Rock Boulders Research Articles

A rheological model for the description of boulder impacts on granular strata

This paper considers the mechanics of rock boulders impacting on granular strata. The study is aimed at improving the numerical methods devoted both to describing boulder trajectories along slopes and designing preventive structures in mountain regions. The problem is analysed by using a simplified approach inspired by the lumped mass method. This is based on (a) the macro-element concept, (b) the definition of generalised stresses and displacements, and (c) delayed plasticity theory. Both vertical and inclined impacts on horizontal strata and vertical impacts on inclined slopes are discussed. The numerical results are obtained by using a finite difference numerical discretisation to integrate, over time, a coupled system of two-dimensional differential equations. Most of the input data requested by the model are basic and geotechnically meaningful, and comparison of the numerical results with the experimental data seems to be quite promising.

A rheological model for the description of boulder impacts on granular strata

This paper considers the mechanics of rock boulders impacting on granular strata. The study is aimed at improving the numerical methods devoted both to describing boulder trajectories along slopes and designing preventive structures in mountain regions. The problem is analysed by using a simplified approach inspired by the lumped mass method. This is based on (a) the macro-element concept, (b) the definition of generalised stresses and displacements, and (c) delayed plasticity theory. Both vertical and inclined impacts on horizontal strata and vertical impacts on inclined slopes are discussed. The numerical results are obtained by using a finite difference numerical discretisation to integrate, over time, a coupled system of two-dimensional differential equations. Most of the input data requested by the model are basic and geotechnically meaningful, and comparison of the numerical results with the experimental data seems to be quite promising.

Centrifuge scaling laws for guided free fall events including rockfalls

Concrete protection galleries are generally used in mountainous regions to protect the local infrastructure and lifelines against potential impacts from rock boulders. These can be protected further by carefully designed cushion systems, most of which rely on granular geomaterials. Rockfall impact energies can reach magnitudes of the order of millions of Joules, requiring understanding of the combined energy absorption mechanisms at high energy levels for improved design of the gallery and cushion. These prototype high-energy ranges can be achieved at the laboratory scale with the help of a geotechnical centrifuge. The model is rotated under high g levels, thereby increasing the unit weight of the material. Prototype energy levels can be represented in a small scale model with consideration of appropriate scaling laws, and although free fall events in a centrifuge experience components of the Coriolis acceleration, projectiles (boulders) will move out of the centripetal gravity field when losing contact with the rotational field. A guiding tube is used in this case to keep the boulder in the acceleration field (ng) in order to achieve sufficient input energy levels to represent existing design criteria. The change in the g-level during the fall of the boulder in the centrifuge, due to the change in the radius, has to be taken into account for determination of the impact energy. In this case, direct application of traditional scaling laws for centrifuge modelling is invalid. This paper focuses on the determination of the change in the g field with time during the fall of the boulder to estimate the g level at the time of impact and this value is used in the calculation of the prototype energy levels. A summary of the performance of various cushion materials is given.

Fish assemblages of Cais do Carvão Bay (Madeira Island) determined by the visual census technique

Fish assemblages in Cais do Carvão Bay, Madeira Island, a proposed marine protected area (MPA), were determined from a diver visual census. A total of 32 transect counts were performed. Habitats sampled included sandy bottom, rocky boulders, vertical walls and rocky outcrops. Species richness, diversity, density, trophic structure, size and spatial organization were documented for the fish assemblages. Forty‐four species from 23 families were encountered; 32% belonged to Sparidae (10) and Labridae (four). The greatest species richness (25) was observed in rocky boulder habitat at 10–15 m depth, while the lowest (five) occurred over a deeper sand habitat. The greatest density (760·5 individuals per 100 m2) was recorded over rocky outcropping (20–25 m deep), and the lowest of 11·6 individuals per 100 m2 was over a sand bottom at 10–15 m depth. Thalassoma pavo, Abudefduf luridus and Chromis limbata had higher densities on hard bottoms, while Heteroconger longissimus was the most abundant species in sand bottom habitats. No significant differences were detected for all indices calculated among depth intervals for sand and rocky boulder stations. Sand and rock boulder substratum, however, differed significantly for the 10–15 m depth stratum.

