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John A Matthews - One of the best experts on this subject based on the ideXlab platform.

  • holocene chemical weathering surface lowering and rock weakening rates on glacially eroded bedrock surfaces in an alpine Periglacial Environment jotunheimen southern norway
    Permafrost and Periglacial Processes, 2011
    Co-Authors: John A Matthews, Geraint Owen
    Abstract:

    Indices of the rate of Holocene chemical weathering of pyroxene-granulite gneiss and peridotite are estimated from bedrock surfaces deglaciated c. 9700 years ago. A mean surface lowering rate for pyroxene-granulite gneiss of 4.8 ± 1.0 mm ka−1 is estimated from the mean height of upstanding quartz veins, and Schmidt hammer R-values are used to validate the reference-surface method. Microrelief development and crack-widening rates for peridotite are 2.6 ± 1.1 mm ka−1 and 1.8 ± 0.4 mm ka−1, respectively. Well-developed weathering rinds indicate a mean rind development rate for peridotite of 0.6 ± 0.1 mm ka−1. New indices of rock surface weakening (IRW) and the rock surface weakening rate (WR) are defined in relation to Schmidt hammer mean R-values. IRW values from weathered and unweathered surfaces of known age are 38.7 per cent for gneiss and 34.1–59.2 per cent (depending on the texture of the weathered rock surface) for peridotite: corresponding WR values are 2.7 R-units ka−1 and 2.1–3.7 R-units ka−1, respectively. Our methods and results are evaluated, particularly in relation to previous research and other rock types in Scandinavia. The various indices, being affected in different ways by biochemical and biological mechanical weathering and micro-erosion, are regarded as complementary aids in the investigation of both the effects of chemical weathering and its rate. Copyright © 2010 John Wiley & Sons, Ltd.

  • lake shoreline development frost weathering and rock platform erosion in an alpine Periglacial Environment jotunheimen southern norway
    Boreas, 2008
    Co-Authors: John A Matthews, Alastair G Dawson, Richard A Shakesby
    Abstract:

    Ice-dammed lake Boverbrevatnet existed for 75–125 years in the ‘Little Ice Age’. After about A.D. 1826, glacier retreat led to a fall in lake level and to exposure of the former shoreline, which includes well-developed platforms cut in metamorphic bedrock. The rock platforms, up to 5.3 m wide and backed by cliffs up to 1.55 m high, are partially covered by large angular boulders which form pavements. Accurate levelling has permitted correlation of platform fragments, overflow cols and related features of the shoreline, such as benches eroded in moraines, ice-push ridges, a perched delta, vegetation trim-lines, lichen limits and a ‘lichen-kill’ zone. The evolution of the lake, the chronology of deglaciation and the period of formation of the rock platforms have been dated by lichenometry, supported by 14C dating, Schmidt hammer ‘R’-values and historical data. The morphology of the rock platforms, together with estimates of their rate of erosion ranging from 1.4 to 7.1 cm/year, indicate the importance of frost shattering (frost riving, frost wedging or macrogelivation) at the lake margin under a Periglacial climate, while the permanence of such platforms as landscape features suggests their use in the reconstruction of former Periglacial Environments. A semi-quantitative model is outlined for the development of rock platforms which emphasises deep penetration of the annual freeze-thaw cycle, the movement of unfrozen lake water towards the freezing plane, and the growth of segregation ice in fissures and cracks at the interface between lake ice and bedrock. Ice-push and ice-pull processes are involved primarily as transporting agents in the formation of boulder pavements and in the removal of debris from the platforms. Analogous processes may occur on polar coasts producing coastal rock platforms.

  • rapid holocene chemical weathering on a calcitic lake shoreline in an alpine Periglacial Environment attgloyma sognefjell southern norway
    Permafrost and Periglacial Processes, 2006
    Co-Authors: Geraint Owen, John A Matthews, Richard A Shakesby
    Abstract:

    A small lake (Attgloyma) at an altitude of about 1220 m in the low-alpine zone, southern Norway, has a shore platform in calcitic and quartzitic muscovite-chlorite schists. The platform has recently been exposed by a fall in lake level due to upstream dam construction and exhibits micro-landforms ranging from pits and grooves to upstanding crenulate ridges produced by differential chemical weathering under relatively constant conditions over the last ca. 10 000 years. The maximum surface lowering rate of the calcitic layers estimated from differential weathering is 35 mm ka−1, which is about an order of magnitude greater than most previous estimates from alpine and polar Periglacial Environments. Average bedrock surface lowering across the whole platform reached a maximum of 15.5 ± 2.2 mm ka−1 in a vertical zone corresponding with the former lake level, declining to negligible values around 0.7 m below lake level. Differential weathering and bedrock surface lowering were also negligible immediately above lake level. Correspondence of maximum surface lowering rates with the former lake level and a shoreline notch at the back of a platform suggest that the effects of solutional weathering of the calcite have been enhanced by water movement generated by small lake-surface waves. Copyright © 2006 John Wiley & Sons, Ltd.

Richard A Shakesby - One of the best experts on this subject based on the ideXlab platform.

  • lake shoreline development frost weathering and rock platform erosion in an alpine Periglacial Environment jotunheimen southern norway
    Boreas, 2008
    Co-Authors: John A Matthews, Alastair G Dawson, Richard A Shakesby
    Abstract:

    Ice-dammed lake Boverbrevatnet existed for 75–125 years in the ‘Little Ice Age’. After about A.D. 1826, glacier retreat led to a fall in lake level and to exposure of the former shoreline, which includes well-developed platforms cut in metamorphic bedrock. The rock platforms, up to 5.3 m wide and backed by cliffs up to 1.55 m high, are partially covered by large angular boulders which form pavements. Accurate levelling has permitted correlation of platform fragments, overflow cols and related features of the shoreline, such as benches eroded in moraines, ice-push ridges, a perched delta, vegetation trim-lines, lichen limits and a ‘lichen-kill’ zone. The evolution of the lake, the chronology of deglaciation and the period of formation of the rock platforms have been dated by lichenometry, supported by 14C dating, Schmidt hammer ‘R’-values and historical data. The morphology of the rock platforms, together with estimates of their rate of erosion ranging from 1.4 to 7.1 cm/year, indicate the importance of frost shattering (frost riving, frost wedging or macrogelivation) at the lake margin under a Periglacial climate, while the permanence of such platforms as landscape features suggests their use in the reconstruction of former Periglacial Environments. A semi-quantitative model is outlined for the development of rock platforms which emphasises deep penetration of the annual freeze-thaw cycle, the movement of unfrozen lake water towards the freezing plane, and the growth of segregation ice in fissures and cracks at the interface between lake ice and bedrock. Ice-push and ice-pull processes are involved primarily as transporting agents in the formation of boulder pavements and in the removal of debris from the platforms. Analogous processes may occur on polar coasts producing coastal rock platforms.

  • rapid holocene chemical weathering on a calcitic lake shoreline in an alpine Periglacial Environment attgloyma sognefjell southern norway
    Permafrost and Periglacial Processes, 2006
    Co-Authors: Geraint Owen, John A Matthews, Richard A Shakesby
    Abstract:

    A small lake (Attgloyma) at an altitude of about 1220 m in the low-alpine zone, southern Norway, has a shore platform in calcitic and quartzitic muscovite-chlorite schists. The platform has recently been exposed by a fall in lake level due to upstream dam construction and exhibits micro-landforms ranging from pits and grooves to upstanding crenulate ridges produced by differential chemical weathering under relatively constant conditions over the last ca. 10 000 years. The maximum surface lowering rate of the calcitic layers estimated from differential weathering is 35 mm ka−1, which is about an order of magnitude greater than most previous estimates from alpine and polar Periglacial Environments. Average bedrock surface lowering across the whole platform reached a maximum of 15.5 ± 2.2 mm ka−1 in a vertical zone corresponding with the former lake level, declining to negligible values around 0.7 m below lake level. Differential weathering and bedrock surface lowering were also negligible immediately above lake level. Correspondence of maximum surface lowering rates with the former lake level and a shoreline notch at the back of a platform suggest that the effects of solutional weathering of the calcite have been enhanced by water movement generated by small lake-surface waves. Copyright © 2006 John Wiley & Sons, Ltd.

Geraint Owen - One of the best experts on this subject based on the ideXlab platform.

