Constraining the Energetics of Explosive Lava-Water Interactions
Abstract
During volcanic eruptions, water, such as groundwater or melted ice or snow, may interact with magma within the conduit during eruption, generating explosions when the heat of the magma causes the water to rapidly turn to steam and expand, resulting in what we call a "phreatomagmatic" eruption. In 2010, the eruption of Eyjafjallajökull volcano in Iceland produced a plume of fine ash, through the interaction between magma and glacial melt water, which resulted in the closure of substantial airspace, ultimately costing a total of almost 5 billion dollars. Although an important area of study, it is difficult to quantify the effect of eternal water on eruption intensity when the gas inside of magma is also expanding and fragmenting the magma. In an attempt to understand the energetics of magma-water interactions, small-scale laboratory experiments have been performed. Explosion energy is found to depend mostly on kinetic energy, which is proportional to dispersal distance, and fragmentation energy, which is proportional to the mean grain size of the ejecta, and the mass percent of ash-sized grains. It is thought that in order to generate heat transfer rates sufficiently rapid to cause explosive detonation, the source melt must be finely fragmented, producing ash-sized grains. Those grains undergo brittle fragmentation due to rapid cooling and weak shock waves generated by the vaporization of superheated water. We take the novel approach of studying explosive interactions between lava and water to obtain additional explosion energy constraints. We identified and analyzed numerous beds of lava-water explosion ejecta of varying explosion energy, and we analyzed the ash-sized grains of these beds in detail. We verified that the mass of ash-sized grains increases with increasing explosion energy, and can form at the interface between lava and water. We found that brittle fragmentation occurs to a greater degree as grain size decreases and that the ash of highly-energetic explosions undergoes the most brittle fragmentation. Therefore, our next steps will be to use these results to constrain the fragmentation and kinetic energy, in order to calculate the total energy and heat-transfer rate of lava-water explosions as important analogs for phreatomagmatic eruptions.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2017
- Bibcode:
- 2017AGUFM.U13B..15F
- Keywords:
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- 0810 Post-secondary education;
- EDUCATION