Answer:
It is difficult to cross.
Step-by-step explanation:
The Sahara desert is a vast region about the size of the continental United States that is extremely dry and barren. The lack of water resources in the desert make the land unsuitable for agriculture and human population.
As a result, the Sahara acts as a giant natural wall both economically, culturally, and socially since relations between states to the north and south of the desert are difficult.