Saudi Arabia Topography and Natural Regions

Saudi Arabia Topography and Natural Regions

The Arabian Peninsula is an ancient massif composed of stable crystalline rock whose geologic structure developed concurrently with the Alps. Geologic movements caused the entire mass to tilt eastward and the western and southern edges to tilt upward. In the valley created by the fault, called the Great Rift, the Red Sea was formed. The Great Rift runs from the Mediterranean along both sides of the Red Sea south through Ethiopia and the lake country of East Africa, gradually disappearing in the area of Mozambique, Zambia, and Zimbabwe. Scientists analyzing photographs taken by United States astronauts on the joint United States-Soviet space mission in July 1975 detected a vast fan-shaped complex of cracks and fault lines extending north and east from the Golan Heights. These fault lines are believed to be the northern and final portion of the Great Rift and are presumed to be the result of the slow rotation of the Arabian Peninsula counterclockwise in a way that will, in approximately ten million years, close off the Persian Gulf and make it a lake.

On the peninsula, the eastern line of the Great Rift fault is visible in the steep and, in places, high escarpment that parallels the Red Sea between the Gulf of Aqaba and the Gulf of Aden. The eastern slope of this escarpment is relatively gentle, dropping to the exposed shield of the ancient landmass that existed before the faulting occurred. A second lower escarpment, the Jabal Tuwayq, runs north to south through the area of Riyadh.

In the south, a coastal plain, the Tihamah, rises gradually from the sea to the mountains. Hejaz extends southward to the borders of mountainous Yemen. The central plateau, Najd, extends east to the Jabal Tuwayq and slightly beyond. A long, narrow strip of desert known as Ad Dahna separates Najd from eastern Arabia, which slopes eastward to the sandy coast along the Persian Gulf. North of Najd a larger desert, An Nafud, isolates the heart of the peninsula from the steppes of northern Arabia. South of Najd lies one of the largest sand deserts in the world, the Rub al Khali.

A recent global remote sensing analysis suggested that there were 706km² of tidal flats in Saudi Arabia, making it the 37th ranked country in terms of tidal flat area.

Hejaz

The western coastal escarpment can be considered two mountain ranges separated by a gap in the vicinity of Mecca in Tihamah. The northern range in the Hejaz seldom exceeds 2,100 meters, and the elevation gradually decreases toward the south to about 600 meters. The rugged mountain wall drops abruptly to the sea with only a few intermittent coastal plains. There are virtually no natural harbors along the Red Sea. The western slopes have been stripped of soil by the erosion of infrequent, but turbulent rainfalls that have fertilized the plains to the west. The eastern slopes are less steep and are marked by dry river beds (wadis) that trace the courses of ancient rivers and continue to lead the rare rainfalls down to the plains.

Scattered oases, drawing water from springs and wells in the vicinity of the wadis, permit some agriculture. Of these oases, the largest and most important is Medina. South of Hejaz, the mountains exceed 2,400 meters in several places with some peaks nearing 3,000 meters. The eastern slope of the mountain range in Asir is gentle, melding into a plateau region that drops gradually into the Rub al Khali. Although rainfall is infrequent in this area, several fertile wadis, of which the most important are the Wadi Bishah and the Wadi Tathlith, make oasis agriculture possible on a relatively large scale.

Extensive lava fields (harrat) scar the surfaces of the plateaus east of the mountain ranges in the Hijaz and give evidence of fairly recent volcanic activity. The largest of these beds is Khaybar, north of Medina, another is Al Harrah, part of the large volcanic field Harrat Ash Shamah.

Tihamah

The rugged western face of the escarpment drops steeply to the coastal plain, the Tihamah lowlands, whose width averages 65 kilometers. Along the seacoast is a salty tidal plain of limited agricultural value, backed by potentially rich alluvial plains. The relatively well-watered and fertile upper slopes and the mountains behind are extensively terraced to allow maximum land use. This coastal plain is part of the Arabian Peninsula coastal fog desert ecoregion. Both Mecca and Jeddah lie within the northern part of Tihamah.

Najd

East of the Hejaz and Asir lies the great plateau area of Najd. This region is mainly rocky plateau interspersed by small, sandy deserts and isolated mountain clumps. The best known of the mountain groups is the Jabal Shammar, northwest of Riyadh and just south of the An Nafud. This area is the home of the pastoral Shammar tribes, which under the leadership of the Al Rashid were the most implacable foes of the Al Saud in the late 19th and early 20th centuries. Their capital was the large oasis of Ha'il, now a flourishing urban center.

