floor, mostly along the central fault. A number of craters with a diameter of 10–100 m formed outside of the main cone, mainly in its northern part. They include Girigantepe (2433 m), Arizintepe (2445 m), Kayalitepe (2311 m), Mezarliktepe (2409 m), Atlitepe (2281 m), Amis (2166 m), Kevriağa (2087 m), Avuştepe and Sivritepe, which is the highest point of Nemrut. Basaltic lava of these craters are the youngest volcanic rocks within Nemrut. The last eruption took place on 13 April 1692. Since then only bursts of steam were observed at the bottom of the caldera, indicating fumarolic activity. Summary of eruptions Historical role Besides the legendary relationship of the volcano with King Nimrod, in 1990s scientists discovered that Nemrut played an important role in the life of the first civilizations. Despite the abundance of obsidian sources in Anatolia and Iran, Nemrut was the main source of obsidian – the most important material of the Stone Age – for all settlements in Mesopotamia and the settlements of the Mesolithic era around the Dead Sea. The analysis of obsidian products revealed that the population of those areas used obsidian from only two sources: Nemrut and the nearby dormant volcano Bingöl. An ancient center of obsidian processing and trade was found at Lake Van, which was part of one of the earliest trade routes. Two eruptions of Nemrut were probably witnessed by people of Urartu, an ancient state located in the eastern Turkey. These eruptions occurred c. 787 BC (period of King Menua) and c. 657 BC (period of King Rusa II), and the latter eruption might cause the sudden disappearance of the city Uaiais located 30 km east of Süphan. Present state Volcanic activity In the 1980s, Japanese volcanologists studied the evolution of gases inside the caldera of Nemrut. They found that the ratio of helium isotopes 3He/4He is 1.06, which indicates volcanic activity (most of the measured helium evolved from the mantle). More recent studies have confirmed these findings. The seismic activity in the region is high – in recent years there have been several earthquakes directly related to the Nemrut fault. Significant seismic events of the last 150 years that occurred within 30 km of Nemrut include the earthquakes of 18 May 1881 (magnitude 6.7), 29 March 1907 (5), 27 January 1913 (5), 14 February 1915 (6), and 3 November 1997 (5). There is evidence that the nature of volcanism