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Oku Volcanic Field
The Oku Volcanic Field or Oku Massif is a 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. The massif has a diameter of almost 100 km and contains four major stratovolcanoes: Mount Oku, Mount Babanki 15 km SW of Oku, Nyos and Nkambe. Rocks in the massif have ages from 24.9 to 22.1 million years ago, but more recent activity has occurred. The massif is composed of rhyolitic and trachytic rock, and contains many maars and basaltic cinder cones. The Oku Volcanic Field includes two crater lakes, Lake Nyos to the north and Lake Monoun to the south. On 15 August 1984, an earthquake and landslide triggered a major release of carbon dioxide from Lake Monoun, killing several people. Lake Nyos is inside a maar formed by an explosion about 400 years ago, and is about 1,800 m wide and 208 m deep. There is a low-temp ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cameroon Line
The Cameroon line (, , ) is a long chain of volcanoes that includes islands in the Gulf of Guinea and mountains on the African mainland, from Mount Cameroon on the coast towards Lake Chad on the northeast. They form a natural border between eastern Nigeria and the West Region of Cameroon. The islands, which span the equator, have tropical climates and are home to many unique plant and bird species. The mainland mountain regions are much cooler than the surrounding lowlands, and also contain unique and ecologically important environments. The Cameroon volcanic line is geologically unusual in extending through both the ocean and the continental crust. Various hypotheses have been advanced by different geologists to explain the line. Geography In the Gulf of Guinea, the Cameroon line consists of six offshore volcanic swells that have formed islands or seamounts. From the southwest to the northeast the island groups are Annobón (or Pagalu), São Tomé, Príncipe and Bioko. T ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Basaltic
Basalt (; ) is an aphanitic (fine-grained) extrusive igneous rock formed from the rapid cooling of low-viscosity lava rich in magnesium and iron ( mafic lava) exposed at or very near the surface of a rocky planet or moon. More than 90% of all volcanic rock on Earth is basalt. Rapid-cooling, fine-grained basalt is chemically equivalent to slow-cooling, coarse-grained gabbro. The eruption of basalt lava is observed by geologists at about 20 volcanoes per year. Basalt is also an important rock type on other planetary bodies in the Solar System. For example, the bulk of the plains of Venus, which cover ~80% of the surface, are basaltic; the lunar maria are plains of flood-basaltic lava flows; and basalt is a common rock on the surface of Mars. Molten basalt lava has a low viscosity due to its relatively low silica content (between 45% and 52%), resulting in rapidly moving lava flows that can spread over great areas before cooling and solidifying. Flood basalts are thick s ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
List Of Volcanic Fields
A list of volcanic fields follows below. {{Incomplete list, date=May 2025 Africa Algeria * Atakor volcanic field * In Teria volcanic field * Manzaz volcanic field * Nemours-Nedroma * Tafna Beni Saf * Tahalra volcanic field Cameroon * Oku Volcanic Field Cape Verde * Charles Darwin volcanic field Chad * Tarso Toh Ethiopia * Dilo-Dukana volcanic field Eritrea *Assab volcanic field Kenya * Dilo-Dukana volcanic field Libya * Gharyan volcanic field * Haruj Madagascar * Ambre-Bobaomby volcanic field * Ankaizina volcanic field * Itasy volcanic field Morocco * Azrou volcanic field * Berguent volcanic field * Chott Tigri volcanic field * Mrit-Ment volcanic field * Oujda volcanic field * Oulmés volcanic field * Rekkame volcanic field Niger * Tin Taralle volcanic field * Todra volcanic field Sudan * Bayuda volcanic field * Meidob volcanic field * Tagabo Hills Asia China *Hainan Volcanic Field * Honggeertu volcanic field * Keluo * Northern Tibet volcanic field * Wudalianchi volcan ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Foumban Shear Zone
The Foumban Shear Zone, or Central Cameroon Shear Zone (CCSZ), is a fault zone in Cameroon that has been correlated with the Pernambuco fault in northeastern Brazil, which splays from the Trans-Brazilian Lineament. It is part of the Central African Shear Zone (CASZ) and dates to at least 640 million years ago. The zone was rejuvenated several times, usually with a dextral movement, before and during the opening of the South Atlantic in the Cretaceous period. The Foumban shear zone is a series of faults associated with major mylonite zones, a segment of the CASZ. The CASZ can be traced from the Sudan to the Adamawa plateau, after which its path is obscured by volcanoes. Based on reconstruction of the configuration of South America before it separated from Africa, the zone can be identified with the Pernambuco fault. The shear zone underlies a chain of active volcanoes, called the Cameroon Volcanic Line. In August 1986 a magnitude 5 earthquake with epicenter near Lake Nyos L ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Carbon Dioxide
Carbon dioxide is a chemical compound with the chemical formula . It is made up of molecules that each have one carbon atom covalent bond, covalently double bonded to two oxygen atoms. It is found in a gas state at room temperature and at normally-encountered concentrations it is odorless. As the source of carbon in the carbon cycle, atmospheric is the primary carbon source for life on Earth. In the air, carbon dioxide is transparent to visible light but absorbs infrared, infrared radiation, acting as a greenhouse gas. Carbon dioxide is soluble in water and is found in groundwater, lakes, ice caps, and seawater. It is a trace gas Carbon dioxide in Earth's atmosphere, in Earth's atmosphere at 421 parts per million (ppm), or about 0.042% (as of May 2022) having risen from pre-industrial levels of 280 ppm or about 0.028%. Burning fossil fuels is the main cause of these increased concentrations, which are the primary cause of climate change.IPCC (2022Summary for pol ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Monoun
