The peninsula of Qatar is low-lying. Its shape is the surface expression of the Qatar Arch, one of the largest structural characteristics of the Arabian Plate. It is enveloped by loose sand and pebbles broken off the outcropping limestone. Smooth plains are found in the east, where the surface is covered by fine-grained dust. The south and south-west portion of the peninsula mainly comprises sand dunes and salt flats. Hill ranges (called 'jebels') can be found in western Qatar near the Dukhan area and at Jebel Fuwayrit on the northeast coast. Jebel Nakhsh is a notable mountain ridge south of Dukhan and contains substantial deposits of gypsum.