Natural Sinkholes Research Articles

Land use and limitations in the sinkhole and polje karst of the Ksiromero Region, Western Greece

Ksiromero occupies an area of 107 km2 in the northeast section of the Prefecture of Aitoloakarnania in western Greece. Its karst is developed primarily on beds of 10–200 m thick Triassic carbonate breccia conglomerates which underlie 70 % of the region. Other karstified units overly 200–300 m thick sequences of upper Triassic to early Jurassic limestones and dolomites and an underlying 150 m thick Triassic gypsum deposit. Major karst features include sinkholes and poljes that capture all surface water. Open caves and conduits are rare due to in-fill by residual terra rossa soils. “Ksiromero” is Greek for “dry place.” While in one of the wetter regions of Greece, with a mean annual precipitation of 962–1,040 mm and a mean evapotranspiration rate of 47 %, no perennial springs are known, surface water is rare, and accessible groundwater is minimal. Some shallow wells in the breccia conglomerate serve as small, local water supplies. Geochemical analyses of water samples from two wells show significant differences due to aquifer type (limestone versus terra rossa) but groundwater is suitable at least for irrigation and livestock and probably human consumption. Generally, domestically used water is supplied to Ksiromero from a neighboring region. Water for agriculture is stored in more than 75 reservoirs, some of which are natural sinkholes but most are excavated in terra rossa soils of poljes and large sinkholes. Shallow groundwater occurs in some of these reservoirs, as well as seasonally captured storm water, but much is pumped in from the adjacent region or from nearby wells. This system is adequate for the area’s modest water needs, but not for potential increased demand. Most land use is farming and pasture, and limited to the relatively flat floors of sinkholes and poljes. The absence of sanitary landfills and other agricultural contaminants potentially threaten groundwater quality, but the impacts are not presently quantifiable due to insufficient aquifer characterization.

Remains of Holocene giant pandas from Jiangdong Mountain (Yunnan, China) and their relevance to the evolution of quaternary environments in south-western China

Two subfossil partial skeletons of male giant pandas (Ailuropoda melanoleuca) were recovered, along with remains of 16 other mammalian species, from a natural sinkhole on Jiangdong Mountain (south-western Yunnan, China). The panda and other mammalian bones from the sinkhole's upper chamber yielded tightly clustered accelerator mass spectrometry corrected radiocarbon ages of 8470–8250 yr BP, and the panda remains from the lower chamber were found to be 5025 ± 35 yr BP. The bones represent a natural accumulation of mostly large mammals (>30 kg), which had fallen accidentally into the sinkhole. The Jiangdong Mountain mammal assemblage comprises mostly obligate forest-dwellers such as the giant panda, Asian elephant and Sumatran rhinoceros, but the presence of the horse and gaur suggests a more open woodland habitat. Giant pandas were distributed widely in southern China during the Pleistocene, but are now restricted to dense stands of bamboo within temperate forests surrounding the Sichuan Basin. The evidence from Jiangdong Mountain indicates that suitable habitat for pandas extended west of the Salween River through the mid-Holocene. Rapid deforestation of the area in historical times is suggested by an accumulation of cave fill below the opening of the sinkhole containing pieces of an early to middle Ming Dynasty bowl.

Investigating Ancient Maya Agricultural Adaptation Through Ground Penetrating Radar (GPR) Analysis of Karst Terrain, Northern Yucatán, Mexico

