Zagros Mountains

The Zagros Mountains from space, September 1992 ^[1]

The Zagros (Persian: رشته كوههاى زاگرس), (Arabic: جبال زاجروس‎), (Sorani Kurdish: Zagros - زاگرۆس) are Iran's and Iraq's largest mountain range. They have a total length of 1 500 km from western Iran, on the border with Iraq to the southern parts of the Persian Gulf. The mountain range ends at the Straits of Hormuz. The highest points in the Zagros Mountains are Zard Kuh (4 548 m) and Mt. Dena (4 359 m). The Hazaran massif in the Kerman province forms an eastern outlier of the range, the Jebal Barez reaching into Sistan.

The Zagros Mountains were formed by collision of two tectonic plates — the Eurasian and Arabian Plates. Recent GPS measurements in Iran^[2] have shown that this collision is still active and the resulting deformation is distributed non-uniformly in the country, mainly taken up in the major mountain belts like Alborz and Zagros. A relatively dense GPS network which covered the Zagros in the Iranian part ^[3]also proves a high rate of deformation within the Zagros. The GPS results show that the currnet rate of shortening in SE Zagros is ~10 mm/yr and ~5mm/yr in the NW Zagros. The NS strike-slip Kazerun fault divides the Zagros into two distinct zones of deformation. The GPS results also show different shortening directions along the belt, i.e. normal shortening in the South-East and oblique shortening in the NW Zagros. The sedimentary cover in the SE Zagros is deforming above a layer of rock salt (acting as a ductile decollement with a low basal friction) whereas in the NW Zagros the salt layer is missing or is very thin. This different basal friction partly made different topographies in either sides of Kazerun fault. Higher topography and narrower zone of deformation in the NW Zagros is observed whereas in the SE, deoformation was spreaded more and wider zone of deformation with lower topography was formed^[4]. Stresses induced in the Earth's crust by the collision caused extensive folding of the preexisting layered sedimentary rocks. Subsequent erosion removed softer rocks, such as mudstone (rock formed by consolidated mud) and siltstone (a slightly coarser-grained mudstone) while leaving harder rocks, such as limestone (calcium-rich rock consisting of the remains of marine organisms) and dolomite (rocks similar to limestone containing calcium and magnesium). This differential erosion formed the linear ridges of the Zagros Mountains.

The depositional environment and tectonic history of the rocks were conducive to the formation and trapping of petroleum, and the Zagros region is an important part of Persian Gulf oil production.

Salt domes and salt glaciers are a common feature of the Zagros Mountains. Salt domes are an important target for oil exploration, as the impermeable salt frequently traps petroleum beneath other rock layers.

Etymology

The name Zagros is derived from the Zagarthians/Sagarthians--and Indo-European, Iranic immigrants from Europe who once inhabited the mountains, from the shores of Lake Van to the coasts of Makran. The Zangana and Chigini tribes of the Kurds are the remnants of these ancient Sagarthians. Other explanations deriving the name from Greek Zagreus, meaning stormy, or the name Za-G'R' means 'great mountain' in the Avestan language, are invalid.These mountains are nery hard to locate on a tiny map.

Type and age of rock

The mountains are divided into many parallel sub-ranges (up to 10, or 250 km wide), and have the same age as the Alps. Iran's main oilfields lie in the western central foothills of the Zagros mountain range. The southern ranges of the Fars Province have somewhat lower summits, reaching 4000 metres. They contain some limestone rocks showing abundant marine fossils.

The Kuhrud Mountains form one of the parallel ranges at a distance of approx. 300 km to the east. The area between these two impressive mountain chains is home to a dense human population that lives in the intermediate valleys which are quite high in altitude with a temperate climate. Their rivers, which eventually reach salt lakes, create fertile environments for agriculture and commerce.

Zagros in history

Signs of early agriculture date back as far as 9000 BCE to the foothills of the Zagros Mountains^[5], in cities later named Anshan and Susa. Jarmo is one archaeological site in this area. Shanidar, where the ancient skeletal remains of Neanderthals have been found, is another.

Some of the earliest evidence of production has been discovered in the Zagros Mountains; both the settlements of Hajji Firuz Tepe and Godin Tepe have given evidence of wine storage dating between 3500 and 5400 BC.^[6]

During early ancient times, the Zagros was the home of peoples such as the Kassites, Guti, and Mitanni, who periodically invaded the Sumerian and/or Akkadian cities of Mesopotamia. The mountains create a geographic barrier between the flatlands of Mesopotamia which is in Iraq and the Iranian plateau.

References

See also

• Taurus Mountains
• Alborz Mountains

External links

• Zagros, Photos from Iran, Livius.
• The genus Dionysia
• Iran, Timeline of Art History
• Mesopotamia 9000 - 500 B.C.
• Major Peaks of the Zagros Mountains