Cors Caron began to be formed 12,000 years ago, at the end of the last glacial period. A raised bog of this type develops from a lake or flat marshy area, over either non-acidic or acidic substrates. Over centuries there is a progression from open lake, to marsh and then fen (or on acidic substrates, valley bog), as silt or peat fill the lake. Eventually, peat builds up to a level where the land surface is too flat for ground or surface water to reach the centre of the wetland. Trees in the area that died (in about 3000 BC) and were preserved by the conditions in the bog are being studied by scientists looking for information on the past climate of the area.