Mass movement

Abstract: Changes in temperature and precipitation have a range of impacts, including change of glacier extent, extent and duration of snow cover, and distribution and thermal properties of permafrost. Similarly, it is likely that climatic changes affect frequency and magnitude of mass movements, such as shallow landslides, debris flows, rock slope failures, or ice avalanches. However, so far changes in mass-movement activity can hardly be detected in observational records. In this progress report we document the role of climate variability and change on mass-movement processes in mountains through the description and analysis of selected, recent mass movements where effects of global warming and the occurrence of heavy precipitation are thought to have contributed to, or triggered, events. In addition, we assess possible effects of future climatic changes on the incidence of mass-movement processes. The report concentrates on high-mountain systems, including processes such as glacier downwasting and the formation of new ice-marginal lakes, glacier debuttressing and the occurrence of rock slope instability, temperature increase and permafrost degradation, as well as on changing sediment reservoirs and sediment supply, with a clear focus on studies from the European Alps.

Abstract: Tree growth and inclination on sloping land is affected by mass movement. Suitable analysis of tree growth and tree form can therefore provide considerable information on mass movement activity. This paper reports a new, automated method for studying the temporal and spatial aspects of mass movement activity. Ringwidth data from only a few cores per tree are required. The method uses filtering techniques and statistical time series analysis. Preliminary results for two landslides in the Barcelonnette area of the French Alps show a relative stability of movement activity over the last hundred years (no trend) and short periodicity (six to seven year periods) of mass movement activity. The advantages of the method (over other, mostly visual, methods) are its clearness, flexibility, repeatability and rapidity. However, further testing is needed to examine its reliability.

Abstract: . Digital elevation models (DEM) are widely used to determine characteristics of mass movement processes such as accumulation and deposition of material, volume estimates or the orientation of discontinuities. To create such DEMs point cloud data is provided by terrestrial laser scanning (TLS) and recently used for analysis of mass movements. Therefore the reliability of TLS data was investigated in a comparative study with tachymetry. The main focus was on the possibility of determining movement patterns of landslides Using the methodology presented it was not possible to determine movement rates

Abstract: Rock glaciers are distinct landforms whose wide distribution, occurrence, and significance often go unrecognised. They are deposits of poorly sorted, angular, blocky to tabular debris which are held together by an ice core or a matrix of ice-cemented fine clastics. Rock glaciers have formed in glaciated and non-glaciated areas. Many researchers have suggested that the absence of an ice core or the lack of movement indicates relict or fossil status. Active and inactive states can be viewed as the end members of a movement continuum. Movement rates, derived from world-wide locations as reported in the literature, range from less than 1 cmyr−1 to greater than 130cmyr−1. Unfortunately, lack of observed movement has been equated incorrectly with an inactive status. Rock glacier movement must be considered from a rheological point of view. Movement is controlled by the transformation of potential energy to kinetic energy as the system attempts to reach thermal equilibrium or stability. Whereas a glacier can completely disappear or redevelop, reactivation of a rock glacier requires only the re-establishment of the conditions responsible for development and maintenance of interstitial ice. Although it might not be possible to re-establish an ice core, interstitial areas can definitely be recharged with ice and thus facilitate movement. The concept of active versus inactive should be abandoned in favor of the view that a spatial and temporal continuum of form and movement exists.