Rock glaciers are lobate or tongue-shaped assemblages of poorly sorted, angular-rock debris and ice, commonly found in high mountain environments, which move as a consequence of the deformation of internal ice (Giardino and Vitek, 1988; Barsch, 1996). However, in most research works, when discussing the formation of these features, the focus has been mainly on the past or present climatic conditions. The systematic observations of the distribution of relict rock glaciers in the mountains of the Balkan Peninsula indicate however that geological setting, represented by bedrock type and composition, and the pattern of fault lines, is not less important for the formation and evolution of these landforms. The present article is focused on rock glaciers in the high mountain zone of the Pirin Mounains (Bulgaria), which are formed in mixed lithology, with participation of both silicate rocks (granite, gneiss) and carbonate rocks (marble). In fact, these rock glaciers are the only ones of a typical morphology that exist in the glaciokarstic marble area of Northern Pirin. What is common for all locations where such rock glaciers are found is that the marble layer, which is on top, is quite thin (few metres to few hundreds of metres). In such conditions, the rock glacier formation occurred following the mechanism typical for silicate rocks, but using marble debris and block material instead. The observed forms are characteristic only for marginal zones, along the contact line between silicate and carbonate high mountain environments.
{"title":"Rock glaciers in mixed lithologies: a case study from Northern Pirin","authors":"E. Gachev","doi":"10.21094/rg.2020.098","DOIUrl":"https://doi.org/10.21094/rg.2020.098","url":null,"abstract":"Rock glaciers are lobate or tongue-shaped assemblages of poorly sorted, angular-rock debris and ice, commonly found in high mountain environments, which move as a consequence of the deformation of internal ice (Giardino and Vitek, 1988; Barsch, 1996). However, in most research works, when discussing the formation of these features, the focus has been mainly on the past or present climatic conditions. The systematic observations of the distribution of relict rock glaciers in the mountains of the Balkan Peninsula indicate however that geological setting, represented by bedrock type and composition, and the pattern of fault lines, is not less important for the formation and evolution of these landforms. The present article is focused on rock glaciers in the high mountain zone of the Pirin Mounains (Bulgaria), which are formed in mixed lithology, with participation of both silicate rocks (granite, gneiss) and carbonate rocks (marble). In fact, these rock glaciers are the only ones of a typical morphology that exist in the glaciokarstic marble area of Northern Pirin. What is common for all locations where such rock glaciers are found is that the marble layer, which is on top, is quite thin (few metres to few hundreds of metres). In such conditions, the rock glacier formation occurred following the mechanism typical for silicate rocks, but using marble debris and block material instead. The observed forms are characteristic only for marginal zones, along the contact line between silicate and carbonate high mountain environments. ","PeriodicalId":52661,"journal":{"name":"Revista de Geomorfologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-22","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43817279","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Snow avalanches are a common phenomenon in Parâng Mountains (Southern Carpathians, Romania) perturbing tourism activities and associated infrastructures, damaging forests, and causing fatalities. Its past history is an essential information to gather while assessing the hazard zonation areas. Usually, in Romania snow–avalanche activity occurring in forested areas are neither monitored, nor recorded by historical archives. In these areas, environmental archives such as tree rings may provide useful information about the past avalanche activity. The purpose of the present study is to reconstruct snow–avalanche history with tree rings along a path located below Cârja Peak (2405 m a.s.l.), an area where past snow–avalanche activity still remains underestimated. In this sense, 57 Norway spruce (Picea abies (L.) Karst.) trees showing clear signs of disturbance by snow avalanches were sampled and the growth anomalies associated with the mechanical impact produced by snow avalanches on trees were identified within their rings and served to reconstruct past events. The reconstructed chronology covers the period 1994–2018 showing the occurrence of a minimum of 11 major events, with an average return period of 2.1 years. Tree–ring records provided the most consistent avalanche event chronology in the study area. Although the limited extension of the chronology back in time, a better understanding of snow–avalanche history which may be gained through dendrochronological reconstructions represent nonetheless useful and pertinent information to consider before the implementation and development of infrastructure in this mountain avalanche–prone area.
