Small Rocks Research Articles

Beijing's South China Sea Debate

The three million square kilometres of the South China Sea are of particular strategic importance. Sovereignty over a plethora of small islands, atolls, rocks and coral reefs, including the two mai...

Resource selection of lithic raw materials in the Middle Palaeolithic in southern France

The work reported here uses several approaches to examine the costs and benefits associated with exploiting potential sources of lithic raw material in the Vaucluse, southern France, and then tests the results against the proportions of raw materials from various sources found in the lithic assemblage of a Middle Palaeolithic site, the Bau de l’Aubesier. A previously published equation designed to quantify the attractiveness of each source proves to be significantly correlated with source use, but the results show that it can be improved. We then individually test the components of the attractiveness equation (raw material quality, source extent, terrain difficulty, and the size and abundance of raw material pieces at the source) and additional variables (Calories expended to get from the source to the site using a straight-line route, Calories expended using a least-cost path, surface distance of the source from the site, and distance to the closest used source) using generalized linear models. Since very similar raw materials can be found at more than one source, we combine such similar sources into source areas, and test the area of the source area (AOSA) and the total area of sources within the source area (AOSISA), as two additional independent variables. The best model shows that raw material quality, source extent, abundance of large and very large rocks, and AOSISA, are positively correlated with use of sources, while terrain difficulty, abundance of small and medium rocks, Calories, and AOSA, are negatively correlated with source use. This shows that the hominins at the Bau de l’Aubesier optimized their raw material procurement to get the most good quality material that they could, while minimizing the time and energy spent getting and using it.

Landmark learning by the Ozark zigzag salamander Plethodon angusticlavius

Abstract Although salamanders have been shown to respond to classical conditioning, spatial learning has been largely unstudied. We tested whether salamanders could learn to locate foraging areas by using landmarks. We trained 10 salamanders Plethodon angusticlavius to use landmarks (small rocks) to locate patches within the arena containing food (blackworms Lum-briculus variegatus). At the corners of each square testing arena were four plastic dishes, one containing blackworms and the other three empty. A rock was placed in front of the dish containing blackworms, and the location of the food-dish was randomly chosen for each training trial. A control group was also trained to feed on blackworms in the presence of a rock, but the rock was positioned randomly among the four dish locations so that the rock was not a reliable landmark for the worms. Although the length of the training period for individual salamanders varied (22–38 trainings per individual), the mean number of trainings for salamanders in the control and experimental groups was equal (30 training trials). During testing, no blackworms were present to eliminate any visual or chemical cues emanating directly from the prey. Individuals trained with the rock landmarks spent significantly more time in the area of the landmark than did control salamanders.

Hilltopping behavior by males of Tachysphex menkei Pulawski (Hymenoptera, Crabronidae)

Males of the little known crabronid wasp Tachysphex menkei Pulawski engage in hilltopping behavior at the peak of Usery Mountain in central Arizona. Males are active at midday in the late spring at this location. Individuals perch on and launch out and back flights from small rocks near prominent plants growing at the highest parts of the undulating ridgeline that makes up the peak. The same set of sites attracted two generations of males (in 2009 and 2010). If site-faithful males are territorial, resident males (those that returned to their perches over at least two days) should be larger on average than the males that replace them after the residents have been removed. This expectation was met. In keeping with the hypothesis that hilltopping is a mating system of last resort, only a few males were seen on any given day and no females were observed, suggesting that the population of the species is small and dispersed, at least in central Arizona.

