Astronaut Don Pettit captured from ISS Erg Chebbi Dunes, Morocco.

Erg Chebbi Dunes, located near Algerian border, are spread 50km north-south, 5-10km east-west, and reach a height of up to 150m in places. A hard, impervious layer of rock – mainly schist – lies directly beneath the dunes and blocks water from seeping deep into the ground.
The local scenery on the ground is as follows.

Reference: Don Pettit’s Tweet
See earthview photo gallery: LiVEARTH