Steep Face Research Articles

Sustainable Retaining Wall Solution as a Mitigation Strategy on Steep Slopes in Soft Rock Mass

Steep slopes in soft rock are characterized by their susceptibility to instability (rockfall, rockslide) due to weathering and erosion of the slope surface. This article deals with the problem of adapting to the increasing height of the scree slope. The construction of a retaining wall in a scree slope in front of a slope of soft rock with a steep face, where a very rapid weathering and erosion process of weathered material takes place, and the simultaneous deposition of material in front of the steep slope is a common solution. Changes in the geometry of the slope and the front scree are taken into account, and at the same time, sufficient safety against rockfall must be ensured. The analysis is shown on a specific example of a steep flysch slope near Split, Dalmatia. The retaining wall solutions are compared in terms of function, cost and sustainability. The construction of a single colossal, reinforced concrete retaining wall shows that this solution is not feasible due to the high construction costs and CO2 emissions of the retaining wall. A model was therefore developed to determine the height of the retaining walls for different construction time intervals and distances from the original rock face. The critical failure modes were investigated for various retaining wall solutions with regard to the highest degree of utilization of the resistance, which also allows the cost-optimized solutions to be determined. By building two or more successive retaining walls at suitable intervals and at an appropriate distance from the original rock face, construction costs and CO2 emissions can be significantly reduced.

Modelling of waves and wave-induced currents in the vicinity of submerged structures under regular waves using nonlinear wave-current models

The evolution of waves and wave-induced currents around submerged structures under regular waves is simulated using two nonlinear wave-current models (Boussinesq-type); coupled with a one equation turbulence closure model to simulate the energy dissipation due to wave breaking. The first model is utilized to simulate the evolution of waves and wave-induced currents around porous structures, while the second model is used to simulate those around impermeable structures. The equation of motion for the porous medium in the first model incorporates an empirical Forchheimer-type term for laminar and turbulent frictional losses and inertial term to account for acceleration effects. In both models, an artificial energy dissipation term is introduced to overcome unrealistic flow patterns and surface water fluctuations, which lead to numerical instabilities near steep faces of submerged structures. In the present study, an improved wave breaking sub-model is introduced in 2DH, and the predictive skills of two improved models are investigated with a published and a new set of experimental data. The comparison between simulations and laboratory data show promising results for the wave height, mean-water level and current distribution around submerged structures for 2DH wave propagation.

Stepping Stones to Reproductive Success: The Role of Geomorphology in Seabird Nest Site Choice

Photo 1. Geomorphological features related to seabird nest sites. (A) L’île de l’Amas off Cap-Fréhel, Brittany, France. The island presents several key geomorphological features at various spatial scales, from largest to smallest: small island (~100 × 50 m at low tide), steep slope (north facing, marked with an N), gentle slope (south facing), low degree of enclosure. (B) Detail of a steep slope face with nesting Kittiwakes. Steep slope-nesting seabirds show no requirement for nest site enclosure, and nest indifferently on large or small islands; the steep face deters both land and seaborne predation. Photo credit: Marie Eveillard-Buchoux. These photographs illustrate the article “Between a rock and a large place: the importance of multi-scale geomorphological features to seabird nest site selection” by Marie Eveillard-Buchoux and Peter G. Beninger in Ecology, https://doi.org/10.1002/ecy.3566.

Dynamics of southern beech (Nothofagaceae) stands in the lowland North Island of New Zealand

ABSTRACT In south-central Chile, the dynamics of southern beech (Nothofagaceae) stands vary predictably along climatic gradients. Beeches form persistent stands at high elevations, but their establishment on lowland sites depends mainly on catastrophic disturbances. In New Zealand, nearly all studies of beech forest dynamics to date have reported all-sized, persistent populations. However, previous work has focused largely on the South Island or on North Island mountains, where beeches are widespread and often dominant. Little is known about beech dynamics in the warm North Island lowlands, where beeches are less common. We aimed to clarify the circumstances that enable beeches to establish on lowland sites in the North Island. We measured population structures of beeches and associated species on 11 plots distributed across a range of climate, lithology and topography. On sites where the most shade-tolerant broadleaved trees were absent or uncommon, all-sized populations showed that beech regeneration did not depend on major disturbances. These stands were located mostly on steep faces or ridges with soil carbon:nitrogen ratios > 18, usually with ericaceous understoreys. On sites with higher N availability, where shade-tolerant broadleaved trees were abundant, beech populations were generally sparser, with restricted age ranges. One of these ± even-aged beech stands appeared to have established after windthrow, the other four after fires. Recent dieback of Weinmannia racemosa associated with insect attack had resulted in another wave of beech regeneration in one of the post-fire stands. Establishment on landslides appears to only rarely enable beeches to capture new sites in the lowland North Island. We conclude that beeches form stable self-replacing stands on lowland North Island sites with low nitrogen availability, but that exogenous disturbances occasionally enable beeches to establish as pioneers on sites with higher nitrogen availability. The early successionalrole commonly seen in lowland south-central Chile thus appears less widespread in New Zealand.

