite bearing evaporites of the tertiary zaragoza gypsum formation more than 100 km of this railway line have been built over salt bearing tertiary evaporites and trains run at a cruising speed of 300 km h the susceptibility assessment has been restricted to the sections located in karstic depressions 2 98 km and trenches excavated in the ground 13 93 km a low susceptibility has been assigned to the sections built on thickened alluvium of the huerva fluvial system 0 5 km and those in which the evaporites exposed in the cuttings do not show evidence of dissolution or subsidence 3 52 km a total of 4 5 km have received an intermediate susceptibility the cuttings in these sections show sagging structures cavities above the railway roadbed irregular rockhead or shallow alluvium bedrock boundary a high susceptibility has been assigned to a total of 6 59 km these correspond to cavities and collapse structures that reach the railway roadbed 3 61 km and karstic depressions generated by interstratal karstification and subsidence 2 98 km the paleokarst and geomorphic evidence in these sections reveals that cavities either air or sediment filled do exist beneath the railway the distribution of the karst features and susceptibility zones seems to be controlled to a large extent by the lithostratigraphy of the bedrock wedging out of the evaporites to the se and increase in the proportion of halite and glauberite to the nw the proposed zonation could be used as the basis for the selection of the stretches where further investigations and the application of mitigation measures would have a better cost benefit ratio

geomorphology and natural hazards in karst areas a review 1 introductionsince human beings started to colonise the world slowly migrat ing in multiple directions from the african rift and ultimatelyreaching the southernmost territories of the americas they haveinteracted with the natural environment using its resources and suf fering from its hazardous processes survival of mankind was possiblethanks to its ability to adapt to an ever changing environment and itscapability to learn and communicate the new ndings from the ear liest times geomorphic features and processes were an essential partof social survival crozier et al 2011 in karst terrains caves wereused as shelters as well as burial and sacred places playing an instru mental role in the day to day struggle for survival especially duringthe ice ages fig 1 spectacular karst landmarks such as big cave en trances blue karst springs deep collapse sinkholes cenotes or rockarches just to name a few have often become part of the naturaland supernatural heritage of our ancestors in prehistoric times the human impact on the karst environmentwas very limited like the probability of properties and people beingdamaged by karst processes e g subsidence ooding both impactsandhazardsinkarstterrainshaveincreaseddramaticallyover thelasttwo centuries along with the exponential increase in population andour capability to modify the natural environment largely related tothe economic and technological development of the societies an in creasing number of scientists consider that humans are nowadaysthe most effective geomorphic agent and a prime factor in landscapeevolution zalasiewicz et al 2010 price et al 2011 in fact the for mal de nition of the anthropocene as a new epoch of the geologicaltime scale characterised by a signi cant and global human impact onthe earth s ecosystems is being debated at the present time around25 of the earth s population lives on or nearby karst areas ford andwilliams 2007 and the increasing exploitation of karst resources such as water and building material is leading to severe environmen tal impacts and unsustainable situations drew and hotzl 1999 gunn 2004 unfortunately the number of karst areas affected bywater pollution landscape degradation and other impacts is growingveryrapidly additionally thedamagecausedbyhazardouskarstpro cesses especially subsidence sinkholes beck 2003 waltham et al 2005 gutierrez et al 2008a will most likely keep on increasing exposed human elements augment and anthropogenic changes inthe karst systems frequently result in hazard enhancement karstgeomorphologists and hydrologists can play a decisive role in pre venting natural disasters in karst areas particularly those inducedby human activities dams with leakage and sinkhole problems milanovic 2000 cooper and gutierrez 2011 mines and tunnelsaffected by ooding and subsidence li and zhou 1999 autin 2002 casagrandeet al 2005 luchaetal 2008 high speedrailwaysbuilt in sinkhole prone areas guerrero et al 2008 or developmentof sinkholes at huge rates induced by lake level yechieli et al 2006 or water table sprynskyy et al 2009 declines the importance of properly managing karst areas and mitigatingthe detrimental effects caused by human activities on these inherentlysensitive environments has been boosted by a series of conferencesand projects since the early 1990s ford 1993 williams 1993 pariseet al 2008 2009 raising public awareness on the need to protectour endangered natural resources especially in developed countries has promoted the production of karst speci c environmental impactassessments veni 1999 recently severalapproacheshavebeenpro posedtoassessthedegreeofhuman induceddisturbanceinkarstareas van beynen and townsend 2005 calo and parise 2006 de waele 2009 north et al 2009 although these studies are essential for apropermanagementofthekarstresources theymaybefutileifnotfol lowed by adequate administrative decisions and regulations 2 karst geomorphology2 1 karst processeskarst is characterised by the predominance of rock dissolution overmechanical erosion and is typical of present temperate cold andwarm and tropical environments ford and williams 2007 in karstterrains surface and subsurface geomorphology and hydrology arelargely governed by dissolution of carbonate and or evaporite rocks in the most classical common situation surface waters acidi ed byco

