Development and recent activity of the San Andrés landslide on El Hierro, Canary Islands, Spain

Extremely voluminous landslides with a long run-out (also known as megalandslides) on oceanic volcanic islands are infrequent denudational processes on such islands. At the same time, they represent a major geological hazard that must be looked into to avoid negative consequences for the inhabitants of these islands. Their occurrence can be related to periods of intense seismo-volcanic activity, similar to that which occurred on El Hierro Island over 2011-2012. Landslides on volcanic islands are studied using onshore and offshore geological, geophysical and geomorphological records, considering their unique triggering conditions (e.g. lava intrusions, eruptive vents, magma chamber collapses). Previous work has pointed out similarities between specific cases of landslides on volcanic islands and deep-seated gravitational slope deformations (DSGSDs) which are typical in high mountain settings. Nevertheless, the methodological approaches and concepts used to investigate DSGSDs are not commonly applied on volcanic islands studies, even though their use may provide new information about the development stage, recent movements and future hazards. Therefore, this approach for studying the San Andrés landslide (SAL) on El Hierro (Canary Islands) has been developed applying a detailed morphological field mapping, an interpretation of digital elevation models, structural measurements, kinematic testing, and a precise movement monitoring system. The acquired information revealed a strong structural influence on the landslide morphology and the presence of sets of weakened planes acting as the sliding surfaces of the SAL or secondary landslides within its body. The presence of secondary landslides, deep erosive gullies, coastal cliffs and high on-shore relative relief also suggests a high susceptibility to future landslide movement. Direct monitoring on the landslide scarps and the slip plane, performed between February 2013 and July 2014, using an automated optical-mechanical crack gauge with a precision of up to 10-2 mm, detected creep movement in the order of 1 mm yr-1 with a persistent sinistral component as well as episodic horizontal and a subtle vertical movement. This monitoring will continue in the future in order to verify the initial observations, which instead of long-term movement patterns, could represent a landslide response to the period of an intense seismo-volcanic activity during 2011-12.The authors would like to thank the National Geographic Society/Waitt Grants Program (No. W244-12) and CzechGeo/EPOS (Project No. LM2010008) for the financial support of the research. We also thank the Spanish National Geographical Institute and the El Hierro Island Authority whose personnel provided us with useful support during the field installation of the measuring instruments. This work was carried out thanks to the unconditional support of the long-term conceptual development research organisation RVO: 67985891.Peer reviewe

Review article: methods of fractal geometry used in the study of complex geomorphic networks

Fractal geometry methods allow one to quantitatively describe self-similar or self-affined landscape shapes and facilitate the complex/holistic study of natural objects in various scales. They also allow one to compare the values of analyses from different scales (Mandelbrot 1967; Burrough 1981). With respect to the hierarchical scale (Bendix 1994) and fractal self-similarity (Mandelbrot 1982; Stuwe 2007) of the fractal landscape shapes, suitable morphometric characteristics have to be used, and a suitable scale has to be selected, in order to evaluate them in a representative and objective manner. This review article defines and compares: 1) the basic terms in fractal geometry, i.e. fractal dimension, self-similar, self-affined and random fractals, hierarchical scale, fractal self-similarity and the physical limits of a system; 2) selected methods of determining the fractal dimension of complex geomorphic networks. From the fractal landscape shapes forming complex networks, emphasis is placed on drainage patterns and valley networks

Bezpečnostní hlediska při používání kyslíku ve zdravotnictví

Import 20/04/2006Prezenční výpůjčkaVŠB - Technická univerzita Ostrava. Fakulta bezpečnostního inženýrství. Katedra (040) bezpečnostního management

Morphometric characteristics of valley nets in the Blue Nile basin in the Ethiopian highlands

The Blue Nile basin has diverse geological history, eg. repeated sea transgression and regression, Tertiary and Quaternary vulcanism, extensional faults in rift system, or area uplift (in the last 29 million years), which caused cutting of the rivers to their subsoil and creating deep gorges (Kazmin, 1975; Pik et al., 2003; Beyne, Abdelsalam, 2005, 2006; Gani et al., 2007; Gani et al., 2009; Wolela, 2010). This paper deals with classification and morphometric features of the Blue Nile valley nets in the Ethiopian highlands. Dendritic and trellis valley nets predominated in the Blue Nile basin. Trellis and rectangular valley nets predominated in the eastern part of the studied area, i.e. the upper part of the drainage area, and dendritic valley nets predominated in the western part of the studied area, i.e. the lower part of the drainage area. Parallel valley nets were located on the border of the studied area, i.e. the watershed or on the slopes of Cenozoic shield volcanoes. Annular valley nets did not occur in the Blue Nile basin. Valley nets were characterized by specific topologic and geometric features: 1) the Gravelius order system; 2) the bifurcation ratio of various order valleys, 3) the average length of various order valleys, 4) the average length-order ratio of various order valleys, 5)..

