A paper in Nature Geoscience is featured at www.physorg.com/print229678808.html and has confirmed that the ocean floor off the northern coast of Scotland was at one time as much as a km above the sea – an area of 10,000 square miles NE of Orkney and the Shetlands, currently 2km below sea level. This information comes from geological soundings by oil contractors who mapped the sea bed. Beneath the layer of silt and other debris a lost land, one that had been pushed up by expansion of the mantle (it is conjectured). Rivers and mountain peaks were found and fossils said to date back 56 million years ago. The ocean floor rose up to create a huge island that existed for a million years before being submerged once again.
At www.bbc.co.uk/news/uk-scotland-highlands-islands-14137259?print=true the story is more recent and belongs to the last few thousand years. It concerns the drowning of ancient communities around the Western Isles. In particular, the lochs and inlets seem to be quite recent in date much as they are on mainland Britain – and may hide Mesolithic relics (conjecture). Rising sea levels, it is argued, may have covered 10km of land to the west of the Outer Hebrides. This occurred, it is said, conjecture once again, around 9000 years ago. However, it appears to coincide more properly with the 6000BC event that was prompted, or included, a collapse of the Storegga Shelf in Norwegian waters, creating a tsunami that struck the eastern side of Scotland. The piece then gets muddled with the drowning of the North Sea basin and Channel, conflating what may have been more than one event.