Lake Nyos
A clouded Lake Nyos, silty after a limnic eruption.
Coordinates	6.44° N 10.30° E
Lake type	Meromictic
Basin countries	Cameroon
Max-length	2.0 km
Max-width	1.2 km
Surface area	1.58 km²
Average depth	208 m

Lake Nyos is a crater lake in the Northwest Province of Cameroon, located at 6.44° N 10.30° E. Nyos is a deep lake high on the flank of an inactive volcano near Mount Oku, along the Cameroon line of volcanic activity. A natural dam of volcanic rock hems in the lake waters. Image File history File links Download high resolution version (1125x755, 43 KB)http://shagging. ... Silt is soil or rock derived granular material of a specific grain size. ... A cow suffocated by gasses from Lake Nyos A limnic eruption, also referred to as a lake overturn or exploding lake, is a rare type of natural disaster in which CO2 suddenly erupts from deep lake water, posing the threat of suffocating wildlife, livestock and humans. ... A man-made lake in Keukenhof, Netherlands A lake is a body of water or other liquid of considerable size surrounded by land. ... A meromictic lake has layers of water which do not intermix. ... A drainage basin is the area within the drainage basin divide (yellow outline), and drains the surface runoff and river discharge (blue lines) of a contiguous area. ... View from the rim The Old Man of the Lake (with extreme clarity of water apparent) Crater Lake is a lake in the U.S. state of Oregon that is 5 by 6 miles (8 by 9. ... The Northwest Province (Nord-Ouest) is the third most populated province in Cameroon. ... Volcano 1. ... The Cameroon line is a geologic fault that runs northeast from the Atlantic Ocean into Cameroon. ... Scrivener Dam, in Canberra, Australia, was engineered to withstand a once-in-5000-years flood A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment. ... Ignimbrite is a deposit of a pyroclastic flow. ...

A pocket of magma lies beneath the lake and leaks carbon dioxide (CO₂) into the waters. Nyos is one of only three known lakes to be saturated with carbon dioxide in this way, the others being Lake Monoun, at a distance of 100 km SSE, and Lake Kivu in Rwanda. On 21 August 1986, the lake emitted a large cloud of CO₂ in a limnic eruption, which suffocated up to 1,800 people and 3,500 livestock in nearby villages. In response, scientists proposed that five tubes be lowered into the lake to allow gas to pass freely to the surface. To date, only one of these has been built. Magma is molten rock located beneath the surface of the Earth (or any other rocky planet), and which often collects in a magma chamber. ... Carbon dioxide is a chemical compound composed of one carbon and two oxygen atoms. ... Lake Monoun is a lake in West Province, Cameroon that lies in the Oku Volcanic Field. ... Lake Kivu forms part of the border of Rwanda and the Democratic Republic of Congo Satellite image of Lake Kivu courtesy of NASA. Lakeside in Rwanda Lake Kivu is one of the Great Lakes of Africa. ... August 21 is the 233rd day of the year (234th in leap years) in the Gregorian Calendar. ... 1986 (MCMLXXXVI) was a common year starting on Wednesday of the Gregorian calendar. ... A cow suffocated by gasses from Lake Nyos A limnic eruption, also referred to as a lake overturn or exploding lake, is a rare type of natural disaster in which CO2 suddenly erupts from deep lake water, posing the threat of suffocating wildlife, livestock and humans. ... Suffocation redirects here, for the band, see Suffocation (band). ...

Today, the lake also poses a threat due to its weakening natural wall. A geological tremor could cause this dike to give way, allowing water to rush into downstream villages all the way into Nigeria. Afsluitdijk, a 32 km dike in the Netherlands. ...

