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Mass Movement (mass + movement)
Selected AbstractsSediment production in large gullies of the Mediterranean area (NE Spain) from high-resolution digital elevation models and geographical information systems analysisEARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2003J. A. Martínez-Casasnovas Abstract Recent studies in the Mediterranean area have shown gully erosion to have a very significant contribution to total soil loss. In the Penedès vineyard region (NE Spain), between 15 and 27% of the land is affected by large gullies and gully-wall retreat seems to be an ongoing process. Multi-date digital elevation model (DEM) analysis has allowed computation of sediment production by gully erosion, showing that the sediment production rates are very high by the, up-to-date, usual global standards. Here, we present a study carried out using large-scale multi-date (1975 and 1995) aerial photographs (1 : 5000 and 1 : 7000) to monitor sediment yield caused by large gullies in the Penedès region (NE Spain). High-resolution DEMs (1 m grid) were derived and analysed by means of geographical information systems techniques to determine the gully erosion rates. Rainfall characteristics within the same study period were also analysed in order to correlate with the soil loss produced. Mass movement was the main process contributing to total sediment production. This process could have been favoured by rainfalls recorded during the period: 58% of the events were of an erosive character and showed high kinetic energy and erosivity. A sediment production rate of 846 ± 40 Mg ha,1 year,1, a sediment deposition rate of 270 ± 18 Mg ha,1 year,1 and a sediment delivery ratio of 68·1% were computed for a gully area of 0·10 km2. The average net erosion within the study period (1975,95) was 576 ± 58 Mg ha,1 year,1. In comparison with other methods, the proposed method also includes sediment produced by processes other than only overland flow, i.e. downcutting, headcutting, and mass movements and bank erosion. Copyright © 2003 John Wiley & Sons, Ltd. [source] Mass movements caused by recent tectonic activity: The 1999 Chi-chi earthquake in central TaiwanISLAND ARC, Issue 4 2003Wen-Neng Wang Abstract The Chi-chi earthquake (MS = 7.7), which occurred in September 1999, seriously damaged central Taiwan. Approximately 2 years later (July 2001), the Toraji typhoon brought a heavy rainstorm (650 mm rain/day) and triggered widespread landslides in central Taiwan and parts of eastern Taiwan. Approximately 10 000 Chi-chi earthquake-induced landslides and 6000 Toraji typhoon-related mass movements were delineated in an area of 2400 km2 using Satellite Pour l'Observation de la Terre (SPOT; French earth resource satellite) images. The landslide distribution could be closely related to the distribution of peak ground acceleration registered during the Chi-chi earthquake. The study area was composed of Tertiary sedimentary and metamorphic rocks, whose age and induration increased eastward. The earthquake-induced landslides were mostly distributed in the region between the Chelungpu Fault and the Lishan Fault to the east, whereas they were few in the region east of the Lishan Fault. The Toraji typhoon in 2001 severely damaged both regions that had been shattered by the Chi-chi earthquake in 1999. The occurrence of earthquake-induced landslides can be correlated with epicentral distance, and their occurrence has more influence from the rock type than from the ground motion. [source] Controlling factors of gullying in the Maracujá Catchment, southeastern BrazilEARTH SURFACE PROCESSES AND LANDFORMS, Issue 11 2005L. de A. P. Bacellar Abstract Hundreds of gullies (,voçorocas') of huge dimensions (up to 400,500 m long, 150 m wide and 50 m deep) are very common in the small Maracujá Catchment in southeastern Brazil. These erosional features, which occur with an uneven intensity throughout the area, started due to bad soil management practices at the beginning of European settlement, at the end of the 17th century, and nowadays are still evolving, but at a slower rate. As surface soils are usually very resistant to erosion, the outcrop of the more erodible basement saprolites seems to be an essential condition for their beginning. An analysis of well known erosion controlling factors was performed, aiming to explain the beginning and evolution of these gullies and to understand the reasons for their spatial distribution. Data shows that geology and, mainly, geomorphology are the main controlling factors, since gullies tend to be concentrated in basement rock areas with lower relief (domain 2) of Maracujá