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Speleology in Kazakhstan

Shakalov on 04 Jul, 2018
Hello everyone!   I pleased to invite you to the official site of Central Asian Karstic-Speleological commission ("Kaspeko")   There, we regularly publish reports about our expeditions, articles and reports on speleotopics, lecture course for instructors, photos etc. ...

New publications on hypogene speleogenesis

Klimchouk on 26 Mar, 2012
Dear Colleagues, This is to draw your attention to several recent publications added to KarstBase, relevant to hypogenic karst/speleogenesis: Corrosion of limestone tablets in sulfidic ground-water: measurements and speleogenetic implications Galdenzi,

The deepest terrestrial animal

Klimchouk on 23 Feb, 2012
A recent publication of Spanish researchers describes the biology of Krubera Cave, including the deepest terrestrial animal ever found: Jordana, Rafael; Baquero, Enrique; Reboleira, Sofía and Sendra, Alberto. ...

Caves - landscapes without light

akop on 05 Feb, 2012
Exhibition dedicated to caves is taking place in the Vienna Natural History Museum   The exhibition at the Natural History Museum presents the surprising variety of caves and cave formations such as stalactites and various crystals. ...

Did you know?

That desorption is the reverse process of sorption [22]. see also sorption.?

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Featured articles from Cave & Karst Science Journals
Chemistry and Karst, White, William B.
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Featured articles from other Geoscience Journals
Karst environment, Culver D.C.
Mushroom Speleothems: Stromatolites That Formed in the Absence of Phototrophs, Bontognali, Tomaso R.R.; D’Angeli Ilenia M.; Tisato, Nicola; Vasconcelos, Crisogono; Bernasconi, Stefano M.; Gonzales, Esteban R. G.; De Waele, Jo
Calculating flux to predict future cave radon concentrations, Rowberry, Matt; Marti, Xavi; Frontera, Carlos; Van De Wiel, Marco; Briestensky, Milos
Microbial mediation of complex subterranean mineral structures, Tirato, Nicola; Torriano, Stefano F.F;, Monteux, Sylvain; Sauro, Francesco; De Waele, Jo; Lavagna, Maria Luisa; D’Angeli, Ilenia Maria; Chailloux, Daniel; Renda, Michel; Eglinton, Timothy I.; Bontognali, Tomaso Renzo Rezio
Evidence of a plate-wide tectonic pressure pulse provided by extensometric monitoring in the Balkan Mountains (Bulgaria), Briestensky, Milos; Rowberry, Matt; Stemberk, Josef; Stefanov, Petar; Vozar, Jozef; Sebela, Stanka; Petro, Lubomir; Bella, Pavel; Gaal, Ludovit; Ormukov, Cholponbek;
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Your search for increment (Keyword) returned 14 results for the whole karstbase:
Assessing the importance of conduit geometry and physical parameters in karst systems using the storm water management model (SWMM), , Peterson Eric W. , Wicks Carol M. ,
SummaryQuestions about the importance of conduit geometry and about the values of hydraulic parameters in controlling ground-water flow and solute transport through karstic aquifers have remained largely speculative. One goal of this project was to assess the role that the conduit geometry and the hydraulic parameters have on controlling transport dynamics within karstic aquifers. The storm water management model (SWMM) was applied to the Devil's Icebox-Connor's Cave System in central Missouri, USA. Simulations with incremental changes to conduit geometry or hydraulic parameters were performed with the output compared to a calibrated baseline model. Ten percent changes in the length or width of a conduit produced statistically significant different fluid flow responses. The model exhibited minimal sensitivity to slope and infiltration rates; however, slight changes in Manning's roughness coefficient can highly alter the simulated output.Traditionally, the difference in flow dynamics between karstified aquifers and porous media aquifers has led to the idea that modeling of karst aquifers is more difficult and less precise than modeling of porous media aquifers. When evaluated against models for porous media aquifers, SWMM produced results that were as accurate (10% error compared to basecase). In addition, SWMM has the advantage of providing data about local flow. While SWMM may be an appropriate modeling technique for some karstic aquifers, SWMM should not be viewed as a universal solution to modeling karst systems

