Yanar Dag(Azerbaijani: Yanar Dağ, translated as “burning mountain”), is a natural gas fire which blazes continuously on a hillside on the Absheron Peninsula on the Caspian Sea near Baku, the capital of Azerbaijan, which itself is known as the “land of fire.” Flames jet into the air 3 metres (9.8 ft) from a thin, porous sandstone layer.
Yanar Dag is known by other names such as “pilpila”, “bozdagh”, “ahtarma” and “gaynarja.” Unlike mud volcanoes, the Yanar Dag flame burns fairly steadily, as it involves a steady seep of gas from the subsurface. It is claimed that the Yanar Dag flame was only noted when accidentally lit by a shepherd in the 1950s. There is no seepage of mud or liquid, which distinguishes it from the nearby mud volcanoes of Lökbatan or Gobustan.
The Yanar Dag fire is never extinguished. Around this open fireplace the atmosphere is filled with the smell of gas. The flames emanate from vents in sandstone formations and rise to a height of 10 metres (33 ft) (different figures are mentioned in other references) at the base of a 10-metre (33 ft)-wide scarp below a hillside. Yanar Dag is described by the Geological Survey of Azerbaijan as “Intensive flames, to 1 metre (3 ft 3 in) high, develop for 15 metres (49 ft) along the base of a 2–4 metres (6 ft 7 in–13 ft 1 in) high and 200 metres (660 ft) long tectonic scarp.” The surface flames result from the steady gas emissions from underlying soils.
Even the surface of streams near Yanar Dag fire can be ignited with a match. These streams, which otherwise appear calm, are known as Yanar Bulaq: “burning springs.” There are several such springs in the vicinity of the Vilascay River, where the local people take curative baths.