Morphology of estuarine bedforms, Weser Estuary, Germany

AbstractLarge bedforms (dunes) are present in many shallow‐water environments. Knowledge of their dimensions and dynamics is required for river and coastal management. In tidal rivers and estuaries, the interaction among hydrodynamics (which results from the action of river and tidal flows), sediment transport and bedform shape and size is complex. In the present study, the distribution and morphology of bedforms in the Weser Estuary, Germany, were investigated. Bedforms were identified in bathymetric data of monthly multibeam echosounder surveys along the navigation channel during the years 2009 to 2013. Their size and shape were characterized. Bedforms were present along most of the channel, except at the position of the estuarine turbidity maximum and where dredging is carried out. Average bedform length varied between 20 and 60 m and bedform height between 0.3 and 1.6 m. Bedform asymmetry varied spatially and temporally along the estuary. In times of high river discharge, bedforms were generally more ebb‐asymmetric than in times of low discharge. The bedforms were predominantly two‐dimensional low‐angle dunes with their steepest slope situated near the bedform crest. A significant proportion of bedforms possessed a steep face (portion of the lee side steeper than 15°). This implies that they are likely to create flow separation and a turbulent wake, with a strong potential to induce high bedform roughness. However, important variations in steep face area density were noted, both spatially along the estuary and temporally as a function of the tidal phase (ebb or flood) and the seasonal variation in river discharge. The results have wide implications in terms of understanding and modelling hydrodynamics and sediment transport in estuaries.

Origin, geomorphology and geoheritage potential of Australia’s longest coastal cliff lines

Two spectacular cliff lines occur along Australia’s south and west coasts: the Great Southern Scarp (new name) and the Zuytdorp Cliffs. Detailed measurements of their length show that they are exceptionally long and unusually continuous. The Great Southern Scarp is the southern edge of the Nullarbor Plain’s Bunda Plateau; it is cut into shallow marine sediments and extends for 820 km. Once a continuous sea-cliff, local uplift has isolated two sections from the ocean, so it now comprises the Bunda Cliffs (210 km of coastal cliff, 180 km of which is uninterrupted cliff line), Hampton Range (inland; 300 km), Baxter Cliffs (160 km of coastal cliff) and Wylie Scarp (inland; 160 km). The Zuytdorp Cliffs are coastal cliffs cut into eolianite, and extend for 210 km with an uninterrupted section of 120 km. The length of the Great Southern Scarp and the Zuytdorp Cliffs results from an unusual combination of circumstances. They are both composed of poorly jointed, relatively homogenous biogenic calcarenites, presented to high-energy ocean waves by regional uplift. The carbonates are sufficiently well cemented to maintain a steep vertical cliff face, but susceptible to disintegration under direct wave attack. Cliff retreat has been fairly uniform because of the broad spatial scale of both lithology and erosion. The arid climate, absence of nearby non-karstic catchments and karstic nature of the cliffs’ hinterlands has discouraged integrated drainage development, so no significant fluvial systems dissect the cliffs; this is a key factor in cliff edge preservation. In the case of the Great Southern Scarp, these processes have formed the longest continuous cliff line in Australia and probably the world. Referenced against criteria from Australia’s National Heritage List, the cliffs have potentially international/national levels of significance for the rarity of their scale, their demonstration of landscape evolution, and their spectacular beauty.KEY POINTSAustralia’s longest coastal cliffs, the Bunda (SA) and Zuytdorp (WA) cliffs, are equal in length (210 km, within defined confidence levels).The Bunda Cliffs are part of the Great Southern Scarp (new name), an 820 km-long feature of the Nullarbor Plain that also includes the coastal Baxter Cliffs (160 km in length) and two paleocoastal scarps.The unusual continuity of the cliff lines results from a landscape history specific to the Australian continent, and the Great Southern Scarp is likely to be unusual on a global scale.The Great Southern Scarp and the Zuytdorp Cliffs have potentially national and/or international levels significance for geoheritage values in the criteria of events and processes, rarity and aesthetics.

