| Mount Hasan | |
|---|---|
 View of Mount Hasan | |
| Highest point | |
| Elevation | 3,268 m (10,722 ft)[1] |
| Prominence | 1,922 m (6,306 ft)[1] |
| Listing | Ultra |
| Coordinates | 38°07′39″N34°10′00″E / 38.12750°N 34.16667°E /38.12750; 34.16667[1] |
| Geography | |
  Mount Hasan Turkey | |
| Location | Aksaray Province,Turkey |
| Geology | |
| Mountain type | Stratovolcano |
| Last eruption | 6200 BC |
Mount Hasan (Turkish:Hasan Dağı) is avolcano inAnatolia,Turkey. It has two summits, the 3,069 metres (10,069 ft) high eastern Small Hasan Dagi and the 3,253 metres (10,673 ft) high Big Hasan Dagi, and rises about 1 kilometre (0.62 mi) above the surrounding terrain. It consists of various volcanic deposits, including severalcalderas, and its activity has been related to the presence of severalfaults in the area and to regional tectonics.
Activity began in theMiocene and continued into theHolocene; a mural found in thearcheological site ofÇatalhöyük has been controversially interpreted as showing a volcanic eruption or even a primitivemap. It was the second mountain from the south in theByzantine beacon system used to warn the Byzantine capital ofConstantinople of incursions during theArab–Byzantine wars.
The modern name of Mount Hasan is widely accepted to be in dedication to Ebu'l-Gazi (El-Hasan), brother ofEbu'l-Kasım during the reign of theAnatolian Seljuks. It is hypothesized that Mount Hasan’s name was “Argeos” or “Argaios”, but this name belongs toMount Erciyes. Another hypothesis is that it was simply calledÁrgos, (Ancient Greek: Ἄργος) as well as Argeiopolis Mons. TheHittites called itAthar.[2]
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Mount Hasan lies in the Anatolian plateau, between theTaurus Range and thePontic Mountains,[3] and its andMount Erciyes's silhouettes dominate the landscape[4] and rise high above the surrounding terrain.[5] The city ofAksaray lies 30–40 kilometres (19–25 mi) northwest from Mount Hasan,[6] while the settlements ofHelvadere,Uluören,Dikmen andTaşpınar lie clockwise from north to northwest around the volcano.[7] In addition, there are seasonal settlements on the volcano which are associated with summerpastures.[8] The volcano has been prospected as a potential source forgeothermal power.[9]
Mount Hasan is part of a larger volcanic province in Central Anatolia[10] known as the Central Anatolian orCappadocian Volcanic Province.,[11] which includesignimbrites,monogeneticvolcanic fields andstratovolcanoes such asMount Erciyes, Mount Hasan,[10]Karacadağ[12][10][13] and Melendiz Dağ[10] with an area of about 20,000 square kilometres (7,700 sq mi)[14]-25,000 square kilometres (9,700 sq mi).[15] Volcanism took place during thePlio-Pleistocene and into theQuaternary.[10]
The volcano has two summits, the 3,069 metres (10,069 ft) high eastern Small Hasan Dagi/Küçük Hasandağ and the 3,253 metres (10,673 ft) high Big Hasan Dagi/Büyük Hasandağ, and consist oflava domes andlava flows.[16] Big Hasan Dagi has two nestedcraters with an 800 metres (2,600 ft) wide and 200 metres (660 ft) high inner cone that is the source of alava flow.[16] Whether they are located within acaldera is unclear; rather than one large caldera encompassing the entire complex,[17] there may be a smaller one underlying Mount Hasan specifically.[18] There isperiglacial activity on the summit,[19] and fossilrock glaciers are found on the volcano.[20] The volcano as a whole rises almost 1 kilometre (0.62 mi) around the surrounding terrain[21] and covers an area of 760 square kilometres (290 sq mi) with 354 cubic kilometres (85 cu mi) of rocks.[22] The terrain of Mount Hasan is formed byphreatomagmaticbreccias,ignimbrites,lahar deposits,lava domes,lava flows andpyroclastic flow deposits.[7] The pyroclastic flow deposits occur in the form of fans or valley flows, when they were channelled by topography.[23] The northern flanks also feature two[24] debris avalanche deposits with hummocky surfaces.[25] Two calderas, theUlukışla caldera on the eastern and theKeçikalesi on the southwestern flank, adorn the volcano.[18] The volcanics of Mount Hasan have been subdivided into a "hot flow" unit, a "Mt. Hasan ashes" unit and into a lava unit.[26]
