Ciomadul
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Ciomadul () is a
dormant volcano A volcano is commonly defined as a vent or fissure in the crust of a planetary-mass object, such as Earth, that allows hot lava, volcanic ash, and gases to escape from a magma chamber below the surface. On Earth, volcanoes are most often ...
in
Romania Romania is a country located at the crossroads of Central Europe, Central, Eastern Europe, Eastern and Southeast Europe. It borders Ukraine to the north and east, Hungary to the west, Serbia to the southwest, Bulgaria to the south, Moldova to ...
. It is in the
Eastern Carpathians Divisions of the Carpathians are a categorization of the Carpathian mountains system. Below is a detailed overview of the major subdivisions and ranges of the Carpathian Mountains. The Carpathians are a "subsystem" of a bigger Alps-Himalaya Sy ...
, between the spa towns of Băile Tușnad and Balvanyos. Ciomadul lies at the southeastern end of the Carpathian volcanic chain and it is the youngest volcano of the Carpatho-Pannonian region. Ciomadul consists of several
lava dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...
s with two embedded explosion craters known as Mohoș and Sfânta Ana, the latter of which contains a
crater lake Crater Lake ( Klamath: ) is a volcanic crater lake in south-central Oregon in the Western United States. It is the main feature of Crater Lake National Park and is a tourist attraction for its deep blue color and water clarity. T ...
,
Lake Sfânta Ana Lake Sfânta Ana (; ; ) is the only crater lake in Romania located in the volcanic crater of the Ciomad volcano of the Eastern Carpathians, near Tușnad in the Natural Reserve of Mohoș, Harghita County, Romania Romania is a country lo ...
. The dominant volcanic rock at Ciomadul is
potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...
-rich
dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...
. Volcanic activity at Ciomadul commenced with effusive activity about one million years ago. Most of the volcano was constructed between 650,000 – 500,000 years ago. Between 56,000 and 32,000 years ago explosive volcanic activity occurred at Ciomadul. Both the exact dates of the various eruptions and of the formation of the Sfânta Ana and Mohoș craters are unclear, partly because dates obtained by potassium-argon dating and other dating techniques deviate from each other. Some eruptions may have reached sub-
Plinian Plinian eruptions or Vesuvian eruptions are volcanic eruptions characterized by their similarity to the eruption of Mount Vesuvius in 79 AD, which destroyed the ancient Roman cities of Herculaneum and Pompeii. The eruption was described in a le ...
strength, ejecting
volcanic ash Volcanic ash consists of fragments of rock, mineral crystals, and volcanic glass, produced during volcanic eruptions and measuring less than 2 mm (0.079 inches) in diameter. The term volcanic ash is also often loosely used to r ...
as far as the
Black Sea The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bound ...
. The last eruption took place between 32,600 and 27,500 years ago. Its date is likewise unclear. Ongoing seismic and
geothermal activity Geothermal activity is a group of natural heat transfer processes, occurring on Earth's surface, caused by the presence of excess heat in the subsurface of the affected area, usually caused by the presence of an igneous intrusion underground. Geot ...
, and exhalations of
volcanic gas Volcanic gases are gases given off by active (or, at times, by dormant) volcanoes. These include gases trapped in cavities (Vesicular texture, vesicles) in volcanic rocks, dissolved or dissociated gases in magma and lava, or gases emanating from ...
and evidence of a still existing
magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it u ...
indicate that Ciomadul is a potentially active volcano.


Geography and geology


Regional setting

With the exception of
Greece Greece, officially the Hellenic Republic, is a country in Southeast Europe. Located on the southern tip of the Balkan peninsula, it shares land borders with Albania to the northwest, North Macedonia and Bulgaria to the north, and Turkey to th ...
and
Italy Italy, officially the Italian Republic, is a country in Southern Europe, Southern and Western Europe, Western Europe. It consists of Italian Peninsula, a peninsula that extends into the Mediterranean Sea, with the Alps on its northern land b ...
, the most recent
volcanic activity Volcanism, vulcanism, volcanicity, or volcanic activity is the phenomenon where solids, liquids, gases, and their mixtures erupt to the surface of a solid-surface astronomical body such as a planet or a moon. It is caused by the presence of a he ...
in Continental Europe occurred between 40,000 and 6,500 years ago in
Garrotxa Garrotxa () is a comarca (county) in the Girona region, Catalonia, Spain. Its population in 2016 was 55,999, more than half of them in the capital city of Olot. It is roughly equivalent to the historical County of Besalú. Geography Garrotx ...
, the Massif Central and the
Vulkaneifel Vulkaneifel () is a district (''Kreis'') in the northwest of the state Rhineland-Palatinate, Germany. It is the least densely populated district in the state and the fourth most sparsely populated district in Germany. The administrative centre of ...
. Volcanism in the region of Carpathia and
Pannonia Pannonia (, ) was a Roman province, province of the Roman Empire bounded on the north and east by the Danube, on the west by Noricum and upper Roman Italy, Italy, and on the southward by Dalmatia (Roman province), Dalmatia and upper Moesia. It ...
has been ongoing since 20 million years ago but has decreased during the
Quaternary The Quaternary ( ) is the current and most recent of the three periods of the Cenozoic Era in the geologic time scale of the International Commission on Stratigraphy (ICS), as well as the current and most recent of the twelve periods of the ...
. No eruptions took place in the
Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...
. The last volcanism occurred at Ciomadul in the last glacial age. Sparse
basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% ...
volcanism has also taken place in the area, forming
monogenetic volcanic field A monogenetic volcanic field is a type of volcanic field consisting of a group of small monogenetic volcanoes, each of which erupts only once, as opposed to polygenetic volcanoes, which erupt repeatedly over a period of time. The small monogenetic ...
s. A
volcanic arc A volcanic arc (also known as a magmatic arc) is a belt of volcanoes formed above a subducting oceanic tectonic plate, with the belt arranged in an arc shape as seen from above. Volcanic arcs typically parallel an oceanic trench, with the arc ...
lies in the
Carpathians The Carpathian Mountains or Carpathians () are a range of mountains forming an arc across Central Europe and Southeast Europe. Roughly long, it is the third-longest European mountain range after the Urals at and the Scandinavian Mountains ...
. In its southern segment, also known as the Călimani (Kelemen) – Gurghiu (Görgényi) – Harghita (Hargita) chain, volcanism has migrated between 9 and 0.22 million years ago southward, forming a volcanic chain. Magma output progressively decreased during time, with early volcanoes being large
stratovolcano A stratovolcano, also known as a composite volcano, is a typically conical volcano built up by many alternating layers (strata) of hardened lava and tephra. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile with ...
es sometimes featuring
caldera A caldera ( ) is a large cauldron-like hollow that forms shortly after the emptying of a magma chamber in a volcanic eruption. An eruption that ejects large volumes of magma over a short period of time can cause significant detriment to the str ...
-forming eruptions, while more recent activity includes monogenetic volcanoes although more precise dating and volume estimation efforts at Ciomad have found an increase of eruption rates over time. This volcanism occurs in a setting where the collision between the Eurasian Plate and the Tisza-Dacia
microplate A microplate, also known as a microtiter plate, microwell plate or multiwell, is a flat plate with multiple "wells" used as small test tubes. The microplate has become a standard tool in analytical research and clinical diagnostic testing lab ...
took place, preceded by a stage of
subduction Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...
involving a narrow
ocean The ocean is the body of salt water that covers approximately 70.8% of Earth. The ocean is conventionally divided into large bodies of water, which are also referred to as ''oceans'' (the Pacific, Atlantic, Indian Ocean, Indian, Southern Ocean ...
. This is part of the collision between the African Plate and the Eurasian Plate;
subduction Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at the convergent boundaries between tectonic plates. Where one tectonic plate converges with a second p ...
may still be underway in the area of the Carpathians. The , which is away from Ciomadul, features ongoing
earthquake An earthquakealso called a quake, tremor, or tembloris the shaking of the Earth's surface resulting from a sudden release of energy in the lithosphere that creates seismic waves. Earthquakes can range in intensity, from those so weak they ...
activity; deep earthquakes suggest that a remnant of a
slab Slab or SLAB may refer to: Physical materials * Concrete slab, a flat concrete plate used in construction * Stone slab, a flat stone used in construction * Slab (casting), a length of metal * Slab (geology), that portion of a tectonic plate that ...
exists beneath the Vrancea Zone. This tectonic setting may also be responsible for ongoing exhumation in the southeastern Carpathians, volcanism at Ciomadul and the Perșani volcanic field, south of Ciomad, which was concurrently active to the older Ciomadul activity. Other theories on Ciomadul's volcanic activity imply
delamination Delamination is a mode of failure where a material fractures into layers. A variety of materials, including Lamination, laminate Composite material, composites and concrete, can fail by delamination. Processing can create layers in materials, suc ...
of the
lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time ...
or roll-back of the subduction zone. Volcanism in this chain is
calc-alkaline The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic ...
, yielding both
andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...
,
dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...
, and
rhyolite Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture (geology), texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained matri ...
. Three million years ago, a change in the chemistry of volcanism occurred, with an increased content of
potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...
in the rocks. This change in composition geographically coincided with the volcanic activity crossing a lineament known as the Trotuș line.


