The Cameroon line is a 1,600 km (990 mi) 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. 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.
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 Pagalu (or Annobón), São Tomé, Príncipe and Bioko. Two large seamounts lie between São Tomé and Príncipe, and between Principe and Bioko. On the mainland, the line starts with Mount Cameroon and extends northeast in a range known as the Western High Plateau, home to the Cameroonian Highlands forests. Volcanic swells further inland are Manengouba, Bamboutu and the Oku Massif. East of Oku there are further volcanic mountains in the Ngaoundere Plateau, some of which appear to have similar origins.
The southernmost island in the chain is Annobón, also known as Pagalu, with an area of about 17.5 km2 (6.8 sq mi). It is an extinct volcano that rises from deep water to 598 m (1,962 ft) above sea level. The average temperature is 26.1 °C (79.0 °F), with little seasonal variation. Most rain falls from November to May, with annual precipitation averaging 1,196 mm (47.1 in) - less than on the mainland. Annobón has lush valleys and steep mountains, covered with rich woods and luxuriant vegetation. The island belongs to Equatorial Guinea. The small population lives in one community, practicing some agriculture but mainly living by fishing.
São Tomé Island is 854 km2 (330 sq mi) in area, lying almost on the equator. The entire island is a massive shield volcano which rises from the floor of the Atlantic Ocean, over 3,000 m (10,000 ft) below sea level, and reaches 2,024 m (6,640 ft) above sea level in the Pico de São Tomé. The oldest rock on Sao Tome is 13 million years old. Most of the lava erupted on São Tomé over the last million years has been basalt. The youngest dated rock on the island is about 100,000 years old, but numerous more recent cinder cones are found on the southeast side of the island.
Due to the prevailing southwesterly winds, there is great variability in rainfall. In the rain shadow to the northeast of Sao Tome the vegetation is dry savannah, with only 60 cm (24 in) of rain each year. By contrast, the lush south and west of the island receive about 6 m (20 ft) of rain, mostly falling in March and April. The climate is hot and humid with the rainy season from October to May. The higher slopes of the island are forested and form part of the Obo National Park. São Tomé has never been connected to Africa, and therefore has many unique plants and birds. Of the bird species, 16 are endemic and six are near endemic, of which four are only shared with Príncipe. Six species are considered vulnerable, and three are critically endangered (São Tomé ibis, São Tomé fiscal and São Tomé grosbeak). Schistometopum thomense, a bright yellow species of caecilian, is endemic to São Tomé.
As of 2010, São Tomé and Príncipe, an independent nation, had an estimated population of 167,000, most of whom lived on São Tomé island. The main language is Portuguese, but there are many speakers of Forro and Angolar (Ngola), two Portuguese-based creole languages. The economy is mainly based on tourism. Agriculture is important near the north and east coasts, with the chief exports being cocoa, coffee, copra, and palm products. There are large reserves of oil in the ocean between Nigeria and São Tomé which have not yet been exploited.
Príncipe is the smaller of the two major islands of São Tomé and Príncipe, with an area of 136 km2 (53 sq mi). Volcanic activity stopped around 15.7 million years ago, and the island has been deeply eroded apart from spectacular towers of phonolite. The island is surrounded by smaller islands including Ilheu Bom Bom, Ilhéu Caroço, Tinhosa Grande and Tinhosa Pequena, and lies in ocean 3,000 m (9,800 ft) deep. It rises in the south to 946 m (3,104 ft) at Pico de Príncipe, in a thickly forested area within the Obo National Park. The north and centre of the island were formerly plantations but have largely reverted to forest. As with São Tomé, the island has always been isolated from the mainland and therefore has many unique species of plants and animals, including six endemic birds. Príncipe has a population of around 5,000 people. Other than Portuguese, some speak Principense or Lunguyê with a few Forro speakers.
Bioko is just 32 km (20 mi) off the coast of Cameroon, on the continental shelf. The island used to be the end of a peninsula attached to the mainland, but was cut off when sea levels rose 10,000 years ago at the end of the last ice age. With an area of 2,017 km2 (779 sq mi) it is the largest island in the Cameroon line.