Perspectives for Systematic Landslide Monitoring

For most geologists, monitoring conjures up actions involving field measurements and data analysis. This is consistent with the definitions of monitoring, which include: “to keep track of systematically with a view to collecting information” and “to test or sample, especially on a regular or ongoing basis” (Dictionary.com, 2010). A major rockslide in Tennessee illustrates the basics of monitoring as applied to landslides. On November 10, 2009, a small mass of rock from an outcrop near mile marker 17.6 on U.S. Highway 64 slid onto the road (News.tennesseeanytime.org, 2009). This early morning rockslide impeded movement from one side of mountainous Polk County to the other. Consequently, Tennessee Department of Transportation (TDOT) maintenance forces quickly reached the site and began clearing rocks blocking the inside (westbound) lane. Among the TDOT employees dispatched to the scene was a geologist, who began observations of the rocks exposed above the work area. The geologist, Vanessa Bateman, noted popping and cracking noises as well as more small rocks rolling down slope (Sohn, 2009). About 12:30 p.m., she alerted personnel on site to the possibility of another rockslide. All personnel and equipment were moved a safe distance away prior to the second, and much larger, rockslide occurring at 1:00 p.m. (Figure 1) (News.tennesseeanytime.org, 2009). Figure 1. The November 10, 2009, rockslide blocking U.S. Highway 64 in Polk County, TN. Just prior to the rockslide, an excavator equipped with an impact hammer was breaking up one of the larger boulders that had slid earlier onto the inside lane. (Photo from Tennessee DOT website.) The timely conclusion that another rockslide was imminent was based on monitoring. The observations were sounds and small rocks rolling during the observational period. The data were collected by the ability of the observer to hear and see. The data were analyzed based …

The Need for High-Fidelity Robotics Sensor Models

Simulations provide a safe, controlled setting for testing and are therefore ideal for rapidly developing and testing autonomous mobile robot behaviors. However, algorithms for mobile robots are notorious for transitioning poorly from simulations to fielded platforms. The difficulty can in part be attributed to the use of simplistic sensor models that do not recreate important phenomena that affect autonomous navigation. The differences between the output of simple sensor models and true sensors are highlighted using results from a field test exercise with the National Robotics Engineering Center's Crusher vehicle. The Crusher was manually driven through an area consisting of a mix of small vegetation, rocks, and hay bales. LIDAR sensor data was collected along the path traveled and used to construct a model of the area. LIDAR data were simulated using a simple point-intersection model for a second, independent path. Cost maps were generated by the Crusher autonomy system using both the real-world and simulated sensor data. The comparison of these cost maps shows consistencies on most solid, large geometry surfaces such as the ground, but discrepancies around vegetation indicate that higher fidelity models are required to truly capture the complex interactions of the sensors with complex objects.

Shell Injuries in Two Intertidal Gastropods Littorina scabra (Linnaeus, 1758) and Thais bufo (Lamarck, 1845) From Tranquebar, Southeast Coast of India

Littorina scabra and Thais bufo were collected from the rocky shore of Tranquebar and the shell injury due to predation or wave action was estimated in both male and female snails. In both the cases, the results show that the shell injury is not depending on shell size but mainly on their exposure to continuous wave action. The physical damage caused to them due to the rolling of small rocks, boulders and the risk of predation was mainly from crabs and birds. In the present study a survey has been made to estimate the percentage of shell injury in male and female snails and different size groups of the above two different species. Obviously there is a relationship between crabs, stones and shell damage. In L. scabra the shell damage in male and female was 47.18% and 41.1% and the size group of 16.10mm to 18.10mm is dominant with 28.44%of shell injury. Whereas in T. bufo it was 50.81% in male and 44.44% in female and the size group of 40.01mm to 48.10mm is dominant with 21.22% of shell injury respectively. The male and female of both the species for the length and width of shell damage were positively correlated. Anova for within the species in shell damage in L. scabra didn’t show variation but for T. bufo it showed variation. Anova for between the species showed significant variation. Among these the female in L. scabra and male in T. bufo showed a maximum injury .This may be able to asses the threat to organisms and shows the level of predation and the damage caused by environmental factors.