Cinder cones,maars and accompanying lava flows also occur around Mount Hasan, they are part of abasaltic volcano family[27] that formsparasitic vents.[23] These include theYıpraktepe cone/maar[28] and a lava flow field atKarataş which covers an area of 60 square kilometres (23 sq mi) and was produced byfissure vents.[29] Many of the cones around Mount Hasan have been grouped as the Hasandağ-Karacadağ volcanic field.[30]
As a consequence of thesubduction and eventual closure of theNeo-Tethys[15] and continental collision betweenArabia-Africa andEurasia,[31]Anatolia moves westward at a rate of 21 millimetres per year (0.83 in/year)[32] between theNorth Anatolian Fault and theEast Anatolian Fault. This movement and the resulting tectonic deformation of Anatolia are responsible for volcanism in Central Anatolia,[10] together with the subduction of theCyprus Plate.[32] Volcanism has been ongoing for the past 10 million years;[33] it is defined as "post-collisional".[34] Further, volcanism at Mount Hasan has been related to the Tuz Gölü Fault[35] and its intersection with the Karaman-Aksaray faults;[36] the former of these is one of two major fault systems in Central Anatolia which influence volcanism there,[33] and volcanic products of Mount Hasan have been deformed by the fault.[37] The Hasandag fault branches off the Karaman-Aksaray fault and cuts between the two summits of Mount Hasan.[38] It and the Karacaören fault influence the hydrothermal system of the volcano.[39]
The westerly Mount Hasan, centralKeçiboyduran[40] and easterlyMelendiz Dağ[41] form the Niğde Volcanic Complex,[42] amountain range, which is surrounded by plains and whose summits reach heights of over 3,000 metres (9,800 ft). Of these mountains,Melendiz Dağ is more heavily eroded compared to the steep cones of Hasan[43] and likeKeçiboyduran is of earlyPliocene age.[44] This alignment is congruent with the tectonic patterns of Anatolia, where the collision between Africa and Eurasia follows the same trend.[45] It and to some degree Mount Hasan are also surrounded by a large depression,[46] and the volcanoes of this alignment are separated by faults.[47] Additionally, Mount Hasan forms a volcaniclineament withKaradağ and theKarapınar Field.[13]
Thebasement in Central Anatolia is formed by magmatic,metamorphic andophiolitic rocks, the former of which are ofPaleozoic toMesozoic age;[33] it crops out at scattered sites and in the Kirshehir and Nigde massifs.[37] The surface however consists mainly ofTertiary volcanic rocks,[48] which are formed both by numerousignimbrites,[17]volcaniclastic material and individual volcanoes.[37] Central Anatolia has undergone uplift, for which several mechanisms have been proposed.[15]
Mount Hasan has produced volcanic rocks with compositions ranging frombasalt torhyolite but the dominant components areandesite anddacite[49] which define an oldertholeiitic and a youngercalc-alkaline[50] or alkaline suite.[34] These rocks in turn includeamphibole,apatite,biotite,clinopyroxene,[51]garnet,[52]ilmenite,mica,[51]olivine,[53]orthopyroxene,plagioclase,[54]pyroxene[22] in the form ofaugite,bronzite,diopside,hypersthene andsalite,[55] andquartz.[54] The older volcanic stages have producedbasaltic andesite[56] while dacite appears only in the most recent stage.[53]Obsidian also occurs in the most recent stage[49] although it is not an important component[57] while most of the rocks areporphyritic.[51] The basaltic family includes bothbasaltic andesite andalkali basalts withaugite,clinopyroxene,garnet,hornblende,hypersthene,olivine,orthopyroxene,oxides andplagioclase.[52][58]
