The Lahars of the South-East slope of Mount Cameroon: geological study, economic interest and impacts of their exploitation on the environment

Abstract

Mount Cameroon is the site of explosive eruptions with the emission of ash, slag and lava flows. Mudflows, known as Lahars, can also be observed. These Lahars are mainly found in the lower part of the south-eastern slope. The outcrops observed on this flank show that these Lahars are very extensive and are avalanches of volcanic material, which flowed down the slopes of the volcano after the eruptions. The different outcrops observed are separated by pyroclastic products on which the lahars rest. The components of these lahars are generally black or grey basalts. The main granulometric characteristic of the deposits of these lahars is their heterometry. The size of the material varies from a few meters to the clay fraction. Large concentrations of mineable material are found in the watercourses. These materials are exploited in order to produce aggregates for civil engineering. This exploitation has consequences on the immediate environment. In addition to climatic factors, several parameters have influenced the mobilities and emplacement of the lahars on the south-eastern slope of Mount Cameroon: the slope, the volume and thickness of the deposits, the nature and physico-hydric characteristics of the deposits. The persistence of strombolian volcanic eruptions on Mount Cameroon and the particularly rainy context predispose it to other future episodes of lahar flow.