About this Research Topic
Volcanoes are complex multi-component systems where physical and chemical processes operate in ranges that cover multiple phases and several orders of magnitude in space, time, pressure and temperature. This complicates the ability of volcanologists to forecast, either in the short- or longterm, the onset, location, duration and magnitude of hazardous volcanic phenomena including ballistics, lava flows, tephra fallout, debris avalanches, pyroclastic density currents (PDCs) and lahars. Lahars and PDCs rank amongst the most dangerous and damaging phenomena, especially for population and infrastructure located within tens of kilometres around volcanoes. About 50% of the victims at volcanoes in the last 400 yr have been caused by these hazardous flows. Therefore, improving volcanic hazard assessment of PDCs and lahars should be an outstanding priority in volcanology.
Several characteristics make PDCs and lahars remarkably dangerous while also very challenging to describe and model, in order to quantify their hazard:
1. The triggering mechanisms and source conditions can be extremely varied, e.g. dome collapse/explosion, partial/total column collapse, lateral blast for PDCs; and rainfall erosion and shallow landsliding, ice-cap melting, lake outbreak for lahars;
2. The propagation of these flows occurs over complex topography, which may change significantly due to erosion and deposition, even during the transport of a single flow;
3. The flow structure is highly heterogeneous (e.g. clast diameters from micrometers to decameters, and solid volume concentrations from below 1% to over 50%), and varies in space and time.
All these features influence flow rheology and transport mechanisms and, therefore, strongly control the maximum runout of the flows, inundated areas and spatial distribution of impact. Addressing these challenges requires multi-disciplinary efforts to integrate data and expertise from geology, physical volcanology, computational fluid dynamics, terrain analysis, uncertainty quantification, etc.
We aim to bring together scientists from varied scientific domains, backgrounds and national volcanic contexts, to help us explore, as a community, the different approaches that are currently being used worldwide to assess the hazard posed by PDCs and lahars, including associated uncertainties. These may cover:
(i) mapping of PDC and lahar deposits,
(ii) analogue experiments of the physical processes,
(iii) numerical modeling of the physical processes on natural or hypothesized terrains, and/or
(iv) statistical modeling with uncertainty quantification.
A key element in moving towards improved volcanic hazard assessments of PDCs and lahars is better understanding and reporting of advantages, challenges and limitations of different methodologies in a holistic and transparent view. Different methods may be favorable in disparate situations, depending on: (a) the state of volcanic activity (e.g. long repose period vs open-conduit volcanism); and (b) the specific characteristics of the country or region of interest (e.g. general style of volcanism, average distance between volcanic centers, proximity to masses of ice or water, etc).
The reciprocal learning experience on methodological approaches and geographical contexts published in this Research Topic will be extremely beneficial for the volcanological community. Strengthening the interconnection and capabilities of this community with a hazard-oriented perspective could significantly improve hazard assessment of PDCs and lahars worldwide, with the ultimate goal of providing robust and defensible scientific evidence to help save the greatest possible number of lives around volcanoes.
This Research Topic welcomes all article types, with a particular emphasis on Original Research, (Mini) Reviews and Perspectives.
Cover image from British Geological Survey©NERC (top) and Robin Holcomb, U.S. Geological Survey (bottom).
Keywords: volcanic hazard assessment, uncertainty quantification, multidisciplinary research, pyroclastic density currents, lahars
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