On the Basque Coast everyone talks about flysch. But what exactly is flysch? During this activity you will discover what is special about these rocks from the depths of the ocean, and it will introduce you to one of those fascinating moments in geological history, the Cretaceous Sea with ammonites, marine reptiles, flying reptiles, and reefs.

In the picturesque town of Deba, on the banks of the river with the same name and along the beaches, we find dark flysch cliffs that let us read their history.

We also find reef limestones that show us their fossils. These famous monumental limestones are mostly "marbles" from Lastur, a well-known quarry located in a large reef nearby. Deba has a very rich geology that gives a good idea of the oldest flysch in the Geopark, and the events that happened during its formation.

We will complete the visit with a walk through the Deba River estuary where we will learn what an estuary is, and we will imagine us this landscape during the last ice age. Furthermore, in this Valley of Prehistory we will discover the history of human presence during the Pleistocene.

For the more sporty, there is the possibility of learning about the geomorphology of karst landscapes from the terrace above the Sasiola meander, where all the elements of Deba's landscape unites.

It is an ideal place to learn about the relationship between deep-water flysch and reefs. These geological features are generally easily accessible by wheelchair and when this is not the case, we will use binoculars.

I will adapt the activity depending on your mobility.

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