Introduction
The Cameroon Volcanic Line (CVL) is a prominent geological feature in West-Central Africa, extending over 1,600 km from the Atlantic Ocean through Cameroon and into Nigeria. This unique chain of volcanic mountains and associated lakes provides a significant opportunity for geological study, particularly in understanding volcanic rock compositions, lake formations, and eruption types. The CVL is notable for its diverse volcanic activity, spanning both oceanic and continental settings, and includes some of the most active volcanoes in Africa, such as Mount Cameroon. Furthermore, the region hosts several crater lakes, some of which have gained international attention due to catastrophic events linked to their formation and chemistry. This essay explores the common rock types associated with the mountains of the CVL, the lakes found within this line, their formation mechanisms, and the predominant types of volcanic eruptions exhibited by the region’s volcanoes. By examining these elements, this paper aims to provide a broad understanding of the CVL’s geological significance while acknowledging the limitations of current research in fully elucidating some of its complexities.
Common Rock Types in the Mountains of the Cameroon Volcanic Line
The Cameroon Volcanic Line comprises several notable volcanic mountains, including Mount Cameroon, Mount Manengouba, Mount Bambouto, and Mount Oku, among others. A defining feature of these volcanoes is the dominance of basaltic rocks, which are characteristic of the CVL’s volcanic activity. Basalt, a mafic extrusive igneous rock, is commonly found across all major mountains in the CVL due to the region’s predominantly alkaline magmatism (Fitton and Dunlop, 1985). Typically, this basalt is fine-grained and dark in colour, formed from the rapid cooling of lava flows on the Earth’s surface.
Mount Cameroon, the most active volcano in the CVL, frequently produces basaltic lava flows during eruptions, as evidenced by historical events such as the 1999 eruption (Suh et al., 2001). Similarly, Mount Manengouba and Mount Bambouto, located within the continental segment of the CVL, also exhibit significant basaltic compositions, though some areas show evidence of more evolved rocks such as trachytes and rhyolites, indicative of magma differentiation over time (Marzoli et al., 2000). Mount Oku, part of the Bamenda Highlands, further reflects this pattern, with basalt dominating its lower slopes while phonolites and trachytes appear in more evolved volcanic structures. Despite these variations, basalt remains the most common rock type across the CVL, underscoring the region’s shared petrological heritage. However, detailed petrological analyses of lesser-studied volcanoes in the CVL are still sparse, limiting a comprehensive understanding of potential variations across the entire line.
Lakes in the Cameroon Volcanic Line and Their Formation
The CVL is also home to numerous crater lakes, formed primarily through volcanic activity. Among the most notable are Lake Nyos, Lake Monoun, and Lake Barombi Mbo, each offering insights into the region’s geological history. These lakes are typically situated within volcanic craters or calderas, formed following explosive eruptions or the collapse of volcanic structures. The formation process generally involves the creation of a depression during or after an eruption, which subsequently fills with water from rainfall or groundwater sources.
Lake Nyos, located in the Northwest Region of Cameroon, is perhaps the most infamous due to the 1986 disaster that released a deadly cloud of carbon dioxide, killing over 1,700 people (Kling et al., 1987). This lake occupies a maar, a type of volcanic crater formed by phreatomagmatic eruptions—explosive interactions between magma and groundwater. Similarly, Lake Monoun, another maar lake in the CVL, formed through a comparable explosive process and was the site of a similar gas release in 1984. Lake Barombi Mbo, on the other hand, is a larger crater lake near Mount Cameroon, likely formed through the subsidence of a volcanic caldera following significant eruptions. These examples illustrate how the lakes of the CVL are direct products of the region’s volcanic activity, with their specific morphologies tied to the nature of past eruptions. While the general mechanisms of crater lake formation are understood, the precise timing and detailed conditions of each lake’s origin remain under-researched, particularly for less-documented lakes in the region.