Marine carbonate cements, which are superficially like travertines from meteoric caves, are coating and binding some intertidal sedimentary rock surfaces occurring in coastal Abu Dhabi, the United Arab Emirates, (UAE). Near Jebel Dhana these surficial cements can be up to 3 cm thick and envelope beach rock surfaces and fossils. They are also present both as thin coats and a fracture-fill cement in the intertidal hard grounds associated with the Khor Al Bazam algal flats. The thickness, microscopic characteristics, and morphology of the marine cement coatings from Jebel Dhana indicates incremental deposition of aragonite in conjunction with traces of sulfate minerals. Most of these cement coatings are micritic, but the layers which encrust the hard grounds from the algae flat of the Khor al Bazam have a more radial and fibrous micro-structure and are composed solely of aragonite. The stable isotopic composition of coatings from Jebel Dhana (delta(18)O = .35, delta(13)C = .00) falls within the compositional range for modem marine non skeletal aragonite and suggests that the marine travertine-like cements precipitate from the agitated slightly hypersaline Arabian Gulf sea water during repeated cycles of exposure, evaporation and immersion. Similar cement coatings and microfabrics are present in the tepee structured and brecciated sediments of the Guadalupe Mountains (Permian) and the Italian Alps (Triassic), in Holocene algal head cements from the Great Salt Lace, and in similar Tertiary algal heads in the Green River Formation of the western US. The petrographic similarity of these ancient ''flow stone'' like cements with Recent hypersaline marine cement coatings suggests that high rates of carbonate cementation and hypersaline conditions contribute to tepee formation and cavity fill

Leaching of agricultural chemicals from the root and vadose zones into groundwater is an important environmental concern. To procure a better understanding of the movement and transport of agricultural chemicals through the soil profile, a field research study was conducted to estimate bromide leaching losses under saturated conditions where preferential flow is occurring. The field data were then used to evaluate the LEACHM model. Eighteen double-ring infiltrometers were used to apply a pulse (100 mm depth) of bromide tracer on two previously saturated soils located in a karst region of southeastern Pennsylvania. Internal drainage over the next seven days resulted in nearly 51 % of the applied Br- being leached to a depth below 0.80 m. The LEACHM model was used to simulate the amount of bromide leached in each infiltrometer. The model predicted, accurately, an average of 46% of the applied Br- leached below the 0.80 m depth. Mcan values of bromide concentration in the soil profile were predicted within two standard deviations of the measured mean for all depths except for the 0.20-0.40 m depth increment where the model overpredicted the bromide concentration. The model predictions of Br- leached were tested against field measurements using several statistical tests. The LEACHM model performed adequately under preferential flow conditions, perhaps because the infiltration rate at each site was used as a model input. This, actually, is some measure of the macropore flow process and suggests that simple models such as LEACHM can be used in the field, as long as a distribution of infiltration rates is used as an input

Modeling of the complex karstic system in Saint-Chaptes (Gard, France): A tool for the synthesis of geological and hydrogeological data, 2000, Josnin J. Y. , Pistre S. , Drogue C. ,
Numerous software packages allow the efficient modeling of the hydrodynamic behaviour of aquifers in continuous media. To study pressure transfer in discontinuous media like karsts, the black-box models are restrictive and the models that consider discrete conduit networks are unsuitable for reservoir scale. We show that the utilization of a continuous media model can lead to useful results, even in the case of complex systems, but needs to be adapted to karst specificity. The problem is approached by studying a hydrogeological system located in the Mediterranean Languedoc region: the S-t-Chaptes basin. This system consists of three superposed aquifers included in four different stratigraphic series. The main aquifer is a karst formation in contact with two other karst formations that belong to different hydrogeologic systems. Considering geological data in addition to hydrological data and with the hypothesis of a relative homogenization of the karst's hydraulic behaviour on a large spatial scale for daily to monthly increments, the model that takes into account the relations with the other aquifers allows (i) a preliminary identification of the main heterogeneities inside the reservoir; (ii) the location of barriers and low-permeability zones that isolate some parts of the aquifer; (iii) the observation of a curious behaviour of the piezometric levels in the confined zones of the aquifer; and (iv) the characterization of the exchanges with the other low-volume but existing aquifers