Impact of rocks onto gravel Design and evaluation of experiments

Layers of gravel represent an energy-absorbing system for structures subjected to rockfall. To support the design of such structures, relations between the penetration depth, the impact duration, and the impact force, respectively, and the rock boulder mass, the height of fall, and the indentation resistance of the gravel are presented. Knowledge about projectiles impacting onto concrete and soil is incorporated in these relations. They can be simplified by dimensional analysis. This is the basis for the design of rockfall experiments comprising heights of fall up to 20 m , and a rock boulder mass up to 20 000 kg . From these experiments, the indentation resistance of gravel is obtained by back-analysis and evaluated statistically. This permits estimation of penetration depths caused by rockfall events which are beyond the experimental means of the current study. Finally, a model for the impact kinematics is deduced from experimental acceleration measurements. It yields design diagrams for impact duration and impact forces, supporting probability-based engineering design of rockfall protection systems with gravel as an energy-absorbing component.

Moult habitat, pre- and post-moult diet and post-moult travel of Ross Sea emperor penguins

MEPS Marine Ecology Progress Series Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections MEPS 267:281-290 (2004) - doi:10.3354/meps267281 Moult habitat, pre- and post-moult diet and post-moult travel of Ross Sea emperor penguins G. L. Kooyman1,*, D. B. Siniff2, I. Stirling3, J. L. Bengtson4 1Scholander Hall, Scripps Institution of Oceanography, La Jolla, California 92014-0204, USA 2Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota 55108, USA 3Canadian Wildlife Service, 5320 122 St., Edmonton, Alberta T6H 3S5, Canada 4National Marine Mammal Laboratory, Alaska Fisheries Science Center, NOAA, 7600 Sand Point Way NE, Seattle, Washington 98115, USA *Email: gkooyman@ucsd.edu ABSTRACT: During a series of transect legs through the pack ice of the eastern Ross Sea, aboard the RV icebreaker ŒNathaniel B. Palmer¹, we: (1) assessed the habitat chosen for moulting by emperor penguins, Aptenodytes forsteri, (2) determined their pre- and post-moult diets, (3) measured the pre- and post-moult body mass of the birds, and (4) tracked their post-moult movements. Diet was based on the colour of guano near the edges of ice floes and fast-ice areas. Pre- and post-moult birds were weighed at locations along the transect. Satellite transmitters were attached to 7 birds, and tracked for up to 5 mo. Birds moulted in concentrated pack ice and coastal fast ice. Offshore from the shelf slope, diet was mostly Antarctic krill Euphausia superba. Over the shelf, the diet was mainly fish and squid. Body masses of birds immediately after the moult were often less than 20 kg. After moult, satellite tracked birds remained in the pack ice but moved to the west at a rate of 13 to 41 km d-1. One bird traveled to the Cape Roget colony, where it arrived on 15 April after 70 d and 2140 km of travel. We conclude that (1) birds are close to starvation by the end of the moult, (2) it is essential that an abundant food supply is in close proximity to the moult area, (3) penguins travel more than 2000 km on the return journey to their colonies of the western Ross Sea, and (4) reduction in the extent and seasonal duration of the pack ice would be reflected in a rapid change in the size of the breeding population of coastal west Antarctica. KEY WORDS: Satellite transmitter · Eastern Ross Sea · Antarctica · Pack ice · Krill · Body mass · Emperor penguin Full text in pdf format PreviousNextExport citation RSS - Facebook - Tweet - linkedIn Cited by Published in MEPS Vol. 267. Online publication date: February 19, 2004 Print ISSN: 0171-8630; Online ISSN: 1616-1599 Copyright © 2004 Inter-Research.

