Coordinates: 20°N 50°E / 20°N 50°E / 20; 50

Rub' al Khali (Arabic: الربع الخالي‎)
Desert
Sand dunes in the Rub' al Khali.
Countries	Saudi Arabia, Oman, United Arab Emirates, Yemen
Length	1,000 km (621 mi)
Width	500 km (311 mi)
Area	650,000 km2 (250,966 sq mi)
Location of the empty quarter in Arabia.

The Rub' al Khali (Arabic: الربع الخالي‎) or Empty Quarter is the largest sand desert in the world,^[1] encompassing most of the southern third of the Arabian Peninsula, including most of Saudi Arabia and areas of Oman, the United Arab Emirates, and Yemen. The desert covers some 650,000 square kilometres (250,000 sq mi) (the area between long. 44°30′ −56°30′E., and lat. 16°30′ −23°00′N).^[2]

Description[link]

Typical pale gravel plains surrounded by huge sand dunes.

Water found just 3 meters deep from ground level.

Terrain[link]

The desert is 1,000 kilometres (620 mi) long, and 500 kilometres (310 mi) wide. Its surface elevation varies from 800 metres (2,600 ft) in the southwest to around sea level in the northeast.^[3] The terrain is covered with sand dunes with heights up to 250 metres (820 ft), interspersed with gravel and gypsum plains.^[2][3] The sand is a reddish-orange color due to the presence of feldspar.^[3]

There are also brackish salt flats in some areas, such as the Umm al Samim area on the desert's eastern edge.^[3]

Lake beds[link]

Along the middle length of the desert there are a number of raised, hardened areas of calcium carbonate, gypsum, marl, or clay that were once the site of shallow lakes. These lakes existed during periods from 37,000 to 17,000 years ago and 10,000 to 5,000 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 lasting longer, up to 800 years, due to increased runoff from the Tuwaiq Escarpment.^[2]

Evidence suggests that the lakes were home to a variety of flora and fauna. 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 10,000 to 5,000 years ago, including chipped flint tools, but no actual human remains have been found.^[2]

Climate[link]

The region is classified as "hyper-arid", with typical annual rainfall of less than 30 millimetres (1.2 in). Daily maximum temperatures average at 47 °C (117 °F) and can reach as high as 56 °C (133 °F).^[3]

Biodiversity[link]

Fauna includes arachnids (e.g. scorpions) and rodents, while plants live throughout the Empty Quarter. As an ecoregion, the Rub' al Khali falls within the Arabian Desert and East Saharo-Arabian xeric shrublands.^[3]

Oil[link]

Geologically, the Empty Quarter is the most oil-rich site in the world.^{[citation needed]} Vast oil reserves have been discovered underneath the sand dunes.^{[citation needed]} Sheyba, at the northeastern edge of the Rub' al Khali, is a major Arab light crude oil-producing site in Saudi Arabia. Ghawar is the largest oil field in the world, which extends southward into the northernmost parts of the Empty Quarter.

History[link]

Satellite image of sand dunes in the Empty Quarter.

Desertification has increased through the millennia. Before desertification made the caravan trails leading across the Rub' al Khali so difficult, the caravans of the frankincense trade crossed now virtually impassable stretches of wasteland, until about AD 300.^[4] It has been suggested that Ubar, or Iram, a lost city, depended on such trade.^[5] The traces of camel tracks, unidentifable on the ground, appear in satellite images.^[6] More recently, tribal populations were also present in certain parts of the Empty Quarter, with the largest in the Najran region. A few road links were connected with these tribal settlements to the water resource and oil production centers.

Expeditions[link]

After Pedro Páez's presence in the late 16th century, the first documented journeys by Westerners were made by Bertram Thomas in 1931 and St. John Philby in 1932. Between 1946 and 1950 Wilfred Thesiger crossed the area several times and mapped large parts including the mountains of Oman.

In June 1950, a U.S. Air Force expedition crossed the Rub' al Khali from Dhahran, Saudi Arabia, to central Yemen and back^[7] in trucks to collect specimens for the Smithsonian Institution and to test desert survival procedures.^[8]

On February 25, 2006, a scientific excursion organized by the Saudi Geological Survey began to explore the Empty Quarter. The expedition was led by a team of 89 environmentalists, geologists, and other scientists, from Saudi Arabia as well as experts from abroad. Various types of fossilized creatures as well as meteorites were discovered in the desert. The expedition also led to the discovery of 31 new plant species and plant varieties, as well as 24 species of birds that inhabit the region, which fascinated scientists as to how they have survived under the harsh conditions of the Empty Quarter.^[9]

In fiction[link]

• Rub' al Khali is one of the settings for the Playstation 3 video game Uncharted 3: Drake's Deception, in which protagonist Nathan Drake searches for the Iram of the Pillars.
• The Empty Quarter plays an important role in Clive Barker's Jericho, and in his novel Weaveworld, and in Tim Powers' Declare.
• It also serves as the site of Machine City, Zero-One, in the Matrix series.
• Gerald Seymour's novel Unknown Soldier is almost entirely set in the Rub' al Khali.
• Jack Higgins sets much of the action in his novels Edge of Danger and Midnight Runner in the Empty Quarter.
• The Empty Quarter is also mentioned several times in The Black Stallion series of books from Walter Farley.
• Much of the SIGMA Force book Sandstorm by James Rollins takes place in the Empty Quarter.
• The Empty Quarter serves as the location of the fictional "Ocean of Fire" horse race in the 2004 film Hidalgo. Filming of the movie actually occurred at various locations in the U.S.A. and Morocco.
• In the Japanese light novel series Zero No Tsukaima, Rub' al Khali is thought to be the place of origin of the main character, Hiraga Saito.
• In Daniel Easterman's second novel, The Seventh Sanctuary it is the location of the lost city of Iram, where the eponymous seventh sanctuary is situated.
• The Fremen people of Frank Herbert's novels on Dune are said to stem from tribes of the Rub' al Khali.

Additional images[link]

• 

  Astronaut photograph highlighting a part of the Ar Rub’ al Khali near its south-eastern margin, in Oman.

• 

  Sunset in Rub' al Khali in Saudi Arabia

See also[link]

Wikimedia Commons has media related to: Rub' al Khali

• Ramlat Khaliya

References[link]

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (August 2010)

External links[link]

• Lost city under the Rub’ Al-Khali, Saudi Life.
• Sights & Sounds: The Empty Quarter: A National Geographic virtual tour in the Empty Quarter.
• Clear picture of some of the dunes in the Empty Quarter.