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Lake Nyos

Lake Nyos

Overview
Lake Nyos is a crater lake
Crater lake
A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not...

 in the Northwest Region of Cameroon
Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...

, located about 200 miles (321.9 km) northwest of Yaoundé
Yaoundé
-Transportation:Yaoundé Nsimalen International Airport is a major civilian hub, while nearby Yaoundé Airport is used by the military. Railway lines run west to the port city of Douala and north to N'Gaoundéré. Many bus companies operate from the city; particularly in the Nsam and Mvan neighborhoods...

. Nyos is a deep lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 high on the flank of an inactive volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 in the Oku volcanic plain along the Cameroon line
Cameroon line
The Cameroon line is a chain of volcanoes.It includes islands in the Gulf of Guinea and mountains that extend along the border region of eastern Nigeria and western Cameroon, from Mount Cameroon on the Gulf of Guinea north and east towards Lake Chad....

 of volcanic activity. A natural dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 of volcanic rock
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...

 contains the lake waters.

A pocket of magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

 lies beneath the lake and leaks carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 (CO2) into the water, changing it into carbonic acid
Carbonic acid
Carbonic acid is the inorganic compound with the formula H2CO3 . It is also a name sometimes given to solutions of carbon dioxide in water, because such solutions contain small amounts of H2CO3. Carbonic acid forms two kinds of salts, the carbonates and the bicarbonates...

.
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Encyclopedia
Lake Nyos is a crater lake
Crater lake
A crater lake is a lake that forms in a volcanic crater or caldera, such as a maar; less commonly and with lower association to the term a lake may form in an impact crater caused by a meteorite. Sometimes lakes which form inside calderas are called caldera lakes, but often this distinction is not...

 in the Northwest Region of Cameroon
Cameroon
Cameroon, officially the Republic of Cameroon , is a country in west Central Africa. It is bordered by Nigeria to the west; Chad to the northeast; the Central African Republic to the east; and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Cameroon's coastline lies on the...

, located about 200 miles (321.9 km) northwest of Yaoundé
Yaoundé
-Transportation:Yaoundé Nsimalen International Airport is a major civilian hub, while nearby Yaoundé Airport is used by the military. Railway lines run west to the port city of Douala and north to N'Gaoundéré. Many bus companies operate from the city; particularly in the Nsam and Mvan neighborhoods...

. Nyos is a deep lake
Lake
A lake is a body of relatively still fresh or salt water of considerable size, localized in a basin, that is surrounded by land. Lakes are inland and not part of the ocean and therefore are distinct from lagoons, and are larger and deeper than ponds. Lakes can be contrasted with rivers or streams,...

 high on the flank of an inactive volcano
Volcano
2. Bedrock3. Conduit 4. Base5. Sill6. Dike7. Layers of ash emitted by the volcano8. Flank| 9. Layers of lava emitted by the volcano10. Throat11. Parasitic cone12. Lava flow13. Vent14. Crater15...

 in the Oku volcanic plain along the Cameroon line
Cameroon line
The Cameroon line is a chain of volcanoes.It includes islands in the Gulf of Guinea and mountains that extend along the border region of eastern Nigeria and western Cameroon, from Mount Cameroon on the Gulf of Guinea north and east towards Lake Chad....

 of volcanic activity. A natural dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 of volcanic rock
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...

 contains the lake waters.

A pocket of magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

 lies beneath the lake and leaks carbon dioxide
Carbon dioxide
Carbon dioxide is a naturally occurring chemical compound composed of two oxygen atoms covalently bonded to a single carbon atom...

 (CO2) into the water, changing it into carbonic acid
Carbonic acid
Carbonic acid is the inorganic compound with the formula H2CO3 . It is also a name sometimes given to solutions of carbon dioxide in water, because such solutions contain small amounts of H2CO3. Carbonic acid forms two kinds of salts, the carbonates and the bicarbonates...