Landscape adaptation on the Northern Yucatán Peninsula, Mexico, is particularly difficult, as soils are thin and the terrain is devoid of any surface water other than the occasional sinkhole (cenote) that connects directly to the groundwater system. Despite this, ancient Maya cities, including Xuenkal, emerged and thrived, likely because of their proximity to natural sinkholes. In the case of Xuenkal, these sinkholes, known locally as rejolladas, have bases above the local water table and, as such, do not provide direct access to the underlying water, but they provide closer access. Recognizing that the presence of rejolladas was likely important to the ancient Maya the purpose of this study is to characterize the rejolladas in terms of their subsurface characteristics, specifically bedrock configuration and soil. Ground penetrating radar analysis, as well as the results of a test pit excavation, confirm the presence of deep soils in the rejollada bases. It seems that the smaller deeper rejolladas have the thickest soils and sediment. The ancient city of Xuenkal is constructed amidst a particularly dense cluster of rejolladas which may have contributed to its location. Rejolladas, containing significantly thicker soils than the surrounding karst surface, and the ability to sustain dense healthy vegetation would have been particularly desirable for the Maya to capitalize on.

Role of Current Versus Historical Hydrology in Amphibian Species Turnover within Local Pond Communities

This study explored how historical and current hydrological conditions covaried with colonization and occupancy probabilities for 14 pond-breeding amphibians at 32 natural sinkhole ponds over a five-year period. Occupancy and colonization were estimated independently for breeding adults and juvenile recruits (metamorphs) of each species using proportion of area occupied (PAO) models that incorporated species detection probabilities. Model selection revealed whether historical or current hydrological conditions are more important in determining occupancy and colonization probabilities for each species. Adults and metamorphs of ranids and most salamanders had occupancy and colonization rates that were best estimated by models that incorporated each pond's historical hydrology. A comparison of colonization and occupancy dynamics for history dependent species indicates that these species contribute little to species turnover within local pond communities. Adult occupancy and colonization of hylid, bufonid, and a pelobatid species were more dependent on the immediate hydrology of a pond within a year. Recruitment dynamics of these same anuran species were best fit by models that incorporated both current and historical pond hydrology. In some years, these species had high probabilities of producing metamorphs in ponds where they had not produced metamorphs in the previous year. Increases or stability in colonization probabilities between years sometimes coincided with stable occupancy probabilities, indicating that these opportunistic species are responsible for species turnover in local communities. Short-term species turnover within local amphibian communities appears to be driven by these opportunistic species and linked to major changes in weather between consecutive years.

A review of natural sinkhole phenomena in Italian plain areas

Italian sinkholes, which are mainly related to karst phenomena (i.e., solution sinkholes, collapse sinkholes, etc.), are widespread along the Apennine ridge and in pedemontane areas where there are carbonatic bedrock outcrops. However, other collapses, which seem unrelated to karst dissolution, have been identified in plain areas with a thick sedimentary cover over buried bedrock. The main goal of this work is to study the geological, geomorphological, and structural setting of these areas to identify the possible mechanism of the generation and evolution of these collapses. About 750 cases were identified by research based on historical archives, specific geological literature, and information from local administrations. Geological, geomorphological, and hydro-geochemical surveys were conducted in 300 cases, supported by literature, borehole, and seismic data. A few examples were discarded because they could be ascribed to karst dissolution, volcanic origin (i.e., maar), or anthropogenic causes. Field studies regarding the other 450 cases are in progress. These cases occur along the Tyrrhenian margin (Latium, Abruzzo, Campania, Tuscany) in tectonic, coastal, and alluvial plains close to carbonate ridges. These plains are characterized by the presence of pressurized aquifers in the buried bedrock, overlaid by unconsolidated sediments (i.e., clay, sands, pyroclastic deposits, etc.). The majority of these collapses are aligned along regional master and seismogenetic faults. About 50% of the studied cases host small lakes or ponds, often characterized by highly mineralized springs enriched with CO2 and H2S. The Periadriatic margin does not seem to be affected by these phenomena, and only a few cases have been found in Sicily, Sardinia, and Liguria. The obtained scenarios suggests that this type of collapse could be related to upward erosion through vertical conduits (i.e., deep faults) caused by deep piping processes whose erosive strength is increased by the presence of acidic fluids. In order to distinguish these collapses from typical karst dissolution phenomena, they are defined as deep piping sinkholes (DPS).

Sinkhole distribution based on pre-development mapping in urbanized Pinellas County, Florida, USA

Abstract Locating sinkholes in Pinellas County, Florida, is confounded by the presence of a cover of Quaternary sediments that mute the surface appearance of these sinkholes. As a first step in addressing the sinkhole hazard in the county, we analysed aerial photographs from 1926 and 1995 that covered the entire county. We digitized all identifiable sinkholes in each set of photographs in a GIS (Geographical Information System) using a set of criteria established to differentiate between karst depressions and depressions resulting from other geological processes. The 1926 photographs, although of low quality, helped to establish a baseline prior to urbanization. The 1995 photographs provided a post-urbanization distribution of natural sinkholes and man-made depression features (e.g. retention ponds). From these two data sets, we are able to assess natural and anthropogenic changes in the karst landscape of the study area. In particular, we discovered that 87% of the sinkhole features identified in the 1926 photographs are no longer present in the photographs from 1995. Many of the lost depressions have been incorporated into retention ponds.

Stygofauna Abundance and Distribution in the Fissures and Caves of the Nardò (Southern Italy) Fractured Aquifer Subject to Reclaimed Water Injections

The demographic growth in developing countries and the increasing pressure of anthropological activities in industrialized states around the world, are leading to a gradual contamination of the natural habitats of our planet. Although the extent of these effects is unclear, the results can already seen in the quality of natural resources, which are intensely stressed by climate changes (greenhouse effect, nutrients load, water consumption, etc.) and by direct contamination of toxic wastes. This could progressively destroy the variety of faunal species and, indeed, recent warming has caused changes in species distribution and abundance. This paper presents an investigation into the possible effects of climate change and anthropological pressures on the ground water fauna present at the Nardò site (Salento peninsula, Southern Italy). Three ecological categories were examined: stygoxenes, stygophiles and stygobionts. The latter are anophthalmic, without pigment, measure up to 10–12 mm, and live in water which moves throughout fissures and karstic caves of carbonate aquifers. These stygofauna are very sensitive to changes, due to environmental stresses, such as water temperature, dissolved oxygen, water salinity, pH and chemical constituents, in their hypogeous habitat. The stygofauna categories are active organisms which contribute to the biodegradation of organic compounds in wastewater artificially (or naturally) injected in the fractured subsoil. Weak information has been available until now about Salento stygofauna ability to resist water pollution caused by human activities. At the Nardò site 12000 m3/d of 2 y effluent from municipal treatment plants have been injected since 1991 in a natural sinkhole. Here, the abundance of the stygofauna, recovered in three wells (Colucci, Brusca and Spundurata cave) at progressive distances from sinkhole, and their distribution have been correlated with ground water constituents. Groundwater quality was monitored on each occasion that stygofauna were collected, during the spring-autumn seasons.

Nest success and conservation status of the Blue Swallow Hirundo atrocaerulea in Swaziland

The Blue Swallow Hirundo atrocaerulea is a globally threatened species endemic to sub-Saharan Africa. The total population breeding south of the Limpopo River (i.e. in South Africa and Swaziland) probably numbers around 100 pairs. A significant proportion of these birds breed in Swaziland, but to date little has been published on this population. Suitable breeding habitat has been reduced significantly in the country in recent decades, due mostly to afforestation with exotic timber plantations, with urbanization playing a lesser role. In Swaziland, breeding sites are restricted to grasslands above 1,200 m, but mostly above 1,300 m. Timing of egg laying is bimodal indicating double brooding. The number of nests initiated in a season is weakly correlated with rainfall in preceding months. Nests were built predominantly in disused antbear Orycteropus afer burrows, with smaller numbers in natural sinkholes. Mean clutch size was 2.80, and 61% of eggs laid resulted in fledged offspring. Mean productivity was 1.30 fledglings per pair per nest attempt. These figures suggest that breeding success is not currently being reduced in Swaziland. The minimum total population currently thought to be breeding in Swaziland is 10 pairs, but this is based on intensive studies of only part of the suitable range. It is recommended that a complete survey be conducted covering the entire range of the species in Swaziland.