  • holocene chemical weathering surface lowering and rock weakening rates on glacially eroded bedrock surfaces in an alpine Periglacial Environment jotunheimen southern norway
    Permafrost and Periglacial Processes, 2011
    Co-Authors: John A Matthews, Geraint Owen
    Abstract:

    Indices of the rate of Holocene chemical weathering of pyroxene-granulite gneiss and peridotite are estimated from bedrock surfaces deglaciated c. 9700 years ago. A mean surface lowering rate for pyroxene-granulite gneiss of 4.8 ± 1.0 mm ka−1 is estimated from the mean height of upstanding quartz veins, and Schmidt hammer R-values are used to validate the reference-surface method. Microrelief development and crack-widening rates for peridotite are 2.6 ± 1.1 mm ka−1 and 1.8 ± 0.4 mm ka−1, respectively. Well-developed weathering rinds indicate a mean rind development rate for peridotite of 0.6 ± 0.1 mm ka−1. New indices of rock surface weakening (IRW) and the rock surface weakening rate (WR) are defined in relation to Schmidt hammer mean R-values. IRW values from weathered and unweathered surfaces of known age are 38.7 per cent for gneiss and 34.1–59.2 per cent (depending on the texture of the weathered rock surface) for peridotite: corresponding WR values are 2.7 R-units ka−1 and 2.1–3.7 R-units ka−1, respectively. Our methods and results are evaluated, particularly in relation to previous research and other rock types in Scandinavia. The various indices, being affected in different ways by biochemical and biological mechanical weathering and micro-erosion, are regarded as complementary aids in the investigation of both the effects of chemical weathering and its rate. Copyright © 2010 John Wiley & Sons, Ltd.

  • rapid holocene chemical weathering on a calcitic lake shoreline in an alpine Periglacial Environment attgloyma sognefjell southern norway
    Permafrost and Periglacial Processes, 2006
    Co-Authors: Geraint Owen, John A Matthews, Richard A Shakesby
    Abstract:

    A small lake (Attgloyma) at an altitude of about 1220 m in the low-alpine zone, southern Norway, has a shore platform in calcitic and quartzitic muscovite-chlorite schists. The platform has recently been exposed by a fall in lake level due to upstream dam construction and exhibits micro-landforms ranging from pits and grooves to upstanding crenulate ridges produced by differential chemical weathering under relatively constant conditions over the last ca. 10 000 years. The maximum surface lowering rate of the calcitic layers estimated from differential weathering is 35 mm ka−1, which is about an order of magnitude greater than most previous estimates from alpine and polar Periglacial Environments. Average bedrock surface lowering across the whole platform reached a maximum of 15.5 ± 2.2 mm ka−1 in a vertical zone corresponding with the former lake level, declining to negligible values around 0.7 m below lake level. Differential weathering and bedrock surface lowering were also negligible immediately above lake level. Correspondence of maximum surface lowering rates with the former lake level and a shoreline notch at the back of a platform suggest that the effects of solutional weathering of the calcite have been enhanced by water movement generated by small lake-surface waves. Copyright © 2006 John Wiley & Sons, Ltd.

Villarroel, Cristian Daniel - One of the best experts on this subject based on the ideXlab platform.

  • Características hidrológicas del ambiente Periglacial de montaña y estructura interna de glaciares de escombros en los andes centrales de San Juan
    2020
    Co-Authors: Villarroel, Cristian Daniel
    Abstract:

    En la provincia de San Juan el ambiente Periglacial se desarrolla en forma extensa en la cabecera de las cuencas andinas, las cuales constituyen las fuentes de recarga de los sistemas hídricos que abastecen de agua a toda la población. Si bien los aspectos geomorfológicos, hidrológicos, climáticos y paleoclimáticos, entre otros, del ambiente Periglacial han recibido mayor atención en los últimos años, aún resta mucho para comprender las complejas interrelaciones entre los diferentes procesos actuantes. En este sentido, el presente trabajo constituye la primera investigación que combina estudios hidrológicos, hidroquímicos, isotópicos, geofísicos, geomorfológicos y dinámicos en una cuenca netamente Periglacial con el objetivo de determinar los patrones espacio-temporales de los flujos superficiales, las características y el origen de las diferentes fuentes de agua que constituyen los ríos cordilleranos e identificar la estructura interna de glaciares de escombros y sus flujos de circulación. Para lo cual, se han considerados dos escalas de trabajo, escala de cuenca y escala de geoforma (glaciar de escombros).El tramo superior de la cuenca del río Santa Cruz, área de estudio del presente trabajo, es una cuenca con condiciones actuales netamente Periglaciales. Habiendo sufrido en el pasado condiciones glaciarias, evidenciado a partir de diferentes rasgos morfológicos. Existe una amplia variedad de geoformas Periglaciales que van desde la micro a la meso escala. Entre ellas se tiene a los glaciares de escombros, los cuales constituyen una de las geoformas más notorias. De los 180 glaciares de escombros inventariados, 83 son activos, 90 inactivos y el resto fósiles o relictos. Los cuales ocupan un área de 8,15 Km2, 4,34 Km2 y 0,37 Km2 respectivamente, y presentan una distribución altitudinal que varía desde 3576 y 3438 m s.n.m. hasta 4673 y 4571 m s.n.m. para los límites inferior y superior de los glaciares de escombros activos e inactivos, respectivamente. Además, se han inventariado 210 geoformas consideradas como protalus rampart, las cuales poseen en conjunto un área de 1,54 Km2 y una altura promedio de 3980 m s.n.m.La fusión nival constituye uno de los principales componentes del hidrograma de ríos cordilleranos y muestra su pico de descarga a finales de primavera o principio de verano, con caudales cercanos a los 6 m3/s en el río Santa Cruz, que decaen a casi la mitad durante el período de sequía hídrica (2010-2015). Otro aspecto importante a destacar del hidrograma es la presencia de una pequeña inflexión (aumento) en la curva de caudales a finales de verano-principios de otoño (marzo-abril). Este aumento estaría vinculado a la fusión del hielo subterráneo presente principalmente en capa activa de áreas con permafrost, el cual presenta un retardo respecto a la fusión nival. En los períodos de sequía, el caudal aportado por fusión de hielo subterráneo llegaría a representar hasta el 63% del flujo total.Los valores de conductividad eléctrica de las diferentes fuentes de agua constituyen una buena aproximación para determinar su origen. Existe una alta variabilidad entre los valores de diferentes fuentes, pero también en ocasiones existe alta variabilidad entre muestras de la misma fuente de agua. Por lo cual, es un parámetro que necesita ser complementado. El río Santa Cruz presenta un comportamiento de decaimiento en sus valores de conductividad a partir de valores altos cerca de la cabecera de la cuenca, influenciado principalmente por los flujos salinos provenientes de la quebrada donde se localiza el glaciar de escombros El Gigante. Mientras que en su tramo medio e inferior los valores de conductividad van disminuyendo, debido a la buena calidad de sus afluentes, los cuales tienen sus cabeceras en sectores elevados. Los termokarst o estructuras deprimidas, sobre glaciares de escombros, constituyen una de las fuentes de agua con mayor variabilidad entre sus valores, indicando la presencia de diferentes orígenes del agua y procesos. Por su parte, los valores de temperatura permiten identificar agua proveniente de la fusión de nieve o hielo subterráneo o en contacto con el permafrost.El contenido iónico de las diferentes fuentes de agua indica un tipo de agua bicarbonatada y sulfatada sódica, con alta variabilidad en el contenido de los aniones. La mayor correlación lineal se observa entre los valores de SO4-2 y Ca+ con desplazamiento hacia valores enriquecidos de SO4-2, indicando disolución de formaciones evaporíticas y oxidación de sulfuros. Los valores más elevados de concentración iónica fueron detectados en las muestras de glaciares de escombros, indicando que estos actúan como un medio de concentración.Por su parte, la composición isotópica de las diferentes fuentes de agua también constituye un trazador natural que permite, en combinación con la hidroquímica y los parámetros físico-químicos, determinar el origen del agua. Los manchones de nieve son los que presentan mayor variabilidad en su composición, con valores de entre -13,3? y -22,1? δ18O y de -104,2? y -172,2? δ2H. Además, se ha identificado el control de la elevación en la composición isotópica de la nieve a través del coeficiente de determinación (r2) con un valor de 0,58 y 0,68 para δ2H y δ18O respectivamente. Mientras que, procesos de redistribución isotópica por metamorfismo y fusión de la nieve han sido evidenciados principalmente en los bancos de nieve en la raíz de un glaciar de escombros. Los principales afluentes del río Santa Cruz reflejan en su composición la altitud de sus cabeceras, con valores de δ18O y δ2H más empobrecidos en los afluentes con sus cabeceras más elevadas.La aplicación de Tomografía de Resistividad Eléctrica (TRE), el método geofísico más ampliamente utilizado en permafrost de montaña, ha permitido identificar la presencia de hielo en glaciares de escombros y determinar su estructura interna. Sobre el glaciar de escombros El Gigante se han desarrollado 8 perfiles de entre 110 y 130 m de longitud en diferentes sectores del mismo. En general, la capa activa presenta una geometría irregular con espesores que varían de 3 a 10 m y valores de resistividad entre 200 y 8000 Ω.m e incluso llegando a valores de hasta 30K Ω.m. En los sectores de capa activa donde las resistividades disminuyen hasta valores de 80-90 Ω.m se infiere la presencia de agua. La capa de permafrost también presenta una geometría irregular con zonas de discontinuidad espacial y con valores de resistividad que varían entre 8 y 150 K Ω.m. Si bien estos valores se encuentran en el rango bajo de los registrados para otros glaciares de escombros, la cantidad, granulometría y tipo de detrito presente tendría una influencia importante. A pesar de no poder realizar una comparación directa con otros glaciares de escombros debido al contexto geológico local donde se desarrolla El Gigante, si ha sido posible identificar sitios con mayor contenido de hielo sobre la misma geoforma.Por su parte, el perfil de TRE realizado sobre el glaciar de escombros Ojotas I, de claro origen criogénico, indica una capa activa con espesor de 2 a 6 m y valores de resistividad de 700 a 20.000 Ω.m. Por debajo se desarrolla la capa de permafrost que alcanza los 172 K Ω.m de resistividad.Por último, la combinación de métodos hidroquímicos, isotópicos, geofísicos, geomorfológicos y dinámicos sobre una misma geoforma, el glaciar de escombros El Gigante, ha permitido identificar los flujos internos de circulación de agua a través de canales preferenciales, sin