Mount Hasan

Template:Short description Template:Infobox mountain Mount Hasan (Template:Langx) is a volcano in Anatolia, Turkey. It has two summits, the high eastern Small Hasan Dagi and the high Big Hasan Dagi, and rises about above the surrounding terrain. It consists of various volcanic deposits, including several calderas, and its activity has been related to the presence of several faults in the area and to regional tectonics.

Activity began in the Miocene and continued into the Holocene; a mural found in the archeological site of Çatalhöyük has been controversially interpreted as showing a volcanic eruption or even a primitive map. It was the second mountain from the south in the Byzantine beacon system used to warn the Byzantine capital of Constantinople of incursions during the Arab–Byzantine wars.

Etymology

The modern name of Mount Hasan is widely accepted to be in dedication to Ebu'l-Gazi (El-Hasan), brother of Ebu'l-Kasım during the reign of the Anatolian Seljuks. It is hypothesized that Mount Hasan’s name was “Argeos” or “Argaios”, but this name belongs to Mount Erciyes. Another hypothesis is that it was simply called Árgos, (Ancient Greek: Ἄργος) as well as Argeiopolis Mons. The Hittites called it .

Geography and geomorphology

File:Aksaray 1998 06.jpg

A street of Aksaray with Mount Hasan in the background

File:MT HASSAN DORMANT VOLCANO CAPPADOCIA CENTRAL TURKEY OCT 2011 (6394626553).jpg

Mount Hasan viewed from the north in a sunset

Mount Hasan lies in the Anatolian plateau, between the Taurus Range and the Pontic Mountains,Template:Sfn and its and Mount Erciyes's silhouettes dominate the landscapeTemplate:Sfn and rise high above the surrounding terrain.Template:Sfn The city of Aksaray lies northwest from Mount Hasan,Template:Sfn while the settlements of Helvadere, Uluören, Dikmen and Taşpınar lie clockwise from north to northwest around the volcano.Template:Sfn In addition, there are seasonal settlements on the volcano which are associated with summer pastures.Template:Sfn The volcano has been prospected as a potential source for geothermal power.Template:Sfn

Mount Hasan is part of a larger volcanic province in Central AnatoliaTemplate:Sfn known as the Central Anatolian or Cappadocian Volcanic Province.,Template:Sfn which includes ignimbrites, monogenetic volcanic fields and stratovolcanoes such as Mount Erciyes, Mount Hasan,Template:Sfn KaracadağTemplate:SfnTemplate:Sfn and Melendiz DağTemplate:Sfn with an area of about Template:Sfn-.Template:Sfn Volcanism took place during the Plio-Pleistocene and into the Quaternary.Template:Sfn

The volcano has two summits, the high eastern Small Hasan Dagi/ and the high Big Hasan Dagi/, and consist of lava domes and lava flows.Template:Sfn Big Hasan Dagi has two nested craters with an wide and high inner cone that is the source of a lava flow.Template:Sfn Whether they are located within a caldera is unclear; rather than one large caldera encompassing the entire complex,Template:Sfn there may be a smaller one underlying Mount Hasan specifically.Template:Sfn There is periglacial activity on the summit, and fossil rock glaciers are found on the volcano.Template:Sfn The volcano as a whole rises almost around the surrounding terrainTemplate:Sfn and covers an area of with of rocks.Template:Sfn The terrain of Mount Hasan is formed by phreatomagmatic breccias, ignimbrites, lahar deposits, lava domes, lava flows and pyroclastic flow deposits.Template:Sfn The pyroclastic flow deposits occur in the form of fans or valley flows, when they were channelled by topography.Template:Sfn The northern flanks also feature twoTemplate:Sfn debris avalanche deposits with hummocky surfaces.Template:Sfn Two calderas, the caldera on the eastern and the on the southwestern flank, adorn the volcano.Template:Sfn The volcanics of Mount Hasan have been subdivided into a "hot flow" unit, a "Mt. Hasan ashes" unit and into a lava unit.Template:Sfn

