Taftan (volcano)

Taftan(Balochi:تپتان,Taptân,Persian:تفتان,Taftân, inBalochiand alsoPersianfor "blistering, smoldering, fuming") is anactivestratovolcanoin south-easternIranin theSistan and Baluchestanprovince. With variable heights reported, all around 4,000 metres (13,000 ft) above sea level, it is the highest mountain in south-eastern Iran. The nearest city isKhash.
Taftan has two main summits, Narkuh and Madehkuh, and various heights have been reported for both summits. The northwestern Narkuh has twocratersand is the older of the two summits. The southeastern Madehkuh summit is surrounded by fresh-lookinglava flowsand has at least three craters. The principal rock at Taftan isandesite.
Reports of historical volcanic activity are unclear and the youngestradiometricdates are 6,950 ± 20 years before present. Currently, the volcano features vigorousfumarolicactivity that is visible from a great distance and involves numerous vents on Materkuh. Taftan appears to be part of ageothermal area; there are a number ofhot springsaround the volcano.
Taftan is part of avolcanic arcin Iran, together withBazman, also in Iran, andKoh-i-Sultanin Pakistan. This volcanic arc has formed onCretaceous-Eocenesedimentary layers and has resulted from thesubductionof theoceanicArabian Platebeneath Iran at theMakran trench.
Taftan is in Iran'sSistan and Balochistan province. Closest cities areKhash45 kilometres (28 mi) south andZahedanc.100 kilometres (62 mi) north north-west.In 1844, Abdul-Nabi reported of the existence of the mountain, as well as its volcanic activity.In 1971, it was reported that someBeluchtribes camp on Taftan's slopes outside of winter.
Volcanic activity has occurred in parts of Iran since the Cretaceousperiod.During the Eocene andOligoceneepochs, volcanic activity reached its maximum, with thickpyroclasticlayers being deposited in central Iran and theAlborzmountains.The area around Taftan volcano belongs to atectoniczone which is variously referred to as the Sistan suture or the Zabul-Baloch zone. There, after a previous episode ofriftingand subsequent formation of an ocean, the Neh and Lut tectonic blocks collided during the Eocene epoch after a subduction episode that commenced in theMaastrichtianage.
Volcanic activity at Taftan itself appears to relate to the subduction of theArabian Platebeneath theCentral Iran Plate,occurring at a pace of 2.5–3.0 centimetres per year (0.98–1.18 in/year)or 3.5–4.2 centimetres per year (1.4–1.7 in/year) at the Makran trench.This subduction is also responsible for volcanism at Bazman in Iran and Koh-i-Sultan in Pakistan;this chain is known as the Baluchistan volcanic arc.The volcanism appears to not align with pre-existent structural trends in the basement.This subduction has also created anaccretionary wedgethat forms theMakranregion.
The convergence of the two blocks continued even after their collision, generatingstrike-slip faults. The Saravan fault east of Taftan is one such fault;the2013 Saravan earthquakeoccurred on this fault.From some of these faults it has been inferred that the mass load from the Taftan edifice has measurable effects on tectonicstresswithin the region.
Taftan is the highest mountain in southeast Iran.The topography is overall steep.Deep valleys with U and V shapes have developed on Taftan, and the volcano has a strongly eroded appearance.One of these valleys,Tamindan, may be the Damindan valley in theAvestareligious texts.One series ofignimbritessurrounding Taftan which reaches thicknesses of 50 metres (160 ft) and reaches distances of 15 kilometres (9.3 mi) from the edificemay be 2 million years old.
The basement of Taftan is formed by varioussedimentary rocks, along with somemaficvolcanic rocks andmetamorphicrocks. At Taftan, the Nehbandan-Khashflyschborders theMakran zone.The oldest rocks arelimestonesfrom the Cretaceous period.The crust beneath Taftan is approximately 60 kilometres (37 mi) thick.The main edifice is constructed on top of the Eocene flysch,although some Cretaceous sediments are also part of the basement.Much of these rocks is coloured pink byhaematite.The 19 mya old Mirabadgraniteplutonmay be associated with Taftan;it could be the remnant of a Miocene volcano.Volcanic rocks ofQuaternaryage are widespread in the area.
Taftan is a volcano with several summits; the highest two are separated by a saddle and are named Narkuh or Narkooh and Materkuh or Madekooh,which are 2 kilometres (1.2 mi) apart.Narkuh is 4,100 metres (13,500 ft) high and Materkuh 3,950 metres (12,960 ft).There are different heights reported for the summits, some of them placing Materkuh as the higher of the two:for example more recent Iranian maps cited in 2004 show Narkuh with a height of 3,840 metres (12,600 ft) and Materkuh with a height of 3,940 metres (12,930 ft), while Gansser in 1964 indicated a summit height of 4,050 metres (13,290 ft).Another report from 1931 claimed a summit height of 3,973 metres (13,034 ft),a report in 1976 stated 4,032 metres (13,228 ft),and a map in 2004 claimed a measurement of 4,061 metres (13,323 ft).These summits rise 2,000 metres (6,600 ft) above the surrounding plains.