do young martian ray craters have ages consistent with the crater count system abstract mcewen et al mcewen a s preblich b s turtle e p artemieva n a golombek m p hurst m kirk r l burr d m christensen p 2005 icarus 176 351 381 developed a useful test for the internal consistency of crater count chronometry systems they argued that certain multi kilometer fresh looking martian craters with prominent rays should be the youngest or near youngest craters in their size range the mcewen et al test is that the ages determined from crater densities of the smallest superimposed craters typically diameter d 5 20 m should thus be comparable to the expected formation intervals of the host primary mcewen et al concluded from moc data that crater chronometry failed this test by factors of 700 2000 we apply hirise and other imagery to eight different young craters in order to re evaluate their arguments we use existing crater chronology systems as well as the reported observed production rate of 16 m craters malin m c edgett k posiolova l mccolley s noe dobrea e 2006 science 314 1573 1557 hartmann w k quantin c mangold n 2007 icarus 186 11 23 kreslavsky 2007 seventh international conference on mars 3325 every case passes the mcewen et al test we conclude that the huge inconsistencies suggested by mcewen et al are spurious many of these craters show evidence of impact into ice rich material and appear to have ice flow features and sublimation pits on their floors as production rate data improve decameter scale craters will provide a valuable way of dating these young martian geological formations and the processes that modify them

solution weathering rate and origin of karst landforms and caves in the quartzite of auyan tepui gran sabana venezuela abstract the paper reports the results of sio 2 analyses in the aonda cave system located on the auyan tepui one of the widest table mountains of the gran sabana south venezuela characterised by karst landforms developed in siliceous rock chemical analyses underline the very low concentration of sio 2 of the surface water percolation and cave drip waters have a sio 2 concentration of about 1 mg l the mean silica load of the cave stream is 184 mg s mainly derived from surface solution removal in the allogenic recharge area in the aonda cave system the mean sio 2 dissolved load is 40 mg s in part from surface solution 15 and mainly from underground processes 85 the low solubility of sio 2 in slightly acidic water implies the importance of the time factor in the formation of cave systems with the present dissolution rate about 10 ma would be necessary to form the known karst system this estimation can be significant only if we assume that climate has been stable in the last few tens of millions of years furthermore this age can be taken as a minimum estimate while according to the geomorphic evolution of the area the origin of the aonda cave system could be reasonably dated back to at least 20 30 ma that is to the oligocene

evolution of isolated caves in porous limestone by mixing of phreatic water and surface water at the water table of unconfined aquifers a model approach summary when water from the surface e g from a lake flows through porous carbonate rocks down along some region with high hydraulic conductivity and encounters the water table of a phreatic aquifer both waters mix by diffusion along their boundary in a carbonate aquifer where both surface and phreatic waters are saturated with respect to calcite mixing corrosion causes renewed dissolution of the carbonate rock in the diffusional mixing zone extending from the boundary separating the phreatic water from the surface water encountering it a numerical model is presented from which the initial change of porosity in such a diffusional mixing zone is obtained the initial change of porosity d dt 0 is proportional to m x y 2 and d2 ceq m dm2 m x y is the spatial distribution of the mixing ratio m vsur vsur vphr and the vs assign the corresponding volumes of surface and phreatic water d2 ceq dm2 is the second derivative of ceq the renewed dissolution capacity of the mixed solution it has been calculated for three geochemical scenarios with differing co2 concentrations of surface and phreatic water by use of phreeqc 2 the spatial distribution m x y is obtained by using modflow and mt3dms in a modeling domain with constant hydraulic conductivity for various flow velocities of the phreatic aquifer from the results the time scale of cave evolution is estimated passages of dimensions of about one meter in width and several 10 cm in height extending in length along the border line where surface and phreatic water meet can be created in time scales of 10 000 years these caves are horizontal with blind ending passages and resemble closely to the isolated caves observed in central west florida for more realistic modeling we have used a geostatistical local distribution of hydraulic conductivities in the modeling domain for a correlation length of 1 of the length of modeling domain the spatial distribution extends deeper into the flow direction when the correlation length is increased by a factor of 10 flow focusing distorts the diffusional mixing zone and enhances the creation of porosity

human induced geological hazards along the dead sea coast the dead sea is a terminal lake whose level is currently dropping at a rate of about 1 m per year due to the over exploitation of all its tributaries the lowering started about four decades ago but geological hazards appeared more and more frequently from the end of the 1980s the water level lowering is matched by a parallel groundwater level drop which results in an increasing intensity of underground and surface water flow the diagonal interface between the dead sea brine and the fresh groundwater is pushed downwards and seawards nowadays sinkholes subsidence landslides and reactivated salt karsts affect wide coastal segments until now mainly infrastructures were damaged and few people animals were injured but the ongoing development of tourism in this very attractive situation will increase the risk if precautionary measures are not included in the development plans this paper discusses the main observations made all around the dead sea and shed a light on the differences between the geological hazards of the western shore israel palestinian authority and the eastern shore jordan it is the first attempt to bring together an overview of the human induced geological hazards encountered along the dead sea coast

