Solifluction Lobes Research Articles

CO 2 sublimation in Martian gullies: laboratory experiments at varied slope angle and regolith grain sizes

Abstract Martian gullies were initially hypothesized to be carved by liquid water, due to their resemblance to gullies on Earth. Recent observations have highlighted significant sediment transport events occurring in Martian gullies at times and places where CO 2 ice should be actively sublimating. Here we explore the role of CO 2 sublimation in mobilizing sediment through laboratory simulation. In our previous experimental work, we reported the first observations of sediment slope movement triggered by the sublimation of CO 2 frost. We used a Mars regolith simulant near the angle of repose. The current study extends our previous work by including two additional substrates, fine and coarse sand, and by testing slope angles down to 10°. We find that the Mars regolith simulant is active down to 17°, the fine sand is active only near the angle of repose and the coarse sand shows negligible movement. Using an analytical model, we show that under Martian gravity motion should be possible at even lower slope angles. We conclude that these mass-wasting processes could be involved in shaping Martian gullies at the present day and intriguingly the newly reported CO 2 -creep process could provide an alternative explanation for putative solifluction lobes on Mars.

Periglacial environment in Nepal Himalaya: Present contexts and future prospects

Periglacial environment in the Nepal Himalaya (80°04’ to 88°12’ E longitude and 26°22’ to 30°27’ N latitude) is a research field that has received a little scientific attention although the first reported periglacial research was in 1958. After the first periglacial research, only 22 studies are reported in Nepal (area: 147,181 km2), most of which is carried out by researchers outside the country. Studies mainly focus on periglacial landforms and determining the lower limit of the mountain permafrost. The mean lower limit of permafrost (LLP) and the size of rock glaciers indicate a decreasing trend of the permafrost limit from the eastern (5239 m a.s.l.) to the western part of Nepal (4513 m a.s.l.). The rate of change in the LLP in response to climate change in Nepal Himalaya is 1.3–2.6 m/yr. Model on the scenario of permafrost change based on the IPCC climate scenarios shows that the LLP would rise by 188 m between 2009 and 2039 with the rise in temperature. The periglacial landforms, like vegetated patterned ground (earth hummocks, turf banked terraces), sorted polygons, sorted stripes, solifluction lobes, striated ground, and rock glaciers are reported from the Nepal Himalaya. The spatial and temporal coverage of periglacial research in Nepal Himalaya is very low. The arena of periglacial researches, like permafrost distribution modelling, periglacial hazards, periglacial ecology, relationships between permafrost and rangeland, and implication on mountain livelihood, global warming and periglacial change are the potential areas of research in the coming days.

Solifluction rates and environmental controls at local and regional scales in central Austria

ABSTRACTSolifluction is a widespread periglacial phenomenon. Little is known about present solifluction rates in Austria. The author monitored five solifluction lobes during a four-year period. Annual rates of surface velocity, vertical velocity profiles, depths of movement, and volumetric velocities were quantified using near-surface markers and painted lines. Environmental conditions were assessed using air temperature, soil texture, and ground temperature-derived parameters. The latter were used to estimate the relevance of needle-ice creep, diurnal frost creep, annual frost creep, and gelifluction. The mean surface velocity rates were 3.5–6.1 cm yr−1 (near-surface markers) and 6.2–8.9 cm yr−1 (painted lines), respectively, indicating a high relevance of needle-ice creep. The mean depth of movement was 32.5–40 cm. The mean volumetric velocities were 71–102 cm3 cm−1 yr−1. Solifluction rates at the five sites did not correlate with each other due to site-specific controls. No statistically significant correlations were quantified between solifluction rates and different environmental parameters due to data gaps and short time series, thus highlighting the importance of long-term monitoring. Nevertheless, the results suggest that longer zero curtain periods, longer seasonal ground thawing periods, later start of the seasonal snow cover, more freeze-thaw cycles, and cooler early summer temperatures promote solifluction.

