Dune bedfroms generated by pyroclastic density currents

• Applicant: Dr. Ulrich Küppers
• Subject Area: Palaeontology
• Term: from 2012 to 2015
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 207474467

One of the fundamental topics in assessment of volcanic hazards is the understanding of pyroclastic density currents (PDCs). During explosive eruptions or upon catastrophic collapse of lava domes, such density currents of fragmented blocks and gas at elevated temperature are produced and travel down the flanks of the volcanic edifice at high velocities (up to 100s km/h). They represent a major threat to the surrounding population. PDCs are very heterogeneous with a wide range of particle concentrations and grain size distributions, leading to different flow behaviour. As direct observation is impossible, our understanding must be based on the study of the deposits. PDCs from the August 2006 eruption at Tungurahua (Ecuador) produced deposits that exhibit dune bedforms (DBs) with well-developed outer shape and internal stratification. Such rarely preserved features offer the unique opportunity to investigate quantitatively the deposition conditions and draw conclusions on flow dynamics. Here, we will combine three different approaches to extract a maximum of information from DBs and enhance our understanding of PDCs. We will 1) describe the DBs at Tungurahua (i.e., spatial distribution, dimensions, internal stratification, and grain size distribution), 2) perform wind-tunnel experiments on gas and ash mixtures to reproduce DBs, and 3) provide a physical framework capable of describing the flow conditions of PDCs generating DBs. The results will improve the hazard assessment of PDCs.

• DFG Programme: Research Grants
• International Connection: Denmark, Ecuador
• Participating Persons: Professor Dr. Donald Bruce Dingwell; Dr. Jonathan Merrison; Patricio Ramon; Professor Dr. Keld Rømer Rasmussen