Catchment, mainly at the fringes of broad and flat interfluves. At the detailed scale (1:10 000), gullies are more common in amphitheatre-like headwater hollows that frequently represent upper Quaternary gullies (paleogullies), which demonstrate the recurrence of channel erosion. So, gullies occur in areas of thicker saprolites (domain 2), in places with a natural concentration of surface and underground water (hollows). Saprolites of the preserved, non-eroded hollows are usually pressurized (confined aquifer) due to a thick seal of Quaternary clay layer, in a similar configuration to the ones found in hollows of mass movement (mudflow) sites in southeastern Brazil. Therefore, the erosion of the resistant soils by human activities, such as road cuts and trenches (,valos'), or their mobilization by mudflow movements, seem to be likely mechanisms of gullying initiation. Afterwards, gullies evolve by a combination of surface and underground processes, such as wash and tunnel erosion and falls and slumps of gully walls. Copyright © 2005 John Wiley & Sons, Ltd. [source] Geomorphic changes in a complex gully system measured from sequential digital elevation models, and implications for managementEARTH SURFACE PROCESSES AND LANDFORMS, Issue 10 2003Harley D. Betts Abstract High-resolution digital elevation models (DEMs) were derived from sequential aerial photography of an active ,uvio-mass movement (gully) complex in New Zealand's North Island East Coast region, to measure geomorphic changes over approximately one year. The gully showed a complex behaviour, combining ,uvial and mass movement erosion, deposition, and reworking of materials stored in an active debris fan. During the measurement period 5200 ± 1700 m3 of material were eroded from the 8·7 ha gully complex and 670 ± 180 m3 from the 0·8 ha depositional fan, giving a total of 5870 ± 1710 m3 for the entire gully complex,fan system. The results provide a high-resolution description of gully behaviour over a short time period, and also demonstrate that mass movement (slumping and debris ,ows) accounted for almost 90 per cent (4660 ± 200 m3) of the sediment generated. This erosional response is described in terms of gully evolution by comparing the gully complex to other systems in the region in various stages of development. The effect of gully evolution on geomorphic coupling between the gully complex and channel system is described, and coupling is also shown to vary with the magnitude and frequency of rainfall events. From a land management perspective the success of strategies, such as tree planting, to mitigate against gully erosion depends on the stage of gully development , particularly on whether or not mass movement erosion has begun. In contrast to gully rehabilitation efforts elsewhere, basin-wide afforestation in the early stages of gully incision is favoured over riparian planting, given that mass movement assisted by excessive groundwater pressure is the main process leading to uncontrollable gully expansion. To protect land effectively against continuing gully erosion of headwater catchments and resulting downstream aggradation, it is necessary for land managers to understand the spatial and temporal variability of gully development fully so that mitigation efforts can be targeted appropriately. Copyright © 2003 John Wiley & Sons, Ltd. [source] A Polygenetic Landform At Stígá, Öræfajökull, Southern IcelandGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2004Tim Harris Abstract Recent research has identified problems inherent in the identification and description of landforms. Morphologically similar small-scale glacial and periglacial landforms can be misinterpreted, thus hindering environmental reconstruction. This study reveals that a landform resembling a moraine at Stígárjökull, southern Iceland, is the product of both glacial deposition and mass movement. The landform has two distinct morphological and sedimentological components: a basal, lithologically diverse component, and an upper, lithologically homogenous component. Clast lithological analysis, particle shape and particle size measurements demonstrate that the basal component of the landform consists of sediment whose characteristics match nearby moraines. In contrast, the source of the upper component is a narrow outcrop of rock above the valley floor. Evidence suggests that frost-shattered material was transported across a perennial snow patch to a small moraine, leading to growth of the ,moraine'. This combination of processes is unlikely to be unique, but the geological peculiarities of the field site permitted their identification. It is possible that many similar ,moraines' could be enlarged by subaerial feeding, leading to false reconstruction of glacier form and/or associated rates of erosion and sedimentation. Such polygenetic landform genesis therefore has implications for environmental reconstruction. [source] Catchment-scale contribution of forest roads to stream exports of sediment, phosphorus and nitrogenHYDROLOGICAL PROCESSES, Issue 23 2007Gary J. Sheridan Abstract The relative contribution of forest roads to total catchment exports of suspended sediment, phosphorus, and nitrogen was estimated for a 13 451 ha forested catchment in southeastern Australia. Instrumentation was installed for 1 year to quantify total in-stream exports of suspended sediment, phosphorus, and nitrogen. In addition, a total of 101 road,stream crossings were mapped and characterized in detail within the catchment to identify the properties of the road section where the road network and the stream network intersect. Sediment and nutrient generation rates from different forest road types within the catchment were quantified using permanent instrumentation and rainfall simulation. Sediment and nutrient generation rates, mapped stream crossing information, traffic data and annual rainfall data were used to estimate annual loads of sediment, phosphorus, and nitrogen from each stream crossing in the catchment. The annual sum of these loads was compared with the measured total catchment exports to estimate the proportional contribution of loads from roads within the catchment. The results indicated that 3·15 ha of near-stream unsealed road surface with an average slope of 8·4% delivered an estimated 50 t of the 1142 t of total suspended sediment exported from the catchment, or about 4·4% of the total sediment load from the forest. Stream discharge over this period was 69 573 Ml. The unsealed road network delivered an estimated maximum of 22 kg of the 1244 kg of total phosphorus from the catchment, or less than 1·8% of the total load from the forest. The average sediment and phosphorous load per crossing was estimated at 0·5 t (standard deviation 1·0 t) and 0·22 kg (standard deviation 0·30 kg) respectively. The lower proportional contribution of total phosphorus resulted from a low ratio of total phosphorus to total suspended sediment for the road-derived sediment. The unsealed road network delivered approximately 33 kg of the 20 163 kg of total nitrogen, about 0·16% of the total load of nitrogen from the forest. The data indicate that, in this catchment, improvement of stream crossings would yield only small benefits in terms of net catchment exports of total suspended sediment and total phosphorus, and no benefit in terms of total nitrogen. These results are for a catchment with minimal road-related mass movement, and extrapolation of these findings to the broader forested estate requires further research. Copyright © 2007 John Wiley & Sons, Ltd. [source] High-sensitivity surface micromachinable accelerometer using a ferroelectric substrate and its characterizationIEEJ TRANSACTIONS ON ELECTRICAL AND ELECTRONIC ENGINEERING, Issue 3 2007Seiji Aoyagi Member Abstract The present study reports the fabrication and characterization of a high-sensitivity surface micromachinable accelerometer using a ferroelectric material having a large dielectric constant, such as bulk PZT (,r = 2600). The measurement principle is the detection of capacitance change with respect to the dielectric mass movement in the fringe electrical field. Considering the practical fabrication, a ferroelectric material is used for the substrate instead of the suspended proof mass. Since capacitance is increased not mechanically but electrically, high sensitivity can be expected while maintaining mechanical stiffness, which has the advantage of preventing touch down of the proof mass and widening the allowable measuring range of acceleration. A fabricated sensor is characterized. A high sensitivity of several sub-pF/g is confirmed, which is hundreds of times higher compared to that of a sensor fabricated using the Parylene polymer (,r = 3.15). This sensitivity is an order higher compared to those of other reported capacitive microaccelerometers, which have comparable proof mass sizes and comparable detectable acceleration ranges to the newly fabricated sensor. Copyright © 2007 Institute of Electrical Engineers of Japan© 2007 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc. [source] Catholic and Non-Catholic Theologies of Liberation: Poverty, Self-Improvement, and Ethics Among Small-Scale Entrepreneurs in Guatemala CityJOURNAL FOR THE SCIENTIFIC STUDY OF RELIGION, Issue 1 2002Henri Gooren In the late 1960s and early 1970s, Catholic