Lake Monoun is a crater lake (maar) in West Province, Cameroon, that lies in the Oku Volcanic Field. On August 15, 1984, a limnic eruption occurred at the lake, which resulted in the release of a large amount of carbon dioxide () that killed 37 people. At first, the deaths remained unexplained, and causes such as terrorism were suspected. Further investigation and a similar event two years later at Lake Nyos led to the currently accepted explanation. Disaster Several people reported hearing a loud noise on August 15, 1984, around 22:30. A gas cloud reportedly emanated from a crater in the eastern part of the lake. The resulting deaths of 37 residents in a low-lying area are believed to have occurred between 03:00 and dawn. The victims were said to have skin burns, which reports later clarified as "skin damage" such as discoloration. Survivors reported that the whitish, smoke-like cloud smelled bitter and acidic. Vegetation was flattened around the eastern part of the l ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Lake Nyos
Lake Nyos ( ) is a crater lake in the Northwest Region of Cameroon, located about northwest of Yaoundé, the capital. Nyos is a deep lake high on the flank of an inactive volcano in the Oku volcanic plain along the Cameroon line of volcanic activity. A volcanic dam impounds the lake waters. A pocket of magma lies beneath the lake and leaks carbon dioxide () into the water, changing it into carbonic acid. Nyos is one of only three lakes known to be saturated with carbon dioxide in this way, and therefore prone to limnic eruptions (the others being Lake Monoun, also in Cameroon, and Lake Kivu in the Democratic Republic of Congo and Rwanda). In 1986, possibly as the result of a landslide, Lake Nyos suddenly emitted a large cloud of , which suffocated 1,746 people and 3,500 livestock in nearby towns and villages, the most notable one being Chah, which was abandoned after the incident. The limnic eruption not only devastated human and livestock populations but also ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cinder Cones
A cinder cone or scoria cone is a steep, conical landform of loose pyroclastic fragments, such as volcanic ash, clinkers, or scoria that has been built around a volcanic vent. The pyroclastic fragments are formed by explosive eruptions or lava fountains from a single, typically cylindrical, vent. As the gas-charged lava is blown violently into the air, it breaks into small fragments that solidify and fall as either cinders, clinkers, or scoria around the vent to form a cone that is often symmetrical, with slopes between 30° and 40° and a nearly circular base. Most cinder cones have a bowl-shaped crater at the summit. Mechanics of eruption Cinder cones range in size from tens to hundreds of meters tall. They are composed of loose pyroclastic material (cinder or scoria), which distinguishes them from '' spatter cones'', which are composed of agglomerated volcanic bombs. The pyroclastic material making up a cinder cone is usually basaltic to andesitic in composition. It is ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Maar
A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow crater lake, which may also be called a maar.David S.G. Thomas and Andrew Goudie (eds.), ''The Dictionary of Physical Geography'' (Oxford: Blackwell, 2000), 301. . Maars range in size from across and from deep. Most maars fill with water to form natural lakes. Most maars have low rims composed of a mixture of loose fragments of volcanic rocks and rocks torn from the walls of the diatreme. Etymology The name ''maar'' comes from a Moselle Franconian dialect word used for the circular lakes of the Daun area of Germany. The word evolved from its first use in German in the modern geological sense in 1819 and is now used in English and in the geological sciences as the term for the explosion crater, even if water from rainfall might alway ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cameroon Volcanic Line
The Cameroon line (, , ) is a long chain of volcanoes that includes islands in the Gulf of Guinea and mountains on the African mainland, from Mount Cameroon on the coast towards Lake Chad on the northeast. They form a natural border between eastern Nigeria and the West Region of Cameroon. The islands, which span the equator, have tropical climates and are home to many unique plant and bird species. The mainland mountain regions are much cooler than the surrounding lowlands, and also contain unique and ecologically important environments. The Cameroon volcanic line is geologically unusual in extending through both the ocean and the continental crust. Various hypotheses have been advanced by different geologists to explain the line. Geography In the Gulf of Guinea, the Cameroon line consists of six offshore volcanic swells that have formed islands or seamounts. From the southwest to the northeast the island groups are Annobón (or Pagalu), São Tomé, Príncipe and Bioko. Tw ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Trachytic
Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava (or shallow intrusions) enriched with silica and alkali metals. It is the volcanic equivalent of syenite. Trachyte is common wherever alkali magma is erupted, including in late stages of ocean island volcanismMacDonald 1983, pp. 51–52 and in continental rift valleys, above mantle plumes,Philpotts and Ague 2009, pp. 390–394 and in areas of back-arc extension. Trachyte has also been found in Gale crater on Mars. Trachyte has been used as decorative building stone and was extensively used as dimension stone in the Roman Empire and the Republic of Venice. Chemical composition Trachyte has a silica content of 60 to 65% and an alkali oxide content of over 7%. This gives it less SiO2 than rhyolite and more (Na2O plus K2O) than dacite. These chemical differences are c ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Rhyolitic
Rhyolite ( ) is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals ( phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase. It is the extrusive equivalent of granite. Its high silica content makes rhyolitic magma extremely viscous. This favors explosive eruptions over effusive eruptions, so this type of magma is more often erupted as pyroclastic rock than as lava flows. Rhyolitic ash-flow tuffs are among the most voluminous of continental igneous rock formations. Rhyolitic tuff has been used extensively for construction. Obsidian, which is rhyolitic volcanic glass, has been used for tools from prehistoric times to the present day because it can be shaped to an extremely sharp edge. Rhyolitic pumice finds use as an abrasive, in concrete, and as a soil amendment. Description Rhyo ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
