Issaouane Erg confined to basins. Sand in the Issaouane Erg, below the level of the sand dunes, has accumulated to a depth of 20 to 30 meters. It has barchan dunes as well as star dunes of 300 to 430 meters high. The presence of both barchan dunes (which form due to unidirectional winds) and star dunes (which form when winds from various directions deposit sand) "suggests that wind regimes have changed over time". NASA's "Earth Observatory" notes all three types of erg dunes are present in the photos of the Issaouane Erg taken from the International Space Station: stationary mega dunes,
What Is a Nation? Language, by contrast, "invites us but does not force us, to unite". Countries which share the Spanish or English language don't merge with one another, while the people of Switzerland speak several languages. Modern nationhood also cannot be based on religion, which Renan observes, is currently practiced according to individual belief. "You can be French, English, German, yet Catholic, Protestant, Jewish, or practicing no religion". Mutuality of interests is fine for corporations and their affiliates, but nationality is based on sentiment. Geography merely leads us astray, and often to violence: "Mountains don't know how to carve out countries". Renan concludes