liberation theology seemed poised to become a mass movement in Latin America, whereas evangelical Protestantism did not seem likely to ever receive broad popular appeal. This paper will explore possible reasons why most of the poor in Latin America preferred to join non-Catholic churches, instead of the so-called Christian Base Communities (CEBs) or other grassroot groups connected with liberation theology. It does so by a review of scientific literature and by presenting empirical data from field research in Guatemala City. Using a neo-Weberian approach, I will argue that various non-Catholic churches foster elements of asceticism and self-improvement, which provide an important asset for the poor in Guatemala in their quest to better their lives both economically and spiritually. [source] A new vision for the field: Introduction to the second special issue on the unified theoryJOURNAL OF CLINICAL PSYCHOLOGY, Issue 1 2005Gregg R. Henriques This is the second of two issues of the Journal of Clinical Psychology focused on the validity and usefulness of a new theoretical vision for the field (Henriques, 2003). The first two contributions from Rand and Ilardi and Geary both enrich the argument that psychology needs to be effectively connected with biology and physics and that the unified theory (via Behavioral Investment Theory) is highly successful in this way. The authors of the subsequent three articles,Shaffer, Quackenbush, and Shealy,show that the Tree of Knowledge System (through the Justification Hypothesis) is deeply commensurate with the dominant paradigms in the social sciences. Thus, the group of authors of these five articles demonstrates the viability of the unified theory both from bottom-up and top-down viewpoints. In the sixth article, the author addresses some important problems that potentially arise with the development of a clearly defined discipline. In the concluding article I address the concerns about the proposal raised by the contributors to the two special issues and articulate how the unified theory lays the foundation for the development of a useful mass movement in psychology. © 2004 Wiley Periodicals, Inc. J Clin Psychol. [source] A study of candidate marine target impact craters in Arabia Terra, MarsMETEORITICS & PLANETARY SCIENCE, Issue 6 2010Germari de VILLIERS Arabia Terra is a region on Mars that straddles the crustal dichotomy, and several proposed shorelines are located in the area. Shallow marine impact craters on Mars likely would exhibit features like those on Earth, including characteristic morphological features that are distinctly different from that of craters formed on land. Common attributes of terrestrial marine impact craters include features of wet mass movement such as gravity slumps and debris flows; radial gullies leading into the crater depression; resurge deposits and blocks of dislocated materials; crater rim collapse or breaching of the crater wall; a central peak terrace or peak ring terrace; and subdued topography (an indicator of both age and possible flood inundation immediately following impact). In this article, these features have been used to evaluate craters on Mars as to a possible marine origin. This study used a simple quantification system to approximately judge and rank shallow marine impact crater candidates based on features observed in terrestrial analogs. Based on the quantification system, 77 potential shallow marine impact craters were found within an area bounded by 20°N and 40°N as well as 20°W and 20°E. Nine exemplary candidates were ranked with total scores of 70% or more. In a second, smaller study area, impact craters of approximately similar size and age were evaluated as a comparison and average total scores are 35%, indicating that there is some morphological difference between craters inside and outside the proposed shorelines. Results of this type of study are useful in helping to develop a general means of classification and characterization of potential marine craters. [source] Nationalism and Intellectuals in Nations without States: the Catalan CasePOLITICAL STUDIES, Issue 5 2000Montserrat Guibernau This paper aims to provide a theoretical framework for the study of the relationship between intellectuals and nationalism in Western nations without states. The first part sets up a theoretical framework which includes a definition of the concepts of nation, state and nationalism and also introduces the concept of nations without states. It then establishes a distinction between ,state nationalism' and nationalism in ,nations without states'. The second part analyses the relationship between intellectuals and nationalism in the