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Articles 421 - 450 of 491

Full-Text Articles in Geology

Minerogenesis Of Volcanic Caves Of Kenya, Paolo Forti, Ermanno Galli, Antonio Rossi Jan 2003

Minerogenesis Of Volcanic Caves Of Kenya, Paolo Forti, Ermanno Galli, Antonio Rossi

International Journal of Speleology

Kenya is one of the few countries in which karst cavities are scarce with respect to volcanic ones, which are widespread throughout the whole country. The great variability in lava composition allowed the evolution of very different cavities, some of which are amongst the largest lava tubes of the world. As normal for such a kind of cave, the hosted speleothems and cave minerals are scarce but important from the minerogenetic point of view. Anyway up to present no specific mineralogical research have been carried out therein. During the 8th International Symposium on Volcanospeleology, held in Nairobi in February 1998, …

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Caves And Karsts Of Northeast Africa, William R. Halliday Jan 2003

Caves And Karsts Of Northeast Africa, William R. Halliday

International Journal of Speleology

At least potentially karstifiable rocks cover much of the surface of Egypt and northern Libya. Study of caves and other karstic features of this region has been hampered by lack of roads, rapid disintegration of the surface of friable, poorly consolidated limestone, wind-blown sand and other factors. Interbedding with marly aquicludes hampers speleogenesis locally. Calcareous and evaporite karsts are present, however, and their waters are important albeit generally limited resources. Large quantities of fresh water are lost through submarine springs downslope from Libya’s Gebel al Akhdar range; the caves and karst of that range may be among the world’s greatest. …

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Human Impact On Karst: The Example Of Lusaka (Zambia), Jo De Waele, Roberto Follesa Jan 2003

Human Impact On Karst: The Example Of Lusaka (Zambia), Jo De Waele, Roberto Follesa

International Journal of Speleology

Lusaka, the capital of Zambia with over 2,000,000 inhabitants, is built on an extensive plateau composed mainly of schists and dolomitic marbles, constituting a very important aquifer that provides the city with almost half of its drinking water needs. Recent demographic growth, leading to uncontrolled urban expansion, and mismanagement of the water resource and of urban waste has lead, in the past 20 years, to an overexploitation of the aquifer and to a generalised water quality depletion, putting in serious danger the future social and economical development of the capital. This third world city has, for these reasons, become a …

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Littoral Dripstone And Flowstone--Non-Spelean Carbonate Secondary Deposits, Danko Taborosi, Kevin Stafford Jan 2003

Littoral Dripstone And Flowstone--Non-Spelean Carbonate Secondary Deposits, Danko Taborosi, Kevin Stafford

International Journal of Speleology

Speleothem-like dripstone and flowstone deposits can form in the non-spelean environments of marine notches on tropical carbonate coastlines. Hereby termed “littoral dripstone” and “littoral flowstone” to distinguish them from genuine cave deposits, they reflect the basic speleothem types: draperies, stalactites, stalagmites, and columns. Nevertheless, these formations lack the luster and crystallinity of cave analogues, and are not nearly as well-developed, dense, and massive. They are composed of layered microcrystalline aragonite and calcite, are generally highly porous, and invariably overlie dissolutional and bioerosional karren. Because true speleothems, often found in the remnants of solution voids breached by coastal erosion, are also …

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Tree-Mould Caves In Slovakia, Ludovít Gaál Jan 2003

Tree-Mould Caves In Slovakia, Ludovít Gaál

International Journal of Speleology

Four tube-shaped caves are described in this work, which origined in consequence of weathering the trees. Their length ranges from 5.8 to 17 m. All of them occur in neovolcanic rocks of Middle Slovakia, in epiclastic andesite conglomerates, breccias or in the tuffs. Some other caverns are close to the entrance of this caves, however they are inaccessible for a man. Thin rim of silicates (opal or chalcedony) occurs in some of them.