Diurnal to Decadal Changes in the Balance between Vegetation and Bare Ground in Tasmanian Fjaeldmark

ABSTRACTPeriglacial processes are active under current climatic conditions on the more exposed peaks and ridges of Tasmania’s high country. Non-sorted steps, stripes, and solifluction lobes with vegetated risers and bare treads have formed on many of the mountains capped in fissile sedimentary rocks. Any disturbance to the balance between vegetation and bare ground can result in biogeomorphic feedbacks leading to an increase or decrease in periglacial activity and thereby threaten the survival of fjaeldmark. We tested the hypotheses that vegetation helps create risers by capturing material moved by needle ice, water, and wind, and that the balance between vegetation and bare ground in fjaeldmark is dynamic in Tasmania at the decadal time scale. Repeat photo plots and temperature data loggers were employed to monitor the dynamism of two non-sorted lobes on Mount Rufus over a seven-month period. Diurnal freeze/thaw cycles resulted in needle ice formation on the bare treads and promoted downslope movement of the surface layer through frost creep. Vegetation was observed to reduce geomorphic activity and to capture soil and clasts transported downslope, thereby steepening the risers. Aerial photographic analysis showed a 0.065% per annum increase in vegetation cover in fjaeldmark since the mid-20th century. Mountains that had a high number of days with snow cover were especially prone to increases in vegetation cover. Decline in vegetation cover occurred on some mountains burned during the past century. The smallest changes occurred on the most exposed peaks and ridges.

Syngenetic dynamic of permafrost of a polar desert solifluction lobe, Ward Hunt Island, Nunavut

Repeated freeze–thaw cycles on slopes trigger sorting and solifluction mass movements, while subsequent displacement of material modifies the geomorphology of slopes as well as permafrost dynamics. This study focuses on the geomorphology and the cryostratigraphy of a polar desert stone-banked solifluction lobe with the objective to clarify the impact of slow mass movements on ground ice aggradation. The morphology of the solifluction lobe was characterized by peripheral ridges of coarse gravel, partially surrounding a depression filled with finer sediments saturated with water and covered by organics. Cryostratigraphic analysis demonstrated that the solifluction lobe’s formation led to the development of a syngenetic layer of permafrost with an ice content that varied according to the location in the lobe. The ice-rich cryofacies formed in the central depression of the lobe should act as a buffer to potential active layer deepening, slowing down its thawing, whereas the ice-poor cryofacies formed under the ridges is expected to thaw faster than the central depression under climate warming scenarios. Thawing of the ice-rich zone in the future will result in differential thaw subsidence between the ridges and the central depression of solifluction lobes, along with increased drainage through the ridges and subsequent changes in hydrology.

Solifluction meets vegetation: the role of biogeomorphic feedbacks for turf‐banked solifluction lobe development

AbstractVegetation is an important factor influencing solifluction processes, while at the same time, solifluction processes and landforms influence species composition, fine‐scale distribution and corresponding ecosystem functioning. However, how feedbacks between plants and solifluction processes influence the development of turf‐banked solifluction lobes (TBLs) and their geomorphic and vegetation patterns is still poorly understood. We addressed this knowledge gap in a detailed biogeomorphic investigation in the Turtmann glacier foreland (Switzerland). Methods employed include geomorphic and vegetation mapping, terrain assessment with unmanned aerial vehicle (UAV) and temperature logging. Results were subsequently integrated with knowledge from previous geomorphic and ecologic studies into a conceptual model. Our results show that geomorphic and vegetation patterns at TBLs are closely linked through the lobe elements tread, risers and ridge. A conceptual four‐stage biogeomorphic model of TBL development with ecosystem engineering by the dwarf shrub Dryas octopetala as the dominant process can explain these interlinked patterns. Based on this model, we demonstrate that TBLs are biogeomorphic structures and follow a cyclic development, during which the role of their components for engineer and non‐engineer species changes. Our study presents the first biogeomorphic model of TBL development and highlights the applicability and necessity of biogeomorphic approaches and research in periglacial environments. Copyright © 2016 John Wiley & Sons, Ltd.

Spatial Controls of Turf-Banked Solifluction Lobes and Their Role for Paraglacial Adjustment in Glacier Forelands

In glacier forelands, solifluction is a major and fast-responding paraglacial process in the adjustment of low- or moderately-inclined moraine slopes. However, the spatial pattern of the factors that control solifluction and their interactions are poorly understood. In this study, we combine geomorphic and vegetation mapping, analysis of borehole material and time domain reflectometry with two-dimensional (2D) and three-dimensional (3D) electrical resistivity tomography (ERT) to quantify the controlling factors and evaluate their influence on sediment transport. The investigated turf-banked solifluction lobe is located on the distal slope of a 1920s lateral moraine in the foreland of the Turtmann glacier in the southern Swiss Alps. Our data demonstrate the interaction between material, soil moisture and vegetation, which results in geomorphometric features such as (i) frontal and lateral risers, (ii) a lobe tread and (iii) a ridge. Lobe size indicates intense solifluction movement in the last 100 years. The interaction of controlling factors results in a negative feedback which stabilises the lobe and, thus, limits paraglacial sediment transport to frost heave processes on the ridge. Copyright © 2016 John Wiley & Sons, Ltd.