a geomorphological strategy for conducting environmental impact assessments in karst areas in their efforts to protect regional groundwater supplies governmental agencies are increasingly requiring studies of karst areas and their features in areas where tracer tests or geophysics are not required funded or otherwise feasible geomorphological methods remain as the primary tool for assessing karst this study proposes a geomorphologically based environmental impact assessment strategy for karst areas while it is supported with results from a study of the karstic edwards aquifer recharge zone on the camp bullis military training installation tx usa it is based on the study of several karst areas and is generalized to accommodate and be fine tuned for regional variations biological and other resource issues can also be assessed with this strategy the assessment identifies environmentally sensitive features and areas as is often required to meet regulatory directives in karst areas with relatively small features excavation is a key tool for accurate assessment although the results of this study will help to better manage karst areas proper management must be done on a regional scale the highly permeable nature of karst precludes adequate management solely on a feature by feature basis studies on the relationship of water quality to impervious cover show adverse environmental impacts significantly increase when impervious cover exceeds 15 of a surface watershed the camp bullis study finds similar impacts in its groundwater drainage basin supporting the argument of 15 impervious cover as a regionally effective means of also protecting karst aquifers when coupled with protection of critical areas identified by field surveys

current perspectives on the environmental impacts and hazards in karst karst geo ecosystems are highly fragile environments that are suffering a progressive degradation caused by human activities in many regions of our planet the interactions between man and karst environments have been relevant since greek and roman times nicod et al 1997 but the resulting detrimental effects became particularly significant from the industrial revolution despite the long history of human induced impacts on the karst environments and damage caused by hazardous karst processes these problems were largely overlooked by the scientific community till the beginning of the 90s fortunately both the perception of the importance of the karst systems and the scientific efforts devoted to their understanding have increased considerably in recent times ford and williams 2007 the results of some investigations have been published in several special issues catena supplement environmental geology oklahoma geological survey circular geological society of london special publication engineering geology williams et al 1993 burri et al 1999 johnson and neal 2003 parise and gunn 2007 gutierrez et al 2008c parise et al 2008 and conference proceedings sauro et al 1991 beck 2003 subsidence related to sinkhole activity is the most important hazard in karst landscapes beck 2003 waltham et al 2005 in many regions financial losses caused by sinkholes are raising considerably due to the humaninduced increase in the probability of occurrence of sinkholes and the development of hazardous areas gutierrez et al 2008a some approaches including mechanical hydrogeological and predictive modelling salvati and sasowsky 2002 he et al 2004 geophysical surveys ardau et al 2007 speleological studies klimchouk et al 2002 and palaeokarst investigations gutierrez et al 2008b have provided enlightening insights on the processes involved in the subsidence phenomena other typical environmental problems in karst terrains are related to water quality and quantity drew and hotzl 1999 goldscheider and drew 2007 ravbar 2007 construction of infrastructures dams highways tunnels milanovic 2002 mining and quarrying gunn 2004 and other human activities such as agriculture waste disposal or urbanisation this special issue of environmental geology contains a selection of peer reviewed articles presented at the symposium on natural and anthropogenic hazards in karst areas held in vienna austria on 16 april 2007 within the framework of the natural hazards programme of the european geosciences union general assembly the symposium was co sponsored by the international union of speleology uis and by the international geographical union igu commission of karst hydrogeology and speleogenesis out of the 35 contributors to the session 22 accepted the invitation to submit a full paper and finally 15 peerreviewed articles have been accepted and included in this special issue they cover many different geographical areas where the interaction between karst systems and human activities results in significant environmental impacts and hazards europe austria bosnia m parise national research council irpi bari italy e mail m parise ba irpi cnr it

a global review of solutional weathering forms on quartz sandstones abstract solutional landforms in limestone have been described for over a hundred years but landforms of similar morphology on highly siliceous sandstones and quartzites have also been identified in a wide variety of environments and generally termed pseudokarst these include large bedrock pinnacles and towers caves corridors grikes solution basins and runnels and even silica speleothems quartzites and quartz sandstones have been held to be amongst the most chemically resistant of rocks but the similarity both in morphology and genetic process of many landforms developed from them to features of known solutional origin on limestone has prompted some authors to refer to these quartzose landforms as true karst the most detailed studies of quartzose karst landforms have been in present day tropical regions or areas believed to have been tropical in the geologically recent past this concentration of research in hot wet areas allied with the long held assertion of the insolubility of silica especially quartz has led to a belief that tropical climatic conditions are necessary for karstic solution of these rocks however the existence of quartzose karst landforms in temperate and even sub polar latitudes especially where there is no evidence of prior tropical conditions suggests that the requirement of tropical weathering is no longer tenable the reports of these quartzose solutional landforms are widely scattered through the geomorphological and geological literature but a comprehensive world wide review of the range of solutional landforms on quartzose rocks has not previously been published because of the increasing awareness in this karst type such a summary is sorely overdue

