No description available.

Essa dissertação realizou o levantamento das variações nas frentes das geleiras no extremo norte da Península Trinity, na Antártica, através da utilização de técnicas de Sensoriamento Remoto. Foram mapeados os avanços e as retrações ocorridas nas frentes das geleiras da área, bem como as áreas livres de gelo da região, no período de 27 anos entre 1988-2015. Os resultados foram complementados com dados de temperatura média do ar para a região. A base de dados utilizou de 8 imagens do satélite Landsat (sensores TM, ETM+ e OLI/TIRS), além de dados da base de dados digitais da Antártica (ADD), o Mosaico de Imagens Landsat da Antártica (LIMA), e o modelo digital de elevação para a Península Antártica (APGDEM). Os dados de temperatura utilizados são provenientes da base antártica Esperanza (ARG), adquiridos através do READER. As linhas de frente das geleiras foram obtidas através de métodos automáticos e manuais de geoprocessamento. Foram realizadas classificações não-supervisionadas e supervisionadas na aquisição dessas, transformando-as em vetores e unindo-as a delimitação das bacias de drenagem glacial disponibilizada pelo ADD, formando, assim, o conjunto de geleiras com a sua posição de frente para cada ano das imagens (1988, 2000, 2006, 2011 e 2015). As áreas livres de neve e gelo foram obtidas através de classificação supervisionada. As classificações foram validadas através do índice Kappa, obtendo resultados satisfatórios. O total da área de estudo é de aproximadamente 1.450 km² e conta com 32 bacias de drenagem glacial, destas, 3 possuem nome, as geleiras de maré Arena, Depot e Mondor. Com análises desde do o período de 1988, observou-se uma perda de massa de gelo da área de aproximadamente 50 km², enquanto que o ganho total foi de aproximadamente 10 km², resultando em uma diminuição de ±40 km² (ou seja, em torno de ±2,7 % da área total). No período entre 1988 e 2000 (maior intervalo das investigações) a área perdeu ±25,1 km² de gelo em suas frentes. Entre 2000 e 2006 o recuo foi de ±12,2 km² e entre 2006 e 2011 de 5,0 km². Já o período de 2011-2015 foi o único a apresentar avanços maiores que retrações, com um aumento de área de ±2,5 km² (±0,16%). As geleiras Depot e Mondor apresentaram comportamento de retração, sendo que a geleira Depot não apresentou nenhum avanço dentro dos períodos, já a geleira Arena apresentou avanços e retrações em todos os intervalos, permanecendo praticamente inalterada. A área livre de gelo e neve aumentou em aproximadamente ±18 km², ou seja, um acréscimo de ±114% em relação a área livre de neve e gelo de 1988. Os maiores aumentos se deram entre os anos 1988 e 2000, no ano de 1988 a área representava ±15,91 km², passando para ±37,54 km² em 2000 e ±37,90 km em 2006, no ano de 2011 observou-se uma diminuição, com área de ±28,32 km², sendo que em 2015 a área voltou aos valores anteriores, ±34,09 km². A avaliação da temperatura do ar observada em Esperanza entre 1964-2014 mostra um aumento de 1,45°C. / This dissertation conducted a survey of variations of ice fronts in glaciers positions on the northern tip of the Trinity Peninsula by using remote sensing techniques. Advances and retreats of glaciers were mapped, as well as ice-free areas in the 27-year period between 1988-2015, and the results were complemented with air temperature data for the region. The database used eight satellite images from Landsat (TM, ETM + and OLI/TIRS sensors). In addition, it was used the Antarctica Digital Database (ADD) data, the Landsat Image Mosaic of Antarctica (LIMA), and the digital elevation model Antarctic Peninsula 100 m Digital Elevation Model (APGDEM). The temperature data used come from the Antarctic station Esperanza (ARG), acquired through READER. The glaciers ice fronts positions were obtained through automatic and manual methods. Unsupervised and supervised classifications were performed in the acquisition of these, turning them into vectors and uniting them with the delimitation of glacial drainage basins provided by ADD, thus forming the set of glaciers with its front position for each year of images (1988, 2000, 2006, 2011 and 2015). The ice-free areas were obtained by supervised classification. The classifications were validated through the Kappa index, obtaining satisfactory results. The total study area is approximately 1,450 square kilometers and has 32 glacial drainage basins, these, three are named glacier (Arena, Depot and Mondor), all three tidewater glaciers. In the period of analysis, since 1988, there has been a loss of mass of ice area of approximately 50 square kilometers, whereas the total gain was only ±10 square kilometers, resulting in an overall decrease of approximately ±40 square kilometers (i.e. ±2,7% of the total area). Between 1988-2000 (the wider range of investigations), the area lost ±25.1 square kilometers of ice on its fronts, from 2000 to 2006 there was a decrease of ±12.2 km², and between 2006 to 2011 others ±5.0 km²; the 2011-2015 interval was the only one to show advances greater that retreats with a ±2.5 sq km increase in the area (±0.16%). The Depot and Mondor glaciers showed retreat behavior, and Depot did not show any advance within the periods, the Arena glacier showed advances and retreats in all intervals, remaining virtually unchanged. The ice-free area increased by approximately 18 square kilometers, that is, a ±114% increase over the 1988 snow/ice free area. The largest increases were given in the years 1988-2000, in 1988 the area represented ±15.91 km², reaching ±37.54 km² in 2000 and ±37.90 km in 2006, in 2011 there was a decrease, with an area of ±28.32 square kilometers, and in 2015 the area returned to its previous values, ±34.09 km². The air temperature evaluation in Esperanza observed in 1964-2014 years show an increase of 1.45 ° C.