Morphology of valley networks

This bachelor thesis is engaged in the juxtaposition and different methods account of valley networks. Thanks to the background research of the late published literature, there are known a lot of types of valley network, which result in various types of relief and the criteria by which can the different types of valley networks be identified and distinguished from other types of valley networks. Methods of characterizing the valley networks are used to describe the valley of the same type of networks in different areas, respectively allow their comparison. In the interested area of CHKO Kokořínsko, there were studied the valley network order, the type of the valley network, the bifurcation ratio, connected of valley network, the fractal dimension, the valley network homogenity and the allometry of the valley of some parts. Valley networks in the studied areas of Pšovka and Liběchovka were identified as trellis and valley network of studied area of Vlhošt was described as a radial type of valley network with elements of annular valley network

Morphology of valley networks

This bachelor thesis is engaged in the juxtaposition and different methods account of valley networks. Thanks to the background research of the late published literature, there are known a lot of types of valley network, which result in various types of relief and the criteria by which can the different types of valley networks be identified and distinguished from other types of valley networks. Methods of characterizing the valley networks are used to describe the valley of the same type of networks in different areas, respectively allow their comparison. In the interested area of CHKO Kokořínsko, there were studied the valley network order, the type of the valley network, the bifurcation ratio, connected of valley network, the fractal dimension, the valley network homogenity and the allometry of the valley of some parts. Valley networks in the studied areas of Pšovka and Liběchovka were identified as trellis and valley network of studied area of Vlhošt was described as a radial type of valley network with elements of annular valley network

Morphostructural analysis of Ethiopian Highland based on remote sensing

- Morphostructural analysis of Ethiopian Highland based on remote sensing The morphometric analysis of lineaments, valleys and signs of erosion taken from a digital elevation model (DEM) made it possible to not only confirm most of the conclusions of the morphotectonic development of the area from the previously published results of structural, petrological, tectonic and geochronological analyses from the Ethiopian Highlands, but to also to expand our knowledge by applying several new hypotheses. Faults, lineaments and valleys are predominantly oriented in a direction compatible to the published concepts of the tectonic development of the area. Overall, the most abundant NE-SW and NNE-SSW lines reflect a change of extension from a NW-SE to WNW-ESE direction during the Pliocene (~40ř rotation), in relation to the creation and development of the Main Ethiopian Rift. The most pronounced morphological manifestations of the extension of the MER and western Afar during the Quaternary are confined to the borders of the MER, and the maximum SOLR values indicate a very short-lived effect of the stress field on the development of the landscape. The directions of the Pre-Neogene rift structures to the NW-SE and WNW-ESE are compatible with the oldest elements of the current landscape, i.e. the most developed..

Review article :methods of fractal geometry used in the study of complex geomorphic networks

Fractal geometry methods allow one to quantitatively describe self-similar or self-affined landscape shapes and facilitate the complex/ holistic study of natural objects in various scales. They also allow one to compare the values of analyses from different scales (Mandelbrot 1967; Burrough 1981). With respect to the hierarchical scale (Bendix 1994) and fractal self-similarity (Mandelbrot 1982; Stuwe 2007) of the fractal landscape shapes, suitable morphometric characteristics have to be used, and a suitable scale has to be selected, in order to evaluate them in a representative and objective manner. This review article defines and compares: 1) the basic terms in fractal geometry, i.e. fractal dimension, self-similar, self-affined and random fractals, hierarchical scale, fractal self-similarity and the physical limits of a system; 2) selected methods of determining the fractal dimension of complex geomorphic networks. From the fractal landscape shapes forming complex networks, emphasis is placed on drainage patterns and valley networks.If the drainage patterns or valley networks are self-similar fractals at various scales, it is possible to determine the fractal dimension by using the method “fractal dimension of drainage patterns and valley networks according to Turcotte (1997)”. Conversely, if the river and valley networks are self-affined fractals, it is appropriate to determine fractal dimension by methods that use regular grids. When applying a regular grid method to determine the fractal dimension on valley schematic networks according to Howard (1967), it was found that the “fractal dimension of drainage patterns and valley networks according to Mandelbrot (1982)”, the “box-counting dimension according to Turcotte (2007a)” and the “capacity dimension according to Tichý (2012)” methods show values in the open interval (1, 2). In contrast, the value of the “box-counting dimensions according to Rodríguez-Iturbe & Rinaldo (2001) / Kolmogorov dimensions according to Zelinka & Včelař & Čandík (2006)” was greater than 2. Therefore, to achieve values in the open interval (1, 2) more steps are needed to be taken than in the case of other fractal dimensions.9911

