The Earth Story

Menchun Falls, Cameroon

Lake Nyos.

In the Northwest Region of Cameroon is a crater lake called Lake Nyos. It may look like an ordinary lake but in August 1986 this lake released a massive cloud of carbon dioxide killing over 1700 people and about 3500 livestock in the surrounding areas.

A pouch of magma exists below the lake. This magma converts the water into carbonic acid by depositing certain amounts of carbon dioxide into the water.

The 1986 disaster was a result of a limnic eruption (commonly referred to as lake overturn). This is an extremely rare type of natural disaster. Small amounts of carbon dioxide gather together to form a large pocket until it suddenly erupts, releasing this CO2 into the surrounding areas. These eruptions have been known to cause small tsunamis as the carbon dioxide that rises displaces the water. It is believed, by many scientists around the world, that landslides, volcanic activity or any kind of explosions can trigger a limnic eruption.

To prevent another disaster, in 2001 a tube was installed to draw water from the bottom of the lake to the top. This method allows the carbon dioxide to escape in small, safe amounts. In 2011, another two tubes were added to assist in the degassing of the lake.

♞Renesh T

Image Credit:

http://s281.photobucket.com/user/Lampedusa/media/Cameroon_Lake_Nyos_2009/IMG_6442.jpg.html

Further reading and references:

http://vulcan.wr.usgs.gov/Glossary/Lakes/description_volcanic_lakes_gas_release.html

http://news.bbc.co.uk/onthisday/hi/dates/stories/august/21/newsid_3380000/3380803.stm

http://www.iomcworld.com/ijcrimph/files/v01-n01-01.pdf

http://www.nytimes.com/2001/02/27/science/trying-to-tame-the-roar-of-deadly-lakes.html

Volcanoes in their senior years

When volcanoes lose their youthful fire, they may leave landscapes of hot springs, bubbling mud and skeletons of their internal workings.

The most dramatic landforms created by volcanoes are giant calderas—great circular scars, often many miles across, which were left behind when huge volcanoes from the past blew apart. Lake Taupo in New Zealand is a typical caldera. Two thousand years ago a large volcano lay dormant while magma built up beneath it. Then in AD 186 it erupted so violently that the whole centre of the mountain collapsed into the magma chamber. Where a majestic mountain once stood, with its summit in the clouds, there is now a wide lake fringed by a circle of low cliffs that mark the boundary of the huge caldera collapse. Sometime around 1645 BC, the central part of the Greek island of Santorini collapsed during a massive eruption which destroyed the ancient city of Akrotiri. Santorini may be the site of the mythical island of Atlantis described by Plato as having been engulfed by waves. The circle of islands that make up modern Santorini are the rim of the caldera left behind after explosion.

As active volcanoes fade into dormancy, they may leave a landscape of gas-emitting vents, hot springs and mud pools, often inside a caldera. Hot springs are formed when ground water percolates down towards a body of magma, then heats up and rises to the surface again. If the water gets hot enough it will boil, and steam will eject it towards the surface with great force to form a geyser. Old Faithful in Yellowstone Park gushes forth regularly every 1 and a quarter-hours or so—the time it takes for steam pressure to build up in underground reservoirs.

The molten rock in the roots of a volcano may take millions of years to cool and solidify, because the overlying rock acts like an insulating tea cosy. A dormant volcano will eventually become extinct, although no volcano above an active plate margin can ever be said to be truly extinct. The wind and weather then erode away the ash and the softer rocks through which the volcano erupted, to expose the internal feeder pipes which are now choked and solid with old magma. Because rock that is formed from cooled magma is usually very hard, the pipes and plugs of volcanoes resist weathering and are left as protrusions in the landscape.

Devils Tower in Wyoming, USA, which was made famous in the film “Close Encounters of the Third Kind,” is a volcano plug. The original volcano profile has long been eroded away; leaving intact the solidified magma that was inside the pipe. This has revealed the internal structure of six-sided basalt columns that were formed when the magma shrank as it cooled. Basalt columns are more common in lava flows, like the Giant’s Causeway in Northern Island which I have covered in a previous post found here ……………. Rhumsiki Peak, a volcanic plug exposed by erosion in Cameroon, West Africa is another example (post image).