Types of Eruptions Exhibited by Volcanoes in the Cameroon Volcanic Line
The volcanic mountains of the CVL exhibit a range of eruption types, reflecting the diversity of magma compositions and tectonic settings along the line. Predominantly, the region is known for effusive eruptions, which produce extensive basaltic lava flows. Mount Cameroon, for instance, has experienced multiple effusive eruptions in recent history, with lava flows extending to the coast during events in 1922 and 1999 (Suh et al., 2001). These eruptions are typically less explosive, as the low viscosity of basaltic magma allows gases to escape easily.
However, explosive eruptions also occur in the CVL, particularly in areas with more evolved magmas such as trachytes and rhyolites. These eruptions, often associated with the formation of maars and calderas, have shaped the region’s crater lakes. The phreatomagmatic eruptions that formed Lake Nyos and Lake Monoun exemplify this type, where water-magma interactions result in violent explosions (Kling et al., 1987). Such eruptions are less frequent but pose significant hazards due to their unpredictability and potential for gas release. Furthermore, some volcanoes in the CVL, such as Mount Manengouba, show evidence of past Plinian eruptions—highly explosive events producing ash columns—though these are rarer and less documented in recent times (Marzoli et al., 2000). The coexistence of effusive and explosive eruption styles in the CVL highlights the complex volcanic dynamics of the region, though detailed eruption histories for many volcanoes remain incomplete due to limited monitoring infrastructure.
Conclusion
In summary, the Cameroon Volcanic Line presents a fascinating geological landscape defined by its volcanic mountains and crater lakes. The dominance of basaltic rocks across major mountains such as Mount Cameroon, Mount Manengouba, Mount Bambouto, and Mount Oku reflects the region’s alkaline magmatism, though variations in evolved rocks add complexity to its petrology. The lakes of the CVL, including Lake Nyos and Lake Monoun, are primarily formed through volcanic processes such as phreatomagmatic eruptions and caldera subsidence, with their unique characteristics posing both scientific intrigue and potential hazards. Additionally, the region exhibits a spectrum of eruption types, from effusive basaltic flows to explosive phreatomagmatic and Plinian events, shaping both the landscape and the associated risks. While this essay provides a broad overview of these features, it must be acknowledged that gaps in research—particularly regarding lesser-known volcanoes and lakes—limit a fully comprehensive analysis. Future studies, supported by enhanced monitoring and fieldwork, are essential to deepen our understanding of the CVL’s geological dynamics and to mitigate the risks posed by its active volcanic systems. Indeed, such efforts are crucial not only for academic advancement but also for the safety and sustainability of the communities living in this volatile region.
References
- Fitton, J.G. and Dunlop, H.M. (1985) The Cameroon Line, West Africa, and its bearing on the origin of oceanic and continental alkali basalt. Earth and Planetary Science Letters, 72(1), pp. 23-38.
- Kling, G.W., Clark, M.A., Compton, H.R., Devine, J.D., Evans, W.C., Humphrey, A.M., Koenigsberg, E.J., Lockwood, J.P., Tuttle, M.L. and Wagner, G.N. (1987) The 1986 Lake Nyos gas disaster in Cameroon, West Africa. Science, 236(4798), pp. 169-175.
- Marzoli, A., Piccirillo, E.M., Renne, P.R., Bellieni, G., Iacumin, M., Nyobe, J.B. and Tongwa, A.T. (2000) The Cameroon Volcanic Line revisited: Petrogenesis of continental basaltic magmas from lithospheric and asthenospheric mantle sources. Journal of Petrology, 41(1), pp. 87-109.
- Suh, C.E., Sparks, R.S.J., Fitton, J.G., Ayonghe, S.N., Annen, C., Nana, R. and Luckman, A. (2001) The 1999 eruption of Mount Cameroon: Insights into eruption dynamics from geophysical and petrological data. Journal of Volcanology and Geothermal Research, 114(1-2), pp. 157-182.
