<p>The process of remobilization of tephra fallout by wind or water has been documented during and after explosive eruptions, with important impacts in health, infrastructure and environment. Existing studies focus on large stratovolcanoes, even though this process may also occur in monogenetic fields. In this work, we address the relevance, controlling factors and characteristics of the processes and deposits related to this phenomenon for scoria cones, which are the main volcano type in this setting. In a systematic literature review, we found a limited number of publications mentioning this process that mostly consist of individual case studies. Based on the analysis of this dataset, we make a synthesis of the existing data and present a first model of tephra remobilization at scoria cones. In this model, we distinguish between (1) the proximal zone, where erosion and transport occur by rilling, gullying and landsliding on the cone slopes, and (2) medial to distal zones where channel erosion, flooding, wind deflation, gullying and ponding along lavas, also take place. The main controlling factors are the climatic conditions that determine the agent and intensity of erosion and transport, and topography which influences transport and deposition. We identify critical gaps in the literature. Sedimentary data on the deposits is sparce and only available for a few cones in specific contexts. Also, the rates of erosion and redeposition are poorly constrained. We demonstrate that closing these gaps is important to better estimate the total volume of tephra emitted by scoria cone eruptions, reconstruct the environmental conditions of past eruptions, and assess hazards in urbanized active monogenetic fields.</p>

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Tephra remobilization in scoria cones

  • Natalia Villalba,
  • Marie-Noëlle Guilbaud

摘要

The process of remobilization of tephra fallout by wind or water has been documented during and after explosive eruptions, with important impacts in health, infrastructure and environment. Existing studies focus on large stratovolcanoes, even though this process may also occur in monogenetic fields. In this work, we address the relevance, controlling factors and characteristics of the processes and deposits related to this phenomenon for scoria cones, which are the main volcano type in this setting. In a systematic literature review, we found a limited number of publications mentioning this process that mostly consist of individual case studies. Based on the analysis of this dataset, we make a synthesis of the existing data and present a first model of tephra remobilization at scoria cones. In this model, we distinguish between (1) the proximal zone, where erosion and transport occur by rilling, gullying and landsliding on the cone slopes, and (2) medial to distal zones where channel erosion, flooding, wind deflation, gullying and ponding along lavas, also take place. The main controlling factors are the climatic conditions that determine the agent and intensity of erosion and transport, and topography which influences transport and deposition. We identify critical gaps in the literature. Sedimentary data on the deposits is sparce and only available for a few cones in specific contexts. Also, the rates of erosion and redeposition are poorly constrained. We demonstrate that closing these gaps is important to better estimate the total volume of tephra emitted by scoria cone eruptions, reconstruct the environmental conditions of past eruptions, and assess hazards in urbanized active monogenetic fields.