volcanic activity with periodic releases of poisonous gases from Lake Nyos and Lake Monoun volcanoes
volcanism: Mt. Cameroon (4,095 m), which last erupted in 2000, is the most frequently active volcano in West Africa; lakes in Oku volcanic field have released fatal levels of gas on occasion, killing some 1,700 people in 1986
slightly larger than California; about four times the size of Pennsylvania