Results from the Big Spring basin water quality monitoring and demonstration projects, Iowa, USA, 2001, Rowden R. D. , Liu H. B. , Libra R. D. ,
Agricultural practices, hydrology, and water quality of the 267-km(2) Big Spring groundwater drainage basin in Clayton County, Iowa, have been monitored since 1981. Land use is agricultural; nitrate-nitrogen (-N) and herbicides are the resulting contaminants in groundwater and surface water. Ordovician Galena Group carbonate rocks comprise the main aquifer in the basin. Recharge to this karstic aquifer is by infiltration, augmented by sinkhole-captured runoff. Groundwater is discharged at Big Spring, where quantity and quality of the discharge are monitored. Monitoring has shown a threefold increase in groundwater nitrate-N concentrations from the 1960s to the early 1980s. The nitrate-N discharged from the basin typically is equivalent to over one-third of the nitrogen fertilizer applied, with larger losses during wetter years. Atrazine is present in groundwater all year; however, contaminant concentrations in the groundwater respond directly to recharge events, and unique chemical signatures of infiltration versus runoff recharge are detectable in the discharge from Big Spring. Education and demonstration efforts have reduced nitrogen fertilizer application rates by one-third since 1981. Relating declines in nitrate and pesticide concentrations to inputs of nitrogen fertilizer and pesticides at Big Spring is problematic. Annual recharge has varied five-fold during monitoring, overshadowing any water-quality improvements resulting from incrementally decreased inputs

Is the water still hot? Sustainability and the thermal springs at Bath, England, 2002, Atkinson Tc, Davison Rm,
The hot springs at Bath are the largest natural thermal source in Britain. Sustainable use of the waters for a spa requires maintenance of their temperature and flow rate. Together with smaller springs at Hotwells, Bristol, they form the outflow from a regional thermal aquifer that occurs where the Carboniferous Limestone is buried at depths > 2.7 km in the Bristol-Bath structural basin. The aquifer is recharged via limestone outcrops forming the south and west portions of the basin rim. Current knowledge of the basin's structure is reviewed, and important uncertainties identified concerning the hydrogeological role of thrust faults which may cut the limestone at depth. A simple numerical model is used to determine the possible influence of thrusts upon groundwater flow within the thermal aquifer. Comparison of the modelled flow patterns with geochemical data and structure contours eliminates the hypothesis that thrusts completely disrupt the continuity of the aquifer. The most successful model is used to simulate the possible impact of dewatering by large quarries at the limestone outcrops north and south of Bath. Substantial reductions in modelled flow at Bath result from proposed dewatering in the eastern Mendips, although the steady-state approach adopted has severe limitations in that it does not take account of the incremental staging of actual dewatering, nor allow for partial restitution of groundwater levels. The geological uncertainties highlighted by the modelling could be addressed by future research into the effect of thrusts on the continuity of the Carboniferous Limestone. More refined modelling to predict the timing of possible impacts of quarry dewatering will require measurements of the storativity of the thermal aquifer

Cambial growth of Swietenia macrophylla King studied under controlled conditions by high resolution laser measurements, 2003, Dunisch O, Schulte M, Kruse K,
The kinetics of phloem and xylem formation of two-year-old plants of Swietenia macrophylla King (true mahogany) was studied in a model system along the shoot circumference (experiment 1) and along the shoot axis (experiment 2). The radius increment of the shoot was registered by high resolution laser measurements (accuracy: 2 mum) in a spatial resolution of 7.8 to 41.3 mum along the stem circumference and 1.5 mm along the stem axis. The temporal resolution of the measurements was 2 s in experiment 1 and 20 s in experiment 2. The radius increment of the shoot detected by the laser measurements was predominately due to the radial enlargement of the phloem and xylem derivatives. On the phloem side the reinitiation of radial cell enlargement after a cambial dormancy occurred first in sieve tubes with contact to ray parenchyma cells, while on the xylem side the radial cell enlargement of vessels and paratracheal parenchyma was induced almost simultaneously along the shoot circumference. In the phloem and xylem derivatives, which were formed first after the cambial reactivation, radial cell enlargement was induced almost simultaneously along the shoot axis. In more advanced phases of phloem and xylem formation, radial cell enlargement of phloem and xylem derivatives was induced shoot downwards with a rate of approximately 13 mm per min. The mean rate of radial cell enlargement of the phloem and xylem derivatives was 2.26 and 4.37 mum per min, respectively. These findings suggest that the kinetics of cambial growth of tropical tree species differ significantly from kinetics observed in trees from temperate regions. The laser measurements might provide a useful experimental approach for studies of cambial activity in situ

Magmatic and Hydrothermal Chronology of the Giant Rio Blanco Porphyry Copper Deposit, Central Chile: Implications of an Integrated U-Pb and 40Ar/39Ar Database, 2005, Deckart K, Clark Ah, Celso Aa, Ricardo Vr, Bertens An, Mortensen Jk, Fanning M,
The history of hypabyssal intrusion and hydrothermal activity in the northeastern and central parts of the be-hemothian (sensu Clark, 1993) Rio Blanco-Los Bronces porphyry copper-molybdenum deposit is clarified on the basis of integrated U-Pb and 40Ar/39Ar geochronology. Isotope dilution thermal ion mass spectrometry (ID-TIMS) U-Pb dates for zircon separates and ID-TIMS and sensitive high resolution ion microprobe (SHRIMP) dates for single zircon grains in pre-, syn- and late-mineralization volcanic and intrusive host rocks in the Rio Blanco, Don Luis, and Sur-Sur mining sectors provide a temporal framework for interpretation of incremental-heating and spot-fusion 40Ar/39Ar dates for, respectively, magmatic biotite and hydrothermal biotite, muscovite, and orthoclase. The ore deposit is hosted in part by 16.77 {} 0.25 to 17.20 {} 0.05 (2{sigma}) Ma andesitic volcanic strata of the Farellones Formation, but the major host rocks are units of the San Francisco batholith, including the 11.96 {} 0.40 Ma Rio Blanco granodiorite (mine terminology), the 8.40 {} 0.23 Ma Cascada granodiorite, and the 8.16 {} 0.45 Ma diorite. Hypabyssal dacitic intrusions (late porphyries) emplaced into the batholith yield 206Pb/238U ID-TIMS dates ranging from 6.32 {} 0.09 Ma (quartz monzonite porphyry), through 5.84 {} 0.03 Ma (feldspar porphyry) to 5.23 {} 0.07 Ma (Don Luis porphyry). The late-mineralization Rio Blanco dacite plug yields a SHRIMP zircon age of 4.92 {} 0.09 Ma. The 40Ar/39Ar plateau ages for phenocrystic biotites in quartz monzonite porphyry, feldspar porphyry, and Don Luis porphyry, as well as the preore diorite, range only from 5.12 {} 0.07 to 4.57 {} 0.06 Ma. All are significantly younger than the corresponding zircons and exhibit no correlation with intrusive sequence. The 40Ar/39Ar ages for hydrothermal biotite and orthoclase veins within the San Francisco batholith units fall in a narrow interval from 5.32 {} 0.27 to 4.59 {} 0.11 Ma. Hydrothermal sericites (muscovite), one associated with chalcopyrite, yielded spot-fusion ages of 4.40 {} 0.15 Ma (Rio Blanco granodiorite hosted) and 4.37 {} 0.06 Ma (Don Luis porphyry hosted). Comparison with the ID-TIMS and SHRIMP zircon ages indicates that most of the 40Ar/39Ar ages, even 95 percent plateaus, do not record initial magmatic cooling or hydrothermal alteration-mineralization events, evidence for quasipervasive reheating to at least 300{degrees}C by successive intrusions. Published Re-Os ages for two molybdenite samples range from 5.4 to 6.3 Ma and overlap extensively with the zircon U-Pb ages for the late porphyries. They imply that Cu-Mo mineralization overlapped temporally with the emplacement of, at least, quartz monzonite porphyry and feldspar porphyry units of the late porphyry suite and was, therefore, contemporaneous with the rise of dacitic melts to subvolcanic levels. Hydrothermal activity is inferred to have continued until 4.37 {} 0.06 Ma, following intrusion of the Don Luis porphyry and the early stages of emplacement of the Rio Blanco dacite plug complex. Hypogene Cu-Mo mineralization therefore probably persisted for 2 m.y. The geochronologic data do not resolve whether ore formation was continuous or episodic, but the observed crosscutting relationships between intensely altered and mineralized country rocks and less altered and mineralized late porphyry bodies support a model in which the ascent of metal-rich brines from an unexposed zone of the parental magma chamber was periodically stimulated by magma perturbation and hypabyssal intrusion

