It is the lithosphere that is broken into tectonic plates, which undergo some large-scale motions. The boundary regions between plates are aptly called “plate boundaries.” Based upon their motions concerning one another, these plate boundaries are of three kinds: divergent, convergent, and transform.
Wind erosion is the main cause. And since it is the desert that wind can pick up tiny sand rock particles that slowly grind against the rock. Over time the erosion will give a jagged rock the smooth features as if it had been submerged in a river for the roughly same period of time.
This breed is called metamorphic rocks - rocks formed in the Earth's crust as a result of metamorphism, ie the change of sedimentary and igneous rocks due to changes in physical and chemical conditions
The answer to your question is knowledge. Scientific knowledge is the information gathered by the systematic study of nature.
1. Crust
2. Mantle
3. Inner core
4. Outer core
