EROSION IN DETAIL
Fragile 150-metre giants
About 5,000 years ago, the sea reached its present position and began to erode our coastline, forming the cliffs that we see today.
Cliffs gradually erode, leaving behind a huge area called an abrasion platform, which can only be seen during low tides.
FLYSCH = to slide
FLYSCH is a German term and it means ‘to slide’.
The Geoparkea flysch lives up to its name. It is formed from very unstable material and also crops out in an almost vertical position. The softer strata erode easily and the harder layers slide down the slope like a puff pastry.
(Drawing 1)
- Landslides
- Pebble beach
- High tide
- Erosion
(Drawing 2)
- Retreat
- Cliffs
- Low tide
- Abrasion platform
- During storms, the Cantabrian sea lashes the cliffs with great force.
- The base of the cliffs is eroded and forms erratic shapes, which peel back the layers of the flysch.
- Rain also plays an important role by infiltrating through the upper layer, increasing the load and reducing the cohesion of the flysch. The flysch slides and tumbles away.
- Every year thousands of cubic metres of rock tumble or shift away in the cliffs of the flysch. It is a dynamic, ever-changing landscape.
- The fallen blocks are quickly rounded and the swell drags them over the shore platform, increasing the abrasive force.
- When there is a fracture, erosion acts quickly and can create caves as deep as 30 m, like the ones that have formed on Itzurun Beach. Here, we can see the bowels of the flysch.
- The small waterfalls cascading down the cliffs are clear evidence that the cliffs are receding fast, or at least faster than the could be accounted for by the incision capacity of the rivers that are forming the valley.
- The shore platform is the indelible mark left by the cliffs when they retreat.