Moelwyn Mawr
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Geology & landscape
Geological Period: Quaternary
Landscape processes: Glacial, Periglacial
Description
Description Moelwyn Mawr is important for Pleistocene geomorphology, in particular for two types of landform whose origin is controversial. At Cwm Croesor a series of transverse boulder ridges with steep scarp fronts has been interpreted as a fossil rock glacier. As yet, its precise age and mode of formation are debatable: one suggestion is that it may have formed by unusually heavy rockfalls which swamped a small corrie glacier of Loch Lomond Stadial age. On the north-eastern slopes of nearby Moelwyn Mawr a well developed series of unsorted vegetation stripes covers an area of ca 20 ha. These stripes are arguably the finest examples of their kind in Wales. Although conventionally believed to be fossil features formed during a past episode or episodes of periglacial conditions, there is some evidence to suggest that they may be forming at the present time. Moelwyn Mawr is therefore a site of substantial geomorphological interest.