Preferencje help
Widoczny [Schowaj] Abstrakt
Liczba wyników

Znaleziono wyników: 7

Liczba wyników na stronie
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników

Wyniki wyszukiwania

help Sortuj według:

help Ogranicz wyniki do:
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
The aim of the paper was to identify the main factors affecting contemporary relief-forming processes in Greece. The analysis focused on areas with a varied type of relief. These were: high mountains, mountains of intermediate and low relief as well as valley and basin bottoms. The orographic diversity of Greece is the consequence of internal processes associated with the Alpine orogenesis and the neotectonic rejuvenation of relief. Lithology is considered to be of much lesser importance as its impact was mainly local. Contemporary morphogenetic processes in Greece are also conditioned by morphometric and lithological factors. In addition to that, many centuries of anthropopressure significantly affect the shaping of relief in this area. Locally, it is more significant than climatic influence.
2
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

Geneza i ewolucja obniżenia szottu Dżerid

100%
The article describes genesis and evolution of a tectonic depression in which there is the largest seasonal lake of Tunisia - the Chott Jerid. Gelogical setting of the depression and its morphometry was described with respect to geology of the whole country. The region is characterised by strike-slip faults running NW-SE, therefore the depression is of the "pull-a part" structure type. The structure began forming in upper Carbon, later it was filled with Permian and Mesozoic sediments which were folded in Neogene. At the end of Pliocene and during Pleistocene the region was probably covered by sea two times, however the second sea transgression (Tyrrhenian II) is questioned by several researchers. Evolution of the depression has been associated with many local tectonic movements which are thought to be at least 0.01 mm/yr (based on thickness of Miocene and Pliocene sediments), and later (Pleistocene and Holocene) even up to 0,26 mm/yr. Denudation rate during the whole post-orogenesis period must have been relatively high due to the arid or semi-arid climate, which favoured intensive surface wash.
The aim of this paper is to present results of the research on contemporary morphogenetic processes and landforms on an extemal waste dump of the Bełchatów Lignite Mine. The most important aspect of the research was the detennination of human impact on this transformation. The recultivation of the Bełchatów waste dump has been almost finished (except of a gypsum storage yard) and now the hill is forested. It is known as Mount Kamieńsk and is used for recreation such as skiing and biking. The research was based on geomorphological mapping. Field study was conducted in five periods, between July 2008 and September 2009. The authors showed that the linear water erosion is the main morphogenetic process acting on unpaved roads and paths - biking routes of Mount Kamieńsk. Particularly damaged, both by water erosion and by erosion caused by vehicles, are the roads on sandy ground. Information about the rate of erosion processes on roads was obtained on the basis of measurements along three selected road cross-profi les located on sandy road fragments (fig. 6). In the whole research period these roads were deepened by 0.2-0.4 m on average (fig. 7, 8, 9). On the roads localized on other grounds (not sandy) erosion caused directly by off-road vehicles was the most significant. Signs of erosion (natural and caused by vehicles) were registered on roads located on slopes as well as on flat areas. The gypsum storage yard is subject to intensive rill and gully erosion. This process was assessed indirectly be measuring accumulation rate on two small alluvial fans. The accumulation in four months period with some intense rainfall episodes was determined to be 0.07-0.125 m. The external waste dump of the Bełchatów Lignite Mine is a good example of successful recultivation of transformed landscape. Nowadays, linear erosion occurs on a very limited area, mainly in the gypsum storage yard and on roads. Erosion control devices are present only on a few road sectors. In authors' opinion the best way to preserve the "Mount Kamieńsk" roads is to cover their surface by crushed stone. It is also recommended to continue the monitoring of processes which transform the most damaged fragments of the waste dump.
Main aims of the research were: i) to assess the degree of development of fluvial landforms on Aegean Islands and ii) to determine the influence of fluvial processes on modification of islands relief. Field studies were conducted on the Ikaria Island, with highly diversified geology and relief, typical of mountainous islands of the Aegean Sea. The island is heavily dissected by deeply incised valleys and gorges with very steep slopes. The valleys on Ikaria Island vary in size, direction, geological setting and maturity. In the four small catchments located in the northern part of the Ikaria Island four types of valleys (from 1st to 4th order, according to Strahler) were studies in detail. Uppermost parts of these valleys (1st order valleys) have slightly concave cross-sections covered with regolith without developed channels. Such forms gradually evolve into 2nd order valleys with seasonal river channels, and further downstream, into well developed deep river valleys. Ravines with channels incised into solid rock are characteristic of the 3rd order valleys. The 4th order valleys are well developed, deeply incised gorges with wide channels sometimes accompanied by river terraces. Channels of small streams, rivers and field tracks in the mountains are subject to differentiated modelling by running water. In islands of the Aegean Sea, intensity of this modelling is diversified and rather small. It depends mostly on rainfall intensity, bedrock resistance to erosion, slope inclination and aspect. Catastrophic hydrometeorological events such as one which occurred in Ikaria in October, 2010, are responsible for rapid modification of whole valley floors and modification of river channels at lower river runs, within deltas and alluvial fans.
The main aim of the study was to estimate the influence of relief, lithology, climatic conditions, methods of wall construction and actual agricultural practice on the degradation of traditional agricultural terraces on the example of three Greek islands. We selected 7 research plots situated in 5 different geological settings - 3 on the Ikaria island, 2 on Thira, and 2 near Plati village on the SW edge of Lassithi Plateau on the Crete island. We used the following methods: GPS RTK measurements, mapping of erosion features, georadar profliling, infiltration rate measurements and interviews with farmers. We find that lithology is the most important factor controlling terraces degradation, but only in relation to methods of cultivation. Traditional agricultural practice helps terraces to remain stable, because cultivated field increases the possibility of infiltration and limits surface runoff. Heavy rainfalls do not affecting terraces stability due to high ground infiltration rate or high permeability of dry-stone walls. Terraces are more stable if they are concordant to the natural slope profile. On the terraced slope erosion is lower than on non-terraced slope. This is true only on the slope with very limited vegetation cover.
7
Artykuł dostępny w postaci pełnego tekstu - kliknij by otworzyć plik
Content available