Volcano

Ciomadul is located in the southeastern
Carpathians The Carpathian Mountains or Carpathians () are a range of mountains forming an arc across Central Europe and Southeast Europe. Roughly long, it is the third-longest European mountain range after the Urals at and the Scandinavian Mountains ...
, at the end of the Călimani (Kelemen) – Gurghiu (Görgényi) – Harghita (Hargita) volcanic chain, and is also known as Csomád in Hungarian. The
gorge A canyon (; archaic British English spelling: ''cañon''), gorge or chasm, is a deep cleft between escarpments or cliffs resulting from weathering and the erosion, erosive activity of a river over geologic time scales. Rivers have a natural tend ...
of the
Olt River The Olt ( Romanian and Hungarian; ; or ', , ''Alytos'') is a river in Romania. It is long, and its basin area is . It is the longest river flowing exclusively through Romania. Its average discharge at the mouth is . It originates in the Hă ...
separates Ciomadul from the Harghita Mountains. The towns of Băile Tușnad and Bixad are close to the volcano, and a road leads up the volcano from the southeast and goes past the Mohoș swamp to
Lake Sfânta Ana Lake Sfânta Ana (; ; ) is the only crater lake in Romania located in the volcanic crater of the Ciomad volcano of the Eastern Carpathians, near Tușnad in the Natural Reserve of Mohoș, Harghita County, Romania Romania is a country lo ...
. The basement of the volcano is formed by
flysch Flysch () is a sequence of sedimentary rock layers that progress from deep-water and turbidity flow deposits to shallow-water shales and sandstones. It is deposited when a deep basin forms rapidly on the continental side of a mountain building ep ...
of
Cretaceous The Cretaceous ( ) is a geological period that lasted from about 143.1 to 66 mya (unit), million years ago (Mya). It is the third and final period of the Mesozoic Era (geology), Era, as well as the longest. At around 77.1 million years, it is the ...
age and by older volcanics; in some places volcanic rocks overlie fluvial deposits. Places around Ciomadul were first mentioned in 1349; the Saxon mineralogist Johann Ehrenwert Fichtel was the first to interpret it as a volcano, in 1780. The idea that Ciomadul could be a still active volcano was first proposed in the same year on the basis of its young appearance and the release of gas. These discoveries drew scholars and visitors to the volcano and the first scientific analysis of the volcano was published just eight years later. While a publication in 1964 postulated that the
tuff Tuff is a type of rock made of volcanic ash ejected from a vent during a volcanic eruption. Following ejection and deposition, the ash is lithified into a solid rock. Rock that contains greater than 75% ash is considered tuff, while rock co ...
s of Ciomadul were reworked
Pliocene The Pliocene ( ; also Pleiocene) is the epoch (geology), epoch in the geologic time scale that extends from 5.33 to 2.58volcanites, the late
Pleistocene The Pleistocene ( ; referred to colloquially as the ''ice age, Ice Age'') is the geological epoch (geology), epoch that lasted from to 11,700 years ago, spanning the Earth's most recent period of repeated glaciations. Before a change was fin ...
age was established soon afterwards. The volcano is the youngest volcanic centre in the Carpathians and has a more rugged appearance than the surrounding mountains. Ciomadul is formed by a complex of
lava dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...
s and other volcanic material that form a south-tilting ridge that rises above the surrounding Lower Ciuk Basin. Individual lava domes form cone-shaped hills, which reach heights of and widths of . Individual domes include Haramul Ierbos (Fű-Haram in Hungarian), Haramul Mare (Nagy-Haram), Haramul Mic (Kis-Haram), Vf. Cetății (Vár-tető), Vf. Comloș (Komlós-tető), Vf. Surduc (Szurdok-tető) and Dealul Mare southeast from the main complex. The central cluster of domes is elliptical and tectonic faults influenced their growth. The highest point of the complex is Ciomadul Mare (Nagy-Csomád) with an altitude of . Some domes were later affected by
erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...
,
explosive An explosive (or explosive material) is a reactive substance that contains a great amount of potential energy that can produce an explosion if released suddenly, usually accompanied by the production of light, heat, sound, and pressure. An ex ...
activity or fumarolic alteration. The whole volcanic complex covers a surface area of , and is surrounded by a circular/semicircular plain made of volcanic debris. The lava dome complex contains two
crater A crater is a landform consisting of a hole or depression (geology), depression on a planetary surface, usually caused either by an object hitting the surface, or by geological activity on the planet. A crater has classically been described ...
s, named Mohoș and Sfânta Ana. They were formed in the previously existing lava domes which form the western margin of the craters, while products of
explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a Viscosity, viscous ...
s crop out in the east. The Sfânta Ana crater is wide and deep beneath the rim, comparable with the crater of
El Chichón El Chichón, also known as Chichonal, is an active volcano in Francisco León, north-western Chiapas, Mexico. El Chichón is part of a geologic zone known as the Chiapanecan Volcanic Arc. El Chichón is a stratovolcano with a complex of domes w ...
volcano in
Mexico Mexico, officially the United Mexican States, is a country in North America. It is the northernmost country in Latin America, and borders the United States to the north, and Guatemala and Belize to the southeast; while having maritime boundar ...
. This crater lacks a breach and is relatively unaffected by erosion. It contains a
crater lake Crater Lake ( Klamath: ) is a volcanic crater lake in south-central Oregon in the Western United States. It is the main feature of Crater Lake National Park and is a tourist attraction for its deep blue color and water clarity. T ...
, which once may have been over deep. This lake is known as Lake Sfânta Ana () and lies at an altitude of ; its ecosystem and environment has drawn the attention of scientists for two centuries. The Mohoș crater lies at an altitude of . It is larger than Sfânta Ana with a diameter of and not as deep with its bottom lying above sea level. It is filled with a and ''
Sphagnum ''Sphagnum'' is a genus of approximately 380 accepted species of mosses, commonly known as sphagnum moss, also bog moss and quacker moss (although that term is also sometimes used for peat). Accumulations of ''Sphagnum'' can store water, since ...
''
peat bog A bog or bogland is a wetland that accumulates peat as a deposit of dead plant materials often mosses, typically sphagnum moss. It is one of the four main types of wetlands. Other names for bogs include mire, mosses, quagmire, and muske ...
and its rim is cut by the Sfânta Ana crater. Unlike Sfânta Ana, the Mohoș crater has been breached by erosion, causing the formation of an outlet valley. Both craters were formed by
explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a Viscosity, viscous ...
s and distinguishing between the deposits of both is difficult. The existence of an even larger crater with a diameter of has been suggested, encompassing both Sfânta Ana and Mohoș.
Pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...
deposits generated by Ciomadul have been found on its northeastern, southern and western slopes. They reach a distance of as much as from the volcano. At Tușnad road, one of the flows has a thickness of . Tephra fall bed,
lapilli Lapilli (: lapillus) is a size classification of tephra, which is material that falls out of the air during a volcanic eruption or during some meteorite impacts. ''Lapilli'' is Latin for "little stones". By definition lapilli range from in dia ...
, and surge deposits are also found, and the flow deposits contain pumice blocks. One lapilli layer, thick, from Ciomadul has been identified east of the volcano. The whole pyroclastic formation has been subdivided into three classes known as "Early Phreatomagmatic + Plinian Activity", "Middle Plinian Activity" and "Latest Sfânta Ana Phreatomagmatic Activity". Each comprise a number of individual tephra layers that were erupted 42,000—40,000, around 31,500 and 29,000—28,000 years ago. Some of these eruptions may have dammed the Olt river; when the river returned on its course it produced
lahar A lahar (, from ) is a violent type of mudflow or debris flow composed of a slurry of Pyroclastic rock, pyroclastic material, rocky debris and water. The material flows down from a volcano, typically along a valley, river valley. Lahars are o ...
deposits. Other
landform A landform is a land feature on the solid surface of the Earth or other planetary body. They may be natural or may be anthropogenic (caused or influenced by human activity). Landforms together make up a given terrain, and their arrangement ...
s at Ciomadul include coulees and
lava flow Lava is molten or partially molten rock (magma) that has been expelled from the interior of a terrestrial planet (such as Earth) or a Natural satellite, moon onto its surface. Lava may be erupted at a volcano or through a Fissure vent, fractu ...
s. The total volume of the complex is about dense rock equivalent. Drilling has identified the existence of an
intrusion In geology, an igneous intrusion (or intrusive body or simply intrusion) is a body of intrusive igneous rock that forms by crystallization of magma slowly cooling below the surface of the Earth. Intrusions have a wide variety of forms and com ...
at a depth of . Finally, volcanic erosion products and tephra occur all over the volcanic complex and up to east of it. Older volcanic centres extend northwest of Ciomadul. With increasing distance they are the 2.5—1.5 million-year-old Pilisca centre, the 2.8—2.2 million-year-old Cucu centre and the 4.3—3.6 million-year-old Luci-Lazu and Șumuleu-Ciuc volcanic centres. South of Ciomadul the Murgul
shoshonite Shoshonite is a type of igneous rock. More specifically, it is a potassium-rich variety of basaltic trachyandesite, composed of olivine, augite and plagioclase phenocrysts in a Matrix (geology), groundmass with calcic plagioclase and sanidine and ...
s were erupted 2.3—1.5 million years ago; they represent cryptodomes.
Andesite Andesite () is a volcanic rock of intermediate composition. In a general sense, it is the intermediate type between silica-poor basalt and silica-rich rhyolite. It is fine-grained (aphanitic) to porphyritic in texture, and is composed predomina ...
lava flows from Pilisca underlie the Ciomadul deposits in some places.