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 scaling law to characterize fault damage zones at reservoir depths we analyze fracture density variations in subsurface fault damage zones in two distinct geologic environments adjacent to faults in the granitic ssc reservoir and adjacent to faults in arkosic sandstones near the san andreas fault in central california these damage zones are similar in terms of width peak fracture or fault ff density and the rate of ff density decay with distance from the main fault seismic images from the ssc reservoir exhibit a large basement master fault associated with 27 seismically resolvable second order faults a maximum of 5 to 6 ff m 1 5 to 1 8 ff ft are observed in the 50 to 80 m 164 to 262 ft wide damage zones associated with second order faults that are identified in image logs from four wells damage zones associated with second order faults immediately southwest of the san andreas fault are also interpreted using image logs from the san andreas fault observatory at depth safod borehole these damage zones are also 50 80 m wide 164 to 262 ft with peak ff density of 2 5 to 6 ff m 0 8 to 1 8 ff ft the ff density in damage zones observed in both the study areas is found to decay with distance according to a power law the fault constant is the ff density at unit distance from the fault which is about 10 30 ff m 3 1 9 1 ff ft in the ssc reservoir and 6 17 ff m 1 8 5 2 ff ft in the arkose the decay rate ranges from 0 68 to 1 06 in the ssc reservoir and from 0 4 to 0 75 in the arkosic section this quantification of damage zone attributes can facilitate the incorporation of the geometry and properties of damage zones in reservoir flow simulation models

interaction between a dam site and karst springs the case of supramonte central east sardinia italy abstract sardinia is one of the italian regions with the greatest number of dams per inhabitants almost 60 for a population of only 1 5 million people many of these dam sites are located on non carbonate rocks along the main rivers of the island and their waters are used for irrigation industrial energy supply drinking and flood regulation purposes the pedra e othoni dam on the cedrino river dorgali central east sardinia is located along the threshold of the palaeozoic basement on the northern border of the supramonte karst area where water is forced to flow out of the system through several resurgences the most famous of which is the su gologone vauclusian spring used for drinking water supply the other main outflows of the system su tippari and san pantaleo springs are at present almost permanently submerged by the high water level of the pedra e othoni dam in the near future water will be supplied also to other communities with a possible increase of water taken from the spring the dam originally meant to regulate the flooding of cedrino river but actually used for all sorts of purposes electricity supply drinking water irrigation of farmlands industrial uses has a maximum regulation altitude of 103 m a s l only slightly less than a meter below the su gologone spring level 103 7 m and 4 and 9 m respectively above the submerged su tippari and san pantaleo springs during floods of the cedrino river occurring on average twice a year also the su gologone spring becomes submerged by the muddy waters of the lake for a time ranging between a couple of hours up to several days making water supply impossible the analysis of the available meteorological and hydrogeological data relative to the december 2004 flood one of the severest of the past 100 years suggests that the reservoir is filled in a few days time several flooding scenarios have been reconstructed using digital terrain models showing that backflooding submerges most of the discharge area of the aquifer having important repercussions also on the inland underground drainage system the upstream flood prone areas prevalently comprise agricultural lands with some sparse houses but also highly frequented tourist facilities fortunately flooding occurs outside the tourist season thus limiting risk to a limited number of local inhabitants massive discharge at the dam site instead determines a more hazardous situation in the cedrino coastal plain where population density in low lying areas is much higher to avoid flooding hazard upstream the water level in the lake should be regulated keeping it low in the flood prone seasons and having it filled from the end of the winter in order to have enough water stocked before the beginning of the summer discharge at the dam site instead should be done cautiously preventing severe flooding of the coastal cedrino plain

morphology and origin of coastal karst landforms in miocene and quaternary carbonate rocks along the central western coast of sardinia italy in the area of punta funtanas arbus central west sardinia some small surfaces of miocene limestones crop out partially covered with quaternary calcarenites and plio quaternary basalts the biggest of these outcrops forms a fossil wave cut shore platform of up to 50 m wide with an altitude above sea level of approximately 4 5 m on this platform a wide variety of dissolution landforms can be observed these morphologies are related to the influence of the seawater zone of wave action marine splash and spray zone up to progressively more continental environments and to biokarst processes erosional action of marine organisms algae and micro organisms and are arranged in bands parallel to the coast corresponding to different morphological zones this paper describes all the karst landforms observed in this coastal area from a morphological and genetic point of view

natural and human induced dissolution and subsidence processes in the salt outcrop of the cardona diapir ne spain the cardona diapir in ne spain with a salt outcrop about 0 9 km2 in area has a well developed endokarstic system that used to discharge into the cardener river underground mining for potassium salt carried out from 1930 to 1990 caused significant changes in the topography and hydrology of the diapir the accumulation of two halite slag heaps totalling around 10 million tons locally dammed the surface drainage creating closed depressions and preferential zones of water recharge the waters that infiltrated in one of these depressions largely derived from uncontrolled sewage disposal led to the generation of a 335 m long human induced cave excavated in one of the slag heaps moreover the inflow of freshwater from the surrounding sandstone aquifer caused by the excavation of a ventilation gallery resulted in the generation of a 280 m long cave in march 1998 the interception of a phreatic conduit by a halite mine gallery 50 m deep caused dramatic changes in the hydrology and geomorphology of the diapir including a a sudden decline in the piezometric level of the karstic aquifer b the inflow of freshwater and debris from the cardener river into the endokarstic system and the mine galleries a tunnel had to be constructed to divert the river flow from the salt outcrop c massive dissolution of salt creating new cavities and enlarging the pre existing ones including both mine galleries or cave passages the 4 300 m long salt meanders cave was largely generated by the inrush of water from the cardener river into the mine galleries and d the generation of a large number of sinkholes in the vicinity of the cardener river an inventory of 178 sinkholes has allowed us to estimate minimum probability values of 4 7 and 8 sinkholes km2 year for time intervals previous and subsequent to the 1998 mine flood event respectively