The Potential Role of Small Depressions as Water Storage Features in the Central Maya Lowlands

Small depressions are a frequent landscape feature in the northeast Petén and northwestern Belize. Although generally considered the remains of seasonal ancient Maya water cisterns, they have not been subject to systematic study. Excavation of 16 depressions in northwestern Belize showed that these features are either natural sinkholes (dolines) or quarried cavities. In three depressions, quarrying for construction materials and mining for clay was evident and two depressions are the remains of collapsed chultuns. Depressions probably also served as areas where household activities were carried out, they may have played a role as gardens, and were used as trash dumps. For one quarter of the sample, a water storage function was established. Water input-output calculations showed that these features could have held water year round and thus theoretically could have played a much more important role in supplying water than commonly assumed. The study indicates that Classic Maya population could have relied on decentralized water sources and suggests that hypotheses of centralized water management in the central Maya lowlands should be critically reviewed.

Assessment of Water Quality After 10 Years of Reclaimed Water Injection: The Nardò Fractured Aquifer (Southern Italy)

AbstractExperimental studies have been carried out in a fractured coastal aquifer of the Salento region (Nardò, Italy), which has been subjected to 12,000 m3/day of treated municipal waste water injected into a natural sinkhole since 1991. The analytical parameters of ground water sampled in 30 monitoring wells in the area down gradient from the sinkhole, taking into account the direction of ground water flow, have been compared before and after injection. The water table mound (1.5 m), the reduction of sea water extent (2 km), and the spreading of injected pollutants were evaluated by means of a mathematical model. The predicted values in the monitoring wells were adjusted to inorganic nitrogen biodegradation using transformation rates developed in laboratory tests. After 10 years, the injection has increased the volume of the available resource for agricultural and drinking water use, without any notable decrease in the preexisting ground water quality. Moreover, to preserve water resources from pollution, the mathematical model allowed the maximum constituent concentrations (standards) in waste water reclamation for recharge to be identified. A precautionary area around the sinkhole was also defined so that withdrawal prohibition could be implemented to avoid risks to human health.

Limnological and morphometrical data of eight karstic systems `cenotes' of the Yucatan Peninsula, Mexico, during the dry season (February–May, 2001)

The karstic nature of the Yucatan Peninsula allows the formation of natural sink-holes from the dissolution of calcareous rock. These systems are almost the only epigean source of fresh water available in this region. In spite of their biological importance, little is known about the morphometric and limnologic characteristics of these karstic systems. We measured limnological variables in eight cenotes in central Quintana Roo during February–May, 2001. Zooplankton biomass and chlorophyll a were also measured in order to determine if the behavior of primary and secondary production was related to environmental parameters. Important short-term changes were observed in nutrients (NO3−, NO2−, PO43-), biomass, and chlorophyll a. The morphometrically conditioned productivity (MCP), which evaluates the cumulative effect of several morphometric variables on production (area, maximum length, shoreline development, perimeter), showed a negative correlation with respect to zooplankton biomass, as did also both pH and temperature. Conversely, NO3− and NO2− had a positive correlation with zooplankton biomass. No correlation was found for chlorophyll a. Significant differences in NO3− (F = 61.52, p<0.001), NO2− (F = 7.36, p<0.001), zooplankton biomass (F = 17.57, p<0.001), chlorophyll a (F = 62.19, p<0.001), and conductivity (F = 497.49, p<0.001) were found among the systems. These results indicate the existence of sharp differences between these karstic systems (oligotrophic, with smaller area, deep and less productive) and non-karstic ones, (eutrophic, larger area, shallow and more productive) but are similar to previous data from other karstic systems of Mexico and other parts of the world. However, understanding of these fragile tropical systems is in the initial phase. It is necessary to increase the intensity of these studies in order to allow a full explanation of their limnological behavior.