Enigmatic Deep-Water Mounds on the Orphan Knoll, Labrador Sea

Deep-sea mounds can have a variety of origins and may provide hard-substrate features in depths that are normally dominated by mud. Orphan Knoll, a 2 km high bedrock horst off northeast Newfoundland, hosts more than 250 mounds of unknown composition, 10-1000 m high and 1-3 km wide in water depths of 1600–3200 m. The study objective was to characterize the size, shape, orientation, and composition of the enigmatic Orphan Knoll mounds, in order to determine their age and origin. Archival ship-based side-scan sonar, multibeam sonar, airgun, high-resolution sparker and 3.5 kHz acoustic sub-bottom profiling, and newly acquired ship-based multibeam sonar, video transects by remotely operated vehicle (ROV), rock samples, and near-bottom multibeam sonar data were analyzed. Four mounds were studied during two ROV dives. Archival sidescan sonar data show >200 mounds. Sparker profiles show that the mound crests are covered by condensed stratified Quaternary sediment and airgun seismic data show faults reaching near the seafloor. New multibeam sonar data show mounds are dominantly conical to elliptical in shape, but without preferred orientation or alignment. ROV transects and near-bottom multibeam showed that three mounds were rounded and symmetrically arranged, while a fourth was more asymmetrical, with steep faces on the southwestern and southeastern flanks, where finely bedded to massive sedimentary bedrock outcropped dipping 15-45°SW. Rock samples from the mounds include Eocene calcareous ooze and mid-Miocene bedded pelagic limestone. Thick ferromanganese crusts were found on many surfaces, obscuring possible outcrops from physical sampling. Polymetallic nodules were found on the slope of one mound. Ice-rafted detritus, including igneous and metamorphic rocks and Paleozoic limestone and dolostone, was common in the sediments immediately surrounding the mounds. Quaternary sub-fossil solitary scleractinian corals accumulated over a span of at least 0.18 Ma at the base of one mound. The presence of uplifted condensed Eocene-Miocene rocks on the mounds and faulting in seismic profiles suggest uplift during reactivation of old rift-related faults during the Neogene, with seabed mass wasting creating residual mounds, which were then draped by Quaternary proglacial muds. Sculpting of hemipelagic Quaternary sediment by bottom currents probably contributed to mound morphology.

Proposals for enhancements of topographic maps for high alpine tours

Abstract. Today we have diverse and high-quality bases for the planning of high alpine tours. Most widely used are topographic maps, tour guides and online portals. In combination with a topographic map or a map extract, photos and topos, the textual description of a tour guide gives us a comprehensive and detailed picture of our planned high alpine tour. However, this picture can still be improved. The character of a high alpine tour is determined by many criteria. Some of the most important ones can be examined with a topographic map:Length of the tour (distances, total time)Altitude profile (in relation to sea level, differences in altitude)Steepness and exposure of the terrain (steep faces, ridges)Land cover (rock, glacier, moraine, meadows, forest)Other important criteria of a high alpine tour are described textually in tour guides and tour reports on the Internet.Some of these criteria or properties remain unchanged over a long time, others can change within hours. Unchanging properties are for instance theDifficulties in climbing (according to international UIAA scale)Stability or fragility of the rocksClarity of the terrain (structure, important for pathfinding)Slowly changing properties are theCondition of glaciers (snow cover, crevasses, retreat)Stability of slopes (glacial moraines)Degree of protection (security hooks, safety rods, fixed ropes, rappelling points)Marking of the route (Steinmänner, coloured markings)Number of rope teams on the route (potential waiting times, traffic jams, oncoming traffic)Suddenly changing properties are theWeather conditions (temperature, wind, clouds, rain- or snowfall, sight, insolation)Conditions on the terrain (fresh snow, moisture, icing of the rocks)Rock or ice fallFrom the cartographic perspective, in particular the unchanging or slowly changing properties are of interest. How can these properties be mapped in an accurate and comprehensible way?This presentation focuses on potential enhancements of topographic maps, topos and tour guides, to map the above-named unchanging or slowly changing properties of high alpine tours. In this context, the avoidance of overcrowding of the already dense topographic maps is an important requirement, especially for the printed versions of these maps. In interactive online maps, the new map content can be added with a new map layer. Tour guides often include extracts of a topographic map, where requirements and constraints for new map content may be not as strong as in the original printed version. The potential for enhancements of the existing planning bases for high alpine tours is considerable. Due to global warming, route conditions are changing quickly. Unexpected situations on high alpine tours emphasize the necessity of an enhancement or supplement of the existing cartographic representations.