Cinder cones, maars and accompanying lava flows also occur around Mount Hasan, they are part of a basaltic volcano familyTemplate:Sfn that forms parasitic vents.Template:Sfn These include the cone/maarTemplate:Sfn and a lava flow field at which covers an area of and was produced by fissure vents.Template:Sfn Many of the cones around Mount Hasan have been grouped as the Hasandağ-Karacadağ volcanic field.Template:Sfn

Geology

As a consequence of the subduction and eventual closure of the Neo-TethysTemplate:Sfn and continental collision between Arabia-Africa and Eurasia,Template:Sfn Anatolia moves westward at a rate of Template:Sfn between the North Anatolian Fault and the East Anatolian Fault. This movement and the resulting tectonic deformation of Anatolia are responsible for volcanism in Central Anatolia,Template:Sfn together with the subduction of the Cyprus Plate.Template:Sfn Volcanism has been ongoing for the past 10 million years;Template:Sfn it is defined as "post-collisional".Template:Sfn Further, volcanism at Mount Hasan has been related to the Tuz Gölü FaultTemplate:Sfn and its intersection with the Karaman-Aksaray faults;Template:Sfn the former of these is one of two major fault systems in Central Anatolia which influence volcanism there,Template:Sfn and volcanic products of Mount Hasan have been deformed by the fault.Template:Sfn The Hasandag fault branches off the Karaman-Aksaray fault and cuts between the two summits of Mount Hasan.Template:Sfn It and the Karacaören fault influence the hydrothermal system of the volcano.Template:Sfn

The westerly Mount Hasan, central Template:Sfn and easterly Template:Sfn form the Niğde Volcanic Complex,Template:Sfn a mountain range, which is surrounded by plains and whose summits reach heights of over . Of these mountains, is more heavily eroded compared to the steep cones of HasanTemplate:Sfn and like is of early Pliocene age.Template:Sfn This alignment is congruent with the tectonic patterns of Anatolia, where the collision between Africa and Eurasia follows the same trend.Template:Sfn It and to some degree Mount Hasan are also surrounded by a large depression,Template:Sfn and the volcanoes of this alignment are separated by faults.Template:Sfn Additionally, Mount Hasan forms a volcanic lineament with and the Karapınar Field.

The basement in Central Anatolia is formed by magmatic, metamorphic and ophiolitic rocks, the former of which are of Paleozoic to Mesozoic age;Template:Sfn it crops out at scattered sites and in the Kirshehir and Nigde massifs.Template:Sfn The surface however consists mainly of Tertiary volcanic rocks,Template:Sfn which are formed both by numerous ignimbrites,Template:Sfn volcaniclastic material and individual volcanoes.Template:Sfn Central Anatolia has undergone uplift, for which several mechanisms have been proposed.Template:Sfn

Composition

Mount Hasan has produced volcanic rocks with compositions ranging from basalt to rhyolite but the dominant components are andesite and daciteTemplate:Sfn which define an older tholeiitic and a younger calc-alkalineTemplate:Sfn or alkaline suite.Template:Sfn These rocks in turn include amphibole, apatite, biotite, clinopyroxene,Template:Sfn garnet,Template:Sfn ilmenite, mica,Template:Sfn olivine,Template:Sfn orthopyroxene, plagioclase,Template:Sfn pyroxeneTemplate:Sfn in the form of augite, bronzite, diopside, hypersthene and salite,Template:Sfn and quartz.Template:Sfn The older volcanic stages have produced basaltic andesiteTemplate:Sfn while dacite appears only in the most recent stage.Template:Sfn Obsidian also occurs in the most recent stageTemplate:Sfn although it is not an important componentTemplate:Sfn while most of the rocks are porphyritic.Template:Sfn The basaltic family includes both basaltic andesite and alkali basalts with augite, clinopyroxene, garnet, hornblende, hypersthene, olivine, orthopyroxene, oxides and plagioclase.Template:SfnTemplate:Sfn