mobile sediment in an urbanizing karst aquifer implications for contaminant transport here we investigate geochemical characteristics of sediment in different compartments of a karst aquifer and demonstrate that mobile sediments in a karst aquifer can exhibit a wide range of properties affecting their contaminant transport potential sediment samples were collected from surface streams sinkholes caves wells and springs of a karst aquifer the barton springs portion of the edwards balcones fault zone aquifer central texas and their mineralogy grain size distribution organic carbon content and specific surface area analyzed statistical analysis of the sediments separated the sampling sites into three distinct groups 1 streambeds sinkholes and small springs 2 wells and 3 caves sediments from the primary discharge spring were a mix of these three groups high organic carbon content and high specific surface area gives some sediments an increased potential to transport contaminants the volume of these sediments is likely to increase with continued urbanization of the watershed

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

identification prediction and mitigation of sinkhole hazards in evaporite karst areas sinkholes usually have a higher probability of occurrence and a greater genetic diversity in evaporite terrains than in carbonate karst areas this is because evaporites have a higher solubility and commonly a lower mechanical strength subsidence damage resulting from evaporite dissolution generates substantial losses throughout the world but the causes are only well understood in a few areas to deal with these hazards a phased approach is needed for sinkhole identification investigation prediction and mitigation identification techniques include field surveys and geomorphological mapping combined with accounts from local people and historical sources detailed sinkhole maps can be constructed from sequential historical maps recent topographical maps and digital elevation models dems complemented with building damage surveying remote sensing and high resolution geodetic surveys on a more detailed level information from exposed paleosubsidence features paleokarst speleological explorations geophysical investigations trenching dating techniques and boreholes may help in investigating dissolution and subsidence features information on the hydrogeological pathways including caves springs and swallow holes are particularly important especially when corroborated by tracer tests these diverse data sources make a valuable database the karst inventory from this dataset sinkhole susceptibility zonations relative probability may be produced based on the spatial distribution of the features and good knowledge of the local geology sinkhole distribution can be investigated by spatial distribution analysis techniques including studies of preferential elongation alignment and nearest neighbor analysis more objective susceptibility models may be obtained by analyzing the statistical relationships between the known sinkholes and the conditioning factors chronological information on sinkhole formation is required to estimate the probability of occurrence of sinkholes number of sinkholes km2 year such spatial and temporal predictions frequently derived from limited records and based on the assumption that past sinkhole activity may be extrapolated to the future are non corroborated hypotheses validation methods allow us to assess the predictive capability of the susceptibility maps and to transform them into probability maps avoiding the most hazardous areas by preventive planning is the safest strategy for development in sinkhole prone areas corrective measures could be applied to reduce the dissolution activity and subsidence processes a more practical solution for safe development is to reduce the vulnerability of the structures by using subsidence proof designs

morphogenesis of hypogenic caves abstract hypogenic speleogenesis is the formation of solution enlarged permeability structures by waters ascending to a cave forming zone from below in leaky confined conditions where deeper groundwaters in regional or intermediate flow systems interact with shallower and more local groundwater flow systems this is in contrast to more familiar epigenic speleogenesis which is dominated by shallow groundwater systems receiving recharge from the overlying or immediately adjacent surface hypogenic caves are identified in various geological and tectonic settings formed by different dissolutional mechanisms operating in various lithologies despite these variations resultant caves demonstrate a remarkable similarity in patterns and meso morphology which strongly suggests that the hydrogeologic settings were broadly identical in their formation hypogenic caves commonly demonstrate a characteristic suite of cave morphologies resulting from rising flow across the cave forming zone with distinct buoyancy dissolution components in addition to hydrogeological criteria hydrostratigraphic position recharge discharge configuration and flow pattern viewed from the perspective of the evolution of a regional groundwater flow system morphogenetic analysis is the primary tool in identifying hypogenic caves cave patterns resulting from ascending transverse speleogenesis are strongly guided by the permeability structure in a cave formation they are also influenced by the discordance of permeability structure in the adjacent beds and by the overall hydrostratigraphic arrangement three dimensional mazes with multiple storeys or complex 3 d cave systems are most common although single isolated chambers passages or crude clusters of a few intersecting passages may occur where fracturing is scarce and laterally discontinuous large rising shafts and collapse sinkholes over large voids associated with deep hydrothermal systems are also known hypogenic caves include many of the largest by integrated length and by volume documented caves in the world more importantly hypogenic speleogenesis is much more widespread than it was previously presumed growing recognition of hypogenic speleogenesis and improved understanding of its peculiar characteristics has an immense importance to both karst science and applied fields as it promises to answer many questions about karst porosity especially as deep seated settings are concerned which remained poorly addressed within the traditional epigenetic karst paradigm