Composition

The principal rock is
dacite Dacite () is a volcanic rock formed by rapid solidification of lava that is high in silica and low in alkali metal oxides. It has a fine-grained (aphanitic) to porphyritic texture and is intermediate in composition between andesite and rhyolite. ...
, which defines a
potassium Potassium is a chemical element; it has Symbol (chemistry), symbol K (from Neo-Latin ) and atomic number19. It is a silvery white metal that is soft enough to easily cut with a knife. Potassium metal reacts rapidly with atmospheric oxygen to ...
-rich
calc-alkaline The calc-alkaline magma series is one of two main subdivisions of the subalkaline magma series, the other subalkaline magma series being the tholeiitic series. A magma series is a series of compositions that describes the evolution of a mafic ...
suite. The rocks have a porphyric appearance and contain few vesicles. They are also very rich in crystals, with the dominant
phenocryst image:montblanc granite phenocrysts.JPG, 300px, Granites often have large feldspar, feldspathic phenocrysts. This granite, from the Switzerland, Swiss side of the Mont Blanc massif, has large white phenocrysts of plagioclase (that have trapezoid sh ...
-forming minerals being
biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron- endmember annite, and the magnesium-endmember phlogopite; more al ...
,
hornblende Hornblende is a complex silicate minerals#Inosilicates, inosilicate series of minerals. It is not a recognized mineral in its own right, but the name is used as a general or field term, to refer to a dark amphibole. Hornblende minerals are common ...
and
plagioclase Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continu ...
. Less important are
allanite Allanite (also called orthite) is a sorosilicate group of minerals within the broader epidote group that contain a significant amount of rare-earth elements. The mineral occurs mainly in metamorphosed clay-rich sediments and felsic igneous rocks. ...
,
apatite Apatite is a group of phosphate minerals, usually hydroxyapatite, fluorapatite and chlorapatite, with high concentrations of Hydroxide, OH−, Fluoride, F− and Chloride, Cl− ion, respectively, in the crystal. The formula of the admixture of ...
,
clinopyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron (Fe ...
,
olivine The mineral olivine () is a magnesium iron Silicate minerals, silicate with the chemical formula . It is a type of Nesosilicates, nesosilicate or orthosilicate. The primary component of the Earth's upper mantle (Earth), upper mantle, it is a com ...
,
orthopyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron (Fe( ...
,
quartz Quartz is a hard, crystalline mineral composed of silica (silicon dioxide). The Atom, atoms are linked in a continuous framework of SiO4 silicon–oxygen Tetrahedral molecular geometry, tetrahedra, with each oxygen being shared between two tet ...
,
sphene Titanite, or sphene (), is a calcium titanium nesosilicate mineral, Ca Ti Si O5. Trace impurities of iron and aluminium are typically present. Also commonly present are rare earth metals including cerium and yttrium; calcium may be partly rep ...
and
zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...
. The groundmass contains
plagioclase Plagioclase ( ) is a series of Silicate minerals#Tectosilicates, tectosilicate (framework silicate) minerals within the feldspar group. Rather than referring to a particular mineral with a specific chemical composition, plagioclase is a continu ...
,
pyroxene The pyroxenes (commonly abbreviated Px) are a group of important rock-forming inosilicate minerals found in many igneous and metamorphic rocks. Pyroxenes have the general formula , where X represents ions of calcium (Ca), sodium (Na), iron ( ...
,
silicon dioxide Silicon dioxide, also known as silica, is an oxide of silicon with the chemical formula , commonly found in nature as quartz. In many parts of the world, silica is the major constituent of sand. Silica is one of the most complex and abundan ...
and
oxides An oxide () is a chemical compound containing at least one oxygen atom and one other element in its chemical formula. "Oxide" itself is the dianion (anion bearing a net charge of −2) of oxygen, an O2− ion with oxygen in the oxidation state o ...
of
iron Iron is a chemical element; it has symbol Fe () and atomic number 26. It is a metal that belongs to the first transition series and group 8 of the periodic table. It is, by mass, the most common element on Earth, forming much of Earth's o ...
and
titanium Titanium is a chemical element; it has symbol Ti and atomic number 22. Found in nature only as an oxide, it can be reduced to produce a lustrous transition metal with a silver color, low density, and high strength, resistant to corrosion in ...
. Clots formed by various
felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...
crystals are common. The composition of Ciomadul's rocks has been fairly constant throughout its evolution albeit with two shifts 1 million and 650,000 years before present, and this diversity of its components indicate that the genesis of Ciomadul magmas involved mixing between
felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...
and
mafic A mafic mineral or rock is a silicate mineral or igneous rock rich in magnesium and iron. Most mafic minerals are dark in color, and common rock-forming mafic minerals include olivine, pyroxene, amphibole, and biotite. Common mafic rocks include ...
magma. The phenocryst compositions at Ciomadul are unlike these at other volcanoes in the Carpathians. The magmas derive from the
upper mantle The upper mantle of Earth is a very thick layer of rock inside the planet, which begins just beneath the crust (geology), crust (at about under the oceans and about under the continents) and ends at the top of the lower mantle (Earth), lower man ...
lithosphere A lithosphere () is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time ...
, which underwent
metasomatic Metasomatism (from the Greek μετά ''metá'' "change" and σῶμα ''sôma'' "body") is the chemical alteration of a rock by hydrothermal and other fluids. It is traditionally defined as metamorphism which involves a change in the chemical com ...
alteration. Compositionally, the tephras of Ciomadul have been subdivided into two groups, one called Tușnad‐type and the other Bixad‐type. A large proportion of crystals in the rocks consists of antecrysts and xenocrysts, making
radiometric dating Radiometric dating, radioactive dating or radioisotope dating is a technique which is used to Chronological dating, date materials such as Rock (geology), rocks or carbon, in which trace radioactive impurity, impurities were selectively incorporat ...
of the rocks difficult. These include
amphibole Amphibole ( ) is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is ...
,
biotite Biotite is a common group of phyllosilicate minerals within the mica group, with the approximate chemical formula . It is primarily a solid-solution series between the iron- endmember annite, and the magnesium-endmember phlogopite; more al ...
,
feldspar Feldspar ( ; sometimes spelled felspar) is a group of rock-forming aluminium tectosilicate minerals, also containing other cations such as sodium, calcium, potassium, or barium. The most common members of the feldspar group are the ''plagiocl ...
and
zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...
. The zircons formed almost continuously over hundred thousands of years within Ciomadul's magma chamber, indicating a steady crystallization of the chamber. Differences in magma temperature, crystal content and the participation of pre-existent crystal mushes determine whether an eruption will be effusive or explosive. The temperature of the
magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it u ...
has been estimated to be about , with heating of over occurring before some eruptions according to thermometry calculation. Volcanic activity was most likely triggered by the injection of
basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% ...
magma into the
felsic In geology, felsic is a grammatical modifier, modifier describing igneous rocks that are relatively rich in elements that form feldspar and quartz.Marshak, Stephen, 2009, ''Essentials of Geology,'' W. W. Norton & Company, 3rd ed. It is contrasted ...
magma chamber before the actual eruption, as has been observed at other silicic volcanoes around the world, but the magma chamber probably kept being recharged even between eruptions. The
amphibole Amphibole ( ) is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is ...
s in the rocks formed at depths of . The magma output of Ciomadul is about while magma chamber recharge may have reached .