Automated Swiss-Style Relief Shading and Rock Hachuring

Rock depiction in Swiss topographic maps has evolved from humble line drawings into expressive renderings indicating slope, aspect and traversability. In this paper, an automatic method to derive monochrome Swiss-style rock hachures from a raster elevation model is presented. The proper placement and light modulation of the linear strokes depend on the availability of sound foundations for both terrain generalization and relief shading, for which two novel methods are introduced. The generalization applies line integral convolution along slope lines to the elevation values. The resulting smoothed raster has the footprint of its steep faces enlarged to increase the map space available for steep faces. The shaded relief is generated with the focus on terrain edges, unlike common raster cell-based methods. The rock hachures are modulated according to the grey values of the shaded relief. Finally, we present two topographic maps that demonstrate this new method of depicting relief.

Numerical modelling of wave transformation over submerged breakwaters using Boussinesq-type models

Predictive skills of two numerical models, which are developed using two widely-recognised Boussinesq-type equations were further investigated in modelling evolution of water waves propagating over submerged breakwaters and the results were compared. These models are often used for practical applications due to their capabilities of simulating complex hydrodynamic characteristics in nearshore region. However, both models are found to be vulnerable to numerical instabilities when simulating wave propagation over submerged breakwaters particularly with small freeboards and steep face slopes. An artificial energy dissipation term was successfully introduced locally into one of the Boussinesq-type models to overcome unrealistic flow patterns that lead to these numerical instabilities near submerged breakwaters and the modified model was verified using a new set of wave flume data.

Virtual Structural Analysis of Jokisivu Open Pit Using ‘Structure-from-Motion’ Unmanned Aerial Vehicles (UAV) Photogrammetry: Implications for Structurally-Controlled Gold Deposits in Southwest Finland

Unmanned aerial vehicles (UAVs) are rapidly growing remote sensing platforms for capturing high-resolution images of exposed rock surfaces. We used a DJI Phantom 3 Professional (P3P) quadcopter to capture aerial images that were used to generate a high-resolution three-dimensional (3-D) model of the Jokisivu open-pit gold deposit that is located in southwestern Finland. 158 overlapping oblique and nadir images were taken and processed with Agisoft Photoscan Pro to generate textured 3-D surface models. In addition, 69 overlapping images were taken from the steep faces of the open pit. We assessed the precision of the 3-D model by deploying ground control points (GCPs) and the average errors were found minimal along X (2.0 cm), Y (1.2 cm), and Z (5.0 cm) axes. The steep faces of the open pit were used for virtual structural measurements and kinematic analyses in CloudCompare and ArcGIS to distinguish the orientation of different fracture sets and statistical categorization, respectively. Three distinct fracture sets were observed. The NW-SE and NE-SW striking fractures form a conjugate geometry, whereas the NNW-SSE striking fractures cut the conjugate fracture set. The orientation of conjugate fractures match well with the resource model of the deposit and NW- and NE-trending segments of regional-scale anastomosing shear zones. Based on the conjugate geometry of fracture sets I and II, and the regional pattern of anastomosing shear system lead us to interpret an origin of gold mineralization in two stages. An early N-S or NNW-SSE crustal shortening, corresponding to the regional D4 (ca. 1.83–1.81 Ga) or pre-D4 (ca. 1.87–1.86 Ga) Svecofennian tectonic event(s) that produced anastomosing shear zones. Subsequent E-W directed D5 contraction (ca. 1.79–1.77 Ga) partly reactivated the anastomosing shear zones with the formation of conjugate system, which controlled the migration of fluids and gold mineralization in SW Finland.

