On top of the Causse de Sauveterre, you will see everywhere closed depressions. That is very rare in common landscapes because rivers open up closed depressions and create open valleys. But in limestone plateaus such as the Causse de Sauveterre closed depressions or dolinas are very common. Very frequently, such a closed depression starts with a collapse of one of the caves just below the surface. But while normal depressions would fill up with water, overflow and erode to an open valley, the water in these depressions have a way out via the cracks in the limestone beneath. As a result, more and more limestone desolves, soil get developed and deposited in the depression. The soil does not erode and becomes a thick and fertile layer. While on the sides and top, the soil is thin and rocky. You will notice the big change in the land use between the different part of the dolina profile.