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Contribution To The Speleology Of Sterkfontein Cave, Gauteng Province, South Africa, J. E. J. Martini, P. E. Wipplinger, H. F. G. Moen, A. Keyser Jan 2003

Contribution To The Speleology Of Sterkfontein Cave, Gauteng Province, South Africa, J. E. J. Martini, P. E. Wipplinger, H. F. G. Moen, A. Keyser

International Journal of Speleology

The authors present more data about the speleological aspect of the Sterkfontein Cave, famous for its bone breccia which yielded abundant hominid remains. They also briefly review the previous voluminous studies by numerous authors, which are mainly dealing with the paleontology, stratigraphy and sedimentology of the breccia. The present investigations were oriented to hitherto poorly investigated aspects such as detail mapping of the cave, its country rock stratigraphy and recording the underground extension of the basal part of the breccia body. The cave consists of a complex network of phreatic channels, developed along joints in Neoarchaean cherty dolostone over a …

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Longshore Sand Transport – Initial Results From The Large-Scale Sediment Transport Facility, Ping Wang, Bruce A. Ebersole, Ernest R. Smith Mar 2002

Longshore Sand Transport – Initial Results From The Large-Scale Sediment Transport Facility, Ping Wang, Bruce A. Ebersole, Ernest R. Smith

Geology Faculty Publications

Accurate predictions of the total rate of longshore sand transport (LST) and its cross-shore distribution pattern in the surf zone are central to many coastal engineering studies. Present understanding and methods for calculating the LST rate are largely developed based on field studies (e.g., Komar and Inman 1970; Inman et al. 1981; Kraus et al. 1982; Bodge and Dean 1987a, b; Dean 1989; Schoonees and Theron 1993; Miller 1998; Wang, Kraus, and Davis 1998; Wang 1998; Wang and Kraus 1999; Miller 1999). The Coastal Engineering Research Center (CERC) formula (Shore Protection Manual 1984), which is based on field measurements, is …

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Cave Breakdown By Vadose Weathering, R. A. L. Osborne Jan 2002

Cave Breakdown By Vadose Weathering, R. A. L. Osborne

International Journal of Speleology

Vadose weathering is a significant mechanism for initiating breakdown in caves. Vadose weathering of ore bodies, mineral veins, palaeokarst deposits, non-carbonate keystones and impure, altered or fractured bedrock, which is intersected by caves, will frequently result in breakdown. Breakdown is an active, ongoing process. Breakdown occurs throughout the vadose zone, and is not restricted to large diameter passages, or to cave ceilings. The surfaces of disarticulated blocks are commonly coated, rather than having fresh broken faces, and blocks continue to disintegrate after separating from the bedrock. Not only gypsum, but also hydromagnesite and aragonite are responsible for crystal wedging. It …

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Subsidence Hazards As A Consequence Of Dam, Reservoir And Tunnel Construction, Petar Milanovic Jan 2002

Subsidence Hazards As A Consequence Of Dam, Reservoir And Tunnel Construction, Petar Milanovic

International Journal of Speleology

Considering all man-made structures in karst areas, dams, reservoirs and tunnels are the most vulnerable in relation to induced subsidence and caverns. Reservoirs that are located entirely or partially on karstified rocks covered with unconsolidated sediments are especially subsidence-prone. As a consequence of induced subsidence a number of reservoirs in karst areas failed and were never fully filled. Such subsidence formation is very damaging because the development is unpredictable and practically instantaneous. Reservoirs in karst areas may fail to fill despite an extensive site investigation programs and sealing treatment. Every problem is unique and past experiences are never repeated. This …

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Subsidence Hazards In Different Types Of Karst: Evolutionary And Speleogenetic Approach, Alexander Klimchouk Jan 2002

Subsidence Hazards In Different Types Of Karst: Evolutionary And Speleogenetic Approach, Alexander Klimchouk

International Journal of Speleology

The typology of karst, based on distinguishing the successive stages of general hydrogeological evolution, between which major boundary conditions and the overall circulation pattern change considerably, gives a natural clue, properly to classify and tie together karst breakdown settings, speleogenetic styles and breakdown development mechanisms. Subsidence hazards vary substantially between the different karst types so that classifying individual karst according to typology can provide an integrated general assessment. This provides a useful basis for selection and realization of region- and site-specific assessment schemes and management strategies. Intrastratal karst types, subjacent karst in particular, are most potent in generating subsidence problems. …

