page_title: Ciomadul
section_title: Volcano
hierarchical_section_title: Ciomadul / Geography and geology / Volcano
caption_attribution_description: A Mohos-tőzegláp photo taken by uploader User:Csanády in 2006.
context_page_description: Ciomadul is a volcano in Romania, and is known as Csomád in Hungarian. It is in the Carpathians, close to the towns of Băile Tușnad and Bixad. It is part of a volcanic chain known as the Călimani – Gurghiu – Harghita chain and lies at its southeastern end. Ciomadul consists of several lava domes with two embedded explosion craters known as Mohos and St. Ana, the latter of which contains a crater lake, Lake Sfânta Ana. The dominant volcanic rock at Ciomadul is potassium-rich dacite.
  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 St. Ana and Mohos 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 strength, ejecting volcanic ash as far as the Black Sea.
  The last eruption took place between 32,600 and 27,500 years ago. Its date is likewise unclear.
context_section_description: Ciomadul is located in the southeastern Carpathians, at the end of the Călimani (Kelemen) – Gurghiu (Görgényi) – Harghita (Hargita) volcanic chain, and is also known as Ciomadu. The gorge of the Olt River 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 Mohos swamp to the St. Ana lake. The basement of the volcano is formed by flysch of Cretaceous age and by older volcanics; in some places volcanic rocks overlie fluvial deposits.
  The idea that Ciomadul could be a still active volcano was first proposed in 1780 on the basis of its young appearance and the release of gas. While a publication in 1964 postulated that the tuffs of Ciomadul were reworked Pliocene volcanites, the late Pleistocene age was established soon afterwards.
  Ciomadul is formed by a complex of lava domes and other volcanic material that form a south-tilting ridge that rises above the 700 metres (2,300 ft) high surrounding Lower Ciuk Basin. Individual lava domes form cone-shaped hills, which reach heights of 300–400 metres (980–1,310 ft) and widths of 1–2 kilometres (0.62–1.24 mi). Individual domes include Haramul Ierbos (Fű-Haram in Hungarian), Haramul Mare (Nagy-Haram), Haramul Mic (Kis-Haram), Vf. Cetăţii (Vár-tető), Vf. Comloş (Komlós-tető), Vf. Surduc (Szurdok-tető) and Dealul Mare southeast from the main complex. The central cluster of domes is elliptical. The highest point of the complex is Ciomadul Mare (Nagy-Csomád) with an altitude of 1,301 metres (4,268 ft). Some domes were later affected by erosion, explosive activity or fumarolic alteration. The whole volcanic complex covers a surface area of 80 square kilometres (31 sq mi), and is surrounded by a circular/semicircular plain made of volcanic debris.
   
  The lava dome complex contains two craters, named Mohos and St. Ana. They were formed in the previously existing lava domes. The St. Ana crater is c. 1,600 metres (5,200 ft) wide and c. 200 metres (660 ft) deep beneath the rim, comparable with the crater of El Chichón volcano in Mexico. This crater lacks a breach and is relatively unaffected by erosion. It contains a 6 metres (20 ft) deep crater lake, which once may have been over 12 metres (39 ft) deep. This c. 189.9 square kilometres (73.3 sq mi) large lake is known as Lake Sfânta Ana (46°07′35″N 25°53′17″E) and lies at an altitude of 946 metres (3,104 ft).
  The Mohos crater lies at an altitude of 1,050 metres (3,440 ft). It is larger than St. Ana with a diameter of 1.9 kilometres (1.2 mi) and not as deep. with its bottom lying  above sea level. It is filled with a 800,000 square metres (80 ha) large and 10 metres (33 ft) thick Sphagnum peat bog and its rim is cut by the St. Ana crater. 
  Unlike St. Ana, the Mohos crater has been breached by erosion, causing the formation of an outlet valley. Both craters were formed by explosive eruptions and distinguishing between the deposits of both is difficult. The existence of an even larger crater with a diameter 2–2.5 kilometres (1.2–1.6 mi) has been suggested, encompassing both St. Ana and Mohos.
  Pyroclastic flow deposits generated by Ciomadul have been found on its northeastern, southern and western slopes. They reach a distance of as much as 25 kilometres (16 mi) from the volcano. At Tusnad road, one of the flows has a thickness of c. 10 metres (33 ft). Tephra fall bed, lapilli, and surge deposits are also found, and the flow deposits contain pumice blocks. One lapilli layer, 20–23 centimetres (7.9–9.1 in) thick, from Ciomadul has been identified 40 kilometres (25 mi) 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 St. Ana Phreatomagmatic Activity". Each comprise a number of individual tephra layers.
  Other landforms at Ciomadul include coulees and lava flows. The total volume of the complex is about 8–15 cubic kilometres (1.9–3.6 cu mi) dense rock equivalent. Drilling has identified the exis
caption: Peat bog in Mohos crater
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