Ewolucja i dynamika rzeźby okolic Pińczowa

45%
The major relief features of the Pińczów region (Ponidzie Pińczowskie) are the following: 1. Polygenetic nature of landforms, which are records of subsequent stages of the region’s geological development (both the youngest and the oldest landforms owe their contemporary shape not to one, but to many links in the evolution of the analysed relief). 2. Great importance of pre-Quaternary forms excavated from under younger deposits. ln this respect, Tertiary relief is the most significant. 3. Manifest dependence of morphology on tectonics and lithological differentiation of deposits (tectonics-based direction of relief, dependence of slope shapes from the substratum structure, occurrence of structural escarpments). 4. Presence and common occurrence of unique gypsum karst forms and their great diversity. 5. lnsignificance of glacial forms, whose remains can be found only locally, on hilltops of older elevations. 6. Considerable range of fluvoglacial cover. 7. Major significance of Holocene processes for the contemporary relief. 8. Important contemporary role of man in relief-forming processes, multitude and diversity of antropogenic forms. The graphic representation of relief (Fig. 2) manifests yet another important feature of the relief in the Pińczów region; it distinctly shows its division into horizons, relating to pre-Quaternary forms. Starting from the areas situated the highest, we can distinguish: • hilltop surface of the Pińczów Hummock at a level of approximately 260 metres a.s.l., with denudation mountains, partly covered with fluvioglacial sands, occasionally forming sand dunes. Culminations reach 270-290 metres above sea level. • Another level (230-250 metres a.s.l.) cuts through gypsum, limestone and marl of the Solec and Połaniec Basins. It is largely covered with denudated glacial forms and fluvioglacial sands. Above this level, gypsum and glacial relic mountains protrude. • In the western part of the Nida valley, the loess-covered spreads of the Wodzisław Hummock hilltop, occurring at the altitude of 280-330 metres, and lowering to approximately 250 metres on the slopes, correspond to the two surfaces described above. • At an altitude of approximately 230 metres starts the level of large, usually water-logged depressions, contemporarily used by rivers or intersected by a network of canals. Most probably, they are preQuaternary forms, possibly tectonic, transformed by glacial (and in some places karst) processes. • The remaining levels are distinctly related to the Nida valley and constitute its terraces -two Pleistocene and two Holocene, at altitudes ranging from 200 to 180 metres. The first three Ievels are autonomous in nature, with clearly marked slopes. The remaining levels are local erosion base levels and receive matter originating from the erosion of higher-situated areas.
Pierwsza strona wyników Pięć stron wyników wstecz Poprzednia strona wyników Strona / 1 Następna strona wyników Pięć stron wyników wprzód Ostatnia strona wyników
JavaScript jest wyłączony w Twojej przeglądarce internetowej. Włącz go, a następnie odśwież stronę, aby móc w pełni z niej korzystać.