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A Rogen moraine (also called ribbed moraine) is a subglacially (''i.e.'' under a glacier or ice sheet) formed type of moraine landform,〔Hättestrand, C. & Kleman, J., 1999. Ribbed moraine formation. ''Quaternary Science Reviews, 18'':43-61〕 that mainly occurs in Fennoscandia,〔 Scotland,〔Finlayson, A. G. & Bradwell, T., 2008. Morphological characteristics, formation and glaciological significance of Rogen moraine in northern Scotland. ''Geomorphology, 101'':607-617〕 Ireland〔Dunlop, P. & Clark, C. D., 2006. The morphological characteristics of ribbed moraine. ''Quaternary Science Reviews, 25'':1668-1691〕 and Canada.〔〔Marich, A., Batterson, M. & Bell, T., 2005. The morphology and sedimentological analyses of Rogen moraines, central Avalon Peninsula, Newfoundland. ''Current Research, Newfoundland and Labrador Department of Natural Resources, Geological Survey, Report, 05-1'':1-14〕 They cover large areas that have been covered by ice, and occur mostly in what is believed to have been the central areas of the ice sheets.〔 Rogen moraines are named after Lake Rogen〔Möller, P., 2006. Rogen moraine: an example of glacial re-shaping of pre-existing landforms. ''Quaternary Science Reviews, 25'':362-389〕 in Härjedalen, Sweden, the landform's type locality. Rogen Nature Reserve serves to protect the unusual area. The landform occurs in groups that are often closely and regularly spaced.〔 They consist of glacial drift, with till being the most common constituent.〔 The individual moraines are large, wavy ridges orientated transverse to ice flow.〔 Drumlins are often found in close proximity of Rogen moraines, and are often interpreted to be formed at the same time as the Rogen moraines.〔 Although Rogen moraines can span a large range of sizes,〔 the most common distribution seems to be 10–30 metres high, 150–300 metres wide and 300-1,200 metres long.〔 The exact mechanics of Rogen moraine formation are not known, but since the 1970s, several theories on the formation have been proposed:〔 *Megaripples eroded in the basal ice fill during subglacial outburst floods.〔Fisher, T. G. & Shaw, J., 1992. A depositional model for Rogen moraine, with examples from the Avalon Peninsula, Newfoundland. ''Canadian Journal of Earth Sciences, 29'':669-686〕 *Already existing landforms, such as drumlins and flutes〔Boulton, G. S., 1987. A theory of drumlin formation by subglacial deformation. ''In'': Menzies, J. & Rose, J. (Eds.), ''Drumlin Symposium'', Balkema, Rotterdam, The Netherlands, pp. 25-80〕 or marginal moraines〔 are reshaped due to a ~90° change in the direction of the ice flow.〔〔 *Debris-rich basal ice or pre-existing sediments are sheared and stacked, or folded during compressive ice flow.〔Lindén, M., Möller, P. & Adrielsson, L., 2008. Ribbed moraine formed by subglacial folding, thrust stacking and lee-side cavity infill. ''Boreas, 37'':102-131〕 *Sediment sheets become fractured and extended during a transition of the overlying glacier from being cold based ice to warm based.〔 However, it has been suggested that, due to the diversity of morphological characteristics displayed by Rogen moraine, different processes might be able to create the landform.〔 This means that all four of the processes mentioned above might be correct. The different theories that proposed a formation near or at the glacial margin have largely been abandoned.〔 Some of these theories proposed that Rogen moraines had an origin as a series of end moraines, that they formed in association with calving ice termini in glacial lakes, or that Rogen moraines formed in dead-ice, where supraglacial material fell down into crevasses in the ice.〔 ==See also== *Drumlin 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rogen moraine」の詳細全文を読む スポンサード リンク
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