Atom & cosmos: Close encounter fascinates media: Small space rocks often pass within radius of moon's orbit

Atom & cosmos: Close encounter fascinates media: Small space rocks often pass within radius of moon's orbit

Status of harbour seals (<i>Phoca vitulina</i>) in Atlantic Canada

Harbour seals are associated with small islets, reefs and rocks exposed at low tide and estuarine habitats throughout eastern Canada. Evidence of harvesting by indigenous people has been found in pre-European contact archaeological excavations. A bounty harvest as well as subsistence and commercial hunting probably lead to a decline in the population from 1949 to the early 1970s. The bounty was removed in 1976, and harbour seals, in the southern parts of their range have been protected since then. There is little information available on total abundance and current population trend. Mitochondrial and microsatellite DNA research has shown separation between Northeast and Northwest Atlantic harbour seals. Within Canada, the subspecies Phoca vitulina concolor shows some population sub-structure with three distinct units that could be separated into Hudson Bay, Gulf of St. Lawrence and Sable Island. Urban development resulting in habitat degradation is probably the most important factor affecting harbour seal populations in AtlanticCanada, although other factors such as incidental catches in commercial fisheries and competition with grey seals may also be important.

Why Are So Many Things in the Solar System Round?

Several years ago a student asked why so many things in the solar system were round. He noted that many objects in the solar system, although not all, are round. The standard answer, which he knew, is that the mutual gravitational attraction of the molecules pulls them into the shape that gets them as close to each other as possible: a sphere. This argument works fine for fluid bodies such as the Sun or Jupiter, but it isn't so simple for a solid object—we have all seen rocks that are not round. There is still a gravitational attraction acting between the rock's molecules, butfor small rocks that force does not overcome the strength of the bonds holding those molecules in their relative positions. Since the strength of the gravitational force grows with the size of the object, a large enough rock will have a strong enough gravitational attraction to force a deformation into a round shape. But how large is that? A simple model gives an answer to this question. There is also renewed interest in this topic as a result of the new definition of a planet approved by the International Astronomical Union, which says in part, “A ‘planet’ is a celestial body that… has sufficient mass for its self-gravity to overcome rigid body forces so that it assumes a hydrostatic equilibrium (nearly round) shape.”1 What size object is large enough to satisfy this criterion? Where does Pluto fall regarding this question?

Who Clears Your Road?

Our house is about five miles from the nearest grocery store. The first four and a half miles are along country roads, and on a typical drive we see more wild animals than cars and trucks. Deer, turkey, skunks, possums, squirrels, mink, raccoons, muskrats, rabbits and buzzards are common. Unfortunately, many of these animals are not well trained in traffic avoidance and the bodies strewn along the side of the road demonstrate the abundance of wildlife in the fields and forests. When the animal is large, someone will stop to remove the carcass from the highway. Similar clean up is required when a tree falls onto the road or large rocks slides from a hill side. I’ve seen strangers cooperate to drag a dead deer from the road or debris from the street. I’ve seen large logs cut using personally owned chain saws and the log sections or rocks loaded into trucks and hauled to the dump. When the road is blocked, groups of individuals cooperate to become ‘‘a road clearing community’’ but when a small animal dies along the roadway, the cleaning is left for the buzzards. The pathway to success occasionally passes through remote sections of highway that contain a variety of animals, trees and large rocks that, on occasions, may become obstacles in the path. Some of the obstacles are too insignificant to damage our vehicle thus we pay little attention to the animal, the stick or other small debris in the road. We drive over the dead squirrel, mink or chipmunk. We leave sticks in the road and small rocks along our career path. One of the fundamental causes of failure is defects in materials. By driving over and ignoring the minor obstacles we begin to accept small defects that can become initiation sites for fatigue cracks, pot holes or other career limiting problems. The small obstacles may include procrastination, rushing to a conclusion and failure to discuss the assumptions associated with a recommendation. We generally try to avoid the larger obstacles, especially the skunks, and may even swerve to avoid hitting them even when they are dead. The skunks and other medium sized animals that lie along the failure analysis highway include prejudging the results, reporting only the data that support an early, client pleasing conclusion and failure to recognize when the required analyses lie outside our areas of expertise. Left unattended, the dead skunks along our highways attract buzzards and other unattractive clients who are reaching for a specific conclusion rather than for the truth. Encounters with large animals, big trees and boulders are easy to recognize, but unfortunately, are often hard to avoid and may need immediate attention. These encounters can damage our vehicles, require effort to repair and minimize our progress along the highway. Reaching the wrong conclusion, providing an inadequate report and giving a poor deposition are large animals that many of us have encountered. These encounters should lead to self examination, improved work habits and an increased tendency to discuss our work with other experts in the field. I’ve seen very confident drivers in very expensive cars, cars that had all the bells and whistles, encounter a deer primarily because the grass beside the highway was too high and hid the deer from view until it stepped directly in front of the vehicle. Brakes squeal, tires skid, glass shatters and fenders and doors need to be replaced. The driver reacted as best he could but... The faster you drive along the highway the harder it becomes to avoid the large animal encounter. It is harder to stop for a fallen tree when M. R. Louthan (&) Box 623, Radford, VA 24142, USA e-mail: macfran61louthan@yahoo.com