sinkhole distribution in a rapidly developing urban environment hillsborough county tampa bay area florida sinkhole formation in florida is a common event the florida karst plain is significantly altered by human development and sinkholes cause considerable property damage throughout much of the state we present in this paper a morphometric analysis of karst depressions in the tampa bay area and the relation with the known distribution of sinkholes we selected the tampa bay area because it is particularly susceptible to the evolution of karst depressions in relation with development of the built up environment karst depressions were mapped from the 1 24 000 usgs topographic maps and a morphometric analysis was performed by using parameters such as shape circularity index perimeter area length width and orientation maps showing the distribution of depression density and the sectors with greatest areas of karst depression were produced using a gis these results were compared with data compiled from the database of sinkhole occurrences in florida maintained by the florida geological survey our analysis demonstrates that the distribution of new sinkhole occurrences differs from the distribution of existing sinkholes indicating that there are processes acting today that are influencing karst landscape formation that are different from those acting in the past

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

holocene glacier history from alpine speleothems milchbach cave switzerland abstract mountain glaciers and their sediments are prominent witnesses of climate change responding sensitively to even small modifications in meteorological parameters even in such a classical and thoroughly studied area as the european alps the record of holocene glacier mass balance is only incompletely known here we explore a novel and continuous archive of glacier fluctuations in a cave system adjacent to the upper grindelwald glacier in the swiss alps milchbach cave became partly ice free only recently and hosts holocene speleothems four coeval stalagmites show consistent petrographic and stable isotopic changes between 9 2 and 2 0 ka which can be tied to abrupt modifications in the cave environment as a result of the closing and opening of multiple cave entrances by the waxing and waning of the nearby glacier during periods of holocene glacier advances columnar calcite fabric is characterized by 18 o values of about 8 0 indicative of speleothem growth under quasi equilibrium conditions i e little affected by kinetic effect related to forced degassing or biological processes in contrast fabrics formed during periods of glacier minima are typical of bacterially mediated calcite precipitation within caves overlain by an alpine soil cover moreover 18 o values of the bacterially mediated calcite fabrics are consistent with a ventilated cave system fostering kinetic fractionation these data suggest that glacier retreats occurred repeatedly before 5 8 ka and that the amplitudes of glacier retreats became substantially smaller afterwards our reconstruction of the upper grindelwald glacier fluctuations agrees well with paleoglaciological studies from other sites in the alps and provides a higher temporal resolution compared to traditional analyses of peat and wood remains found in glacier forefields

palaeo climate reconstruction from stable isotope variations in speleothems a review abstract speleothems are now regarded as valuable archives of climatic conditions on the continents offering a number of advantages relative to other continental climate proxy recorders such as lake sediments and peat cores they are ideal materials for precise u series dating yielding ages in calendar years thereby circumventing the radiocarbon calibration problems associated with most other continental records stable isotope studies in speleothems have shifted away from attempting to provide palaeo temperature reconstructions to the attainable goal of providing precise estimates for the timing and duration of major o isotope defined climatic events characterised by high signal to noise ratios e g glacial interglacial transitions dansgaard oeschger oscillations the 8200 year event unlike the marine records speleothem data sets are not tuned and their independent chronology offers opportunities to critically assess leads and lags in the climate system that in turn can provide important insights into forcing and feedback mechanisms improved procedures for the extraction and measurement of stable isotope ratios in fluid inclusions trapped in speleothems are likely to provide in the near future a much enhanced basis for the quantitative interpretation of o isotope ratios in speleothem calcite the latter developments open up once again the tantalising prospect of palaeo temperature estimates but more importantly perhaps provide a direct test for a new generation of general circulation models whose hydrological cycles will incorporate the water isotopes the literature is reviewed briefly to provide for the reader a sense of the current state of the art and to provide some pointers for future research directions

karst flash flooding in a mediterranean karst the example of fontaine de nimes karst flash flooding identified as one of the hazards in karst terrains is directly linked to the structure and hydraulic properties of karst aquifers due to the characteristics of flow within karst aquifers characterized by a dual flow diffuse flow within fissured limestone and conduit flow within karst conduits networks flash flooding may be important in volume and dynamics such phenomenon may cause serious damages including loss of lives as it occurred on 3rd october 1988 in nimes gard south france flash floods there have been considered to be the result of very intensive rainfall events conjugated to runoff due to the geomorphologic context of the city located down hill however preliminary results of recent studies of the hydrologic behaviour of groundwater and surface water for a specific event september 2005 based on an extensive monitoring of the karst aquifer coupled to a classical runoff monitoring show that the role of the karst in the flood genesis plays an important role the main characteristics of the nimes karst system leading to karst flash flooding are presented in this paper a methodology comprising modelling of the karst system allowed proposing simple thresholds for various part of the karst water level threshold for the karst conduits and cumulative rainfall threshold for the overflowing fissured karst these thresholds can be included in the flash flood warning system of the nimes city