. Nyos is one of only three known exploding lakes
Limnic eruption
A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which carbon dioxide 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...

 to be saturated with carbon dioxide in this way, the others being Lake Monoun
Lake Monoun
Lake Monoun is a lake in West Province, Cameroon, that lies in the Oku Volcanic Field . On August 15, 1984, the lake exploded in a limnic eruption, which resulted in the release of a large amount of carbon dioxide that killed 37 people. At first, the cause of the deaths was a mystery, and...

, 100 km (62.1 mi) away SSE, and Lake Kivu
Lake Kivu
Lake Kivu is one of the African Great Lakes. It lies on the border between the Democratic Republic of the Congo and Rwanda, and is in the Albertine Rift, a part of the Great Rift Valley. Lake Kivu empties into the Ruzizi River, which flows southwards into Lake Tanganyika...

 in Democratic Republic of Congo. On August 21, 1986, possibly triggered by a landslide, Lake Nyos suddenly emitted a large cloud of CO2, which suffocated
Asphyxia
Asphyxia or asphyxiation is a condition of severely deficient supply of oxygen to the body that arises from being unable to breathe normally. An example of asphyxia is choking. Asphyxia causes generalized hypoxia, which primarily affects the tissues and organs...

 1,700 people and 3,500 livestock in nearby towns and villages. Though not completely unprecedented, it was the first known large-scale asphyxiation caused by a natural event. To prevent a recurrence, a degassing tube that syphons water from the bottom layers of water to the top allowing the carbon dioxide to leak in safe quantities was installed in 2001, though additional tubes are needed to make the lake safe.

Today, the lake also poses a threat due to its weakening natural wall. A geological tremor could cause this natural dike to give way, allowing water to rush into downstream villages all the way into Nigeria
Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...

 and allowing much carbon dioxide to escape.

Setting


Lake Nyos lies within the Oku Volcanic Field
Oku Volcanic Field
The Oku Volcanic Field or Oku Massif is group of volcanoes based on a swell in the Cameroon Volcanic Line, located in the Oku region of the Western High Plateau of Cameroon.The Mount Oku stratovolcano rises to 3,011 m above sea level....

, located near the northern boundary of the Cameroon Volcanic Line, a zone of volcanoes and other tectonic activity that extends southwest to the Mt. Cameroon stratovolcano
Stratovolcano
A stratovolcano, also known as a composite volcano, is a tall, conical volcano built up by many layers of hardened lava, tephra, pumice, and volcanic ash. Unlike shield volcanoes, stratovolcanoes are characterized by a steep profile and periodic, explosive eruptions...

. The field consists of volcanic maars and basaltic scoria cones.

Formation and geological history


Lake Nyos is located south of the dirt road from Wum
Wum
Wum is a town and commune in Cameroon. It is the capital of Menchum division in the Northwest Province.-Geography:Wum is the third biggest town in the North West Region of Cameroon. It lies on a plateau at an elevation of about 1100 m near the edge of the western highlands of Cameroon. It is north...

, about 30 km (18.6 mi) to the west, to Nkambe in the east. Villages along the road in the vicinity of the lake include Cha
Chah (Cameroon)
Chah or Cha is a village in Northwest Province of Cameroon, abandoned after the death of its inhabitants in 2005. The cause has been attributed to an eruption of carbon dioxide from nearby Lake Nyos....

, Nyos, Munji
Munji
The Munji language, also Munjani language, is a Pamir language spoken in Badakhshan Province in Afghanistan. It is similar to the Yidgha language which is spoken in the Upper Lutkuh Valley of Chitral, west of Garam Chishma in Pakistan....

, Djingbe, and Subum. The lake is 50 km (31.1 mi) from the Nigerian border to the north, and lies on the northern slopes of the Massif du Mbam, drained by streams running north, then northwest, to the Katsina-Ala River in Nigeria which is part of the Benue River
Benue River
The Benue River is the major tributary of the Niger River. The river is approximately 1,400 km long and is almost entirely navigable during the summer months...

 basin.

Lake Nyos fills a roughly circular maar
Maar
A maar is a broad, low-relief volcanic crater that is caused by a phreatomagmatic eruption, an explosion caused by groundwater coming into contact with hot lava or magma. A maar characteristically fills with water to form a relatively shallow crater lake. The name comes from the local Moselle...

 in the Oku Volcanic Field
Oku Volcanic Field
The Oku Volcanic Field or Oku Massif is group of volcanoes based on a swell in the Cameroon Volcanic Line, located in the Oku region of the Western High Plateau of Cameroon.The Mount Oku stratovolcano rises to 3,011 m above sea level....

, an explosion crater caused when a lava flow interacted violently with groundwater
Groundwater
Groundwater is water located beneath the ground surface in soil pore spaces and in the fractures of rock formations. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock...

. The maar is believed to have formed in an eruption about 400 years ago, and is 1,800 m (5,900 ft) across and 208 m (682 ft) deep. The area has been volcanically active for millions of years—after South America
South America
South America is a continent situated in the Western Hemisphere, mostly in the Southern Hemisphere, with a relatively small portion in the Northern Hemisphere. The continent is also considered a subcontinent of the Americas. It is bordered on the west by the Pacific Ocean and on the north and east...

 and Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

 were split apart by plate tectonics
Plate tectonics
Plate tectonics is a scientific theory that describes the large scale motions of Earth's lithosphere...

 about 110 million years ago, West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...

 also experienced rifting, although to a lesser degree. The rift is known as the Mbéré Rift Valley, and crust
Crust (geology)
In geology, the crust is the outermost solid shell of a rocky planet or natural satellite, which is chemically distinct from the underlying mantle...

al extension has allowed magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

 to reach the surface along a line extending through Cameroon. Mount Cameroon
Mount Cameroon
Mount Cameroon is an active volcano in Cameroon near the Gulf of Guinea. Mount Cameroon is also known as Cameroon Mountain or Fako or by its native name Mongo ma Ndemi ....

 also lies on this fault line. Lake Nyos is surrounded by old lava flows and pyroclastic
Pyroclastic flow
A pyroclastic flow is a fast-moving current of superheated gas and rock , which reaches speeds moving away from a volcano of up to 700 km/h . The flows normally hug the ground and travel downhill, or spread laterally under gravity...

 deposits.

Although Nyos is situated within an extinct volcano, magma still exists beneath it. Approximately 50 miles (80.5 km) directly below the lake resides a pool of magma
Magma
Magma is a mixture of molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets. Besides molten rock, magma may also contain suspended crystals and dissolved gas and sometimes also gas bubbles. Magma often collects in...

, which lets off carbon dioxide and other gases; the gasses then travel upward through the earth. The fumes are then ensnared by the natural springs encircling the lake, ultimately rising to the surface of the water and leading into the lake.

The lake waters are held in place by a natural dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 composed of volcanic rock
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...

. At its narrowest point, the wall measures 40 metres (131.2 ft) high and 45 metres (147.6 ft) wide.

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
Lake Monoun
Lake Monoun is a lake in West Province, Cameroon, that lies in the Oku Volcanic Field . On August 15, 1984, the lake exploded in a limnic eruption, which resulted in the release of a large amount of carbon dioxide that killed 37 people. At first, the cause of the deaths was a mystery, and...

, also in Cameroon, and Lake Kivu
Lake Kivu
Lake Kivu is one of the African Great Lakes. It lies on the border between the Democratic Republic of the Congo and Rwanda, and is in the Albertine Rift, a part of the Great Rift Valley. Lake Kivu empties into the Ruzizi River, which flows southwards into Lake Tanganyika...

 in Democratic Republic of Congo. A magma chamber
Magma chamber
A magma chamber is a large underground pool of molten rock found beneath the surface of the Earth. The molten rock in such a chamber is under great pressure, and given enough time, that pressure can gradually fracture the rock around it creating outlets for the magma...

 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 tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...

s of CO2.

Lake Nyos is thermally stratified
Stratification (water)
Water stratification occurs when water masses with different properties - salinity , oxygenation , density , temperature - form layers that act as barriers to water mixing...

, 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
Supersaturation
The term supersaturation refers to a solution that contains more of the dissolved material than could be dissolved by the solvent under normal circumstances...

