In 1951, an underground seam from Rossington Colliery undermined the area of Low Ellers, and was followed by further seams which affected the whole of the Carr between 1960 and 1967. The effects were not immediate. In 1955, the area of Low Ellers was no more than a damp pasture and even by 1959 had not become much wetter. From this time onwards, however, the effects of subsidence became more severe and by 1963 the eastern side of Low Ellers had been transformed into marsh with a small, but permanent, area of open water. The subsidence continued and by 1965 Balby Carr had also flooded whilst the marsh at Low Ellers had extended. After a lapse of 200 years the term "inundated" could once again be used to describe part of Potteric Carr. Those areas which had not become completely flooded were at least very wet. One loss during this period were the trees in the Young Eaa Plantation and a part of the Old Eaa Plantation which died as a consequence of the flooding. There followed, however, a very fast colonisation of the area by marsh plant communities which once typified the Carr and naturally, following this, the return of the animal life.
