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Fragmentation by high energy impacts during volcanic activity

^^ Jackie E. Kendrick^^ , Anthony Lamur, Klara Heinrigs, Yan Lavallée

  • Affiliations: Department of Earth and Environmental Sciences, Ludwig-Maximilians-Universität München, Munich, Germany

  • Presentation type: Talk

  • Presentation time: Tuesday 11:00 - 11:15, Room R290

  • Programme No: 3.16.6

  • Theme 3 > Session 16

Abstract

Volcanic eruptions are amongst the most dynamic and energetic processes on Earth, and yet our understanding of the behaviour of materials under relevant conditions remains relatively limited. Recent technological advancements allow us to experiment at faster, hotter and more extreme conditions with higher precision than ever before, enabling exploration of the failure of rocks across a wide range of loading conditions. In particular, a newly developed high-temperature, high-energy drop tower enables mechanical testing at strain rates up to ~103 s-1 with impact energies of up to 1,800 J. Here we explore the energy absorption and rupture strength of variably porous volcanic rocks under a range of impact velocities and masses. We find that the peak energy absorbed by a sample at failure decreases with porosity and increases with impact energy. We also show that the maximum energy that can be absorbed by volcanic rocks without suffering irreversible damage depends upon porosity. The peak stress is higher at higher impact energy, and higher than uniaxial compressive strength, due to the rate strengthening nature of rocks. Upon failure a higher proportion of finer grains are produced at higher energy, and more fines are produced upon fragmentation of the stronger, lower porosity samples. The outcomes from material testing using this novel apparatus can provide a quantitative link between the extremely high strain rate rupture dynamics of volcanic materials to the energy budget of volcanic eruptions which to date remains elusive.