Stone‐banked lobes as a product of mild freeze–thaw action: an example from western tasmania, australia

This paper interprets a stone‐banked lobe on the upper western face of Mt Rufus, at an altitude of 1380 m in western Tasmania, Australia. The morphology of the deposit resembles that of a solifluction lobe. Field observations show vertical and downslope movement of pebbles, cobbles and small boulders over a single winter season. The movement is largely related to frost pull (10–15 cm) and shallow freeze–thaw processes promoting the downslope (up to 50 cm yr–1) creep of material and the accumulation of coarse clasts at the lobe riser. The climate of Mt Rufus is strongly maritime and this is reflected in the limited duration and depth of penetration of frozen ground at this site during the 2013 winter. Despite the relatively mild climatic conditions, freeze–thaw processes are clearly the dominant geomorphic force operating at the site.These findings support observations of active stone‐banked lobes on sub‐Antarctic islands where intense freezing is absent. Both there and at Mt Rufus, movement is dominated by freeze–thaw processes operating in the upper c. 20 cm of the regolith. These are typical landforms of marginal freeze–thaw settings.

火星表面の永久凍土と周氷河作用

Following the development of high-resolution imaging, digital elevation models, thermal and hydrological data, and onsite ground information during the early period of the 21st century, the periglacial geomorphology of the Martian surface advanced rapidly. Images can even resolute meter-scale landforms, enabling identification of most periglacial features and analysis of their global distributions and detailed morphologies. This review focuses on progress in research covering permafrost distribution, patterned ground, possible heave and subsidence features, lobate debris forms, and slope-lineated features during the last decade. Most of the Martian high-latitude surface is underlain by ice-rich ground called the latitude-dependent mantle (LDM), which favors permafrost-related features possibly developed under warm-humid conditions during past high-obliquity periods or partially s,till active under the present cold-dry conditions. Thermal contraction cracking is likely to prevail in the LDM, resulting in high-centered, flat-top polygons, possibly underlain by sublimation-type wedges or sand wedges that prevail at high latitudes. The surface patterns change into subdued or peak-top polygons toward the mid-latitudes, probably reflecting long-term sublimation of the LDM. Some researchers attribute stone circles to sorting due to freeze-thaw, but the features are much larger than candidates on the Earth. Small isolated domes with concentric cracks or craters at the top may include pingos, which also prevail at high- to mid-latitudes. Asymmetrical scalloped depressions may result from sublimation or thawing of the LDM, but there is a debate between pole-ward and equator-ward slope retreats. Lobate debris aprons may originate from creep of ice-rock mixtures or debris-covered glaciers, but the distinction between the two origins is unclear, as in the long-lasting debate on terrestrial candidates. Some thin, smaller debris lobes at high latitudes resemble stone-banked solifluction lobes on the Earth, which may indicate the occurrence of seasonal freeze-thaw cycles in the recent past. Time-series images indicate active slope features, including gullies, slope streaks, and recurrent slope lineaes that develop below cliffs. These active features may originate from outflows of brine that thaws far below the melting point of water ice.

Glacial and periglacial geomorphology and its paleoclimatological significance in three North Ethiopian Mountains, including a detailed geomorphological map

Geomorphological investigations and detailed mapping of past and present (peri)glacial landforms are required in order to understand the impact of climatic anomalies. The Ethiopian Highlands show a great variety in past and contemporary climate, and therefore, in the occurrence of glacial and periglacial landforms. However, only a few mountain areas have been studied, and detailed geomorphological understanding is lacking. In order to allow a fine reconstruction of the impact of the past glacial cycle on the geomorphology, vegetation complexes, and temperature anomalies, a detailed geomorphological map of three mountain areas (Mt. Ferrah Amba, 12°51′N 39°29′E; Mt. Lib Amba, 12°04′N 39°22′; and Mt. Abuna Yosef, 12°08′N 39°11′E) was produced. In all three study areas, inactive solifluction lobes, presumably from the Last Glacial Maximum (LGM), were found. In the highest study area of Abuna Yosef, three sites were discovered bearing morainic material from small late Pleistocene glaciers. These marginal glaciers occurred below the modeled snowline and existed because of local topo-climatic conditions. Evidence of such Pleistocene avalanche-fed glaciers in Ethiopia (and Africa) has not been produced earlier. Current frost action is limited to frost cracks and small-scale patterned ground phenomena. The depression of the altitudinal belts of periglacial and glacial processes during the last cold period was assessed through periglacial and glacial landform mapping and comparisons with data from other mountain areas taking latitude into account. The depression of glacial and periglacial belts of approximately 600m implies a temperature drop around 6°C in the last cold period. This cooling is in line with temperature depressions elsewhere in East Africa during the LGM. This study serves as a case study for all the intermediate mountains (3500–4200m) of the North Ethiopian highlands.

