Interactions between rock avalanches and glaciers in the Mont Blanc massif during the late Holocene

Rock avalanches are common in the Mont Blanc massif, which is bordered by valleys with large resident and tourist populations and important highways. This paper combines historical data with detailed geomorphological mapping, stratigraphic observation, and absolute and relative dating, to interpret several deposits resulting from rock avalanching onto glaciers.Nineteen rock falls and rock avalanches are described, ranging in volume from 10,000 m³ to 10 × 10⁶ m³. They occurred between 2500 BP and AD 2007 at six sites. The events at three sites (Miage and Drus Glaciers, and Tour des Grandes Jorasses) are characterised by short travel distances; those at Brenva, Triolet, and Frébouge Glaciers exhibit excessive travel distances.Interactions between rock avalanches and glaciers are of four types: (i) rock-avalanche triggering, where glacial and paraglacial controls include debuttressing of rockwalls due to glacier thinning and retreat, oversteepening of rock slopes by glacial erosion, and effects of glaciers on permafrost; (ii) rock-avalanche mobility, in which mobility and travel distance are modified by channelling of rock-avalanche debris by moraines and valleys, incorporation of ice and snow (often >50% for large events), and irregularities on the glacier surface; (iii) deposit sedimentology, where melting of incorporated ice transforms the final deposit by reducing its thickness typically to <5 m, and debris of variable thicknesses is juxtaposed in a hummocky deposit with chaotic piles of angular rock debris; and (iv) glacier dynamics where insulating debris deposited upon a glacier produces a debris-covered glacier of different dynamics, and high elevated scars can favour the formation of small glaciers.     

The Cascade rock avalanche: implications of a very large Alpine Fault-triggered failure,New Zealand

Catastrophic deep-seated rock slope failures (RSFs; e.g., rock avalanches) can be particularly useful proxies for fault rupture and strong ground motion, and currently represent an underappreciated hazard of earthquakes in New Zealand. This study presents observations of the previously undescribed Cascade rock avalanche (CRA), a c. 0.75 km³ single-event, long-runout, catastrophic failure interpreted to have been coseismically triggered by a large to great earthquake c. 660 AD on the Alpine Fault. Despite its size and remarkable preservation, the CRA deposit has been previously identified as a terminal moraine and fault-damaged outcrop, highlighting the common misinterpretation of similar rock avalanche deposits. Comparisons are drawn between the CRA and other Alpine Fault-attributed rock avalanches, such as the better-studied c. 860 AD Round Top rock avalanche, to re-assess coseismic rock avalanche hazard. Structural relationships indicate the rock mass comprising the CRA may have formerly been a portion of a larger (c. 3 km³) RSF, before its catastrophic collapse on a deep-seated gravitational collapse structure (sackung). Sackungen and RSFs are common throughout the Southern Alps and other mountainous regions worldwide; in many cases, they should be considered potential precursors to catastrophic failure events. Two masses of rock in the Cascade River Valley show precursory signs of potential catastrophic failures of up to c. 2 km³; a similar mass may threaten the town of Franz Josef.     

Relationships between glacier and rock glacier in the Maritime Alps, Schiantala Valley, Italy

In the Schiantala Valley of the Maritime Alps, the relationship between a till-like body and a contiguous rock glacier has been analyzed using geomorphologic, geoelectric and ice-petrographic methodologies. DC resistivity tomographies undertaken in the till and in the rock glacier show the presence of buried massive ice and ice-rich sediments, respectively. Ice samples from a massive ice outcrop show spherical gas inclusions and equidimensional ice crystals that are randomly orientated, confirming the typical petrographic characteristics of sedimentary ice. The rock glacier formation began after a phase of glacier expansion about 2550 ± 50 ¹⁴C yr BP. Further ice advance during the Little Ice Age (LIA) overrode the rock glacier root and caused partial shrinkage of the pre-existing permafrost. Finally, during the 19th and 20th centuries, the glacial surface became totally debris covered. Geomorphological and geophysical methods combined with analyses of ice structure and fabric can effectively interpret the genesis of landforms in an environment where glaciers and permafrost interact. Ice petrography proved especially useful for differentiating ice of past glaciers versus ice formed under permafrost conditions. These two mechanisms of ice formation are common in the Maritime Alps where many sites of modern rock glaciers were formerly occupied by LIA glaciers.     