Magma mixing processes appear to be the most important mechanisms involved in the genesis of Mount Hasanmagmas,[59] which are derived from themantle with participation ofcrustal components.[60] Evidence offractional crystallization has been encountered in the most recent stage rocks[53] and more generally plays a role in the genesis of Hasan magmas[61] although it does not explain all of the compositional traits.[62] It appears that basaltic andesites formed through mixing, while fractional crystallization was more important for the genesis of other magmas.[63] Older volcanic stages also show evidence ofsubduction influence[64] while the more recent magmas are more indicative of intraplate processes,[65] the effects of crustal extension[66] and of the presence of water.[67] In general, various sources have been proposed for the magmas of the Central Anatolian province.[15] The magmatic system of Mount Hasan appears to be more active than that of Mount Erciyes.[68]
The magmas formed at different depths, with basalts originating at about 35–41 kilometres (22–25 mi) depth at the base of thecrust, while the other volcanic rocks have shallower sources.[69] The basaltic magmas would have ascended into a shallowmagma chamber at 3–4 kilometres (1.9–2.5 mi) depth, mobilizing its contents and thus giving rise to the more silicic magmas.[70] The magma formation processes were quick, with only days or weeks going from the formation of the magma and its eruption on the surface.[71]
Oak forests occur on Mount Hasan.[72] Annual precipitation is about 400 millimetres (16 in).[73] Between October/November and May, the mountain is frequently covered bysnow due to the common precipitation at that time and when it melts the water mostly infiltrates into the permeable rocks,[74] making the volcano a principal groundwater recharge area in the region.[75] Additionally, volcanics of Mount Hasan form a majoraquifer[76] and the Melendiz River passes north and northeast of the volcano.[40]
Mount Hasan has been active for the last 13 million years, with theKeçikalesi, Paleo-Hasan, Mesovolcano and Neovolcano stages during theMiocene, Miocene-Pliocene andQuaternary;[22] the older two stages might actually not be part of Mount Hasan at all.[66] Aside from thefelsic central vent volcanism, basaltic volcanism also took place at Mount Hasan throughout its activity;[16] this activity has been dated to 120,000, 65,000[77] and the most recent event 34,000 years ago.[50] This volcanism however is not part of the actual Mount Hasan system.[78] The main edifice has produced about 1–0.3 cubic kilometres (0.240–0.072 cu mi) of magma every millennium, more than at Erciyes.[79][80]
Keçikalesi is the oldest (13 million years) volcanic structure,[22] it is among the oldest volcanoes of the Central Anatolian volcanic province.[81] This volcano is a small sized volcano with acaldera which crops out on the southwestern side of Mount Hasan. It grew over sediments to a present-day elevation of 1,700 metres (5,600 ft); today it is eroded, partly buried by the younger Hasan volcanics[22] and disrupted bystrike-slip faulting. About 7 million years ago the Paleovolcano began to grow north ofKeçikalesi; it too is buried by more recent volcanics but part of its deposits crop out on the northwestern flank of Mount Hasan in the form of ignimbrites, lahars and lava flows.[54] The Paleovolcano also formed a caldera which produced the rhyolitic Dikmen-Taspinar Ignimbrites;[77] formerly the Cappadociantuffs were in general attributed to volcanism at Mount Hasan, Mount Erciyes andGöllü Dag.[82]
TheQuaternary activity gave rise to the Mesovolcano and Neovolcano, with the former centered between the two present-day summits. This volcano produced ignimbrites, lava domes and lava flows and eventually acaldera; it too has been dissected byfaulting which probably also influenced the development of the volcano[54] and its activity probably occurred between 1 and 0.15 million years ago.[83] Finally, the Neovolcano grew within the caldera, producing various kinds of deposits; these includelava domes with accompanyingpyroclastic flow deposits,breccia in the rim of the Mesovolcano caldera[54] that probably formed through the interaction of intrudingmagma with water in the caldera,[23] 700,000 years agorhyolitic flows and ignimbrites accompanied by the formation of another, 4 by 5 kilometres (2.5 mi × 3.1 mi) caldera, and finallyandesitic lava flows and lava domes which form the two main summits.[16] A majorPlinian to sub-Plinianpumice-forming eruption took place 417,200 ± 20,500 years ago, forming theBelbaşhanı Pumice[84] and deposited fallout over much of Central Anatolia.[85]
