The Atlas Mountains extend across much of Morocco, northern Algeria and Tunisia, are part of the fold mountain system that also runs through much of Southern Europe. They recede to the south and east, becoming a steppe landscape before meeting the Sahara desert, which covers more than 75 percent of the region. The sediments of the Sahara overlie an ancient plateau of crystalline rock, some of which is more than four billion years old.
what major desert encompasses most of northern africa
the Sahara desert