Rock avalanches and other landslides in the central Southern Alps of New Zealand: a regional study considering possible climate change impacts

Slope instabilities in the central Southern Alps, New Zealand, are assessed in relation to their geological and topographic distribution, with emphasis given to the spatial distribution of the most recent failures relative to zones of possible permafrost degradation and glacial recession. Five hundred nine mostly late-Pleistocene- to Holocene-aged landslides have been identified, affecting 2% of the study area. Rock avalanches were distinguished in the dataset, being the dominant failure type from Alpine slopes about and east of the Main Divide of the Alps, while other landslide types occur more frequently at lower elevations and from schist slopes closer to the Alpine Fault. The pre-1950 landslide record is incomplete, but mapped failures have prevailed from slopes facing west–northwest, suggesting a structural control on slope failure distribution. Twenty rock avalanches and large rockfalls are known to have fallen since 1950, predominating from extremely steep east–southeast facing slopes, mostly from the hanging wall of the Main Divide Fault Zone. Nineteen occurred within 300 vertical metres above or below glacial ice; 13 have source areas within 300 vertical metres of the estimated lower permafrost boundary, where degrading permafrost is expected. The prevalence of recent failures occurring from glacier-proximal slopes and from slopes near the lower permafrost limit is demonstrably higher than from other slopes about the Main Divide. Many recent failures have been smaller than those recorded pre-1950, and the influence of warming may be ephemeral and difficult to demonstrate relative to simultaneous effects of weather, erosion, seismicity, and uplift along an active plate margin.     

Avalanche Defence Strategies and Monitoring of Two Sites in Mountain Permafrost Terrain, Pontresina, Eastern Swiss Alps

Snow-supporting avalanche defence structures are increasingly being built at high altitudes in potential permafrost areas. Special construction methods and guidelines have been developed to ensure a minimal stability of the structures, which have a vital role in the protection of underlying settlements and transport infrastructure against snow avalanches. If the avalanche slopes are located on ice-rich permafrost terrain, as is the case in a steep avalanche gully above Pontresina (Eastern Swiss Alps), other means of protection must be used – such as deflection or retention dams – as construction on ice-rich sediments can be very problematic. Experimental snow-supporting structures were built in 1997 in order to test different types of structures and their foundations, to develop specially adapted construction methods and to monitor the long-term behaviour of the structures in moderately creeping frozen ground with volumetric ice contents under 20%. Snow-nets were found to be the most suitable type of protection against avalanches in this type of permafrost terrain due to their deformability and because they are well adapted to rock fall. The structures do not improve slope stability but contribute towards maintaining permafrost as they delay snow melt by modifying the spatial and temporal distribution of the snow cover. The results of the project described have led to a better understanding of permafrost-related avalanche defence problems.     

The July 2007 rock and ice avalanches at Mount Steele, St. Elias Mountains, Yukon, Canada

A large rock and ice avalanche occurred on the north face of Mount Steele, southwest Yukon Territory, Canada, on July 24, 2007. In the days and weeks preceding the landslide, several smaller avalanches initiated from the same slope. The ice and rock debris traveled a maximum horizontal distance 5.76 km with a maximum vertical descent of 2,160 m, leaving a deposit 3.66 km² in area on Steele Glacier. The seismic magnitude estimated from long-period surface waves (M _s) is 5.2. Modeling of the waveforms suggests an estimated duration of approximately 100 s and an average velocity of between 35 and 65 m/s. This landslide is one of 18 large rock avalanches known to have occurred since 1899 on slopes adjacent to glaciers in western Canada. We describe the setting, reconstruct the event chronology and present a preliminary characterization of the Mount Steele ice and rock avalanches based on field reconnaissance, analysis of seismic records and an airborne LiDAR survey. We also present the results of a successful dynamic simulation for the July 24 event.     

Be exposure ages of a rock avalanche and a late glacial moraine in Alta Valtellina, Italian Alps

A rock avalanche deposit was investigated in order to understand the chronological evolution of geological hazards and to evaluate the interaction of the triggering geodynamic processes in the valley Val Viola, Italian Alps. The deposit is situated west of the Alpe Dosdé, in a permafrost area with deep-seated gravitational deformations (DSGD) along a tectonic line. Based on its geomorphologic context, the rock avalanche was first interpreted as a result of slope stress release without exact timing. This hypothesis was tested by measuring the ¹⁰Be exposure date of quartz from one boulder from the rock avalanche. The age of 7430±460 years places the event in the early Holocene. The timing of the last deglaciation was constrained using the inner late glacial moraine of a moraine doublet in the valley Alpe Dosdé situated at an altitude between 2140 and 2120 m a.s.l. west of the rock avalanche. The ¹⁰Be concentrations of quartz yield minimum exposure ages of 11,480±670 and 10,850±820 years. Different proposals for potential triggering factors of the rock avalanche include (a) melting of the local valley glacier and slope stress release in the Val Viola, likely to play a minor role as trigger, because of the time delay between the deglaciation and the rock avalanche event. More likely are (b) enhanced crustal seismicity induced by post-glacial regional isostatic glacial rebound coupled with tectonic stress or/and (c) climate conditions with higher temperatures around 7430±460 years, resulting in an upwards movement of the permafrost limit and destabilization of the rock walls.     

