Cirque Research Articles

Glacial cirques and the relationship between equilibrium line altitudes and mountain range height: COMMENT

Glacial cirques and the relationship between equilibrium line altitudes and mountain range height: COMMENT

Mid‐ and large‐scale geodiversity calculation in fuentes carrionas (nw spain) and serra do cadeado (paraná, brazil): methodology and application for land management

A state‐of‐the‐art geodiversity concept, its use and scientific development are presented. Methodologies for geodiversity calculation are assessed, as well as their aim and problems. Geodiversity calculation methodology based on biodiversity richness index is explained and applied to two different areas: uentes arrionas, a high mountain mid‐latitude environment in northern pain, and erra do adeado, a tropical mid‐mountain environment in southern rasil. A geodiversity map of uentes arrionas proves that glacial cirques over 2000 m a.s.l. keep a high geodiversity related to a periglacial and glacial environment, whereas a geodiversity map of erra do adeado shows that high geodiversity areas are situated at its main structural scarp. Geodiversity calculation needs to take scale and hierarchy issues into account, which makes comparison only possible if the same scale is used. Geodiversity calculation is a useful tool for land management as it defines areas subject to protection due to the richness of abiotic elements. It is also useful in terms of environmental impact assessment and geotourism evaluation at remote areas.

Rule Set Transferability for Object-Based Feature Extraction: An Example for Cirque mapping

AbstractCirques are complex landforms resulting from glacial erosion and can be used to estimate Equilibrium Line Altitudes and infer climate history. Automated extraction of cirquesmay help research on glacial geomorphology and climate change. Our objective was to test the transferability of an object-based rule set for the extraction of glacial cirques, using lidar data and color-infrared orthophotos. In Vorarlberg (W-Austria), we selected one training area with well-developed cirque components to parameterize segmentation and classification criteria. The rule set was applied to three test areas that are positioned in three altitudinal zones. Results indicate that the rule set was successful (81 percent) in the training area and a higher situated area (71 percent). Accuracy decreased in the two lower situated test areas (66 percent and 51 percent). We conclude that rule sets are transferable to areas with a comparable geomorphological history. Yet, significant deviation from the training area requires a different extraction strategy.

Lateglacial/Holocene environmental changes in the Mediterranean Alps inferred from lacustrine sediments

This study investigates sediment cores from the Mediterranean alpine lakes located in upvalley cirques upper than 1700 metres a.s.l. using sedimentological, palynological and geomorphological studies, in order to document environmental changes following the last phase of glacier retreat. These results are considered in the framework of the deglaciation characterized from 16 sediment cores from high-altitude lakes and mires including 104 14C ages and geomorphological studies of the Mediterranean Alps. Considering each sediment core proxy as an independent observation, i.e., comparisons between 14C ages and palynostratigraphy, between 14C ages and lithostratigraphy, between palynostratigraphy and lithostratigraphy, these data are aimed at contributing to a better understanding of the timing of postglacial environmental changes. The 14C ages combined with pollen biostratigraphy indicate that the deglaciation of cirque catchments is dated between 14,500 and 13,000 cal. BP, i.e., during the Lateglacial Interstadial (Greenland Interstadial-1e). The sixteen lacustrine and mire sediment records are systematically characterized by three units from bottom to top: organic-poor blue clay, beige to light-brown silty clay and organic rich dark brown gyttja lithotype. During the Younger Dryas, lakes located below 2300 m a.s.l. were ice-free and their pollen record indicates steppe conditions. The sedimentary facies also informs on the timing of glacial-dominated processes. The onset of organic-rich gyttja is dated at 11,000 cal. BP suggesting the last influence of cirque glaciers in these lakes at the beginning of the Holocene. The timing of the onset of this organic rich unit differs in sites (±2000 years) probably due to an altitudinal and exposure gradient of the glacial cirques. The presence of gyttja from 11,000 cal. BP to Present indicates biogenic infilling lake for all the Holocene. Even though the literature have indicated rock glacier advances occurred during the Holocene (Subboreal and LIA) in the south of the Alps, no significant sedimentological patterns related to glacier fluctuations are recorded in Lake Vens. The glacier fluctuations in the Mediterranean Alps are concomitant with those dated in the non-Mediterranean Alps, thus suggesting a main common climate forcing. However, the increase in terrigenous sediment inputs since 1800 cal. BP is mainly due to human activities.