{"title":"Snow–avalanche history reconstructed with tree rings in Parâng Mountains (Southern Carpathians, Romania)","authors":"C. Todea, O. Pop, D. Germain","doi":"10.21094/rg.2020.099","DOIUrl":"https://doi.org/10.21094/rg.2020.099","url":null,"abstract":"Snow avalanches are a common phenomenon in Parâng Mountains (Southern Carpathians, Romania) perturbing tourism activities and associated infrastructures, damaging forests, and causing fatalities. Its past history is an essential information to gather while assessing the hazard zonation areas. Usually, in Romania snow–avalanche activity occurring in forested areas are neither monitored, nor recorded by historical archives. In these areas, environmental archives such as tree rings may provide useful information about the past avalanche activity. The purpose of the present study is to reconstruct snow–avalanche history with tree rings along a path located below Cârja Peak (2405 m a.s.l.), an area where past snow–avalanche activity still remains underestimated. In this sense, 57 Norway spruce (Picea abies (L.) Karst.) trees showing clear signs of disturbance by snow avalanches were sampled and the growth anomalies associated with the mechanical impact produced by snow avalanches on trees were identified within their rings and served to reconstruct past events. The reconstructed chronology covers the period 1994–2018 showing the occurrence of a minimum of 11 major events, with an average return period of 2.1 years. Tree–ring records provided the most consistent avalanche event chronology in the study area. Although the limited extension of the chronology back in time, a better understanding of snow–avalanche history which may be gained through dendrochronological reconstructions represent nonetheless useful and pertinent information to consider before the implementation and development of infrastructure in this mountain avalanche–prone area.","PeriodicalId":52661,"journal":{"name":"Revista de Geomorfologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-17","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"49088311","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The paper discusses geomorphology of the Sunda Trench, an oceanic trench located in eastern Indian Ocean along the Sumatra and Java Islands of the Indonesian archipelago. In particular, it analysis the difference in depths and variation in slope steepness between the two segments of the trench: the southern Java transect (coordinates 108.8°E 10.10°S to 113.0°E 10.75°S) and the northern Sumatra transect (97.5°E 1.1°S to 101.0°E 5.5°S). The thematic maps and geomorphological modelling were plotted using Generic Mapping Tools (GMT). The materials include high-resolution data on topography, geology and geophysics: GEBCO 15 arc-minute resolution grid, EGM2008 2.5 minute Earth Gravitation Model of 2008, GlobSed global 5‐arc‐minute total sediment thickness and vector geological datasets. In addition to the GEBCO-based bathymetric data, geological, topographic and geophysical maps, the results include enlarged transects for the Java and Sumatra segments, their slope gradients and cross-section profiles, derived from the bathymetric GEBCO dataset. The geomorphology framework of the Sunda Trench is largely controlled by the subduction of the Australian plate underneath the Sunda microplate. The geological processes take place in basin of the Indian Ocean at different stages of its evolution and influence the nature of the submarine geomorphology and geometric shape of the trench. Sunda Trench is seismically active part of the Pacific Ring of Fire. A large number of the catastrophic earthquakes are recorded around the trench. The histograms shows variation in depths along the segments of the Sumatra and Java. The Java segment has a bell-shaped data distribution in contrast to the Sumatra with bimodal pattern. The Java segment has the most repetitive depths at -2,500 to -5,200 m. The Sumatra transect has two peaks: 1) a classic bell-shaped peak at depths -4,500 m to -5,500 m; 2) shelf area with a peak from 0 to -1,750 m. The data at middle depths (-1,750 to -4,500 m) have a frequency <300 samples. The most frequent bathymetry for the Sumatra segment corresponds to the -4,750 m to -5,000 m (2,151 samples). Comparing to the Sumatra segment, the Java segment is deeper. For the depths >-6,000 m, there are only 138 samples for the Sumatra while 547 samples for Java. Furthermore, Java segment has more symmetrical geometric shape while Sumatra segment is asymmetric, one-sided. The Sumatra segment has a steepness of 57.86° on its eastern side (facing Sumatra Island) and a contrasting 14.58° on the western part. The Java segment has a steepness of 64.34° on its northern side (facing Java Island) and 24.95° on the southern part (facing Indian Ocean). The paper contributes to the studies of the submarine geomorphology in Indonesia.