A giant avalanche on K2 mount,Karakorum

On September 16th, 1986, an ice avalanche from a hanging glacier near the K2 peak at 7800 m asl, Karakorum, triggered a massive avalanche of ice and snow. Ice and snow, impacting on the path, formed a dust cloud at the advancing tip. Grounding on the firn basin surface, ice and snow broke into fine powder and covered the whole basin. Fine powder of the dust cloud rose up to 500–600 m and drifted 4–5 km away. On the basis of field observations and measurements, topography and weather, conditions of the avalanche formation are analyzed. Judging by the data obtained, the avalanche was extremely large, its vertical descend being 2500 m, the maximum motion speed 124 m/s, volume of the avalanche mass 2 × 10⁵ m³ to 10⁷ m³, and impact pressure, as the avalanche grounded, 2.3 × 10⁶ Pa. It could have been one of the largest avalanches ever recorded, causing danger for mountaineering and expedition activities in this area.     

青藏高原冰崩隐患发育分布规律及危险性

随着全球气候变暖，青藏高原冰崩灾害日益加剧.通过大量遥感解译及数据分析，系统查明青藏高原冰崩隐患数量、类型、发育规律及危险性:(1)40 269条冰川共发育冰崩隐患581处.按失稳方式分为滑移式和崩落式；按成灾模式分为冰崩直接灾害、冰崩-堵江溃决和冰崩-冰湖溃决灾害.(2)冰崩敏感坡度40°~50°，集中分布高程为4 500~5 500 m，坡向具有“亲北性”.(3)区域分布差异大.西藏和新疆区域分布共占89.5%，雅鲁藏布江和塔里木河流域分布共占80.4%，念青唐古拉山脉和横断山脉分布共占49.4%.(4)空间分异明显.冰崩前缘高程以喜马拉雅东构造结为界，以西呈自西向东增大的趋势，以东呈先减小后增大的“V”型趋势，40.1%的冰崩前缘高程4 500~5 000 m、位于雪线附近，受山脉控制具有气候带交界“群聚性”特点.(5)高危险的冰崩隐患点36处、中等危险215处、低危险330处.      

Posteruption glacier development within the crater of Mount St. Helens, Washington, USA

The cataclysmic eruption of Mount St. Helens on May 18, 1980, resulted in a large, north-facing amphitheater, with a steep headwall rising 700 m above the crater floor. In this deeply shaded niche a glacier, here named the Amphitheater glacier, has formed. Tongues of ice-containing crevasses extend from the main ice mass around both the east and the west sides of the lava dome that occupies the center of the crater floor. Aerial photographs taken in September 1996 reveal a small glacier in the southwest portion of the amphitheater containing several crevasses and a bergschrund-like feature at its head. The extent of the glacier at this time is probably about 0.1 km². By September 2001, the debris-laden glacier had grown to about 1 km² in area, with a maximum thickness of about 200 m, and contained an estimated 120,000,000 m³ of ice and rock debris. Approximately one-third of the volume of the glacier is thought to be rock debris derived mainly from rock avalanches from the surrounding amphitheater walls. The newly formed Amphitheater glacier is not only the largest glacier on Mount St. Helens but its aerial extent exceeds that of all other remaining glaciers combined.     

Extremely large rockslides and rock avalanches in the Tien Shan Mountains, Kyrgyzstan

Most systematic research on large rock-slope failures is geographically biased towards reports from Europe, the Americas, the Himalayas and China. Although reports exist on large rockslides and rock avalanches in the territory of the former Soviet Union, they are not readily available, and few translations have been made. To begin closing this gap, we describe here preliminary data from field reconnaissance, remote sensing and geomorphometry of nine extremely large rock-slope failures in the Tien Shan Mountains of central Kyrgyzstan. Each of these catastrophic and prehistoric failures exceeds an estimated 1 km³ in volume, and two of them involve about 10 km³. Failure of rock slopes in wide valleys favoured the emplacement of hummocky long-runout deposits, often spreading out over >10 km², blocking major rivers. Most of these gigantic slope failures are located on or near active faults. Their spatial clustering and the high seismic activity in the Tien Shan support the hypothesis that strong seismic shaking caused or triggered most of these large-scale rock-slope failures. Nevertheless detailed field studies and laboratory analyses will be necessary to exclude hydroclimatic trigger mechanisms (precipitation, fluvial undercutting, permafrost degradation), and to determine their absolute ages, frequency and the large-landslide hazard of central Kyrgyzstan.     