conexión entre ellos en algunos casos. Además, se ha podido establecer los sectores que presentan degradación de permafrost y determinar el diferente grado de actividad de los diferentes sectores de esta geoforma.In the province of San Juan, the Periglacial Environment develops extensively in the headwaters of the Andean basins, which are the sources of recharge of the water systems that supply water to the entire population of the province. Although the geomorphological, hydrological, climatic and paleoclimatic aspects, among others, of the Periglacial Environment have received more attention in recent years, there is still much to understand the complex interrelations between the different processes involved. In this sense, the present work constitutes the first research that combines hydrological, hydrochemical, isotopic, geophysical, geomorphological and dynamic studies in a clearly Periglacial basin with the objective of determining the spatio-temporal patterns of surface flows, characteristics and origin of the different sources of water that make up the Andean rivers and identify the internal structure of debris glaciers and their circulation flows. For which, two scales of work have been considered: basin scale and landform scale (debris glacier). The upper section of the Santa Cruz river basin, the study area of this work, is a basin with clearly Periglacial current conditions. Having suffered in the past glacial conditions, evidenced from different morphological features. There is a wide variety of Periglacial landforms ranging from the micro to the meso scale. Among them are the rock glaciers, which are one of the most notorious ones. Of the 180 inventoried rock glaciers, 83 are active, 90 inactive and the rest fossils or relicts, occupying an area of 8.15 km2, 4.34 km2 and 0.37 km2 respectively, with an altitudinal distribution that varies from 3576 and 3438 meters to 4673 and 4571 m.a.s.l. for the lower and upper limits of the active and inactive rock glaciers respectively. In addition, 210 landforms considered as protalus rampart have been inventoried, which together have an area of 1.54 km2 and an average height of 3980 meters above sea level. The snow melt is one of the main components of the cordilleran river hydrograph and shows its discharge peak at the end of spring or early summer, with flows close to 6 m 3 /s in the Santa Cruz River, which fall by almost half during the period of water drought (2010-2015). Another important aspect of the hydrograph is the presence of a small inflection (increase) in the flow curve in late summer-early autumn (MarchApril). This increase would be linked to the melting of the underground ice present mainly in the active layer of areas with permafrost, which presents a delay with respect to the snow melt. In periods of drought, the flow contributed by melting underground ice would reach up to 63% of the total flow. The electrical conductivity values of the different water sources are a good approximation to determine their origin. There is a high variability between the values of different sources, but there is also sometimes high variability between samples from the same water source. Therefore, it is a parameter that needs to be complemented. The Santa Cruz River shows a behavior of decay in its conductivity values from high values near the head of the basin, influenced mainly by the saline flows coming from the area where the El Gigante rock glacier is located. While in the middle and lower sections the conductivity values are decreasing, due to the good quality of its tributaries, which have their headwaters in high sectors. Thermokarst is one of the sources of water with high variability between its values, indicating the presence of different origins of water and processes. On the other hand, the temperature values allow identifying water coming from the melting of snow or underground ice or in contact with the permafrost. The ionic content of the different water sources indicates a type of bicarbonated and sulphated sodium water, with high variability in the content of the anions. The highest linear correlation is observed between the values of SO4-2 and Ca + with displacement towards enriched values of SO4-2 , indicating dissolution of evaporite formations and oxidation of sulfides. The highest values of ionic concentration are found in the samples of rock glaciers, indicating that these act as a means of concentration. For its part, the isotopic composition of the different water sources also constitutes a natural tracer that allows, in combination with hydrochemical and physical-chemical parameters, to determine the origin of water. The snow patches are those that present greater variability in their composition, with values between -13.3 ‰ and -22.1 ‰ δ 18O and -104.2 ‰ and -172.2 ‰ δ2H. In addition, control of the elevation in the snow isotopic composition has been identified through the coefficient of determination (R2 ) with a value of 0.58 and 0.68 for δ2H and δ18O respectively. While, isotopic redistribution processes by metamorphism and melting snow have been evidenced mainly in the snow banks at the root of a debris glacier. The main tributaries of the Santa Cruz River reflect in their composition the altitude of their headwaters, with more depleted values in the tributaries with their higher headwaters. The use of Electrical Resistivity Tomography (TER), the most widely used geophysical method in mountain permafrost, has made it possible to identify the presence of ice in rock glaciers and determine its internal structure. On the El Gigante rock glacier, 8 profiles of 110 m to 130 m in length have been developed in different sectors of the same. In general, active layer presents an irregular geometry with thicknesses ranging from 3 to 10 m and values of resistivity between 200 and 8000 Ω.m and even reaching values of up to 30K Ω.m. In the active layer sectors where the resistivities decrease to values of 80-90 Ω.m, the presence of water is inferred. While, the permafrost layer also presents an irregular geometry with zones of spatial discontinuity and with values of resistivity that vary between 8 and 150 K Ω.m. Although these values are in the low range of those registered for other debris glaciers, the amount, granulometry and type of debris present would have an important influence. Despite not being able to make a direct comparison with other rock glaciers due to the local geological context where El Gigante is developed, it has been possible to identify sites with higher ice content on the same landform. On the other hand, the TRE profile made on a Talus rock glacier of clear Periglacial origin indicates an active layer with a thickness of 2 to 6 m and resistivity values of 700 to 20,000 Ω.m. Underneath, the permafrost layer that reaches 172 K Ω.m of resistivity is developed. Finally, the combination of hydrochemical, isotopic, geophysical, geomorphological and dynamic methods on the same landform, El Gigante rock glacier, has allowed to identify the internal flows of water circulation through preferential channels without connection between them in some cases. In addition, it has been possible to establish the sectors that present degradation of permafrost and determine the different degree of activity of the different sectors of this landform.Fil: Villarroel, Cristian Daniel. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geología; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Autor