Congress report of the 23rd AGE annual meeting from 26th - 28th April 2018 in Hamburg

The Study Group of Gynecological Endoscopy (AGE) has a growing number of members each year. This is an acknowledgment as well as a challenge for the study group. The challenges were faced in the form of exemplary cooperative work by the core members of AGE, the Velen Study Group for Ambulant Surgery (VAAO), the Foundation of Endometriosis Research (SEF), the Study Group of Urogynecology and Plastic Pelvic Floor Reconstruction (AGUB), the Study Group for Robotic-assisted Surgery in Gynecology (ARCGyn), and the Study Group of Gynecological Oncology (AGO). More than 1500 AGE members have been able to create significant effects preemptively by designing a Congress program that was prepared interactively. The program of live surgery was designed in the course of two days on the basis of an online inquiry. The first transmission of laparoscopy on a body donor and anatomic demonstrations on formalin-fixed specimens were especially significant in this context. Sessions of general gynecology, including myoma therapy, endometriosis and infertility treatment, and gynecologic oncology and urogynecology covered the entire spectrum of minimally invasive surgical techniques. Individual topics were addressed in specific courses. The Congress was preceded by an optional certified basic course (MIC I) of the AGE. Far more than 500 congress attendees from all German-speaking countries were spirited away to a paramedical steep face, which was ascended together with a renowned German extreme climber. The keynote lecture was especially impressive and held by the pioneer and founder of the neuropelveology. The world’s leading expert in this field described the responsibilities of our specialty in a visionary manner and motivated all of the listeners strongly in regard of their actions and efforts.

Characteristics of the Roof Behaviors and Mine Pressure Manifestations During the Mining of Steep Coal Seam

Abstract A steep seam similar simulation system was developed based on the geological conditions of a steep coal seam in the Xintie Coal Mine. Basing on similar simulation, together with theoretical analysis and field measurement, an in-depth study was conducted to characterize the fracture and stability of the roof of steep working face and calculate the width of the region backfilled with gangue in the goaf. The results showed that, as mining progressed, the immediate roof of the steep face fell upon the goaf and backfilled its lower part due to gravity. As a result, the roof in the lower part had higher stability than the roof in the upper part of the working face. The deformation and fracture of main roof mainly occurred in the upper part of the working face; the fractured main roof then formed a “voussoir beam” structure in the strata’s dip direction, which was subjected to the slip- and deformation-induced instability. The stability analysis indicated that, when the dip angle increased, the rock masses had greater capacity to withstand slip-induced instability but smaller capacity to withstand deformation-induced instability. Finally, the field measurement of the forces exerted on the hydraulic supports proved the characteristics of the roof’s behaviors during the mining of a steep seam.

A submarine landslide source for the devastating 1964 Chenega tsunami, southern Alaska

During the 1964 Great Alaska earthquake (Mw 9.2), several fjords, straits, and bays throughout southern Alaska experienced significant tsunami runup of localized, but unexplained origin. Dangerous Passage is a glacimarine fjord in western Prince William Sound, which experienced a tsunami that devastated the village of Chenega where 23 of 75 inhabitants were lost – the highest relative loss of any community during the earthquake. Previous studies suggested the source of the devastating tsunami was either from a local submarine landslide of unknown origin or from coseismic tectonic displacement. Here we present new observations from high-resolution multibeam bathymetry and seismic reflection surveys conducted in the waters adjacent to the village of Chenega. The seabed morphology and substrate architecture reveal a large submarine landslide complex in water depths of 120–360 m. Analysis of bathymetric change between 1957 and 2014 indicates the upper 20–50 m (∼0.7 km3) of glacimarine sediment was destabilized and evacuated from the steep face of a submerged moraine and an adjacent ∼21 km2 perched sedimentary basin. Once mobilized, landslide debris poured over the steep, 130 m-high face of a deeper moraine and then blanketed the terminal basin (∼465 m water depth) in 11±5 m of sediment. These results, combined with inverse tsunami travel-time modeling, suggest that earthquake-triggered submarine landslides generated the tsunami that struck the village of Chenega roughly 4 min after shaking began. Unlike other tsunamigenic landslides observed in and around Prince William Sound in 1964, the failures in Dangerous Passage are not linked to an active submarine delta. The requisite environmental conditions needed to generate large submarine landslides in glacimarine fjords around the world may be more common than previously thought.

