Mapping and Assessment of Volcanic Hazards Related to the Ignimbritic Eruption by AMS in Bambouto Volcano (Cameroon Volcanic Line)
M. Gountie Dedzo
2013
Open Geology Journal
Pyroclastic deposits constitute major components of explosive volcanic activity. To help improve the safety of the population faced with natural disasters, a study is carried out at Bambouto volcano with a view to map potential hazards related to pyroclastic flows. The Bambouto volcano is indeed considered to be still active since the recent discovery of Quaternary basalts (0.5 Ma) at Totap, a locality situated near the Bambouto Caldera. This discovery has led to reclassify Mount Bambouto among
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... active volcanoes of Cameroon and, therefore, considered as potentially dangerous. The dangerousness of this volcano is accentuated by the presence of ignimbrites that are witnesses of ancient pyroclastic flows. Because a map of volcanic hazards is non-existent on the volcano, anisotropy of magnetic susceptibility (AMS) is the method used in this paper to characterize magnetic fabrics and provides an estimate of flow direction of each ignimbrite sheet (represented by massive lapilli tuff and massive lithic breccia facies). Inferred transport directions based on the AMS data and field indicators show that Bambouto Caldera is the source of main pyroclastic deposits of Mount Bambouto. These results have enabled us to produce a new hazard map related to potential future pyroclastic flows. villages, are located on the flanks of this large volcano (Fig. 3) . Mount Bambouto is probably a volcanic horst fed mainly by fissures, most with a NE-SW orientation. It is made up of volcanic products dated from 21.12 ± 0.45 Ma to 0.48 ± 0.014 Ma, and comprises basalts, trachytes, phonolites, rhyolite and ignimbritic deposits that form various facies [2] . The volcanological story of the Mount Bambouto can be subdivided into three main stages [1, 3]: The 1 st stage, ca. 21 Ma, was devoted to the building of a primitive shield volcano with alkaline basalts. The 2 nd stage, between 18.5 and 15.3 Ma, corresponds to the formation of the caldera in response to the large-volume eruptions of rhyolitic and trachytic magmas from a large, evolved, sub-volcanic magma reservoir and the formation of extensive ignimbrite sheets. The 3 rd stage renewed activity with effusive basanite to mugearite eruptions between 15.1 and 4.5 Ma, together with post-caldera extrusions of trachytes between 15 and 8.8 Ma, and of phonolites between 12.9 and 5.2 Ma. Basaltic (0.48 Ma) effusive activity of Totap could indicate the beginning of a fourth stage. Mount Bambouto has has been subjected to several catastrophic events of different origins over the past few years [4]: meteorological events such as landslides and rock © Gountié Dedzo et al.; Licensee Bentham Open. This is an open access article licensed under the terms of the Creative Commons Attribution Non-Commercial License (http://creativecommons.org/licenses/bync/3.0/) which permits unrestricted, non-commercial use, distribution and reproduction in any medium, provided the work is properly cited.
doi:10.2174/1874262901307010001
fatcat:u7sxtkkmkjbypbx5osmvxyvtne