A series of massive, heavily eroded mountain ranges surround Iran's high interior basin. Most of the country is above 1,500 feet, one-sixth of it over 6,500 high.
In sharp contrast are the coastal regions outside the mountain ring. In the north, the 400-mile strip along the Caspian Sea, never more than 70 miles wide and frequently narrowing to 10, falls sharply from the 10,000-foot summit to 90 feet below sea level.
In the south, the land drops away from a 2,000-foot plateau, backed by a rugged escarpment three times as high, to meet the Persian Gulf and the Gulf of Oman.
Mountains The Zagros range stretches from the border with the Republic of Armenia in the north-west to the Persian Gulf, and then eastward into Baluchistan.
As it moves southward, it broadens into a 125-mile-wide band of parallel, alternating mountains lying plains of Mesopotamia and the great central plateau of between Iran. It is drained on the west by streams that cut deep, narrow gorges and water fertile valleys.
The land is extremely hard, difficult to access, and populated largely by pastoral nomads. The Alborz mountain range, narrower than the Zagros but equally forbidding, runs along the Zagros but equally forbidding, runs along the southern shore of the Caspian to meet the border ranges of Khorasan to the east.
The highest of its volcanic peaks is 18,600-foot, snow-covered Mt. Damavand. On the border of Afghanistan, the mountains fall away, to be replaced by barren sand dunes.
The arid interior plateau, which extends into Central Asia, is cut by two smaller mountain ranges. Parts of this desert region, known as Dasht, are covered by loose stones and sand, gradually merging into the fertile soil on the hillsides.
Where fresh water can be held, oases have existed from time immemorial, marking the ancient caravan routes.
The most remarkable feature of the plateau is a salt waste 200 miles long and half as wide, knows as the Kavir (deserts).
It remains unexplored, since its treacherous crust has been formed by large, sharp-edged salt masses which cover mud. Cut by deep ravines, it is virtually impenetrable.
LAKES AND SEAS
The Caspian Sea, which is the largest landlocked body of water in the world (424,240 sq. km.), lies some 85 feet below the sea level.
It is comparatively shallow, and for some centuries has been slowly shrinking in size.
Its salt content is considerably less than that of the oceans and though it abounds with fish, its shelly coasts do not offer any good natural harbors, and sudden and violent storms make it dangerous for small boats.
The important ports on the Caspian coast are Bandar Anzali, Noshahr, and Bandar Turkman. Other Lakes Along the frontier between Iran and Afghanistan there are several marshy lakes which expand and contract according to the season of the year.
The largest of these, the Seestan (Hamun-Sabari), in the north of the Seestan & Baluchistan province, is alive with wildfowl.
Real freshwater lakes are exceedingly rare in Iran. There probably are no more than 10 lakes in the whole country, most of them brackish and small in size.
The largest are: Lake Urmiya (area: 3,900-6,000 sq. km. depending on season) in Western Azerbaijan, Namak (1,806 sq. km.) in the Central province, Bakhtegan (750 sq. km.) in Fars province, Tasht (442 sq. km.) in Fars province, Moharloo (208 sq. km.) in Fars province, Howz Soltan (106.5 sq. km.) in Central province.
The Persian Gulf is the shallow marginal part of the Indian Ocean that lies between the Arabian Peninsula and south-east Iran. The sea has an area of 240,000 square kilometers.
Its length is 990 kilometres, and its width varies from a maximum of 338 kilometres to a minimum of 55 kilometres in the Strait of Hormuz, it is bordered on the north, north-east, and east by Iran, on the north-west by Iraq and Kuwait, on the west and south-west by Saudi Arabia, Bahrain and Qatar, and on the south and south-east by the United Arab Emirates and partly Oman. The term the Persian Gulf is often used to refer not only proper to the Persian Gulf but also to its outlets, the Strait of Hormuz and the Gulf of Oman, which opens into the Arabian Sea.
The most important islands of the Persian Gulf on the Iranian side are Minoo, Kharg, Sheikh Saas, Sheikh Sho'ayb, Hendurabi, Kish, Farur, Sirri, Abu Mussa, the Greater and Lesser Tunb, Qeshm, Hengam, Larak, Farsi, Hormuz, Lavan.
The notable ports on the Persian Gulf coast are Abadan, Khorramshahr, Bandar Iman Khomeini, Mahshahr, Deilam, Gonaveh, Rig, Bushehr, Bandar Lengeh, Bandar Abbas. The Iranian shore is mountainous, and there are often cliffs; elsewhere a narrow coastal plain with beaches, intertidal flats, and small estuaries borders the gulf. The coastal plain widens north of Bushehr on the eastern shore of the gulf and passes into the broad deltaic plain of the Tigris, Euphrates and Karun rivers.
It is noticeably asymmetrical in profile, with the deepest water occurring along the Iranian coast and a broad shallow area, which is usually less than 120 feet deep, along with the Arabian coast.
There are some ephemeral streams on the Iranian coast south of Bushehr, but virtually no fresh water flows into the gulf on its south-west side. Large quantities of fine dust are, however, blown into the sea by predominant north-west winds from the desert areas of the surrounding lands.
The deeper parts of the Persian Gulf adjacent to the Iranian coast and they are around the Tigris-Euphrates Delta are mainly floored with grey-green muds rich in calcium carbonate. The Persian Gulf has a notoriously bad climate. Temperatures are high, though winters may be quite cool in the north-western extremities.
The sparse rainfall occurs mainly as sharp downpours between November and April and is heavier in the north-east, Humidity is high.
The little cloud cover is more prevalent in winter than in summer.
Thunderstorms and fog are rare, but dust storms and haze occur frequently in summer.
Until the discovery of oil in Iran in 1908, the Persian Gulf area was important mainly for fishing, pearling, the building of dhows, sailcloth making, camel breeding, reed mat making, date cultivating, and the production of other minor products, such as red ochre from the islands in the south.
Today these traditional industries have declined, and the economy of the region is dominated by the production of oil.
The Persian Gulf and the surrounding countries produce approximately 31 percent of the world's total oil production and have 63 percent of the world's proven reserves.
The Persian Gulf area will probably remain and important source of world oil for a long period.