Eruptive history

Ciomadul has been active for over half a million years, with the oldest activity between 1,000,000 and 750,000 years ago forming
lava dome In volcanology, a lava dome is a circular, mound-shaped protrusion resulting from the slow extrusion of viscous lava from a volcano. Dome-building eruptions are common, particularly in convergent plate boundary settings. Around 6% of eruptions ...
s. Older estimates indicate that activity did not start before 250,000 years ago, while more recent research indicated a start of volcanism over 600,000/ 850,000 years ago. Volcanism at Ciomadul consisted mostly of the extrusion of lava domes, their collapse forming block-and-ash flows and subplinian and Vulcanian eruptions separated by long periods of rest. The volcanic history of Ciomadul has been subdivided into an effusive phase that lasted until about 440,000 years ago and an explosive phase that began 200,000 years ago during which magma output increased 30-fold and which is known as "young Ciomad". An alternative description envisages an "old Ciomadul" between 1,000,000 — 300,000 years ago and a "young Ciomad eruptive period" between 160,000 — 30,000 years ago, with the latter in turn subdivided into five stages that emplaced about of rock. A gap of about 500,000 years separates Ciomadul from the activity of other volcanoes in the area. The two oldest dates of 1,020,000 and 850,000 years ago were obtained on peripheral lava domes. Early activity between 850,000 — 440,000 years ago built the southeastern domes. This effusive phase is also known as "old Ciomad", and eruptions were separated by long pauses without volcanic activity from each other. The dates obtained by potassium-argon dating are much older; there is substantial disagreement between dates obtained by potassium-argon dating or argon-argon dating on the one hand and uranium-thorium dating on the other hand at Ciomadul. These dates indicate that the formation of the central lava domes took place between 590,000 and 140,000 years ago. Around 200,000 — 130,000 or 150,000 — 100,000 years ago a number of lava domes developed.
Explosive eruption In volcanology, an explosive eruption is a volcanic eruption of the most violent type. A notable example is the 1980 eruption of Mount St. Helens. Such eruptions result when sufficient gas has dissolved under pressure within a Viscosity, viscous ...
s became common only about 57,000 years ago. Between 56,000 and 32,000 years ago, explosive activity occurred at Ciomadul. That timespan coincides with the deposition of
tephra Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...
from volcanoes in Italy in Europe; it is possible that tephra also came from Ciomadul. Indeed, the age of Ciomadul's last eruption overlaps with the age of the Campanian Ignimbrite.


Tephras

Ciomad has produced far-flung
tephra Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...
s, which reached as far as
Ukraine Ukraine is a country in Eastern Europe. It is the List of European countries by area, second-largest country in Europe after Russia, which Russia–Ukraine border, borders it to the east and northeast. Ukraine also borders Belarus to the nor ...
and have been recovered from the Ursului Cave of the Perșani Mountains. Some tephra layers found in two drilling cores of the
Black Sea The Black Sea is a marginal sea, marginal Mediterranean sea (oceanography), mediterranean sea lying between Europe and Asia, east of the Balkans, south of the East European Plain, west of the Caucasus, and north of Anatolia. It is bound ...
may have originated at Ciomad but reliably distinguishing between Ciomadul tephras and these from
Nisyros Nisyros, also spelled Nisiros (; ), is a volcanic Greek island and municipality located in the Aegean Sea. It is part of the Dodecanese group of islands, situated between the islands of Kos and Tilos. Its shape is approximately round, with a ...
and
Anatolia Anatolia (), also known as Asia Minor, is a peninsula in West Asia that makes up the majority of the land area of Turkey. It is the westernmost protrusion of Asia and is geographically bounded by the Mediterranean Sea to the south, the Aegean ...
n volcanoes is difficult. The Roxolany Tephra has been found as far as
Odesa Odesa, also spelled Odessa, is the third most populous List of cities in Ukraine, city and List of hromadas of Ukraine, municipality in Ukraine and a major seaport and transport hub located in the south-west of the country, on the northwestern ...
,
Ukraine Ukraine is a country in Eastern Europe. It is the List of European countries by area, second-largest country in Europe after Russia, which Russia–Ukraine border, borders it to the east and northeast. Ukraine also borders Belarus to the nor ...
, away from Ciomadul. If the Roxolany Tephra was formed by the youngest eruption of Ciomadul, the youngest eruption would have occurred 29,600 calibrated radiocarbon years ago based on independent dates of the tephra. From the other point of view, the clinopyroxene‐bearing Roxolany tephra was unlikely to be derived from Ciomadul, as it differs significantly from Ciomadul typical phenocryst assemblage containing amphibole. Based on new chronostratigraphic model for the Roxolany section, supported by updated magnetostratigraphic results and compiled existing radiocarbon and
optically stimulated luminescence In physics, optically stimulated luminescence (OSL) is a method for measuring doses from ionizing radiation. It is used in at least two applications: * Luminescence dating of ancient materials: mainly geological sediments and sometimes fired pot ...
dates, the Roxolany tephra was deposited around 143,800 years ago.