Narkuh has two craters, the northern of which is lower and is the source of more lava flows than the southern.The northwest Narkuh cone from thePleistoceneage is highly eroded, while the southeastern Materkuh cone has fresh appearinglava flowsand displayssolfataricactivity.Materkuh has three principal craters,although the eastern side of the eastern crater has also been affected by erosion.Alternatively, an explosive eruption removed the eastern side and generated a steep ravine. The northern crater has been the source of lava flows, some of which are well preserved and reach lengths of 12 kilometres (7.5 mi).In general, thick andesitic lava flows cover Materkuh.In 1893 and 1914,Percy Sykesdescribed a summit plateau with a surface of 370 metres (400 yd), at the side of which lay the two summits Ziaret Kuh ("Hill of Sacrifice", where pilgrims sacrificed goats) and Madar Kuh ("Mother Hill", containing fumaroles according to the 1893 report).Fumarolic alteration of the summit area has generated sulfur andclaydeposits which resemble snowcap.One report in 1893 indicated that the summit area of the volcano was covered with ash from 3,400 metres (11,000 ft) upwards.
The bulk of the volcano is formed by lava flows, along withvolcaniclasticrocks,with dacites and pyroclastics lying on top of the Cretaceous-Eocene basement.These loose rocks formed by erosion, explosive activity and hot avalanches and are deposited in a large apron at the base of the volcano that extends over 30 kilometres (19 mi) away from the central vents.Several fans of pyroclastic material, cemented by andesitictuffs, surround the base of Taftan.Ignimbrites andpyroclastic flowsare also present, includingbreccias,nuee ardentesand tuffs.Volcanic rocks cover a surface of 1,050 square kilometres (410 sq mi).There is also evidence of southeastern migration of the craters of Taftan, with Anjerk and Sardarya being more westerly vents.These preceding centres have left andesitic lava flows that are partially dissected andagglomerates.The existence of acalderaat Taftan has been inferred.The table mountain Takht-i-Rostam 25 kilometres (16 mi) south of Taftan may be the remnant of a basalt extrusion, but it doesn't appear to be related to Taftan.Amagma chambermay lie beneath the volcano.
Taftan has erupted lavas ranging frombasaltic andesitetodacite. The dominant rock is andesite, withSiO2content ranging from 49.8 to 63.5%.Grey andesites form the youngest rocks on the main summit and containchloriteschistandbiotitegneissinclusions.The andesites are vesicular.The magma of Taftan volcano is very oxidized, as can be inferred from the composition of the surrounding ignimbrite and fumarole gases.
The lavas of Taftan are porphyritic. Mineral components include biotite,clinopyroxene,hornblende,orthopyroxene,plagioclaseandquartz. Other components arechalcopyrite, haematite,ilmenite,magnetiteandpyrite.Complexphenocrystassemblages found in a sample indicate that the magma formation is a complex process.Taftan rocks overall arepotassium-richcalc-alkaline,of sub–alkaline affinity.The magma that formed these rocks was influenced bycrystal fractionationand mixing processes.Its composition has characteristics of volcanic arc magmas.Crustal materials were involved in the formation of the magma,withstrontiumisotope data indicating crustal assimilation.
Fumarolic activity affects surrounding rocks and pyroclastics.Carbonates,opal, and white covers of possiblyaluminum sulfateandcalcium sulfatehave been formed.Gypsumformed from the sulfur of the volcano is found in the form of crystals in the upper valleys of Taftan.Sinterand hydrothermally altered rocks are found farther down.Minerals formed by alteration processes includealunite,calcite,cristobalite,illite,jarosite,kaolinite,pyrophyllite, quartz,smectite, sulfur andtridymite.Someepithermalmineralizations have been identified around Taftan.Other secondary factors at Taftan includelahars.
About five different active eruption periods have been discovered at Taftan volcano.Activity first involved lava and pyroclastics of dacitic torhyodaciticcomposition. Later, upperPliocenelavas were erupted along with agglomerates. These can be found up to 10 kilometres (6.2 mi) away from the cone.Three phases have been dated at 6.95 ± 0.72, 6.01 ± 0.15 and 0.71 ± 0.03 million years ago;an even older phase west-northwest of the current volcano occurred 8 million years ago,while aQuaternaryignimbrite has produced an age of 404,000 ± 82,000 years before present.The youngest dates have been obtained on lava flows and indicate ages of 6,950 ± 20 years ago, byradiometric dating.Research published in 1897 indicated the absence of very fresh lava flows but the authors inferred from the fresh ash that volcanic activity had occurred during the present geological epoch.That the name "Taftan" may be derived from an ancient Iranian word "taft" for "semi solid liquid material" could indicate thateffusive activitywas witnessed by the people of that time period around the volcano.
