GETXO

MAGNETIC BEACHES

THE CEMENTED BEACHES OF GORRONDATXE-AZKORRI AND TUNELBOKA

Along the Flysch of Biscay Route you can discover two beaches - Gorrondatxe (Azkorri) and Tunelboka - whose sands have undergone cementation.

Cementation is caused by the precipitation of calcite cement from ocean spray when the waves crash into the beach.

Geologists call it “beachrock”, because it's petrified. But, do you know how that happened? In the first half of the 20th century a lot of industrial slag and dross was dumped into the mouth of the Abra. That material was dragged to the ocean and deposited on the coast, which caused the formation of sedimentary rocks on the nearby beaches, like the two mentioned above.

You don't need to look far to find remains of bricks, drink tins and cans, shards of glass or even plastic between the layers of petrified sand. Experts have named these fragments technofossils. A few secrets are also hidden in the loose sand. All you need is a magnet to see how some sediment will stick because it comes from slag from the metallurgy industry.