work of Elie Kedourie, Tom Nairn, John Breuilly and Anthony D. Smith. The third part considers the specific context within which intellectuals operate in nations without states. It concentrates on the study of the role of Catalan intellectuals in protecting their vernacular language and culture during Franco's regime (1939,75) together with the processes which, in the 1960s and 1970s, turned Catalan nationalism from an elite into a mass movement. Particular attention is given to the cultural resistance activities carried out by Catalan intellectuals during this period, the reasons why some intellectuals may feel attracted to nationalism, and the rational and emotional arguments employed by intellectuals as mobilizing agents. [source] Typology of Natural Hazards and Assessment of Associated Risks in the Mount Bambouto Caldera (Cameroon Line, West Cameroon)ACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 5 2009Ghislain T. ZANGMO Abstract: Mount Bambouto is a polygenic stratovolcano of the Cameroon Volcanic Line, built between 21 Ma and 4.5 Ma. It is situated approximately 200 km NE of Mount Cameroon, between 09° 55, and 10°15, longitude east and, 05°25, and 05°50, latitude north. The volcano covers an area of 500 km2 and culminates at 2740 m at Mélétan dome and bears a collapsed caldera at the summit (13 × 8 km). Mount Bambouto is characterized by several natural hazards of different origins: meteorological, such as landslides and rock falls; anthropogenic, such as bushfires, tribal wars and deforestation; and volcanological, such as volcanic eruption. The thematic map shows that 55,60% of the caldera has high probability of occurrence of mass movement. The caldera has a high population density (3000 inhabitants), which increases the level of risk, evaluated at approximately $US3.8 million for patrimony, 3000 civilian deaths and destruction of biodiversity. [source] Sediment production in large gullies of the Mediterranean area (NE Spain) from high-resolution digital elevation models and geographical information systems analysisEARTH SURFACE PROCESSES AND LANDFORMS, Issue 5 2003J. A. Martínez-Casasnovas Abstract Recent studies in the Mediterranean area have shown gully erosion to have a very significant contribution to total soil loss. In the Penedès vineyard region (NE Spain), between 15 and 27% of the land is affected by large gullies and gully-wall retreat seems to be an ongoing process. Multi-date digital elevation model (DEM) analysis has allowed computation of sediment production by gully erosion, showing that the sediment production rates are very high by the, up-to-date, usual global standards. Here, we present a study carried out using large-scale multi-date (1975 and 1995) aerial photographs (1 : 5000 and 1 : 7000) to monitor sediment yield caused by large gullies in the Penedès region (NE Spain). High-resolution DEMs (1 m grid) were derived and analysed by means of geographical information systems techniques to determine the gully erosion rates. Rainfall characteristics within the same study period were also analysed in order to correlate with the soil loss produced. Mass movement was the main process contributing to total sediment production. This process could have been favoured by rainfalls recorded during the period: 58% of the events were of an erosive character and showed high kinetic energy and erosivity. A sediment production rate of 846 ± 40 Mg ha,1 year,1, a sediment deposition rate of 270 ± 18 Mg ha,1 year,1 and a sediment delivery ratio of 68·1% were computed for a gully area of 0·10 km2. The average net erosion within the study period (1975,95) was 576 ± 58 Mg ha,1 year,1. In comparison with other methods, the proposed method also includes sediment produced by processes other than only overland flow, i.e. downcutting, headcutting, and mass movements and bank erosion. Copyright © 2003 John Wiley & Sons, Ltd. [source] Talus Instability in a Recent Deglaciation Area and Its Relationship to Buried Ice and Snow Cover Evolution (Picacho Del Veleta, Sierra Nevada, Spain)GEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 2 2003Antonio Gómez The southernmost glacier in Europe formed during the Little Ice Age at the foot of the north wall of Picacho del Veleta (3 398 m) in Sierra Nevada, in the southeast region of the Iberian Peninsula (lat. 37,03,N, long. 3,22,W). The glacier gradually retreated during the last century, leaving a large talus slope at the base of the wall. The unconsolidated material covering the ice masses acted as a thermal insulator. Recent bottom temperature of snow (BTS) analyses and drillings indicate that the ice still exists within the talus. Evidence from field