Abstract
The objective of our study is to establish an assessment of four volcanic hazards in a country threatened by the eruption of the OlDoinyo Lengai volcano. The last major eruption dates back to 2007-2008 but stronger activity in 2019 has revived the memory of volcanic threats to the Maasai and Bantu communities and human activities (agro-pastoral and tourism). The methods chosen have had to be adapted to the scarce and incomplete data. The volcanic hazards and their probability of occurrence were analysed on the basis of data available in the scientific literature and were supplemented by two field missions combining geography and hydro-geomorphology. Our study enabled us to map the hazards of ash fall, lava flows, lahars and avalanches of debris. Each hazard was spatialised by being ascribed an intensity. They are sometimes synchronous with the eruption sometimes they occur several months or years after a volcanic eruption. The results are the first step towards developing a volcanic risk management strategy, especially for the pastoral communities living around Lengai and for the growing tourist activities in this area.
Highlights
Volcanoes are complex geological systems that can produce a wide variety of dangerous phenomena during and after eruptions
Our study enabled us to map the hazards of ash fall, lava flows, lahars and avalanches of debris
NGOs provided food aid to almost 36,000 people (Msami, 2007). Faced with these poorly documented and insufficiently mapped volcanic threats, we present our progress in assessing the impacts of four volcanic hazards: ash fallout, lava flows, lahars and debris avalanches
Summary
Volcanoes are complex geological systems that can produce a wide variety of dangerous phenomena during and after eruptions These include glowing clouds, lava flows, pyroclastic flows, debris avalanches, ballistic 70 projections, plumes and ashfalls, as well as volcanic earthquakes, landslides, gas emissions, floods, and fires (Baxter and Horwell, 2015). According to the available data, there are many methods for assessing and mapping volcanic hazards (Thouret et al, 2000; Leone and Lesales, 2009; Connor et al, 2015), such as the probabilistic method with the development of event trees (Newhall and Hoblit, 2002), and the use of digital models (Felpeto et al, 2007; Favalli et al, 2011; Tarakada, 2017) These methods require reliable data, acquired through the work of geologists, geomorphologists, volcanologists and geographers. For poorly documented volcanoes, probabilistic scenarios are based on field investigations and, if possible, on modelling (Neri et al, 2013)
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