It is not certain that there were anyHoloceneeruptions at Taftan, as clear evidence of such activity is missing.Eruptions are recorded in 1902, 1970 and 1993. A report of smoke emission in 1877 may have confusedcloudsfor volcanic activity.In 1914, the volcano was described to be "belching out clouds of smoke",although a report in 1971 indicated the absence of historical activity.These eruptions were accompanied by earthquake activity.During the eruption of 1902, heavy smoke and a night time glow on the volcano were observed.The eruption in 1993 involved ac.60 metres (200 ft) long lava flow,but it may have been a flow of molten sulfur.The volcano is currently classified as adormant volcano.Satellite imagery indicates, however, thatground deformationoccurs at Taftan.Unofficial volcano hazard maps have been developed.
Taftan displays vigorousfumarolicactivity, with high temperature vents found around the crater.Fumaroles are found chiefly in the eastern and at the edge of the western crater, with minor fumaroles within the western crater, along some minor craters and along the major lava flow.These gas exhalations are known as "Dood" by local peoples and they appear as yellow-white clouds with a strong smell. The vents they come from have the shape of fissures, cracks and crevices.The larger fumaroles can reach diameters of 1 metre (3 ft 3 in).The occurrence ofhydrothermal explosionshas been inferred from the presence ofbrecciamade up by volcanic rocks.
Reportedly in 1897 the smell of the fumaroles was so strong as to be unbearable when one was close to the vents.One report mentioned in a magazine of 1899 indicated the presence of seven steam vents at an altitude of 3,700 metres (12,000 ft), produced audible noise. Their steam plumes were visible at distances of 16–24 kilometres (10–15 mi);later reporting indicated visibility to distances of 100 kilometres (62 mi).Another report in 1999 found a 1.5 by 5 metres (4 ft 11 in × 16 ft 5 in) solfatara surrounded by clay and sulfur deposits that looked like a snowcap.A fumarole field was described on the west side of the southeast cone, the venting clearly visible from arefugefarther down the mountain and covering a surface area ofc.10 square metres (110 sq ft).The name "Taftan" is derived from these exhalations, which make the mountain appear to be burning.
The overall gas composition found at Taftan includesCO2,H2S,SO2andwater.Sulfuris present in high quantities in fumarolic gases, which also containarsenic. These gases are hence extremely acidic.The fumaroles have altered rocks, forming highly colourful exposures especially on Taftan's eastern flank.Ammonium chloride(salmiak) and sulfur has been collected around fumaroles.The thick sulfur layers on the southeastern summit were formerly extracted for use in Iran and Pakistan. Sulfur and sulfate deposits are also found lower on the volcano, from hot springs around Gooshe, at Sangān and Torshāb.
Hot springs are also found at Taftan, especially at over 3,000 metres (9,800 ft) altitude.An analysis of five springs in May 2012 indicated temperatures of 11–56 °C (52–133 °F) and flow rates of 0.5–11 litres per second (0.018–0.388 cu ft/s).The waters are very acidic due to the formation ofH2SO4from magmatic gases,including the oxidation ofH2S.The hot waters around Taftan contain large quantities ofboron,probably because the hydrothermal system of Taftan is young and receives input of host rocks containingboron.They are influenced by the fumarolic gases,as well as by volcanic rock composition. Some of the water in the area is juvenile,with magmatic water forming up to 20% of the water.Temperatures in the hydrothermal system are estimated to be between 104–210 °C (219–410 °F) and 75–185 °C (167–365 °F).The composition of the water in various springs around Taftan varies in terms of elemental composition, probably reflecting the mixing between volcanic and meteoric waters and interaction with host rocks andbrines.The geothermal area of Taftan is among the largest in the Makran zone of Iran;it covers a surface area of 4,310 square kilometres (1,660 sq mi).Other geothermal manifestations in southeastern Iran have been found at Bazman.Mud poolsare also found at Taftan.Probably due to decreased precipitation, before 2002 a trend to increased steam and decreased water release has been observed, especially in the upper part of the geothermal system.
Hot springs and other geothermal manifestations are widespread in Iran and using them to gain geothermal energy has been studied; according to a report of 2002 hot springs at that time were mainly used for therapeutic purposes and bathing.A report in 2002 indicated that Taftan may be a feasible place to install abinary cyclepower plant.
The climate at Taftan features cold winters accompanied bysnowfallwhen temperatures drop below freezing between December and February, and hot summers with temperatures during July and August exceeding 30 °C (86 °F).Taftan is located in anaridlocale but has more precipitation than the surrounding area, thus providing water to the surrounding terrain.Average precipitation is 150 millimetres (5.9 in) per year.
Owing to the height of the mountain, there are distinct vegetation belts at Taftan. The lowlands around the mountain are covered withArtemisiasteppe and occasionalshrubland. Openscrubsoccur in a higher altitude belt of 1,800–2,500 metres (5,900–8,200 ft) where the terrain is rocky, andthorn-cushion vegetationat elevations of 2,600–3,700 metres (8,500–12,100 ft); there is little vegetation in the summit area.The summit of Taftan and several other Iranian volcanoes were deemed national natural monuments in 2002.