TY - JOUR
T1 - Catastrophic caldera-forming eruptions
T2 - Thermomechanics and implications for eruption triggering and maximum caldera dimensions on Earth
AU - Gregg, P. M.
AU - De Silva, S. L.
AU - Grosfils, E. B.
AU - Parmigiani, J. P.
N1 - Funding Information:
We thank the APVC Research Group and the Volcano Igneous Petrology Economic Research (VIPER) Group at OSU for insightful discussions that contributed to this work. We thank G. Currenti for aid in double-checking the viscoelastic analytical and numerical solutions. We also thank R. Scandone and an anonymous reviewer for helpful comments, which added to the final manuscript. This research was funded by a National Science Foundation Postdoctoral Fellowship (Gregg, EAR 0815101 ). Work on supereruptions in the Central Andes is funded by the National Science Foundation (de Silva, EAR 0908324). Initial formulation and analysis of the elastic caldera mechanics problem commenced during research funded by a Fulbright New Zealand Award (Grosfils).
PY - 2012/10/1
Y1 - 2012/10/1
N2 - 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>10 3km 3, and roof aspect ratios (depth/width)<0.3, moderate magma chamber overpressures (<30MPa) will cause extensive through-going fault development in the overlying roof. This result indicates an external mechanism, caused by fault propagation in the roof, is a likely trigger for the largest caldera forming eruptions. The thermomechanical models also provide an estimate of the maximum size of magma chamber growth in a pristine host material and, thus, an estimate of the maximum size of the resultant caldera. We find a maximum reservoir volume range of 10 4-10 5km 3 for shallow crustal magma chambers emplaced at depths to the top of the magma chamber of 3-7km. These volumes produce maximum caldera areas of 10 3-10 4km 2, comparable to the largest calderas observed on Earth (e.g., Toba). These thermomechanical models offer critical new insight into the mechanics of catastrophic caldera collapse and provide a numerical construct for predicting how eruption is triggered in the largest crustal magma chambers.
AB - 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>10 3km 3, and roof aspect ratios (depth/width)<0.3, moderate magma chamber overpressures (<30MPa) will cause extensive through-going fault development in the overlying roof. This result indicates an external mechanism, caused by fault propagation in the roof, is a likely trigger for the largest caldera forming eruptions. The thermomechanical models also provide an estimate of the maximum size of magma chamber growth in a pristine host material and, thus, an estimate of the maximum size of the resultant caldera. We find a maximum reservoir volume range of 10 4-10 5km 3 for shallow crustal magma chambers emplaced at depths to the top of the magma chamber of 3-7km. These volumes produce maximum caldera areas of 10 3-10 4km 2, comparable to the largest calderas observed on Earth (e.g., Toba). These thermomechanical models offer critical new insight into the mechanics of catastrophic caldera collapse and provide a numerical construct for predicting how eruption is triggered in the largest crustal magma chambers.
KW - Caldera collapse
KW - Finite-element model
KW - Geodynamic model
KW - Magma chamber rupture
KW - Mohr-Coulomb failure
KW - Resurgence
KW - Surface displacement
KW - Thermomechanics
KW - Tumescence
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U2 - 10.1016/j.jvolgeores.2012.06.009
DO - 10.1016/j.jvolgeores.2012.06.009
M3 - Article
AN - SCOPUS:84863474272
SN - 0377-0273
VL - 241-242
SP - 1
EP - 12
JO - Journal of Volcanology and Geothermal Research
JF - Journal of Volcanology and Geothermal Research
ER -