Have protoplanetary discs formed planets?

It has recently been noted that many discs around T Tauri stars appear to comprise only a few Jupiter-masses of gas and dust. Using millimetre surveys of discs within six local star-formation regions, we confirm this result, and find that only a few percent of young stars have enough circumstellar material to build gas giant planets, in standard core accretion models. Since the frequency of observed exo-planets is greater than this, there is a `missing mass' problem. As alternatives to simply adjusting the conversion of dust-flux to disc mass, we investigate three other classes of solution. Migration of planets could hypothetically sweep up the disc mass reservoir more efficiently, but trends in multi-planet systems do not support such a model, and theoretical models suggest that the gas accretion timescale is too short for migration to sweep the disc. Enhanced inner-disc mass reservoirs are possible, agreeing with predictions of disc evolution through self-gravity, but not adding to millimetre dust-flux as the inner disc is optically thick. Finally, the incidence of massive discs is shown to be higher at the {\it proto}stellar stages, Classes 0 and I, where discs substantial enough to form planets via core accretion are abundant enough to match the frequency of exo-planets. Gravitational instability may also operate in the Class 0 epoch, where half the objects have potentially unstable discs of $\ga$30 % of the stellar mass. However, recent calculations indicate that forming gas giants inside 50 AU by instability is unlikely, even in such massive discs. Overall, the results presented suggest that the canonically 'proto-planetary' discs of Class II T Tauri stars {\bf have globally low masses in dust observable at millimetre wavelengths, and conversion to larger bodies (anywhere from small rocks up to planetary cores) must already have occurred.}

Context-dependent avoidance of predatory centipedes by nocturnal geckos (Oedura lesueurii)

Most research on the anti-predator behaviour of vertebrate prey has focused on their responses to vertebrate predators. Nonetheless, invertebrates are abundant predators in terrestrial ecosystems, and some invertebrates (e.g., centipedes, spiders) attack and consume vertebrates. We used a combination of field data and laboratory experiments to determine whether a predatory centipede (Scolopendridae: Cormocephalus sp.) influences habitat selection by the nocturnal rock-dwelling velvet gecko, Oedura lesueurii. In the field, centipedes and geckos were syntopic, and sheltered beneath rocks with similar physical dimensions, thermal regimes and degree of sun exposure. Nonetheless, geckos rarely shared rocks with centipedes in the field. In laboratory trials, both geckos and centipedes selected shelters with narrow rather than wide crevices. The presence of a centipede modified habitat selection by juvenile geckos, which preferred wide crevices without centipedes to narrow crevices containing centipedes. In contrast, adult geckos continued to select narrow crevices even if these contained centipedes. When we added centipedes to narrow crevices beneath small and large rocks occupied by geckos, both juvenile and adult geckos exited the crevice (especially if it was under a small rather than large rock). Our results show that centipedes influence habitat selection by velvet geckos, and demonstrate that anti-predator behaviours of geckos are both size- and context-dependent. Ontogenetic shifts in behaviour and habitat selection by vertebrates in response to invertebrate predators may be widespread.