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The Engineering Classification Of Karst With Respect To The Role And Influence Of Caves, Tony Waltham Jan 2002

The Engineering Classification Of Karst With Respect To The Role And Influence Of Caves, Tony Waltham

International Journal of Speleology

The engineering classification of karst defines various complexities of ground conditions, in terms of the hazards that they provide to potential construction. Karst is divided into five classes (from immature to extreme). The three key parameters within the classification are caves (size and extent), sinkholes (abundance and collapse frequency) and rockhead (profile and relief). As one component of karst, caves are a hazard to foundation integrity, though natural surface collapses over caves are extremely rare. A cave roof is normally stable under engineering loading where the roof thickness is greater than 70% of the cave width. Construction can proceed over …

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Stability Appraisal Of The Medvedova Konta Pothole, Jože Kortnik Jan 2002

Stability Appraisal Of The Medvedova Konta Pothole, Jože Kortnik

International Journal of Speleology

Until 1956 the underground details of areas around Pokljuka were practically unknown due to the area’s non-karstic outward appearance. However, the presence of karst phenomena on this Alpine plain is undoubtedly indicated, primarily by the absence of a surface drainage network. A mathematical model was made of the Medvedova konta pothole, in which two different sets of material properties were used, corresponding to the Triassic limestone that forms the bedrock under the greater part of Pokljuka. The model simulates the gradual thinning of the ceiling of the underground hall, from the surface downwards, until its collapse. The paper presents a …

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Mechanisms Of Karst Breakdown Formation In The Gypsum Karst Of The Fore-Ural Region, Russia (From Observations In The Kungurskaja Cave), Vjacheslav Andrejchuk, Alexander Klimchouk Jan 2002

Mechanisms Of Karst Breakdown Formation In The Gypsum Karst Of The Fore-Ural Region, Russia (From Observations In The Kungurskaja Cave), Vjacheslav Andrejchuk, Alexander Klimchouk

International Journal of Speleology

The fore-Ural is a classical region of intrastratal gypsum karst. The intensive development of karst in the Permian gypsums and anhydrites causes numerous practical problems, the subsidence hazard being the most severe. Mechanisms of karst breakdown formation were studied in detail in the Kunguskaya Cave area. The cave and its setting are characteristic to the region and, being a site of detalied stationary studies for many years, the cave represents a convenient location for various karst and speleological investigations. Breakdown structures related to cavities of the Kungurskaya Cave type develop by two mechanisms: gravitational (sagging and fall-in of the ceilings …

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Karstology And The Opening Of Caves During Motorway Construction In The Karst Region Of Slovenia, Martin Knez, Tadej Slabe Jan 2002

Karstology And The Opening Of Caves During Motorway Construction In The Karst Region Of Slovenia, Martin Knez, Tadej Slabe

International Journal of Speleology

The nature of karst makes constructing a roadway across karst areas a complex task, which is why karstologists take part in motorway construction across Slovenia’s karst. Working with planners, karstologists select the best route on the basis of preliminary research. Then they carry out regular karstological monitoring of the construction, to study newly discovered karst phenomena, mostly caves, and also help builders overcome the challenges of karst in a way that will preserve nature as much as possible. During the recent construction of a section of motorway, more than three hundred caves were encountered within a sixty-kilometre stretch of road. …

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Collapse Above The World's Largest Potash Mine (Ural, Russia), Vjacheslav Andrejchuk Jan 2002

Collapse Above The World's Largest Potash Mine (Ural, Russia), Vjacheslav Andrejchuk

International Journal of Speleology

This paper reports the results of the study of a huge collapse that occurred in June 1986 within the area of the 3rd Berezniki potash mine (the Verkhnekamsky potash deposit, Ural). Processes that took place between the first appearance of a water inflow through the mine roof and the eventual collapse are reconstructed in detail. The origin and development of a cavity that induced the collapse are revealed. Two factors played a major role in the formation of the collapse: the presence of a tectonic fold/rupture zone with in both the salt sequence and the overburden (the zone of crush …

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Karst Subsidence In South-Central Apulia, Southern Italy, Marco Delle Rose, Mario Parise Jan 2002