The Arecibo Observatory

The Arecibo radar and radio telescope stands on a triangular platform as it hovers 220 m above the ground. The spherical dish resides in a natural sink hole, one of the largest in Puerto Rico. This platform is the focal point of an isolated scientific outpost where staff and students ply their trade. The Arecibo Observatory is a US national laboratory managed by Cornell University (New York) through a cooperative agreement with the National Science Foundation (NSF). The bulk of the astronomy work done focuses on stellar evolution, galaxy formation, and pulsars.

Effects of Individual Variation in Size on Growth and Development of Larval Salamanders

Theoretical population models suggest that variation among individuals can affect population—level properties like stability and equilibrial density. Few studies, however, have tested the importance of individual variation to factors affecting population dynamics (e.g., average individual growth rates, developmental rates, survivorship, etc.) using natural populations. We conducted a field experiment designed to test effects of larval density and individual variability in body size on growth and development of larval tiger salamanders (Ambystoma tigrinum nebulosum). We performed our experiment in a natural sinkhole lake in central Arizona; experimental populations differing in density and initial variability in body size were held in nylon mesh enclosures. Effects of individual variability in size were examined independently of any effects due to mean body size of the population or total population biomass. Density affected growth rates and development to metamorphosis of experimental larvae in a manner consistent with other studies. Initial variability in body size did not affect larval growth rates or diets but did interact with density to affect survivorship and development: experimental larvae held with similarly sized individuals experienced lower survivorship and were metamorphosing earlier than experimental larvae held with variably sized individuals. These effects did not appear to be mediated by size—specific competitive abilities but may have been mediated by individual behavioral responses to size structure. This study underscores the importance of incorporating information about interindividual variability into our understanding of processes affecting population dynamics.

Seven Bat Species from the Kaibab Plateau, Arizona, with a New Record of Euderma maculatum

The study areas, Fracas Lake and Fracas Camp Meadow, were 9.5 km SSW of Jacob Lake, Coconino Co., Arizona (SW?, SE?, Sec. 1, T37N, R1E, elev. 2,507 m). The two sites were 0.25 km apart, separated by a stand of Pinus ponderosa and Populus tremuloides. Fracas Lake was a 0.4ha natural limestone sinkhole lake, surrounded by Petran montane conifer forest consisting of mature stands of P. ponderosa with a few mature P. tremuloides. The lake was permanent and varied in depth seasonally from 0.75 to 1.75 m. A floating mat of rushes (Scirpus sp.) rising 1 m from the surface of water covered half of the lake

Induced Sinkholes: An Engineering Problem

Induced sinkholes are those related to man's activities, whereas natural sinkholes are not. Induced sinkholes are divided into two types: those resulting from a decline in the water table due to ground-water withdrawals and those resulting from construction. Almost all induced sinkholes occur where cavities develop in residual or other unconsolidated deposits overlying openings in carbonate rocks. The downward migration of the deposits into underlying openings in bedrock and the formation and collapse of resulting cavities are caused or accelerated by a decline in the water table that results in: (1) Loss of buoyant support; (2) increase in the velocity of movement of water; (3) water-level fluctuations at the base of unconsolidated deposits; and (4) induced recharge. Most sinkholes resulting from construction are due to the diversion of drainage over openings in bedrock.