{"title":"Analysis of the difference in depths and variation in slope steepness of the Sunda Trench, Indonesia, east Indian Ocean","authors":"Polina Lemenkova","doi":"10.21094/rg.2020.096","DOIUrl":"https://doi.org/10.21094/rg.2020.096","url":null,"abstract":"The paper discusses geomorphology of the Sunda Trench, an oceanic trench located in eastern Indian Ocean along the Sumatra and Java Islands of the Indonesian archipelago. In particular, it analysis the difference in depths and variation in slope steepness between the two segments of the trench: the southern Java transect (coordinates 108.8°E 10.10°S to 113.0°E 10.75°S) and the northern Sumatra transect (97.5°E 1.1°S to 101.0°E 5.5°S). The thematic maps and geomorphological modelling were plotted using Generic Mapping Tools (GMT). The materials include high-resolution data on topography, geology and geophysics: GEBCO 15 arc-minute resolution grid, EGM2008 2.5 minute Earth Gravitation Model of 2008, GlobSed global 5‐arc‐minute total sediment thickness and vector geological datasets. In addition to the GEBCO-based bathymetric data, geological, topographic and geophysical maps, the results include enlarged transects for the Java and Sumatra segments, their slope gradients and cross-section profiles, derived from the bathymetric GEBCO dataset. The geomorphology framework of the Sunda Trench is largely controlled by the subduction of the Australian plate underneath the Sunda microplate. The geological processes take place in basin of the Indian Ocean at different stages of its evolution and influence the nature of the submarine geomorphology and geometric shape of the trench. Sunda Trench is seismically active part of the Pacific Ring of Fire. A large number of the catastrophic earthquakes are recorded around the trench. The histograms shows variation in depths along the segments of the Sumatra and Java. The Java segment has a bell-shaped data distribution in contrast to the Sumatra with bimodal pattern. The Java segment has the most repetitive depths at -2,500 to -5,200 m. The Sumatra transect has two peaks: 1) a classic bell-shaped peak at depths -4,500 m to -5,500 m; 2) shelf area with a peak from 0 to -1,750 m. The data at middle depths (-1,750 to -4,500 m) have a frequency <300 samples. The most frequent bathymetry for the Sumatra segment corresponds to the -4,750 m to -5,000 m (2,151 samples). Comparing to the Sumatra segment, the Java segment is deeper. For the depths >-6,000 m, there are only 138 samples for the Sumatra while 547 samples for Java. Furthermore, Java segment has more symmetrical geometric shape while Sumatra segment is asymmetric, one-sided. The Sumatra segment has a steepness of 57.86° on its eastern side (facing Sumatra Island) and a contrasting 14.58° on the western part. The Java segment has a steepness of 64.34° on its northern side (facing Java Island) and 24.95° on the southern part (facing Indian Ocean). The paper contributes to the studies of the submarine geomorphology in Indonesia.","PeriodicalId":52661,"journal":{"name":"Revista de Geomorfologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"67826953","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The biocrusts are organized by soil-surface communities of biota that live within or on the very top of soil surface and play an important role in soil conservation. They include lichens, mosses, fungi, cyanobacteria, eukaryotic algae, and other heterotrophic bacteria. The interaction between biocrusts and soil is very important and good awareness from that help to better manage soil specially in arid and semi-arid areas. The linkage between cyanobacteria species and soil physicochemical parameters and mineralogy in two geomorphic zones in the northeastern Iran was studied. Samples were collected in summer along a linear transect by using 50 x 50 cm quadrates for each study zone. Individual mineral soil particles were analyzed by a scanning electron microscopy (SEM). The amounts of Na, K, Ca, and Mg contents as well as EC and SOC altered significantly between two study zones. Biocrusts increased levels of organic carbon, pH, calcium carbonate, exchangeable sodium and potassium percentages. The main soil properties of SOC, CaCO3 and amount of clay changed among biocrust sand bare soils.