Small Mount Hasan is probably older as it is more heavily eroded while the morphology of Big Hasan Dagi is fresher[16] although its pyroclastic flow deposits are heavily incised. Dates of 33,000 and 29,000 years ago have been obtained on the summit domes[25] and ages of 66,000±7,000 years on the most recentmonogenetic volcano south of Mount Hasan.[86] Explosive eruptions took place 28,900 ± 1,500 and 13,500 ± 1,500 years ago.[87] Tephras found in theKonya plain[88] and in a lake of theTurkish Lakes Region have been attributed to Mount Hasan.[89] The debris flow from Mount Hasan occurred 150,000-100,000 years ago[90] and a number oflava flows were emplaced during the last 100,000 years.[91]
Eruptions occurred 8,970 ± 640,[25] 8,200, less than 6,000 years ago[54] and 0 ± 3,000 years ago; the first emplacedpumice on the summit, the penultimate of these formed a lava dome on the northern flank while the last formed a lava flow on Mount Hasan's western foot.[25][92] A shift inarcheological sites around Mount Hasan may be linked to the older eruptions.[93] There is no evidence of historical eruptions of the volcano.[42]
Hydrothermal activity also occurs at Mount Hasan,[94] withfumaroles and water vapour emissions on the summit.[95] The emission occurs along vents trending in a northeast-southwest direction, which are linked to a major regionalfault.[96] Rocks around these vents have been chemically altered.[97] Another field of fumaroles andhot springs is on the northwestern side of Hasan.[17]Magnetotelluric and other imaging techniques have found evidence of amagma chamber at 4–6 kilometres (2.5–3.7 mi) depth and of a magmatic body between 6–11.5 kilometres (3.7–7.1 mi).[17][98] A hydrothermal system may[99] or may not exist.[100] There have beenseismic swarms around Mount Hasan,[32] including one in 2020[101] next to acinder cone that was active 2000 years ago,[102] and there is evidence that fumarolic and seismic activity has increased during the 2020s.[42] Reportedly, there are frequent explosions within the volcano.[103]
Future activity at Hasan could impact neighbouring villages, and larger eruptions might disruptair traffic and tourism in Cappadocia.[84] As of 2022[update] the volcano is not monitored.[104]
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Amural discovered inÇatalhöyük has been interpreted as showing a volcanic eruption, commonly linked to Mount Hasan, and this mural has even been interpreted as being the oldest knownmap. The interpretation of the mural showing a volcanic eruption has been contested however[105] as an alternative interpretation is that the "volcano" shown in the mural is actually aleopard and the "village" a set of random geometric motifs.[106][21] The map interpretation is also contested.[105] The mural is depicted in theMuseum of Anatolian Civilizations inAnkara[16][107] and has been cited as the first man-madediagram.[108]
If the mural indeed shows an eruption, it probably occurred only a short time before the mural was drawn.Radiocarbon dating has yielded ages of about 7,400 - 6,600 yearsBCE for Çatalhöyük[105] andradiometric dating has produced evidence forexplosive eruptions during that time[109] and when the mural was made. The depicted activity resemblesStrombolian eruptions, and the event may not have been directly visible from Çatalhöyük.[110] The discovery of this mural has drawn attention to the volcano[111] and has led to efforts to date the eruptive activity of Mount Hasan.[112]
Mount Hasan was used as a source forObsidian.[113][114] TheByzantine city ofMokissos was located on Mount Hasan.[115] The mountain is considered to be the second beacon of theByzantine beacon system, which was used to relay information from theTaurus Mountains to the Byzantine capitalConstantinople.[116]