Glacial cirques and the relationship between equilibrium line altitudes and mountain range height

Research Article| January 01, 2015 Glacial cirques and the relationship between equilibrium line altitudes and mountain range height Sara Gran Mitchell; Sara Gran Mitchell 1Department of Biology, College of the Holy Cross, P.O. Box B, 1 College Street, Worcester, Massachusetts 01610, USA Search for other works by this author on: GSW Google Scholar Elizabeth E. Humphries Elizabeth E. Humphries 2Department of Geological Sciences, University of North Carolina–Chapel Hill, 104 South Road, Campus Box #3315, Chapel Hill, North Carolina 27599, USA Search for other works by this author on: GSW Google Scholar Author and Article Information Sara Gran Mitchell 1Department of Biology, College of the Holy Cross, P.O. Box B, 1 College Street, Worcester, Massachusetts 01610, USA Elizabeth E. Humphries 2Department of Geological Sciences, University of North Carolina–Chapel Hill, 104 South Road, Campus Box #3315, Chapel Hill, North Carolina 27599, USA Publisher: Geological Society of America Received: 13 Aug 2014 Revision Received: 16 Oct 2014 Accepted: 19 Oct 2014 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2014 Geological Society of America Geology (2015) 43 (1): 35–38. https://doi.org/10.1130/G36180.1 Article history Received: 13 Aug 2014 Revision Received: 16 Oct 2014 Accepted: 19 Oct 2014 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation Sara Gran Mitchell, Elizabeth E. Humphries; Glacial cirques and the relationship between equilibrium line altitudes and mountain range height. Geology 2015;; 43 (1): 35–38. doi: https://doi.org/10.1130/G36180.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract A global GIS- and literature-based analysis of the altitude and relief of more than 14,000 ice-free glacial cirques in 56 study areas ranging from 69°N to 77°S shows that average cirque floor altitudes vary with latitude in a zone centered on the Quaternary average equilibrium line altitude (QA-ELA). In addition, relief above cirque floors averages 346 ± 107 m, and is rarely >600 m. In regions where ice-free cirques are abundant, cirque relief is independent of modern precipitation rates, tectonic regime, and relative peak height, limiting peaks to within a fixed distance above the QA-ELA and thus causing them to also parallel the ELA. We propose a physical process model where, under suitable geologic and tectonic conditions, climate exerts a first-order control on mountain range height. In this model, glacial erosion excavates a zone of cirques with floors centered on the QA-ELA, while climate-driven weathering processes on adjacent slopes limit the peaks to within a few hundred meters above this zone. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

Regional distribution and relevance in paleonvironmental studies of lakes in the Tatra Mts. (Western Carpathians)

Scientific limnological research in the Tatra Mountains were initiated by Stanislaw Staszic in the early XIX century. After the World War II, the evolution of Tatra lakes was investigated by Kondracki, Klimaszewski, Baumgart-Kotarba and. Extensive paleolimnological investigations in the Tatra Mountains were started by the group of scientists led by K. Starmach in the beginning of the second half of the 20 th century. There has been not much research concerned to the regional distribution of lakes and their properties in the Tatra Mountains (Pociask-Karteczka 2013). Very early division of lakes presented A. Gadomski (1922), which distinguished four types of lakes: a) tarns (cirque lake or corrie loch), b) bedrock-dammed lakes, c) moraine lakes. This division was concerned in subsequent publications (Choinski 2007). M. Luknis (1973, 1985) recognized additional types: kettles and landslide-dammed lakes and M. Klimaszewski (1988) – inter-sheepback lakes. J. Pacl and K. Wit-Joźwik in Klima Tatier (Pacl, Wit-Joźwik 1974) were focused on the temperature of water in lakes in Polish and Slovak parts and M. Borowiak (2000a,b) provided a comprehensive analysis of types, dimensions, temperature and chemical composition of water in lakes in the Tatra Mountains. According to present day state of knowledge, one may distinguish following genetic types of lakes: I) glacial, II) not-glacial. There are four types of the glacial origin lakes in the Tatra Mountains (Fig. 1): a) tarns (cirque lakes or corrie loch), b) bedrock-moraine dammed lakes, c) inter-sheepback lakes, d) moraine lakes, e) kettles. Most of lakes in the Tatra Mountains are tarns and bedrock-moraine dammed lakes, and they are located at the elevation over 1400 m a.s.l. in the Western Tatra Mountains, and over 1600 m a.s.l. in the High Tatra Mountains. Some of them are paternoster lakes – a series of stair-stepped lakes formed in individual rock basins aligned down the course of a glaciated valley. Lakes in the Five Polish Lakes Valley is an example of such type. The inter-sheepback lakes occur at higher elevations (e.g. Wyznie Mnichowe Stawki, Zamrznute oka). There is a little number of moraine lakes in the Tatra Mountains (e.g. Smreczynski, Toporowy Nizni) and kettles (e.g. Strbske Pleso, Kotlinowy Stawek). Some lakes are located among rock debris or rock debris and moraine material (Dwoisty Staw Gąsienicowy, Anitino ocko) – they are of polygenetic origin.