Essa dissertação realizou o levantamento das variações nas frentes das geleiras no extremo norte da Península Trinity, na Antártica, através da utilização de técnicas de Sensoriamento Remoto. Foram mapeados os avanços e as retrações ocorridas nas frentes das geleiras da área, bem como as áreas livres de gelo da região, no período de 27 anos entre 1988-2015. Os resultados foram complementados com dados de temperatura média do ar para a região. A base de dados utilizou de 8 imagens do satélite Landsat (sensores TM, ETM+ e OLI/TIRS), além de dados da base de dados digitais da Antártica (ADD), o Mosaico de Imagens Landsat da Antártica (LIMA), e o modelo digital de elevação para a Península Antártica (APGDEM). Os dados de temperatura utilizados são provenientes da base antártica Esperanza (ARG), adquiridos através do READER. As linhas de frente das geleiras foram obtidas através de métodos automáticos e manuais de geoprocessamento. Foram realizadas classificações não-supervisionadas e supervisionadas na aquisição dessas, transformando-as em vetores e unindo-as a delimitação das bacias de drenagem glacial disponibilizada pelo ADD, formando, assim, o conjunto de geleiras com a sua posição de frente para cada ano das imagens (1988, 2000, 2006, 2011 e 2015). As áreas livres de neve e gelo foram obtidas através de classificação supervisionada. As classificações foram validadas através do índice Kappa, obtendo resultados satisfatórios. O total da área de estudo é de aproximadamente 1.450 km² e conta com 32 bacias de drenagem glacial, destas, 3 possuem nome, as geleiras de maré Arena, Depot e Mondor. Com análises desde do o período de 1988, observou-se uma perda de massa de gelo da área de aproximadamente 50 km², enquanto que o ganho total foi de aproximadamente 10 km², resultando em uma diminuição de ±40 km² (ou seja, em torno de ±2,7 % da área total). No período entre 1988 e 2000 (maior intervalo das investigações) a área perdeu ±25,1 km² de gelo em suas frentes. Entre 2000 e 2006 o recuo foi de ±12,2 km² e entre 2006 e 2011 de 5,0 km². Já o período de 2011-2015 foi o único a apresentar avanços maiores que retrações, com um aumento de área de ±2,5 km² (±0,16%). As geleiras Depot e Mondor apresentaram comportamento de retração, sendo que a geleira Depot não apresentou nenhum avanço dentro dos períodos, já a geleira Arena apresentou avanços e retrações em todos os intervalos, permanecendo praticamente inalterada. A área livre de gelo e neve aumentou em aproximadamente ±18 km², ou seja, um acréscimo de ±114% em relação a área livre de neve e gelo de 1988. Os maiores aumentos se deram entre os anos 1988 e 2000, no ano de 1988 a área representava ±15,91 km², passando para ±37,54 km² em 2000 e ±37,90 km em 2006, no ano de 2011 observou-se uma diminuição, com área de ±28,32 km², sendo que em 2015 a área voltou aos valores anteriores, ±34,09 km². A avaliação da temperatura do ar observada em Esperanza entre 1964-2014 mostra um aumento de 1,45°C. / This dissertation conducted a survey of variations of ice fronts in glaciers positions on the northern tip of the Trinity Peninsula by using remote sensing techniques. Advances and retreats of glaciers were mapped, as well as ice-free areas in the 27-year period between 1988-2015, and the results were complemented with air temperature data for the region. The database used eight satellite images from Landsat (TM, ETM + and OLI/TIRS sensors). In addition, it was used the Antarctica Digital Database (ADD) data, the Landsat Image Mosaic of Antarctica (LIMA), and the digital elevation model Antarctic Peninsula 100 m Digital Elevation Model (APGDEM). The temperature data used come from the Antarctic station Esperanza (ARG), acquired through READER. The glaciers ice fronts positions were obtained through automatic and manual methods. Unsupervised and supervised classifications were