Glacial geomorphology of the Tweedsmuir Hills, Central Southern Uplands, Scotland

The Quaternary glacial history of the Tweedsmuir Hills, Central Southern Uplands, Scotland, has received little attention since the 1980s, with earlier studies focussing on single lines of geomorphic evidence in isolated valleys. This study presents the first systematic glacial geomorphological assessment of the region, covering approximately 300 km2 with the map designed to be presented at A0. Mapping from remotely sensed imagery and field investigation reveal a large number of moraines and meltwater channels, both within valleys and occasionally extending to the plateau, alongside a range of peri- and para-glacial features, including solifluction lobes, alluvial fans, debris cones, river terraces and rock slope failures. Aspects of the mapped geomorphology are consistent with plateau icefield landsystems mapped elsewhere in Britain and this will hopefully form the basis for palaeoglaciological reconstructions which will improve our understanding of the extent and dynamics of former ice masses in the region.

Coasts of Foxe Basin, Arctic Canada

Abstract Foxe Basin is a down-faulted arctic basin floored by Palaeozoic carbonates, surrounded by metamorphic Precambrian terrains. Quaternary deposits consist of Pleistocene–Holocene glacial drift, and frost-shattered bedrock-clasts mostly reworked by sea waves during post-glacial emergence during the last 5000–6000 yr. The shallow, primarily micro- to meso-tidal sea is covered by ice for c. 9–10 months each year. This ensures that the overall energy of the coasts is low, although strong storm waves develop during ice-free periods. Puccinellia phryganodes dominated salt marshes occur on muddy and sandy shores and grade into inland sedge-forb wetlands and Dryas -dominated tundra. Cold climate processes active on the emerged land have generated typical features such as frost heaving of bedrock blocks, solifluction lobes on slopes, frost boils in flatter areas, frost shattering and solution of surficial carbonate pebbles, thermokarst lakes, and shallow Cryosols.

Depositional structure of solifluction lobe distributed on wind-beaten bare ground at northwest slope of Mt.Akaishi, Southern Japanese Alps

Depositional structure of solifluction lobe distributed on wind-beaten bare ground at northwest slope of Mt.Akaishi, Southern Japanese Alps

Morphological evidence for geologically young thaw of ice on Mars: A review of recent studies using high-resolution imaging data

Liquid water is generally only meta-stable on Mars today; it quickly freezes, evaporates or boils in the cold, dry, thin atmosphere (surface pressure is about 200 times lower than on Earth). Nevertheless, there is morphological evidence that surface water was extensive in more ancient times, including the Noachian Epoch (∼4.1 Ga to ∼3.7 Ga bp), when large lakes existed and river-like channel networks were incised, and early in the Hesperian Epoch (∼3.7 Ga to ∼2.9 Ga bp), when megafloods carved enormous channels and smaller fluvial networks developed in association with crater-lakes. However, by the Amazonian Epoch (∼3.0 Ga to present), most surface morphogenesis associated with liquid water had ceased, with long periods of water sequestration as ice in the near-surface and polar regions. However, inferences from observations using imaging data with sub-metre pixel sizes indicate that periglacial landscapes, involving morphogenesis associated with ground-ice and/or surface-ice thaw and liquid flows, has been active within the last few million years. In this paper, three such landform assemblages are described: a high-latitude assemblage comprising features interpreted to be sorted clastic stripes, circles and polygons, non-sorted polygonally patterned ground, fluvial gullies, and solifluction lobes; a mid-latitude assemblage comprising gullies, patterned ground, debris-covered glaciers and hillslope stripes; and an equatorial assemblage of linked basins, patterned ground, possible pingos, and channel-and-scarp features interpreted to be retrogressive thaw-slumps. Hypotheses to explain these observations are explored, including recent climate change, and hydrated minerals in the regolith ‘thawing’ to form liquid brines at very low temperatures. The use of terrestrial analogue field sites is also discussed.

