This activity is primarily designed to discover what the nature of flysch is as a sediment from the bottom of the ocean, and to introduce you to one of those fascinating moments in geological history, the Cretaceous Sea with marine reptiles, flying reptiles, and reefs. We will focus on the transition from the Lower to the Upper Cretaceous, which results in a change in color from dark to light, reflecting a phase of opening (with greater oxygenation) of the primitive Bay of Biscay. We will explain all this in detail.

By following the coast for a few kilometers we will observe how it changes as geological history evolves. We will observe how important subsequent deformations of the strata condition the landscape. During the walk, we will also discover different active geomorphological processes. Erosion never stops sculpting the landscape.

We will also observe in detail the layers of the flysch and the different phenomena that accompany it, as well as one of the most important elements at scientific level, which is the wealth of animal tracks that we can find on the fossil seabed.

But the history of the layers does not end after their deposition, they subsequently petrify and are subjected to numerous accidents such as faults and folds, many generated during the formation of the Pyrenees when the Iberian Plate collided with the European Plate.

The route has a height difference of about 200 meters. It is a variated walk on uneven terrain.

Recommended for children aged 12 and older with an interest in natural history.