Recent explosive activity

Explosive activity may have occurred in two separate episodes, one 57,000/56,000–44,000 years ago and the other 34,000/33,000–29,000 years ago. An earlier explosive eruption about 55,900 ± 2,300 years ago may be the origin of the Mohoș crater, with another proposed potassium-argon date being 220,000 years ago. Mohoș crater is probably older than the Sfânta Ana crater. A phreatomagmatic deposit northeast of Mohoș was formed by an eruption of the Mohoș crater; this eruption may be the source of the "Turia type" phreatomagmatic deposits, which are dated to have occurred about 51,000 ± 4,800 years ago. In one view, a volcanically quiet period followed an effusive eruption 48,000 or 42,900 years ago named "Piscul Pietros" and lasted until 31,510 years ago, when a Plinian eruption occurred. This latter eruption deposited ash as far as from the vent at one site. Alternatively, 38,900 ± 1,700 years ago a subplinian eruption occurred at Ciomadul; it may have formed the Sfânta Ana crater. This date would correspond to that of the so-called "MK-202" tephra. Piscul Pietros has been also dated to be 48,000 ± 6,000 or 60,000 ± 5,000 years old. The age of the last eruption is controversial but probably took place about 30,000 years ago. In 1994,
radiocarbon Carbon-14, C-14, C or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic matter is the basis of the radiocarbon dating method pioneered by Willard Libby and coll ...
dating yielded an age of 10,700 ± 800 years
Before Present Before Present (BP) or "years before present (YBP)" is a time scale used mainly in archaeology, geology, and other scientific disciplines to specify when events occurred relative to the origin of practical radiocarbon dating in the 1950s. Because ...
from a
pyroclastic flow A pyroclastic flow (also known as a pyroclastic density current or a pyroclastic cloud) is a fast-moving current of hot gas and volcanic matter (collectively known as tephra) that flows along the ground away from a volcano at average speeds of b ...
. Later, paleosoils and other samples from the same flow were used to deduce similar ages of over 36,770, 42,650, over 35,670 and over 35,520 years before present, respectively. Thus this youngest age estimate was discarded. In 2010, further research identified two younger eruptions, one occurring 39,000 years Before Present and the other 27,500 years Before Present. Other data obtained by uranium-thorium dating indicate an age of 32,600 ± 1,000 years ago for the youngest eruption. Both of these eruptions took place at Sfânta Ana and imply a repose period between eruptions of over 10,000 years. Much older dates obtained by potassium-argon dating are not considered reliable. Alternatively, the latest eruption may have occurred at a
satellite vent A satellite or an artificial satellite is an object, typically a spacecraft, placed into orbit around a Astronomical object, celestial body. They have a variety of uses, including communication relay, weather forecasting, navigation (GPS), br ...
seeing as sedimentation of Lake Sfânta Ana has been ongoing since 26,000 years ago. These two recent eruptions were fed by different magmas, with the younger eruption coming from deeper
magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it u ...
s ( versus ) and involving more primitive magma. After the last eruption, the lava domes were subject to glacial
weathering Weathering is the deterioration of rocks, soils and minerals (as well as wood and artificial materials) through contact with water, atmospheric gases, sunlight, and biological organisms. It occurs '' in situ'' (on-site, with little or no move ...
, such as frost shattering that produced
stone run A stone run (called also ''stone river'', ''stone stream'' or ''stone sea''tephra Tephra is fragmental material produced by a Volcano, volcanic eruption regardless of composition, fragment size, or emplacement mechanism. Volcanologists also refer to airborne fragments as pyroclasts. Once clasts have fallen to the ground, ...
layers that might indicate more recent eruptions.


