Cwm Dwythwch
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Geology & landscape
Geological Feature: Moraine
Landscape processes: Glacial
Description
Description Of geological interest. Cwm Dwythwch is important for interpreting Late Devensian glacial history and environmental conditions in North Wales. It provides geomorphological evidence in the form of moraines for two separate glacial stages. Pollen analysis from a core taken inside the outer moraine demonstrates that the latter pre-dated the Loch Lomond Stadial. While its exact age and origin are uncertain, it provides some of the best evidence for elaborating glacial conditions at the end of, or immediately following the last major glaciation of the area. During the later Loch Lomond Stadial, small glaciers again occupied the cwm and formed inner moraines. The pollen record preserved in the sediments in the floor of the cwm extends back to the early part of Late-glacial and provides a record of Late-glacial and early Flandrian environmental changes. Remarks This site lies within the Snowdonia National Park.