Bioko has three basaltic shield volcanoes, joining at the lower levels. San Carlos is 2,260 m (7,410 ft) high with a broad summit caldera, lying at the extreme SW of the island. The volcano dates from the Holocene age and has been active within the last 2000 years. Santa Isabel is the largest volcano at 3,007 m (9,865 ft) in height, and contains many satellite cinder cones. Three eruptions have been reported from vents on the southeast flank during the late-19th and early-20th centuries. San Joaquin, also known as Pico Biao or Pico do Moka, is 2,009 m (6,591 ft) high, on the southeast of the island. The summit is cut by a small lake-filled caldera, and there is a crater lake on the NE flank. San Joaquin has also been active during the last 2000 years.
The southwestern side of Bioko is rainy for most of the year, with annual rainfall in some locations of 10,000 mm (394 in). The climate is tropical at lower altitudes, becoming about 1 °C (1.8 °F) cooler for each 150 m (492 ft) of elevation. There is open canopy montane forest above 1,500 m (4,900 ft) on Pico Basilé, Gran Caldera de Luba and Pico Biao, with subalpine grassland above 2,500 m (8,200 ft). Bioko has exceptional numbers of endemic species of flora and fauna, partly due to the great range of altitudes, particularly birdlife. The montane forest is protected by the 330 km2 (130 sq mi) Basilé National Park and the 510 km2 (200 sq mi) Luba Crater Scientific Reserve. There has been little habitat loss, and the southern slopes have remained almost completely undisturbed. Although hunting pressure is rising, the fauna in the inaccessible southern part of the island is mostly intact. This includes an endemic subspecies of drill, Mandrillus leucophaeus poensis.
Bioko is part of the Republic of Equatorial Guinea. The island has a population of 334,463 inhabitants (2015 Census), most of whom are Bubi. The rest of the population are Fernandinos, Spaniards and immigrants from Río Muni, Nigeria and Cameroon. Cocoa production was once the main export, but has declined in recent years. Farming, fishing and logging remain important. Natural gas is produced in offshore wells, processed on the island and exported via tanker.
The Western High Plateau, also called the Western Highlands or the Bamenda Grassfields, continues the Cameroon line into the mainland of Cameroon. The plateau rises in steps from the west. To the east, it terminates in mountains that range in height from 1,000 m (3,300 ft) to 2,500 metres (8,200 ft). The plateau gives way to the Adamawa Plateau to the northeast, a larger but less rugged region.
The Western High Plateau features several dormant volcanoes, including the Bamboutos Mountains, Mount Oku, and Mount Kupe. Crater lakes dot the plateau, the result of dead volcanoes filling with water. This includes Lake Barombi Mbo and Lake Bermin, which have the highest number of endemic fish species per area recorded anywhere in the world.
The 4,095 m (13,435 ft) Mount Cameroon on the coastline, which may have been observed by the Carthaginian Hanno the Navigator in the 5th century BC, erupted in 2000. Further inland, the stratovolcano Mount Oku at 3,011 metres (9,879 ft) is the second highest mountain in sub-Saharan mainland West Africa. In 1986, Lake Nyos, a crater lake in the Oku volcanic plain, released a cloud of carbon dioxide gas that killed at least 1,200 people.
The region has cool temperatures, heavy rainfall, and savanna vegetation. The plateau experiences an equatorial climate with a wet season of nine months, and a dry season of three months. During the wet season, humid, prevailing monsoon winds blow in from the west and lose their moisture upon hitting the region's mountains. Average rainfall per year ranges from 1,000 mm (39 in) to 2,000 mm (79 in). High elevations give the region a cooler climate than the rest of Cameroon. For example, the average temperature at Dschang in the West Province is 20 °C (68 °F). Toward the north, rainfall levels are reduced as the Sudan climate becomes predominant.
