The Mandara Mountains are a volcanic range extending about 190 km (about 120 mi) along the northern part of the Cameroon–Nigeria border, from the Benue River in the south () to the north-west of Maroua in the north (). The highest elevation is the summit of Mount Oupay, at 1,494 m (4,900 ft) above sea level (). The region is densely populated, mainly by speakers of Chadic languages, including both the Mofu and the Kirdi ethnic groups. Extensive archaeological research has been undertaken in the Mandara Mountains, including work at Diy-Gid-Biy (DGB) sites. Geology The Mandara Mountains were formed millions of years ago when a continental plate of basement rock deep beneath the African continent rose up, fragmenting and splitting as it was pushed to the surface. The climate was significantly wetter in those times, so enormous amounts of precipitation formed numerous rivers that rushed through these fractures, carving them deeper and wider, resulting in the range's notably rugged terrain. Volcanic activity also played a role in the formation of the range. Eruptions of lava formed volcanic cones whose vents were eventually plugged with hardening magma. These hardened cores are called volcanic plugs. In the case of the Mandara Mountains, the plugs were much more erosion-resistant than the exterior of the cones, which wore away over time. Eventually, only the plugs remained, forming the stark, needle-like spires such as Kapsiki Peak that the range is known for. Gallery Climate The ecoregion has tropical savanna climate, moderated by elevation. Average annual rainfall varies from 800 to 1000 mm depending on location. Most rain falls during the long wet season from May to October, and the rest of the year is dry. Ecology The higher elevation and rainfall of the mountains sustained plant communities distinct from the surrounding lowlands. Open woodlands, dominated by the tree Isoberlinia doka, were once the dominant plant community in the ecoregion, In relatively intact woodlands the trees reach 12 to 18 meters high, and tree cover averages 50% or more. Grasses form the understory The highest-elevation areas, from 1,200 to 1,494 meters elevation, are home to a mix of lowland (Sudanian) and montane and submontane (Afromontane) species, including some rare and endemic plants and reptiles. The vegetation has been profoundly altered by heavy grazing, burning, and conversion to agriculture, and only fragmented and degraded areas of woodland remain. Mozogo-Gokoro National Park and Mayo-Louti Forest Reserve in Cameroon