Observation of surface features on an active landslide, and implications for understanding its history of movement

International audienceSurface features are produced as a result of internal deformation of active landslides, and are continuously created and destroyed by the movement. Observation of their presence and distribution, and surveying of their evolution may provide insights for the zonation of the mass movement in sectors characterized by different behaviour. The present study analyses and describes some example of surface features observed on an active mass movement, the Slumgullion earthflow, in the San Juan Mountains of southwestern Colorado. The Slumgullion earthflow is one of the most famous and spectacular landslides in the world; it consists of a younger, active part which moves on and over an older, much larger, inactive part. Total length of the earthflow is 6.8 km, with an estimated volume of 170 × 10 6 m 3 . Its nearly constant rate of movement (ranging from about 2 m per year at the head, to a maximum of 6?7 m per year at its narrow and central part, to values between 1.3 and 2 m per year at the active toe), and the geological properties of moving material, are well suited for the observation of the development and evolution of surface features. In the last 11 years, repeated surveying at the Slumgullion site has been performed through recognition of surface features, measurements of their main characteristics, and detailed mapping. In this study, two sectors of the Slumgullion earthflow are analysed through comparison of the features observed in this time span, and evaluation of the changes occurred: they are the active toe and an area located at the left flank of the landslide. Choice of the sectors was dictated in the first case, by particular activity of movement and the nearby presence of elements at risk (highway located only 250 m downhill from the toe); and in the second case, by the presence of many surface features, mostly consisting of several generations of flank ridges. The active toe of the landslide is characterized by continuous movement which determines frequent variations in the presence and distribution of surface features, as evidenced by the multi-year observations there performed. In addition, monitoring of the inactive material just ahead of the active toe showed that this sector is experiencing deformation caused by the advancing toe. Mapping and interpretation of the different generations of flank ridges at the narrowest and central part of the active Slumgullion landslide evidenced, on the other hand, the gradual narrowing of the mass movement, which was accompanied by a reduction in the thickness of the material involved in landsliding. Multi-time observation of the surface features at the Slumgullion earthflow allowed to reconstruct the evolution of specific sectors of the mass movement. This low-cost approach, whose only requirements are the availability of a detailed topographic map, and repeated surveying, is therefore particularly useful to better understand the kinematics of active mass movements, also in order to design the more appropriate stabilization works

Landslide hazard zonation of slopes susceptible to rock falls and topples

International audienceA landslide hazard zonation is a division of the land surface into areas, and the relative ranking of these areas according to degrees of actual or potential hazard from landslides on slopes. Zonation from scientific research does not generally imply legal restrictions, but can be useful to those people who are charged with the land management, by providing them with information that is indispensable for planning and regulation purposes. This paper presents a zonation of rock slopes in carbonate mountains on the boundary to the east of the valley of the Sele River (Campania, southern Apennines of Italy). The mountains are severely affected by rock falls and topples, and the related hazard is, therefore, very high; the presence of inhabited areas (the towns of Valva, Colliano and Collianello) and other human infrastructures at the slope foothills make these phenomena extremely dangerous to the anthropogenic environment. The area is highly seismic, as experienced on the occasion of several moderate to strong earthquakes that have hit this sector of the Apennines. According to the zonation proposed here, the ridge of Mount Valva and Mount Marzano is subdivided into four main areas on the basis of the processes which take place in the different sectors of the mountains: the source area, the talus slope, the rockfall shadow (where scattered outlying boulders are present), and the safe area (outside of the reach of fallen blocks). The four sectors were identified through air-photo interpretation and detailed field surveys, aimed in particular at characterizing and interpreting the main rock mass joint patterns, and their relative orientation with respect to the local slope direction. Geological, morphological and structural analyses permitted one to evaluate and classify those parts of the slope that are more susceptible to detachment of rocks, and to identify the more diffuse types of failure. Due to high seismicity of the study area, particular attention was given to the evaluation of the seismic susceptibility to rock falls, by applying two methods recently proposed in literature. Results from this phase of the study were then integrated by additional information from historical research on slope movements occurred previously in the area. The landslide hazard zonation, shown on large-scale cartography, could be compared to maps depicting the distribution and typology of the anthropogenic activities, and thus constitutes a useful tool for administrators and planners, in order to evaluate the hazards related to slope movements, and the vulnerability of settlements, roads, and other man-made infrastructures