The Western High Plateau's relief and high rainfall make it a major watershed for Cameroon. Important rivers in the region include the Manyu, which rises in the Bamboutos Mountains and becomes the Cross River on its lower course, and the Nkam, which is known as the Wouri River on its lower course. The region gives rise to important tributaries to the Sanaga River. These rivers have a long high-water period during the wet season and a short low-water period during the dry season.
Volcanism has created fertile black and brown soils. The Western High Plateau was once heavily forested. However, repeated cutting and burning by humans has forced the forest back to areas along the waterways and has allowed grasslands to expand into the area. Sudan savanna forms the dominant vegetation. This consists of grassfields—leading to the name Bamenda grassfields around the city of Bamenda—and short shrubs and trees that shed their foliage during the dry season as a defence against brush fires and dry weather. Raffia palms grow in the valleys and depressions.
Although geographers may limit the Cameroon line to the volcanoes in the island chain and the Western High Plateau, many geologists also include the Ngaoundere Plateau which extends the line to the east in the Adamawa plateau, and some would also include the Biu plateau and the Jos Plateau in Nigeria.
Geologists disagree over which volcanic regions should be included in the Cameroon Volcanic Line. All include the island line and the continental line up to Oku. Based on similarities in age and composition, some also include the Ngaoundere Plateau, the Biu plateau of Nigeria to the north of the Yola arm of the Benue Trough, and the Jos Plateau to the west of the Benue Trough. There are varying theories for the similarities between the oceanic and continental volcanoes.
The Cameroon line bisects the angle where the coast of Africa makes a 90° bend from the southern coast along the west of the Congo craton and the western coast along the south of the West African craton. The coastline roughly corresponds to the coast of the Borborema geological province of northeastern Brazil, which began to separate from this part Africa around 115 million years ago.
The Central African Shear Zone (CASZ), a lineament that extends from the Sudan to coastal Cameroon, runs under the continental section of the Cameroon line. It is visible in the Foumban Shear Zone, which was active before and during the opening of the South Atlantic in the Cretaceous period. The western end of the shear zone is obscured by the volcanoes of the Cameroon line, but based on reconstruction of the configuration of South America before it separated from Africa, the Foumban Shear Zone can be identified with the Pernambuco fault in Brazil. A major earthquake in 1986 could indicate that the shear zone is reactivating.
The Benue Trough lies to the west of the Cameroon line. The Benue Trough was formed by rifting of the central West African basement, beginning at the start of the Cretaceous era. A common explanation of the trough's formation is that it is an aulacogen, an abandoned arm of a three-armed radial rift system. The other two arms continued to spread during the break-up of Gondwana, as South America separated from Africa. During the Santonian age, around 84 million years ago, the Benue Trough underwent intense compression and folding. Since then it has been tectonically quiet.
The basaltic rocks in the oceanic and continental sectors of the Cameroon line are similar in composition, although the more evolved rocks are quite distinct. The similarity in basaltic rocks may indicate they have the same source. Since the lithosphere mantle below Africa must be different in chemical and isotopic composition from the younger lithosphere below the Atlantic, one explanation is that the source is in the asthenosphere rather than in metasomatized lithosphere. A different view is that the similarities are caused by shallow contamination of the oceanic section, which could be caused by sediments from the continent or by rafted crustal blocks that were trapped in the oceanic lithosphere during the separation between South America and Africa.
According to some geologists, there is evidence that a mantle plume has existed in the region for about 140 million years, first remaining in roughly the same position while the African plate rotated above it, and then remaining stationary under the Oku area since around 66 million years ago. The abnormal heat rising in a mantle plume would lead to melting of the upper mantle, which raises, thins and weakens the crust and facilitates rifting. This may have been repeated several times in the Benue Trough between 140 Ma and 49 Ma. One hypothesis for the later development of the Cameroon Line around 30 Ma is that it coincides with development of a shallow mantle convection system centered on the mantle plume, and is related to thinning and extension of the crust along the Cameroon line as pressures relaxed in the now stationary plate. The mantle plume hypothesis is disputed by others, who say the region is quite different from what is predicted by that hypothesis, and that a source in lithospheric fracture is more likely to be the explanation.