sinkholes in the salt bearing evaporite karst of the ebro river valley upstream of zaragoza city ne spain geomorphological mapping and analysis as a basis for risk management abstract a detailed sinkhole map has been produced in a stretch of the ebro valley 40 8 km2 including the western sector of zaragoza city ne spain during the last few decades around 70 of the original sinkhole area has been filled with anthropogenic sediments causing the disappearance of 137 ha of wetlands the interstratal karstification of salts halite and glauberite and a wnw ese trending joint set have played a major control in the development of sinkholes three morphometric types of sinkholes have been differentiated each attributed to a specific subsidence mechanism inferred from the paleosinkholes exposed in the surrounding of zaragoza city sagging of bedrock and cover collapse of bedrock and cover and collapse of cover material related to the downward migration of particles through dissolutional conduits each type of sinkhole is characterised by a distinctive behaviour in terms of controlling factors spatio temporal distribution and kinematics and consequently the proposed differentiation may have a practical utility the vast majority of the subsidence damage identified in the area occurs within the boundaries of pre existing sinkholes identifiable in old aerial photographs and topographical maps this fact demonstrates that the application of preventive planning strategies based on detailed geomorphological maps would have allowed avoidance of most of the large financial losses caused by subsidence in the area of the order of hundreds of thousands of euros per year

travertines depositional morphology and the bacterially constructed constituents abstract investigation of travertine accumulations throughout central italy and the west central u s has shown that the carbonate is precipitated in response to both inorganic and organic processes individual deposits range up to 85 m thick and hundreds of square kilometers in areal extent all of the carbonate is low magnesian calcite water chemistry temperature and morphology of the accumulation greatly influence the constituents comprising these deposits harsh environmental situations favor inorganic deposits while increasingly more moderate conditions result in the formation of a greater abundance of organically precipitated material morphological variations of travertine deposits recognized include 1 waterfall or cascade 2 lake fill 3 sloping mound fan or cone 4 terraced ound and 5 fissure ridge gross morphology internal stratification and constituents comprising these deposits vary systematically depending upon the type of accumulation and chemistry of the waters bacterially precipitated calcite forms a large percentage of the carbonate in many travertine accumulations exceeding 90 of the framework grains comprising some of the lake fill deposits bacteria are among the first taxa to inhabit and reproduce in harsh spring environments and produce a variety of fascinating constituents the bacteria are primarily rods generally 0 2 m in diameter and less than 1 0 m in length the rods readily decay resulting in calcite crystals loaded with micropores the basic building block of bacterially constructed travertine is a clump of bacteria averaging 20 m in diameter enclosed in a single crystal of calcite aggregates of these crystals produce a variety of deposits including 1 crudely laminated carbonate mud 2 finely laminat d layers of mud 3 intraclasts 4 foam rock and 5 shrubs the shrubs are most striking commonly forming layers 1 3 cm thick but also producing bacterial pisoids at some locales bacterial stromatolites composed of layers of shrubs alternating with finely laminated layers of bacterial mud comprise essentially the entire deposit the shrub layers are the result of flourishing summer growth of bacteria and furthermore show remarkable daily laminae 0 1 0 5 mm thick the importance of bacteria in the formation of travertine and their universally recognized abundance in modern sediments provides an impetus for a reexamination of the role of bacteria in the origin of other types of ancient deposits

dinsar measurements of ground deformation by sinkholes mining subsidence and landslides ebro river spain differential interferometric synthetic aperture radar dinsar has been applied to detect and measure ground deformation in a stretch of the ebro river valley spain excavated in salt bearing evaporites the capability of the small baseline subset sbas dinsar technique to detect ground displacement is analyzed comparing the dinsar results with the available geomorphological information the deformation map derived from 27 european remote sensing ers satellite images covering more than five years provides sub centimeter displacement measurements in zones coinciding with known active sinkholes and landslides moreover the map provides the first account of mining subsidence in the area the measured deformation rates reach 1 68 cm y for the sinkholes 0 80 cm y for the landslides and 1 45 cm y for the area affected by mining subsidence the sbas dinsar technique provided deformation measurements in a small proportion 5 10 of the known active sinkholes and landslides this limitation is mainly due to the lack of coherence in agricultural areas the spatial resolution of the deformation map pixel size of 90 m and the parallelism between the ers satellite line of sight and the linear escarpment on which most of the landslides occur despite this the interferometric technique provides valuable data that complement traditional geomorphological studies including the quantification of the deformation phenomena the identification of mining subsidence otherwise only recognizable by geodetic methods and the detection of creep deformation which might correspond to premonitory indicators of catastrophic sinkholes and landslides capable of causing the loss of lives detailed dinsar studies combined with field data would be required to improve the analysis of each deformation area copyright 2009 john wiley sons ltd

