CoSV webinar series: Volcanoes can make waves too: Tsunamis generated by pyroclastic density currents

CoSV webinar series: Volcanoes can make waves too: Tsunamis generated by pyroclastic density currents

On November 1st, 2023, 16:00 UTC, CoSV hosted the webinar entitled “Volcanoes can make waves too: Tsunamis generated by pyroclastic density currents”. This webinar was presented by Dr. Natalia Lipiejko , Post-Doctoral Researcher in Volcanology and Granular Flows, Lancaster Environment Centre, Lancaster University, UK.

To watch the webinar recording, click this link.

Seminar Lipiejko 2023 Pptx

Abstract:

Although volcanic eruptions account for only 5% of all the documented tsunamis, they are responsible for almost 25% of all the fatalities associated directly with volcanic eruptions. One of the reasons for such high fatalities is that by transferring energy to the waves, tsunamigenic volcanic eruptions expand the potential hazard area well beyond the eruption itself. Moreover, volcanic tsunamis are rarely included in hazard maps because the source mechanisms, and hence the properties of the resultant waves, are poorly understood. 

Volcanic tsunamis can be generated by source mechanisms that include pressure waves sent through the atmosphere, an entrance of pyroclastic density currents (PDCs) into the sea, a caldera collapse, slope instabilities, volcanic earthquakes, and underwater eruptions. A combination of different volcanic tsunami source mechanisms has often been involved in generating tsunamis, with a prime example being the 2022 eruption of the Hunga Tonga-Hunga Ha’apai volcano, where a variety of different volcanic sources caused destructive tsunamis. Determining the main source mechanism and analysing tsunamis generated by complex sources is incredibly challenging. Therefore, a deeper understanding of the individual source mechanisms is necessary to analyse more complex events. 

This research focuses on tsunami generation by the entrance of PDCs into water. A fluidised granular column was released from a reservoir; the particles flowed down a porous ramp into a water-filled flume and generated waves. The entrance of the fluidised flow into the water generated a solitary-like leading wave followed by a smaller trough and trailing waves. Upon impact, the flow separated into a part advected with the wave crest and a part which turbulently mixed with water and propagated along the bottom of the flume, forming an underwater particulate gravity current. The tsunamigenic potential of the fluidised flows was explored in terms of the flow kinematics before impacting the water, the flow-water interactions and the wave generation and the propagation of the waves and the underwater gravity current in the near field.

Fig Wave Generation And Timestack

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