In situ analysis of ice table depth variations in the vicinity of small rocks at the Phoenix landing site

Prior to the Phoenix mission, ice stability simulations predicted that surface rocks at the landing site would produce depressions in the ice table (the boundary between dry and ice‐cemented soil) if ground ice at the site were in diffusive equilibrium with atmospheric water vapor. We use stereo images and digital elevation models to investigate variations in the depth of the ice table near two decimeter‐scale rocks at the Phoenix landing site and compare the observed depth variations to ice stability simulations. We find that ice table depth variations observed near rocks at the landing site are consistent with our theoretical predictions. Based on our results we conclude that: 1) Water transport in the near‐surface regolith occurs primarily via vapor diffusion; 2) Environmental conditions in which water transport is dominated by diffusion have been persistent at the landing site for 100s to 1000s of years or longer; that is, ground ice is in diffusive equilibrium with atmospheric water vapor; and 3) In diffusive equilibrium, thermal stability dictates the depth of the ice table on horizontal length scales as small as centimeters.

Implications of coppice stand characteristics on the rockfall protection function

Coppice forest stands can play a key protective role on active rockfall slopes in mountainous regions. This paper aims at quantifying their protection function and at explaining the role of different stand parameters in this function. To achieve these objectives we first made field inventories focussing on the dendrometric and spatial characteristics of 13 coppice stands. Then, we developed a 2D simulation model, called RockCop, to quantify their protective function against rockfall. The simulations show that the predominant size of the falling rocks conditions which of the dendrometric stand parameters mainly determine the protective function of a coppice stand. In the case of small rocks (20 cm Ø), we conclude that a higher stand density improves the protective function. Thus, for those rocks, young stands are most adequate. An acceptable level of protection against medium-sized rocks (50 cm Ø) is only fulfilled by few coppice stands and determined by specific combinations of stand density, stem diameters, basal area and species composition. None of the investigated stands offer sufficient protection against large rocks (1 m Ø).

Breeding Ecology of Kittlitz's Murrelets at Agattu Island, Aleutian Islands, Alaska

The Kittlitz's Murrelet (Brachyramphus brevirostris) is a poorly-known species of alcid and a seabird of conservation concern. Nesting murrelets were discovered at Agattu Island in the western Aleutian Islands, and a field study provided new information on nest site selection, chick growth rates and reproductive success. Twelve ground nests were located in upland habitats (441 masl) at inland areas of Agattu (2.3 km from shore). All nests contained one egg or chick. Murrelets tended to nest in association with a ground cover of orange crustose lichens, bare ground, small rocks and graminoids. Estimates of growth rates for the body mass of nestling Kittlitz's Murrelets were lower (KL < 0.10) than published estimates for other small-bodied alcids with semiprecocial young (KL = 0.14 to 0.23). Murrelet young departed from nests after 30 days of growth at 47% of adult mass but at 80% of adult wing length. Optimal wing-loading may ensure successful dispersal flights from terrestrial nest sites to ocean habitats. Survival of eggs and young were low during the incubation (0.26; 30 d) and brood-rearing periods (0.22; 30 d), leading to a low probability of nest survival (0.06). Losses during incubation were mainly due to avian predators, whereas mortality of young after hatching was caused by inclement weather. Kittlitz's Murrelets have a suite of life-history traits associated with low reproductive potential (small clutch size, slow growth and poor reproductive success) and may have limited ability to recover from population declines.

