Australia: The Land Where Time Began

A biography of the Australian continent 

Volcanic Drumbeat Seismicity – Stick-Slip Motion and Magmatic Friction Melting

Domes of solidifying magma can form at the summit of a volcano during volcanic eruptions, and as the magma ascends it often forms a plug that is bounded by discrete fault zones, and drumbeat seismicity accompanies this process. The repetitive nature of this seismicity has been attributed to motion (Iverson et al., 2006) of the stick-slip type at loci that are fixed between the conduit wall (Costa, Wadge & Melnik, 2012; Neuberg et al., 2006) and the rising magma plug, though the mechanism for this form of periodic motion has remained controversial (Iverson, 2008; Chouet & Matoza, 2013; Michaut et al., 2013; Dmitrieva et al., 2013). In this study the authors¹ used high-velocity rotary-shear experiments on samples of magma dome that were collected from the Soufrière Hills Volcano, Montserrat, and Mount Saint Helens Volcano, USA. In the study they frictionally slid the solid magma samples to generate slip that was analogous to the movement that took place between the magma and the wall of the conduit. They found that a common consequence of such slip is frictional melting. The melt acts a viscous brake, therefore the velocity of slip decreases as the melt is formed, following which the melt solidifies and the pressure builds up allowing the fracture and slip to resume. A feedback mechanism is therefor provided during the stick-slip process that can accentuate the cyclicity of such motion. Their results indicate that the viscosity of the frictional melt can aid in the defining of the interval of occurrence of the stick-slip events. The authors¹ concluded that the magnitude, frequency and duration of the drumbeat seismicity depend in part of the magma composition.

Sources & Further reading

1. Kendrick, J. E., et al. (2014). "Volcanic drumbeat seismicity caused by stick-slip motion and magmatic frictional melting." Nature Geosci 7(6): 438-442.