  • DInSAR for a Regional Inventory of Active Rock Glaciers in the Dry Andes Mountains of Argentina and Chile with Sentinel-1 Data
    'MDPI AG', 2018
    Co-Authors: Villarroel, Cristian Daniel, Forte, Ana Paula, Tamburini Beliveau Guillermo, Monserrat Oriol, Morvillo, Mónica Cristina
    Abstract:

    The Dry Andes region of Argentina and Chile is characterized by a highly developed Periglacial Environment. In these arid or semi-arid regions, rock glaciers represent one of the main pieces of evidence of mountain creeping permafrost and water reserves in a solid state. However, their distribution, degree of activity, and response to global warming are not yet well understood. In this context, this work aims to show the potential of the Sentinel-1-based interferometric technique (DInSAR) to map active rock glaciers at a regional level. In particular, the paper presents an active rock glacier inventory for the study area, which covers approximately 40,000 km2, ranging from latitude 30°210S to 33°210S. A total of 2116 active rock glaciers have been detected, and their elevations show a high correlation with the west-east direction. This result was obtained by using only 16 interferometric pairs. Compared to other remote sensing classification techniques, the interferometric technique offers a means to measure surface displacement (active rock glacier). This results in a reliable classification of the degree of activity compared to other methods, based on geomorphological, geomorphometric, and/or ecological criteria. This work presents evidence of this aspect by comparing the obtained results with existing optical data-based inventories. We conclude that the combination of both types of sensors (radar and optical) is an appropriate procedure for active rock glacier inventories, as both mapping methodologies are complementary.Fil: Villarroel, Cristian Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geología; ArgentinaFil: Tamburini Beliveau, Guillermo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional de Rosario; ArgentinaFil: Forte, Ana Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Monserrat, Oriol. Agencia Espacial Europea; EspañaFil: Morvillo, Mónica Cristina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales; Argentin