Magma mixing processes appear to be the most important mechanisms involved in the genesis of Mount Hasan magmas,Template:Sfn which are derived from the mantle with participation of crustal components.Template:Sfn Evidence of fractional crystallization has been encountered in the most recent stage rocksTemplate:Sfn and more generally plays a role in the genesis of Hasan magmasTemplate:Sfn although it does not explain all of the compositional traits.Template:Sfn It appears that basaltic andesites formed through mixing, while fractional crystallization was more important for the genesis of other magmas.Template:Sfn Older volcanic stages also show evidence of subduction influenceTemplate:Sfn while the more recent magmas are more indicative of intraplate processes,Template:Sfn the effects of crustal extensionTemplate:Sfn and of the presence of water.Template:Sfn In general, various sources have been proposed for the magmas of the Central Anatolian province.Template:Sfn The magmatic system of Mount Hasan appears to be more active than that of Mount Erciyes.

The magmas formed at different depths, with basalts originating at about depth at the base of the crust, while the other volcanic rocks have shallower sources.Template:Sfn The basaltic magmas would have ascended into a shallow magma chamber at depth, mobilizing its contents and thus giving rise to the more silicic magmas.Template:Sfn The magma formation processes were quick, with only days or weeks going from the formation of the magma and its eruption on the surface.Template:Sfn

Ecology and hydrology

File:Güzelyurt 04 1999 Hasan Dağı.jpg

An ancient orthodox church known as St. Analipsis on Analipsis Hill, with Mount Hasan in the background. The Melendiz River can be seen in the bottom left.

Oak forests occur on Mount Hasan.Template:Sfn Annual precipitation is about .Template:Sfn Between October/November and May, the mountain is frequently covered by snow due to the common precipitation at that time and when it melts the water mostly infiltrates into the permeable rocks,Template:Sfn making the volcano a principal groundwater recharge area in the region.Template:Sfn Additionally, volcanics of Mount Hasan form a major aquiferTemplate:Sfn and the Melendiz River passes north and northeast of the volcano.Template:Sfn

Eruption history

Mount Hasan has been active for the last 13 million years, with the , Paleo-Hasan, Mesovolcano and Neovolcano stages during the Miocene, Miocene-Pliocene and Quaternary;Template:Sfn the older two stages might actually not be part of Mount Hasan at all.Template:Sfn Aside from the felsic central vent volcanism, basaltic volcanism also took place at Mount Hasan throughout its activity;Template:Sfn this activity has been dated to 120,000, 65,000Template:Sfn and the most recent event 34,000 years ago.Template:Sfn This volcanism however is not part of the actual Mount Hasan system.Template:Sfn The main edifice has produced about of magma every millennium, more than at Erciyes.Template:SfnTemplate:Sfn

is the oldest (13 million years) volcanic structure,Template:Sfn it is among the oldest volcanoes of the Central Anatolian volcanic province.Template:Sfn This volcano is a small sized volcano with a caldera which crops out on the southwestern side of Mount Hasan. It grew over sediments to a present-day elevation of ; today it is eroded, partly buried by the younger Hasan volcanicsTemplate:Sfn and disrupted by strike-slip faulting. About 7 million years ago the Paleovolcano began to grow north of ; 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.Template:Sfn The Paleovolcano also formed a caldera which produced the rhyolitic Dikmen-Taspinar Ignimbrites;Template:Sfn formerly the Cappadocian tuffs were in general attributed to volcanism at Mount Hasan, Mount Erciyes and Göllü Dag. Template:Sfn

The Quaternary 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 a caldera; it too has been dissected by faulting which probably also influenced the development of the volcanoTemplate:Sfn and its activity probably occurred between 1 and 0.15 million years ago.Template:Sfn Finally, the Neovolcano grew within the caldera, producing various kinds of deposits; these include lava domes with accompanying pyroclastic flow deposits, breccia in the rim of the Mesovolcano calderaTemplate:Sfn that probably formed through the interaction of intruding magma with water in the caldera,Template:Sfn 700,000 years ago rhyolitic flows and ignimbrites accompanied by the formation of another, caldera, and finally andesitic lava flows and lava domes which form the two main summits.Template:Sfn A major Plinian to sub-Plinian pumice-forming eruption took place 417,200 ± 20,500 years ago, forming the PumiceTemplate:Sfn and deposited fallout over much of Central Anatolia.Template:Sfn

