Eustatic

Eustatic sea level changes are longterm fluctuations in the absolute volume of sea water held in the oceans of the earth. Such fluctuations have occurred throughout the Quaternary, due to changes in the extent of ice-sheets and thus in the volume of water locked up as ice. The larger the ice-sheets, the less water available to the sea, and so sea level is lower during glacials than during interglacials. Evidence exists for a whole series of eustatic sea level fluctuations, but the most widespread is the ‘high stand’ on cl20,000 bp, just before the start of the last cold stage (De-vensian, Weichselian, Wisconsin), when sea levels were between two and ten metres higher than at the present day. During the maximum extent of the ice-sheets of the last cold stage, eustatic sea level was much lower than that of today. Large areas of continental shelf were exposed, some being occupied by the ice-sheets themselves. Recovery of sea level at the end of the last cold stage is relatively well known from deposits in the Netherlands, Scandinavia and Scotland, but is complicated by isostatic changes. The North Sea and English Channel flooded, separating Britain from the Continent, by about 7000 bp. Ireland became a separate island at about the same time. Scandinavia had a complicated series of different seas and lakes, until a sea similar to today’s Baltic became established around 7000 bp.