Catastrophic caldera-forming eruptions: Thermomechanics and implications for eruption triggering and maximum caldera dimensions on Earth

• Published in: Journal of volcanology and geothermal research 2012-10, Vol.241-242, p.1-12
• Main Authors: Gregg, P.M., de Silva, S.L., Grosfils, E.B., Parmigiani, J.P.
• Format: Article
• Language: English
• Subjects: Caldera collapse; Calderas; Chambers; Ductile brittle transition; Earth; Finite-element model; Geodynamic model; Magma; Magma chamber rupture; Mathematical models; Mohr–Coulomb failure; Overpressure; Resurgence; Roofs; Surface displacement; Thermomechanics; Tumescence
• ISSN: 0377-0273; 1872-6097
• DOI: 10.1016/j.jvolgeores.2012.06.009

Approximately every 100,000years the Earth experiences catastrophic caldera-forming “supereruptions” that are considered to be one of the most hazardous natural events on Earth. Utilizing new temperature-dependent, viscoelastic numerical models that incorporate a Mohr-Coulomb failure criterion, we find that eruptive failure of the largest magma chambers is a function of the geometry of the overlying roof and the location of the brittle-ductile transition. In particular, the ductile halo created around the hot magma chamber buffers increasing overpressures and prevents pressure relief via magmatic injection from the magma chamber. The numerical results indicate that as chamber volume increases, the higher temperatures in the host rock and the decrease in the roof aspect ratio cause a shift from reservoir-triggered eruption to an external roof-triggered mechanism. Specifically, as overpressure increases within the largest magma chambers, extensive uplift in the overlying roof promotes the development of through-going faults that may trigger eruption and caldera collapse from above. We find that for magma chamber volumes>103km3, and roof aspect ratios (depth/width)