Geology Condition

Iran is located between two major depressions, the Caspian Sea to the north and the Persian Gulf to the south. A series of mountains rising steeply from these depressions, along with other isolated mountain chains, form a high outer rim that encloses the interior basin.

This configuration provides Iran with an overall bowl-shaped topography that characterizes the country’s general physical appearance. The interior basin is known as the Iranian Plateau. According to geologists, the plateau is an ancient former seabed that took its present shape during the Quaternary period about 200,000 years ago. It was formed and shaped by the uplifting and folding effects of three giant plates pressing against each other.

The interacting plates are the Arabian Plate, the Eurasian Plate, and the Indian Plate. The continuous process of squeezing and pressing resulted in a considerable folding at the edges, and some folding in the interior, which eventually formed Iran’s present mountain ranges.

The continuing geologic process of uplifting and folding is also responsible for earthquakes—subterranean shifts in the earth that take place near the numerous fault zones formed by the movement of the plates. About 90 percent of Iran falls within an active seismic (earthquake-prone) zone. Most of the country is subject to the tremors and the devastation that they can cause. On June 22, 2002, a major earthquake hit the northwestern region of Iran, causing significant damage and casualties to small mountain towns and villages in the area.

Other major earthquakes during recent decades have claimed the lives of many Iranian people. For example, a 1997 earthquake in eastern Iran with a magnitude of 7.1 on the Richter Scale killed 2,000 and destroyed 200 villages. Another quake, measuring 7.7, occurred in 1978 in the eastern province of Khorasan. It killed 25,000 people and completely destroyed the ancient city of Tabas along with a large number of villages. The cheaply built adobe (mud-brick) buildings are the main reason for the vast destruction and high death tolls.