Observations on the Breeding of Turquoise-Browed Motmots in Yucatán

Motmots typically excavate burrows in banks and lay their eggs on bare earth in terminal chambers of these b urrows. The works of Skutch (1947), Klaas (1968), and Orejuela (1977) indicate that in much of Middle America, the behavior of the Turquoise-browed Motmot (Eumomota superciliosu) follows this pattern. In areas of the Yucatan Peninsula that possess shallow soils, however, this motmot commonly frequents the vicinity of natural wells or sinkholes (cenotes) and cave entrances during the breeding season (Gaumer 18811882, Klaas 1968, Orejuela 1977, Reddell 1977), using recesses in the limestone walls as sites for egg deposition. Differences among the observations of these authors and others (see also, Paynter 1955) suggest considerable plasticity in the reproductive pattern of this motmot. Here we present data on E. superciliosa taken at yet a different type of breeding site: elevated apertures in the walls and ceilings of rooms of archaeological ruins at Uxmal, Kabah, and Sayil, Yucatan, Mexico. Observations were made at Uxmal on 19 June and 3 and 4 July 1979, and at Kabah and Sayil on 3 July 1979. On all dates, Turquoise-browed Motmots were abundant (at least 50) near The Governor’ s Palace and The Nunnery Quadrangle at Uxmal. Many of the birds were carrying food to nestlings, which were vocalizing in apertures, rectangular and circular in cross section, which had been made by the Maya in the walls and ceilings of both the inner and outer rooms of these structures. Several rooms sheltered more than one pair of motmots. Here, and at Kabah and Sayil, we saw no agonistic behavior or visible manifestation of territoriality. On 3 and 4 July, recently fledged young (as judged by their size and flight ability) were observed at Uxmal; they uttered vocalizations similar to, but softer than, those given by adults. Twice on 3 July, and once on 4 July, an adult was flushed from the same clutch of three (clean) white eggs deposited on a thin layer of fine-particulate breakdown on the floor of a short, broad (approximately 40 cm length, 25 cm width, 14 cm height) hole located 2.5 m above floor level in the inner room of a 2-room complex within The Governor’ s Palace at Uxmal. This observation supports Skutch’ s (1945) judgment that the attribution by Gaumer (18811882) of relatively elaborate nests to well (cenote?)nesting Yucatan Turquoise-browed Motmots was questionable. Together with our sightings of recently fledged young on these dates, this observation also supports the data of Klaas (1968) taken at a bank-burrowing colony near Champoton, Campeche on 9 July 1962 and his hypothesis that these motmots may rear two broods per season. Recent work on this species near Escircega, Campeche, by Orejuela (1977), however, indicates that early July clutches in that area represent late starts and renestings. An additional observation made at Uxmal is of interest in regard to potential helpers at the nest in this motmot: On 4 July, we watched three individuals of similar size (apparently adult, but rectrices were hidden) perched on a rock within 30 cm of each other with prey in their bills; one held a large scorpion. The group appeared to be waiting to enter the chamber from which we watched. Unfortunately, they flushed at the approach of other visitors to the area, and we could not continue observation. I thank James Reddell and Norberto Gonzalez for their assistance.

Induced and natural sinkholes in Alabama — A continuing problem along highway corridors : Newton, J G Transp Res Rec, N612, 1976, P9–16

Sinkholes are divided into two categories, induced (man-related) and natural. Since 1900, an estimated 4000 induced sinkholes or related features have formed in Alabma,; fewer than 50 natural sinkholes have been reported. Most induced sinkholes are caused by water-level declines due to pumpage; others result from factors associated with construction. Almost all occur where cavities develop in unconsolidated deposits overlying openings in bedrock. The downward migration of the deposits and the development of the cavities are caused or accelerated by a water-level decline that results in the loss of buoyant support and increases the velocity of water movement, the magnitude of water-level fluctuations, and the induced recharge. Most sinkholes caused by construction are due to the diversion of drainage over openings in bedrock. Many natural sinkholes are caused by the collapse or downward migration of unconsolidated deposits into openings in bedrock. The downward migration that sometimes creates cavities in the deposits results from natural declines in the water table, progressive enlargement by solution of openings in the top of bedrock, or a combinstion of both. The failure of bedrock roofs over solutionally enlarged openings is a rare occurrence. The time required for the development of natural sinkholes is far greater than that associated with induced sinkholes. /Author/