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Monday, 7 June 2010

Recent sea-level changes



This shows how sea-level has risen during recent times -- including Mesolithic, Neolithic and Bronze Age. Note that the dates are BP, not BC.



Post-glacial sea level rise, derived from data from many locations worldwide. There is still some doubt as to just how low sea-level dropped at the peak of the Last Glacial Episode. In the early stages of deglaciation, sea level rose at a rate of 1m per century -- but then came Meltwater pulse 1A, when sea level rose approximately 20 m over a 500 year period, about 14,200 years ago. That was a phenomenal rate, considering that we are talking here about the GLOBAL sea-level. The early dramatic rise coincided with the catastrophic collapse of the Laurentide Ice Sheet (North America) and the slightly less dramatic collapse of the Scandinavian Ice Sheet.



These raised beach terraces in NW Scotland were formed originally at a much lower altitude -- below present sea-level. But they have been lifted by post-glacial crustal rebound to c 30m above present sea level. This uplift has outstripped the eustatic rise in sea level.



Submerged forest (revealed at low tide) at Marros on Carmarthen Bay. As in all of the submerged forests around the West Wales coast, we can see fallen branches and tree trunks, peat beds, roots and stumps, and even accumulations of hazel nuts with the kernels still in place. They date from around 7,000 years ago, when Mesolithic hunters wandered these woods. The woodlands were later inundated by the rising sea-level, which here outstripped the isostatic rise of the land.

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