Formation and geological history

Lake Nyos fills a roughly circular maar in the Oku Volcanic Field, an explosion crater caused when a lava flow interacted violently with groundwater. The maar is believed to have formed in an eruption about 400 years ago, and is 1,800 m (5,900 feet) across and 208 m (682 feet) deep^[1]. The area has been volcanically active for millions of years —- after South America and Africa were split apart by plate tectonics about 110 million years ago, West Africa also experienced rifting, although to a lesser degree. The rift is known as the Mbéré Rift Valley, and crustal extension has allowed magma to reach the surface along a line extending through Cameroon. Mount Cameroon also lies on this fault line. Lake Nyos is surrounded by old lava flows and pyroclastic deposits. Ukinrek Maars, Alaska; the result of a 10-day eruption in 1977. ... In computer programming jargon, lava flow is a problem in which computer code, usually written under less than optimal conditions, is put into production and then built on when still in a developmental state. ... Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of geologic formations. ... South America South America is a continent crossed by the equator, with most of its area in the Southern Hemisphere. ... A world map showing the continent of Africa. ... Bridge across the Álfagjá rift valley in southwest Iceland, the boundary of the Eurasian and North American continental tectonic plates. ...  Western Africa (UN subregion)  Maghreb West Africa or Western Africa is the westernmost region of the African continent. ... The Mbéré Rift Valley is a rift valley in western Africa, running diagonally through São Tomé and Príncipe, Cameroon, the southeastern edge of Nigeria, and the southwestern edge of Chad. ... Earth cutaway from core to exosphere. ... Magma is molten rock located beneath the surface of the Earth (or any other rocky planet), and which often collects in a magma chamber. ... Mount Cameroon (also known as Cameroon Mountain or Fako) is an active volcano in Cameroon, near the Gulf of Guinea and is part of a general area of volcanic activity the Cameroon Volcanic Line, which also includes Lake Nyos, the site of the 1986 Lake Nyos tragedy. ... Pyroclastic flows sweep down the flanks of Mayon Volcano, Philippines, in 1984 Pyroclastic flows are a common and devastating result of some volcanic eruptions. ...

The lake waters are held in place by a natural dam composed of volcanic rock. At its narrowest point, the wall measures 40 metres high and 45 metres wide. Scrivener Dam, in Canberra, Australia, was engineered to withstand a once-in-5000-years flood A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment. ... Ignimbrite is a deposit of a pyroclastic flow. ...

Gas saturation

Lake Nyos is one of only three lakes in the world known to be saturated with carbon dioxide -- the others are Lake Monoun, also in Cameroon about 100 km away, and Lake Kivu in Rwanda. A magma chamber beneath the region is an abundant source of carbon dioxide, which seeps up through the lake bed, charging the waters of Lake Nyos with an estimated 90 million tonnes of CO₂ Lake Monoun is a lake in West Province, Cameroon that lies in the Oku Volcanic Field. ... Lake Kivu forms part of the border of Rwanda and the Democratic Republic of Congo Satellite image of Lake Kivu courtesy of NASA. Lakeside in Rwanda Lake Kivu is one of the Great Lakes of Africa. ... A magma chamber is a chamber typically between 1 km and 10 km beneath the surface of the Earth formed as rising magma forms a reservoir if it is unable to rise any further. ... A tonne or metric ton (symbol t), sometimes referred to as a metric tonne, is a measurement of mass equal to 1,000 kilograms. ...

Lake Nyos is thermally stratified, with layers of warm, less dense water near the surface floating on the colder, denser water layers near the lake's bottom. Over long periods, carbon dioxide gas seeping into the cold water at the lake's bottom is dissolved in great amounts.

Most of the time, the lake is stable and the CO₂ remains in solution in the lower layers. However, over time the water becomes supersaturated, and if an event such as an earthquake or volcanic eruption occurs, large amounts of CO₂ may suddenly come out of solution. The term supersaturation refers to a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances. ... An earthquake is a phenomenon that results from the sudden release of stored energy in the Earths crust that creates seismic waves. ... This article is about volcanoes in geology. ...

The 1986 disaster

A cow suffocated by gases from Lake Nyos

Although a sudden outgassing of CO₂ had occurred at Lake Monoun in 1984, killing 37 local residents, a similar threat from Lake Nyos was not anticipated. However, on August 21, 1986, a limnic eruption occurred at Lake Nyos which triggered the sudden release of about 1.6 million tonnes of CO₂. The gas rushed down two nearby valleys, displacing all the air and suffocating up to 1,800 people within 20 km of the lake, mostly rural villagers, as well as 3,500 livestock. About 4,000 inhabitants fled the area, and many of these developed respiratory problems, burns, and paralysis as a result of the gases. Cow killed by Lake Nyos gasses. ... Cow killed by Lake Nyos gasses. ... Lake Monoun is a lake in West Province, Cameroon that lies in the Oku Volcanic Field. ... 1984 (MCMLXXXIV) was a leap year starting on Sunday of the Gregorian calendar. ... August 21 is the 233rd day of the year (234th in leap years) in the Gregorian Calendar. ... 1986 (MCMLXXXVI) was a common year starting on Wednesday of the Gregorian calendar. ... A cow suffocated by gasses from Lake Nyos A limnic eruption, also referred to as a lake overturn or exploding lake, is a rare type of natural disaster in which CO2 suddenly erupts from deep lake water, posing the threat of suffocating wildlife, livestock and humans. ... A tonne or metric ton (symbol t), sometimes referred to as a metric tonne, is a measurement of mass equal to 1,000 kilograms. ...

