Saudi Arabia

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2

Najd

An arid, rocky plateau known as Najd occupies the interior of Saudi Arabia. The western half of the plateau is a desolate tableland of broken volcanic rock crossed by wadis (watercourses that flow only after rains). In the eastern half numerous rocky ridges run north to south. Bordered on its north, east, and south by desert areas, Najd itself also contains several deserts, including Nafūd ad Daḩy, a series of sandhills and ridges that divide western Najd from eastern Najd.

A

3

Al Aḩsā’

In the east, along the Persian Gulf, is the low-lying region of Al Aḩsā’, known for its vast petroleum deposits, farms, and gulf ports. Here, natural springs made agriculture and large-scale settlement possible long before the discovery of the region’s rich oil reserves. The agricultural oasis of Al Qaţīf is noted for its large plantations of date palms. The coast consists of salt flats (called sabkhas), marshes, lagoons, and sandy or rocky beaches. Offshore coral reefs, mud islands, and sand bars made navigation difficult before channels to ports were dredged in the 20th century.

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4

Deserts

Considerably more than half the area of Saudi Arabia is desert. Some desert areas are covered with shifting sand dunes, while others are more stable flat or rippled expanses of sand. Shaped and moved by winds, sand dunes take the form of long ridges or tall hills. Sand, gravel, or bare rock basins lie between the dunes. Few plants grow in these arid deserts, except in scattered oases supported by springs or wells. Three large deserts lie on three sides of the country’s central plateau: An Nafūd to the north, the Rub‘ al Khali to the south, and the narrow Ad Dahnā’ connecting these two on the east. The Rub‘ al Khali, one of the largest deserts in the world, has an area of about 650,000 sq km (about 250,000 sq mi), nearly as large as the U.S. state of Texas.

An Nafūd is characterized by parallel sand ridges, most 6 to 15 m (20 to 50 ft) high, but some sand hills rise as high as 30 m (100 ft). In some areas, wind has stripped the bedrock surface clean of loose material. North of An Nafūd are the southern fringes of the Syrian Desert.

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A belt of sand hills and ridges known as Ad Dahnā’ extends in an arc south from An Nafūd, separating Najd and Al Aḩsā’. Ad Dahnā’, varying in width from 24 to 80 km (15 to 50 mi), connects the northern desert regions with the Rub‘ al Khali in the south. A similar but discontinuous band of sand ridges lies on the western edge of Najd, also connecting An Nafūd and the Rub‘ al Khali.

Rub‘ al Khali means “Empty Quarter” in Arabic, reflecting the barren and forbidding nature of the southern Arabian desert. It is much larger and drier than the other Saudi deserts, contains no oases, and can only be inhabited temporarily, in the cooler winter months, by camel-herding nomads called Bedouins. The Rub‘ al Khali extends over much of southeastern Saudi Arabia and beyond the southern frontier into Yemen and Oman. Like An Nafūd, the Rub‘ al Khali is a sea of sand ridges and hills, some of which are as high as 150 m (500 ft). One of the world’s best-preserved meteor impact sites is located in the middle of the Rub‘ al Khali, at a site called Wabar.

B

Climate

Extreme heat and aridity are characteristic of most of Saudi Arabia. It is one of the few places in the world where summer temperatures above 50°C (120°F) are common, while in winter frost or snow can occur in the interior and the higher mountains. The average temperature range in January is 8° to 20°C (47° to 68°F) in Riyadh and 19° to 29°C (66° to 83°F) in Jiddah. The average range in July is 27° to 43°C (81° to 109°F) in Riyadh and 27° to 38°C (80° to 100°F) in Jiddah. Precipitation is usually sparse, although sudden downpours can lead to violent flash floods in wadis. Annual rainfall in Riyadh averages 100 mm (4 in) and falls almost exclusively between January and May; the average in Jiddah is 54 mm (2.1 in) and occurs between November and January.

C

Natural Resources

Some of the world’s largest oil and natural gas fields lie beneath Saudi Arabia and its offshore waters, representing the country’s most economically important natural resource. In 2007 Saudi Arabia’s oil reserves were estimated at 264 billion barrels. Before the discovery and exploitation of these reserves in the mid-20th century, Saudi Arabia was one of the poorest countries in the world. Its relatively small population subsisted in a harsh environment with little agricultural land and limited water resources. Saudi Arabia lacks permanent lakes and rivers, but considerable reserves of underground water have been discovered across the country. These have been used to increase agricultural production and provide water for the growing population. Desalination plants on the Persian Gulf and Red Sea coasts provide important, if expensive, sources of water. In addition, a number of dams built across wadis capture seasonal rainwater temporarily.

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