There was a thread about the Moffat book, dunno if it mentioned the tsunami. There was also one about when Britain first got cut off from the continent, Doggerland etc in which Mr Fitzcoraldo pointed a link in the direction of this:

http://en.wikipedia.org/wiki/Storegga_Slide
which was apparently the cause of that mesolithic period tsunami, and according to this:
http://www.fettes.com/Shetland/Storegga.html
there have been 3 such landslides.

Makes me wonder if such a tsunami could have put paid to a fair chunk of Doggerland,all in one go. Or at least made the inhabitants think about the merits of moving to higher ground.