Across the peninsula as a whole, the plateau slopes toward the east from an elevation of 1,360 meters in the west to 750 meters at its easternmost limit. Wadis cross the region in an eastward direction from the Red Sea escarpment toward the Persian Gulf. There is little pattern to these remains of ancient riverbeds, the most important of them are Wadi Hanifa, Wadi ar Rummah, Wadi as Surr, and Wadi ad-Dawasir.

The heart of Najd is the area of the Jabal Tuwayq, an arc-shaped ridge with a steep west face that rises between 100 and 250 meters above the plateau. Many oases exist in this area, the most important of which are Buraydah, Unayzah, Riyadh, and Al Kharj. Outside the oasis areas, Najd is sparsely populated. Large salt marshes (sabkah) are scattered throughout the area.

Northern Arabia

The area north of the An Nafud is geographically part of the Syrian Desert. It is an upland plateau scored by numerous wadis, most tending northeastward toward Iraq. This area, known as Badiyat ash Sham and covered with grass and scrub vegetation, is extensively used for pasture by nomadic and seminomadic herders. The most significant feature of the area is the Wadi as Sirhan, a large basin as much as 300 meters below the surrounding plateau, which is the vestige of an ancient inland sea. For thousands of years, some of the heavily traveled caravan routes between the Mediterranean and the central and southern peninsula have passed through the Wadi as Sirhan. The most important oases in the area are Al Jawf and Sakakah, just north of the An Nafud.

Eastern Arabia

East of the Ad Dahna lies the As Summen Plateau, about 120 kilometers wide and dropping in elevation from about 400 meters in the west to about 240 meters in the east. The area is generally barren, with a highly eroded surface of ancient river gorges and isolated buttes.

Farther east the terrain changes abruptly to the flat lowlands of the coastal plain. This area, about sixty kilometers wide, is generally featureless and covered with gravel or sand. In the north is the Ad Dibdibah graveled plain and in the south the 'Al Jafurah sand desert, which reaches the gulf near Dhahran and merges with the Rub al Khali at its southern end. The coast is extremely irregular, merging sandy plains, marshes, and salt flats almost imperceptibly with the sea. As a result, the land surface is unstable, in places water rises almost to the surface, and the sea is shallow, with shoals and reefs extending far offshore. Only the construction of long moles at Ras Tanura has opened the Saudi coast on the gulf to seagoing tankers.

Eastern Arabia is sometimes called 'Al-Hasa or 'Al Ahsa after the great oasis, one of the more fertile areas of the country. 'Al-Hasa, the largest oasis in the country, actually comprises two neighbouring oases, including the town of Al-Hofuf.

Geography of Saudi Arabia Overview

Saudi Arabia Continent: Asia
Saudi Arabia Region: West Asia
Saudi Arabia Coordinates: 25°00′N 45°00′E
Saudi Arabia Area: Ranked 12th
Saudi Arabia Total: 2,149,690 km2 (830,000 sq mi)
Land 100%
Water 0%
Saudi Arabia Coastline: 2,640 km (1,640 mi)
Saudi Arabia Borders: Total: 4,415 km (2,743 mi)
Saudi Arabia Highest Point: Jabal Sawda,
3,015 m (9,892 ft)
Saudi Arabia Lowest Point: Persian Gulf, Red Sea
0 m (0 ft)
Saudi Arabia Saudi Arabia Longest River: Wadi al-Rummah
600 km (373 mi)
Saudi Arabia Saudi Arabia Largest Lake: Al-Asfar Lake
20,000 ha (49,421 acres)
Saudi Arabia Climate: Most of Saudi Arabia follows a desert climate, with exceptions
Saudi Arabia Terrain: Mostly desert covered, some mountainous areas and plains
Saudi Arabia Natural Resources: Petroleum, natural gas, fish, minerals, farming
Saudi Arabia Natural Hazards: Haze, dust storms
Saudi Arabia Environmental Issues: Desertification, depletion of ground water, lack of perennial rivers or permanent water bodies, coastal pollution from oil spills
Saudi Arabia Exclusive Economic Zone: 228,633 km2 (88,276 sq mi)