observations made during the period 1995,2001, revealed that large mass movements occurred during the driest summers (1998 and especially, 1999 and 2000) when the talus was snow free. These conditions suggest a direct relationship between talus stability and thermal insulation from the snow cover in areas where buried ice or decaying marginal permafrost exists. [source] Geophysical investigation and dynamic modelling of unstable slopes: case-study of Kainama (Kyrgyzstan)GEOPHYSICAL JOURNAL INTERNATIONAL, Issue 1 2008G. Danneels SUMMARY The presence of massive Quaternary loess units at the eastern border of the Fergana Basin (Kyrgyzstan, Central Asia) makes this area particularly prone to the development of catastrophic loess earthflows, causing damages and injuries almost every year. Efficient disaster management requires a good understanding of the main causes of these mass movements, that is, increased groundwater pressure and seismic shaking. This paper focuses on the Kainama earthflow, mainly composed of loess, which occurred in 2004 April. Its high velocity and the long run-out zone caused the destruction of 12 houses and the death of 33 people. In summer 2005, a field survey consisting of geophysical and seismological measurements was carried out along the adjacent slope. By combination and geostatistical analysis of these data, a reliable 3-D model of the geometry and properties of the subsurface layers, as shown in the first part of the paper, was created. The analysis of the seismological data allowed us to point out a correlation between the thickness of the loess cover and the measured resonance frequencies and associated amplification potential. The second part of this paper is focused on the study of the seismic response of the slope by numerical simulations, using a 2-D finite difference code named FLAC. Modelling of the seismic amplification potential along the slope confirmed the results obtained from the seismological survey,strong amplifications at the crest and bottom of the slope where there is a thick loess cover and almost no amplification in the middle part of the slope. Furthermore, dynamic slope stability analyses were conducted to assess the influence of local amplifications and increased groundwater pressures on the slope failure. The results of the dynamic modelling, although preliminary, show that a combination of seismic and hydrologic origin (pore pressure build-up during the seismic shaking) is the most probable scenario responsible for the 2004 failure. [source] Mass movements caused by recent tectonic activity: The 1999 Chi-chi earthquake in central TaiwanISLAND ARC, Issue 4 2003Wen-Neng Wang Abstract The Chi-chi earthquake (MS = 7.7), which occurred in September 1999, seriously damaged central Taiwan. Approximately 2 years later (July 2001), the Toraji typhoon brought a heavy rainstorm (650 mm rain/day) and triggered widespread landslides in central Taiwan and parts of eastern Taiwan. Approximately 10 000 Chi-chi earthquake-induced landslides and 6000 Toraji typhoon-related mass movements were delineated in an area of 2400 km2 using Satellite Pour l'Observation de la Terre (SPOT; French earth resource satellite) images. The landslide distribution could be closely related to the distribution of peak ground acceleration registered during the Chi-chi earthquake. The study area was composed of Tertiary sedimentary and metamorphic rocks, whose age and induration increased eastward. The earthquake-induced landslides were mostly distributed in the region between the Chelungpu Fault and the Lishan Fault to the east, whereas they were few in the region east of the Lishan Fault. The Toraji typhoon in 2001 severely damaged both regions that had been shattered by the Chi-chi earthquake in 1999. The occurrence of earthquake-induced landslides can be correlated with epicentral distance, and their occurrence has more influence from the rock type than from the ground motion. [source] Remote sensing of permafrost-related problems and hazardsPERMAFROST AND PERIGLACIAL PROCESSES, Issue 2 2008Andreas Kääb Abstract Modern remote sensing techniques can help in the assessment of permafrost hazards in high latitudes and cold mountains. Hazard development in these areas is affected by process interactions and chain reactions, the ongoing shift of cryospheric hazard zones due to atmospheric warming, the large spatial scales involved and the remoteness of many permafrost-related threats. This paper reviews ground-based, airborne and spaceborne remote sensing methods suitable for permafrost hazard assessment and management. A wide range of image classification and change detection techniques support