A 35‐Year Record of Solifluction in a Maritime Periglacial Environment

ABSTRACTEight segmented PVC columns (Rudberg pillars) inserted vertically in the treads of three vegetation‐covered (‘turf‐banked’) solifluction lobes at altitudes of 912–1031 m in the Fannich Mountains of NW Scotland were exhumed 35 years after insertion, and downslope displacement of each segment was measured to derive velocity profiles for each site. Data from these profiles yielded average surface velocities of 7.8–10.6 mm a‐1 (mean 8.8 mm a‐1), average volumetric velocities of 8.3–13.3 cm3 cm‐1 a‐1 (mean 10.5 cm3 cm‐1 a‐1) and maximum displacement depths of 290–445 mm (mean 390 mm). Measured volumetric velocities for these maritime periglacial sites are fairly similar to those recorded in high alpine environments, but markedly less than most reported rates for solifluction in areas of warm permafrost or deep seasonal freezing. Movement affects only the uppermost parts of individual lobes, and the measured volumetric velocities imply either very slow advance of lobe fronts (~ 0.7 mm a‐1) or slow thickening and steepening of stationary lobe risers. Velocity profiles decline approximately exponentially with depth over the depth range 50–400 mm, consistent with movement by frost creep alone or frost creep plus gelifluction. Comparison with measured rates of periglacial mass transport elsewhere on British mountains suggests (1) that, contrary to traditional views, surface velocities are similar to (and may exceed) those of ploughing boulders in the same area, and (2) that both surface velocities and volumetric velocities are markedly less than at unvegetated sites where needle ice creep is the dominant component of solifluction. Copyright © 2012 John Wiley & Sons, Ltd.

A glacial geomorphological map of the Monadhliath Mountains, Central Scottish Highlands

The Monadhliath Mountains in the Central Scottish Highlands are dominated by an extensive plateau area that has received little Quaternary research attention during the last century. Previous studies have focussed on the geomorphology and sedimentology of isolated valleys and therefore the 1:57,500 map presented here provides the first systematic assessment of the glacial geomorphology of the region as a whole, covering an area of approximately 840 km2. Results of mapping from remotely sensed imagery and in the field reveal a large number of moraines and ice-marginal meltwater channels both within outlet valleys and on the plateau, alongside a wide range of glacial, periglacial and fluvial features including glaciolacustrine landforms and sediments, lake overflow channels, ice-contact fans, blockfields, solifluction lobes, alluvial fans, debris cones, river terraces and rock slope failures. The spatial distribution of the majority of landforms indicates that the region was dominated by at least one local plateau icefield glaciation. The map now provides a framework for further analysis, which will greatly improve understanding of the extent and dynamics of former ice masses in the region.

Periglacial mass-wasting landforms on Mars suggestive of transient liquid water in the recent past: Insights from solifluction lobes on Svalbard

On Earth, periglacial solifluction is a slow mass-wasting process related to freeze–thaw activity. We compare the morphology of small-scale lobate features on Mars to solifluction lobes in Svalbard to constrain their processes of formation. The analysis is based on high-resolution satellite imagery of Mars (HiRISE, ∼25cm/pxl), aerial images of Svalbard with a similar spatial resolution (HRSC–AX, ∼20cm/pxl) acquired through an air campaign in summer 2008, and ground truth obtained during two summer expeditions in 2009 and 2011 on Svalbard. We present a detailed study of two crater environments on Mars displaying two types of lobate forms, characterized as sorted (clast-banked) and non-sorted lobes. On both Svalbard and Mars such lobes typically occur as clusters of overlapping risers (lobe fronts), pointing to differential velocities in the soil. The martian small-scale lobes have well-defined arcuate risers and lobe treads (surface). Lobe widths range between 14 and 127m and tread lengths between 13 and 105m. Riser height is estimated to be approximately 1–5m. The lobes on Mars share the plan view morphology of solifluction lobes on Svalbard and their morphometry is within the range of values of terrestrial solifluction lobes. The lobes are distinct from permafrost-creep landforms such as rock glaciers. We show the results of a survey of 53 HiRISE images covering latitudes between 59°N and 81°N. Similar to Svalbard, the studied lobate features on Mars occur in close spatial proximity to gullies and thermal contraction polygons. The widespread distribution of the lobate forms in the northern hemisphere and their close association to ground-ice and gullies are best explained by mass-wasting processes related to frost creep, gelifluction and/or plug-like flow. This suggests a protracted process (thousand to several thousands of years) of freeze–thaw activity at the northern high latitudes on Mars. Age constraints on lobe deposits and superposition relationships with gullies and polygons imply a process involving liquid water within the last few million years.