Current status

Presently, Ciomadul displays seismic activity, release of
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
from bubbling pools and bogs and mofettas and anomalous
heat flow Heat transfer is a discipline of thermal engineering that concerns the generation, use, conversion, and exchange of thermal energy (heat) between physical systems. Heat transfer is classified into various mechanisms, such as thermal conduction, ...
reaching . Outgassing of
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
,
hydrogen sulfide Hydrogen sulfide is a chemical compound with the formula . It is a colorless chalcogen-hydride gas, and is toxic, corrosive, and flammable. Trace amounts in ambient atmosphere have a characteristic foul odor of rotten eggs. Swedish chemist ...
and mostly
abiotic In biology and ecology, abiotic components or abiotic factors are non-living chemical and physical parts of the environment that affect living organisms and the functioning of ecosystems. Abiotic factors and the phenomena associated with them und ...
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...
have been found at Ciomadul, forming
sulfide Sulfide (also sulphide in British English) is an inorganic anion of sulfur with the chemical formula S2− or a compound containing one or more S2− ions. Solutions of sulfide salts are corrosive. ''Sulfide'' also refers to large families o ...
deposits in some caverns. The total output of
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
exceeds about per year, while the output of
methane Methane ( , ) is a chemical compound with the chemical formula (one carbon atom bonded to four hydrogen atoms). It is a group-14 hydride, the simplest alkane, and the main constituent of natural gas. The abundance of methane on Earth makes ...
amounts to per year. Carbon dioxide concentrations in some places such as caverns can be high enough to become dangerous to people and animals, and is reflected in place names - such as Peștera Ucigașă (Gyilkos-barlang) which mean "killer cave" while Puturosu means "stinky" - and local legends of a "gate to hell". Former
alum An alum () is a type of chemical compound, usually a hydrated double salt, double sulfate salt (chemistry), salt of aluminium with the general chemical formula, formula , such that is a valence (chemistry), monovalent cation such as potassium ...
and
sulfur Sulfur ( American spelling and the preferred IUPAC name) or sulphur ( Commonwealth spelling) is a chemical element; it has symbol S and atomic number 16. It is abundant, multivalent and nonmetallic. Under normal conditions, sulfur atoms ...
mines east of Ciomadul were abandoned due to the dangers from toxic gases. The carbon dioxide is accompanied by
noble gas The noble gases (historically the inert gases, sometimes referred to as aerogens) are the members of Group (periodic table), group 18 of the periodic table: helium (He), neon (Ne), argon (Ar), krypton (Kr), xenon (Xe), radon (Rn) and, in some ...
es derived from the mantle. The gases may come directly from the mantle, rather than from magma. At depths of and especially , a
magma chamber A magma chamber is a large pool of liquid rock beneath the surface of the Earth. The molten rock, or magma, in such a chamber is less dense than the surrounding country rock, which produces buoyant forces on the magma that tend to drive it u ...
has been identified beneath Ciomadul, based on magnetotelluric data, and several of magma may still be stored underneath Ciomadul. An alternative explanation is that there are less than a few cubic kilometres of magma. This magmatic reservoir appears to have about 5–15% of melt by volume fraction, with a vertical stratification by temperature. A deeper
basaltic Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% ...
melt zone may also exist at a depth of around . Further, a zone of low seismic velocity has been identified with geophysical and seismic modelling in the lower crust and upper mantle beneath Ciomad, down to depths of or .
Hydrothermal Hydrothermal circulation in its most general sense is the circulation of hot water (Ancient Greek ὕδωρ, ''water'',Liddell, H.G. & Scott, R. (1940). ''A Greek-English Lexicon. revised and augmented throughout by Sir Henry Stuart Jones. with th ...
activity has been noted at Ciomadul and Tușnad-Băi, including a high temperature system at depth with temperatures exceeding . The Tușnad-Băi springs have temperatures of and discharge salty,
carbon dioxide Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at norma ...
-rich water which emerges from pyroclastic deposits. They are used in
spa A spa is a location where mineral-rich spring water (sometimes seawater) is used to give medicinal baths. Spa health treatments are known as balneotherapy. The belief in the curative powers of mineral waters and hot springs goes back to pre ...
s in the area. In one cave, autotropic bacterial
biofilm A biofilm is a Syntrophy, syntrophic Microbial consortium, community of microorganisms in which cell (biology), cells cell adhesion, stick to each other and often also to a surface. These adherent cells become embedded within a slimy ext ...
s have been found which subsist on the exhaled gases or the sulfur deposits.


Future activity

Volcanoes are usually considered to be active if they have had eruptions during the
Holocene The Holocene () is the current geologic time scale, geological epoch, beginning approximately 11,700 years ago. It follows the Last Glacial Period, which concluded with the Holocene glacial retreat. The Holocene and the preceding Pleistocene to ...
. However, as demonstrated by the unexpected eruption of Chaiten volcano in
Chile Chile, officially the Republic of Chile, is a country in western South America. It is the southernmost country in the world and the closest to Antarctica, stretching along a narrow strip of land between the Andes, Andes Mountains and the Paci ...
in May 2008, even long-inactive volcanoes can become active again. Such volcanoes can constitute a threat to regions with seemingly quiet volcanism. Ciomadul has had repose periods that lasted longer than the timespan elapsed since the last eruption.
Zircon Zircon () is a mineral belonging to the group of nesosilicates and is a source of the metal zirconium. Its chemical name is zirconium(IV) silicate, and its corresponding chemical formula is Zr SiO4. An empirical formula showing some of th ...
crystallization data imply that the magma chambers of Ciomadul were active over time spans of over 300,000 years. Uniquely, Ciomadul is a still alive volcano in Eastern Europe and its craters have a youthful appearance. There is always the possibility of renewed volcanic activity if the magma chamber has not solidified even if there is no positive evidence of ongoing magma generation. Deep earthquake activity at Ciomadul occurs down to a depth of , indicating that the volcanic system between the magma chamber and lithospheric melts is still active. It is considered to be a potentially active volcano although the risk of impending eruptions has been greatly exaggerated by
sensationalist In journalism and mass media, sensationalism is a type of editorial tactic. Events and topics in news stories are selected and worded to excite the greatest number of readers and viewers. This style of news reporting encourages biased or emotiona ...
media. Potential eruptions may be heralded by seismic swarms caused by the ascent of magma, followed by deformation of the edifice and degassing in the last weeks and hours before the eruption.


