Just inside the Arabian Desert is the city of Dubai. The geography of Dubai, however, differs greatly from that of the southern part of the United Arab Emirates in that much of Dubai’s terrain is emphasized by sand desert patterns, whereas gravel deserts predominate much of the southern part of the nation. The fine, pure, and white sand is primarily composed of crushed shell and coral. The sabkha, or salt-crusted coastal plains, end east of the city and give place to a stretch of dunes that runs north to south. The dunes expand and acquire an iron oxide-red tint farther east.