A series of massive, heavily eroded mountain ranges surround Iran’s
high interior basin. Most of the country is above 1,500 feet, and one-sixth of it is over 6,500 feet high. In the north, a 400-mile strip along the Caspian Sea between 10 to 70 miles wide falls sharply from the 10,000-feet summit to 90 feet below sea level. In the south, the land drops from a 2,000-feet plateau to the Persian Gulf and the Gulf of Oman.
The arid interior plateau, which extends into Central Asia, is interrupted by two small mountain ranges. In the intermediate steppe region, thorny shrubs form the ground cover. Parts of this desert region, known as dasht, are covered by loose stones and sand, which gradually merge with fertile soil on the hillsides. Where the ground can hold fresh water, oases mark ancient caravan routes. The vast deserts of Iran stretch across the plateau from the northwest, for a distance of about 400 miles toward the southeast and beyond the frontier. Approximately one-sixth of the total area of Iran is barren desert.
The Zagros mountain range stretches from the northwest border with the Republic of Armenia to the Persian Gulf, and then eastward into Baluchistan. . Willow, poplar, and plane trees grow in the ravines, as do many species of creepers. The Zagros are drained from the west by streams that cut deep, narrow gorges and continue on to water fertile valleys.
The Persian Gulf and the surrounding countries produce approximately 31% of the world’s total oil production and have 63% of the world’s proven reserves. In the Caspian coastal region, where the vegetation is subtropical, is Iran’s forested region, with trees like oak, beech, linden, elm, walnut, ash, as well as a few broad-leafed evergreens. Thorny shrubs and fern also abound.
Iran is mostly arid or semiarid, with a subtropical climate along the Caspian coast. In the summer, temperatures vary from a high of 123° F (50o C) in Khuzistan at the head of the Persian Gulf to a low of 35° F (1o C) in Azerbaijan in the northwest. Precipitation also varies greatly, ranging from less than two inches in the southeast to about 78 inches in the Caspian region.