Sunday, 8 December 2013
Erosion at Sanna
Sanna is famous for its sands. We had always assumed that the sand was the product of the erosion of the underlying rock, a dark igneous rock called gabbro, but it isn't. The sand is almost entirely formed of smashed fragments of sea shells.
Perhaps it is the result of rising sea levels, though the land in this part of Scotland is also rising in isostatic response to the removal of the glaciers that once weighed it down. Perhaps the dominant winds are changing, so there is less of the constant onshore westerlies that must have built the machair. Perhaps there are other reasons, but Sanna beach is changing.