Electrical resistivity tomography (ERT) surveys on glacial deposits in Romanian Carpathians

The study presents preliminary results regarding the use of electrical resistivity surveys in the assessment of the internal structure of the glacial deposits from the Romanian Carpathians. ERT is a geophysical method used to quantify changes in electrical resistivity of the ground towards passing electric current across an array of electrodes and simultaneous measurement of the induced potential gradient. Using specific software the measurements are further processed and correlated with the topography in order to obtain bedrock resistivity features. Therefore, the method is useful to evaluate the characteristics of geological strata and is widely used for mapping shallow subsurface geological structures. In the mountain regions ERT studies have been applied in different glacial and periglacial geomorphological studies - for permafrost detection (in Romanian Carpathians - Urdea et. al., 2008; Vespremeanu-Stroe et al., 2012), slope deformation analysis, the assessment of slip surface depths, sediment thickness, groundwater levels etc. One of the most commonly 2-D array used is the Wenner electrode configuration, which is moderately sensitive to both horizontal and vertical ground structures. Due to their elevations and Pleistocene’s climatic conditions, the Romanian Carpathians have been partially affected by Quaternary glaciations. The glaciers descended to about 1050-1200 m a.s.l. (Urdea and Reurther, 2009) in the Transylvanian Alps and Rodna Mountains (Eastern Carpathians) carving a large number of U-shaped valleys and glacial cirques (Mindrescu, 2006) and forming accumulations of unconsolidated glacial debris (moraines). Our study areas are two sites located in the northern (Rodna Mts.) and southern (Iezer Papusa Mts.) part of the mountain range.

A critical appraisal of allometric growth among alpine cirques based on multivariate statistics and spatial analysis

When considering the morphometric attributes of a glacial cirque, imbalances between length, width, and amplitude have been deemed relevant tools for discriminating between two possible pathways of cirque growth: downwearing by glaciers or backwearing by freeze–thaw processes. Based on a sample of 1071 cirques in the French Pyrenees, we reframe the concern for climatic variables by also granting systematic consideration to cirque lithology. Insight into the factors that control cirque shape is gained from Principal Component Analysis, where maps of eigenvalues assigned to six classes of bedrock display spatial patterns of cirque form as a function of position along the regional climatic gradient. Among crystalline rocks (granite, gneiss, migmatite), cirque form is predominantly determined by climatic controls. This is highlighted in the contrast between the elevated core of the Pleistocene icefield, where cirque isometry prevails, and the more peripheral areas (external sierras of the Atlantic precipitation zone and high sierras of the drier Mediterranean zone) where the lighter imprint of glaciation on the landscape has failed to erase (through glacial deepening) the allometric signature of pre-Pleistocene topographic features such as shallow valley heads and etch-basins. As a result, wide and shallow cirques occur in these settings. Among schist outcrops, in contrast, cirque form appears randomly distributed, suggesting that bedrock characteristics (e.g., structure) rather than climate are the key controls on cirque growth patterns. Given the importance of geological structure and preglacial topographic inheritance, cirques are complex landforms for which assumptions of allometric growth may be spurious. It follows that form is not always a reliable guide to process.

