The flysch rock layers off the Bizkaia coast began to form 110 million years ago beneath the sea through the build-up of sediments over a period of approximately 60 million years. These sediments were deposited slowly, forming numerous layers with different compositions depending on the type of flysch. The harder ones consisted of limestones and/or sandstones, while the softer ones involved loams and/or shales, with these layers alternating with each other. In some cases, however, these deposits were formed by huge submarine landslides of sediments, or by the subsidence of the seabed due to the opening of the Bay of Biscay, forming layers called turbidites.
This formed all the layers of the Bizkaia Flysch although, of course, they were still underwater. How did these rocky formations that we can now admire from our clifftops rise to the surface, appearing in full view at low tide?
This process took place mainly during the so-called GRANDE COUPURE, or great upheaval, between the Cretaceous and Oligocene epochs, when the small Iberian tectonic plate collided with the much larger European one, and all the sediments that had formed over millions of years were folded, fractured and raised to create most of the folds and elevations that we can now see in Euskadi-The Basque Country, as well as large mountain ranges such as the Pyrenees and the Himalayas.
Places of geological interest
Between the coastal towns of Getxo and Bakio, from one site to the next and step-by-step, you can discover the 16 Places of Geological Interest along the Bizkaia Flysch route.
Almost all these places are located on the coast, with the only exception being the Pequeña Calzada de los Gigantes de Fruiz (The Giants’ Causeway in Fruiz), but all you need to do is take a short detour inland, and you’ll see it is well worth a visit.
You can follow the route in either direction, and the views are simply spectacular. Part of it runs along the so-called Ruta de los Acantilados (Clifftop Route), which links the towns of Getxo and Plentzia, regaling you with some of the finest panoramic views along Bizkaia’s coastline.
Discover the secrets concealed in the rocks along the shore by reading the information panels dotted along the Bizkaia Flysch route or on one of the guided tours available.
If you have a sense of adventure, come and enjoy the activities we have arranged for you.