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Should I Flow or Should I Blow? That's Important to Know!

Simon Thivet1, Lucia Dominguez1, Jonathan Lemus 1,2, Allan Fries1, Clothilde Jost1, Carolina Díaz-Vecino1, Riccardo Simionato1,2, María-Paz Reyes-Hardy1, Mélanie Gretz1

  • Affiliations: 1Department of Earth Sciences, University of Geneva, Geneva, Switzerland; 2Department of Computer Science, University of Geneva, Geneva, Switzerland 

  • Presentation type: Demonstration

  • Demonstration time: Check the SciCom program, Room Esplanade

  • Programme No: 7.4.17

  • Theme 7 > Session 4

Abstract

Volcanic eruptions can manifest in markedly different styles, ranging from effusive outpourings of lava to highly explosive events that produce ash clouds and pyroclastic materials. This contrast arises primarily from the interplay between magma viscosity and magmatic gas supply. Understanding such processes is crucial, not only for volcanologists but also for communities living near active volcanoes who rely on effective preparedness strategies. Science communication and demonstrations play a fundamental role in this process. To engage broad audiences, we propose two hands-on demonstrations showcasing the fundamental physical principles governing effusive versus explosive eruptions. These demonstrations are regularly performed by the Enviroscope program of the University of Geneva. First, a "lava flow" experiment uses materials of varying viscosities poured down a slope to illustrate how viscosity affects flow velocity and morphology---a key factor driving effusive eruptions. Second, a "Cola and Mentos" experiment models the role of dissolved gases in explosive eruptions by demonstrating how rapid gas expansion propels volcanic fragments into the atmosphere. These accessible, visually striking demonstrations are powerful tools to communicate complex volcanic concepts, bridging the gap between scientific research and the public. By highlighting the critical influence of magma rheology and gas content, our approach aims to foster a deeper appreciation of volcanic hazards and stimulate greater community engagement in hazard mitigation and preparedness. Language of activity: French (English if needed). Materials: metallic slope; various viscosity liquids (i.e., teeth paste, hair gel, soap, ketchup); Coke and Mentos; Rock samples; one table.