Heterogeneity in Fill and Properties of Karst-Modified Syndepositional Faults and Fractures: Upper Permian Capitan Platform, New Mexico, U.S.A, 2006, Kosa Eduard, Hunt David W. ,
This study examines the heterogeneity in properties of syndepositional faults and fractures found in the Upper Permian Capitan carbonate platform, Guadalupe Mountains, New Mexico. Syndepositional faults and fractures grew incrementally, and were repeatedly exploited by early karst as the platform developed. Primary fault and fracture rocks were preferentially dissolved to form structure-controlled paleocaverns, which were subsequently filled with platform-derived sediments. These are divided here into three groups: (i) carbonate-dominated, (ii) siliciclastic-dominated, and (iii) mixed carbonate-siliciclastic lithologies. The affinity of the paleocavern-filling deposits to platform strata permits linking of the different fill types to different stages of sea-level cycle. Consequently, periods of dissolution and deposition within paleocaverns can be tied to the platform's sequence stratigraphy. Paleocavern-filling sediments have a distinct vertical stratigraphy, and are observed to vary with distance from the platform margin over a distance of 2.6 km. Their distribution is thus to some extent predictable. Vertical and lateral variability in paleocavern fill is chiefly related to siliciclastic-filled karstic chimneys that narrow downwards and tend to become more frequent and laterally extensive upwards. This is because upper structural levels of fault and fracture zones were more frequently opened by early karst, and also because siliciclastics are not prone to dissolution, whereas carbonates are. Across platform, karst-modified faults and fractures located close to the platform margin are dominated by carbonate lithologies. The proportion and vertical penetration of siliciclastics increases with distance from platform margin. These patterns appear to reflect variations in the frequency and duration of subaerial exposure events across the basinward-inclined Capitan platform. The results of this study have implications for understanding properties of early faults and fractures in carbonate strata. Faults and fractures presented here are heterogeneous, and the heterogeneity is related principally to distribution of sedimentary rocks within paleocaverns developed along them. As a consequence, their properties are not related to dimensions or throw, as is the case for faults and fractures within siliciclastic rocks. Data and interpretations presented here have implications for Capitan hydrocarbon reservoirs, and can be applied to characterization of faults and fractures in other carbonate platforms subjected to early deformation

