IRAN, officially Islamic Republic of Iran, has the area of 636,290 sq miles (1,648,000 sq km), SW Asia. The country's name was changed from Persia to Iran in 1935. Iran is bordered on the north by Armenia, Azerbaijan, Turkmenistan, and the Caspian Sea; on the east by Afghanistan and Pakistan; on the south by the Persian Gulf and the Gulf of Oman; and on the west by Turkey and Iraq. The Shatt al Arab forms part of the Iran-Iraq border. Tehran is the capital, largest city and the political, cultural, commercial, and industrial center of the nation. The country is divided into 30 provinces. In addition to Tehran, important cities include Isfahan, Shiraz, Mashhad, Tabriz, Rasht, Hamadan, Abadan, and Ahwaz. The land lies within the Alpine-Himalayan mountain system and is composed of a vast central plateau rimmed by mountain ranges and limited lowland regions. Iran is subject to numerous and often severe earthquakes and volcanic eruptions. The Iranian Plateau (alt. 4,000 ft/1,200 m), which extends beyond the low ranges of E Iran into Afghanistan, is a region of interior drainage. It consists of a number of arid basins of salt and sand, such as those of Dasht-e Kavir and Dasht-e Lut, and some marshlands, such as the area around Hamun-i-Helmand along the Afghanistan border. The plateau is surrounded by high folded and volcanic mountain chains including the Kopet Mts. in the northwest, the Elburz Mts. (rising to 18,934 ft/5,771 m at Mt. Damavand, Iran's highest point) in the north, and the complex Zagros Mts. in the west. Lake Urmia, the country's largest inland body of water, is in the Zagros of NW Iran. Narrow coastal plains are found along the shores of the Persian Gulf, Gulf of Oman, and the Caspian Sea; at the head of the Persian Gulf is the Iranian section of the Mesopotamian lowlands. Of the few perennial rivers in Iran, only the Karun in the west is navigable for large craft; other major rivers are the Karkheh and the Sefid Rud.
The official language of Iran is Persian (Farsi). The Persian spoken in Iran today developed in the first two centuries after the country's conversion to Islam in the mid-seventh century AD. The Persian spoken then, the language of the Sassanid was gradually modified by the introduction of many Arabic words; these retained their Arabic spelling, although their pronunciation adapted to Persian. Other languages are Turkic dialects, Turkish, Kurdish, Armenian, and Arabic. Among the educated classes, English and French are spoken.
Iran's climate is continental, with hot summers and cold, rainy winters; the mountain regions of the north and west have a subtropical climate. Temperature and precipitation vary with elevation, as winds bring heavy moisture from the Persian Gulf. The Caspian region receives over 40 in. (102 cm) of rain annually. Precipitation occurs mainly in the winter and decreases from northwest to southeast; much of the precipitation in the mountains is in the form of snow. Meltwater is vital for Iran's water supply. The central portion of the plateau and the southern coastal plain receive less than 5 in. (12.7 cm) of rain annually.
According to 2005 census Iran's population is estimated 68,018,000. The population is not homogeneous, although it has a Persian core that includes over half of the people. Azerbaijanis constitute almost a quarter of the population. The migrant ethnic groups of the mountains and highlands, including the Kurds, Lurs, Qashqai, and Bakhtiari, are of the least mixed descent of the original Iranians. In the Northern provinces, Turkic and Tatar influences are evident; Arab strains predominate in the southeast.
Islam entered the country in the 7th century AD and is now the official religion; about 90% of Iranians are Muslims of the Shiite sect. The remainder, mostly Kurds and Arabs, are Sunnis. Colonies of Zoroastrians remain at Yazd, Kerman, and other large towns. In addition to Armenian and Assyrian Christian sects, there are Jews, Protestants, and Roman Catholics.
agriculture contributes just over 20% to the gross national product and employs a third of the labor force. The main food-producing areas are in the Caspian region and in the valleys of the northwest. Wheat, the most important crop, is grown mainly in the west and northwest; rice is the major crop in the Caspian region. Barley, corn, cotton, sugar beets, tea, hemp, tobacco, fruits (including citrus), nuts, and dates are also grown, and livestock is raised. Illicit cultivation of the opium poppy is fairly common. The construction of multipurpose dams and reservoirs along the rivers in the Zagros and Elburz mts. has increased the amount of water available for irrigation. The northern slopes of the Elburz Mts. are heavily wooded, and forestry products are economically important. In the rivers entering the Caspian Sea are salmon, carp, trout, and pike; sturgeon are abundant in the Caspian Sea. Petroleum (discovered in 1908 in Khuzestan province) and natural gas are by far the most important of the variety of natural resources found in Iran. The chief oil fields are found in the central and southwestern parts of the Zagros Mts. in W Iran. Oil also is found in N Iran and in the South in offshore waters of the Persian Gulf. Domestic oil and gas, along with hydroelectric power facilities, provide the country with power. Iran is a member of the Organization of Petroleum Exporting Countries (OPEC). Besides crude and refined petroleum, Iran's chief exports are carpets, fruits, nuts, hides, and iron and steel.