, and if an event such as an earthquake
Earthquake
An earthquake is the result of a sudden release of energy in the Earth's crust that creates seismic waves. The seismicity, seismism or seismic activity of an area refers to the frequency, type and size of earthquakes experienced over a period of time...

 or landslide
Landslide
A landslide or landslip is a geological phenomenon which includes a wide range of ground movement, such as rockfalls, deep failure of slopes and shallow debris flows, which can occur in offshore, coastal and onshore environments...

 occurs, large amounts of CO2 may suddenly come out of solution.

The 1986 disaster



Although a sudden outgassing
Outgassing
Outgassing is the release of a gas that was dissolved, trapped, frozen or absorbed in some material. As an example, research has shown how the concentration of carbon dioxide in the Earth's atmosphere has sometimes been linked to ocean outgassing...

 of CO2 had occurred at Lake Monoun
Lake Monoun
Lake Monoun is a lake in West Province, Cameroon, that lies in the Oku Volcanic Field . On August 15, 1984, the lake exploded in a limnic eruption, which resulted in the release of a large amount of carbon dioxide that killed 37 people. At first, the cause of the deaths was a mystery, and...

 in 1984, killing 37 local residents, a similar threat from Lake Nyos was not anticipated. However, on August 21, 1986, a limnic eruption
Limnic eruption
A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which carbon dioxide 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...

 occurred at Lake Nyos which triggered the sudden release of about 1.6 million tonne
Tonne
The tonne, known as the metric ton in the US , often put pleonastically as "metric tonne" to avoid confusion with ton, is a metric system unit of mass equal to 1000 kilograms. The tonne is not an International System of Units unit, but is accepted for use with the SI...

s of CO2; this cloud rose at nearly 100 kilometres per hour (62.1 mph). The gas spilled over the northern lip of the lake into a valley running roughly east-west from Cha to Subum, and then rushed down two valleys branching off it to the north, displacing all the air and suffocating some 1,700 people within 25 kilometres (15.5 mi) of the lake, mostly rural villagers, as well as 3,500 livestock. The worst affected villages were Cha, Nyos, and Subum. Scientists concluded from evidence that a 300 feet (91.4 m) fountain of water and foam formed at the surface of the lake. The huge amount of water rising suddenly caused much turbulence in the water, spawning a wave of at least 80 feet (24.4 m) that would scour the shore of one side.

One survivor, Joseph Nkwain from Subum, described himself when he awoke after the gases had struck:

"I could not speak. I became unconscious. I could not open my mouth because then I smelled something terrible . . . I heard my daughter snoring in a terrible way, very abnormal . . . When crossing to my daughter's bed . . . I collapsed and fell. I was there till nine o'clock in the (Friday) morning . . . until a friend of mine came and knocked at my door . . . I was surprised to see that my trousers were red, had some stains like honey. I saw some . . . starchy mess on my body. My arms had some wounds . . . I didn't really know how I got these wounds . . .I opened the door . . . I wanted to speak, my breath would not come out . . . My daughter was already dead . . . I went into my daughter's bed, thinking that she was still sleeping. I slept till it was 4:30 p.m. in the afternoon . . . on Friday. (Then) I managed to go over to my neighbors' houses. They were all dead . . . I decided to leave . . . . (because) most of my family was in Wum . . . I got my motorcycle . . . A friend whose father had died left with me (for) Wum . . . As I rode . . . through Nyos I didn't see any sign of any living thing . . . (When I got to Wum), I was unable to walk, even to talk . . . my body was completely weak."


Carbon dioxide, being about 1.5 times as dense as air, caused the cloud to "hug" the ground and descend down the valleys where various villages were located. The mass was about 50 metres (164 ft) thick and it travelled downward at a rate of 20–50 km/h (12.4–31.1 ). For roughly 23 kilometres (14.3 mi) the cloud remained condensed and dangerous, suffocating many of the people sleeping in Nyos, Kam, Cha, and Subum. About 4,000 inhabitants fled the area, and many of these developed respiratory problems, lesion
Lesion
A lesion is any abnormality in the tissue of an organism , usually caused by disease or trauma. Lesion is derived from the Latin word laesio which means injury.- Types :...

s, and paralysis
Paralysis
Paralysis is loss of muscle function for one or more muscles. Paralysis can be accompanied by a loss of feeling in the affected area if there is sensory damage as well as motor. A study conducted by the Christopher & Dana Reeve Foundation, suggests that about 1 in 50 people have been diagnosed...

 as a result of the gases.