It is not known what triggered the catastrophic outgassing. Most geologists suspect a landslide, but some believe that a small volcanic eruption may have occurred on the bed of the lake. A third possibility is that cool rainwater falling on one side of the lake triggered the overturn. Whatever the cause, the event resulted in the rapid mixing of the supersaturated deep water with the upper layers of the lake, where the reduced pressure allowed the stored CO₂ to effervesce out of solution. Effervesence from soda. ...

It is believed that up to a cubic kilometre of gas was released. Because CO₂ is denser than air, the gas flowed off the mountainous flank in which Lake Nyos rests and down two adjoining valleys in a layer tens of metres deep, displacing the air and suffocating all the people and animals before it could dissipate. The normally blue waters of the lake turned a deep red after the outgassing, due to iron-rich water from the deep rising to the surface and being oxidised by the air. The level of the lake dropped by about a metre, representing the volume of gas released. The outgassing probably also caused an overflow of the waters of the lake. Trees near the lake were knocked down. A cubic kilometre (symbol km³) is an SI derived unit of volume. ... Layers of Atmosphere (NOAA) Air redirects here. ... General Name, Symbol, Number iron, Fe, 26 Chemical series transition metals Group, Period, Block 8, 4, d Appearance lustrous metallic with a grayish tinge Atomic mass 55. ...

Degassing

French scientists working on degassing Lake Nyos.

The scale of the disaster led to much study on how a similar occurrence could be prevented. Estimates of the rate of carbon dioxide entering the lake suggested that outgassings could occur every 10-30 years, though a recent study shows that release of water from the lake, caused by erosion of the natural barrage that keeps in the lake's water, could in turn reduce pressure on the lake's carbon dioxide and cause a gas escape much sooner. Image File history File links Granted permission to use as long as a link to the owners website is provided. ... Image File history File links Granted permission to use as long as a link to the owners website is provided. ...

The solution proposed by scientists was that five pipes should be extended into the lower regions of the lake, allowing a controlled and continuous outgassing. International efforts have since installed one of these, which runs from the surface anchored to a raft that allows the deeper areas of the lake to release their CO₂ to the surface in controlled small amounts. It is hoped this will reduce the maximum levels of CO₂ in the future, and prevent any possibility of the lake turning over. Degassing began in 2001 and is continuing steadily. Traditional raft, from 1884 edition Huckleberry Finn and Jim Children successfully test their raft, in Brixham harbour, south Devon, England. ...

Following the Lake Nyos tragedy, scientists investigated other African lakes to see if a similar phenomenon could happen elsewhere. Lake Kivu in Rwanda, 2000 times larger than Lake Nyos, was found also to be supersaturated, and geologists found evidence for outgassing events around the lake about every thousand years. The eruption of nearby Mount Nyiragongo in 2002 sent lava flowing into the lake, raising fears that a gas eruption could be triggered, but fortunately it was not, as the flow of lava stopped well before it got near the bottom layers of the lake where the gas is. Lake Kivu forms part of the border of Rwanda and the Democratic Republic of Congo Satellite image of Lake Kivu courtesy of NASA. Lakeside in Rwanda Lake Kivu is one of the Great Lakes of Africa. ... Mount Nyiragongo is a volcano in the Virunga Mountains associated with the Great Rift Valley. ... For album titles with the same name, see 2002 (album). ... Look up lava, Aa, pahoehoe in Wiktionary, the free dictionary. ...

