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Hail formation triggers rapid ash aggregation in volcanic plumes
Alexa R Van Eaton1,2, Larry G Mastin1, Michael Herzog3
1David A. Johnston Cascades Volcano Observatory, US Geological Survey, Vancouver, Washington 98683, USA.
Nature Communications
|August 4, 2015
Summary
Volcanic eruptions with water cause ash particles to clump together, like hail. This process rapidly removes ash from the atmosphere, improving eruption forecasts and geological interpretations.
Area of Science:
- Volcanology
- Atmospheric Science
- Geology
Background:
- Particle aggregation during explosive volcanic eruptions is poorly understood.
- This process impacts ash dispersal forecasting and interpreting past eruptions.
- Wet eruptions, incorporating external water, are common globally.
Purpose of the Study:
- To investigate the mechanisms and timescales of ash particle aggregation.
- To analyze aggregation during a well-characterized 'wet' eruption.
- To understand the role of water in ash fallout.
Main Methods:
- Utilized C-band weather radar data.
- Analyzed volcanic fall deposits.
- Employed numerical modeling.
Main Results:
- Hail-forming processes in the eruption plume aggregated ~95% of fine ash.
- Most erupted mass was removed from the atmosphere within 30 minutes.
- Identified a hail-like ash aggregation mechanism.
Conclusions:
- Hail-like ash aggregation explains rapid fine ash fallout.
- This mechanism contributes to concentrically layered volcanic deposits.
- Understanding this process enhances ash dispersal forecasting and geological record interpretation.
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