EC Programme ENV4-CT98-0703-SCV1 "Physics of explosive volcanism", contractor Universitaet Wuerzburg:
Dry and wet phreatomagmatic explosions: a comparison between pyroclastic deposits of La Fossa di Vulcano (Italy) and MFCI experiments.
Projektleitung an der Universität Würzburg:
Beteiligte Wissenschaftlerinnen und Wissenschaftler:
Experimental methods for the production of ash-sized particles by specific fragmentation processes using close-to-nature silicate melts have been developed and refined to fit the needs of the project: Thermal granulation, gas driven ?magmatic? fragmentation and thermohydraulic explosion by water-melt interaction.The experimental set-up TEE-II has been modified to fit this needs.
An additional unit was constructed, by which ?wet? exit conditions of the exploding system were achieved. This unit consists of a cylindrical container (to be mounted onto the melt crucible) and a device for the controlled flooding of this container with a volume of maximum 1000 ml of water. This water is introduced immediately before the triggering of the explosive expansion of the underlying melt in such way, that the expanding hot melt-gas-vapour-system is forced to pass through a superimposed water layer of up to 10 cm thickness. Using this technique, the experimental generation of ash particles was achieved, that typically can be found in wet surge deposits of La Fossa di Vulcano.
Rheology and thermal behavior of La Fossa magma simulant (remelted scoria from La Sommata) was determined in the Wuerzburg Lab.
A discrimination scheme (using SEM pictures) was developed from interlaboratory standardization of particle analysis. After checking the descriptive and discriminating power of various form and shape parameters, in cluding adimensional perimeter and area factors, fractal and multifractal dimension; a binary diagram based on adimensional shape parameters was chosen as both the best suited for discriminating particles in term of different fragmentation modes and the easier to construct and interpret. This method was successfully applied to quantify natural ash particles in respect to their fragmentation and transport history.
Energy calculations were conducted on the base of specific fragmentation energy related to particle families produced in laboratory experiments and sampled from natural deposits.
Laufzeit: von 08.1998 bis 08.2000
EU ,Genehmigungsdatum: 01.06.1998