000K utf8 1100 $c2004 1500 eng 2050 urn:nbn:de:gbv:8-diss-12275 3000 Urbanski, Nico-Alexander 4000 Eruption dynamics during Plinian eruptions : insights from the stratigraphic variations of deposit structures and pumice textures of the Minoan eruption (Santorini, Greece) and the Laacher See eruption (East Eifel, Germany)$hChristian-Albrechts-Universität zu Kiel [Urbanski, Nico-Alexander] 4030 Kiel$nChristian-Albrechts-Universität zu Kiel 4209 The in situ observation of conduit processes as well as eruption dynamics during major Plinian eruptions is still impossible, however, understanding these processes is essential to enhance hazard mitigation and risk reduction near active volcanoes. Here we set out to reconstruct the conditions in the conduit during Plinian eruptions through a detailed analysis of the fall deposits of two major Plinian eruptions (Minoan eruption as the chemically homogeneous and the Plinian phases of the Laacher See eruption as chemically heterogeneous endmember) focussing on the stratigraphic variation of deposit structures (granulometry, modal composition, clast shape parameters) and pumice textures (clast density, permeability, vesicle size distribution) in combination with chemical data and intensive parameters. Changes in the aforementioned parameters reflect changing transport conditions like the granulometric data of the fall deposit being an indicator for fragmentation and eruption intensity or the acceleration of the melt being controlled by degassing that is mirrored in the pumice density and vesicle size distribution. The data collected by means of various methods and their simultaneous interpretation demonstrates that deposit structure and pumice texture are indeed a powerful tool to constrain and reconstruct the temporal variation of conduit flow and eruption dynamics during major Plinian eruptions. It was found that the chemically homogeneous deposits are much easier to invert for conduit flow processes and eruptions dynamics because viscosity is a major factor controlling transport properties of the melt. With the viscosity being fixed parameters like conduit geometry, or shifting of the fragmentation horizon can be constrained much better. 4950 https://nbn-resolving.org/urn:nbn:de:gbv:8-diss-12275$xR$3Volltext$534 4961 https://macau.uni-kiel.de/receive/diss_mods_00001227 5051 550 5550 Deposit Structures 5550 Entgasung 5550 Ergussgestein 5550 Eruption 5550 Eruption Dynamics 5550 Laacher See 5550 Laacher See Volcano 5550 Magma 5550 Minoan Eruption 5550 Plinian Eruptions 5550 Pumice Textures 5550 Risikoanalyse 5550 Santorin 5550 Verlauf