permafrost hazard studies. Digital terrain models (DTMs) derived from optical stereo, synthetic aperture radar (SAR) or laser scanning data are some of the most important data sets for investigating permafrost-related mass movements, thaw and heave processes, and hydrological hazards. Multi-temporal optical or SAR data are used to derive surface displacements on creeping and unstable frozen slopes. Combining DTMs with results from spectral image classification, and with multi-temporal data from change detection and displacement measurements significantly improves the detection of hazard potential. Copyright © 2008 John Wiley & Sons, Ltd. [source] Solifluction processes in an area of seasonal ground freezing, Dovrefjell, NorwayPERMAFROST AND PERIGLACIAL PROCESSES, Issue 1 2008Charles Harris Abstract Continuous monitoring of soil temperatures, frost heave, thaw consolidation, pore water pressures and downslope soil movements are reported from a turf-banked solifluction lobe at Steinhøi, Dovrefjell, Norway from August 2002 to August 2006. Mean annual air temperatures over the monitored period were slightly below 0°C, but mean annual ground surface temperatures were around 2°C warmer, due to the insulating effects of snow cover. Seasonal frost penetration was highly dependent on snow thickness, and at the monitoring location varied from 30,38,cm over the four years. The shallow annual frost penetration suggests that the site may be close to the limit of active solifluction in this area. Surface solifluction rates over the period 2002,06 ranged from 0.5,cm yr,1 at the rear of the lobe tread to 1.6,cm yr,1 just behind the lobe front, with corresponding soil transport rates of 6,cm3,cm,1 yr,1 and 46,cm3,cm,1 yr,1. Pore water pressure measurements indicated seepage of snowmelt beneath seasonally frozen soil in spring with artesian pressures beneath the confining frozen layer. Soil thawing was associated with surface settlement and downslope soil displacements, but following clearance of the frozen ground, later soil surface settlement was accompanied by retrograde movement. Summer rainfall events caused brief increases in pore pressure, but no further soil movement. Surface displacements exceeded maximum potential frost creep values and it is concluded that gelifluction was an important component of slow near-surface mass movements at this site. Temporal and spatial variations in solifluction rates across the area are likely to be considerable and strongly influenced by snow distribution. Copyright © 2008 John Wiley & Sons, Ltd. [source] Substrate determines asymmetrical gait dynamics in marmosets (Callithrix jacchus) and squirrel monkeys (Saimiri boliviensis)AMERICAN JOURNAL OF PHYSICAL ANTHROPOLOGY, Issue 4 2009Jesse W. Young Abstract Studies of skeletal pathology indicate that injury from falling accounts for most long bone trauma in free-ranging primates, suggesting that primates should be under strong selection to manifest morphological and behavioral mechanisms that increase stability on arboreal substrates. Although previous studies have identified several kinematic and kinetic features of primate symmetrical gaits that serve to increase arboreal stability, very little work has focused on the dynamics of primate asymmetrical gaits. Nevertheless, asymmetrical gaits typify the rapid locomotion of most primates, particularly in smaller bodied taxa. This study investigated asymmetrical gait dynamics in growing marmosets and squirrel monkeys moving on terrestrial and simulated arboreal supports (i.e., an elevated pole). Results showed that monkeys used several kinematic and kinetic adjustments to increase stability on the pole, including reducing peak vertical forces, limiting center of mass movements, increasing substrate contact durations, and using shorter and more frequent strides (thus limiting disruptive whole-body aerial phases). Marmosets generally showed greater adjustment to pole locomotion than did squirrel monkeys, perhaps as a result of their reduced grasping abilities and retreat from the fine-branch niche. Ontogenetic increases in body size had relatively little independent influence on asymmetrical gait dynamics during pole locomotion, despite biomechanical theory suggesting that arboreal instability is exacerbated as body size increases relative to substrate diameter. Overall, this study shows that 1) symmetrical gaits are not the only stable way to travel arboreally and 2) small-bodied primates utilize specific kinematic and kinetic adjustments to increase stability when using asymmetrical gaits on arboreal substrates. Am J Phys Anthropol, 2009. © 2008 Wiley-Liss, Inc. [source] | |||||||||||||||||||