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Schematic presentation of the sublacustrine fluid reservoir which is encircled by gray line. The geological cross section of Lake Nyos was taken from Lockwood and Rubin (1989). Arrow with white head indicates the flow of groundwater, and that with black head indicates magmatic fluid coming from magma underneath. Noble gas and carbon isotopic ratios of respective reservoirs are shown
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Lakes Nyos and Monoun in Cameroon are known as “killer lakes” because they killed ˜1,800 people in the mid-80s after a gas explosion or limnic eruption, a sudden release of carbon dioxide accumulated in deep waters. This event attracted the interest of the international scientific community, not only for the sake of disaster mitigation but also for...
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... Degassing of CO 2 at volcanic lakes is mainly linked to the sudden and potentially fatal "Nyos-type" gas release, i.e. by lake rollover upon CO 2 supersaturation in deep lake strata, or upon an external trigger (e.g. earthquake, landslide) (Sigurdsson et al., 1987;Kling et al., 1987;Kusakabe, 2015Kusakabe, , 2017. Nevertheless, as CO 2 is the most abundant dry gas species at degassing volcanoesfrom purely magmatic to hydrothermal systemsa myriad of alternative degassing mechanisms is possible, depending on the physical-chemical characteristics of the lake the gas is flushing through: (1) acid crater lakes (pH < 3.4) topping the most active volcanoes are chemically transparent to CO 2 , which will be released from the lake surface tal qual as it enters at the lake bottom Tamburello et al., 2015;Shinohara et al., 2015;de Moor et al., 2016;Gunawan et al., 2017;Battaglia et al., 2019), (2) hyper-acid (pH < 2) and hyper saline crater lakes affected by high seasonal rainfall can "coat" the lake surface by cold, less dense and less acid waters to create CO 2 accumulation under its "skin" to eventually be hazardously released as a gas beracun (e.g. ...
... Our calculation yields a total dissolved CO 2(aq) ranging from ~109 to ~176 tons ( Fig. 5ab). For comparison, Lake Monoun and Lake Nyos accumulated prior to and released during their limnic eruptions ~26,000 and ~ 650,000 tons of CO 2 in the mid-80s, respectively (Kusakabe, 2015). We argue that the amount of CO 2 stored in Lagoa das Furnas unlikely threatens the local population. ...
... Limnic eruptions around the lakes of Monoun and Nyos led to around 40 and 1700 fatalities, respectively (Faivre Pierret et al., 1992;Kling et al., 1987;Kusakabe et al., 2000Kusakabe et al., , 1989Sigurdsson et al., 1987;Folch et al., 2017). In the case of a potential limnic eruption at lake Pavin, the current body of CO 2 stored in the lake (450 tons) is significantly below the that involved at lake Nyos (about 4 Mt. in January 2011; Halbwachs et al., 2020;Kusakabe, 2015) and Monoun (about 17 kt in January 2011; Kusakabe, 2015). Nevertheless, our study highlights that under some conditions (summer season and exponential flux), densely populated areas (i.e., the municipality of Besse-et-Saint-Anastaise), 3 km from lake Pavin, may be reached by the CO 2 cloud. ...
... Limnic eruptions around the lakes of Monoun and Nyos led to around 40 and 1700 fatalities, respectively (Faivre Pierret et al., 1992;Kling et al., 1987;Kusakabe et al., 2000Kusakabe et al., , 1989Sigurdsson et al., 1987;Folch et al., 2017). In the case of a potential limnic eruption at lake Pavin, the current body of CO 2 stored in the lake (450 tons) is significantly below the that involved at lake Nyos (about 4 Mt. in January 2011; Halbwachs et al., 2020;Kusakabe, 2015) and Monoun (about 17 kt in January 2011; Kusakabe, 2015). Nevertheless, our study highlights that under some conditions (summer season and exponential flux), densely populated areas (i.e., the municipality of Besse-et-Saint-Anastaise), 3 km from lake Pavin, may be reached by the CO 2 cloud. ...