As magma is squeezed to the surface it makes use of any fractures or weakness in the rock. Often it does not reach the surface and erupt as lava, but solidifies underground. In vertical cracks, molten rock congeals to make dykes—long straight walls of rock that may resist erosion. A dyke 9 miles (15km) long stretches out from Ship Rock in New Mexico desert. If the molten rock worms its way between horizontal cracks it hardens to make a sill. The Whin Sill in northern England was left as a long escarpment after the soft rock above was eroded away. It was used by the Romans as a barrier between Scotland and England, and they built part of Hadrian’s Wall along the top of it.

Molten rock injected into layers of sedimentary rock may bend the sedimentary rock upwards, forming a mushroom shape called a laccolith. Sometimes, laccoliths are stacked one on top of the other as the molten rock bursts up in successive layers and forms a ‘Christmas tree’ laccolith. The Judith Mountains in The US state of Montana take their shape from laccoliths.

Let us lastly look at the magma chamber itself. Beneath every volcano, there is — or was—a magma chamber. Often, the magma cooled underground, usually forming crystalline rock such as granite. Later Earth movements and erosion may strip off the rock which covered these batholiths, and exposed the granite on the surface. In Cornwall, round offshoots of a magma chamber called stocks protrude above the surface to make granite moorland such as Bodmin Moor. The Sierra Nevada in California is composed of a huge batholith which has been exposed to form a range of mountains. The granite walls of Yosemite Valley are cut in just a tiny fragment of them.

No matter where you step, the land under your feet is the result of some form of tectonic and volcanic activity. Millions of years of plate movement and erosion has shaped the land that you now stand on. The long history of these wonderful landscapes is nothing short of amazing and wonderful and it is fair to say that, as the saying goes, one should “respect your elders.” Respect the Earth the same way.

~ JM

The last post in this series: http://on.fb.me/1R2kdQl

Image Credit: Rhumsiki Peak, a volcanic plug exposed by erosion in Cameroon, West Africa: http://bit.ly/1DJ8Fqx

More Info: Calderas: http://bit.ly/1I07lpE Laccoliths: http://on.doi.gov/1EKpvL9 Batholith: http://bit.ly/1fFtXOz Dykes: http://bit.ly/1bM6zQB Magma Chamber: http://bit.ly/1dBPASj

Lake Kivu: Making the Most of a Deadly Situation

There are a lot of ways a volcano can kill you. Explosions, pyroclastic flows, ash that disrupts climate and growing patterns….and if you needed to add another to the list: exploding lakes. It sounds pretty dire, but some brilliant people with a knack for finding silver linings have come up with a way to turn one of these killers—exploding lakes—into an energy source.

Lakes that sit near volcanoes can become saturated with carbon dioxide. The carbon dioxide collects at the bottom of the lake, and with the right trigger, is suddenly released in a dense cloud, asphyxiating most life in its path. Two of the most infamous of these eruptions both occurred in Cameroon just two years apart—Lake Monoun in 1984 and Lake Nyos in 1986(http://on.fb.me/17hOLeB).

These “limnic eruptions” were very mysterious at first—they were killers that hardly left a trace. Once scientists figured out what was going on, they realized exploding lakes could be quelled by releasing the carbon dioxide slowly (via pipes) instead of letting it build up.

Enter some scientists who realized they could make the most of an unfortunate situation. There is another African lake that is very saturated with gas and shows signs of prehistoric eruptions—Lake Kivu on the border of the Democratic Republic of Congo and Rwanda. Lake Kivu is much larger than both Lake Monoun and Lake Nyos, and it is believed to hold much more gas—except most of this gas is not carbon dioxide, it is methane. Methane is an energy source. Methane can fuel power plants. Methane can provide electricity to the millions of people who live around the banks of Lake Kivu.