The Keylong Serai rock avalanche, NW Indian Himalaya: geomorphology and palaeoseismic implications

This paper describes the geomorphology of rock avalanche deposits that resulted from a major mountain slope failure at Keylong Serai on the north slope of the Indian High Himalaya, an area of high altitude desert. Cosmogenic ¹⁰Be exposure ages of the widespread deposits indicate their formation 7,510 ± 110 years BP. Proxy records for this region of the Himalaya imply a similar dry climatic regime to the present day at this time, suggesting that precipitation was an unlikely trigger for this rock avalanche. An alternative mechanism associated with rock-wall stress relaxation is also unlikely, given the earlier timing of deglaciation in this area. Given the enormous volume of debris generated by this event, the most likely trigger for this mountain collapse and resultant rock avalanche is high ground acceleration during a great earthquake (M > 8). It is proposed that rock avalanches can be used to extend the limited palaeoseismic record and improve information on the recurrence interval of great earthquakes within the Himalaya arc.     

高速远程冰-岩碎屑流研究进展

冰-岩碎屑流是高寒山区陡峭山体斜坡区冰崩、岩崩或滑坡解体后形成的冰屑、岩块和土颗粒混合体高速流动现象.由于裹挟了冰屑,冰-岩碎屑流具有超强的运动性,屡屡引发震惊世人的灾难性事件,是全球气候变暖大背景下地质灾害研究的热点与前沿问题.通过对近40余年来的研究进展进行梳理和评述,指出了冰-岩碎屑流的概念由来和主流定义方法,阐述了其成因机制的气候敏感性,结合典型实例论述了区域发育特征,重点分析了运动特征、减阻机理和冰屑影响机制.冰-岩碎屑流的超强运动性被认为与低摩擦冰减阻机理、摩擦热融减阻机理、侧限约束减阻机理密切相关.冰屑作为材料组分和融水来源,能够降低界面摩擦、改变冰-水-岩相互作用,进而形成复杂的热-水-力耦合作用.今后应加强研究冰-岩碎屑流事件的成因机制和时空分布规律、运动特性和冰屑影响机制、过程演化观测与预警评估技术,以期揭示冰-岩碎屑流运动机理,为冰-岩碎屑流及链生灾害的科学减灾提供有力支撑.      

The 2020 glacial lake outburst flood process chain at Lake Salkantaycocha (Cordillera Vilcabamba,Peru)

Glacial lakes represent a threat for the populations of the Andes and numerous disastrous glacial lake outburst floods (GLOFs) occurred as a result of sudden dam failures or dam overtoppings triggered by landslides such as rock/ice avalanches into the lake. This paper investigates a landslide-triggered GLOF process chain that occurred on February 23, 2020, in the Cordillera Vilcabamba in the Peruvian Andes. An initial slide at the SW slope of Nevado Salkantay evolved into a rock/ice avalanche. The frontal part of this avalanche impacted the moraine-dammed Lake Salkantaycocha, triggering a displacement wave which overtopped and surficially eroded the dam. Dam overtopping resulted in a far-reaching GLOF causing fatalities and people missing in the valley downstream. We analyze the situations before and after the event as well as the dynamics of the upper portion of the GLOF process chain, based on field investigations, remotely sensed data, meteorological data and a computer simulation with a two-phase flow model. Comparison of pre- and post-event field photographs helped us to estimate the initial landslide volume of 1–2 million m³. Meteorological data suggest rainfall and/or melting/thawing processes as possible causes of the landslide. The simulation reveals that the landslide into the lake created a displacement wave of 27 m height. The GLOF peak discharge at the dam reached almost 10,000 m³/s. However, due to the high freeboard, less than 10% of the lake volume drained, and the lake level increased by 10–15 m, since the volume of landslide material deposited in the lake (roughly 1.3 million m³) was much larger than the volume of released water (57,000 m³, according to the simulation). The model results show a good fit with the observations, including the travel time to the uppermost village. The findings of this study serve as a contribution to the understanding of landslide-triggered GLOFs in changing high-mountain regions.

