Iran's interior plateaus are almost completely surrounded by mountains. The major sets of mountains are the Zagros Mountains, which cut across the country for more than 1,600 km (1,000 mi) from northwest to southeast. With the omission of the Khûzestân coastal plain, which extends from the northern reaches of the Persian Gulf, the Zagros Mountains take up all of western Iran. The central part of the range averages more than 340 km (210 mi) in width. Many summits of the Zagros exceed 4,000 m (12,000 ft) in elevation; the highest is Zard Kûh (4,547 m/14,918 ft). The peaks rising above 2,300 m (7,500 ft) capture considerable moisture, which spreads out down to the lower-lying basins as groundwater. These basins, ranging from about 1,200 to 1,500 m (4,000 to 5,000 ft) in elevation, contain fertile soil that traditionally has sustained various and demanding crop farming.

To the north of Iran, there is a steep, narrow mountain range called the Elburz Mountains, lines the entire southern coast of the Caspian Sea. This range extends more than 600 km (400 mi) in length and is about 100 km (about 60 mi) in width. The country's highest peak is Mount Damâvand (5,670 m/18,602 ft), which lies in the central part of the mountain range. The northern slopes of the range receive a huge amount of rainfall throughout the year and support forests. A productive coastal plain about 24 km (15 mi) in width lies between the Caspian Sea and the mountains. East of the Elburz Mountains is a series of parallel mountain ranges with elevations of 2,400 to 2,700 m (8,000 to 9,000 ft). These ranges are stuck in with many narrow, arable valleys. Low mountain ridges, referred to as the eastern highlands, run along Iran's eastern border.

Within this rocky area lies a series of basins known as the central plateaus. They include the Dasht-e Kavir, a huge salt- decorated desert in north central Iran; the Dasht-e Lût, a sand-and-pebble desert in the southeast; and several rich oases.

The mountains of Iran make up an active earthquake zone, and numerous small earthquakes occur each year. Major earthquakes cause great loss of life and property damage. During the 18th century earthquakes twice-leveled Tabrîz, the most important city in the northwest, kills at least 50,000 people on each time. Several cruel earthquakes resulting in 1,000 or more deaths occurred during the second half of the 20th century. In June 1990, the most shocking earthquake occurs in the fault zone where the Elburz and Zagros mountains intersect, and killed an estimated 40,000 people. Several of Iran's highest mountains are volcanic cones; only Mount Damâvand and Kûh-e Taftân in are active volcanoes, both are periodically emitting gases near their summits.