Originally posted by IgorZ It's amazing how big these dunes are... Are they all the same colour? I read a book by a guy who traveled in the Arabian Peninsula. He said dunes there are of different colours.
The dunes we saw were predominantly pale to deeper orange, with the depth of color depending on weather & time of day (cloudy vs sunny - midday vs, early morning or near sundown). There are patches or slashes of near black where magnetite grains have accumulated as a lag concentrate on the surface of a dune. The "dune sea" ends with startling abruptness where very old rocks have been uplifted during the collision of proto-Africa with proto-South America.