     

Magnitude and frequency relations: are there geological constraints to the rockfall size?

There exists a transition between rockfalls, large rock mass failures, and rock avalanches. The magnitude and frequency relations (M/F) of the slope failure are increasingly used to assess the hazard level. The management of the rockfall risk requires the knowledge of the frequency of the events but also defining the worst case scenario, which is the one associated to the maximum expected (credible) rockfall event. The analysis of the volume distribution of the historical rockfall events in the slopes of the Solà d’Andorra during the last 50 years shows that they can be fitted to a power law. We argue that the extrapolation of the F-M relations far beyond the historical data is not appropriate in this case. Neither geomorphological evidences of past events nor the size of the potentially unstable rock masses identified in the slope support the occurrence of the large rockfall/rock avalanche volumes predicted by the power law. We have observed that the stability of the slope at the Solà is controlled by the presence of two sets of unfavorably dipping joints (F3, F5) that act as basal sliding planes of the detachable rock masses. The area of the basal sliding planes outcropping at the rockfall scars was measured with a terrestrial laser scanner. The distribution of the areas of the basal planes may be also fitted to a power law that shows a truncation for values bigger than 50 m² and a maximum exposed surface of 200 m². The analysis of the geological structure of the rock mass at the Solà d’Andorra makes us conclude that the size of the failures is controlled by the fracture pattern and that the maximum size of the failure is constrained. Two sets of steeply dipping faults (F1 and F7) interrupt the other joint sets and prevent the formation of continuous failure surfaces (F3 and F5). We conclude that due to the structural control, large slope failures in Andorra are not randomly distributed thus confirming the findings in other mountain ranges.     

On the sensitivity of Holocene talus-derived rock glaciers to climate change in the Ben Ohau Range,New Zealand

The morphology and surface ages of talus-derived rock glaciers are investigated to establish the timing of rock glacier formation in the central Southern Alps. Samples of rock weathering rinds show that all rock glaciers studied were formed during the Neoglacial period, but differences exist between sites in the number of new rock glacier lobes formed by Holocene climatic fluctuations. A qualitative conceptual model is proposed to explain rock glacier formation in terms of two thresholds. An external threshold relates to the presence of a cool climate capable of allowing internal ice to form within talus slopes. An internal threshold relates to the presence of sufficiently thick talus at a site to generate a shear stress capable of overcoming internal friction within the talus/ice mass. The model produces a non-steady-state response to explain why unmodified talus, single-lobed and double-lobed rock glaciers developed at adjacent sites under the same climatic regime. Individual landforms have different sensitivities to formation, which depend partly on the previous history of talus accumulation and rock glacier activity at a site. The model demonstrates how successive cool climate periods may be fully represented by rock glacier lobes at sensitive sites but under-represented at insensitive sites. Sensitivity (and therefore climatic representativeness) is favoured by high rates of debris supply. By implication, the timing of formation of rock glacier lobes in regions of prolonged cool climate and low debris production is less likely to correspond to the timing of climatic cooling and more likely to follow the ‘rules’ of deterministic chaos.     

Chronology of glaciation and deglaciation during the Loch Lomond (Younger Dryas) Stade in the Scottish Highlands: implications of recalibrated 10Be exposure ages

Considerable uncertainty surrounds the timing of glacier advance and retreat during the Younger Dryas or Loch Lomond Stade (LLS) in the Scottish Highlands. Some studies favour ice advance until near the end of the stade (c. 11.7 ka), whereas others support the culmination of glacier advance in mid‐stade (c. 12.6–12.4 ka). Most published ¹⁰ Be exposure ages reported for boulders on moraines or deglacial sites post‐date the end of the LLS, and thus appear to favour the former view, but recalibration of 33 ¹⁰ Be ages using a locally derived ¹⁰ Be production rate and assuming rock surface erosion rates of zero to 1 mm ka^?1 produces exposure ages 130–980 years older than those originally reported. The recalibrated ages are filtered to exclude anomalous data, and then employed to generate aggregate probability density distributions for the timing of moraine deposition and deglaciation. The results suggest that the most probable age for the timing of the deposition of the sampled outermost moraines lies in the interval 12.4–12.1 ka or earlier. Deglacial ages obtained for sites inside Loch Lomond Stadial glacier limits imply that glaciers at some or all of the sampled sites were retreating prior to 12.1 ka. Use of aggregated data does not exclude the possibility of asynchronous glacier behaviour at different sites, but confirms that some glaciers reached their maximum limits and began to retreat several centuries before the rapid warming that terminated the LLS at 11.7–11.6 ka, consistent with the retrodictions of recent numerical modelling experiments and with geomorphological evidence for gradual oscillatory ice‐margin retreat under stadial conditions.     

