It is composed of differing materials : the Tanezrouft contains mostly sandstone deposits , whereas the Hoggar formations are metamorphic rocks .
Tanezrouft is a barren plain extending to the west of the Hoggar mountains and to the southeast of the sandy Erg Chech .
Tanezrouft is composed of differing materials : the Tanezrouft contains mostly sandstone deposits , whereas the Hoggar formations are metamorphic rocks .
Tanezrouft is a barren plain extending to the west of the Hoggar mountains and to the southeast of the sandy Erg Chech .