Rub' al Khali

Lore & Background

The sand is reddish-orange due to feldspar. Brackish salt flats exist in some areas, such as Umm al Samim. Along the desert's middle length are raised areas of calcium carbonate, gypsum, marl, or clay that were once shallow lake beds, which existed during periods 6,000 to 5,000 years ago and 3,000 to 2,000 years ago. These lakes likely formed from cataclysmic rainfall and lasted only a few years, though some in the Mundafen area lasted up to 800 years. Fossil remains indicate hippopotamus, water buffalo, long-horned cattle, snails, ostracods, and freshwater clams. Evidence of human activity from 3,000 to 2,000 years ago includes chipped flint tools, but no human remains have been found.

Reader's Guide

The Rub' al Khali is significant as one of the world's largest sand deserts and a key part of the Arabian Desert ecoregion. Its hyper-arid climate, with annual precipitation under 50 mm, supports limited biodiversity including arachnids, rodents, and the dromedary camel. Archaeological remains include a fortification, walls, and circular pillar bases.

Did You Know?

• The desert contains brackish salt flats such as Umm al Samim.
• Fossil remains of hippopotamus, water buffalo, and long-horned cattle have been found in ancient lake beds.
• The first documented journeys by non-resident explorers were made by Bertram Thomas and St John Philby in the early 1930s.