Risk mitigation in long-dormant volcanic provinces is a challenge due to the absence of collective memory of past disasters as well as the scarcity, and subtlety, of unrest signals that can be monitored. In this study, the impact of a potential limnic eruption is assessed at the 92-m-deep lake Pavin (French Massif Central). The lake is hosted in a maar crater formed during the last eruptive event in metropolitan France (~7 ka) and contains dissolved CO2 in the deepest water layer, below 60 m. Carbon dioxide (CO2) emissions measured at the lake surface (0.44 km 2) reach up to 10.1 tons/day during the winter. Beyond this (limited) continuous degassing of the lake, the current CO2 budget in the monimolimnion layer (at a depth of 60 m to 92 m) was estimated at 1750 tons, of which about 450 tons are available for release in case of overturn of the lake. Scenarios for CO2 dispersion in the lower atmosphere were simulated with the DISGAS and TWODEE-2 models by varying (i) meteorological conditions, (ii) the amount of CO2 released, (iii) and the mechanisms of degassing during a potential limnic eruption. The simulations allowed identification and delimitation of areas potentially impacted by hazardous CO2 levels in the air down-valley from the lake and directly around the lake. The spatio-temporal evolution of the potential CO2 cloud raises issues regarding the impacts of such a hypothetical event in the close vicinity of the lake and, given the area is populated and highly visited, needs to be considered in future risk mitigation strategies.
... Difficulties arise in volcano crater lake monitoring with drawbacks in accessing the target location. Data from vol-cano monitoring provide essential information that helps researchers in forecasting possible disasters [8], [9], [10]. The utilization of Unmanned Aerial Systems applications, in this case, reveals favorable results in close monitoring. ...
Water sampling is a fundamental practice for obtaining essential environmental data, enabling the analysis and quality testing of water from natural or industrial sources. It plays a vital role in understanding water quality changes over time, identifying contaminant sources, and supporting water management plans. Traditional sampling methods, including spot (bottle) sampling and in-situ readings, can be labor-intensive and limited by accessibility. To address these challenges, the utilization of drones equipped with specialized sensors and sampling devices has emerged as an innovative and efficient approach. Drones offer the potential to automate field quality control and streamline water sampling efforts, providing a cost-effective and comprehensive solution for data collection in diverse water environments. This paper focuses on the design and development of a water sampling system integrated with a drone, featuring an automatic lock mechanism activated after rigorous field quality control, ensuring the reliable collection of water samples in various scenarios.
... After 1986, many monitoring efforts revealed the ongoing CO 2 -recharge at both Lakes Nyos and Monoun (Kusakabe et al., 1989(Kusakabe et al., , 2000Evans et al., 1993). Such observation confirmed the spontaneous gas release as the most plausible eruption mechanism and suggested a highly probable future recurrence of these events (Kusakabe, 2015(Kusakabe, , 2017. This awareness gave rise to the unique disaster risk reduction intervention through artificial degassing of both "killer lakes" in Cameroon (Halbwachs et al., 2020 and references therein). ...
... The 1986 limnic gas burst was characterized by the change in the color of the lake (dark red, Fig. 2), suffocation by CO 2 of magmatic origin causing nearly 1800 deaths, and the overflow of the lake. During the years after the gas catastrophe, the dissolved CO 2 content in deep lake layers increased due to the continuous supply of magmatic CO 2 (Kusakabe, 2015(Kusakabe, , 2017. To prevent another explosion in the future, artificial degassing was launched (Halbwachs et al., 1993Tanyileke et al., 2019). ...
... The model by Ohba et al. (2022) implies that supersaturation conditions of dissolved CO 2 in deep waters are not necessary for the lake to explode. Hence, a limnic eruption at Lake Monoun may be independent of the CO 2 -recharge rate, which shows a fairly constant increase with an estimated 8.4 Mmol/year (Kusakabe, 2015(Kusakabe, , 2017, and recurrence can be more frequent than previously thought. In fact, based on oral traditions, Shanklin (1989) reports on "maleficent" lake behavior in the Monoun area, arguably pointing to limnic gas burst in the past in recent history. ...
... The geological history of the Mfouet Lake sector is as follows: First of all, thanks to the fractures of the basement, the basaltic lava spilled out on the surface in vast sheets and consolidated into plateau basalts. Then the climate of the geomorphological situation of the plain between the Bamiléké and Bamoun plateaus, as well as the circulation of water in the faults of the Pan-African granito-gneissic substratum, (Wandji, 1995) This site is representative of the regional geomorphology and is an exemplary entity 0.75 Rareness It is a fairly frequent form in the region, however, its color, structure and geometric configuration differs from others entities present in the region Villevielle, 1993; Halbwachs et al., 2004;Kling et al., 2005;Kusakabe, Tanyileke, McCord, & Scladow, 2000;Nagao, Kusakabe, Yoshida, & Tanyileke, 2010;Issa et al., 2013;Kozono et al., 2016;Saiki et al., 2016;Yoshida, Issa, Satake, & Ohba, 2010;Yoshida, Kusakabe, Issa, Tanyileke, & Hell, 2016;Kusakabe, 2015Kusakabe, , 2017, which earned it an international status. ...