Environmental changes in Northern Iceland since the Younger Dryas inferred from periglacial slope deposits

The slopes in Northern Iceland show the widespread occurrence of solifluction features, indicative of an active periglacial environment due to annual mean temperatures around 3°C at sea level and seasonal soil frost. In order to reconstruct periods with active and inactive solifluction in the past we excavated 18 solifluction lobes for analysing the sediment sequences. Dating of the sediments was realised mainly by tephrochronology and 14C. The oldest solifluction layer could be dated to the Younger Dryas (YD), just after the deglaciation of Northern Iceland. The early to mid Holocene up to the deposition of Hekla 3 Tephra (~3 ka BP) is characterized by the accumulation of loess and tephra layers, which show no signs of secondary remobilisation or erosion, indicating stable slopes during the mid-Holocene climatic optimum (MCO). After the deposition of Hekla 3 Tephra and especially during the ‘Little Ice Age’ (LIA), solifluction reappeared in the profiles as a probable consequence of Neoglacial cooling. The results fit well with other proxies from Iceland (glacier variations, pollen), from North Atlantic marine cores and from Greenland ice records.

UK Mars research and priorities in the Aurora programme

John Bridges and Axel Hagermann summarize an RAS Special Discussion Meeting in January 2011, which looked at the prospects for the UK exploring Mars. High-resolution imaging and near-infrared mapping of the martian surface, together with detailed studies of martian meteorites and exobiology research, have revealed an increasing amount of detail about how climate and surface processes have changed over the history of Mars. The exploration of Mars is now being planned through a joint NASA–ESA programme. New missions such as the Mars Science Laboratory in 2012 and the Trace Gas Orbiter in 2016 will also improve our understanding about the evolution of Mars. Mission planning is being guided by recent reports of methane in the Mars atmosphere and the identification of minerals and landforms associated with water such as the Eberswalde Delta. Mars research is also acting as a spur for the development of mission concepts and analytical techniques such as new XRD techniques, microRaman and a Life Marker Chip. The second UK in the Aurora Programme meeting was held on 14 January 2011 at Burlington House, London. The aim was to bring together researchers, particularly in the field of Mars research and instrumentation, in order to provide a platform to show our research and to discuss what the priorities for future missions within Aurora should be. The Aurora programme encapsulates Europe's current plans, aiming to send unmanned spacecraft to explore our neighbouring world to examine its climate, search for evidence of past or present life, and learn how conditions there relate to those on Earth. The meeting was introduced by Frederick Taylor (Oxford). High-resolution imagery of some of the surface of Mars using the HiRise camera on the Mars Reconnaissance Orbiter (MRO) at 25 cm/pixel has changed our view of the evolution of its surface and climate. One of the ways our view of Mars has changed is the recognition of the influence of glacial and periglacial activity in shaping landscapes. Matt Balme (Open University) and Peter Gallagher (Trinity College Dublin) presented new observations of periglacial landforms that appear to have been formed by water as part of freeze–thaw cycles: self-organized patterns of stone stripes, polygons, circles and clastic solifluction lobes. The low density of impact craters suggests these terrains formed in a geologically recent era. Kate Goddard et al. (Imperial College) presented a study of youthful gullies and depositional fans on Mars in Mojave Crater. Understanding the role of water or other processes, including CO 2 ice sublimation, in the formation of such gullies is a crucial way of reaching a more accurate understanding of martian climate variations within the last few million years. Balme and Gallagher speculated that because perchlorates (identified at the Phoenix landing site) have eutectic temperatures below 240 K and can remain liquid at temperatures far below the freezing point of water, perchlorate brines may explain freeze–thaw processes and could cause geomorphological changes.

Relict rock glaciers in Wasdale, western Lake District, northwest England: geofact or geofantasy

Field examination of four landforms in the Wasdale area of the western Lake District that have previously been classified as relict rock glaciers indicates that such designation is no longer appropriate. Two of the features consist of bedrock with clusters of locally derived boulders; another is largely the product of glacial deposition with some evident fluvial modification; the fourth resembles a series of solifluction lobes, which may also have undergone some fluvial alteration. Use of these features to draw palaeoclimatic inferences concerning permafrost and temperature is no longer tenable.