English: Swanlake Bay View over the western part of the bay, showing cliffs up to 40m high and a wave-cut platform (seen here at mid-tide).

Vertical layers (beds) form part of the sequence of rocks referred to as the Old Red Sandstone. Near the top of the cliffs, slight curvature of the beds shows evidence of mass movements (solifluction flows) during the latter part of the Ice Age. As a result of post-glacial rise in sea level, marine erosion has removed most of the solifluction flow deposits, although there are some remnants behind the sandy beach.

The development of the bay has been facilitated by erosion along numerous faults. Some of these show up as gullies cutting across the layers in the wave-cut platform. The orientation of the faults can be measured from vertical air photos (eg. Google Earth). Frictional forces caused the changes in orientation (strike) of the bedding which coincide with the faults.

I have a theory that the name Swanlake is derived from the Viking chieftain Sweyn (as in Sweyn's Ey, now Swansea) and that the Lake part of the name may be a Norse word for spring or stream, as there are several of these behind the sandy beach. This secluded bay would have been a safe place for Viking raiders to obtain supplies of fresh water.