**1. Introduction and geological context**

Internal geodynamics is manifested on the Earth's surface by volcanic phenomena. Most of these phenomena are controlled by volcanoes located in the tectonically and structurally weak areas of the globe, notably accretion zones, convergence zones, and intra-plate zones. Some of these volcanoes are characterized by a simple crater, while others have one or more complex craters (distinguished by the collapse events). These complex craters are defined by one or more calderas [1–4]. The term caldera derives from the depression called Taburiente (Canary Islands) and has been firstly used by [5]. The Caldera de Taburiente in fact, is the frequently quoted example of erosion caldera. Erosion calderas are volcanic depression erosionally formed on the summit or on the flanks of the volcano, which may be several kilometers in diameter [6–8]. However, geologically, calderas are volcanic depressions resulting from the collapse of the roof of the magma chamber due to the rapid

retreat of the magma during an eruption [9, 10]. They can be elliptical, sub-circular or circular in map view. These shapes are induced by the shape of the underlying magma reservoir [11, 12]. In Refs. [9, 13], five types of collapse such as *piston, piecemeal, trapdoor, downsag,* and *funnel* have been defined to ease the comprehension of the caldera formation processes.

Nevertheless, insufficient work on the dynamics of caldera emplacement limits the understanding of the functioning and evolution of volcanic massifs worldwide. Some calderas deserve to be characterized according to the models of [9] and [13] in order to classify them according to the Collapse Caldera DataBase established by [14]. The Collapse Caldera DataBase makes it possible to better study the caldera formation processes and to classify them. The study of calderas for decades has been of paramount importance for the development of science; it allows us to understand the functioning of volcanic apparatus around the world and the environmental impact that can result from them. Since calderas constitute a natural heritage for the economic development of several countries and a laboratory for education and research [15–17], their classification will heighten their promotion and valorization.

Mount Bambouto, which was once a very active volcano, was truncated at their summit by a caldera like some volcanoes along the Cameroon Volcanic Line (**Figure 1**). It caldera was chosen for the present study because Mount Bambouto have been the subject of numerous studies focusing mainly on petrography, geochemistry, geochronology, geo-heritage, hazards and associated risks [18–29]. With the exception of [20, 21, 29], the studies on the caldera of Mount Bambouto are generally carried out in the specific areas [22, 30, 31]. Mount Bambouto is the third largest volcano (in volume) in the Cameroon Volcanic Line after Mount Cameroon and Mount Manengouba. It is located in the NE extension of Mount Manengouba from which it is separated by the Mbô plain. It is almost continuously contiguous to the NE with Mount Bamenda and covers an area of about 800 km<sup>2</sup> . It is located between longitudes 09°55′ and 10°15′E and latitudes 05°25′ and 05°50′N. They straddle the Departments of Bamboutos in the East, Menoua in the South, Lebialem in the West and Mezam in the NW and, culminate at 2744 m at Meletan Mountain where they dominate the West Cameroon Highlands. Mount Bambouto is a huge shield volcano with a general SW-NE orientation [18]. This massif is characterized by the asymmetry of its slopes [32]. Its summit caldera is located between longitudes 09°57′ and 10°07′E and latitudes 05°37′ and 05°44′N. The Caldera of the Mount Bambouto has an elliptical map view (16 × 8 km) that opens in a horseshoe shape toward the west (**Figure 2**). Throughout the caldera, rocks (basalts, hawaiites, mugearites, phonolites, trachytes, and ignimbrites) are found in different forms: flows, domes, peaks, teeth and needles that characterize the interior, the external slopes and the floor of the caldera. Thus, the inside of the caldera is marked by a sinuous "s" line punctuated by trachytic and phonolitic peaks, necks, and domes [18, 20, 29]. Moreover, the crystalline basement made up of granite, is observed on the western side of the volcano [21, 22, 29]. The floor of the caldera has a structure of stairs decreasing from the east to the west of the massif. The caldera rims are sub-vertical to vertical. In addition, several steep valleys (in "v" shape) accidentally affect the topography of the whole caldera (about 78% of the slopes are susceptible to mass movements) [29].

