evidence: Cameroon has four major aquifers and a network of rivers. In the north, the Logone River flows into Lake Chad. The Benoue River also runs north, emptying into the Niger River in Nigeria. In the south, the Ntem, Nyong, Sanaga and Wouri rivers flow west into the Gulf of Guinea. Major wetlands include mangrove forests on the coasts and the Yaeres floodplains in the northern Waza Logone region. Lake Chad, at the tip of the extreme north of the country, is shared with Chad, Nigeria and Niger. Cameroon has tectonic lakes (Ossa, Dissoni and Ejagham) and several volcanic lakes that store carbon dioxide and other gases below their lake bottoms. Scientists believe that in 1986 heavy rains disturbed the bottom of Lake Nyos, causing an expulsion of carbon dioxide that killed 1,700 people in the villages surrounding the lake (SDSU 2006; FAO 2005; Moula and Lambi 2006).