Taxonomy, frustular morphology and systematics of Platichthys, a new genus of canal raphe bearing diatoms within the Entomoneidaceae

Platichthys, a new genus of canal raphe bearing diatoms, is formally described following analysis of the frustule morphology using LM and EM examination. The genus type originates from a thermal spring in the temperate climate zone of Chile, and an example of the second member of this new genus is observed from a coastal lagoon on the Galápagos Islands (Isabela Island). Taken together, the morphological features of these two newly described taxa demonstrate a unique set of characteristics observed within Thalassiophysaceae, Bacillariaceae and Entomoneidaceae. Platichthys gen. nov. contains both a canal raphe and fibulae, and the compressed valve face, absence of distinct valve mantle and numerous open porous copulae found in Platichthys gen. nov. are typical of Entomoneidaceae. However, unlike species belonging to Entomoneis, the valves of the new genus do not show frustule twisting and the striae are composed of single simple areolae instead of double rows. The most characteristic feature of the new genus is raphe positioned on an elevated keel, robust tubular fibulae, the strongly developed, steep valve face and an indistinct valve mantle in a form of a narrow structureless strip. The relationships of Platichthys gen. nov. to Nitzschia subgenus Nitzschia and to other sections of Nitzschia sensu lato, Entomoneis and to Hamatusia are discussed.

Correspondence: Incremental Radical Innovation

I found the article, “Incremental and Radical Innovation,” by Norman & Verganti (Winter 2014, 78-96) to be very interesting but also puzzling. Why do the authors make no reference to the concept of local maxima as it occurs in evolutionary biology? The basic idea is that in searching for better ways of existing and propagating, entities can climb up a hill of gradual improvement until they reach the top where further small changes will only move downward. The hilltop is called a local maximum because there may be other peaks that are higher; but, how can you reach these other peaks? This idea has been around for more than 100 years and is not just limited to the academic literature. Richard Dawkins’ book, Climbing Mount Improbable, provides a popular account in which there is a mount with a steep cliff face, almost impossible to climb.1 Out of sight, however, is a sloping path that reaches the top in gradual steps. The idea of local maxima in human design cropped up in 1862 when Eilert Sundt (1817–1875), a Norwegian sociologist, visited England and was impressed by Charles Darwin. He wrote a paper giving a Darwinian model of gradual technical change involving accidental changes, perceived improvements, choice, etc. In his account of shipbuilding, he concludes with the idea of experiments, “when the idea of new and improved forms had first been aroused, then a long series of prudent experiments, each involving extremely small changes, could lead to the happy result that from the boat constructor’s shed there emerged a boat whose like all would desire.” This gradual series of changes comes to a stop when, “Each kind of improvement has progressed to the point where further developments would entail defects that would more than offset the advantage.2 The problem of getting stuck on a point had to be tackled by evolutionary theorists, and maybe the reason for the authors ignoring their ideas is that they came to different conclusions. Norman & Verganti claim that radical innovation needs a different mechanism from the gradual climbing of a slope but Darwinian theorists don’t agree. In ‘Origin’, Darwin wrote, “If it could be demonstrated that any complex organ existed which could not possibly have been formed by numerous successive, slight modifications my theory would absolutely break down.”3 You can’t be much clearer than that. For “complex organ,” substitute “complex system” or “radical innovation” and it becomes obvious that Darwinians have to find a way out of being stuck on a peak. In fact, there are many ways out.

Toward quantifying discrete groundwater discharge from frozen seepage faces using thermal infrared images

AbstractFrozen groundwater seeps from discrete features, such as fractures and faults, are common along steep faces of cliffs, mines, quarries, and road cuts in cold environments at high elevations and latitudes. Our objective is to test whether thermal infrared imaging can be used to quantify groundwater discharge from such discrete features in freezing conditions. Discrete seeps and freezing cliff faces were simulated in a cold room laboratory with a systematic series of experiments captured through infrared imaging. Two zones of distinct surface temperatures were observed at the ice surface: a zone of relatively warm and constant surface temperature above a zone with high thermal gradients. Experimental conditions impacted the length of the relative warm zone. A strong correlation is observed between length of the relative warm zone and the discharge rate suggesting that groundwater discharge from discrete features could be quantified using noninvasive infrared imaging.