The Stones Shall Cry Out: Consciousness, Rocks, and Indians

The Stones Shall Cry Out:Consciousness, Rocks, and Indians George “Tink” Tinker (bio) Did you know that trees talk? Well they do. They talk to each other, and they'll talk to you if you listen. Trouble is, white people don't listen. They never learned to listen to the Indians, so I don't I suppose they'll listen to other voices in nature. But I have learned a lot from trees; sometimes about the weather, sometimes about animals, sometimes about the Great Spirit.1 When we talk with non-Indians about nature, there is really nothing you can say in universal Western concepts that is going to make a lot of sense. I think that Western people who come into an Indian environment and attempt to preach take along their own set of categories and use it to deal with Indian people they meet. Anthropologists, summarizing what they find in the Indian tradition, always calling us animists, and that view is accepted by a great many people in the field of religion. We are put in a cultural evolutionary framework, and then we are supposed to move from animism to some great abstract conception of one god.2 Science describes things at a level of abstraction, by leaving out of account a whole range of properties that they have (colour, beauty, consciousness...). This is for many [End Page 105] purposes a very useful procedure, but it does not follow that the properties with which science concerns itself are more real than those it leaves out.3 Did you know that rocks talk? Well, they do. Yes, I am aware that this is an audacious claim—even for an American Indian—made in the context of late modernity (or even postmodernity, if you insist) and in the context of a world indelibly marked by the accomplishments of modern science. But the argument proposed for this essay is that rocks talk and have what we must call consciousness. And we must extend our discussion of rocks to trees—as Walking Buffalo asserts in the quote above—and to the rest of the created world around us. I want to open an exploration of the particular disjunction between the worldviews of American Indian and Euro-Western cultures with regard to Western scientific, religious, and commonsense knowledges. The Western world, long rooted in the evidential objectivity of science, distinguishes at least popularly between things that are alive and things that are inert, between the animate and the inanimate. Among those things that are alive, in turn, there is a consistent distinguishing between plants and animals and between human consciousness and the rest of existence in the world. To the contrary, American Indian peoples understand that all life forms not only have consciousness, but also have qualities that are either poorly developed or entirely lacking in humans.4 Curiously enough, while Western philosophy asserts universally that human beings have consciousness, there is currently no agreement whatsoever as to what that consciousness is and whether its qualities are to be identified through a process of scientific study (neurology, psychology, and so on) or through philosophical or theological reflection. Yet Western culture, the emergent world culture (in Immanuel Wallerstein's useful parlance)5 of globalized capital and Western science, is equally sure that rocks certainly do not have consciousness. What, then, is the nature of these contrasting epistemological claims? Is the Indian worldview "merely" religious—with no value in fact?6 Is the Euro-Western scientific worldview a perception of reality that is equally a "mythological" system? Or is it to be understood as a singular truth-value that is incontrovertible? Allow me to begin with a personal reminiscence from the summer of 1986. Rocks The Kanukamaoli artist was describing how he found the large rock boulders that he sculpted so beautifully into images of Kanukamaoli deity figures. These sculptures, the artist was quick to note, were never [End Page 106] for sale and hence were not the source of his sustenance. Speaking to a diverse group of U.S. academics and Pacific Rim artists and scholars gathered at the East-West Center at the University of Hawaii, the man responded to a question by...

Movement patterns, home range, and habitat utilization of adult kelp bass Paralabrax clathratus in a temperate no-take marine reserve

Home range, activity patterns, site fidelity and habitat preference of the kelp bass Para- labrax clathratus were determined from 12 adult fish tracked using acoustic telemetry within a tem- perate no-take marine reserve (0.13 km 2 ). Home range sizes ranged from 33 to 11 224 m 2 , averaging 3349 ± 3328 m 2 (±SD), but did not correlate with fish size. Fish were active and occupied similar-sized activity spaces during both day and night. Kelp bass exhibited a high degree of site fidelity, remain- ing resident in core areas for up to 3 yr. Relative to the total amount of available habitat, kelp bass showed a habitat selection preference for rock boulder, rock rubble and kelp habitat. These habitats offer high vertical relief, shade and large holes for shelter, and may attract and facilitate prey capture. Average home range size was 3% of the area of the reserve. Only 1 of 12 tracked fish crossed the reserve boundary, but this accounted for less than 5% of the fish's time. Natural habitat breaks along the reserve boundary may have further limited adult kelp bass movements. The small home ranges and high site fidelity of kelp bass in this reserve indicate that the reserve is effective in protecting the resident adult stock.

The Use of Rockfall Protection Systems in Surface Mining Activity

In many cases open pits in mountainous areas are subjected to the collapse of rock boulders (rockfall), which can reach the quarry area and create safety hazards for both personnel and mine infrastructure. The paper demonstrates that net fences widely used for control and risk mitigation of rockfall in civil and road constructions, can be used successfully also for mining activities, with special reference to ornamental stone quarries. A description of this protection technique and the design key points are highlighted and discussed.

Food of emperor penguins ( Aptenodytes forsteri ) in the western Ross Sea, Antarctica

The diet of the emperor penguin Aptenodytes forsteri in the western Ross Sea during spring was investigated by analysis of stomach contents sampled at three different localities. At Cape Washington, emperor penguins feeding chicks consistently preyed on fishes (89 to 95% by mass) and crustaceans (5 to 11%) over the four spring seasons examined. By far the commonest prey was the Antarctic silverfish Pleuragramma antarcticum (89% of the fish prey); the remainder of fish prey were mainly unidentified juveniles of different species of channichthyid fishes. Three species dominated the crustacean part of the diet, i.e. the gammarid amphipods Abyssorchomene rossi/plebs (30% of the crustacean prey) and Eusirus microps (22%), together with the euphausiid Euphausia crystallorophias (24%). At Coulman Island and Cape Roget, fishes, mainly P. antarcticum, formed the bulk of the food (88 and 93% by mass, respectively), crustaceans were minor prey (2.5 and 0.4%), and the squid Psychroteuthis glacialis accounted for a small but significant part of the food (3.5 and 0.8%). This study emphasizes the importance of the small, shoaling pelagic fish Pleuragramma antarcticum as a key link between zooplankton and top predators, including seabirds, in the food web and marine ecosystem of the Ross Sea.