Star formation in Chamaeleon I and III: a molecular line study of the starless core population

The Chamaeleon clouds are excellent targets for low-mass star formation studies. Cha I and II are actively forming stars while Cha III shows no sign of ongoing star formation. We aim to determine the driving factors that have led to the very different levels of star formation activity in Cha I and III and examine the dynamical state and possible evolution of the starless cores within them. Observations were performed in various molecular transitions with APEX and Mopra. Five cores are gravitationally bound in Cha I and one in Cha III. The infall signature is seen toward 8-17 cores in Cha I and 2-5 cores in Cha III, which leads to a range of 13-28% of the cores in Cha I and 10-25% of the cores in Cha III that are contracting and may become prestellar. Future dynamical interactions between the cores will not be dynamically significant in either Cha I or III, but the subregion Cha I North may experience collisions between cores within ~0.7 Myr. Turbulence dissipation in the cores of both clouds is seen in the high-density tracers N2H+ 1-0 and HC3N 10-9. Evidence of depletion in the Cha I core interiors is seen in the abundance distributions of C17O, C18O, and C34S. Both contraction and static chemical models indicate that the HC3N to N2H+ abundance ratio is a good evolutionary indicator in the prestellar phase for both gravitationally bound and unbound cores. In the framework of these models, we find that the cores in Cha III and the southern part of Cha I are in a similar evolutionary stage and are less chemically evolved than the central region of Cha I. The measured HC3N/N2H+ abundance ratio and the evidence for contraction motions seen towards the Cha III starless cores suggest that Cha III is younger than Cha I Centre and that some of its cores may form stars in the future. The cores in Cha I South may on the other hand be transient structures. (abridged)Comment: Accepted for publication in A&A. The resolution of Figure 2 has been degraded and the abstract in the metadata has been shortened to fit within the limits set by arXi

Ultracapacitors for port crane applications: Sizing and techno-economic analysis

The use of energy storage with high power density and fast response time at container terminals (CTs) with a power demand of tens of megawatts is one of the most critical factors for peak reduction and economic benefits. Peak shaving can balance the load demand and facilitate the participation of small power units in generation based on renewable energies. Therefore, in this paper, the economic efficiency of peak demand reduction in ship to shore (STS) cranes based on the ultracapacitor (UC) energy storage sizing has been investigated. The results show the UC energy storage significantly reduce the peak demand, increasing the load factor, load leveling, and most importantly, an outstanding reduction in power and energy cost. In fact, the suggested approach is the start point to improve reliability and reduce peak demand energy consumption

Sinkhole genesis and evolution in Apulia, and their interrelations with the anthropogenic environment

Sinkhole development occurs in many areas of the world where soluble rocks crop out. Sinkholes are generally the surface expression of the presence of caves and other groundwater flow conduits in carbonate rocks, which are solutionally enlarged secondary permeability features. Their formation may be either natural or caused by man's activities. In both cases, heavy consequences have to be registered on the anthropogenic environment and related infrastructures. Knowledge of the mechanism of formation of this subtle geohazard is therefore necessary to planners and decision makers for performing the most appropriate and suitable programs of land use and development. <P style='line-height: 20px;'> The Apulia region of southern Italy is characterized for most of its extension by carbonate rocks, which makes it one of the most remarkable example of karst in the Mediterranean Basin. Based on analysis of literature and in situ surveys, including caving explorations, we have identified in Apulia three main types of possible mechanisms for sinkhole formation: 1) collapse of a chamber in a natural cave or in man-made cavities; 2) slow and gradual enlargement of doline through dissolution; 3) settlement and internal erosion of filling deposits of pre-existing dolines. Since sinkhole formation very often affects directly the human settlements in Apulia, and have recently produced severe damage, some considerations are eventually presented as regards the interrelationships between sinkholes and the anthropogenic environment

