Deserts may look very different. Even if all what is visible is stone and sand - stones and sand can look very different in different regions. This depends on the material. There are regions where the basic color of the stones is black, so the desert looks quite black. Of course, the White Desert , (known as Sahara el Beyda, or as-Sahra al-baida, in arabic الصحراء البيضاء) looks white.
The White Desert is a national park of Egypt founded 2002, with a size of 3010 km², and is located between the oasis of Farafra ( الفرافرة ) and the oasis of Bahariya (الواحات البحرية ), around 500 km south-west of Cairo.
The forms of rocks in the white desert seem quite fantastic and strange, very different from what one knows and expects. This makes it worth to think about how they have been created.
The mushroom-like rocks in these pictures have something in common: The material of the hat is different from the material of the stem, which is visible already from the color, with the stem being much whiter than the hat. So, at least part of the explanation seems clear: The material of the hat is simply more rubust.
This will be part of the explanation for these strange umbrella-like formations too. What is located at the same height has been sedimented at the same time and consists of almost the same material, so one can expect less robust material at lower height to lead to such effects.
But this cannot be all yet. Different materials at different height we have almost everywhere. But, of course, usually one would expect not such extremal consequences. Something like the pyramid-like mountain – ok, but not such umbrella-like structures.
Part of the explanation is that one needs a very arid environment, so that water and vegetation does not play an important role. Because what is the result of the work of water and vegetation is what we know from other places.
So, such unusual rocks we can find at places where these actors have no influence – in deserts. So that what we observe here is created by another actor – sandstorms. So, how sandstorms act? What is their effect on the landscape?
This is much better visible at places where the rocks themself seem more homogeneous. As we see, we have almost vertical rocks, down to the bottom of the rock. Such rock formations are text-book examples of ventifact and have been created as a result of occasional sandstorm in the area. "Even in strong winds, sand grains can't be continuously held in the air. Instead, the particles bounce along the ground, rarely reaching higher than a few feet above the earth. Over time, the bouncing sand grains erode the lower portions of a ventifact more strongly, which can leave a larger less eroded cap.
On the other hand, one can find in the white desert also things which have been created by water.
Indeed, what you see here, in the middle of the desert, are typical dripstone sculptures. And dripstone is something created by water.
The white material is chalk. It sedimented and calcified plankton from the end of the Cretaceous period 80 million years ago. At that time, the Mediterranean Sea covered this part of the desert.
That there was sea in the past, at the time when this chalk has been created, is nothing you have to believe — you can check this yourself: It is possible (and not really difficult) to find here petrified remains of shells.
Here is how the white desert looks like from satellite (from google maps: