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A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which dissolved carbon dioxide (CO2) suddenly erupts from deep lake water, suffocating wildlife, livestock and humans. Such an eruption may also cause tsunamis in the lake as the rising CO2 displaces water. Scientists believe earthquakes, volcanic activity, or explosions can trigger such an eruption. Lakes in which such activity occurs may be known as ''limnically active lakes'' or ''exploding lakes''. Some features of limnically active lakes include: *CO2-saturated incoming water *A cool lake bottom indicating an absence of direct volcanic interaction with lake waters *An upper and lower thermal layer with differing CO2 saturations *Proximity to areas with volcanic activity Scientists have recently determined, from investigations into the mass casualties in the 1980s at Lake Monoun and Lake Nyos, that although limnic eruptions can be indirectly related to volcanic eruptions, they are actually separate types of disaster events.〔(Volcanic Lakes and Gas Releases ) USGS/(Cascades Volcano Observatory ), Vancouver, Washington.〕 == Historical occurrences == To date, this phenomenon has been observed only twice. The first was in Cameroon at Lake Monoun in 1984, causing the asphyxiation and death of 38 people living nearby. A second, deadlier eruption happened at neighbouring Lake Nyos in 1986, this time releasing over 80 million cubic meters of CO2 and killing around 1,700 people and 3,500 livestock, again by asphyxiation. Due to the nature of the event, it is hard to determine if limnic eruptions have happened elsewhere. A third lake, Lake Kivu, exists on the border between the Democratic Republic of the Congo and Rwanda, and contains massive amounts of dissolved CO2. Sample sediments from the lake were taken by professor Robert Hecky from the University of Michigan, which showed that an event caused living creatures in the lake to go extinct approximately every thousand years, and caused nearby vegetation to be swept back into the lake. Limnic eruptions can be measured on a scale using the concentration of CO2 in the surrounding area. The Messel pit fossil deposits of Messel, Germany, show evidence of a limnic eruption there in the early Eocene. Among the victims are perfectly preserved insects, frogs, turtles, crocodiles, birds, anteaters, insectivores, early primates and paleotheres. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Limnic eruption」の詳細全文を読む スポンサード リンク
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