5130 x 3420 px | 43,4 x 29 cm | 17,1 x 11,4 inches | 300dpi
Data acquisizione:
2008
Ubicazione:
baratang island,andaman,india,asia
Altre informazioni:
A mud volcano started erupting at Baratang Island, Middle Andamans, India on 18th February 2003. There was a minor fissure eruption at the same site before 1983. This type of fissures are common at Baratang through which mud and gas constantly seeps out. The last major eruption occurred in March, 1983, which was of larger magnitude compared to the recent eruption. The present eruption covers an area of 1, 000 sq m to 1, 200 sq m and has resulted in the formation of the sub-circular mound of about 30 m in diameter and height of about 2 m at the center. The main crater is submerged under grey coloured, solidified mud. Emission of a colourless gas with sulphurous smell was noted along with grey, dark grey to bluish grey coloured viscous mud. The ejected viscous mud also contains angular to sub-rounded rock fragments consisting of sandstone, red and green coloured shales, quartz-calcite vein fragments and crystals of cubic pyrite from the underlying strata. The island of Baratang, part of the Great Andaman archipelago (India) in the Andaman Islands, Indian Ocean has several sites of mud volcanic activity. The most recent significant eruption event was in 2003.Mud volcanoes are eruption of mud containing hydrocarbon fluids, gases (methane, carbon dioxide, nitrogen) and acidic liquids with suspended fine sediment. These are more akin to mud diapirs formed by pressurised mud slarry. The muddy material below ground are squeezed upward by compressive forces and expelled at the surface along zones of weakness. Viscosity of the ejected mud ‘lava’ depends on the content of the water, gas and/or oil content of the source rock/ clay. Mud volcanoes are often associated with accretionary prism in subduction zones, petroleum deposits and in orogenic belt. Internal forces below the earth's surface causing mud volcanoes include tectonic disturbance, compression of clays and differences in density and thickness of sediments. Hydrocarbon gases are often associated.
