Hazards from Pyroclastic Density Currents at Mount Bamenda (West-Cameroon, Cameroon Volcanic Line): Mapping and Assessment by AMS Method

Pierre Kamgang,Emmanuel Njonfang,Merlin Gountié Dedzo,Ghislain Zangmo Tefogoum

doi:10.3844/ajgsp.2015.26.39

Abstract

Hazards related to pyroclastic density current continue to raise victims on many volcanoes in our planet. The Cameroon is not spared to this type of hazard because deposits of pyroclastic flows and surges are found on Mount Bamenda; products of this volcano are relatively young (27-0 Ma). Besides Mount Bamenda, Mounts Bambouto and Oku are the only volcanoes located in the central part of the Cameroon Volcanic Line where these ignimbritic deposits are found. Several factors highlight dangerousness and damage that can cause ignimbritic flows on the flanks of this volcano. This is essentially the high aspect ratio of these ignimbrites, the important population (about 750,000 people) that lives on the slopes and around the volcano. In order to have an idea of a nowadays ignimbritic eruption scenario on Bamenda volcano, the Anisotropy of Magnetic Susceptibility (ASM) method is used in this study to highlight the palaeoflow in ancient deposits of ignimbrites which are mostly discontinuous and isotropic. Results of AMS study are used to produce map of hazards and assess risks that may be related with such eruptions in Bamenda volcano.

Highlights

The Cameroon Volcanic Line (CVL) is characterized by alignment of oceanic and continental volcanic massifs and anorogenic plutonic complexes extending from Pagalu Island in the Atlantic Ocean to Chad with N30°E general orientation (Fig. 1)
The presence of pyroclastic density currents deposits justify the dangerousness of this volcano because it is still considered as an active volcano in the CVL with the basalts recently dated to 0 Ma (Kamgang et al, 2007)
Directional data of AMS study show a fairly reliable transport pattern in 6 sites inferred by magnetic foliation. These sites situated at Bambili, Mbu Mbengwi and Bamenda show well-defined magnetic fabrics characterized by mostly low plunges of the magnetic lineations (1 to 26°) and gently inclination of magnetic foliation planes (3 to 24°)

Summary

Introduction

The Cameroon Volcanic Line (CVL) is characterized by alignment of oceanic and continental volcanic massifs and anorogenic plutonic complexes extending from Pagalu Island in the Atlantic Ocean to Chad with N30°E general orientation (Fig. 1). Volcanism along this line began in the Eocene by the formation of Bamoun plateau between 51.8 and 46.7 Ma (Moundi et al, 2007) and Mount Bangou between 44.7 and 43.1 Ma (Fosso et al, 2005) and continues until the present day on Mount Cameroon (Suh et al, 2003). The Bamenda volcano covers an area of about 600 km and culminates at 2621 m (Bambili Lake borders) It is characterized by two elliptically shaped calderas (Fig. 2): Santa-Mbu caldera (6×4 km) and Lefo caldera (4×3 km). The presence of pyroclastic density currents deposits justify the dangerousness of this volcano because it is still considered as an active volcano in the CVL with the basalts recently dated to 0 Ma (Kamgang et al, 2007)

Objectives

Methods

Results

Discussion

Conclusion