The unusual square waves of the island of Ré

Sometimes Nature is entertained in playing with shapes and textures, as if, boring and mischievous, it wanted to attract our attention. Whimsically eroded rocks, clouds forming silhouettes, lakes of unusual colours… In France, for example, there is a coastal spot where, sometimes, the sea surface is geometrically articulated forming something very similar to a chessboard. A water grid. Curious, isn’t it?

The island of Ré is a piece of land located off the French west coast, in the Cantabrian Sea, connected to the mainland by a long bridge of almost three kilometers inaugurated in 1988.

The island is small, about thirty kilometres long by five kilometres wide, with an area of eighty-five square kilometres, and practically flat, as the highest point does not exceed twenty metres.

Map of the island of Re / photo Pline on Wikimedia Commons

These modest dimensions have not deprived it of an interesting history. Due to the proximity of La Rochelle, it was involved in the French and English wars for its possession, just as in World War II it was fortified by the Germans with bunkers from its famous Atlantic Wall that are still preserved (part of the film The Longest Day about the Allied landing in Normandy was shot there); also, because of its insular character, Ré also served as a prison in the second half of the 17th century.

Today, however, it stands out for other things. In the first place, because it is an outstanding holiday centre that in summer multiplies its usual population by ten, reaching a total of one hundred and sixty thousand people. Therefore, the island has many tourist infrastructures, from hotels to restaurants through campsites, shops, a port, leisure and adventure companies … It is not surprising that many celebrities choose the place for some of their escapades and have built homes there, such as the politician Lionel Jospin (who was also born there), singer Charles Aznavour, actress Carole Bouquet, Princess Carolina of Monaco, and so on.

There is also their traditional business: the salt industry, which dates back to Roman times, when Ré was made up of three islets and the channels that separated them were used to collect the product. The salt flats occupy up to twenty percent of the total surface area and produce around two thousand five hundred tonnes per year (a minimum part compared to the beginning of the 20th century), although they are no longer all used to extract salt; they are also used to maintain the rich native flora and fauna.

German bunkers on the island of Re / photo ile-de-re-commonswiki on Wikimedia Commons

However, without a doubt, one of Ré’s greatest attractions is located in the northwest of the island: the Whale Lighthouse, named after the large number of cetaceans that used to visit the area in the past. The lighthouse was built in 1854 and measures fifty-five meters high, which can be climbed up a spiral staircase of two hundred and a half steps. The incentive is threefold: there is no entrance fee, the panoramic views are magnificent and from there, with a little luck, it will be possible to appreciate one of the most surprising natural phenomena on the island, the one I mentioned at the beginning.

These are sine waves, which have constant amplitude and well-defined periods of length and wavelength. That is to say, regular waves that adopt a quadrangular shape, in this case as a consequence of the collision between two oblique bottom seas.

Bottom seas originate at depths of kilometers and, together with other factors (wind, for example) make the waves travel long distances, adopting the sea surface this unusual formation in checkerboard. Be careful, though, because the waves are spectacular but dangerous.

This article was first published on our Spanish Edition on April 5, 2019. Puedes leer la versión en español en El científico que plasmó el Imperio Ruso en fotografías en color antes de que éstas se inventasen