"In the wake of the observations at Puzzuoli other unambiguous archaeological examples of changed sea-level were identified on the European coastline. A striking prehistoric example was recognised in the Golfe du Morbihan, France, where, on the tiny island of Er Lannic, a stone circle could by seen rising from the intertidal zone (Lukis 1868; Crawford 1927; Atkinson 1976), (see Figure 2.14, and also Plate 7p)." [from this article]

 

 Figure 2 14  112605579

Figures 1 (left) Diagram derived from sketch of the Er-Lannic flattened circle (right) Picture from http://lieuxsacres.canalblog.com (please visit for background, right click "translate to English") of Submerged circle

On the left of figure 1 one can see flattening in the south-south-east and so the question is, does this correspond with a known flattening shape as per those found by Alexander Thom, interestingly dismissed as technically impossible when built, seen only by choosing to see a geometry or perhaps, achieved without wooden pegs and ropes? When visiting the Gulf de Morbihan, this circle was referred to as type-B, but Thom did not survey El-Lannic. The diagram below was found online, in a 2000 scientific study1. It is probably good enough, from an original sketch on-site. Underwater stones are fallen (on the plus side, not re-erected). fallen stone are found in most flattened circles and, at Long Meg (a type-B), the flattened part was historically flattened by a local.

One starts by trying to find the circle that fits half (type-B) or even 5/6ths (type-A) of the ring. When the type-B geometry is applied, the stones in the flattened area seem a long way from where they should be, even assuming they fell down in a small gradiant of sea floor. In contrast, over five extra stones fit the type-A geometry, one of these in the central arc of flattening, as can be seen in Figure 2. 

Er Lannic AorB

Figure 2 The Er-Lannic diagram allows some confidence it was built as a flattened circle of type-A (red) rather than type-B (blue), in the flattened region of the forming circle. 

1. Coastal Change, Climate and Instability. Robin McInnes et al. Isle of Wight Council. 2000