Natural and anthropogenic hazards in karst areas of Albania

International audienceIn Albania, about one quarter of the country is occupied by outcroppings of soluble rocks; thus, karst represents an important and typical natural environment. Today karst areas are seriously threatened by a number of hazards, of both natural and anthropogenic origin. Many problems are related to agricultural practices: the use of heavy machinery, ever-increasing in recent years, results at many sites in destruction of the original karst landscapes. Use of pesticides and herbicides, in addition, causes the loss of karst ecosystems of great biological relevance, as has been observed in the Dumre district, where about 80 lakes of karst origin are present in the evaporites of Permian-Triassic age. Agricultural practice performed on slopes with medium to high gradient is a further factor which greatly predispose the slopes to erosion. The cave heritage of Albania (estimated so far in about 1000 caves) is at risk because of the uncontrolled quarrying activities which determine the total or partial destruction of karst caves, including many of naturalistic, archaeological and speleological interest. Many caves have also become sites of illegal disposal of solid and liquid wastes, which causes pollution of the karst ecosystems and of the aquifer therein present, with heavy negative consequences on the quality of water. Even though most of the cases here mentioned are related to anthropogenic activities, the natural hazards, such as subsidence phenomena, floods, and the development of sinkholes, have not to be disregarded

Detection of OD towards the low-mass protostar IRAS16293-2422

Although water is an essential and widespread molecule in star-forming regions, its chemical formation pathways are still not very well constrained. Observing the level of deuterium fractionation of OH, a radical involved in the water chemical network, is a promising way to infer its chemical origin. We aim at understanding the formation mechanisms of water by investigating the origin of its deuterium fractionation. This can be achieved by observing the abundance of OD towards the low-mass protostar IRAS16293-2422, where the HDO distribution is already known. Using the GREAT receiver on board SOFIA, we observed the ground-state OD transition at 1391.5 GHz towards the low-mass protostar IRAS16293-2422. We also present the detection of the HDO 111-000 line using the APEX telescope. We compare the OD/HDO abundance ratio inferred from these observations with the predictions of chemical models. The OD line is detected in absorption towards the source continuum. This is the first detection of OD outside the solar system. The SOFIA observation, coupled to the observation of the HDO 111-000 line, provides an estimate of the abundance ratio OD/HDO ~ 17-90 in the gas where the absorption takes place. This value is fairly high compared with model predictions. This may be reconciled if reprocessing in the gas by means of the dissociative recombination of H2DO+ further fractionates OH with respect to water. The present observation demonstrates the capability of the SOFIA/GREAT instrument to detect the ground transition of OD towards star-forming regions in a frequency range that was not accessible before. Dissociative recombination of H2DO+ may play an important role in setting a high OD abundance. Measuring the branching ratios of this reaction in the laboratory will be of great value for chemical models.Comment: 6 pages, 6 figures, 3 tables, accepted for publication in A&A SOFIA/GREAT special issu

Combining historical and geological data for the assessment of the landslide hazard: a case study from Campania, Italy

International audiencePast slope instabilities at Quindici (one of the five towns of Campania that was hit by catastrophic landslides on 5 May 1998) and in the Lauro Valley are investigated to improve the understanding of the landslide history in the area, as a mandatory step for the evaluation of the landslide hazard. The research was performed by combining information on past slope instabilities from both historical and geological data. From numerous historical sources an archive consisting of 45 landsliding and flooding events for the period 1632?1998 was compiled. Landslide activity was also investigated by means of interpretation of multi-year sets of aerial photos, production of Landslide Activity Maps, and excavation of trenches on the alluvial fans at the mountain foothills. Detailed stratigraphic analysis of the sections exposed in the trenches identified landslide events as the main geomorphic process responsible for building up the fans in the study area. Integration of historical and geological approaches provides significant insight into past and recent instability at Quindici. This is particularly valuable in view of the limitations of individual sources of information. Application of such an approach offers potential for improved hazard assessment and risk mitigation

Segregation in desiccated sessile drops of biological fluids

It is shown here that concurrence between advection and diffusion in a drying sessile drop of a biological fluid can produce spatial redistribution of albumen and salt. The result gives an explanation for the patterns observed in the dried drops of the biological fluids.Comment: 6 pages, 3 figures; submitted to European Physical Journal