Cameroon line
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.
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