... The first layer (epilimnion) extends from 0 to −55 m where water is mixed convectively per year during the dry season. Due to exchange with the atmosphere and dilution by rainwater, this layer has a low carbon dioxide (CO 2 ) concentration and low electrical conductivity [8] . The second layer (metalimnion) extends from −55 m to −180 m and the third layer (hypolimnion) from −180 m to −200 m. ...
On August 15, 1984 at Lake Monoun and on August 21, 1986 at Lake Nyos, 37 and 1,746 people, respectively, died from gas fumes. Lakes Monoun and Nyos are peculiar aquatic ecosystems located on the Cameroon Volcanic Line, a strategic site, which continue to draw the attention of scientists, stakeholders, policy makers, public authorities as well as local communities and indigenous. It has been clearly demonstrated that these two lakes store large quantities of toxic gases in dissolved form in their bottom. Indeed, the extremely diverse microbial communities that colonizes these lakes are capable of producing, storing and releasing gases. These particularities have earned these lakes the name "killer lakes". Although relevant results have been obtained after the installation of degassing devices on these lakes, these results are less popularized and Cameroonian society, in particular natives of the disaster-stricken areas have remained skeptic and divided on the origin of gases : 9.4% of survivors and residents interviewed said it was a nuclear test. Also, 78.13% supported the thesis of a mystical-religious phenomenon. Only 12.47% of the interviewees understood that it was a scientifically explainable phenomenon. Clearly, the gap between science, scientists and societies is quite perceptible. Based on the deadly catastrophes of these two lakes, we present here the fracture that exists between science and African societies still anchored in indigenous beliefs.
... The degassing pipe installed in Lake Nyos has an inside diameter of 0.14 m, corresponding to the blue curve in Fig. 4. According to Kling et al. (2005), the concentration of CO 2 (mass fraction) at bottom of the Lake Nyos is 0.018 during the degassing process, with an observed eruption height of 50 m. As shown by arrows A-B and B-C in Fig. 4, when the CO 2 concentration at the intake point of the degassing pipe is 0.018 (Kusakabe, 2015), the simulated eruption height is 48.12 m, indicating that the simulated result has good agreement with the on-site observation. ...
... In the case that the eruption height is only 50 m as observed in the real degassing process, the corresponding CO 2 concentration at the bottom of the lake is only 0.018 (shown by D-E-F.), much less than the saturated CO 2 concentration of 0.030. It should be pointed out that this doesn't mean the lake does not subject to an eruption because the water may saturated with CO 2 at a depth of 100 m before the 1986 lake eruption (Kusakabe, 2015). However, if the eruption height becomes higher than 100 m and especially when it has an even greater eruption height towards its upper-limit, an "eruption warning" should be given in time for safety. ...
Gas-driven limnic eruption can happen in a lake with an aqueous gas solution that becomes supersaturated due to some reason. In this case, the exsolution of massive gases dissolved in the water could occur in a very short time, resulting in a disaster as happened in the Lake Nyos (Cameroon, Africa) in 1986. Using degassing pipe to artificially release the dissolved gases is a good way to minimize the risk of an eruption. In this study, a transient multi-component gas-liquid two-phase flow model of the degassing pipe used in Lake Nyos has been established and verified with the observed eruption data. The drift flux model has been used for modelling of a transient multi-component gas-liquid flow formed due to the spontaneous exsolution of gases dissolved in the water inside the degassing pipe. The governing equations for the mechanistic drift model include continuity equation for each phase, a single momentum equation for a homogeneous mixture of the fluid, constitutive equations for mass transfer rates between the phases, and the drift velocity formulas. The model considered not only CO2 but also CH4 as dissolved gases. The “chain reaction” conjecture predicted to have the degassing-point migrating downward with time during the transient degassing process is verified by using this model. The relationship between the eruption height and the CO2 concentration at the bottom of the degassing pipe has been simulated in detail. This relationship supplies people with a quick and convenient way to estimate the CO2 concentration in the lake, based on which one can evaluate the risk of lake eruption and hence to formulate or adjust the degassing plan. In addition, the effects of diameter and equivalent roughness of the degassing pipe on the eruption height has been investigated. Meanwhile, the eruption height upper-limit in different lake-depth scenarios has also been determined. Finally, the role of CH4 component in the degassing process has been analyzed. Although the influence of CH4 on eruption height can be neglected in Lake Nyos' case, CH4 as a dissolved gas plays an important role at Lake Kivu. The multi-component gas-liquid flow model developed in this study is useful to study the role of CH4 in the degassing process.