生物结皮是由生活在土壤表层或最表层的生物群落组成的，在土壤保持中起着重要作用。它们包括地衣、苔藓、真菌、蓝藻、真核藻类和其他异养细菌。生物结皮与土壤的相互作用是非常重要的，认识到这一点有助于更好地管理土壤，特别是在干旱和半干旱地区。研究了伊朗东北部两个地貌带蓝藻种类与土壤理化参数和矿物学的联系。夏季沿线性样带收集样本，每个研究区使用50 x 50厘米的方形。用扫描电子显微镜(SEM)对矿质土壤颗粒进行了分析。两个研究区的Na、K、Ca、Mg含量以及EC和SOC变化显著。生物结壳增加了有机碳、pH值、碳酸钙、可交换钠和钾的百分比。生物结砂裸地土壤的主要性质是有机碳、碳酸钙和粘质含量发生了变化。
{"title":"The effects of biocrusts on soil parameters in a semi-arid pediment at north-eastern Iran","authors":"A. Sepehr, Atoosa Gholamhosseinian, I. Emadodin","doi":"10.21094/rg.2020.094","DOIUrl":"https://doi.org/10.21094/rg.2020.094","url":null,"abstract":"The biocrusts are organized by soil-surface communities of biota that live within or on the very top of soil surface and play an important role in soil conservation. They include lichens, mosses, fungi, cyanobacteria, eukaryotic algae, and other heterotrophic bacteria. The interaction between biocrusts and soil is very important and good awareness from that help to better manage soil specially in arid and semi-arid areas. The linkage between cyanobacteria species and soil physicochemical parameters and mineralogy in two geomorphic zones in the northeastern Iran was studied. Samples were collected in summer along a linear transect by using 50 x 50 cm quadrates for each study zone. Individual mineral soil particles were analyzed by a scanning electron microscopy (SEM). The amounts of Na, K, Ca, and Mg contents as well as EC and SOC altered significantly between two study zones. Biocrusts increased levels of organic carbon, pH, calcium carbonate, exchangeable sodium and potassium percentages. The main soil properties of SOC, CaCO3 and amount of clay changed among biocrust sand bare soils.","PeriodicalId":52661,"journal":{"name":"Revista de Geomorfologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47034787","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
The last three decades have marked an unprecedented urban expansion of the city of Cluj-Napoca, leading to strong anthropogenic influences on the natural environment and important changes in the land-use. Due to the specific morphology of Cluj area, characterized by limited available plane surfaces which are insufficient to support the urban expansion, more and more territories with slopes between 5°-26° are used for constructions. These areas are marked by high risks of mass movements due to their specific geological and geomorphological characteristics, therefore the present study proposes a more detailed and complex GIS and remote sensing analysis of the western urban part of Cluj-Napoca, in order to highlight the main changes of the city and the consequences of the human actions. One of the most used radar interferometry (InSAR) technique was applied in order to detect land deformations that can threaten the infrastructure and the population. Sentinel-1B SAR imagery were processed by the DInSAR methodology, resulting in a land deformation map, which represents an important support in generating the vulnerability assessment. Based upon this evaluation, we concluded that the most vulnerable neighbourhoods to land deformations from the western part of the city are the peripheral ones, as following: Dâmbul Rotund, Bună Ziua, Europa, Mănăștur, West Iris and Făget, proving that human activity and the geological setting are the main triggering factors of the discussed phenomenon.
