Iran

I

Introduction

Iran, officially Islamic Republic of Iran, republic in the Middle East, bordered to the north by Armenia, Azerbaijan, Turkmenistan, and the Caspian Sea; to the east by Afghanistan and Pakistan; to the south by the Gulf of Oman, the Strait of Hormuz, and the Persian Gulf; and to the west by Iraq and Turkey. The country was a constitutional monarchy ruled by a shah from 1906 until 1979, when a popular uprising led by Islamic religious leaders resulted in the establishment of an Islamic republic. The area of Iran is 1,648,000 sq km (636,300 sq mi). Until the 1930s Iran was known abroad as Persia. The capital and largest city is Tehran.

II

Land and Resources

Most of Iran is made up of rugged terrain. The country contains enormous mineral wealth, much of which has yet to be exploited. Iran is subject to some of the world’s most severe earthquakes, and the geological instability has frequently resulted in major physical damage and great loss of life.

Iran is dominated by a central plateau that is about 1,220 m (4,000 ft) high and is almost ringed by mountain chains. In the north are the Elburz Mountains, paralleling the southern shore of the Caspian Sea. The highest peak in Iran, Mount Damāvand (5,604 m/18,386 ft), is part of this mountain system. The Caspian Sea, at 28 m (92 ft) below sea level, is the lowest point in Iran. Along the western border the complex Zagros Mountains extend south-east, running parallel to the Persian Gulf. Mountains of lower elevation lie to the east of the central plateau. Except for the relatively fertile plateaux of the northern Iranian provinces of East and West Azerbaijan, the mountain soils are thin, heavily eroded, and infertile. The narrow Caspian coastal plain, in contrast, is covered with rich brown forest soil. The only other generally flat area is the plain of Khuzestan in the west.

Two great deserts extend over much of central Iran. The Dasht-e Lūt, running from the centre of the plateau towards the south, is covered largely with sand and rocks; and the Dasht-e Kavīr, running across the north of the central plateau, is covered mainly with salt. Both deserts are inhospitable and virtually uninhabited. In the winter and spring small streams flow into the Dasht-e Kavīr, creating small, seasonal lakes and permanent swamps. At other times of the year both deserts are extremely arid.

A

Rivers and Lakes

Most of Iran’s rivers are seasonal, flowing only during the part of the year when precipitation is heaviest. The country’s principal permanent rivers flow off the mountains on the slopes facing the Caspian Sea, the Persian Gulf, or the Gulf of Oman. The River Kārūn, flowing from the Zagros Mountains to the Shatt Al Arab at Khorramshahr, is the country’s main navigable river. Besides the Caspian Sea, Iran has few large lakes. Most shrink in size during the hot, dry summer and have a high salt content because they have no outlet to carry away the salt left when the water evaporates. The largest water body entirely within Iran is Lake Orūmīyeh, a salt lake in the north-west. It varies in area between 3,900 sq km and 6,000 sq km (1,506 sq mi and 2,317 sq mi) depending on the season.

B

Climate

Iran is divided climatically into four main regions: the extremely hot and humid coast along the Persian Gulf and the Gulf of Oman; the arid central plateau, with cold winters and baking summers; the Elburz and Zagros mountain chains, with cold winters, mild summers, and high precipitation; and the narrow Caspian Plain, a fertile, semi-tropical area, with a very warm and humid microclimate.

Winter brings very cold weather and snow to the west and interior of the Iranian plateau; low pressure over the warm waters of the Caspian Sea and the Persian Gulf brings mild sub-tropical weather to those regions. The Shamal wind blows from Pakistan from February to October, north-westerly through to the Tigris-Euphrates valley, while a “120-day” summer wind with a velocity of up to 40 km per hour (24 mph) scorches the Sistan region near the border with Pakistan.

Temperatures range from a high of 51° C (123° F) in summer in Khuzestan in the west to a low of -37° C (35° F) in winter in the north. The average temperatures for the months of January and July in Tehran are 2° C (36° F) and 29° C (85° F), respectively. The average temperatures during the same months in Ābādān are 12° C (54° F) and 36° C (97° F).

Precipitation also varies widely, from less than 50 mm (2 in) in the south-east to 1,950 mm (77 in) in the Caspian Sea coastal region. The annual average for the country is about 350 mm (14 in). Average annual precipitation in Tehran and Ābādān is 246 mm (10 in) and 204 mm (8 in) respectively.