Volcano in Turkey
Mount Erciyes () is an inactive volcano in Kayseri Province, Turkey. It is a large stratovolcano surrounded by many monogenetic vents and lava domes, and one maar. The bulk of the volcano is formed by lava flows of andesitic and dacitic composition. At some time in the past, part of the summit collapsed towards the east.
The volcano began to form in the Miocene. At first, a volcano farther east named formed from lava flows. Then, again to the east, large explosive eruptions formed a caldera. During the Pleistocene, Mount Erciyes proper grew inside the caldera together with a group of lava domes. Lateral eruptions of Erciyes may have generated ash layers in the Black Sea and the Mediterranean during the early Holocene.
The last eruptions occurred during the early Holocene and may have deposited ash as far away as Palestine; the occurrence of historical volcanism is uncertain. Future eruptions of Erciyes may endanger the nearby cities to the north. The volcano was glaciated during the Pleistocene. One regular glacier still exists, but is receding.
Etymology.
"Erciyes" is the adoption into Turkish of the Greek name "Argaios" (Greek: Ἀργαῖος). The Latinized form is "Argaeus"; a rarely encountered alternative latinization was "Argaeas mons", "Argeas mons." The Greek name has the meaning of "bright" or "white"; as applied to the mountain, it may have been eponymous of Argaeus I (678 – 640BC), king of Macedon and founder of the Argead dynasty.
The Turkish name was historically spelled "Erciyas", and it was changed to "Erciyes" to conform with vowel harmony in the 1940s–1960s. Mons Argaeus on the Moon was named for Argaeus. The "Mount Harhara" of Bronze Age and Iron Age inscriptions in Anatolia may be Erciyes.
Geology and geomorphology.
Erciyes lies in the Kayseri Province of Turkey. The city of Kayseri lies - north of Erciyes volcano; some lava domes generated by the volcano are within the urban limits. Other towns in the region are Talas and Hacilar, also north of Erciyes but closer to the volcano ( and , respectively), Develi, located south, and İncesu, located west and southwest of the volcano. The mountain is about half an hour from Kayseri but access to the summit area is difficult. Climbers in antiquity reported that both the Black Sea and the Mediterranean could be seen from the summit.
Regional.
Erciyes Dagi and Hasan Dagi are both large stratovolcanoes that lie in Central Anatolia, on the Anatolian Plate. This microplate is part of the collision zone between the Eurasian Plate, the African Plate, and the Arabian Plate that forms the Alpide Belt. This convergence commenced in the Miocene and formed the Anatolian block, with two oceans that existed between these three plates in the Eocene disappearing through subduction. During the late Miocene, the Neo-Tethys ocean disappeared, and Africa and Eurasia collided. Later, the Red Sea and the Gulf of Suez separated the Arabian Plate from the African Plate, causing the former to collide with Eurasia and forming the Bitlis–Zagros Belt. The Anatolian block was pushed westward between the North Anatolian and East Anatolian faults, and it is still moving today.
In central Anatolia, volcanism commenced in the Miocene. After an effusive phase and the eruption of large ignimbrite sheets, volcanoes developed, including stratovolcanoes such as Erciyes Dagi and Hasan Dagi on the one hand and monogenetic volcanoes and maars on the other hand. The tectonic environment has been compared with the Basin and Range Province. The Central Anatolian Volcanic Province, of which Erciyes is a part, covers a surface area of . The Cappadocian volcanic plateau comprises ignimbrites that are up to thick. The youngest K–Ar dates obtained on these centres are 60,000 ± 20,000 years ago for the Kizirtepe monogenetic centres and 20,000 ± 10,000 for Hasan. Volcanic activity in the Acıgöl-Nevşehir system has been fission track dated at 15,500 ± 2,500 years ago.
Major faults such as the North Anatolian Fault, which were generated by the convergence, are also active. Some of these faults form the edges of the Erciyes pull-apart basin, a tectonic depression up to deep that is split by this volcano into the and basins, both of which nevertheless are part of the same system. These margin faults have been the source of earthquakes during historical times, resulting in damage to cities in the region, and ongoing extension of this crustal domain is the probable reason for volcanism at Erciyes.
Local.
Erciyes Dagi is a large stratovolcano, reaching a height of , or , making it the highest mountain and most voluminous volcano of Central Anatolia. It rises about above the basin and above the floor of the Erciyes pull-apart basin. 
The volcano is large, it covers a surface area of or . It developed over a broad shield, and dacitic domes and flows form the bulk of the volcano's exposed units, including the summit area, where several lava flows have been identified. Lava flows of Erciyes extend both from the summit and from lateral vents. A debris avalanche extending east-northeast from Erciyes was formed by the collapse of the summit, creating a wide horseshoe-shaped scar that forms the upper segment of the valley. The debris avalanche deposit reaches a distance of from the summit and has a hummocky appearance. The volcano overall has an eroded appearance.
Two major valleys extend to the summit, the northwesterly Aksu Valley and the easterly valley. The minor valleys of lie north, south, and southwest of the summit. The Aksu valley contains sizable moraines left by the Pleistocene glaciation that are up to high, wide and long. A glacial outwash plain formed at the valley foot and was partly buried by lavas. Moraines and outwash plains are heavily eroded.
Andesite and basaltic andesites are exposed on the western, southern, and eastern sides of the volcano; on the eastern side they form the centre with a height of . This centre is mostly formed by lava flows. On the western side, andesitic lava flows reach the basin. The huge middle Pleistocene Aliboran lava flow descended the western slopes and blocked the Incesu valley, forming Aliboran Lake in the basin. The lake was fed by glacial meltwater from Erciyes and later overflowed the lava flow at several sites, the most important of which is . This overflow was not continuous; phases of lower lake levels caused it to dry up. Today, the basin contains wetlands that are protected under the Ramsar Convention and are a major nesting site for migratory birds.
