Ruta de los Miradores de Benalúa

This photo show a typical landscape in the GEOPARQUE near Granada.

The photo shows the final part of the process where the hills made of marl and silt are in an advanced state of erosion. 

As you walk around the geopark and in the badlands you will notice that the hills contain long tubular hollows.  It is similar to Swiss  cheese but with long tapering holes.

The following is based on a text written by a geologist on a placard next to one of the "miradores" (vantage points) 

The hollows that you see in the ground are formed by  an erosive process that leads to the formation of gullies and the peculiar badlands landscape which is found in the Granada Geopark.   Rainwater attempts to drain away by penetrating through cracks in the ground. As the marl and silt is are not  particularly hard materials it is not too difficult for the water to form hollow tubes which over time get wider and deeper. When the hollow tubes reach  impermeable layers of rock , the water advances horizontally looking for a way to continue descending or to find a drainage hole. Over time, a network of tunnels (vertical and horizontal) is created, creating instability in the terrain, causing collapses with the consequent retreat of the cliff.  Successive percolation of water allows the evacuation of a large volume of material and the increase in size and continuity of the tubes, connecting the collectors with the drains. The ducts  get bigger and bigger until they become unstable and then collapse. The hillside continues to recede and the valley widens.

 

What is Marl? 

Marl is an earthy material rich in carbonate minerals, clays, and silt. When hardened into rock, this becomes marlstone. It is formed in marine or freshwater environments, often through the activities of algae.

Marl makes up the lower part of the cliffs of Dover, and the Channel Tunnel follows these marl layers between France and the United Kingdom. Marl is also a common sediment in post-glacial lakes, such as the marl ponds of the northeastern United States.

Marl has been used as a soil conditioner and neutralizing agent for acid soil and in the manufacture of cement. 



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