Abstrakt
The influence of past microclimates on the morphology and distribution of clasts is considered for relict large-scale sorted polygons in the Krkonoše Mountains (Czech Republic). Sixty-two sorted polygons with an average length of 194 cm and an average height of 21.5 cm were measured at four sites on Mt.
Luční hora, at elevations of 1455 to 1555 m a.s.l. The polygons consist of tabular clasts with a mean length of 11 cm at the borders and 5 cm in the interiors.
Smaller polygons are better sorted because of shorter distances for clasts to reach their borders. Polygons with greater relative height are better sorted due to more intensive slope processes associated with differential frost heaving.
Better sorted and more domed polygons at higher altitudes suggest more severe and longer-lasting microclimates suitable for the development of sorted polygons. The altitudinal gradient in polygon morphology and sorting suggests the dominant role of microlimate in the periglacial environment of the summit area of the Krkonoše Mountains during the Last Glacial/Holocene period.
Polygon development probably involves positive feedback between morphology and frost susceptibility, driven by microclimate. The proposed method for evaluating frost sorting allows for rapid non-invasive assessment of sorting using modern methods including high-resolution remote sensing (especially terrestrial photogrammetry).