Magnitude of fluvial transport and rate of denudation in a non‐glacierised catchment in a polar zone, central spitsbergen

Research into the magnitude of fluvial transport was carried out in the non‐glacierised polar ynamisk ekken catchment in the region of Petunia Bukta, in the central part of est pitsbergen. The study period included two ablation seasons (uly–ugust) in 2008 and 2009. The stream flows from the glacial cirque cutting the north‐western edge of the ordiekammen assif. The bedrock is composed of sedimentary rocks. The ynamisk ekken is periodic stream, mainly fed from snow cover from une to early eptember. The other components of the feeding in the ablation seasons are less effective precipitation and groundwater from the active layer of permafrost. Medium discharge was 27.4 dm3 s–1 ranging from 0.1 to 250.8 dm3 s–1. Average ionic composition of the water indicates the hydrogeochemical sulphate‐bicarbonate‐calcium type. A tendency of systematic increase in the proportion of sulphates and decreasing share of bicarbonate ions in the ionic composition of water during the ablation season was observed. This correlates with the gradual decrease in the discharge rate and the decrease of the meltwater in the stream feed. The proportion of geogenic components in the dissolved load material outflow from the catchment is 75%. It consists of mainly bicarbonates, sulphates and calcium, which are derived from the dissolving of limestone, gypsum and anhydrite. The average value of the chemical denudation was 0.35 t km–2 d–1 and the mechanical denudation 0.32 t km–2 d–1. The results are similar to those obtained in previous years, reflecting the relatively large stability of the polar environment.

An Approach to Geotopes of Jajrud Catchment Basin from Meygun to Darbandsar

Development of urbanization imposed many mental and physical stresses on citizens. Air Pollution, noise pollution, Overcrowding, cars and the lack of green space caused Urbanites to need to have more leisure time. These causes resulted in interests of authorities to tourism. Tourism plays an important role in both Increasing revenues and employment and cultural and social aspects. Geotopes and geological phenomenon including caves, canyons, valleys, fossil sites, beaches etc., as a geological heritage, can be examined as potential geosites in developing geotourism and establishing geoparks. The studied area has various Climatic and geomorphological heritage including glacial cirques, terrace, wandering rocks, canyons and cliffs, caves and springs reflecting the ancient climates. Hence, it can be introduced as a platform for more geographical research as a geosite. key words: Geotope, Geosite, Geotourism, Geopark.

Use of the mercury record in Red Tarn sediments to reveal air pollution history and the implications of catchment erosion

Red Tarn is a cirque lake with a small ratio of terrestrial area to lake area, surrounded by glacial edges with little soil in the catchment. A sediment core taken from the deepest area of the lake was (210)Pb dated and validated by (137)Cs and (241)Am stratigraphic records. The core was analysed for mercury (Hg) and other elements. The results show Hg pollution before the mid-19th century, and thereafter, a rapid increase in Hg pollution into modern time, followed by a decline in pollution since 1968-1970. This agrees well with the decline in UK Hg emissions since the Clear Air Act of 1968. The results suggest that the core has recorded Hg air pollution history, and it can be used to benchmark Hg changes in the sediments from other lakes in the region up to the late 1980s. However, increased (210)Pb fluxes after the late 1980s indicate enhanced catchment erosion, which has brought more legacy Hg in the catchment into the lake. As a consequence, since 2000, the Hg in the sediment record no longer reflects the atmospheric Hg deposition. The core shows how dominant Hg sources for the lake changed from atmospheric deposition to the catchment inputs, and demonstrates that contaminated catchment inputs have not only increased Hg fluxes to the lake sediments but have also increased Hg concentrations in the sediments.

Combined use of GIS and experimental functions for the morphometric study of glacial cirques, Zardkuh Mountain, Iran

Morphometric analysis using DEM (with 10 m spatial resolution) is performed on the main cirque-like features in the Zardkuh Mountain (central Zagros Mountain Range, IRAN) to study the evolution patterns of these features. For this purpose, the cirque like-features were delimitated manually and their headwall and floor boundaries were modified based on the slope map (10 m spatial resolution) classified based on the definition of cirque. The power law functions were fitted to 58 longitudinal cross-sections of the cirque-like features and their parameters were analyzed. The analysis showed that high values of b coefficient have good correlation with the cirque-like features which their morphometric characteristics are generally coincide with the definitions of cirques and location of the small glaciers. All the cirque-like features were classified based on results of the power function model and comparison of longitudinal profiles of the cirque like-features with the Vilborg and Evans classification system. At least 9 cirques with the classical characteristics were distinguished in the altitudes above 3650 m a.s.l. of Zardkuh Mountain (mean values of b coefficient (b¯) is equal to 2.1). In addition, 19 cirques were classified as “Well-defined” (10 cirques with b¯ ≥ 2.0) and “Definite cirques” (9 cirques with b¯ ≥ 1.7). The other cirque-like features (30 cirques with b¯ ≥ 1.4) were considered as “Poor” and “Marginal” cirques. In addition, the morphometric parameters of 28 cirques (with most glacial characteristics) and their allometric behaviors were analyzed. The allometric coefficients of length and width are above 1.0 and for depth is significantly below 1.0 (or vertical development of the cirques increases slower than that of length and width) in accordance with similar research.

