SHALLOW CHAMBER & CONDUIT BEHAVIOR OF SILICIC MAGMA: A THERMO- AND FLUID- DYNAMIC PARAMETERIZATION MODEL OF PHYSICAL DEFORMATION AS CONSTRAINED BY GEODETIC OBSERVATIONS: CASE STUDY; SOUFRIERE HILLS VOLCANO, MONTSERRAT

The Soufrière Hills Volcano, Montserrat (SHV) is an active, mainly andesitic and well-studied stratovolcano situated at the northern end of the Lesser Antilles Arc subduction zone in the Caribbean Sea. The goal of our research is to create a high resolution 3D subsurface model of the shallow and deeper aspects of the magma storage and plumbing system at SHV.

Our model will integrate inversions using continuous and campaign geodetic observations from 1995 to the present as well as seismic records taken at various unrest intervals to construct a best-fit geometry, pressure point source and inflation rate and magnitude. We will also incorporate a heterogeneous media in the crust and use the most contemporary understanding of deep crustal- or even mantle-depth “hot-zone” genesis and chemical evolution of silicic and intermediate magmas to inform the character of the deep edifice influx.

The final forward model should elucidate observational data preceding and proceeding unrest events, the behavioral suite of magma transport in the subsurface environment and the feedback mechanisms that may contribute to eruption triggering.

Preliminary hypotheses suggest wet, low-viscosity residual melts derived from “hot zones” will ascend rapidly to shallower stall-points and that their products (eventually erupted lavas as well as stalled plutonic masses) will experience and display two discrete periods of shallow evolution; a rapid depressurization crystallization event followed by a slower conduction-controlled heat transfer and cooling crystallization. These events have particular implications for shallow magma behaviors, notably inflation, compressibility and pressure values.

Visualization of the model with its inversion constraints will be affected with ComSol. Conclusions about the subsurface behavioral suite at SHV will have high applicability to other silicic and intermediate volcanic edifices and may aid in the hazard mitigation associated with volcanic unrest.