Cristian MONTANARO
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Explosivity of gas-overpressure and vapour-explosion driven fragmentation in volcanic systems
Personal Project in NEMOH
Phreatic eruptions are amongst the most common eruption types, often precursory to a new cycle of volcanic activity, and occur with little or no warning representing a significant hazard within geothermal regions. However their dynamics are still poorly understood, partly owned to their huge variety of triggers and appearance. The main goal of the PhD project is to better our understanding and to constrain the physical processes of phreatic eruption activity, and to compare their dynamics to magmatic eruptions. In particular the fragmentation behavior in relation with the competence of natural rocks (unaltered to altered state), as well as their rock mechanical properties with respect to a present water phase, will be investigated.
The fragmentation experiments simulating the phreatic eruptions are performed within a shock-tube apparatus (Alidibirov and Dingwell, 1996, Spieler et al. 2004, Scheu et al. 2008) consisting of a high pressure autoclave overlain by a voluminous tank at atmospheric conditions.
Pressurization and subsequent depressurization of the autoclave are regulated by a diaphragm system opening at a defined differential pressure. Cylindrical samples drilled from volcanic rocks are mounted in the autoclave and fragmented by rapid decompression of the system.
The fragmentation threshold of dry and liquid water saturated samples are meant to be analyzed. Pressure sensors are used to record the speed of fragmentation. Due to a full recovery of the fragments the grain-size distribution, and therefore the efficiency of fragmentation, can be determined. A high-speed camera (10000 fps) is also used to measure the ejection velocities of the gas–particle mixture.
The results will used to develop a model for the energy conversion based on the thermodynamics of vapor expansion in order to constrain phreatic eruptions scenarios and elucidating their hazard potential.
Scientific Background
I am graduate in Geophysical and Structural Geology (2008), at the University of Rome "La Sapienza" with a thesis focused on the stratigraphic reconstruction of pyroclastic products from hydromagmatic eruptions; the work also included the study of the spatial and temporal evolution of the hydromagmatic centers through morphological analysis, and the energetic parameterization of hydromagmatic events via quantitative analyses of ejected ballistic.
After my graduation I started collaborations with the INGV of Rome working on the analysis of high-speed imaging. This innovative technique was used to get insight on two important major topics: the conduit dynamic processes of strombolian activity and the settling dynamic of ash aggregates.
I also got experience as marine geophysicist working with the Marine Geology research group of “La Sapienza”; by being involved within the MAGIC (MArine Geohazards Along the Italian Coasts) project I developed knowledge on interpretation and analyses of geophysical data used to identify potential geohazard for human settlements and infrastructures in the offshore and coastal zones.
In between these experiences I spent six month in Alaska where I carried out a research project on volcanic island edifice instability; the aim of the project was to improve the knowledge concerning volcanic collapses occurred along the Aleutian Ridge, in western part of Aleutian island arc.
About me
Personal Contacts
Department of Earth and Environmental Sciences
Section for Mineralogy, Petrology and Geochemistry
Theresienstr. 41
80333 Munich
Germany
Email: cristian.montanaro
min.uni-muenchen.de