The line may be due to a more complex interaction between a hotspot and Precambrian faults. A gravity study of the southern part of the Adamawa plateau has shown a belt of dense rocks at an average depth of 8 km running parallel to the Foumban shear zone. The material appears to be an igneous intrusion that may have been facilitated by reactivation of the shear zone, and may be associated with the Cameroon line.
Annobón, also spelled Anabon and formerly as Anno Bom and Annabona, is a province of Equatorial Guinea consisting of the island of Annobón and its associated islets in the Gulf of Guinea and Atlantic Ocean's Cameroon line. The provincial capital is San Antonio de Palé on the north side of the island; the other town is Mabana, formerly known as San Pedro. The roadstead is relatively safe, and some passing vessels take advantage of it in order to obtain water and fresh provisions, of which Annobon has offered an abundant supply. However, there is no regular shipping service to the rest of Equatorial Guinea, and ships call as infrequently as every few months. According to the 2015 census it had 5,232 inhabitants, a small population increase from the 5,008 registered by the 2001 census. The official language is Spanish but most of the inhabitants speak a creole form of Portuguese. The island's main industries are fishing and timbering.Bakossi Mountains
The Bakossi Mountains are a mountain range that forms part of the Cameroon line of active and extinct volcanoes in western Cameroon, covering about 230,000 square kilometres (89,000 sq mi).
The mountains lie in the regions of Littoral and the Southwest.
The highest peak in this range is Mount Kupe at 2,064 metres (6,772 ft). They contain a large area of cloud forest, and have considerable ecological interest. The mountains are home to the Bakossi people.The climate is tropical, with rainfall throughout the year. The drier season lasts from November to March, with cold nights and hot days. The rainy season starts in April and peaks between late August and the end of October. The soil is fertile, supporting coffee and cocoa as cash crops.The mountains hold the Bakossi Forest Reserve, a 5,517 square kilometres (2,130 sq mi) reserve created in 1956.
In 2000, the main section of the reserve was designated a protection forest. All logging was banned and Kupe became a "strict nature reserve". The local Bakossi people participated in delineating the boundaries.
The Forest Reserve in turn contains the Bakossi National Park, created by a decree in early 2008.
The park covers 29,320 hectares (72,500 acres), and was justified on the basis of preserving plant diversification.Bioko
Bioko (also spelled Bioco, in Europe traditionally called Fernando Po [fɨɾˈnɐ̃du ˈpɔ] from the period of Portuguese colonization) is an island 32 km (20 mi) off the west coast of Africa, and the northernmost part of Equatorial Guinea. Its population was 334,463 at the 2015 census (preliminary results) and it covers an area of 2,017 km2 (779 sq mi). The island is located off Cameroon, in the Bight of Bonny portion of the Gulf of Guinea. Its geology is volcanic; its highest peak is Pico Basile at 3,012 m (9,882 ft).Biu Plateau
The Biu Plateau is a highland area in Northeastern Nigeria containing many recently extinct volcanoes. It covers about 5,200 km2 (2,000 sq mi) and has an average elevation of 700 m (2,300 ft). The plateau lies between the Upper Benue Basin to the south and the Chad Basin to the north. High points are Wade Hill at 775 m (2,543 ft) above sea level and Wiga Hill, at well over 800 m (2,600 ft). The plateau is the source of many tributaries of the Gongola River, which have cut deep gorges. To the north the plateau slopes gently to the Bauchi plains and the Chad Basin.There is evidence of early volcanic activity in the area during the Cretaceous, which ended about 66 million years ago. However, the plateau was built around the end of the Miocene, and the bulk of the rocks are Pliocene basalts that have erupted from small vents or fissures, and then spread in a thin layer over wide areas. Activity resumed in the Quaternary with thin flows of lava issuing from small cinder cones and filling the valleys. Most of the basalts date between 7 and 2 million years ago, but some are less than a million years old. The plateau includes many small pyroclastic cones caused by explosions when water penetrated downward and came into contact with fresh lava. There are a number of well-preserved volcanic cones rising above the Plateau along a NNW-SSE axis in the Miringa volcanic zone.Some geologists consider that the volcanic activity in the Biu Plateau is associated with the activity in the Cameroon line to the south.Geology of São Tomé and Príncipe
São Tomé and Príncipe both formed within the past 30 million years due to volcanic activity in deep water along the Cameroon line. Long-running interactions with seawater and different eruption periods have generated a wide variety of different igneous and volcanic rocks on the islands with complex mineral assemblages.Gulf of Guinea
The Gulf of Guinea is the northeasternmost part of the tropical Atlantic Ocean between Cape Lopez in Gabon, north and west to Cape Palmas in Liberia. The intersection of the Equator and Prime Meridian (zero degrees latitude and longitude) is in the gulf.