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. Others still believe there was a small earthquake, but as witnesses did not report feeling any tremors on the morning of the disaster, this hypothesis is unlikely. 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
Effervescence (chemistry)
Effervescence is the escape of gas from an aqueous solution and the foaming or fizzing that results from a release of the gas. The word effervescence is derived from the Latin verb fervere preceded by the adverb ex, which means to boil...

 out of solution.

It is believed that about 1.2 cubic kilometre (0.287895310325144 cu mi) of gas was released. The normally blue waters of the lake turned a deep red after the outgassing, due to iron
Iron
Iron is a chemical element with the symbol Fe and atomic number 26. It is a metal in the first transition series. It is the most common element forming the planet Earth as a whole, forming much of Earth's outer and inner core. It is the fourth most common element in the Earth's crust...

-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 and trees near the lake were knocked down.

Medical problems


Following the eruption, many survivors were treated at the main hospital in Yaoundé, the country's capital. It was believed that many of the victims had been poisoned by a mixture of gases including hydrogen
Hydrogen
Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of , hydrogen is the lightest and most abundant chemical element, constituting roughly 75% of the Universe's chemical elemental mass. Stars in the main sequence are mainly...

 and sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...

 gases. Poisoning by these gases would lead to burning pains in the eyes and nose, coughing and signs of asphyxiation similar to being strangled, as like "being gassed by a kitchen stove".

Following the disaster, the lake was dubbed the "Deadliest lake" by Guinness World Records
Guinness World Records
Guinness World Records, known until 2000 as The Guinness Book of Records , is a reference book published annually, containing a collection of world records, both human achievements and the extremes of the natural world...

 in 2008.

Degassing


The scale of the disaster led to much study on how a recurrence 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 barrier 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.

Several researchers independently proposed the installation of degassing columns from rafts in the lake. The principle is simple: a pump lifts water from the bottom of the lake, heavily saturated with CO2, until the loss of pressure begins releasing the gas from the diphasic fluid and thus makes the process self-powered. In 1992 at Monoun, and in 1995 at Nyos, a French team demonstrated the feasibility of this approach. In 2001, the US Office of Foreign Disaster Assistance
Office of Foreign Disaster Assistance
The Office of U.S. Foreign Disaster Assistance is an organizational unit within the U.S. Agency for International Development that has delegated responsible for directing and coordinating U.S. Government relief assistance overseas. Within USAID, OFDA resides within Bureau of Democracy, Conflict,...

 funded a permanent installation at Nyos.

More pipes are expected to be needed to make the lake safe: the original French estimates called for a total of five, and the current OFDA project calls for an additional two pipes, each with ten times the capacity of the single current pipe.

Following the Lake Nyos tragedy
Tragedy (event)
A tragedy is an event in which one or more losses, usually of human life, occurs that is viewed as mournful. Such an event is said to be tragic....

, scientists investigated other African lakes to see if a similar phenomenon could happen elsewhere. Lake Kivu
Lake Kivu
Lake Kivu is one of the African Great Lakes. It lies on the border between the Democratic Republic of the Congo and Rwanda, and is in the Albertine Rift, a part of the Great Rift Valley. Lake Kivu empties into the Ruzizi River, which flows southwards into Lake Tanganyika...

 in Democratic Republic of Congo, 2,000 times larger than Lake Nyos, was also found to be supersaturated, and geologists found evidence for outgassing events around the lake about every thousand years. The eruption of nearby Mount Nyiragongo
Mount Nyiragongo
Mount Nyiragongo is a stratovolcano in the Virunga Mountains associated with the Great Rift Valley. It is located inside Virunga National Park, in the Democratic Republic of the Congo, about 20 km north of the town of Goma and Lake Kivu and just west of the border with Rwanda. The main crater...

 in 2002 sent lava
Lava
Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling. This molten rock is formed in the interior of some planets, including Earth, and some of their satellites. When first erupted from a volcanic vent, lava is a liquid at...