{"title":"Investigating land surface deformation using InSAR and GIS techniques in Cluj–Napoca city’s most affected sector by urban sprawl (Romania)","authors":"A. Kerekes, S. Poszet, Laurențiu Călin Baciu","doi":"10.21094/rg.2020.097","DOIUrl":"https://doi.org/10.21094/rg.2020.097","url":null,"abstract":"The last three decades have marked an unprecedented urban expansion of the city of Cluj-Napoca, leading to strong anthropogenic influences on the natural environment and important changes in the land-use. Due to the specific morphology of Cluj area, characterized by limited available plane surfaces which are insufficient to support the urban expansion, more and more territories with slopes between 5°-26° are used for constructions. These areas are marked by high risks of mass movements due to their specific geological and geomorphological characteristics, therefore the present study proposes a more detailed and complex GIS and remote sensing analysis of the western urban part of Cluj-Napoca, in order to highlight the main changes of the city and the consequences of the human actions. One of the most used radar interferometry (InSAR) technique was applied in order to detect land deformations that can threaten the infrastructure and the population. Sentinel-1B SAR imagery were processed by the DInSAR methodology, resulting in a land deformation map, which represents an important support in generating the vulnerability assessment. Based upon this evaluation, we concluded that the most vulnerable neighbourhoods to land deformations from the western part of the city are the peripheral ones, as following: Dâmbul Rotund, Bună Ziua, Europa, Mănăștur, West Iris and Făget, proving that human activity and the geological setting are the main triggering factors of the discussed phenomenon.","PeriodicalId":52661,"journal":{"name":"Revista de Geomorfologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2020-12-13","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43065151","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
S. Roșca, Ștefan Bilașco, I. Vescan, I. Fodorean, D. Petrea, R. Rusu
Multi–risk assessment supposes an integrated analysis of various processes and phenomena generating risks across the territory, highlighting the individual and cumulative impact at different levels of analysis. This paper aims at creating an assessment model of multi–risk generated by the cumulative effects of landslides and floods, processes considered as significant in the study area, the administrative unit of the city of Reghin in the Transylvanian Basin. To obtain the multi–risk, two GIS spatial analysis models have been created. The first model means to identify the probability of landslide occurrence (built on GIS databases in vector and raster format, correlatively analysed by means of spatial analysis functions and equations), and is adapted according to legislative regulations stipulated in the Government Decision no. 447/2003. The second one is a database regarding the floodable area with a 1% probability in raster format, resulted from a nation–wide model created to identify the flooded areas.The multi–risk map was created using the mediation method, in which every class of individual (geomorphological or hydrological) hazard receives equal weight within the final result. As a consequence of applying the above–mentioned models, we obtained areas with different probabilities for cumulative risk processes, which are rendered as favourable or restrictive in terms of locating different structures (roads, settlements, functional areas, shopping centres). According to the degree of validation, these may be used for a more precise determination of the development areas and for territorial planning.
