Read "Cirque overdeepening and their relationship to morphometry, Geomorphology" on DeepDyve, the largest online rental service for. yet, however, PFAFFL () investigated some characteristics of the lakes and deflation pla approaching the morphology of a glacial cirque develop after ca. . The relationship between mean steepness of slopes and altitude was . shape of the cirques in the Bohemian Forest (mainly their overdeepening of their cirque. the hypothesis that overdeepening can be initiated by an increase in ice velocity. . Defining overdeepenings that contain lakes, within sink data. .. Evaluating the strength of the relationship between glacial confluence and the cirque morphometries are commonplace (being a consequence of the general effect of.
The basin will become deeper as it continues to be eroded by ice segregation and abrasion. A bergschrund forms when the movement of the glacier separates the moving ice from the stationary ice forming a crevasse.
The temperature within the bergschrund changes very little, however, studies have shown that ice segregation frost shattering may happen with only small changes in temperature. Water that flows into the bergschrund can be cooled to freezing temperatures by the surrounding ice allowing freeze-thaw mechanisms to occur. When three or more cirques erode toward one another, a pyramidal peak is created. The Matterhorn in the European Alps is an example of such a peak. Where cirques form one behind the other, a cirque stairway results as at the Zastler Loch in the Black Forest.
As glaciers can only originate above the snowline, studying the location of present-day cirques provides information on past glaciation patterns and on climate change.
The island consists of an active shield-volcano Piton de la Fournaise and an extinct, deeply eroded volcano Piton des Neiges.
Cirque - Wikipedia
Three cirques have eroded there in a sequence of agglomerated, fragmented rock and volcanic breccia associated with pillow-lavas overlain by more coherent, solid lavas. However, cirque elevation effects are diverse. Whereas for the Cantabrian Range an increase in elevation determines an increase in cirque size.
The elevation effect for cirques should be linked to controlling factors such as lithology and the geological structure of these massifs, as well as their spatial distribution in relation to moisture sources, Specially in the SBMR where the Westerly winds and associated climate systems and rainfall gradients play an important role in the cirques development, as we explain below.
In general, the spatial distribution of different cirques types in SBMR would be the result of the combined actions of the following: Actually, west of the study area, around the accumulation zone of the SPIF, the annual precipitation reaches up to 10, mm Cassasa et al. We assume this reflects the rainfall gradient at SBMR, which favors the development of small cirques eroded by alpine-type glaciers cirques Type 1prevails at eastern higher areas of SBMR mainly due to the low temperatures associated with the E-W thermal gradient, moreover Type 1 reflects an alpine glaciated landscape that is isolated from coverage by the Pleistocene Ice Sheet, a particular morphoclimatic domain mainly in this eastern Andes foothills which also provides a useful natural laboratory for the study of the past environmental changes.
Another important factor in the development of the SBMR morphoclimatic configuration corresponds to the difference in the cirques floors elevations cirques Type 1, is about m above the cirques Type 2. The elevation factor helps the development of cirques that are extensively or commonly occupied by valley glaciers with a long ablation tongues that may have been influenced by activity associated with outlet glaciers from the Pleistocene Ice Sheet when it existed.
As well, cirque floor elevation also influences the development of glacial activity east of the Andean foothills along with ice sheet outlet glaciers due to the temperature gradient at SBMR. That is whether they are currently occupied by remnant glacial activity, and their location and size is mainly controlled by the low temperatures prevailing towards the interior of the continent. For large cirques located just to the east of SPIF glacial activity also is influenced by the effect of high precipitation, near the Pacific coast.
Cirque distribution, elevation and dimensions Based on the spatial distribution of the glacial cirques morphological types it is possible to recognize two domains of glacial activity in the study area. The first includes cirques Type 1 which mainly show evidence of perennial snowy activity, and in some cases evidence of glacial activity.
Some of these cirques contain latero-terminal moraines, and are distributed in an elevation range from 1, to 1, m. On average, these elevations appear to be about m above the altitude limit of landforms marking the expansion of the SPIF into the Southern Patagonian Ice Sheet during glacial maximun.