 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 maintained in solution by the water pressure.

Weakening dam


On August 18, 2005, Dr. Isaac Njilah, a geologist at the University of Yaoundé
University of Yaoundé
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....

, suggested that the natural dam
Dam
A dam is a barrier that impounds water or underground streams. Dams generally serve the primary purpose of retaining water, while other structures such as floodgates or levees are used to manage or prevent water flow into specific land regions. Hydropower and pumped-storage hydroelectricity are...

 of volcanic rock
Volcanic rock
Volcanic rock is a rock formed from magma erupted from a volcano. In other words, it is an igneous rock of volcanic origin...

 that keeps in the lake's waters could collapse in the near future. Erosion
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...

 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 (1.8 billion cu ft) of water flooding downhill into areas of the Northwest Province and the Nigeria
Nigeria
Nigeria , officially the Federal Republic of Nigeria, is a federal constitutional republic comprising 36 states and its Federal Capital Territory, Abuja. The country is located in West Africa and shares land borders with the Republic of Benin in the west, Chad and Cameroon in the east, and Niger in...

n states of Taraba
Taraba
Taraba can refer to:* Taraba State* Taraba River* Taraba, the genus of the Great Antshrike...

 and Benue. Dr. Njilah estimates that the area is home to more than 10,000 people.

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
United Nations
The United Nations is an international organization whose stated aims are facilitating cooperation in international law, international security, economic development, social progress, human rights, and achievement of world peace...

 team led by Olaf Van Duin and Nisa Nurmohamed of the Netherlands
Netherlands
The Netherlands is a constituent country of the Kingdom of the Netherlands, located mainly in North-West Europe and with several islands in the Caribbean. Mainland Netherlands borders the North Sea to the north and west, Belgium to the south, and Germany to the east, and shares maritime borders...

 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 believed that the dam would breach within the next 10 or 20 years.

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 (65.6 ft), the pressure on the wall would be reduced significantly.

Return of population


Despite the risks from carbon dioxide and collapse of the lake's retaining wall, the area is being resettled. There is impatience with the apparent slowness of international organisations – Cameroon, UNDP, European Union
European Union
The European Union is an economic and political union of 27 independent member states which are located primarily in Europe. The EU traces its origins from the European Coal and Steel Community and the European Economic Community , formed by six countries in 1958...

 – to implement improvements in infrastructure and safety projects at the lake. Settlers cite the wish to return to ancestral lands (although some are newcomers) and the great fertility of the land as reasons for their return.

See also

  • Carbon sequestration
  • Limnic eruption
    Limnic eruption
    A limnic eruption, also referred to as a lake overturn, is a rare type of natural disaster in which carbon dioxide 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...

  • Limnology
    Limnology
    Limnology , also called freshwater science, is the study of inland waters. It is often regarded as a division of ecology or environmental science. It covers the biological, chemical, physical, geological, and other attributes of all inland waters...

  • Mazuku
    Mazuku
    In geology, a mazuku is a pocket of oxygen-poor air that can be lethal to any human or animal life inside. Mazuku are created when an odorless and invisible gas such as carbon dioxide accumulates in pockets low to the ground...

  • Meromictic lake
  • Lake Monoun
    Lake Monoun
    Lake Monoun is a lake in West Province, Cameroon, that lies in the Oku Volcanic Field . On August 15, 1984, the lake exploded in a limnic eruption, which resulted in the release of a large amount of carbon dioxide that killed 37 people. At first, the cause of the deaths was a mystery, and...

  • Lake Kivu
    Lake Kivu
    Lake Kivu is one of the African Great Lakes. It lies on the border between the Democratic Republic of the Congo and Rwanda, and is in the Albertine Rift, a part of the Great Rift Valley. Lake Kivu empties into the Ruzizi River, which flows southwards into Lake Tanganyika...


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