The Rwandan government decided to take advantage of this. Working with the energy firm, Contour Global, the aptly named project KivuWatt is under works to convert the methane to electricity. The plan is to suck gas out of the lake, as they would ordinarily do for safety reasons, and then harness the methane in a power plant off the coast.

Rwanda lacks many of its own natural resources and relies on foreign sources of fuel, so KivuWatt has the potential to change things. The first operations are supposed to start later this year.

-CM

For more information: http://bbc.in/1zMEH83 http://bit.ly/170FG9O http://bit.ly/1vFo5zo

Photo credit: The Advocacy Project http://bit.ly/1vNtkgx

Cameroon (Group A) - Mount Cameroon Rising through the mist is Mount Cameroon, one of the ‘Cameroon line’ of volcanoes, which includes both volcanic islands such as Principe, Sao Tome and Bioko (from which this photograph was taken) and bona-fide land-based volcanoes such as Mount Cameroon. This volcanic line is unusual because it features volcanoes both on continental crust (such as Mount Cameroon) and oceanic crust (such as the volcanic islands mentioned above). The cause for the volcanism, and the so-called ‘Cameroon line’ are disputed. Some invoke a mantle plume, similar to the Hawaiian island chain. A mantle plume would have stretched the old country rock (African Shield, thought to be around three billion years old) inducing volcanism, creating the islands and volcanoes seen. Cameroon burst onto the footballing stage in the 1990, with 38 year old Roger Milla scoring four goals as Cameroon stormed to the quarter finals, the furthest an African team has ever made it in a World Cup. Their defensive frailties were exposed however as, after going 2-1 up, they lost against England 3-2 after extra time, conceding two penalties. This year their hopes lie with another ‘old man’ Samuel Eto’o, leading the line. Will they be able to stretch a little more out of him and progress further than the heroes of 1990? Sedg Deadlier side of Cameroon’s volcanism: Lake Nyos -http://on.fb.me/1kRBPiH Image credit (non commercial): John and Mel Kotsopoulos (http://bit.ly/1idwvld) References: Burke 2001 (http://bit.ly/1lg94Mz) Wiki:http://en.wikipedia.org/wiki/Cameroon_line

LAKE NYOS, CAMEROON Lake Nyos in Cameroon has an unfortunate moniker attached; it is also known as “The Lake that Killed” or “Killer Lake”. The lake was responsible for the deaths of 1,700 people within 2 hours in 1986 after the lake outgassed so much carbon dioxide that it lowered the level of the lake by over a metre and turned the water to the colour of blood. The lake is a crater lake within a large caldera on the flanks of an inactive stratovolcano 3,011 metres elevation. The volcano is located in the north-west region of Cameroon and is part of the rhyolitic and trachytic Mount Oku massif along the Cameroon volcanic line. The lake is around 1,400 metres long, 900 metres wide, and 208 metres deep; it is situated above a pool of magma that slowly leaks carbon dioxide. The northeast rim of the lake has lava fountain and basaltic flow deposits, on the north and east flanks pyroclastic deposits can be found. The killer gas that emitted from the lake on August 21 1986 consisted of carbon dioxide mixed with sulphur and hydrogen; 1 cubic kilometre of the gas spread as far as 23 kilometres away from its source. It is thought the deadly emission occurred either due to overturn of stratified lake waters from a non-volcanic process, or to a phreatic explosion, or to injection of hot gas into the lake. The gas stayed close to the ground and swept over nearby villages and small towns. Around 1,700 people and 3,500 farm animals were killed; those that survived were left with long term side effects. To prevent further lethal emissions from the lake, a degassing tube was installed in 2001. The tube siphons water from the bottom layers of water to the top to allow the carbon dioxide to leak in safe amounts. -TEL More info: http://www.volcano.si.edu/world/volcano.cfm?vnum=0204-03- http://vulcan.wr.usgs.gov/Glossary/Lakes/description_volcanic_lakes_gas_release.html; http://www.neatorama.com/2007/05/21/the-strangest-disaster-of-the-20th-century/ Photo credit: USGS http://gallery.usgs.gov/images/02_06_2012/qvm8PCb54J_02_06_2012/large/2.jpg