Extremely high-energy wave deposits inside the Great Barrier Reef, Australia: determining the cause—tsunami or tropical cyclone

A hydrodynamic approach is used to determine whether tsunami- or cyclone-generated waves were responsible for the deposition of fields of well-imbricated rock boulders (up to 290 tonnes) along the coast of Cairns inside the Great Barrier Reef, Australia. Calculations of the overturning moments show that only tsunami are capable of moving such large boulders in this environment. It is hypothesised that large tsunami (> 11 m) have been able to penetrate the Great Barrier Reef through wide (5–10 km) 50–70 m deep passages between individual reefs. Three such passages each approximately 35 km apart and oriented in the same direction exist in the Cairns region. It is possible that these passages have funnelled and amplified palaeotsunamis. The preferential location of eroded coral boulders up to 3 m in length on reef flats alongside these passages and their absence on other reefs throughout the region provide further evidence that extremely high-energy waves have been able to penetrate the Great Barrier Reef into the inner channel adjacent to the mainland. Carbon-14 ages of the coral boulders on these reef flats matches closely the ages of coral fragments pinned below the very large rock boulders along the coast. These ages suggest that the Cairns region has experienced large tsunami twice over the last millennium.

Analysis of symmetric contact charge action in breaking rock boulders : Wei Wu Min Sci TechnolV13, N3, Dec 1991, P439–444

Analysis of symmetric contact charge action in breaking rock boulders : Wei Wu Min Sci TechnolV13, N3, Dec 1991, P439–444

Analysis of symmetric contact charge action in breaking rock boulders

A new method is proposed for more effective breakage of rock boulders during secondary blasting. It is suggested that by placing two contact charges at symmetrical locations on a boulder's surface, one can take advantage of stress wave interaction within the block and, especially, the superposition of reflected tensile waves from the free boundary of the boulder. Theoretical calculations based on elastodynamics and dynamic photoelastic experiments showed the existence of stress concentration within a finite block under symmetric loading conditions, which could lead to spliting of the block along loading points. Blasting tests on mortar models of various shapes further confirmed the possibility of rock boulder fracture by this method.

Structural safety of an ocean outfall against hurricane damage

Ocean outfall pipelines, made of cast iron with concrete coating, are used to carry secondary-treated effluent which has almost the same density as freshwater. The pipelines, which are laid in trenches backfilled with sand and rock boulders, are often insufficiently protected in the event of a major storm. This paper presents a study on the prediction of the wave/wave-induced hydrodynamic forces and erosion that would result from a hurricane, and evaluates the potential for damage to the structure due to a Category 4 hurricane, i.e. a hurricane (measured on a scale of 1–5) with a wind velocity between 131 and 155 m.p.h. and storm surges of 13–18 ft above normal, which may lead to major beach erosion. The investigation includes liquefaction analysis, evaluation of scour due to wave breaking, vertical and horizontal stability analyses, and recommendations for a concrete flexible revetment scour protection system. Both fully exposed and partially buried pipelines are considered in the stability analysis. A detailed discussion of the main elements of a scour protection system, including the revetment underlayer, cellular units, tendons, and pin anchors is presented, with typical illustrations. Further study is needed to include possible pipeline breakout from the seafloor which results from fluctuating lift forces caused by an induced gap at the pipe-soil interface.

Nest Site Selection in Zenaida Dove (Zenaida aurita) in Puerto Rico

Nest Site Selection in Zenaida Dove (Zenaida aurita) in Puerto Rico

The Prehistoric Rock Art of Great Britain: A Survey of All Sites Bearing Motifs more Complex than Simple Cup-marks

The prehistoric rock art of Great Britain — England, Scotland and Wales — is surveyed, with specific reference to the over 900 sites bearing motifs more complex than cup-marks alone and apparently random grooves. Of sites bearing cup-marks alone, there are at least 700.The majority of motifs is geometric, with a few animals, weapons and human hands and footprints. Two main groups are recognized, the Boyne or Passage Grave type and the Galician type. The former occurs mainly on the slabs of Neolithic tombs, especially in Ireland, and includes spirals, rings, lozenges, zigzags and flower-like figures, only some of which occur in Britain. The latter is more restricted in design, with mainly cup-and-rings, rings, and spirals, usually on rock outcrops and boulders. A third group is recognized by some workers, in which cist and burial stones are carved with mostly the Boyne type, but sometimes with Galician or simple cup-marks or a mixture of these. There is also occasional overlap between Galician and Boyne types, occurring on natural rocks and tombs.The main characteristics, locations in relation to topography and archaeology, and distribution are detailed. Dating and significance are briefly discussed.Most of the art occurs in a central belt of Britain, but within that it is recognized as being distributed spatially among 16 main regions which are defined both geographically and with regard to concentrations of sites.There is a gazetteer of all sites, similarly arranged.

