Dynamics of an active rock glacier (Ötztal Alps, Austria)

The rock glacier Innere Ölgrube, located in a small side valley of the Kauner Valley (Ötztal Alps, Austria), consists of two separate, tongue-shaped rock glaciers lying next to each other. Investigations indicate that both rock glaciers contain a core of massive ice. During winter, the temperature at the base of the snow cover (BTS) is significantly lower at the active rock glacier than on permafrost-free ground adjacent to the rock glacier. Discharge is characterized by strong seasonal and diurnal variations, and is strongly controlled by the local weather conditions. Water temperature of the rock glacier springs remains constantly low, mostly below 1°C during the whole melt season. The morphology of the rock glaciers and the presence of meltwater lakes in their rooting zones as well as the high surface flow velocities of >1 m/yr point to a glacial origin. The northern rock glacier, which is bounded by lateral moraines, evolved from the debris-covered tongue of a small glacier of the Little Ice Age with its last highstand around A.D. 1850. Due to the global warming in the following decades, the upper parts of the steep and debris-free ice glacier melted, whereas the debris-covered glacier tongue transformed into an active rock glacier. Due to this evolution and due to the downslope movement, the northern rock glacier, although still active, at present is cut off from its ice and debris supply. The southern rock glacier has developed approximately during the same period from a debris-covered cirque glacier at the foot of the Wannetspitze massif.     

Modeling and Fitting of Three-Dimensional Mineral Microstructures by Multinary Random Fields

Mathematical Geosciences - Modeling a mineral microstructure accurately in three dimensions can render realistic mineralogical patterns which can be used for three-dimensional processing...     

Sea level induced variations in clay mineral composition in the southwestern South China Sea over the past 17,000 yr

Variations in clay mineral composition of sediment cores from the margin and continental slope of the Sunda Shelf (southern South China Sea, SE Asia) covering the past 17,000 yr reflect changing influences of sediment sources together with clay mineral partitioning processes in shallow waters. We identify the deglacial sea level rise as the principal factor driving these changes. During the late glacial, high values of kaolinite are interpreted to reflect a higher contribution of clays from soils that have formed on the exposed Sunda Shelf and in the southern archipelagos of Indonesia. At this time core sites were located in close proximity to the mouths of the Sunda Shelf palaeo-drainage systems on the emerged shelf (“Sundaland”). The progressive landward displacement of the coastline and breakdown of these vast drainage systems during deglaciation led to a decrease in influence of the kaolinite-rich southern sources. When the coastline had retreated closely to its present-day position in mid-Holocene times, the former dominance of southern sources was replaced by a stronger influence of illite-rich sources (e.g. Borneo). The overriding control of sea level changes on the clay mineral distribution patterns precludes a definite climatic interpretation of clay mineral data in terms of climatic/monsoonal changes in such highly dynamic sedimentary environment.     

Swedish coastal fisheries—From conflict mitigation to participatory management

Several research projects have studied Swedish coastal fishery to investigate the conflict between seals and fishery. In recent years, a strategy of participation by means of co-management has been unfolding. Realising that maintaining the coastal fishery requires societal support and knowledge integration, attempts have been made to introduce the principle of participatory management into the centralised Swedish fisheries management system. However, this co-management approach, presently implemented in six pilot projects, will take a long time to develop through a sustained process of experimentation and improvement.     

The Portuguese bend landslide

The Portuguese Bend landslide, in coastal southern California, is an active, slow-moving mass of blocks and debris that extends from the shoreline to moderate altitudes along part of the southerly margin of the Palos Verdes Hills. These hills form a peninsula that is underlain by Cenozoic sedimentary and volcanic rocks draped anticlinally over a core of Mesozoic schist. In the southerly parts of the peninsula, inherently weak units in the Altamira Shale Member of the Miocene Monterey Formation dip seaward in general concordance with the ground surface. Ground failure has been widespread in this area. It evidently began in mid- to late-Pleistocene time, and it has continued intermittently to the present.

The Portuguese Bend landslide represents a reactivation of movement of the eastern part of a complex of prehistoric landslides occupying an area of approximately two square miles. This latest episode of movement began in 1956, presumably in response to placement of fill during a road construction project. The active slide subsequently was enlarged by sequential failure of adjoining blocks of ground, and by September 1969 about 54,500,000 metric tons of debris was slowly moving downslope in an area of approximately 104 ha. Movement has been continuous since recent failure began in 1956, although the velocity of the active slide decreased markedly after that year. Between 1962 and 1972 the velocity fluctuated only slightly about an average value of about 1 cm per day.

The active slide is an irregular prism, roughly triangular in plan view. The southern side of the triangle trends approximately 1100 m east-west along a stretch of shoreline that essentially coincides with the toe of the slide. The other two sides of the triangle trend northeast and northwest from the ends of the toe and meet about 1200 m north of the shoreline. The thickness of the moving mass differs considerably from one place to another, reflecting both topographic irregularities and major undulations in the underlying surface of movement. The maximum thickness is approximately 75 m.

Movement is occurring along a distinct basal failure surface. The eastern part of the slide is underlain by bedrock, and is bordered by bedrock with a general structure that limits further deep-seated propagation of failure to the east and northeast. In contrast, the western part of the slide is underlain and bordered by extensive ancient landslide deposits that are marginally stable. Further encroachment of the active slide westward and northwestward into these materials was viewed as a distinct possibility at the time the dissertation was prepared and has occurred since then.

Continued movement of the Portuguese Bend landslide since 1956 has been due to four main factors. A rise in the water table during the period 1957–1968 has been documented in the northwestern part of the moving mass and is attributable mainly to infiltration of surface runoff entering numerous open fissures that cut the surface of the slide. The toe of the active slide daylights along the shoreline and is subjected to storm-wave erosion, so that any natural build-up of resisting forces is prevented in this area. The redistribution of mass as the slide has moved along an undulatory failure surface has been responsible for local fluctuations in the driving and resisting forces. Finally, smoothing of irregularities in the failure surface by the moving slide mass must have decreased some of the forces resisting movement.