Relação da granulometria do solo e morfologia do saprolito com a infiltração de água em Neossolos Regolíticos do rebordo do Planalto do Rio Grande do Sul

Os Neossolos Regolíticos apresentam baixo potencial de uso devido a sua pequena profundidade efetiva, à presença de pedregosidade/rochosidade, ao contato lítico próximo à superfície e à ocorrência frequente em terrenos declivosos. Análises mais detalhadas são necessárias para a melhor interpretação desses solos, visto que a filtragem da água de percolação, retenção de solutos e fluídos e sua possível transformação são de interesse ambiental. Nesse sentido, este estudo gerou informações sobre a infiltração de água em cinco áreas de Neossolos Regolíticos, na região do Rebordo do Planalto do Rio Grande do Sul. Para cada área foram descritos e analisados três perfis, sendo a infiltração de água determinada pelo método dos duplos anéis concêntricos. Mesmo com idêntica classificação taxonômica até o quarto nível categórico, os Neossolos apresentaram variações no seu comportamento hídrico, inclusive quando comparados entre os perfis do mesmo ponto de coleta. Os dados sugerem que a infiltração, nesses Neossolos, é influenciada pela configuração de fraturas do saprolito, granulometria, condições de relevo e uso do solo.

ISOTROPIC GAMMA-RAY BACKGROUND: COSMIC-RAY-INDUCED ALBEDO FROM DEBRIS IN THE SOLAR SYSTEM?

We calculate the gamma-ray albedo due to cosmic-ray interactions with debris (small rocks, dust, and grains) in the Oort Cloud. We show that under reasonable assumptions a significant proportion of what is called the "extragalactic gamma-ray background" could be produced at the outer frontier of the solar system and may be detectable by the Large Area Telescope, the primary instrument on the Fermi Gamma-Ray Space Telescope. If detected it could provide unique direct information about the total column density of material in the Oort Cloud that is difficult to access by any other method. The same gamma ray production process takes place in other populations of small solar system bodies such as Main Belt asteroids, Jovian and Neptunian Trojans, and Kuiper Belt objects. Their detection can be used to constrain the total mass of debris in these systems.

Passing of Sovereignty: The Malaysia/Singapore Territorial Dispute before the ICJ

The 2008 Malaysia/Singapore case before the International Court of Justice relates to the dispute concerning territorial sovereignty over three maritime features in the Straits of Singapore, namely Pedra Branca/Pulau Batu Puteh, Middle Rocks and South Ledge. Pedra Branca/Pulau Batu Puteh (hereafter Pedra Branca) is a granite island, measuring 137 m long, with an average width of 60 m. It is situated at the eastern entrance of the Straits of Singapore – one of the busiest maritime passages in the world. It lies approximately 24 nautical miles to the east of Singapore, 7.7 nautical miles to the south of the Malaysian state of Johor and 7.6 nautical miles to the north of the Indonesian island of Bintan. Middle Rocks consists of two clusters of small rocks that are permanently above water, and is located 0.6 nautical miles to the south of Pedra Branca.

Ice table depth variability near small rocks at the Phoenix landing site, Mars: A pre-landing assessment

We combine thermal simulations of ground ice stability near small rocks with extrapolations of the abundance of rocks at the Phoenix landing site based on HiRISE rock counts to estimate the degree of ice table depth variability within the 3.8 m 2 workspace that can be excavated during the mission. Detailed predictions of this kind are important both to test current ground-ice theory and to optimize soil investigations after landing. We find that Phoenix will very likely have access to at least one rock in the diameter range 5 cm to 1 m. Our simulations, which assume the ice to be in diffusive equilibrium with atmospheric water vapor, indicate that all rocks in this size range are associated with an annulus of deep ice-free soil. Ice table depth variability of 1–5 cm is very likely at the landing site due to the presence of small rocks. Further, there are scenarios in which Phoenix might exploit the presence of individual large rocks and/or the arrangement of small rocks to sample soils at depths >10 cm below the average depth predicted from orbit (∼4 cm). Scale analysis to constrain uncertainties in simulation results indicates that estimates of maximum depths may be somewhat conservative and that ice table depressions associated with individual rocks could be deeper and laterally more extended than indicated by formal predictions by mm to cm.