Weakening dam

On 18 August 2005, Dr. Isaac Njilah, a geologist at the University of Yaoundé, suggested that the natural dam of volcanic rock that keeps in the lake's waters could collapse in the near future. Erosion has worn the dam away, causing holes and pockets to develop in the dam's upper layer, and water already passes through the lower section. Meanwhile, landslides have reduced dam strength on the outside. Seismic activity caused by the lake's volcanic foundation could thus cause the lake wall to give way, resulting in up to 50 million cubic metres of water flooding downhill into areas of the Northwest Province and the Nigerian states of Taraba and Benue. Dr. Njilah estimates that the area is home to more than 10,000 people. August 18 is the 230th day of the year (231st in leap years) in the Gregorian calendar. ... 2005 (MMV) was a common year starting on Saturday of the Gregorian calendar. ... The University of Yaoundé is a leading university in Cameroon, located in Yaoundé. It was built with the help of France and opened in 1962 as the Federal University of Yaoundé, dropping the Federal in 1972 when the country was reorganized. ... Scrivener Dam, in Canberra, Australia, was engineered to withstand a once-in-5000-years flood A dam is a barrier across flowing water that obstructs, directs or retards the flow, often creating a reservoir, lake or impoundment. ... Ignimbrite is a deposit of a pyroclastic flow. ... Severe soil erosion in a wheat field near Washington State University, USA. For erosion as understood by materials science, see Erosion (materials science) For erosion as an English analogy, see Erosion (figurative) Erosion is the displacement of solids (soil, mud, rock and other particles) by the agents of wind, water... Binomial name Taraba major Vieillot, 1816 The Great Antshrike, Taraba major, is a passerine bird in the antbird family. ... The Benue River or Bénoué River is the major tributary of the River Niger. ...

The Cameroonian government, speaking through Dr. Gregory Tanyi-Leke of the Institute of Mining and Geological Research, acknowledges the weakening wall but denies that it presents any immediate threat. A United Nations team led by Olaf Van Duin and Nisa Nurmohamed of the Netherlands Ministry of Transport and Public Works inspected the dam over three days in September 2005 and confirmed that the natural lip had weakened. Van Duin believes that the dam will breach in the next 10 or 20 years. The United Nations (UN) is an international organization whose stated aims are to facilitate cooperation in international law, international security, economic development, social progress and human rights issues. ...

One possible means of averting such a catastrophe would be to strengthen the lake wall, though this would take much time and money. Engineers could also introduce a channel to allow excess water to drain; if the water level were lowered by about 20 metres, the pressure on the wall would be reduced significantly.

See also

• Henry's Law
• Raoult's law
• Lake Monoun

In chemistry, Henrys law is one of the gas laws. ... In chemistry, Raoults law states that the vapor pressure of mixed liquids is dependent on the vapor pressures of the individual liquids and the molar vulgar fraction of each present in solution. ... Lake Monoun is a lake in West Province, Cameroon that lies in the Oku Volcanic Field. ...

References

• "Cameroon scientist denies dam about to collapse" (23 August 2005). Reuters.
• Cotel A (1999), A trigger mechanism for the Lake Nyos disaster, American Physical Society, Division of Fluid Dynamics Meeting, November 21-23, 1999
• Decker, R. and Decker, B. (1997) Volcanoes, 3rd edition, WH Freeman, New York.
• Musa, Tansa (28 September 2005). "Cameroon dam could collapse in 10 years-UN experts". Reuters.
• Musa, Tansa (18 August 2005). "Cameroon dam nears collapse, 10,000 lives at risk". Reuters.
• Sano Y., Kusakabe M., Hirabayashi J. et al (1990), Helium and carbon fluxes in Lake Nyos, Cameroon: constraint on next gas burst, Earth and Planetary Science Letters, v. 99, p. 303-314
• Sano Y., Wakita H., Ohsumi T., Kusakabe M. (1987), Helium isotope evidence for magmatic gases in Lake Nyos, Cameroon, Geophysical Research Letters, v. 14, p. 1039-1041
• Scripts/W%FCest_Schmid_DD_Nyos_FM9_12626.pdf Lake Nyos Research

External links

• Lake Nyos incident
• Lake Nyos research
• BBC News 'On This Day' article
• BBC news article about the degassing of Lake Nyos
• BBC Horizon episode Killer lakes
• Volcano World information
• USGS information
• Killer Lakes, Smithsonian magazine
• Gas threat grows from Cameroon's lethal lakes — article from The Guardian newspaper
• BBC News 27 Sep 2005: Action needed on deadly lakes
• The eruption at Lake Nyos from sdsu.edu
• NASA Exploding Lakes
• Mechanics of the switching on of the trigger mechanism of limnological catastrophes - Latvian research by Nataliya Anatolievna Solodovnik and Anatoliy Borisovich Solodovnik