... (5) the degassing dynamics of the 1984 and 1986 gas bursts (Freeth and Kay, 1987;Sigurdsson et al., 1987;Barberi et al., 1989;Kanari, 1989;Tazieff, 1989;Freeth, 1990;Freeth, 1992;Evans et al., 1993;Freeth, 1994); (6) the hazard assessment mainly based on the chemistry of lake water and dissolved gases (Sano et al., 1987Tuttle et al., 1987;Kling et al., 1989;Kusakabe et al., 1989Kusakabe et al., , 2000Kusakabe et al., , 2008Lockwood and Rubin, 1989;Giggenbach, 1990;Nojiri et al., 1990Nojiri et al., , 1993Faivre Pierret et al., 1992;Kusakabe and Sano, 1992;Tietze, 1992;Evans et al., 1993Evans et al., , 1994Kantha and Freeth, 1996;Tanyileke et al., 1996;Nagao et al., 2010;Yoshida et al., 2010;Issa et al., 2014;Tassi and Rouwet, 2014;Anazawa et al., 2019;Kusakabe et al., 2019); (7) the risk mitigation through artificial degassing (since 2001, intensified since 2011 and ongoing; Halbwachs and Sabroux, 2001;Halbwachs et al., 1993Halbwachs et al., , 2004Halbwachs et al., , 2020McCord and Schladow, 1998;Schmid et al., 2003Schmid et al., , 2004Schmid et al., , 2006Kling et al., 2005;Ohba et al., 2017;Saiki et al., 2017;Yoshida et al., 2017); (8) the dam stability and its recent (2014-2015) reinforcement (Lockwood et al., 1988;Freeth and Rex, 2000;Aka et al., 2008;Aka and Yokoyama, 2013;Fantong et al., 2015;Tanyileke et al., 2019); (9) the topic of numerous projects (e.g. NyMo degassing, France-Cameroon; SATREPS, Japan-Cameroon), studies and review papers (Aka, 2015;Kling et al., 2015;Kusakabe, 2015Kusakabe, , 2017Tanyileke et al., 2019). ...
Volcanic lakes pose specific hazards inherent to the presence of water: phreatic and phreatomagmatic eruptions, lahars, limnic gas bursts and dispersion of brines in the hydrological network. Here we introduce the updated, interactive and open-access database for African volcanic lakes, country by country. The previous database VOLADA (VOlcanic LAke DAta Base, Rouwet et al., Journal of Volcanology and Geothermal Research, 2014, 272, 78–97) reported 96 volcanic lakes for Africa. This number is now revised and established at 220, converting VOLADA_Africa 2.0 in the most comprehensive resource for African volcanic lakes: 81 in Uganda, 37 in Kenya, 33 in Cameroon, 28 in Madagascar, 19 in Ethiopia, 6 in Tanzania, 2 in Rwanda, 2 in Sudan, 2 in D.R. Congo, 1 in Libya, and 9 on the minor islands around Africa. We present the current state-of-the-art of arguably all the African volcanic lakes that the global experts and regional research teams are aware of, and provide hints for future research directions, with a special focus on the volcanic hazard assessment. All lakes in the updated database are classified for their genetic origin and their physical and chemical characteristics, and level of study. The predominant rift-related volcanism in Africa favors basaltic eruptive products, leading to volcanoes with highly permeable edifices, and hence less-developed hydrothermal systems. Basal aquifers accumulate under large volcanoes and in rift depressions providing a potential scenario for phreatomagmatic volcanism. This hypothesis, based on a morphometric analysis and volcanological research from literature, conveys the predominance of maar lakes in large monogenetic fields in Africa (e.g. Uganda, Cameroon, Ethiopia), and the absence of peak-activity crater lakes, generally found at polygenetic arc-volcanoes. Considering the large number of maar lakes in Africa (172), within similar geotectonic settings and meteoric conditions as in Cameroon, it is somewhat surprising that “only” from Lake Monoun and Lake Nyos fatal CO2 bursts have been recorded. Explaining why other maars did not experience limnic gas bursts is a question that can only be answered by enhancing insights into physical limnology and fluid geochemistry of the so far poorly studied lakes. From a hazard perspective, there is an urgent need to tackle this task as a community.
