At www.physorg.com/print231409994.html … a paper published in the Journal of Geophysical Research (Aug 2011) has been looking at tides in the early to mid Holocene and they have discovered some serious differences with the tides of today. For example, on the east coast of North America tides were 10 to 20 feet high compared with 3 to 6 feet of today, and tides in the Bay of Fundy, which are now very extreme, at 55 feet, were much less 5000 years ago. At that time tides on the coast of the Carolinas south to Florida were much higher than today. It seems there are spots on the earth where tidal energy get dissipated at a high rate – and one of these in the modern world is Hudson Bay in Canada. In the Ice Age Hudson Bay was frozen over so extreme tides occurred elsewhere. The same paper is discussed at http://wattsupwiththat.com/2011/08/02/the-tides-they-are-a-changin/ where it says a computer simulation lies at the heart of the research. Previoulsy, it had been assumed prehistoric tidal patterns were about the same as they are now – so this is a new discovery. As always, the comments at Anthony Watts blog are worth a perusal – providing additional information and different points of view. They begin with a touch of humour – 'I guess the Moon was closer back then …'. It is parried by another comment, well yes, it was, actually … at the rate of 38mm a year.