The Caldera of Mount Bambouto: Volcanological Characterization and Classification

Mount Bambouto culminates at 2744 m (Meletan Mountain) where an elliptical caldera of 16 × 8 km is found. Although that caldera has been a subject of numerous scientific works, complementary studies were needed to bring out additional data used to classify it through the Caldera DataBase of Geyer and Marti (2008). It emerges that Bambouto Caldera codes are 2 and 203 because it is respectively located in Africa and Central Africa according to the numbering system developed in the Catalog of Active Volcanoes of the World. The collapse type of the caldera is piecemeal; this relies on the fact that the caldera floor is uneven. Several rocks crop out in the caldera; accordingly, its code is B, I, T, P, and Ig viz. basalts, intermediate rocks, trachytes, phonolites, and ignimbrites. Bambouto depression is the ignimbrite caldera because it is associated with thick ignimbrite sheer, that ruled its collapse. The chemical analysis of rocks reveals that the magmatic series of Bambouto Caldera is of alkaline type. It has been built through the continental rifting of extensional type (RC-EXT). The collapse process has been followed by post-caldera protrusion of trachytic and phonolitic domes; then, its codes are Type-S and type-MS

Tracking Airborne Pollution with Environmental Magnetism in A Medium-Sized African City

International audienceThis article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC B

The geodiversity of Lefo and Santa-Mbu Calderas (Bamenda Mountains, Cameroon Volcanic Line): Factor for socioeconomic activities

Lefo and Santa-Mbu calderas are located on the Bamenda Mountains. They are two geological structures that accompanied the construction of the Bamenda Mountains. The geological processes that accompanied their collapse gave them a significant number of geological features. These elements, known as geodiversity components, constitute real assets for ecosystem services in these more or less populated volcanic environments. The present work aims to highlight the ecosystem services of these two calderas in relation to the socio-economic activities they govern. To this end, field and laboratory work was carried out. They revealed that the ecosystem services of the two calderas include: (1) regulation services because the calderas are covered in places by forest reserves, notably that of Bali Ngemba and Bafut Ngemba, and by a grassland with trees that play a crucial role in climate regulation. In addition, these areas are subject to natural hazards such as mass movements and volcanic eruptions; (2) supporting services as they provide a base for human activities, a habitat for wildlife species; (3) provisioning services because the calderas have fairly fertile soils that favour a fairly diversified agricultural activity, making the floor of the Lefo caldera a coffee growing area. These calderas are covered by a herbaceous grassland that favours pastoral activity in the region. In addition, the rocks of these calderas are used in construction, especially in the foundations and walls of houses; (4) cultural services as they provide a setting for traditional ritual practices and plants with therapeutic properties. In addition, it has several geomorphosites whose scientific and additional values favour the implementation of geotourism and offer geological features that are indispensable for the understanding and functioning of the Volcanic Line of Cameroon. These calderas are undeniable assets for the balance of the ecosystem

Importance of Rocks and Their Weathering Products on Groundwater Quality in Central-East Cameroon

The present work highlights the influence of lithology on water quality in Méiganga and its surroundings. The main geological formations in this region include gneiss, granite and amphibolite. The soils developed on these rocks are of ABC type, which are acidic to slightly acidic. Electrical conductivity (EC), organic matter, total nitrogen, nitrate-nitrogen, sulfate, chloride, phosphorus and exchangeable base values were low to very low in the soil samples. Groundwater samples were investigated for their physicochemical characteristics. The wide ranges of EC values (15.1–436 µS/cm) and total dissolved solids (9–249 mg/L) revealed the heterogeneous distribution of hydrochemical processes within the groundwater of the area. The relative abundance of major dissolved species (mg/L) was Ca2+ > Na+ > Mg2+ > K+ for cations and HCO3− >> NO3− > Cl− > SO42− for anions. All the groundwater samples were soft, with total hardness values (2.54–136.65 mg/L) below the maximum permissible limits of the World Health Organization (WHO) guideline. The majority of water samples (67%) were classified as mixed CaMg-HCO3 type. Alkaline earth metal contents dominated those of alkali metals in 66.66% of samples. Thus, for the studied groundwater, Mg2+ and Ca2+ ion adsorption by clay minerals was almost nonexistent; this implies their release into the solution, which accounts for their high concentrations compared to alkali metals. Ion geochemistry revealed that water-rock interactions (silicate weathering) and ion exchange processes regulated the groundwater chemistry. One water sample points towards the evaporation domain of this diagram, indicating that groundwater probably does not originate from a deeper system. Kaolinite is the most stable secondary phase in the waters in the study area, in accordance with the geochemical process of monosiallitization, which predominated in the humid tropical zone