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Morphology of thermal-contraction-crack features and their pattern
Dufek, Jaroslav ; Křížek, Marek (advisor) ; Roman, Matěj (referee)
This bachelor thesis deals with phenomenon of periglacial landscape of continuos permafrost such as thermal-conctraction-crack polygons and forms of their secondary infill - ice, sand, soil and composite-wedge pseudomorphs. Upper Pleistocene thermal-conctraction-crack polygons are located in mid-latitudes all across the Europe. Most common geometry shapes of these polygons are orthogonal and hexagonal patterns. Pseudomorphs are commonly situated in areas of lowlands, river terraces, floodplains on slopes with angle up to 4ř. Their distribution is closely associated with the maximum extent of past permafrost during the last glacial episode (~17-25 ka BP). This pleistocene phase is known as last periglacial maximum (LPM; Vandenberghe et al. 2014). Creation of ice-wedges is primarily bound to present continuous permafrost, which the southernmost Pleistocene limit in Europe has been established to 47ř N (Black 1976, Vandenberghe et al. 2014). However, some research suggest, that with favorable local conditions, ice-wedges can develop also in arid climate and discontinuous permafrost zone and they can occur together with sand-wedges (Kasse 1998). It was also found that cold arid climate is not the only factor for sand wedge development, but great importance has also local variability of microrelief such...
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