... The Eruption can happen if high gas fluxes from magma find favourable conditions for gas accumulation into lake waters, gaseous. Lakes Nyos and Monoun (Cameroon) and Kivu (Republic Democratic of Congo) are the only three crater lakes in the Africa known to be rich in dissolved CO 2 [1]. Catastrophic CO 2 outgassing occurred on 15 th August 1984 at Lake Monoun and on 21 st August 1986 at Lake Nyos, killing 37 and 1746 people, respectively [2] [3] [4] [5]. ...
... Until now, scientific researches on these two lakes have mainly focused on the age of the gases at the origin of the disaster, the reverse of the CO 2 supersaturated hypolimnion [6] [7], the composition and concentrations of the physico-chemical elements [1], the escape chronology of gases, the presence of isotopes and rare gases [8], and the degassing process [9]. In the two lakes, data on biological communities, mainly those on microbial assemblages are scarce, with no interest regarding the communities of viruses. ...
This study explores the diversity and structure of prokaryotic communities (Archaea and Bacteria) of 2 tropical volcanic lakes (Nyos and Monoun) in Cameroon, using 16SrRNA sequences. Metagenomics analysis of sequences showed that most OTUs (Operational Taxonomic Units) were associated with 26 phyla (23 for Bacteria and 3 for Archaea) in Nyos and 36 phyla (33 for Bacteria and 3 for Archaea) in Monoun. In both lakes, Proteobacteria for Bacteria and Crenarchaea for Archaea were predominant and present at all depths but in different proportions. Bacterial community compositions were generally dominated by members of Proteobacteria, Firmicutes, Actinobacte-ria, Chloroflexi and Bacteroidetes covering about 98% of the sequences. Cre-narchaea, Thaumarchaea and Euryarchaea were the three main phyla of Arc-haea common to both lakes. The amount of virus and total bacteria was determined by flow cytometry technic and the evaluated ratio ranged from 0.2 to 1.2 at Nyos and from 0.6 to 2.6 at Monoun. For both lakes, the correlation was very significant between viruses and total bacteria. The depth-dependent variability is discussed with chemical and physical environmental parameters. These could significantly influence virus-mediated bacterial lysis and abundance and vertical stratification of the prokaryotic community.
... ROUWET et alii (2019) proposed that Lago Albano is instead an "anti-Nyos-type" lake, for being suddenly recharged with CO 2 (vs. a continuous CO 2 input at Lake Nyos; EVANS et alii, 1993;KUSAKABE, 2017), and with a periodical CO 2 release during winter overturn events (vs. sudden gas bursts at Lake Nyos following CO 2 saturation; KUSAKABE, 2015KUSAKABE, , 2017. ...
With this study a nine-year hiatus (May 2010-April 2019) in the quantification of the CO2 content of Lago Albano by our working group has been resolved through the acquisition and analysis from two new field campaigns. Based on a CO2 budget analysis the dynamics of CO2 degassing throughout the past thirty years (1989-2019) is detailed and quantified. The decreasing CO2 content (expressed as dissolved inorganic carbon, DIC) in the lake, since the co-seismic CO2 input during the 1989-1990 seismic swarm beneath Colli Albani volcano, was accelerated at lake bottom layers (-140 m to bottom, near -160 m) in the 4-5 years after the swarm, continued afterwards at lower depths (-125 to -95 m), and seems to have reached steady-state conditions during recent years. The peculiar lake basin morphology has control on the degassing dynamics. The low chemical gradients detected during the April 2019 survey have induced near-zero degassing conditions, and arguably stopped the gas-self lifting process: Lago Albano might not become CO2-free in the future. This finding has implications for gas hazard when the next seismic swarm will hit the area. The updated degassing model also takes into account the lake level drop, and hence the volume decrease of Lago Albano, caused by excessive well pumping for anthropic purposes. This volume decrease appears to have a destabilizing effect on the degassing dynamics, which renders Lago Albano's gas release less predictable in the future. Enhanced gas surveys (high-frequency and fine-scale spatial measurements) are needed to shed light on how Lago Albano degasses in this quiescent stage during the Anthropocene. A submersible infra-red detector to directly measure in-lake dissolved CO2 concentrations, applied satisfactorily during this study, is an adapted instrument to do so.