Among the many rivers that drain into the Gulf of Guinea are the Niger and the Volta. The coastline on the gulf includes the Bight of Benin and the Bight of Bonny.Lake Nyos
Lake Nyos is a crater lake in the Northwest Region of Cameroon, located about 315 km (196 mi) 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 (CO2) into the water, changing it into carbonic acid. Nyos is one of only three known exploding lakes to be saturated with carbon dioxide in this way, 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 CO2, which suffocated 1,746 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 siphons water from the bottom layers to the top, allowing the carbon dioxide to leak in safe quantities, was installed in 2001. Two additional tubes were installed in 2011.
Today, the lake also poses a threat because its natural wall is weakening. A geological tremor could cause this natural levée to give way, allowing water to rush into downstream villages all the way into Nigeria and allowing large amounts of carbon dioxide to escape.List of Ultras of Africa
This is a list of all the Ultra prominent peaks (with topographic prominence greater than 1,500 metres) in Africa. Also shown is Mount Catherine in Sinai, Egypt which is not geographically part of Africa. Not listed here are the 5 Ultras of the Canaries and Madeira which are off the African Coast but listed under Europe.Mount Kupe
Mount Kupe or Mont Koupé is a plutonic mountain in the Western High Plateau of Cameroon, part of the Cameroon line of volcanoes. It is the highest of the Bakossi mountains, rising to 2,064 metres (6,772 ft).The mountain is revered by the local Bakossi people as the home of their ancestral and forest spirits.
Missionaries in the 1890s observed that the mountain had a strong magical reputation, and it still has an important role in beliefs related to ekong, a form of witchcraft.
The mountain used to be forest-covered apart from a few small grassy areas near the summit. The causes of deforestation in the Bakossi landscape, are shifting cultivation, logging for timber, felling for fuelwood, growth and expansion of human settlements and establishment of pasture lands.
All sides of the mountain have been steadily converted to agricultural use.
Forest has been cleared up to 1,500m on the eastern slopes and up to between 750m and 1,100m on the western and northern sides, above the villages of Mbule and Nyasoso.As of 2010, there was still primary mid-altitude and montane rainforest on the northern side.
The cloud forest supports rich biodiversity, and is home to chimpanzees and several species of threatened primates.
The Mount Kupe bushshrike Telophorus kupeensis is known to be endangered due to its small range and declining quality of its habitat.
The Mount Kupe Forest Project was at first managed by BirdLife International, later by WWF-UK and then by WWF-Cameroon. As of 2010 the project was dormant.Mountain saw-wing
The mountain saw-wing (Psalidoprocne fuliginosa), also known as the mountain rough-winged swallow or the Cameroon Mountain rough-winged swallow is a species of bird in the family Hirundinidae.
