Rub' al Khali

Lore & Background

The desert is 1,000 km long and 500 km wide. Its surface elevation varies from 800 m in the southwest to around sea level in the northeast. Most of the terrain is ergs, with sand dunes up to 250 m high, interspersed with gravel and gypsum plains. The sand is reddish-orange due to the presence of iron oxide. There are also brackish salt flats in some areas, such as the Umm al Samim area on the desert's eastern edge. Along the middle length of the desert, there are several raised, hardened areas of calcium carbonate, gypsum, marl, or clay that were once the site of shallow lakes. These lakes existed during periods from 6,000 to 5,000 years ago and 3,000 to 2,000 years ago. The lakes are thought to have formed as a result of 'cataclysmic rainfall' similar to present-day monsoon rains and most probably lasted for only a few years. However, lakes in the Mundafen area in the southwest of the Rub' al Khali show evidence of such lakes lasting longer, up to 800 years, from increased runoff from the Tuwaiq Escarpment. Fossil remains indicate the presence of several animal species, such as hippopotamus, water buffalo, and long-horned cattle. The lakes also contained small snails, ostracods, and when conditions were suitable, freshwater clams. Deposits of calcium carbonate and opal phytoliths indicate the presence of plants and algae. There is also evidence of human activity dating from 6,000 to 5,000 years ago and 3,000 to 2,000 years ago, including chipped flint tools, but no actual human remains have been found. The region is classified as 'hyper-arid', with annual precipitation generally less than 50 mm, and daily mean relative humidity of about 52% in January and 15% in June–July. Fauna includes arachnids (e.g. scorpions) and rodents, while plants live throughout the Empty Quarter. The dromedary, or Arabian camel, is an important part of the fauna, with the black camels of Oman being a rare and prized breed. As an ecoregion, the Rub' al Khali falls within the Arabian Desert and East Saharo-Arabian xeric shrublands. The Asiatic cheetah, once widespread in Saudi Arabia, is extirpated. The Shaybah oil field was discovered in 1968. South Ghawar, discovered in 1948, is the largest oil field in the world and extends southward into the northernmost parts of the Empty Quarter. A road between Oman and Saudi Arabia, through the Empty Quarter, was completed in September 2021.

Reader's Guide

The Rub' al Khali is a vast desert covering most of the southern third of the Arabian Peninsula. It spans parts of Saudi Arabia, Oman, the United Arab Emirates, and Yemen. The terrain is dominated by sand dunes up to 250 m high, with gravel and gypsum plains and brackish salt flats. The climate is hyper-arid, with annual precipitation less than 50 mm. Travel across the desert is challenging; a road between Oman and Saudi Arabia was completed in September 2021, measuring 700–800 km from Ibri to Al-Ahsa. Numerous expeditions have crossed the desert on foot, including a 2013 South African team, a 2013 South Korean team, and a 2020 Italian explorer. The desert is home to various tribes, including the Al Murrah, Banu Yam, Banu Hamdan, and Bani Yas.

Did You Know?

• The sand is reddish-orange due to the presence of iron oxide.
• The desert covers approximately 650,000 km².
• The first documented journeys by non-resident explorers were made by British explorers Bertram Thomas and St John Philby in the early 1930s.
• The Asiatic cheetah, once widespread in Saudi Arabia, is extirpated from the region.
• The Shaybah oil field was discovered in 1968.