The second includes cirques Type 2 that shows no evidence of current glacial or snow activity and is found at relatively low elevations ranging from 1, to 1, m, as we move from the SPIF region to the east. Glacial deposits can also be considered as evidence of these glaciation limits. On the one hand morphological Type 1 can be linked to lateral moraine deposits constrained to the cirques Figs.
Paleoglacial significance Topographic and climatic conditions, besides the west to east climate contrast across Patagonia Glasser et al. Western Patagonian Ice Sheet glaciers exhibited a highly dynamic behavior, in part due to high precipitation and a positive mass balance Hulton et al.
As soon as the large ice sheet outlet glaciers retreated to the west of the study area, due to an uninterrupted climatic change i. However, our results indicate that the evolution of cirques in the study area was not uniform. Most likely because of a climatic gradient, cirque glaciers Type 2 developed to the west, near the SPIF, were more dynamic, and therefore their cirques experienced more erosion and enlarged more, than those to the east.
Differences in area and shape parameters of morphological types recognized in this study would be linked to the geographical evolution and climate of the study area, as well as aspect, exposure to the Westerly winds, and elevation.
Morphological Type 1 cirques, mainly located at altitudinal classes D and E 1, m a.
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Isolated from the SPIF during the Holocene, and under cold and dry weather conditions towards the interior of continent, this favored the presence of snow and ice coverage controlled mainly by aspect and local topographic conditions Figs. Morphological Type 1 can also be associated with high composite values Fig. On the other hand, morphological Type 2 cirques, mainly located at altitudinal classes B and Cm a. Morphological Type 2 are related with low composite values Fig.
The outlet glaciers may have overrun and occupied these cirques, or they may have co-existed with the waxing and waning of glaciers in the cirques, which may have flowed into the valleys and merged with the lower larger ice masses. Considering the above, we concluded that the morphological Type distribution Fig. This could be related to the specific climatic gradient across the region. In particular, it is plausible that the larger cirques near the SPIF were more dynamic due to high ice flux facilitated by higher winter precipitation and summer temperatures sensu Barr and Spagnolo, than the smaller cirques to the east.
The latter hypothesis is consistent with the present-day precipitation gradient across the study area. Given the Westerly winds and associated climate systems, SBMR tectonic uplift allowed intensification of the orographic effect, and associated temperature and precipitation gradients, which favored the development of independent alpine glaciers to the east even at relatively low elevations 1, to 1, m. This defined a new morphoclimatic setting in southern Patagonia, the Sierra Baguales alpine glaciated region, which can be considered as a satellite of the SPIF Mercer, Glacier variations associated with this domain have hardly been studied, and represent an opportunity to assess and interpret those factors that enabled the development of individual, small and independent glaciations, which provide a sensitive proxy of past environmental changes in the eastern foothills of the Southern Andes.
Based on 14 morphometric parameters and morphological classification of the SBMR glacial cirques, as well as the development of a composite map, in which the morphometric parameters were combined and standardized, we infer two glaciation domains related to the climatic and glacial history that characterize the study area.
The lower domain, located mainly in an intermediate zone between the eastern margin of the SPIF and lower sections of the SBMR to 1, m, at altitudinal classes B to Ccontains cirques that do not show current evidence of perennial snow activity or glacial processes. The surface and shape of these cirques suggest that they were highly dynamic, i.
The upper limit, particularly around the eastern side of the SPIF and in the most elevated sectors 1, to 1, m, altitudinal classes D to E contains cirques that mainly show perennial snow activity followed by glacial processes and in some cases, remnants of latero-terminal moraines marking larger former alpine glaciers.
The surface and shape of these cirques could be influenced by the action of alpine glaciers that persisted throughout the Holocene, due to prevailing low temperature and humidity conditions at the sites.
Along with the climatic gradient, other factors that favored the development of alpine-type cirque glaciations, including also the current glacial activity, that exists mainly around the upper level of the SBMR, include cirque floor elevation, mean slope, aspect and orientation aspect relative to the Westerly winds. Riquez allowed access to the farm Verdadera Argentina. Peltier lent invaluable assistance in field activities.
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South Africa Journal of Geology