Petrography and Geohazards of Fundong East(North West Region, Cameroon)

Abstract

Fundong is found North East of the Bamenda highlands and North West of Mt Oku along the CVL. It is located between latitude 6^o4’ and 6^o20’ North and longitude 10^o11’ and 10^o30’ East. This area is made up principally of basalts; some of which occur as lava flows and others as blocks of columnar basalt.

The columnar basalts make up about 75% of the entire basaltic rocks in the area. The basaltic rocks are mainly porphyritic basalts with the phenocrysts being olivine, pyroxenes and plagioclases in the ratios of 35% 30% 20% 15% respectively. The area hosts one major geohazard which is landslides and also rockfalls.

They are principally found along with the road cuts and cliffs of Mbam and Laikom. The events must have been facilitated by the steepness of the slopes, gravity and high rainfall and joints found in the rocks. The geohazards did not pose great problems to the community since no lives or properties were claimed.

However, it could be realised that these minor features although appearing to have been friendly, reduced the farmland space and disturbed communication especially as the sliding occurred along the roads. The slope and susceptibility map of this area reveals that the landscape varies enormously from flat to hilly pattern; West of Fujua is said to be flat unlike the East portion having an undulating nature. 

The southern sector which includes the West of the Laikom area and the entire Tiniformbi area is hilly and the landslide susceptibility is high. From the study, it could also be realised that some houses in the Mbam village are at risk and that these villagers also carry out agricultural activities on slopes such as farming and bush burning which could greatly activate or accelerate the occurrence of landslides in this area.

CHAPTER ONE

GENERAL INTRODUCTION

Background of the study

Humanity faces a big challenge today to obtain a balance in maintaining an optimum natural environment and in the use of land in the form of geohazards. Geohazards are geologic processes or events caused by natural phenomena that have the potential to bring about damage, loss or other adverse effects to those attributes valued by mankind.

They include earthquakes floods, landslides, volcanism, avalanches and tsunamis. One of the most common geohazards that have been recurrent in Cameroon is landslides; principally along the Cameroon volcanic line (CVL). Analysis of data from the last three decades shows an upward trend in the number of landslides in Cameroon.

Their impact on human beings, the environment and properties have increased considerably. For example; The landslide at Fossong-Wentcheng (South-West of Dschang) which took place on the 28th August 1978 killing six people (Tchoua 1984; 1989); at Limbe, the 27th June 2001, killing 24 people; that of Maga 20 July 2003, which led to 20 deaths (KagouDongmo, 2006; Zogning et al., 2007).

The September 12^th, 1992 landslide at Santa killed 12 people and atKekem 20 October 2007 with one death (Aboubakar etal., 2011). The Bamenda August 24^th 2004 landslide, where four kids were killed at Abangoh quarter (Lambi, 2004), and on the 4^th of August 2009, another kid was killed in an event in the Sisia neighbourhood (Ndi., 2010).

Also, the 4th of August 2009, saw a landslide that occurred in the proximity of the governor’s residence at “C-Bend” station hill preventing communication between Up Station and downtown. On the 6^th of August 2009, the national road (N11) linking the Western region and the North-west regional capital (Bamenda) was cut off after heavy rainfall (Geudjeo et al., 2013).

The reasons for this hazard in Cameroon are natural and anthropogenic. Among other natural factors, are the changing climatic conditions with the occurrence of very exceptional rainfalls and the uneven topography of the affected zones.

The anthropogenic factors are also very relevant; such as the increasing human pressure on the environment, characterized by the extension and intensification of the agro-pastoral activities (in the rural areas) as well as the settlement on the sloping zones. The landslides occur mainly during the peak of the rainy season from June to October.

Most of the occurrences are however not recorded, except when people are killed or appreciable property is destroyed (Lambi, 1991; Ayonghe et al, 1999). Records have therefore proven that landslides are the most predominant geohazards around the Bamenda volcanic area.

The  Bamenda volcanic area lies within the western high lands on the CVL between Mt Bambouto and Mt Oku. This part of the CVL consists mainly of the Bamenda Mountains and the Oku mountains (Aka et al., 2008). Fundong falls Northeast of the Bamenda highlands and Northwest of Mt Oku along the CVL (Figure 7).

Problem Statement

Several works have been carried out one the petrography of the Bamenda highlands and oku massif. But little information is available as concerns the petrography of its localities such as Fundong. The east area of Fundong has not only been modified by the geologic processes that accompanied the CVL but some anthropogenic processes as well such as constructions, resulting in its hilly nature.

Given that there is an increase in population and urbanization of Fundong in general, inhabitants have also turned to occupy risk areas for construction and farming since such areas are cheap and affordable. This work, therefore, seeks to identify the different petrographic rock types Fundong east, to add to existing information available about this area, and also to map out and characterize hazardous zones which will enable the decision-makers of this area to know suitable mitigation measures to implement.

Main Objective

The main objective of this work is to study the petrography and east.

Specific objectives

The specific objectives of this work are;

• To determine the different rock types Fundong east.
• Describe the different mass movements Fundong east.
• To contribute to the existing geologic information of this area.
• Propose and recommend measures that the Fundong council can use to mitigate future hazards.
• To determine the importance of this piece of work in teaching Geology in high schools.