Festus Tongwa Aka

Eruptive history of the Barombi Mbo Maar, Cameroon Volcanic Line, Central Africa: Constraints from volcanic facies analysis

Abstracthis study presents the first and detail field investigations of exposed deposits at proximal sections of the Barombi Mbo Maar (BMM), NE Mt Cameroon, with the aim of documenting its past activity, providing insight on the stratigraphic distribution, depositional process, and evolution of the eruptive sequences during its formation. Field evidence reveals that the BMM deposit is about 126m thick, of which about 20m is buried lowermost under the lake level and covered by vegetation. Based on variation in pyroclastic facies within the deposit, it can be divided into three main stratigraphic units: U1, U2 and U3. Interpretation of these features indicates that U1 consists of alternating lapilli-ash-lapilli beds series, in which fallout derived individual lapilli-rich beds are demarcated by surges deposits made up of thin, fine-grained and consolidated ash-beds that are well-defined, well-sorted and laterally continuous in outcrop scale. U2, a pyroclastic fall-derived unit, shows crudely lenticular stratified scoriaceous layers, in which many fluidal and spindle bombs-rich lapilli-beds are separated by very thin, coarse-vesiculatedash-beds, overlain by a mantle xenolith- and accidental lithic-rich explosive breccia, and massive lapilli tuff and lapillistone. U3 displays a series of surges and pyroclastic fall layers. Emplacement processes were largely controlled by fallout deposition and turbulent diluted pyroclastic density currents under “dry” and “wet” conditions. The eruptive activity evolved in a series of initial phreatic eruptions, which gradually became phreatomagmatic, followed by a phreato-Strombolian and a violent phreatomagmatic fragmentation. A relatively long-time break, demonstrated by a paleosol between U2 and U3, would have permitted the feeding of the root zone or the prominent crater by the water that sustained the next eruptive episode, dominated by subsequent phreatomagmatic eruptions. These preliminary results require complementary studies, such as geochemistry, for a better understanding of the changes in the eruptive styles, and to develop more constraints on the maar’s polygenetic origin.

Disaster prevention, disaster preparedness and local community resilience within the context of disaster risk management in Cameroon

Cameroon was one of the 57 countries that participated in the Global Network of Civil Society Organizations for Disaster Reduction (GNDR) Views from the Frontline (VFL) 2013 project on everyday disasters, community resilience and disaster preparedness. Working with 6 other civil society organizations, Geotechnology, Environmental Assessment and Disaster Risk Reduction administered 400 questionnaires to frontliners in 7 administrative regions of the country on 14 disaster indicators that assessed the underlying causes of disasters and the level of preparedness and resilience of the communities. Scores from the 89% of informants who responded show that Cameroon occupied the 43rd position globally, was 15th out of the 23 African countries, and was 7th out of the 9 West African countries surveyed. Cameroon average scores for all 14 indicators were lower (poorer) than the West African average, suggesting that a lot more effort is needed in managing disaster risks in the country, i.e., reducing vulnerabilities and increasing preparedness and resilience. At the national level, the Center and Adamaoua Regions recorded the lowest scores of the survey. Above-average scores recorded for some indicators in the Southwest, Northwest and Far North Regions are interpreted to be due to disaster prevention activities like monitoring via early warning systems, resilience building and outreach exercises carried out for disasters like landslides, floods, gas explosions from lakes, and volcanic eruptions, in these areas. Cameroon presently has many laws relating to disaster risk management matters, but an analysis of how the laws are applied shows that the expected results have not been attained, mainly because of over-centralization and a reactive, rather than a proactive approach to disaster risk management. Given her current disaster risk profile, Cameroon has to increase research, better manage, and make disaster risks a central tenet in her development project decision-making, if the goal earmarked in her development vision to become a newly industrialized country by 2035 has to be realized. We propose the creation of an autonomous statutory National Disaster Risk Management Agency which will have a local community-driven bottom-top approach to disaster risk management, and disseminate appropriately tailored disaster risk information to promote a proactive community-based resilience and disaster prevention framework. This will fulfill the post-2015 Sendai framework priority of action No. 2 (strengthening disaster risk governance to manage disaster risk) and appropriately prepare Cameroon to face the challenges of the Sustainable Development Goals (SDGs).