Despite these previous studies, the dynamics of the establishment of the caldera of the Mount Bambouto remains poorly understood. Moreover, that caldera is not yet classified in the Caldera DataBase established by [10]. However, some data do exist on this caldera. These data need to be completed and this will allow us to characterize that caldera according to the model of [9]. This characterization will make it possible to obtain and organize the data in order to classify the caldera of the Mount Bambouto in the Caldera Database of [14]. This work is essential for

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**Figure 2.**

*Satellite image of the Mount Bambouto caldera.*

**Figure 1.**

*The Cameroon volcanic line.*

*The Caldera of Mount Bambouto: Volcanological Characterization and Classification*

*DOI: http://dx.doi.org/10.5772/intechopen.93694*

*The Caldera of Mount Bambouto: Volcanological Characterization and Classification DOI: http://dx.doi.org/10.5772/intechopen.93694*

**Figure 1.** *The Cameroon volcanic line.*

*Updates in Volcanology – Transdisciplinary Nature of Volcano Science*

the caldera formation processes.

retreat of the magma during an eruption [9, 10]. They can be elliptical, sub-circular or circular in map view. These shapes are induced by the shape of the underlying magma reservoir [11, 12]. In Refs. [9, 13], five types of collapse such as *piston, piecemeal, trapdoor, downsag,* and *funnel* have been defined to ease the comprehension of

Nevertheless, insufficient work on the dynamics of caldera emplacement limits the understanding of the functioning and evolution of volcanic massifs worldwide. Some calderas deserve to be characterized according to the models of [9] and [13] in order to classify them according to the Collapse Caldera DataBase established by [14]. The Collapse Caldera DataBase makes it possible to better study the caldera formation processes and to classify them. The study of calderas for decades has been of paramount importance for the development of science; it allows us to understand the functioning of volcanic apparatus around the world and the environmental impact that can result from them. Since calderas constitute a natural heritage for the economic development of several countries and a laboratory for education and research [15–17], their classification will heighten their promotion and valorization. Mount Bambouto, which was once a very active volcano, was truncated at their summit by a caldera like some volcanoes along the Cameroon Volcanic Line (**Figure 1**). It caldera was chosen for the present study because Mount Bambouto have been the subject of numerous studies focusing mainly on petrography, geochemistry, geochronology, geo-heritage, hazards and associated risks [18–29]. With the exception of [20, 21, 29], the studies on the caldera of Mount Bambouto are generally carried out in the specific areas [22, 30, 31]. Mount Bambouto is the third largest volcano (in volume) in the Cameroon Volcanic Line after Mount Cameroon and Mount Manengouba. It is located in the NE extension of Mount Manengouba from which it is separated by the Mbô plain. It is almost continuously contiguous to the NE with Mount Bamenda and covers an area of about 800 km<sup>2</sup>

is located between longitudes 09°55′ and 10°15′E and latitudes 05°25′ and 05°50′N. They straddle the Departments of Bamboutos in the East, Menoua in the South, Lebialem in the West and Mezam in the NW and, culminate at 2744 m at Meletan Mountain where they dominate the West Cameroon Highlands. Mount Bambouto is a huge shield volcano with a general SW-NE orientation [18]. This massif is characterized by the asymmetry of its slopes [32]. Its summit caldera is located between longitudes 09°57′ and 10°07′E and latitudes 05°37′ and 05°44′N. The Caldera of the Mount Bambouto has an elliptical map view (16 × 8 km) that opens in a horseshoe shape toward the west (**Figure 2**). Throughout the caldera, rocks (basalts, hawaiites, mugearites, phonolites, trachytes, and ignimbrites) are found in different forms: flows, domes, peaks, teeth and needles that characterize the interior, the external slopes and the floor of the caldera. Thus, the inside of the caldera is marked by a sinuous "s" line punctuated by trachytic and phonolitic peaks, necks, and domes [18, 20, 29]. Moreover, the crystalline basement made up of granite, is observed on the western side of the volcano [21, 22, 29]. The floor of the caldera has a structure of stairs decreasing from the east to the west of the massif. The caldera rims are sub-vertical to vertical. In addition, several steep valleys (in "v" shape) accidentally affect the topography of the whole caldera (about 78% of the slopes are

Despite these previous studies, the dynamics of the establishment of the caldera of the Mount Bambouto remains poorly understood. Moreover, that caldera is not yet classified in the Caldera DataBase established by [10]. However, some data do exist on this caldera. These data need to be completed and this will allow us to characterize that caldera according to the model of [9]. This characterization will make it possible to obtain and organize the data in order to classify the caldera of the Mount Bambouto in the Caldera Database of [14]. This work is essential for

. It

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susceptible to mass movements) [29].

**Figure 2.** *Satellite image of the Mount Bambouto caldera.*

understanding the functioning and evolution of the Mount Bambouto and, consequently, the dynamics of the Cameroon Volcanic Line, which remains a subject of discussion by many researchers nowadays.