Morphometric characteristics of valley nets in the Blue Nile basin in the Ethiopian highlands

The Blue Nile basin has diverse geological history, eg. repeated sea transgression and regression, Tertiary and Quaternary vulcanism, extensional faults in rift system, or area uplift (in the last 29 million years), which caused cutting of the rivers to their subsoil and creating deep gorges (Kazmin, 1975; Pik et al., 2003; Beyne, Abdelsalam, 2005, 2006; Gani et al., 2007; Gani et al., 2009; Wolela, 2010). This paper deals with classification and morphometric features of the Blue Nile valley nets in the Ethiopian highlands. Dendritic and trellis valley nets predominated in the Blue Nile basin. Trellis and rectangular valley nets predominated in the eastern part of the studied area, i.e. the upper part of the drainage area, and dendritic valley nets predominated in the western part of the studied area, i.e. the lower part of the drainage area. Parallel valley nets were located on the border of the studied area, i.e. the watershed or on the slopes of Cenozoic shield volcanoes. Annular valley nets did not occur in the Blue Nile basin. Valley nets were characterized by specific topologic and geometric features: 1) the Gravelius order system; 2) the bifurcation ratio of various order valleys, 3) the average length of various order valleys, 4) the average length-order ratio of various order valleys, 5)..

Morphostructural analysis of Ethiopian Highland based on remote sensing

- Morfostrukturní analýza Etiopské vysočiny pomocí dálkového průzkumu Země Soubor morfometrických analýz údolních sítí, lineamentů a zlomů získaných z digitálního modelu reliéfu (DEM) umožnil nejen potvrdit většinu závěrů o morfotektonickém vývoji Etiopské vysočiny z dosavad publikovaných výsledků stratigrafických, strukturně-geologických, petrologických, tektonických a geochronologických studií realizovaných v Etiopské vysočině, ale umožnil jejich rozšíření o nové poznatky. Údolní segmenty i lineamenty jsou orientované ve směrech odpovídajících orientaci zlomů a odpovídajících publikovaným konceptům tektonického vývoje území. Nejvíce zastoupené jsou lineární prvky reliéfu odrážející pliocenní změnu tektonického napětí ze směru SV-JZ do SSV-JJZ směru (rotace napěťového pole o ~40ř) související se vznikem a vývojem Hlavního Etiopského Riftu (HER). Nejvýraznější morfologické projevy rozšiřování HER a Afarské deprese jsou dobře patrné na hranici Etiopské vysočiny a HER, kde dominance toků prvního řádu poukazuje na krátké působení napětí v tomto směru a aktivní zpětnou erozi. Paleogenní SZ-JV a ZSZ-VJV směry tektonického napětí tvoří nejstarší části Etiopské vysočiny, tj. nejvyvinutější údolí vysokých řádů (nejnižší hodnoty SOLR) a relikty radiální paleo-údolní sítě. Ta byla před pozdním miocénem...- Morphostructural analysis of Ethiopian Highland based on remote sensing The morphometric analysis of lineaments, valleys and signs of erosion taken from a digital elevation model (DEM) made it possible to not only confirm most of the conclusions of the morphotectonic development of the area from the previously published results of structural, petrological, tectonic and geochronological analyses from the Ethiopian Highlands, but to also to expand our knowledge by applying several new hypotheses. Faults, lineaments and valleys are predominantly oriented in a direction compatible to the published concepts of the tectonic development of the area. Overall, the most abundant NE-SW and NNE-SSW lines reflect a change of extension from a NW-SE to WNW-ESE direction during the Pliocene (~40ř rotation), in relation to the creation and development of the Main Ethiopian Rift. The most pronounced morphological manifestations of the extension of the MER and western Afar during the Quaternary are confined to the borders of the MER, and the maximum SOLR values indicate a very short-lived effect of the stress field on the development of the landscape. The directions of the Pre-Neogene rift structures to the NW-SE and WNW-ESE are compatible with the oldest elements of the current landscape, i.e. the most developed...Katedra fyzické geografie a geoekologieDepartment of Physical Geography and GeoecologyPřírodovědecká fakultaFaculty of Scienc