{"title":"Multi–risk quantitative assessment in Reghin city, Transylvania, Romania","authors":"S. Roșca, Ștefan Bilașco, I. Vescan, I. Fodorean, D. Petrea, R. Rusu","doi":"10.21094/rg.2019.014","DOIUrl":"https://doi.org/10.21094/rg.2019.014","url":null,"abstract":"Multi–risk assessment supposes an integrated analysis of various processes and phenomena generating risks across the territory, highlighting the individual and cumulative impact at different levels of analysis. This paper aims at creating an assessment model of multi–risk generated by the cumulative effects of landslides and floods, processes considered as significant in the study area, the administrative unit of the city of Reghin in the Transylvanian Basin. To obtain the multi–risk, two GIS spatial analysis models have been created. The first model means to identify the probability of landslide occurrence (built on GIS databases in vector and raster format, correlatively analysed by means of spatial analysis functions and equations), and is adapted according to legislative regulations stipulated in the Government Decision no. 447/2003. The second one is a database regarding the floodable area with a 1% probability in raster format, resulted from a nation–wide model created to identify the flooded areas.The multi–risk map was created using the mediation method, in which every class of individual (geomorphological or hydrological) hazard receives equal weight within the final result. As a consequence of applying the above–mentioned models, we obtained areas with different probabilities for cumulative risk processes, which are rendered as favourable or restrictive in terms of locating different structures (roads, settlements, functional areas, shopping centres). According to the degree of validation, these may be used for a more precise determination of the development areas and for territorial planning.","PeriodicalId":52661,"journal":{"name":"Revista de Geomorfologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-26","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"47435904","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Mountain glaciation involves the erosion of cirques and troughs, which increase steep slopes but also produce gentle slopes in cirque floors and trough floors. This is expected to increase the variability of slope gradients at related altitudes. Taking a whole mountain range, its distributions of altitude and slope can be analysed to establish a signal of glacial modification. Frequency distributions of altitude (hypsometry) and gradient (clinometry) alone do not seem adequate. Taking these two variables together – hypsoclinometry, plotting slope gradient against altitude – is more promising. Frequency distributions of slope gradient at different altitudes are exemplified here for mountain ranges in British Columbia and Romania, together with altitudinal variations of steep or gentle slopes. Cirque headwalls give the clearest morphometric signature of glaciation. Steep (especially the steepest) slopes are concentrated at cirque altitudes, increasing mean, median, standard deviation (SD) and inter-quartile range (IQR) of gradients, especially above cirque floors. There is only a small increase in SD and IQR at cirque floor altitudes. Hypsometric maxima and increased proportions of gentle slopes at cirque floor altitudes are clear only in mountain ranges densely occupied by cirques. This relates to the small proportion of each cirque (about 28%) occupied by the floor. Concentrations of steep slope aspects in directions favoured by local glaciers provide further evidence of glacial modification. The most general morphometric effect of glaciation, however, is the increase in steep slopes at cirque headwall altitudes. Thus it is possible to rank mountain ranges by degree of glacial modification.
{"title":"The erosion of glaciated mountains: evidence from hypsoclinometry","authors":"I. Evans","doi":"10.21094/RG.2019.006","DOIUrl":"https://doi.org/10.21094/RG.2019.006","url":null,"abstract":"Mountain glaciation involves the erosion of cirques and troughs, which increase steep slopes but also produce gentle slopes in cirque floors and trough floors. This is expected to increase the variability of slope gradients at related altitudes. Taking a whole mountain range, its distributions of altitude and slope can be analysed to establish a signal of glacial modification. Frequency distributions of altitude (hypsometry) and gradient (clinometry) alone do not seem adequate. Taking these two variables together – hypsoclinometry, plotting slope gradient against altitude – is more promising. Frequency distributions of slope gradient at different altitudes are exemplified here for mountain ranges in British Columbia and Romania, together with altitudinal variations of steep or gentle slopes. Cirque headwalls give the clearest morphometric signature of glaciation. Steep (especially the steepest) slopes are concentrated at cirque altitudes, increasing mean, median, standard deviation (SD) and inter-quartile range (IQR) of gradients, especially above cirque floors. There is only a small increase in SD and IQR at cirque floor altitudes. Hypsometric maxima and increased proportions of gentle slopes at cirque floor altitudes are clear only in mountain ranges densely occupied by cirques. This relates to the small proportion of each cirque (about 28%) occupied by the floor. Concentrations of steep slope aspects in directions favoured by local glaciers provide further evidence of glacial modification. The most general morphometric effect of glaciation, however, is the increase in steep slopes at cirque headwall altitudes. Thus it is possible to rank mountain ranges by degree of glacial modification.","PeriodicalId":52661,"journal":{"name":"Revista de Geomorfologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2019-12-24","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"41705289","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