Karst Subsidence In South-Central Apulia, Southern Italy, Marco Delle Rose, Mario Parise

International Journal of Speleology

Subsidence in the karst of Apulia (Southern Italy), one of the classical karst areas of Italy, is described in this paper. The carbonate rocks that make up the geological structure of the Apulia region are affected by subsidence, which is of different type and intensity depending upon geological, topographical, and hydrogeological conditions. In particular, we discriminate between inland subsidence and coastal subsidence. Inland subsidence is generally restricted to the presence of individual cavities, either empty or partly or totally filled with deposits produced by dissolution of soluble rocks underground. Locally, such subsidence can cause severe effects on anthropogenic structures above. …

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Karst Breakdown Mechanisms From Observations In The Gypsum Caves Of The Western Ukraine: Implications For Subsidence Hazard Assessment, Alexander Klimchouk, Vjacheslav Andrejchuk Jan 2002

Karst Breakdown Mechanisms From Observations In The Gypsum Caves Of The Western Ukraine: Implications For Subsidence Hazard Assessment, Alexander Klimchouk, Vjacheslav Andrejchuk

International Journal of Speleology

The term karst breakdown is employed in this paper to denote the totality of processes and phenomena of gravitational and/or hydrodynamic destruction of the ceiling of a karst cavity and of the overlying sediments. It refers not only to the existence of a surface subsidence (collapse) feature but, first of all, to the “internal” (hidden in the subsurface) structures that precede development of a surface form. This study reports and discusses the results of direct mapping and examination of breakdown structures in the gypsum karst of the Western Ukraine, at the level of their origin, i.e. in caves. The accessibility …

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Collapse Dolines And Deflector Faults As Indicators Of Karst Flow Corridors, France Šušteršič Jan 2002

Collapse Dolines And Deflector Faults As Indicators Of Karst Flow Corridors, France Šušteršič

International Journal of Speleology

The paper concerns collapse dolines, which appear to be one of the best-defined surface karst phenomena. Despite this appearance, one may find quite different views in the literature, and some of the aspects of their morphogenesis have been overlooked completely. Among these aspects the most obvious is the question of the ongoing development of the closed depression. Five of the most common collapse doline types found in Slovenia are considered in terms of general systems theory, leading to a conclusion that cave roof collapse remains the crucial event in a collapse doline’s development. However, the collapse event itself may be …

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Development Of A Large-Scale Laboratory Facility For Sediment Transport Research, David G. Hamilton, Bruce A. Ebersole, Ernest R. Smith, Ping Wang Sep 2001

Development Of A Large-Scale Laboratory Facility For Sediment Transport Research, David G. Hamilton, Bruce A. Ebersole, Ernest R. Smith, Ping Wang

Geology Faculty Publications

No abstract provided.

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Longshore Sediment Transport As A Function Of Energy Dissipation, Ernest R. Smith, Ping Wang Jan 2001

Longshore Sediment Transport As A Function Of Energy Dissipation, Ernest R. Smith, Ping Wang

Geology Faculty Publications

Experiments to measure waves, currents, and sediment transport rate for two breaker types, plunging and spilling, were conducted in a large-scale three-dimensional physical model. It was found that there was a large difference in cross-shore distribution and total sediment transport rate between the two breaker types. Total transport rates compared to existing predictive equations. The equations generally did not predict the data well. With the exception of the Kamphuis (1991) equation, which included a dependence on wave period, the predictive equations did not differentiate between breaker types.

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Classification Of Terrestrial Subterranean Fauna Of Volcanic Substrates In The Canary Islands, Josè L. Martín, Helga García, Y. P. Oromí Jan 2001

Classification Of Terrestrial Subterranean Fauna Of Volcanic Substrates In The Canary Islands, Josè L. Martín, Helga García, Y. P. Oromí

International Journal of Speleology

A system is proposed for classifying the species occurring in the hypogean environment in relation to their ecological and evolutionary characteristics. The ecological criteria utilized relate to the preferred habitat of the animals (the epigean, endogean or hypogean environment) and the evolutionary criteria specify the grade of adaptive modification in three characteristics: reduction of eyes, amount of pigmentation and extent of elongation of the appendages. The object of developing this classification is to provide a system appropriate for those regions - such as those with volcanic rocks - in which the cave faunas include elements originating in different environments, and …