performed in the acquisition of these, turning them into vectors and uniting them with the delimitation of glacial drainage basins provided by ADD, thus forming the set of glaciers with its front position for each year of images (1988, 2000, 2006, 2011 and 2015). The ice-free areas were obtained by supervised classification. The classifications were validated through the Kappa index, obtaining satisfactory results. The total study area is approximately 1,450 square kilometers and has 32 glacial drainage basins, these, three are named glacier (Arena, Depot and Mondor), all three tidewater glaciers. In the period of analysis, since 1988, there has been a loss of mass of ice area of approximately 50 square kilometers, whereas the total gain was only ±10 square kilometers, resulting in an overall decrease of approximately ±40 square kilometers (i.e. ±2,7% of the total area). Between 1988-2000 (the wider range of investigations), the area lost ±25.1 square kilometers of ice on its fronts, from 2000 to 2006 there was a decrease of ±12.2 km², and between 2006 to 2011 others ±5.0 km²; the 2011-2015 interval was the only one to show advances greater that retreats with a ±2.5 sq km increase in the area (±0.16%). The Depot and Mondor glaciers showed retreat behavior, and Depot did not show any advance within the periods, the Arena glacier showed advances and retreats in all intervals, remaining virtually unchanged. The ice-free area increased by approximately 18 square kilometers, that is, a ±114% increase over the 1988 snow/ice free area. The largest increases were given in the years 1988-2000, in 1988 the area represented ±15.91 km², reaching ±37.54 km² in 2000 and ±37.90 km in 2006, in 2011 there was a decrease, with an area of ±28.32 square kilometers, and in 2015 the area returned to its previous values, ±34.09 km². The air temperature evaluation in Esperanza observed in 1964-2014 years show an increase of 1.45 ° C.

Essa dissertação realizou o levantamento das variações nas frentes das geleiras no extremo norte da Península Trinity, na Antártica, através da utilização de técnicas de Sensoriamento Remoto. Foram mapeados os avanços e as retrações ocorridas nas frentes das geleiras da área, bem como as áreas livres de gelo da região, no período de 27 anos entre 1988-2015. Os resultados foram complementados com dados de temperatura média do ar para a região. A base de dados utilizou de 8 imagens do satélite Landsat (sensores TM, ETM+ e OLI/TIRS), além de dados da base de dados digitais da Antártica (ADD), o Mosaico de Imagens Landsat da Antártica (LIMA), e o modelo digital de elevação para a Península Antártica (APGDEM). Os dados de temperatura utilizados são provenientes da base antártica Esperanza (ARG), adquiridos através do READER. As linhas de frente das geleiras foram obtidas através de métodos automáticos e manuais de geoprocessamento. Foram realizadas classificações não-supervisionadas e supervisionadas na aquisição dessas, transformando-as em vetores e unindo-as a delimitação das bacias de drenagem glacial disponibilizada pelo ADD, formando, assim, o conjunto de geleiras com a sua posição de frente para cada ano das imagens (1988, 2000, 2006, 2011 e 2015). As áreas livres de neve e gelo foram obtidas através de classificação supervisionada. As classificações foram validadas através do índice Kappa, obtendo resultados satisfatórios. O total da área de estudo é de aproximadamente 1.450 km² e conta com 32 bacias de drenagem glacial, destas, 3 possuem nome, as geleiras de maré Arena, Depot e Mondor. Com análises desde do o período de 1988, observou-se uma perda de massa de gelo da área de aproximadamente 50 km², enquanto que o ganho total foi de aproximadamente 10 km², resultando em uma diminuição de ±40 km² (ou seja, em torno de ±2,7 % da área total). No período entre 1988 e 2000 (maior intervalo das investigações) a