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The ejection and cooling rate of pyroclasts during mafic explosive eruptions

Chiedozie C. Ogbuagu 1,2,3 ,Kuang C. Lin2, Thomas J. Jones4, Silvio De Angelis1

  • Affiliations: 1School of Environmental Sciences, University of Liverpool, Liverpool L69 3GP, UK; 2Department of Engineering and System Science, National Tsing Hua University, Hsinchu 30013, Taiwan; 3Department of Geology, University of Nigeria, Nsukka, 410001, Enugu State, Nigeria; 4Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, UK.

  • Presentation type: Poster

  • Presentation time: Tuesday 16:30 - 18:30, Room Poster Hall

  • Poster Board Number: 87

  • Programme No: 3.16.14

  • Theme 3 > Session 16

Abstract

Explosive volcanic eruptions pose a threat to nearby populations and infrastructure.  Erupted pyroclasts (i.e., variably molten lava droplets) can travel large distances from the eruptive vent to cause a range of hazards. To mitigate these hazards from explosive eruptions there is an increasing need to improve our understanding of the transport dynamics of pyroclasts. In this study, we developed and coupled both a transport and a transient cooling model that account for the instantaneous, in-flight, cooling of pyroclasts of different sizes, launch angles, and exit velocities. The transport model developed solves equations for a translating spherical body in two-dimensional (2-D) space and the cooling model solves the Fourier heat equation for spherical bodies. The two models were then coupled using a set of equations that describe relationships between Nusselt-Reynolds-Prandtl numbers. These relationships provide a way to estimate the heat transfer coefficient, based on ambient flow conditions around the pyroclast, at different times during the particles transport. Together, our model can describe the trajectory, distanced reached, and cooling profiles of pyroclasts during all mafic explosive eruptions. We show how it can be used to predict the temperature of pyroclasts within lava fountains and discuss the possible textural outcomes of ejected pyroclasts in-flight and upon landing. Thus, our model can be used to predict the pyroclast types (e.g., rheomorphic, breadcrusted) at set distances from the vent and used to forensically determine eruptive conditions from deposits of past eruptions. Keywords: transient cooling, transport, explosive eruptions, numerical model, real-time monitoring