Chaotic breccia along the Dent Fault, NW England: implosion or collapse of a fault void?, 2006, Woodcock N. H. , Omma J. E. , Dickson J. A. D. ,
A body of chaotic breccia along the reverse-oblique Dent Fault zone is ascribed to hanging-wall collapse into persistent voids created by geometric mismatch of fault walls, although some implosion into transient voids is a possibility. The breccia comprises a 20 m wide body of hanging-wall lithologies, with a chaotic clast-supported fabric that contrasts with the fitted-fabric breccias typical of the Dent Fault damage zone. The breccia body has crude bedding defined by clast shape and size contrasts. The void fill is cut by Variscan fault strands, which, together with its ferroan calcite and barite cement, prove its late Carboniferous rather than recent age. It is shown that any fault void, transient or persistent, had a smaller aperture than the final width of the breccia body, and no more than 5 m; a span that can be supported to depths of 2 or 3 km. However, cement zonation in the breccia fill suggests that the void opened in multiple increments, each of an aperture compatible with the maximum displacement in any one event along the Dent Fault. The Dent Fault example highlights the possible general importance of fault-void collapse but also the problems in distinguishing it from implosion processes

Fossil population structure and mortality of the cave bear from the Mokrica cave (North Slovenia), 2007, Debeljak, I.

The fossil population structure of the cave bear from the Mokrica cave was evaluated to provide new data concerning the behaviour and mortality of this extinct species. Age at death was estimated for 128 different individuals by analysing cementum increments, root formation and crown wear of left M1 teeth. After the frequency distribution of specimens through one- year intervals, the mortality trends can be estimated for various lifetime periods, and interpreted in accordance with data for present-day bears. The original death assemblage was presumably juvenile-dominated. Extremely fragile molars of less than 6 month old cubs did not get preserved. Yearlings are the most numerous age class in the fossil population from the Mokrica cave. Mortality drastically dropped after cave bears survived their first hibernation in the second winter. The lowest mortality rate was observed in the 9-15 years age group, when cave bears would be expected to be in their prime. The oldest age recorded by cementum analysis is approximately 30 years, which indicates that the maximum life span was similar to present-day bears. Study of dental tissues shows that the mortality in the cave was seasonally restricted – the majority of deaths in the cave occured during winter and in early spring. Sex structure of the fossil population has been studied on the sample of 750 canines. The significantly higher proportion of males in the group of older juveniles and subadults could be explained by the fact that the weaning period is more critical for males also in present- day bears. In young adults and prime adults the mortality was presumably higher in females. The sex structure of adult bears, especially in the sample of older individuals, indicates that the Mokrica cave was used as winter den mostly by solitary males.

Using Geographic Information System to Identify Cave Levels and Discern the Speleogenesis of the Carter Caves Karst Area, Kentucky, 2011, Peterson E. , Dogwiler T. , Harlan L.

Cave level delineation often yields important insight into the speleogenetic history of a karst system. Various workers in the Mammoth Cave System (MCS) and in the caves of the Cumberland Plateau Karst (CPK) have linked cave level development in those karst systems with the Pleistocene evolution of the Ohio River. This research has shown that speleogenesis was closely related to the base level changes driven by changes in global climate. The Carter Caves Karst (CCK) in northeastern Kentucky has been poorly studied relative to the MCS to the west and the CPK karst to the east. Previously, no attempt had been made to delineate speleogenetic levels in the CCK and relate them to the evolution of the Ohio River. In an attempt to understand cave level development in CCK we compiled cave entrance elevations and locations. The CCK system is a fluviokarst typical of many karst systems formed in the Paleozoic carbonates of the temperate mid-continent of North America. The CCK discharges into Tygarts Creek, which ultimately flows north to join the Ohio River. The lithostratigraphic context of the karst is the Mississippian Age carbonates of the Slade Formation. Karst development is influenced by both bedding and structural controls. We hypothesize that cave level development is controlled by base level changes in the Ohio River, similar to the relationships documented in MCS and the karst of the Cumberland Plateau The location and elevation of cave entrances in the CCK was analyzed using a GIS and digital elevation models (DEMs). Our analysis segregated the cave entrances into four distinct elevation bands that we are interpreting as distinct cave levels. The four cave levels have mean elevations (relative to sea level) of 228 m (L1), 242 m (L2), 261 m (L3), and 276 m (L4). The highest level—L4—has an average elevation 72 m above the modern surface stream channel. The lowest level—L1—is an average of 24 m above the modern base level stream, Tygarts Creek. The simplest model for interpreting the cave levels is as a response to an incremental incision of the surface streams in the area and concomitant adjustment of the water table elevation. The number of levels we have identified in the CCK area is consistent with the number delineated in the MCS and CPK. We suggest that this points toward the climatically-driven evolution of the Ohio River drainage as controlling the speleogenesis of the CCK area 

