Heat discharge at the dynamic magma-water-interface in subaqueous and subglacial volcanism: Experiments and thermodynamic modelling

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During subaqueous/subglacial eruptions, thermal pulses have been observed. These eruptions provide quantitative information on time scales and thermal efficacy. A short-term calorimeter was built for the direct measurement of the heat-flux from a magmatic melt to a coolant. In the first series material from recent eruptions in Iceland and purified water were used and particles could be pro-duced in a non-explosive process, that are practical identical to those from natural hyaloclastites. By variations of melt properties and experimental geometry flat water and deep sea signatures could be produced as well. First approximations of the thermo-mechanical energy budget of the experimental products are in good agreement with data of the 2004 Grimsvötn eruption. The development of a thermodynamic model is in progress. First experiments with impure coolants show, that heat capacity and viscosity of the coolant have a major impact on the heat discharge. Detailed studies are planned in the next step. The records of seismic signals show the synchronicity of fragmentation and heat-flux: thermal and seismic micro-pulses can be used for monitoring during the experiments. It is intended to use high resolution pressure sensors to monitor the acoustic emission directly. If “acoustical fingerprints” can be assigned, direct monitoring using appropriate sensors on submersibles or probes may be possible.