Why is there a large stone area in my desert?

So after loading a new map for 1.8 I found a desert. In the desert is a few spots where there is no sand but a blank stone face with assorted dirt, coal, etc. There is sand nearby and it gradually drops to this spot. The average height of these are y = 66. Is this just a feature of the desert biome or do others have this feature too?

Also you can see it across the river in my forest biome.

Like in real life, sometime the terrain generator makes spots of exposed stone on the surface. This seems a bit counterintuitive in a desert, but it can happen in any biome.

Occasionally, instead of being converted to dirt or sand, the top layer is stripped away, leaving a 'Basin' of bare stone. There is a common misconception in the community that these are errors, however they are an intended feature. They bear some resemblance to a geological 'shield' (an area of tectonically stable rock that has been exposed to prolonged erosion due to its very old age; it is distinct from the geological term "basin"). They seem to be more common in Forest or Plains, and are sometimes seen filled with water. Sometimes, common minerals can be found on the surface such as coal and iron ore.

Quoted From the (Unofficial) Minecraft Wiki.