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Bamboutu
The Bambouto massif or Bamboutos Mountains is a group of volcanoes based on a swell in the Cameroon Volcanic Line, located in the Western High Plateau of Cameroon, merging in the north with the Oku Volcanic Field. Geology The large volcanic complex extends in a NE-SW direction for over 50 km, with the highest peaks rising to 2,679 m around the rim of a caldera with diameter 10 km. Lava dating gives ages from 23 to 6 million years ago, with a lower basaltic series and an upper series of trachytes, trachyphonolites and phonolite Phonolite is an uncommon shallow intrusive or extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a var ...s. Environment The upper part of the massif above 2,000 m has a cool and cloudy climate with 2,510 mm of rainfall annually. Soils are acidic, low in phosphates and relatively inferti ... [...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] |
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] |
Western High Plateau
The Western High Plateau, Western Highlands or Bamenda Grassfields is a region of Cameroon characterised by high relief, cool temperatures, heavy rainfall and savanna vegetation. The region lies along the Cameroon line and consists of mountain ranges and volcanoes made of crystalline and igneous rock. The region borders the South Cameroon Plateau to the southeast, the Adamawa Plateau to the northeast and the Cameroon coastal plain to the south. Topography and geology The Western High Plateau lies along the Cameroon line, a series of volcanic swells running from the Atlantic Ocean in the southwestern part of the plateau to the Adamawa Plateau in the northeast. The region is characterised by accidented relief of massifs and mountains. The Western High Plateau features several dormant volcanoes, including the Bamboutos Mountains, Mount Oku and Mount Kupe. The plateau rises in steps from the west. To the east, it terminates in mountains that range from 1,000 metres to 2,50 ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Cameroon
Cameroon, officially the Republic of Cameroon, is a country in Central Africa. It shares boundaries with Nigeria to the west and north, Chad to the northeast, the Central African Republic to the east, and Equatorial Guinea, Gabon, and the Republic of the Congo to the south. Its coastline lies on the Bight of Biafra, part of the Gulf of Guinea, and the Atlantic Ocean. Due to its strategic position at the crossroads between West Africa and Central Africa, it has been categorized as being in both camps. Cameroon's population of nearly 31 million people speak 250 native languages, in addition to the national tongues of English and French, or both. Early inhabitants of the territory included the Sao civilisation around Lake Chad and the Baka people (Cameroon and Gabon), Baka hunter-gatherers in the southeastern rainforest. Portuguese discoveries, Portuguese explorers reached the coast in the 15th century and named the area ''Rio dos Camarões'' (''Shrimp River''), which became ''C ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
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] |
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] |
Trachyte
Trachyte () is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanite, 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 differe ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
Phonolite
Phonolite is an uncommon shallow intrusive or extrusive rock, of intermediate chemical composition between felsic and mafic, with texture ranging from aphanitic (fine-grained) to porphyritic (mixed fine- and coarse-grained). Phonolite is a variation of the igneous rock trachyte that contains nepheline or leucite rather than quartz. It has an unusually high (12% or more) Na2O + K2O content, defining its position in the TAS classification of igneous rocks. Its coarse grained (phaneritic) intrusive equivalent is nepheline syenite. Phonolite is typically fine grained and compact. The name ''phonolite'' comes from the Ancient Greek meaning "sounding stone" due to the metallic sound it produces if an unfractured plate is hit; hence, the English name ''clinkstone'' is given as a synonym. Formation Unusually, phonolite forms from magma with a relatively low silica content, generated by low degrees of partial melting (less than 10%) of highly aluminous rocks of the lower crust su ... [...More Info...] [...Related Items...] OR: [Wikipedia] [Google] [Baidu] |