Sediment connectivity in the high-alpine valley of Val Müschauns, Swiss National Park — linking geomorphic field mapping with geomorphometric modelling

The efficiency of sediment routing through mountain sediment cascades is controlled by the connectivity of hillslopes to the main river system. A lack of connectivity may cause long-term sediment storage and exclude large fractions of a basin from the sediment routing for several thousand years. Here, we studied sediment dynamics in a small, formerly glaciated valley in the Swiss Alps. To characterise the sediment connectivity to the stream, we calculated a morphometric index using a GIS algorithm. The modelling results were tested against a field based geomorphic mapping of sediment storages, which were evaluated with respect to their state of (de)coupling. In accordance to the field diagnostics, the modelling results indicate very well that the present-day sediment flux is conditioned by the glacial valley morphometry inherited through Pleistocene glaciation. Especially in the upper hanging valleys, the connectivity index is reduced noticeably due to the glacial cirque morphology. Based on the field mapping, 30% of the hillslope sediment cascades are interrupted and 20% of the storage boundaries are currently affected by a lack of material transfer. As a consequence, ~29% of the basin surface is currently disconnected from the main river. Nevertheless, the GIS algorithm overestimates the connectivity within the basin, because it fails to calculate decoupling between neighbouring pixels in digital terrain models (DTMs). Around 35% of the basin surface, which has been mapped in the field as being decoupled, is related to relative high connectivity. Our study highlights the potential of morphometric GIS modelling for studying sediment connectivity, but additionally emphasises the indispensability of geomorphic field mapping for a holistic understanding of mountain cascading systems.

Environmental evolution in Sierra Nevada (South Spain) since the Last Glaciation, based on multi-proxy records

Our knowledge of the Quaternary landscape evolution in the high mountain areas of the Iberian Peninsula has substantially improved over the last decades. The Sierra Nevada is one of the most studied mountain ranges in southern Europe regarding its environmental evolution. The purpose of the present paper is to integrate and summarize all the studies focused on the reconstruction of the palaeoenvironmental history in this massif since the Last Glaciation. Research has focused both on different sedimentary records and historical sources. A wide range of geomorphological, sedimentological and geochronological techniques have been used to characterize the glacial, periglacial, wetland and lacustrine records for palaeoenvironmental purposes. For the last nine centuries tens of descriptions, maps and sketches describe the landscape of the summit area of the Sierra Nevada, providing evidences of the historical environmental events. Based on a multi-proxy approach, five periods have been identified: Last Glaciation, deglaciation, Holocene, Little Ice Age and recent evolution. Recent studies have detected the maximum expansion of glaciers in the Sierra Nevada around 30–32 ka BP, predating the global temperature minimum. No data about the environmental evolution is available between 20–30 ka BP. Around 19–20 ka BP glaciers advanced significantly. The process of deglaciation was rapid and around 14–15 ka BP the massif was almost free of ice. The Late Glacial promoted the formation of small glaciers in the highest northern cirques and widespread active periglacial processes (i.e. rock glaciers). During the Holocene there has been an alternation of colder/warmer periods and changing moisture conditions. Periglacial processes have been generally widespread in the summit area, with an increasing or decreasing activity depending on climate conditions. Ephemeral reappearance of small glacial cirques occurred in the highest northern cirques during the coldest and wettest phases. This is the case of the Little Ice Age, as revealed by historical documents and sedimentary records. Since the last decades of the XIX century the temperature has increased ∼0.93°C leading to a decrease of the intensity of periglacial processes in the high lands of the Sierra Nevada.