Small Mount Hasan is probably older as it is more heavily eroded while the morphology of Big Hasan Dagi is fresherTemplate:Sfn although its pyroclastic flow deposits are heavily incised. Dates of 33,000 and 29,000 years ago have been obtained on the summit domesTemplate:Sfn and ages of 66,000±7,000 years on the most recent monogenetic volcano south of Mount Hasan. Explosive eruptions took place 28,900 ± 1,500 and 13,500 ± 1,500 years ago.Template:Sfn Tephras found in the Konya plainTemplate:Sfn and in a lake of the Turkish Lakes Region have been attributed to Mount Hasan. The debris flow from Mount Hasan occurred 150,000-100,000 years agoTemplate:Sfn and a number of lava flows were emplaced during the last 100,000 years.Template:Sfn

Holocene and present activity

Eruptions occurred 8,970 ± 640,Template:Sfn 8,200, less than 6,000 years agoTemplate:Sfn and 0 ± 3,000 years ago; the first emplaced pumice 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.Template:SfnTemplate:Sfn A shift in archeological sites around Mount Hasan may be linked to the older eruptions. There is no evidence of historical eruptions of the volcano.Template:Sfn

Hydrothermal activity also occurs at Mount Hasan, with fumaroles and water vapour emissions on the summit. The emission occurs along vents trending in a northeast-southwest direction, which are linked to a major regional fault.Template:Sfn Rocks around these vents have been chemically altered.Template:Sfn Another field of fumaroles and hot springs is on the northwestern side of Hasan.Template:Sfn Magnetotelluric and other imaging techniques have found evidence of a magma chamber at depth and of a magmatic body between .Template:SfnTemplate:Sfn A hydrothermal system mayTemplate:Sfn or may not exist.Template:Sfn There have been seismic swarms around Mount Hasan,Template:Sfn including one in 2020Template:Sfn next to a cinder cone that was active 2000 years ago,Template:Sfn and there is evidence that fumarolic and seismic activity has increased during the 2020s.Template:Sfn Reportedly, there are frequent explosions within the volcano.Template:Sfn

Future activity at Hasan could impact neighbouring villages, and larger eruptions might disrupt air traffic and tourism in Cappadocia.Template:Sfn since 2022Template:Dated maintenance category (articles) the volcano is not monitored.Template:Sfn

Possible portrayal of an eruption in a mural from Çatalhöyük

File:Mokisos (Viranşehir) with Hasan Dağı.jpg

The ancient town of Mokissos and Mount Hasan

A mural discovered in Çatalhöyük has been interpreted as showing a volcanic eruption, commonly linked to Mount Hasan, and this mural has even been interpreted as being the oldest known map. The interpretation of the mural showing a volcanic eruption has been contested howeverTemplate:Sfn as an alternative interpretation is that the "volcano" shown in the mural is actually a leopard and the "village" a set of random geometric motifs.Template:Sfn The map interpretation is also contested.Template:Sfn The mural is depicted in the Museum of Anatolian Civilizations in AnkaraTemplate:SfnTemplate:Sfn and has been cited as the first man-made diagram.

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 years BCE for ÇatalhöyükTemplate:Sfn and radiometric dating has produced evidence for explosive eruptions during that timeTemplate:Sfn and when the mural was made. The depicted activity resembles Strombolian eruptions, and the event may not have been directly visible from Çatalhöyük. The discovery of this mural has drawn attention to the volcanoTemplate:Sfn and has led to efforts to date the eruptive activity of Mount Hasan.Template:Sfn

Importance during ancient history

Mount Hasan was used as a source for Obsidian. The Byzantine city of Mokissos was located on Mount Hasan. The mountain is considered to be the second beacon of the Byzantine beacon system, which was used to relay information from the Taurus Mountains to the Byzantine capital Constantinople.

See also

• List of volcanoes in Turkey
• List of Ultras of West Asia

External links

• Template:Cite gvp
• Template:In lang Niğde