Forebulge

In geology, a quickly-accumulating heavy weight such as an icecap causes isostatic sinking. As this happens, mantle material is pushed away sideways from under the icecap, and may accumulate under land near the icecap and make it rise. This rise is called a forebulge [p54 in "Doggerland: a Speculative Survey", by B.J.Coles, Proceedings of the Prehistoric Society, #64 1998 pp 45-81.] . As the ice melts and the land under it rises by isostatic recovery, the forebulge sinks. Forebulge sinking is the reason why the Netherlands and parts of south England have been slowly steadily sinking.

One estimate ["Glacial deposits of Britain and Europe: general overview", by D.Ehlers, P.Gibbard, & Tj.C.E van Weering, 1979: in "Glacial Deposits in Britain and Ireland", edited by J.Ehlers, P.Gibbard, & J.Rose, pp 493-501, Rotterdam: Balkema.] is that the centre of the North Sea rose by about 170m = 558 feet because of forebulging.

References

* "Deglaciation, Earth crustal behaviour and sea level changes in the determination of insularity: a perspective from Ireland", by R.J.N.Devoy: in "Island Britain: A Quaternary Perspective", edited by R.C.Preece, pp 181-208, London: Geological Society Special Publication 96.