Cirque form and development in Romania: Allometry and the buzzsaw hypothesis

A complete inventory of the 631 glacial cirques in Romania (and adjacent Ukraine) shows that they are scale-specific and develop allometrically, extending in length more rapidly than they deepen: shape changes with size. Horizontal dimensions are around 700m, vertical around 300m. On each quantitative measure they form a single, unimodal population with limited variation in size (on a logarithmic scale). Cirque axial gradients (15–33°) are appropriate to occupation by rotationally-flowing glaciers. Lake basins are more common (26%) on granitic rocks, compared with 10.6% of all cirques. Geology also affects vertical dimensions and gradients. The relation between subjective (five grades) and objective measures of cirque development is shown by an r2 of 62% when Grade is predicted from maximum gradient, minimum gradient, and plan closure. Cirques larger in horizontal dimensions have better grades.Cirque floors cover around 28% of cirque map area. Larger cirques, and nested inner and outer cirques, are common in ranges that rose well above the snowline, and are associated with more extensive, more symmetrical glaciation and more cols. In size and shape Romanian cirques are similar to those in England and Wales. They are similar in some respects to those in part of the British Columbia Coast Mountains, except for smaller vertical dimensions. They may have developed only in the last few glaciations: mountain ranges can be ranked by degree of glacial modification and symmetry of glaciations. The ‘buzzsaw hypothesis’ is applicable only in the cores of the higher ranges: elsewhere, summit surfaces that are essentially preglacial survive.

Detecting complex relations among vegetation, soil and geomorphology. An in-depth method applied to a case study in the Apennines (Italy)

Physical environment is the ruling factor of vegetation patterns in mountain areas, where vegetation mosaics are determined by a complex interplay among topography, geomorphology and soil. A deep analysis of such interplay is pivotal in order to build vegetation anamnesis and make sound projections. Instead, even recent cartographic models are still linked to standard statistical methods which are not on top of an efficient uncovering of knotty associations among these kinds of data. To this aim, in this study we propose a novel approach for: (a) assessing the associations among vegetation, soil, topography and geomorphology; (b) measuring the frequency and strength of these associations; (c) define in a rigorous way land units based on vegetation–soil–geomorphology associations; (d) advance hypotheses on the causes and prospects of the existing spatial pattern. In order to test the strength of the proposed methodology we applied it to a case study in the above-tree-line glacial cirque of Mount Prado (Northern Apennines, N Italy). In this area, the vegetation mosaic is still strongly conditioned by physical features but in a lower measure with respect to the higher alpine sites. We have been able to detect and weight 168 kinds of associations among vegetation, soil and geomorphological types, 1092 kinds of associations among vegetation and topographic variables and 12 land units with inner dominance of a particular association. The analysis of associations between vegetation types, soils, topography and landforms produced considerable insights into the ecology of the occurring plant communities. This proposed analytic methodology can be extended to other regions (e.g. mountain and alpine areas) and can also be considered a tool for interpreting present landscape heterogeneity also in a historical perspective.

Variations in landform definition: a quantitative assessment of differences between five maps of glacial cirques in the Ţarcu Mountains (Southern Carpathians, Romania)

Geomorphological mapping is an important tool in geomorphology and related disciplines, yet it depends on the expertise and experience of the practitioner. The reliability of the technique and its products has not been subject to sufficient quantitative evaluation. In this study, we evaluated the magnitudes of differences in mapping glacial cirques between five maps in a mountainous area in the Southern Carpathians in Romania and attempted to identify the causes of the differences observed and possible solutions for obtaining more objective geomorphological mapping. We found notable differences between maps (in paired sample comparisons in all cases for the total values in each dataset) in the number of cirques, the total area and in headwall crest lengths. Statistically significant differences were found between datasets based on different semantic models of glacial cirques. Differences in mapping arise mainly from differences in conceptualising glacial cirques. When mapping relied on an explicit semantic model (a geomorphometric approach), differences were significantly smaller. Therefore, explicit semantic models of landforms based on land surface variables can result in more similar maps and further facilitate the transition from manual delineation to automated recognition of landforms from Digital Elevation Models (DEMs).

Distribution and inferred age of exfoliation joints in the Aar Granite of the central Swiss Alps and relationship to Quaternary landscape evolution