Winter Behavior of the Granite Spiny Lizard, Sceloporus orcutti Stejneger

During the winter as many as 37 Sceloporus orcutti were found together in rock crevices in western Riverside County, California. First-year animals were located close to the surface of the rock while older animals were found deep within rock boulders. Temperature fluctuations within a deep crevice were 2? C during a winter day, while a crevice containing only young animals experienced a change of 16? C. Rising crevice temperatures in late winter seemed to be a major cue for emergence. Many adult lizards occupied a specific crevice in consecutive winters which was outside the normal spring-summer home range. Home ranges were re-established shortly after the lizards emerged. This migration pattern to and from the winter crevices was well established by the time a lizard was three years old as a result of changes in home range localities, changes in crevice requirements, and memory of the location of past wintering areas.

Bathyscaph Observations in the La Jolla Submarine Fan Valley: ABSTRACT

Observations, made from the bathyscaph Trieste during six dives to depths ranging from 1,800 to 3,000 feet, reveal that submarine erosion is actively modifying a series of step-like terraces forming the internal walls of the La Jolla Submarine Fan Valley. The innermost terrace is cut by a narrow, steep-walled, flat bottomed channel that forms the longitudinal axis of the valley. Beneath a thin mud cover, the channel contains sand and plant fill that is entirely different from that found on or forming the internal terraces. The steep slopes (up to 70 degrees), found where the innermost terraces lead down to the inner channel, have slump scars, striations, and fresh burrows that indicate they are presently being eroded by marine processes. Terrace sediments are bedded and s mi-consolidated and do not appear to have been deposited in the present erosional environment of the canyon. On one of the dives, large rounded rock boulders, up to 3 feet in diameter, were found scattered through the interbedded sand, mud, and plant material found in the inner channel. The nearest possible source for these large erratics is more than one-fourth of a mile from their present location. The following characteristics are arguments against dense, high-velocity turbidity currents as agents of erosion or transportation in the present day La Jolla Fan Valley: (1) the lack of scour depressions around large man-made objects found in the sands of the inner channel, (2) the sinuous course of the inner channel, (3) a low axial gradient, (4) a lack of inner channel sediment on terraces 10 feet above the channel bottom, and (5) the heterogeneous mixture of fragile sea-grass mats, large boulders, and micaceous sands. Pulsating bottom currents with velocities up to 0.45 knots have been measured. These currents were observed to have sufficient strength to transport fine micaceous sand and unconsolidated clay-sized particles along the bottom of the inner channel. However, the large boulders associated with sands and organic debris, foreign to the surrounding sea floor, must have been transported by another mechanism; gravity creep and progressive slumping of the entire fill of the erosion channel are suggested agents. End_of_Article - Last_Page 338------------

The discovery of multiple rock gongs in Nigeria

The first recorded discovery of ringing rocks used for the production of musical notes was made at Birnin Kudu in Kano Emirate (9'30"E., 11 'N.) in June, 1955, during field investigations of the recently discovered rock paintings, the first to be found in Nigeria. The term ‘rock gong’ is here used to denote the small percentage of the numerous natural rock boulders, slabs, spalls and exfoliations abounding in the rocky hills of Nigeria which vibrate with a ringing tone when struck and which also show indisputable evidence of having been used as percussion instruments.

Sediments of the Submarine Canyons Off the California Coast

ABSTRACT The sediments in the numerous submarine canyons off the California coast may be characterized as sand, mostly find sand, with an abundance of silt and some clay. They are in general very well sorted. Rock fragments and boulders have been dredged from many canyons. Bed rock crops out on the sides of Monterey, Carmel, and Scripps canyons.The median grain sizes in the canyons are slightly lower than on the adjacent parts of the shelf. There are variations in median grain sizes in the canyons but there is not always a decrease in median grain size with increasing depth. Short cores from Fire Hill canyon showed no stratification of the sediments. Heavy minerals make up only a very small part of the sediments. Authigenic minerals and organic material are common in the deeper portions of the canyons. The calcium carbonate content increases with depth due to the increase in abundance of organisms.