Central concepts of karst hydrology, 2013, Palmer, Arthur N.

The solutional growth of karst features involves a simple mass transfer, in which the mass removed from the walls of a void equals the mass removed in solution by flowing water. Mass removed = volume  rock density, and mass in solution = discharge  solute concentration. Therefore (e.g., in a solution conduit) the rate of volume increase = discharge  gain in dissolved load  time / rock density. Density is essentially con-stant, so conduit size depends only on the cumulative values of discharge, dissolution rate, and time. All three are essential, and all are equally important.
Discharge in a conduit depends on catchment area and water balance; and the distribu-tion of water among all solution conduits depends on hydraulic variables and conduit geometry. Dissolution rate varies with rock type, undersaturation, and solution kinetics, the last of which can be determined by laboratory and field measurements. Together, they provide a tool for quantifying the local geomorphic history.
These relationships seem simple, but applying them quantitatively is complex. This requires a finely divided 2- or 3-dimensional grid in which each segment varies in dis-charge and dissolution rate within each of many small time increments. Computer modelers use this approach to simulate conduit growh; but the results depend on the specific boundary conditions of the model.
It is more challenging to use this concept intuitively to solve real field problems, where the variables are only partly understood. In this case, one must show that the water source, dissolution rate, and available time are all great enough to account for the ob-served solution features. All three variables are closely linked by a web of interactive processes, all of which can be expressed quantitatively. Whether the goal is to under-stand what is already known, or to predict the unknown, this approach provides a solid basis for interpreting karst systems.

Sinkholes, pit craters, and small calderas: Analog models of depletion-induced collapse analyzed by computed X-ray microtomography, 2014,

Volumetric depletion of a subsurface body commonly results in the collapse of overburden and the formation of enclosed topographic depressions. Such depressions are termed sinkholes in karst terrains and pit craters or collapse calderas in volcanic terrains. This paper reports the first use of computed X-ray microtomography (?CT) to image analog models of small-scale (~< 2 km diameter), high-cohesion, overburden collapse induced by depletion of a near-cylindrical (“stock-like”) body. Time-lapse radiography enabled quantitative monitoring of the evolution of collapse structure, velocity, and volume. Moreover, ?CT scanning enabled non-destructive visualization of the final collapse volumes and fault geometries in three dimensions. The results illustrate two end-member scenarios: (1) near-continuous collapse into the depleting body; and (2) near-instantaneous collapse into a subsurface cavity formed above the depleting body. Even within near-continuously collapsing columns, subsidence rates vary spatially and temporally, with incremental accelerations. The highest subsidence rates occur before and immediately after a surface depression is formed. In both scenarios, the collapsing overburden column undergoes a marked volumetric expansion, such that the volume of subsurface depletion substantially exceeds that of the resulting topographic depression. In the karst context, this effect is termed “bulking”, and our results indicate that it may occur not only at the onset of collapse but also during progressive subsidence. In the volcanic context, bulking of magma reservoir overburden rock may at least partially explain why the volume of magma erupted commonly exceeds that of the surface depression.

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