  • Impact of natural parameters on rock glacier development and conservation in subtropical mountain ranges. Northern sector of the Argentine Central Andes
    'Copernicus GmbH', 2016
    Co-Authors: Forte, Ana Paula, Villarroel, Cristian Daniel, Esper Angillieri, María Yanina
    Abstract:

    This paper presents a detailed rock glacier inventory used in determining how the various natural parameters affect a mountain Periglacial Environment. This study was undertaken in a northernmost sector of the central Argentine Andes, in an area stretching between 31°02´ and 31°22´ S latitude. This is a high and arid subtropical region where permafrost and cryogenic processes are predominant, featuring as well as a large number of rock glaciers and associated Periglacial landforms. Rock glaciers inventory was based on geomorphological characterization with optical remote sensing data and field description information. The study region covers 630 km2, with 3,25 % of this area showing 402 rock glaciers and protalus rampart features. In total, 172 rock glaciers have been identified, 48 of which are considered active. In such a sector, the protalus rampart range shows the largest landform occurrences, though fossil and inactive rock glaciers are usually larger and are developed over a larger attitudinal distribution. Based on previous studies, we have considered that the study of active rock glaciers is an effective approach to assess the current state of Periglacial Environment evolution. Therefore, we analysed their spatial distribution and their relationship through different variables, by resorting to statistical analysis and a frequency ratio method. The chosen natural parameters were: Lithology, Elevation, Latitude and Longitude,Aspect, Slope and Annual Potential Solar Incoming Radiation. Analytical results have demonstrated that active rock glaciers landforms lie above 3.600 m.a.s.l. elevations, on 11° to 28° slopes with predominating south facing aspect and relatively low solar radiation. The statistical analysis shows that elevation, lithology and aspect are the most influencing factors for current Periglacial Environment development while rock glacier conservation is mainly controlled by lithology. On the study area, the annual potential solar radiation show high values but there is not any significant difference between landform and, therefore, it is scarcely influential. The research is carried out over a high mountain area where poor accessibility hindered the chances for obtaining systematic data on weather and Environment. A simple and low coast methodology was used to analyse an area where no studies on rock glacier distribution had been made before. This information gains special importance because Argentina has recently instituted a national law for glacial and Periglacial Environment protection and conservation. Therefore, this research and its results may contribute a significant step toward knowing the number, features and distribution of rock glacier bodies lying in a scarcely studied region.Fil: Forte, Ana Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; ArgentinaFil: Villarroel, Cristian Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan; Argentina. Universidad Nacional de San Juan. Facultad de Ciencias Exactas, Físicas y Naturales. Departamento de Geología; ArgentinaFil: Esper Angillieri, María Yanina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - San Juan. Centro de Investigaciones de la Geosfera y Biosfera. Universidad Nacional de San Juan. Facultad de Ciencias Exactas Físicas y Naturales. Centro de Investigaciones de la Geosfera y Biosfera; Argentin

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  • Periglacial tarn on the rock and pillar range crest south central south island new zealand and its surrounding snowbank community
    Austral Ecology, 2016
    Co-Authors: Alan F Mark, Ulf Molau, Peter A Whigham, Lorna Little, J A Nielsen
    Abstract:

    A small 18 × 1–5 m, distinctive, teardrop-shaped alpine tarn about 55-cm deep with a variable schist plate rock-silty bed, a wetland rim and surrounding snowbank community is described from a shallow depression in the headwaters of a small primary stream at 1400 m on the crest of the Rock and Pillar Range (1450 m), south-central South Island, New Zealand. Its initiation some 2500–3000 years ago (based on radiocarbon dating of peaty material near the base of the dam front) may have been serendipitous, but the prevailing Periglacial Environment of the area, involving seasonal freezing of the pond surface, has probably been conducive to its maintenance and slow extension. Despite some floristic similarities, it differs from any known alpine tarns, and a request via a YouTube video has not revealed any similar features.

  • intensity and spatio temporal variability of fluvial sediment transfers in an arctic oceanic Periglacial Environment in northernmost swedish lapland latnjavagge catchment
    Geomorphology, 2006
    Co-Authors: Achim A Beylich, Ulf Molau, Olga Sandberg, Susan Wache
    Abstract:

    Abstract Intensity and spatio-temporal variability of fluvial sediment transfers and mechanical fluvial denudation were analyzed in the Periglacial Latnjavagge catchment (9 km 2 ; 950–1440 m a.s.l.; 68.20N, 18.30E) in Arctic-oceanic northernmost Swedish Lapland. The present-day rates of fluvial sediment transfer are low. The mean annual mechanical fluvial denudation rate at the inlet of lake Latnjajaure, as calculated after five years of process monitoring (2000–2004), and excluding a “rare rainfall event” which caused 3.2 times higher suspended sediment transport during one day as compared to the total mean annual suspended sediment transport, is 2.3 t km − 2 yr − 1 . In years without “rare rainfall events”, most of the total annual sediment load is transported in a few days during annual snowmelt runoff. In the calculation of longer-term sediment budgets, rare rainfall events like the July 20th–21st, 2004 event have to be considered as essential components. Reliable estimation of the recurrence intervals of such events is problematic. The pattern of ice patches and snow fields within the valley, the steepness of streams and channels and the location of areas showing slushflow activity are the major factors controlling spatial variability of mechanical fluvial denudation in the drainage basin. The five lakes in Latnjavagge, especially lake Latnjajaure, are significant sediment traps and ground below 1300 m a.s.l. is protected by a very stable and closed vegetation cover and rhizosphere across the entire lower catchment.

  • rates of chemical and mechanical fluvial denudation in an arctic oceanic Periglacial Environment latnjavagge drainage basin northernmost swedish lapland
    Arctic Antarctic and Alpine Research, 2005
    Co-Authors: Achim A Beylich, Ulf Molau, Karina Luthbom, Dorothea Gintz
    Abstract:

    Abstract A process geomorphological investigation was started in 1999 to study present denudation rates and the mutual relationship of chemical and mechanical fluvial denudation in Periglacial Environments. Latnjavagge (9 km2; 950–1440 m a.s.l.; 68°20′N, 18°30′E) was chosen as a representative drainage basin of the arctic-oceanic mountain area in northernmost Swedish Lapland. Atmospheric solute inputs, chemical denudation, and mechanical fluvial denudation were analyzed. During the arctic summer field seasons of 2000, 2001, and 2002 measurements of daily precipitation, solute concentrations in precipitation, and in melted snow cores, taken before snowmelt, were recorded. In addition, solute and suspended sediment concentrations in creeks were analyzed, and bedload tracer movements were registered during the entire summer seasons (end of May until beginning of September). Results show a mean annual chemical denudation net rate of 5.4 t km−2 yr−1 in the entire catchment. Chemical denudation in Latnjavagge i...

  • direct human impacts on mechanical denudation in an arctic oceanic Periglacial Environment in northern swedish lapland abisko mountain area
    54th German Conference of Geographer Bern GERMANY SEP 28-OCT 04 2003, 2005
    Co-Authors: Achim A Beylich, Karin Lindblad, Ulf Molau
    Abstract:

    In the Latnjavagge drainage basin (9 km(2); 950 m - 1440 m a.s.l.; 68 degrees 20’N, 18 degrees 30’E), an arctic-oceanic Periglacial Environment in the mountain area of northernmost Swedish Lapland, ...