Composite rock slope kinematics at the current Randa instability, Switzerland, based on remote sensing and numerical modeling

Kinematic analysis of slope instabilities in brittle rock is crucial for understanding the reaction of the rock mass to external forcing factors. In steep terrain, inaccessibility often limits collection of relevant data and remote sensing techniques must be applied. This is the case at the current Randa rock slope instability in southern Switzerland, where a total volume of about 5–6 million m 3 moves at a rate of up to 30 mm/yr. A large portion of the unstable rock mass is exposed in an 800 m high inaccessible cliff; the main scarp of the May 1991 rock slope failure. Between 2005 and 2007, a comprehensive suite of remote sensing techniques, including photogrammetry, LiDAR, and GB-DInSAR, was combined with 3D geodetic measurements to characterize the rock mass structure and displacement patterns. Photogrammetry and LiDAR data were measured simultaneously from a helicopter using a system allowing for oblique view angles, which provided optimal observations of the steep rock cliff. We used these datasets to map large-scale structures and extract their orientation and minimum persistence, as well as to characterize the 1991 failure scarp. The northern part of the May 1991 failure surface shows a transition from stepped planar sliding at the base, to failed rock bridges in the center, to tensile failure close to the vertical head scarp. Kinematic analysis of the discontinuity sets in the currently moving rock mass shows that both toppling and translational sliding are feasible failure mechanisms. Toppling is more likely for steep faces above 2200 m, whereas translational failure is more likely in the lower portion of the instability. Interpretation of GB-DInSAR displacement maps revealed similar kinematic behavior, and also allowed identification of a basal rupture zone and lateral release plane bounding the instability. Displacement vectors derived from geodetic surveying provided new insights into the 3D kinematic behavior of the instability. All information extracted from different data sets were integrated in a conceptual model, which was then investigated with 2D numerical simulation using the discontinuum code UDEC. The numerical models were able to reproduce the hypothesized kinematic behavior well.

Biogenic origin of coastal honeycomb weathering

AbstractHoneycomb weathering occurs in two environments in Late Cretaceous and Eocene sandstone outcrops along the coastlines of south‐west Oregon and north‐west Washington, USA, and south‐west British Columbia, Canada. At these sites honeycomb weathering is found on subhorizontal rock surfaces in the intertidal zone, and on steep faces in the salt spray zone above the mean high tide level. In both environments, cavity development is initiated by salt weathering. In the intertidal zone, cavity shapes and sizes are primarily controlled by wetting/drying cycles, and the rate of development greatly diminishes when cavities reach a critical size where the amount of seawater left by receding tides is so great that evaporation no longer produces saturated solutions. Encrustations of algae or barnacles may also inhibit cavity enlargement. In the supratidal spray zone, honeycomb weathering results from a dynamic balance between the corrosive action of salt and the protective effects of endolithic microbes. Subtle environmental shifts may cause honeycomb cavity patterns to continue to develop, to become stable, or to coalesce to produce a barren surface. Cavity patterns produced by complex interactions between inorganic processes and biologic activity provide a geological model of ‘self‐organization’. Surface hardening is not a factor in honeycomb formation at these study sites. Salt weathering in coastal environments is an intermittently active process that requires particular wind and tidal conditions to provide a supply of salt water, and temperature and humidity conditions that cause evaporation. Under these conditions, salt residues may be detectable in honeycomb‐weathered rock, but absent at other times. Honeycomb weathering can form in only a few decades, but erosion rates are retarded in areas of the rock that contain cavity patterns relative to adjacent non‐honeycombed surfaces. Copyright © 2010 John Wiley & Sons, Ltd.

A multistory gigantic subaerial debris flow in an active fault scarp in NW Anatolia, Turkey: anatomy, mechanism and timing

Mass instability in the uplifting footwall blocks of normal faults involves a range of regional and local factors including, among others, climatic setting, topography, lithology and particularly ground shaking during earthquakes. Morphological and sedimentological investigations backed by 14C dating on a huge debris flow and its zone of depreciation provided favorable insights for dynamics and causative factors of this mass wasting. Our observations showed that İsmetpaşa Debris Flow with a volume of 96 km 3 involves three individual flows of decreasing significance in the late Pleistocene—Holocene period. The primary flow occurred in relation to a huge landslide developed on highly fractured and altered basaltic lavas near the crest of fault scarp c. 18.7 ka BP and probably conditioned by high precipitation rates in the early Interglacial. Although, most of the blocky debris flow transferred into the neighboring graben to form a 2 km wide debris fan, some remnant blocks and flow-induced valley-side slickensides can still be observed in the zone of depreciation. One km long secondary flow was sourced from the remnants of primary flow and was realized at 7.9 ka BP in another humid period of the Holocene. The third, though minor (less than 100 m long), mobilization of the flow occurred on one of the steep faces of secondary flow in 1960s when the mean precipitation was higher than that of today. Good coincidence of timing of individual debris flows with the humid phases of the late Pleistocene—Holocene period showed that long-term antecedent precipitation is the dominant causative factor.