Endogenous domes extend from Erciyes, and 184, 210, or 64 individual centres dot its flanks. The domes have diameters of , and formed along radial dykes. A number of such domes and centres formed on the rim of the wide caldera in which Erciyes sits and which formed during the Valibaba Tepe eruption. This caldera may originally have had a volume of . Clockwise from north, these volcanic centres are , , , , , , , , , , , and . About half of these centres are at distances of about from Erciyes, and most of them can be found on the northern slopes. Of these centres, wide and deep lies northwest of Erciyes. It formed within Quaternary andesite lava flows; its formation was probably favoured by a shallow aquifer and was accompanied by strong phreatomagmatic explosions. The formation of this maar was accompanied by the release of tephra, which reached a distance of . Additional basaltic vents are , , , and .
From the more recent volcanic phases, and lava domes lie on the southern and northern slope of Erciyes, respectively. Both domes are formed of rhyodacite and accompanied by pyroclastic deposits. covers a surface area of and reaches a height of . The blocky dome flowed down the slopes southwards over . on the north-northwestern flank stratigraphically belongs to the same unit as . This dome flowed for a distance of about .
The volcano lies in a tectonic depression. It is cut by the fault, which together with the fault border this basin. Other faults converge on the volcano or pass through its outer slopes. Aeromagnetic investigation of the region has evidenced the existence of a magnetic anomaly associated with Erciyes, which is probably caused by the volcanism.
Petrology.
Erciyes Dagi has erupted basalt, basaltic andesite, andesite, dacite, rhyodacite, and rhyolite. The rocks are chiefly andesite with smaller amounts of dacite; dacites appear to dominate in the summit region, however. The volcano is dominated by calc-alkaline rocks; one basalt with tholeiitic to intermediary affinity was erupted 1.7million years ago; volcanic activity at first was tholeiitic and later became calc-alkaline. Monogenetic volcanoes in the region also erupted basalt, but this basalt is clearly different from the Erciyes basalt.
Minerals contained in Erciyes rocks include clinopyroxene, ilmenite, orthopyroxene, plagioclase, and titanomagnetite. Samples taken from the summit also contain amphibole, apatite, biotite, feldspar, quartz, and zircon. The mineral yazganite was first described from samples obtained on Mount Erciyes, and its chemical formula is NaFe23·H2O.
The dacites taken from the summit display a noticeable variability in their composition and texture, with their temperatures at formation varying between .
The andesites and dacites may have formed from basaltic magma by fractional crystallization involving amphibole, based on elemental composition data. Further, crustal materials were included into the magma. Tholeiitic and calc-alkaline magmas have different elemental compositions and probably formed from separate sources; tholeiitic magmas may have formed from partial melting of the mantle, while the calc-alkaline magmas formed from crustal assimilation in these magmas. Overall, the magma originated in the asthenospheric mantle; lithospheric components may have contributed, however.
Volcanism appears to be associated with crustal extension at Erciyes. Mantle metasomatism from a subducting slab, on the other hand, may or may not have played a major role, and the slab itself did not reach down below Central Anatolia, meaning that subduction probably is not responsible for Central Anatolian volcanism.
Climate and biology.
The climate of the region is influenced by topography, with the Taurus and Kaçkar Mountains blocking the entry of moisture into Anatolia. Summers are dry and hot and winters snowy and cold; in Kayseri, summer temperatures are about and winter temperature about . Precipitation at Kayseri falls mostly in autumn, winter, and spring and amounts to per year. In Develi, south of Erciyes, maximum temperatures are about and minimum temperatures . Estimated temperatures at altitude are about , and precipitation per year. Groundwater under Kayseri is recharged from the mountain. During the last glacial maximum, precipitation may have been double that of present-day.
Four vegetation belts surround the mountain: a boreal belt, a subalpine, an alpine, and a subnival belt. The boreal belt extends between while the subalpine belt goes from elevation and the alpine from . Species found in the vegetation belts are different from these found in the equivalent areas of Western European mountains.
The flora of Erciyes is diverse. A number of endemic plant species have been identified, including "Astragalus argaeus", "Astragalus stenosemioides", "Asyneuma trichostegium", "Bellardiochloa argaea", "Dianthus crinitus argaeus", "Festuca cratericola", "Festuca woronowii argaea", "Hieracium argaeum", "Onobrychis argaea", and "Vicia canescens argaea". The plant "Silene erciyesdaghensis" was discovered on Erciyes and named after it. The geographer Strabo claimed that, in antiquity, the volcano was forested. A number of endemic and relic animal species can also be found at Erciyes, as well as a rich lichen flora. Grazing, settlements, and tourism have altered the natural vegetation of the mountain.
Glaciation.
The volcano was glaciated during the Pleistocene, during which about three stages of glaciation occurred. Aretes, cirques, horns, and moraines from these glaciations can be found on the volcano, with each of the five valleys that extend from the summit hosting glaciers. In the Aksu valley, these extended down to an altitude of . Glaciers reached lengths of ; with the Aksu valley glacier reaching a length of and the glacier of . The snowline was lower during the last glacial maximum, probably due to a wetter climate. Chlorine-36 dating has yielded ages corresponding to the last glacial maximum and late glacial for the principal moraines in Aksu valley. A late Holocene glacial advance extended down to ; dating of these moraines has yielded ages of 1,200 ± 300 years ago. In the valley, the lowermost moraines are found at an altitude of , with the late Holocene advance forming moraines at an altitude of . The maximum extent of glaciers on Erciyes occurred 21,300 ± 900 years ago, when glaciers reached lengths of .