Completed in November 2013, my PhD thesis explored magma chamber interactions and lava dome growth in subduction zone volcanoes. I had the privilege of working under the supervision of Professor Andrew Woods, head of the BP Institute at the University of Cambridge. The full pdf is available here. We also did some work on steady states in exchange flows across geological faults, published in Journal of Fluid Mechanics.
In this thesis, we analyse the long-term evolution of historical volcanic eruptions and identify different patterns of behaviour at the volcanoes. In some cases the volumetric flux, or eruption rate, decays exponentially over years. In other cases, the eruption involves periods of ground inflation and deflation. In still other cases, the eruption rate first wanes at one rate and then changes to a different rate.
Historically, long-term eruptive trends have been interpreted in terms of a closed or open magma plumbing system. A closed system leads to simple exponential decay as magma leaves a storage reservoir or chamber. An open system, in which a storage reservoir is recharged with magma, allows for more complexity.
In this thesis we develop a series of models that allow for the possibility of more than one magma chamber. We build a generalised picture to allow for multiple chambers at different depths in the earth’s crust. We illustrate how combining multiple chambers with a critical chamber overpressure at which an eruption starts and stops can lead to rich dynamics in which the timescale of eruption can be initially controlled by a shallow reservoir and later by a deeper reservoir. We use our model to interpret historical eruption data.
Additionally, we develop laboratory experiments to model the effects of recharge to a chamber. These illustrate how an eruption may converge to steady state following a period of relatively intense or mild eruption activity, as controlled by resistance in the conduit and the critical pressure at which eruptions are initiated.
We consider the implications of our models for monitoring the longterm evolution of volcanic events.