Geodetic imaging of magma migration at Soufrière Hills Volcano 1995 to 2008
Published:January 01, 2014
Derek Elsworth, Roozbeh Foroozan, Joshua Taron, Glen S. Mattioli, Barry Voight, 2014. "Geodetic imaging of magma migration at Soufrière Hills Volcano 1995 to 2008", The Eruption of Soufrière Hills Volcano, Montserrat from 2000 to 2010, G. Wadge, R. E. A. Robertson, B. Voight
Download citation file:
We use histories of magma efflux and surface deformation from a continuously operating global positioning system (cGPS) to quantitatively constrain magma transfer within the deep crustal plumbing of the Soufrière Hills Volcano (SHV). Displacement records reach a surface aperture of approximately 11 km and are continuous over three successive cycles of eruption followed by a pause spanning 1995–2008, and we focus on data of this time period. The assumed geometry and flow topology is for twin vertically stacked spherical chambers pierced by a vertical conduit that transmits magma from the deep crust to the surface. For a compressible magma column within an elastic crust we use mean deformation rates measured at between 6 and 13 cGPS stations for periods of effusion then repose and the time-history of magma efflux to define optimal chamber depths and basal magma input. The best fit for a constrained constant basal input to the system is obtained for chambers at 5 and 19 km, and a constant magma input rate of approximately 1.2 m3 s−1. Eruptive then pause episodes are, respectively, characterized by synchronous deflation then inflation of both shallow and deep chambers. Throughout this period of three repeated episodes of effusion then repose, the total effusive volume (c. 0.95 km3 dense rock equivalent, DRE) has been sourced half from the lower chamber (c. 0.5 km3) and half from below this chamber (c. 0.45 km3). A consistent observation, repeated through three episodes, is that the eruption restarts as the shallow chamber regains its original volume following the pause and that eruption rearrests when the shallow chamber has deflated by a small but constant volume change (c. 16–22 Mm3). This magmatic metering is consistent with a control on eruption periodicity that involves overpressured breaching of the shallow chamber followed by underpressured sealing. We contrast these observations with other contemporary models that have consistently placed an upper chamber at a depth of approximately 5–6 km, and deeper chambers at 12 km and deeper.
Figures & Tables
The Eruption of Soufrière Hills Volcano, Montserrat from 2000 to 2010
The 1995 to present eruption of Soufrière Hills Volcano on Montserrat is one of the most important and best-studied eruptions of an explosive andesitic volcano. This volume presents scientific findings from the period between 2000 and 2010; it follows on from Memoir 21, which focused on the early years of activity between 1995 and 1999. In addition to descriptions and analysis of the growth, collapse and explosions associated with lava domes, there are papers on the deformation of the volcano caused by the deep magma, the petrology and geochemistry of the lavas and associated gases. Of particular note are: an overview of the insights into the deep structure of the volcano that resulted from a major international seismic tomography experiment; and an analysis of the quantitative risk assessment process that has run now for most of the eruption, the longest such continuous assessment in the world.