This paper focused on the analysis of the interpretation potential given by fluvial archives, in order to decipher the Mid- to Late Holocene sedimentary history. The database discussed here refers to 65 dated ages (mostly radiocarbon), mappings of the most representative floodplain reaches of Suceava, Moldova and Siret rivers, and 23 outcrops analysed in floodplain deposits (river banks or gravel pits). The study results concentrated on (a) describing the regional features of Eastern Carpathian floodplains, (b) the floodplain morphology and its correlation with the structure of fluvial deposits and (c) identifying the paleoevents of fluvial activity on a centennial timescale. In this way, we were able to identify a general pattern of the dynamic geomorphology history for the rivers situated eastward of the Carpathians, which resulted from combining the Mid- to Late Holocene sedimentation phases, the avulsion and lateral migration processes that occurred during high fluvial activity intervals and the morphological adjustment of the rivers channels, from braiding to wandering and sinuously–meandering. The chronological overlay of the events revealed that the time intervals with the most extensive fluvial processes on the rivers draining the Eastern Carpathians occurred (in years before present) during 6200, 5300, 4100–4080, 3600, 2300–2200 (Iron Age), 1300 (Migrations Period), 950–970 (Medieval Climate Anomaly), 750–520 BP (Little Ice Age)and that these intervals generally overlap the high precipitation palaeoclimatic episodes documented in Romania. The fluvial activity of the rivers during the Mid- to Late Holocene has been compared as well with several records of paleo–climates variability over the geographical area of Romania. The result showed that many flooding episodes were coincident with the wet and cold intervals which were also identified in the variation of the other proxydata, especially after 4.7 kcal BP.
{"title":"Mid and Late Holocene flooding reconstruction based on fluvial archives of the East Carpathian rivers","authors":"M. Rǎdoane, F. Chiriloaei, N. Rădoane, C. Nechita","doi":"10.21094/rg.2018.010","DOIUrl":"https://doi.org/10.21094/rg.2018.010","url":null,"abstract":"This paper focused on the analysis of the interpretation potential given by fluvial archives, in order to decipher the Mid- to Late Holocene sedimentary history. The database discussed here refers to 65 dated ages (mostly radiocarbon), mappings of the most representative floodplain reaches of Suceava, Moldova and Siret rivers, and 23 outcrops analysed in floodplain deposits (river banks or gravel pits). The study results concentrated on (a) describing the regional features of Eastern Carpathian floodplains, (b) the floodplain morphology and its correlation with the structure of fluvial deposits and (c) identifying the paleoevents of fluvial activity on a centennial timescale. In this way, we were able to identify a general pattern of the dynamic geomorphology history for the rivers situated eastward of the Carpathians, which resulted from combining the Mid- to Late Holocene sedimentation phases, the avulsion and lateral migration processes that occurred during high fluvial activity intervals and the morphological adjustment of the rivers channels, from braiding to wandering and sinuously–meandering. The chronological overlay of the events revealed that the time intervals with the most extensive fluvial processes on the rivers draining the Eastern Carpathians occurred (in years before present) during 6200, 5300, 4100–4080, 3600, 2300–2200 (Iron Age), 1300 (Migrations Period), 950–970 (Medieval Climate Anomaly), 750–520 BP (Little Ice Age)and that these intervals generally overlap the high precipitation palaeoclimatic episodes documented in Romania. The fluvial activity of the rivers during the Mid- to Late Holocene has been compared as well with several records of paleo–climates variability over the geographical area of Romania. The result showed that many flooding episodes were coincident with the wet and cold intervals which were also identified in the variation of the other proxydata, especially after 4.7 kcal BP.","PeriodicalId":52661,"journal":{"name":"Revista de Geomorfologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43820184","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
N. Evelpidou, T. Gournelos, Eirini Kardara, A. Karkani
This research applies the fuzzy set theory via Geographical Information Systems (GIS) – based analysis, in order to model slope erosion by runoff. For this purpose, the following steps were accomplished: definition of input variables (rocks’ susceptibility to erosion, slope inclination, slope morphology), development of a fuzzy inference system based on theoretical and empirical knowledge, transformation of input to output variables (erosion – deposition) and visualization of the output variables (spatial distribution of erosion–deposition processes). The method was applied on the drainage basin of Corinth, located in the north–eastern part of Peloponnese (Greece), where a series of catastrophic erosional events have recently occurred.