Climate and vegetation

Ciomadul is located in a
temperate climate In geography, the temperate climates of Earth occur in the middle latitudes (approximately 23.5° to 66.5° N/S of the Equator), which span between the tropics and the polar regions of Earth. These zones generally have wider temperature ra ...
zone. Rainfall reaches , resulting in strong erosion. The annual mean temperature is at Sfântu Gheorghe, the nearest
meteorological station A weather station is a facility, either on land or sea, with instruments and equipment for measuring atmospheric conditions to provide information for weather forecasts and to study the weather and climate. The measurements taken include tempera ...
. Around Sfânta Ana, July mean temperatures are and January temperatures are . While some
glaciation A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate be ...
occurred in the Carpathians during the
ice age An ice age is a long period of reduction in the temperature of Earth's surface and atmosphere, resulting in the presence or expansion of continental and polar ice sheets and alpine glaciers. Earth's climate alternates between ice ages, and g ...
s, no glacial activity is recorded at Ciomadul. The volcano was unforested at that time, with
steppe In physical geography, a steppe () is an ecoregion characterized by grassland plains without closed forests except near rivers and lakes. Steppe biomes may include: * the montane grasslands and shrublands biome * the tropical and subtropica ...
and
tundra In physical geography, a tundra () is a type of biome where tree growth is hindered by frigid temperatures and short growing seasons. There are three regions and associated types of tundra: #Arctic, Arctic, Alpine tundra, Alpine, and #Antarctic ...
vegetation comprising most of the reported flora.
Drill core A modern core drill is a drill specifically designed to remove a cylinder of material, much like a hole saw. The material left inside the drill bit is referred to as the ''core''. Core drills used in metal are called annular cutters. Core d ...
s from the Mohoș peat bog have been used to reconstruct the past climate and hydrology of the area. Ciomadul is covered by
beech Beech (genus ''Fagus'') is a genus of deciduous trees in the family Fagaceae, native to subtropical (accessory forest element) and temperate (as dominant element of Mesophyte, mesophytic forests) Eurasia and North America. There are 14 accepted ...
and
spruce A spruce is a tree of the genus ''Picea'' ( ), a genus of about 40 species of coniferous evergreen trees in the family Pinaceae, found in the northern temperate and boreal ecosystem, boreal (taiga) regions of the Northern hemisphere. ''Picea'' ...
forests. Around Lake Sfânta Ana, the vegetation consists mostly of ''
Fagus sylvatica ''Fagus sylvatica'', the European beech or common beech, is a large, graceful deciduous tree in the Fagaceae, beech family with smooth silvery-gray bark, large leaf area, and a short trunk with low branches. Description ''Fagus sylvatica'' i ...
'' (common beech) and ''
Picea abies ''Picea abies'', the Norway spruce or European spruce, is a species of spruce native to Northern Europe, Northern, Central Europe, Central and Eastern Europe. It has branchlets that typically hang downwards, and the largest cones of any spruce, ...
'' (Norway spruce) woods. Other trees include ''
Acer platanoides ''Acer platanoides'', commonly known as the Norway maple, is a species of maple native to eastern and central Europe and western Asia, from Spain east to Russia, north to southern Scandinavia and southeast to northern Iran. It was introduced to ...
'' (Norway maple), ''
Betula pendula ''Betula pendula'', commonly known as silver birch, warty birch, European white birch, or East Asian white birch, is a species of tree in the family (biology), family Betulaceae, native plant, native to Europe and parts of Asia, though in so ...
'' (silver birch), ''
Carpinus betulus Hornbeams are hardwood trees in the plant genus ''Carpinus'' in the family Betulaceae. Its species occur across much of the temperateness, temperate regions of the Northern Hemisphere. Common names The common English name ''hornbeam'' derives ...
'' (common hornbeam), ''
Pinus sylvestris ''Pinus sylvestris'', the Scots pine (UK), Scotch pine (US), Baltic pine, or European red pine is a species of tree in the pine family Pinaceae that is native plant, native to Eurasia. It can readily be identified by its combination of fairly s ...
'' (Scots pine), ''
Salix caprea ''Salix caprea'', known as goat willow, pussy willow or great sallow, is a common species of willow native to Europe and western and central Asia.Meikle, R. D. (1984). ''Willows and Poplars of Great Britain and Ireland''. BSBI Handbook 4. . De ...
'' (goat willow) and ''
Salix cinerea ''Salix cinerea'' (common sallow, grey sallow, grey willow, grey-leaved sallow, large grey willow, pussy willow, rusty sallow) is a species of willow native to Europe and western Asia.Meikle, R. D. (1984). ''Willows and Poplars of Great Britain ...
'' (grey willow). A
fen A fen is a type of peat-accumulating wetland fed by mineral-rich ground or surface water. It is one of the main types of wetland along with marshes, swamps, and bogs. Bogs and fens, both peat-forming ecosystems, are also known as mires ...
contains '' Carex lasiocarpa'' (slender sedge), ''
Carex rostrata ''Carex rostrata'', the bottle sedge or beaked sedge, is a perennial species of sedge in the family Cyperaceae. Range and habitat The species is native to Holarctic fens and can be found in Canada and the northern part of the United States, and ...
'' (bottle sedge), '' Lysimachia thyrsiflora'' (tufted loosestrife) and '' Sphagnum angustifolium'' (fine bogmoss). At Mohoș, vegetation consists of ''
Alnus glutinosa ''Alnus glutinosa'', the common alder, black alder, European alder, European black alder, or just alder, is a species of tree in the family (biology), family Betulaceae, native plant, native to most of Europe, southwest Asia and northern Africa. ...
'' (common alder), ''
Betula pendula ''Betula pendula'', commonly known as silver birch, warty birch, European white birch, or East Asian white birch, is a species of tree in the family (biology), family Betulaceae, native plant, native to Europe and parts of Asia, though in so ...
'' and ''
Salix Willows, also called sallows and osiers, of the genus ''Salix'', comprise around 350 species (plus numerous hybrids) of typically deciduous trees and shrubs, found primarily on moist soils in cold and temperate regions. Most species are known ...
''. The peat bog contains trees (''
Pinus sylvestris ''Pinus sylvestris'', the Scots pine (UK), Scotch pine (US), Baltic pine, or European red pine is a species of tree in the pine family Pinaceae that is native plant, native to Eurasia. It can readily be identified by its combination of fairly s ...
'' and ''
Betula pubescens ''Betula pubescens'' (syn. ''Betula alba''), commonly known as downy birch and also as moor birch, white birch, European white birch or hairy birch, is a species of deciduous tree, native and abundant throughout northern Europe and northern Asia ...
'' (downy birch)) and
Ericaceae The Ericaceae () are a Family (biology), family of flowering plants, commonly known as the heath or heather family, found most commonly in acidic and infertile growing conditions. The family is large, with about 4,250 known species spread acros ...
. The region of the volcano is a
Site of Community Importance A Site of Community Importance (SCI) is defined in the European Commission Habitats Directive (92/43/EEC) as a site which, in the biogeographical region or regions to which it belongs, contributes significantly to the maintenance or restoration at ...
and some endangered plant species have been identified in the Mohoș bog.


References


Bibliography

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External links

{{Commons category, Ciomad, Ciomadul Pleistocene lava domes Volcanoes of Romania Landforms of Romania Natural history of Romania Geography of Harghita County Dormant volcanoes