área perdeu ±25,1 km² de gelo em suas frentes. Entre 2000 e 2006 o recuo foi de ±12,2 km² e entre 2006 e 2011 de 5,0 km². Já o período de 2011-2015 foi o único a apresentar avanços maiores que retrações, com um aumento de área de ±2,5 km² (±0,16%). As geleiras Depot e Mondor apresentaram comportamento de retração, sendo que a geleira Depot não apresentou nenhum avanço dentro dos períodos, já a geleira Arena apresentou avanços e retrações em todos os intervalos, permanecendo praticamente inalterada. A área livre de gelo e neve aumentou em aproximadamente ±18 km², ou seja, um acréscimo de ±114% em relação a área livre de neve e gelo de 1988. Os maiores aumentos se deram entre os anos 1988 e 2000, no ano de 1988 a área representava ±15,91 km², passando para ±37,54 km² em 2000 e ±37,90 km em 2006, no ano de 2011 observou-se uma diminuição, com área de ±28,32 km², sendo que em 2015 a área voltou aos valores anteriores, ±34,09 km². A avaliação da temperatura do ar observada em Esperanza entre 1964-2014 mostra um aumento de 1,45°C. / This dissertation conducted a survey of variations of ice fronts in glaciers positions on the northern tip of the Trinity Peninsula by using remote sensing techniques. Advances and retreats of glaciers were mapped, as well as ice-free areas in the 27-year period between 1988-2015, and the results were complemented with air temperature data for the region. The database used eight satellite images from Landsat (TM, ETM + and OLI/TIRS sensors). In addition, it was used the Antarctica Digital Database (ADD) data, the Landsat Image Mosaic of Antarctica (LIMA), and the digital elevation model Antarctic Peninsula 100 m Digital Elevation Model (APGDEM). The temperature data used come from the Antarctic station Esperanza (ARG), acquired through READER. The glaciers ice fronts positions were obtained through automatic and manual methods. Unsupervised and supervised classifications were performed in the acquisition of these, turning them into vectors and uniting them with the delimitation of glacial drainage basins provided by ADD, thus forming the set of glaciers with its front position for each year of images (1988, 2000, 2006, 2011 and 2015). The ice-free areas were obtained by supervised classification. The classifications were validated through the Kappa index, obtaining satisfactory results. The total study area is approximately 1,450 square kilometers and has 32 glacial drainage basins, these, three are named glacier (Arena, Depot and Mondor), all three tidewater glaciers. In the period of analysis, since 1988, there has been a loss of mass of ice area of approximately 50 square kilometers, whereas the total gain was only ±10 square kilometers, resulting in an overall decrease of approximately ±40 square kilometers (i.e. ±2,7% of the total area). Between 1988-2000 (the wider range of investigations), the area lost ±25.1 square kilometers of ice on its fronts, from 2000 to 2006 there was a decrease of ±12.2 km², and between 2006 to 2011 others ±5.0 km²; the 2011-2015 interval was the only one to show advances greater that retreats with a ±2.5 sq km increase in the area (±0.16%). The Depot and Mondor glaciers showed retreat behavior, and Depot did not show any advance within the periods, the Arena glacier showed advances and retreats in all intervals, remaining virtually unchanged. The ice-free area increased by approximately 18 square kilometers, that is, a ±114% increase over the 1988 snow/ice free area. The largest increases were given in the years 1988-2000, in 1988 the area represented ±15.91 km², reaching ±37.54 km² in 2000 and ±37.90 km in 2006, in 2011 there was a decrease, with an area of ±28.32 square kilometers, and in 2015 the area returned to its previous values, ±34.09 km². The air temperature evaluation in Esperanza observed in 1964-2014 years show an increase of 1.45 ° C.