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Studies On Certain Aspects Of Behaviour In The Blind Catfish Horaglanis Krishnai Menon, T. V. Anna Mercy, N. K. Pillai, N. K. Balasubramanian Jan 2001

Studies On Certain Aspects Of Behaviour In The Blind Catfish Horaglanis Krishnai Menon, T. V. Anna Mercy, N. K. Pillai, N. K. Balasubramanian

International Journal of Speleology

Horaglanis krishnai is a blind catfish inhabiting the dug-out wells at Kottayam, Kerala. This fish has great zoogeographical importance as a similar blind clariid, Uegitglanis zammaroni is found only in the artesian wells of the former Italian Somaliland. Studies on certain behavioural aspects of the fish in captive conditions showed that, this fish even though is blind, exhibited a high degree of thigmotactism. Locomotion, comfort behaviour, feeding and light sensitivity of the fish were studied under laboratory conditions. Though the fish is totally blind and histological study did not reveal the presence of any light sensitive structures, the fish is …

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Deposition Of Calcium Carbonate In Karst Caves: Role Of Bacteria In Stiffe's Cave, Claudia Ercole, Paola Cacchio, Giorgio Cappuccio, Aldo Lepidi Jan 2001

Deposition Of Calcium Carbonate In Karst Caves: Role Of Bacteria In Stiffe's Cave, Claudia Ercole, Paola Cacchio, Giorgio Cappuccio, Aldo Lepidi

International Journal of Speleology

Bacteria make a significant contribution to the accumulation of carbonate in severa! natural habitats where large amounts of carbonates are deposited. However, the role played by microbial communities in speleothem formation (stalactites, stalagmites etc.) in caves is still unclear. In bacteria carbonate is formed by autotrophic pathways, which deplete CO2 from the environment, and by heterotrophic pathways, leading to active or passive precipitation. We isolated cultivable heterotrophic microbial strains, able to induce CaCO3 precipitation in vitro, from samples taken from speleothems in the galleries of Stiffe’s cave, L’Aquila, Italy. We found a large number of bacteria in the …

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Studies On The Cranial Osteology Of The Blind Catfish Horaglanis Krishnai Menon (Pisces, Clariidae), T. V. Anna Mercy, N. Krishna Pillai Jan 2001

Studies On The Cranial Osteology Of The Blind Catfish Horaglanis Krishnai Menon (Pisces, Clariidae), T. V. Anna Mercy, N. Krishna Pillai

International Journal of Speleology

Horaglanis krishnai Menon is a blind catfish inhabiting the dug- out wells at Kottayam, Kerala, South India. Studies on the cranial osteology of the fish show that the bones on the skull are firmly articulated. The frontoparietal fontanella is very large so that the cranium virtually lacks a roof. The sphenotics and alisphenoids are hardly recognizable and the orbital bones are entirely lacking. In osteological features H. krishnai closely resembles Uegitglanis zammaroni. But in H. krishnai the orbital bones are further reduced or even absent. The fontanella is larger than that of any other known catfish. These two species …

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The Distribution Of Plants In Scoska Cave, North Yorkshire, And Their Relationship To Light Intensity, Allan Pentecost, Zhang Zhaohui Jan 2001

The Distribution Of Plants In Scoska Cave, North Yorkshire, And Their Relationship To Light Intensity, Allan Pentecost, Zhang Zhaohui

International Journal of Speleology

The flora of a small limestone cave was investigated. A total of 59 species was recorded (4 algae, 3 lichens, 47 bryophytes, 4 ferns, 1 angiosperm) making it bryologically the richest cave in Britain and one of the richest in Europe. All but nine of the species had been recorded from other European caves. Species-richness declined irregullarly from the entrance (relative irradiance with respect to open sky 12%) to 34m depth (rel. irradiance 0.004%). Bryophytes were found at 0-16m depth where relative irradiance declined to 0.2% and only algae were encountered at 34m depth. While irradiance, which declined exponentially, was …

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Biogenic Speleothems: An Overview, Paolo Forti Jan 2001