It is found on Bioko island and adjacent Mt. Cameroon. While it has been reported elsewhere in Central Africa (namely, the Cameroon line of Cameroon and Nigeria), it has never been confirmed.Mungo River, Cameroon
The Mungo River is a large river in Cameroon that drains the mountains in the southern portion of the Cameroon line of active and extinct volcanoes.Pico Basilé
Pico Basilé (formerly Pico de Santa Isabel), located on the island of Bioko, is the tallest mountain of Equatorial Guinea. With an altitude of 9,878 ft (3,011 m), it is the summit of the largest and highest of three overlapping basaltic shield volcanoes which form the island. From the summit, Mt. Cameroon can be seen to the northeast. Pico Basilé lies close to the city of Malabo. The very top is used as a broadcast transmitting station for RTVGE (Radio Television Guinea Ecuatorial) and microwave relay station for various communication networks.
The peak forms a part of Pico Basilé National Park, created in April 2000 The boundaries of Bioko Norte and Sur runs near the summit.
Bioko was formed along the Cameroon line, a major northeast-trending geologic fault that runs from the Atlantic Ocean into Cameroon. This line includes other volcanic islands in the Gulf of Guinea such as Annobón, Príncipe and São Tomé, along with the massive stratovolcano of Mount Cameroon. Unlike the three other islands which are extinct volcanoes, its last eruption occurred in 1923.Pico do Príncipe
Pico do Príncipe is a mountain on the island of Príncipe, the smaller of the two inhabited islands of São Tomé and Príncipe. The elevation of the mountain is 947 metres (3,107 ft), making it the highest peak on the island. The island is one of the volcanic swells that make up the Cameroon line of extinct and active volcanoes.Príncipe
Príncipe is the smaller, northern major island of the country of São Tomé and Príncipe lying off the west coast of Africa in the Gulf of Guinea. It has an area of 142 square kilometres (55 sq mi) (including offshore islets) and a population of 7,324 at the 2012 Census; the latest official estimate (at May 2018) was 8,420. The island is a heavily eroded volcano speculated to be over three million years old, surrounded by smaller islands including Ilheu Bom Bom, Ilhéu Caroço, Tinhosa Grande and Tinhosa Pequena. Part of the Cameroon Line archipelago, Príncipe rises in the south to 947 metres at Pico do Príncipe. The island is the main constituent of the Autonomous Region of Príncipe, established in 1995, and of the coterminous district of Pagué.Quioveo
Quioveo is the extinct volcanic peak at the centre of the island of Annobón, Equatorial Guinea. It rises to a height of 598 metres. The island of Annobón is part of the Cameroon line of volcanoes, together with the islands of São Tomé Island, Príncipe, Bioko, and Mount Cameroon on the African mainland.São Tomé, Príncipe, and Annobón moist lowland forests
The São Tomé, Príncipe, and Annobón moist lowland forests is a tropical moist broadleaf forest ecoregion that covers the islands of São Tomé and Príncipe, which form the island nation of São Tomé and Príncipe, as well as the island of Annobón, which is part of Equatorial Guinea.West African slender-snouted crocodile
The West African slender-snouted crocodile (Mecistops cataphractus) is a critically endangered species of crocodile from Africa. It is one of five species of crocodile in Africa, the other four being the Central African slender-snouted, Nile, West African and dwarf crocodiles.
The slender-snouted crocodile (M. cataphractus) was thought to be distributed across west Africa and into central Africa but the central African species has been separated as the Central African slender-snouted crocodile (M. leptorhynchus) based on studies in 2014 and 2018 that indicated that both were distinct species. The name cataphractus is retained for the West African species as that species was described first based on specimens from western Africa. The two species diverged about 6.5-7.5 mya, living in different river drainage zones that were geographically separated from each other by the Cameroon Line.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.Wildlife of São Tomé and Príncipe
The wildlife of São Tomé and Príncipe is composed of its flora and fauna. São Tomé and Príncipe are oceanic islands which have always been separate from mainland West Africa and so there is a relatively low diversity of species, restricted to those that have managed to cross the sea to the islands. However the level of endemism is high with many species occurring nowhere else in the world.
Major African geological formations
|Cratons and shields|