Rock falls in the Mont Blanc Massif in 2007 and 2008

Due to a lack of systematic observations, the intensity and volume of rock falls and rock avalanches in high mountain areas are still poorly known. Nevertheless, these phenomena could have burly consequences. To document present rock falls, a network of observers (guides, mountaineers, and hut wardens) was initiated in the Mont Blanc Massif in 2005 and became fully operational in 2007. This article presents data on the 66 rock falls (100 m³?≤?V?≤?50,000 m³) documented in 2007 (n?=?41) and 2008 (n?=?25). Most of the starting zones are located in warm permafrost areas, which are most sensitive to warming, and only four rock falls are clearly out of permafrost area. Different elements support permafrost degradation as one of the main triggering factors of present rock falls in high mountain areas.     

Exposure dating and reinterpretation of coarse debris accumulations (‘rock glaciers’) in the Cairngorm Mountains,Scotland

Relict rock glaciers have considerable potential for contributing to palaeoclimatic reconstruction, but this potential is often undermined by lack of dating control and problems of interpretation. Here we reinvestigate and date four proposed ‘rock glaciers’ in the Cairngorm Mountains and show that the morphology of only one of these appears consistent with that of a true rock glacier produced by creep of underlying ice or ice‐rich sediment. All four features comprise rockslide or rock avalanche runout debris, and the possibility that all four represent unmodified runout accumulations cannot be discounted. Surface exposure dating of the four debris accumulations using cosmogenic ¹⁰Be produced uncertainty‐weighted mean ages of 15.4 ± 0.8 ka, 16.2 ± 1.0 ka, 12.1 ± 0.6 ka and 12.7 ± 0.8 ka. All four ages imply emplacement under cold stadial conditions, two prior to the Windermere Interstade of ca. 14.5–12.9 cal. ka BP and two during the Loch Lomond Stade of ca. 12.9–11.5 cal. ka BP. The above ages indicate that paraglacial rock‐slope failure on granite rockwalls occurred within a few millennia after deglaciation. The mean exposure ages obtained for runout debris at two sites – Strath Nethy (16.2 ± 1.0 ka) and Lairig Ghru (15.4 ± 0.8 ka) – are consistent with basal radiocarbon ages from Loch Etteridge, 22 km to the southwest (mean = 15.6 ± 0.3 cal. ka BP) and imply widespread deglaciation of the Cairngorms and adjacent valleys before 15 ka and possibly 16 ka. Copyright © 2008 John Wiley & Sons, Ltd.     

Sedimentary facies and landform genesis at a temperate outlet glacier: Soler Glacier, North Patagonian Icefield

This paper focuses on the structural glaciology, dynamics, debris transport paths and sedimentology of the forefield of Soler Glacier, a temperate outlet glacier of the North Patagonian Icefield in southern Chile. The glacier is fed by an icefall from the icefield and by snow and ice avalanches from surrounding mountain slopes. The dominant structures in the glacier are ogives, crevasses and crevasse traces. Thrusts and recumbent folds are developed where the glacier encounters a reverse slope, elevating basal and englacial material to the ice surface. Other debris sources for the glacier include avalanche and rockfall material, some of which is ingested in marginal crevasses. Debris incorporated in the ice and on its surface controls both the distribution of sedimentary facies on the forefield and moraine ridge morphology. Lithofacies in moraine ridges on the glacier forefield include large isolated boulders, diamictons, gravel, sand and fine-grained facies. In relative abundance terms, the dominant lithofacies and their interpretation are sandy boulder gravel (ice-marginal), sandy gravel (glaciofluvial), angular gravel (supraglacial) and diamicton (basal glacial). Proglacial water bodies are currently developing between the receding glacier and its frontal and lateral moraines. The presence of folded sand and laminites in moraine ridges in front of the glacier suggests that, during a previous advance, Soler Glacier over-rode a former proglacial lake, reworking lacustrine deposits. Post-depositional modification of the landform/sediment assemblage includes melting of the ice-core beneath the sediment cover, redistribution of finer material across the proglacial area by aeolian processes and fluvial reworking. Overall, the preservation potential of this landform/sediment assemblage is high on the centennial to millennial timescale.