Biogenic Speleothems: An Overview, Paolo Forti

International Journal of Speleology

The idea that speleothems may be somehow influenced by living organisms is rather old, but specific studies have only started in the last few decades and presently there are only a couple of systematic papers on this topic. The role of micro-organisms is perhaps the best investigated even if it is not fully understood, while studies over upper organisms and speleothems in a cavern environment are scarce and details are not always given on the involved genetic mechanisms. The aim of the present paper is to give an updated overview on these topics in order to enhance the interest of …

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Comparisons Of Gravity Anomalies At Pseudofaults, Fracture Zones, And Nontransform Discontinuities From Fast To Slow Spreading Areas, Sarah E. Kruse, Sarah F. Tebbens, David F. Naar, Qingyuan Y. Lou, Robert T. Bird Dec 2000

Comparisons Of Gravity Anomalies At Pseudofaults, Fracture Zones, And Nontransform Discontinuities From Fast To Slow Spreading Areas, Sarah E. Kruse, Sarah F. Tebbens, David F. Naar, Qingyuan Y. Lou, Robert T. Bird

Geology Faculty Publications

Published mechanisms for rift tip propagation at spreading centers include extensional deformation and an initial period of slow spreading. We investigate whether the gravity signal and inferred crustal structure at pseudofaults formed in medium to superfast spreading environments resemble the gravity signal at fracture zones or nontransform discontinuities formed in slow spreading environments. We find that altimetry-based gravity anomalies on the Mathematician, Bauer, Easter, Juan Fernandez, and northern Chile Ridge pseudofaults, located in 75–150 mm/yr (full rate) seafloor spreading environments, are similar in amplitude and form to Atlantic fracture zones with 20–30 mm/yr spreading rates. A 5–15 mGal positive mantle …

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Verification Of The Causes Of Glaciations And Sea Level Changes Using The Records Of Calcite Speleothems, Y. Shopov, D. Stoykova, L. Tsankov, M. Sanabria, J. Lundberg, L. Georgiev, P. Forti, D. Georgieva Jan 2000

Verification Of The Causes Of Glaciations And Sea Level Changes Using The Records Of Calcite Speleothems, Y. Shopov, D. Stoykova, L. Tsankov, M. Sanabria, J. Lundberg, L. Georgiev, P. Forti, D. Georgieva

International Journal of Speleology

The luminescence of calcite speleothems displays an exponential dependence on soil temperature unless there is a dense cover of forest over the cave to dampen it. This relationship is determined primarily by the strength of solar visible and infrared radiation. It is suggested that, as a consequence, the microzonal variations of luminescence often found in speleothems can be used as a proxy index of Solar Insolation. The luminescence solar insolation proxy record of a speleothem from Jewel Cave, South Dakota, USA, was found to display millenial and centennial cycles in the record. It exhibits a rapid increase in solar insolation …

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Révision De Quelques Hypothèses Sur Le Creusement Karstique, Jacques Choppy Jan 2000

Révision De Quelques Hypothèses Sur Le Creusement Karstique, Jacques Choppy

International Journal of Speleology

Quite often, as we know better karst phenomena and the evolution of the karst environment, several hypotheses on speleogenesis appeared to be flimsy. Some of these hypotheses, concerning processes playing a part in the creation of karst forms, exceed the limits of their field. Others suggest hydraulic mechanisms, and interventions of geological or geographical factors likely to be questioned. Hypotheses relating to the evolution of karst, as well as the classification of karst types, suffer from the lack of an analytical approach. However, some of these hypotheses still have an important place in the current vision of speleologists and karstologists.

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Is It Always Dark In Caves?, Giovanni Badino Jan 2000

Is It Always Dark In Caves?, Giovanni Badino

International Journal of Speleology

Underground natural sources of visible light are considered. The main light producer is Cerenkov radiation emitted in air, water and rock by cosmic ray muons, that depends, in a complex way, on shape of mountain and of caves. In general the illumination increases linearly with the cavity dimensions. Other light sources are from secondary processes generated by radioactive decays in rock from minerals luminescence. The natural light fluxes in caves are in general easy to detect but are not used from underground life.

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