The objective of this study is to reconstruct the history of glaciation from the start of Fraser (Late Wisconsinan) Glaciation to the end of deglaciation, for three areas in the Cascade Mountains. The Cascade Mountains are located between the Coast Mountains and the Interior Plateau in southwestern British Columbia. The Coast Mountains were glaciated by mountain glaciation followed by frontal retreat, whereas the Interior Plateau underwent ice sheet glaciation followed by downwasting and stagnation. The Cascades were supposed to have undergone a style of glaciation transitional between these two. Terrain mapping on air photographs followed by field checking was used to locate surficial materials and landforms indicative of glaciation style and pattern. All three study areas were glaciated by mixed mountain and ice sheet glaciation. At the start of Fraser Glaciation, alpine and valley glaciers formed around higher summits as occurred in the Coast Mountains. At the glacial maximum the entire area was covered by the Cordilleran Ice Sheet. Deglaciation was largely by continuous downvalley retreat of active glaciers, contrasting with downwasting and stagnation in the Interior Plateau, and frontal retreat in the Coast Mountains. The scarcity of fresh moraines in the cirques suggests that, unlike in the Coast Mountains, most cirque glaciers were not active at the end of glaciation. Only the highest north facing cirques remained above the local snowline throughout deglaciation and, as a result, glaciers in these valleys remained active and retreated up valley. The pattern of glaciation in the Cascade Mountains was similar to that of other areas which underwent mixed mountain and ice sheet glaciation, such as the Presidential Range in New Hampshire, the Green Mountains in Vermont, mountain ranges in west central Maine and the Insular Mountains on Vancouver Island. However, deglaciation in al l areas was complex and depended strongly on local conditions. For this reason local patterns cannot be predicted easily on the basis of glaciation style. The value of an understanding of glaciation style to improve the accuracy of terrain mapping was also investigated. It was found that the model developed for the Cascade Mountains was of some use in predicting the presence of fine-textured material in valley bottoms and for the prediction of glaciofluvial material overlying till . However fine-textured sediments were not found in al l valleys which were predicted to contain them. The model appears to be most useful as an indicator of where to concentrate field checking in order to locate fine-textured sediments. / Arts, Faculty of / Geography, Department of / Graduate

Five periods of ice advance in the North Klondike-upper Blackstone basins of the Ogilvie Mountains are recognized by the downvalley sequence of progressively older moraines. The youngest occurred during the last millennium and is represented by glacierets and fresh moraines. The other advances are of the Pleistocene Epoch; from youngest to oldest they are: Age I (valley glacier stage), Age II (transection glacier), Age IIA (transection glacier with piedmont) and Age III (mountain ice cap). Evidence for Age III is limited to the north slope of the ranges. Age IIA was recognized only on the north slope and may represent a slightly older pulse of the Age II. This chronosequence is tentatively correlated with those elsewhere in the northern Cordillera. Within the region an array of surficial elements indicates that a continuous and discontinuous mosaic of processes have operated interdependently during the Quaternary. A product of these processes is mapped under one of eight facies - attention being directed to the varieties of features associated with the glacial and periglacial cycles. Of the latter, active, inactive and degradational forms exist. Strong correlations between the distribution of some types of surficial features and the underlying bedrock geology are recognized. No changes in morphology, permafrost distribution, pebble weathering, pedogenesis and floral succession could be related to the ages of the Pleistocene moraines. The influence of permafrost on all ages of moraines, the variability in their environment of deposition, and an edaphic and climatic discontinuity produce greater differences than does the age factor. In the northern half of the study area, permafrost and associated phenomena were observed to greatly retard chemical alteration; on the other hand, they permit the development of only a vegetational and pedological "polyclimax", rather than a single mesic climax, in a time span of less than 11,000-15,000 years. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

By only considering records of climate and glaciers over the period that humans have been monitoring them, one might think that climate normally changes quite rapidly, and that glaciers have always been small. But in the not-so-distant past, an ice sheet covered the Southern Andes, flowing across the southern tip of the continent, and in some places, even terminating into the Atlantic Ocean. Glaciers rewrite the surfaces they inhabit, leaving behind indicators of their past behavior. By studying the landforms they create, we can reconstruct climates of the past. Here I present unique and novel glacier-climate reconstructions over southern and central Patagonia using a state-of-the-art dating approach tied to high resolution spatial mapping and glaciological modeling. The main goal of this thesis is to constrain the precise timing and character of the past advances of three glaciers in Patagonia. To this end, I present new precise 10Be surface exposure datasets from two paleo outlet glacier lobes (at 45°S and 53°S), totaling 71 new moraine boulder ages. In these two valleys, I am able to reconstruct the last three major glaciations (MIS 6, 4, 2), as well as provide a constraint for the last two terminations (T1, T2). At a third site, I create a novel dataset to reconstruct the behavior of the Calluqueo glacier (48°S) from ~7,000 years ago to the present. All three sites are eastwards of the main Andes mountain range, spanning from southernmost Patagonia (53°S) to central Patagonia (45°S). To achieve my thesis objectives, I employed recent improvements in the 10Be exposure dating method, and tied the geochronological studies to new, high resolution maps of the glacial geomorphology created by the former glaciers and associated processes. We find in central Patagonia, the Ñirehuao glacier lobe was most extensive potentially during Marine Isotope Stage (MIS) 8, but certainly prior to MIS 6, followed by a major advance during MIS 6. This study presents one of the first directly dated records of a MIS 6 glacier expansion in Patagonia at 153±5.1 ka, where the glacier may have been in retreat at 137±4.2 ka. During the last glacial cycle, the glacier was most extensive during the middle of MIS 2, at 23.6±0.9 ka. The southernmost section of the Ice Sheet, at Estrecho de Magallanes, was more extensive during Marine Isotope Stage 4 (MIS 4) than during MIS 2, representing the first direct dating of the MIS 4 glacier culmination in South America. Similar to the MIS 2 glacial maximum, within MIS 4 there were multiple advances that we date (6 samples) to between 67.5±2.1 and 62.1±2.0 ka. Inboard of the MIS 4 moraine complex, we date a sequence of geomorphically distinct MIS 2 moraines that represent separate major periods of glacial stability. The MIS 2 maximum extent occurred by 27.4±0.8 ka and was followed by at least four more full glacial culminations over a hundred miles beyond the Andes mountains. About 18 km inboard of the main MIS 2 landforms, the sequence is followed by smaller-scale recessional moraine crests that we date to 18.0±0.8 ka, indicating the glacier was in net retreat at this time. In order to estimate the climate conditions necessary to drive the glacier advances that we date and map, we apply the University of Maine Ice Sheet Model to the Estrecho de Magallanes and Ñirehuao records. Tentative results suggest that the Magallanes lobe may have reached mapped inner and outer MIS 2 moraines with a climate that had approximately 4.5°C and 5.5°C cooler summers, respectively, assuming about 25% less annual precipitation relative to modern conditions. A new record at Calluqueo, in central Patagonia, allows us to reconstruct Holocene (interglacial) glacier changes. Using 33 new 10Be ages with unprecedented precision, geomorphic mapping and historical imagery, we find that the Calluqueo glacier sat at its mid-Holocene maximum extent from ~6,900 until ~6,700 years before the present. Major moraine forming advances subsequently culminated at least seven more times, averaging every 500±31 years, between 5,620±203 and 3,120±106 years ago. A hiatus in moraine formation occurred from 3,120±106 until 1,160±50 years ago (860 CE). Major retreat occurred between 1600-1800 CE, followed by stability from 1800-1940 CE, and pronounced ongoing retreat since after 1940 CE. For the Holocene period, this record represents one of the first precise, directly-dated glacier histories from central Patagonia, and one of the few available for all of Patagonia. The timing of advances of the Calluqueo glacier has little in common with the glacial histories from the Northern Hemisphere, suggesting an inter-hemispheric asynchronicity. All together, we reconstruct the timing of glacial maxima at three sites in terrestrial Patagonia from 53°S to 45°S, with unprecedented precision, from pre-MIS 6 to the present day.

Thesis advisor: Jeremy D. Shakun / Glaciers in the tropics have retreated over recent decades, but whether the magnitude of this retreat has exceeded the bounds of past Holocene fluctuations is unclear. In this study, we measure cosmogenic 10Be and 14C concentrations from recently exposed bedrock at the margin of five glaciers in the tropical Andes, including four small glaciers and the Quelccaya Ice Cap, the world’s largest tropical ice mass. Concentrations at the Quelccaya Ice Cap margin suggest there was extended exposure during the first half of the Holocene, but that the site was covered by ice for the last 5 kyr. In contrast, nuclide concentrations are strikingly low in all samples at the margins of the four small glaciers, equivalent to ~200 years of 14C and 50 years of 10Be accumulation at surface production rates. These data suggest that the small tropical glaciers are now smaller than they have been at any point during the Holocene, whereas the Quelccaya Ice Cap has not yet retreated to its smallest extent of the Holocene, likely due to its larger size and slower response time. / Thesis (MS) — Boston College, 2021. / Submitted to: Boston College. Graduate School of Arts and Sciences. / Discipline: Earth and Environmental Sciences.

Rock glaciers are tongue-shaped or lobate masses of rock debris which occur below cliffs and talus in many alpine regions. They are best developed in continental alpine climates where it is cold enough to preserve a core or matrix of ice within the rock mass but insufficiently snowy to produce true glaciers. Previous reports have identified and briefly described several rock glaciers in the Olympic Mountains, Washington {Long 1975a, pp. 39-41; Nebert 1984), but no detailed integrative study has been made regarding the geomorphic character, age,and distribution of these features.

No description available.