{"title":"Fuzzy modelling of slope erosion by runoff. Case study in Corinth basin, Greece","authors":"N. Evelpidou, T. Gournelos, Eirini Kardara, A. Karkani","doi":"10.21094/RG.2018.013","DOIUrl":"https://doi.org/10.21094/RG.2018.013","url":null,"abstract":"This research applies the fuzzy set theory via Geographical Information Systems (GIS) – based analysis, in order to model slope erosion by runoff. For this purpose, the following steps were accomplished: definition of input variables (rocks’ susceptibility to erosion, slope inclination, slope morphology), development of a fuzzy inference system based on theoretical and empirical knowledge, transformation of input to output variables (erosion – deposition) and visualization of the output variables (spatial distribution of erosion–deposition processes). The method was applied on the drainage basin of Corinth, located in the north–eastern part of Peloponnese (Greece), where a series of catastrophic erosional events have recently occurred.","PeriodicalId":52661,"journal":{"name":"Revista de Geomorfologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"42115999","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Glacio–isostatic rebound is one of the most important landscape processes affecting the northern and northeastern coast of Canada and, therefore, reconstruction of postglacial rebound rates is critical for a better understanding of landscape evolution in this region. Yet, studies reconstructing coastal palaeogeography in Northern Canadaare constrained by the limitation of shell–based radiocarbon chronologies used in dating shoreline displacementand palaeo–sea levels. This study proposes an alternative methodology for the reconstruction and dating of palaeo–sea levels, which uses testate amoeba microfossils from coastal sediments as palaeoecological markers of coastal water table shifts linked to sea level change. Our results indicate that testate amoeba–inferred water table reconstruction is a good indicator of water table drawdown due to isostatic uplift on affected coastlines. Furthermore, radiocarbon dating of distinct plant macrofossils within the transitional marine/freshwater stratigraphy avoids the inherent reservoir effect issues associated with dating of marine shells.
{"title":"Identifying glacio–isostatic rebound processes using testate amoeba as palaeohydrological proxies; a case study from subarctic Québec, Canada","authors":"C. Ferguson, Florin Pendea","doi":"10.21094/rg.2018.008","DOIUrl":"https://doi.org/10.21094/rg.2018.008","url":null,"abstract":"Glacio–isostatic rebound is one of the most important landscape processes affecting the northern and northeastern coast of Canada and, therefore, reconstruction of postglacial rebound rates is critical for a better understanding of landscape evolution in this region. Yet, studies reconstructing coastal palaeogeography in Northern Canadaare constrained by the limitation of shell–based radiocarbon chronologies used in dating shoreline displacementand palaeo–sea levels. This study proposes an alternative methodology for the reconstruction and dating of palaeo–sea levels, which uses testate amoeba microfossils from coastal sediments as palaeoecological markers of coastal water table shifts linked to sea level change. Our results indicate that testate amoeba–inferred water table reconstruction is a good indicator of water table drawdown due to isostatic uplift on affected coastlines. Furthermore, radiocarbon dating of distinct plant macrofossils within the transitional marine/freshwater stratigraphy avoids the inherent reservoir effect issues associated with dating of marine shells.","PeriodicalId":52661,"journal":{"name":"Revista de Geomorfologie","volume":null,"pages":null},"PeriodicalIF":0.0,"publicationDate":"2018-12-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"43899753","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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