Exfoliation joints are well-known natural fractures limited to near the ground surface. Relatively few details, however, are known about their distribution and age in the Swiss Alps. Exfoliation joints follow the landscape surface at the time of their formation; the age of the associated landscape feature then provides a maximum age of exfoliation joints. While landscape forms can change through time, exfoliation joints preserve elements of former landscape morphologies by their undisturbed orientations. The Grimsel region of the Central Alps is well-suited for analyzing the impact of erosional episodes, and accompanying stress changes, on exfoliation joint formation in granitic rocks. Mapping above and below ground revealed that exfoliation joints are widespread and occur between valley bottoms and mountain crests within glacial (inner and hanging U-shaped trough valleys, glacial cirques, and steep mountain crests) and predominantly fluvial landforms (gently inclined linear slopes above the inner trough valleys, narrow inner-valley gorges, and steep V-shaped side gullies). Based primarily on their geometric properties at the ground surface, three exfoliation joint types were distinguished in our study area: (1) closely spaced (<1m) joints oriented distinctly parallel to the present-day ground surface, (2) intermediately spaced (0.6–2m) joints that are nearly parallel (<10° difference) to today's mean ground surface at a 10-m scale, and (3) widely spaced (≫2m) joints not parallel to the ground surface. Relating the mapped distribution of exfoliation joint types to identified erosional episodes and landscape features of known and inferred ages, respectively, enables us to distinguish four exfoliation joint generations in the Grimsel area, which most likely formed during the lower Pleistocene (~1.5–1Ma), middle Pleistocene (~0.7–0.4Ma), upper Pleistocene (0.1–0.02Ma), and Late Glacial/Holocene (<0.02Ma). We demonstrate that the most prominent and deepest exfoliation joint generation is associated with erosion of the inner glacial troughs of the upper Aar valley, which likely occurred during the mid-Pleistocene Revolution. Our study shows how exfoliation joint episodes can be dated, and, conversely, that better knowledge of the distribution of exfoliation joint sets can reveal unique information about the morphological evolution of an Alpine valley.

The influence of aspect and altitude on the size, shape and spatial distribution of glacial cirques in the High Tatras (Slovakia, Poland)

The shape of glacial cirques is generally considered to result from the combined actions of climate, topography, and geology. The goal of this article was to determine the dependence of cirque morphology on mesoclimatic conditions defined by altitude and aspect in the highest part of the Carpathians — the High Tatras. The morphology of each of 116 analyzed cirques was described using a set of 12 morphometric characteristics. The relationships between the obtained data were evaluated using simple and multivariate statistical methods. The results indicate that cirques in the High Tatras are scale-specific landforms with allometric development. Their occurrence increases with altitude, but their size decreases. The shape of the cirques is determined by altitude only to a small extent, with the exception of an increase in the degree of incision with altitude. The spatial distribution of cirques is negatively influenced by incoming solar radiation and positively influenced by moisture sources, which came mainly from the NW to N during the cold phases of the Pleistocene. For this reason, north-facing cirques have proportionally stronger representation and are more incised with steep slopes. Thus, cirques have proportionally stronger representation on the northern slopes and represent more developed glacial erosion landforms than those on the southern slopes. Although some relationships were detected between cirque morphology and mesoclimatic factors (such as altitude and aspect), a general discriminant analysis showed that these environmental factors did not explain variations in cirque morphology with sufficient cogency.

Palaeoglacial and palaeoclimatic conditions in the NW Pacific, as revealed by a morphometric analysis of cirques upon the Kamchatka Peninsula

The distribution of glacial cirques upon the Kamchatka peninsula, Far Eastern Russia, is systematically mapped from satellite images and digital elevation model data. A total of 3758 cirques are identified, 238 of which are occupied by active glaciers. The morphometry of the remaining 3520 cirques is analysed. These cirques are found to show a very strong N bias in their azimuth (orientation), likely resulting from aspect-related variations in insolation. The strength of this N bias is considered to indicate that former glaciation upon the peninsula was often ‘marginal’, and mainly of cirque-type, with peaks extending little above regional equilibrium-line altitudes. This is supported by the fact that S and SE-facing cirques are the highest in the dataset, suggesting that glacier-cover was rarely sufficient to allow S and SE-facing glaciers to develop at low altitudes. The strength of these azimuth-related variations in cirque altitude is thought to reflect comparatively cloud-free conditions during former periods of glaciation. It is suggested that these characteristics, of marginal glaciation and comparatively cloud-free conditions, reflect the region's former aridity, which was likely intensified at the global Last Glacial Maximum, and during earlier periods of ice advance, as a result of the development of negative pressure anomalies over the North Pacific (driven by the growth of the Laurentide Ice Sheet), combined with other factors, including an increase in the extent and duration of sea ice, a reduction in global sea levels, cooler sea surface temperatures, and the localised growth of mountain glaciers. There is published evidence to suggest extensive glaciation of the Kamchatka Peninsula at times during the Late Quaternary, yet the data presented here appear to suggest that such phases were comparatively short-lived, and that smaller cirque-type glaciers were generally more characteristic of the period.