on the formation of dissolution pipes in quaternary coastal calcareous arenites in mediterranean settings a large number of uniform cone shaped dissolution pipes has been observed and studied in quaternary coastal calcareous arenites in apulia and sardinia italy and tunisia these cylindrical tubes have a mean diameter of 52 8 cm and are up to 970 cm deep mean depth for sediment free pipes is 1 38 m they generally have smooth walls along their length are perfectly vertical and taper out towards their bottoms their development is not influenced by bedding nor fractures sometimes their walls are coated by a calcrete crust their morphology has been studied in detail and their relationships with the surrounding rocks and with the environment have been analysed the perfectly vertical development is a clear evidence of their genesis controlled by gravity the depth of the dissolution pipes can be described by an exponential distribution law the milanovic distribution strongly suggesting they developed by a diffusion mechanism from the surface vertically downward we believe dissolution pipes preferentially form in a covered karst setting local patches of soil and vegetation cause infiltration water to be enriched in carbon dioxide enhancing dissolution of carbonate cement and local small scale subsidence this process causes the formation of a depression cone that guides infiltrating waters towards these spots giving rise to the downward growth of gravity controlled dissolution pipes a change of climate from wetter phases to drier and hotter ones causes the formation of a calcrete lining fossilizing the pipes when the pipes become exposed to surface agents by erosion of the sediment cover or are laterally breached the loose quartz sand filling them may be transported elsewhere copyright 2010 john wiley sons ltd

the effect of river dynamics induced by the messinian salinity crisis on karst landscape and caves example of the lower ardeche river mid rhone valley abstract the karstic canyon of lower ardeche is located in the middle rhone valley which is directly tributary to the mediterranean sea the rhone river is emblematic of the messinian salinity crisis msc impact on landscape morphology along the edge of the saint remeze plateau the rhone valley displays four benchmark levels generated by the msc the pre evaporitic abandonment surface 1 the messinian erosional surface 2 the marine non marine surface of the pliocene ria 3 and the pliocene abandonment surface 4 the study of these benchmark levels allows us to reconstruct the evolution of the regional base level over the last 6 ma we obtain a curve for base level evolution that provides a geodynamic reference which is used to investigate the morphogenesis of the saint remeze karstic plateau the ardeche river downcuts the saint remeze plateau in a deep canyon from vallon pont d arc to the west to its confluence with the rhone to the east several abandoned valleys are present along the western edge of the saint remeze plateau at the inlet of the ardeche canyon in these abandoned valleys the fluvial deposits are related to several periods from the pliocene onwards they provide important insights into the fluvial dynamics a 160 m thick aggradation sequence infilled the ardeche canyon during the pliocene this aggrading river caused the first lateral shifting as an aggradation epigenesis this first infilling shows that the ardeche canyon already existed before the pliocene secondly it has been demonstrated that the ardeche canyon is downcut into the pre evaporitic surface of the saint remeze plateau dated to 5 45 ma martini j 2005 etude des paleokarsts des environs de saint remeze ardeche france mise en evidence d une riviere souterraine fossilisee durant la crise de salinite messinienne karstologia 45 46 1 18 consequently the canyon downcutting is entirely due to the msc and occurred during a time span of only 100 000 years based on these observations it is possible to elucidate the curve of the regional base level evolution hence we are able to propose a new interpretation of the geomorphological evolution of the saint remeze karstic plateau and its cave levels for the last 6 ma the cave levels consist in underground short cuts of the surface meanders they mainly developed during the pliocene aggradation cycle the chauvet cave famous for its palaeolithic paintings corresponds to one of these underground short cuts the aggradation period ends at the end of the pliocene with long high level riverbed stability it favours the development of large low gradient surfaces as pediments the complete messinian pliocene eustatic cycle is responsible for the downcutting of the ardeche canyon and its infilling during the pliocene consequently karst developed according to the base level oscillations as low gradient surfaces and as cave levels for the study of the peri mediterranean caves and karst areas we propose to apply the lower ardeche valley evolution model based on the base level oscillations during and after the msc

pliocene pleistocene incision of the green river kentucky determined from radioactive decay of cosmogenic 26al and 10be in mammoth cave sediments cosmogenic 26al and 10be in sediments washed into mammoth cave kentucky record the history of 3 5 m y of water table position governed by incision and aggradation of the green river a tributary of the ohio river upper levels of the cave formed during a period of slow river incision and were later filled with sediment due to river aggradation at 2 3 2 4 ma a brief surge of river incision ca 2 ma was followed by river stability and cave passage formation at a lower level rapid incision through 15 m of bedrock ca 1 5 ma was prompted by repositioning of the ohio river to its present course along an ice sheet margin renewed incision ca 1 2 ma and aggradation at 0 7 0 8 ma correlate with major ice advances in the ohio river basin measurements of 26al and 10be also indicate that sandstone capped uplands have maintained slow erosion rates of 2 7 m m y for the past 3 5 m y despite accelerated pleistocene river incision rates of 30 m m y