Volcanotectonics

I have worked for many years on various aspects of volcanotectonics – a scientific field that combines various principles from structural geology, volcano-deformation studies, and physics with a view of understanding what processes happen inside volcanoes during unrest periods and how those processes may or may not result in volcanic eruptions. Topics that I have deal with include (a) dyke emplacement, (b) collapse-caldera formation, (c) landslides in volcanoes, (d) magma-chamber formation and development and (e) toughness and failure of volcanic edifices..

Among the main topics my students and colleagues and I am working on at the moment, I mention the following:

(1) Mechanics of large volcanic eruptions.  It is well known from (poro)elastic models that the volume of magma that flows out of a magma chamber during its rupture Vf is normally a very small fraction of the total volume of magma in the chamber, Vt, at the time of rupture. The poroelastic models assume that the magma chamber ruptures and ejects magma (though a dyke or a sheet) once the excess pressure (magmatic pressure in excess of the minimum principal compressive stress in the host rock) in the chamber reaches the in situ tensile strength of the host rock. These models have been used for more than 20 years to account for the volume of magma (intrusive and extrusive) flowing out of a chamber during eruption and/or dyke injection. While useful, these models do not explain how similar-sized magma chambers with similar types of magma, or the same magma chamber, can erupt widely different magma volumes. In particular, they do not explain the mechanical conditions for comparatively large eruptions in a particular volcano. The main aim of the project is to explore the conditions for comparatively large eruptions, both mafic and felsic, with a focus on large mafic eruptions.

(2) Sill emplacement and magma-chamber formation. This is related to a larger project, supported by oil companies, on sill emplacement and their effects on petroleum systems in sedimentary basins. The deflection of dykes into sills depends on the mechanical layering in the crust, its state of stress, the magmatic overpressure, and related factors (see Gudmundsson, 2011, cited).  Whether a sill or a cluster of sills evolves into a shallow magma chamber depends on additional factors such as the thickness of the initial sill (sills), the rate of cooling, the frequency of propagating dykes being arrested (and part of their magma absorbed) by the sill(s) which, in turn, depends on extension (spreading) rates. This project involves analytical and numerical modelling as well as detailed field studies of sills and their feeder dykes.

Selected publications on this topic

Gudmundsson, A., 1990.
Emplacement of dikes, sills and crustal magma chambers at divergent plate boundaries.
Tectonophysics 176, 257-275.

Gudmundsson, A., 1998.
Magma chambers modeled as cavities explain the formation of rift-zone central volcanoes and their eruption and intrusion statistics.
J. Geophys. Res. 103, 7401-7412.

Gudmundsson, A., 2000.
Dynamics of volcanic systems in Iceland: Example of tectonism and volcanism at juxtaposed hotspot and mid-ocean ridge systems.
Ann. Rev. Earth Planet. Science 28, 107-140.

Gudmundsson, A., 2002.
Emplacement and arrest of sheets and dykes in central volcanoes.
J. Volcanol. Geotherm. Res. 116, 279-298.

Gudmundsson, A., 2003.
Surface stresses associated with arrested dykes in rift zones.
Bull. Volcanol. 65, 606-619.

Gudmundsson, A., 2006.                                                                                                 How local stresses control magma-chamber ruptures, dyke injections, and eruptions in composite volcanoes.                                                                                                      Earth-Sci. Reviews 79, 1-31.

Gudmundsson, A., 2007.                                                                                       Conceptual and numerical models of ring-fault formation.                                                 Volcanol. Geotherm. Res., 164, 142-160.

Andrew, R.E.B., Gudmundsson, A., 2007.                                                           Distribution, structure, and formation of Holocene lava shields in Iceland.                           J. Volcanol. Geotherm. Res., 168, 137-154.

Gudmundsson, A., 2009.                                                                                            Material toughness and failure of volcanic edifices.                                              Tectonophysics, 471, 27-35.

Gudmundsson, A., 2011.                                                                                         Deflection of dykes into sills at discontinuities and  magma-chamber formation. Tectonophysics  doi:10.1016/j.tecto.2009.10.015

Gudmundsson, A. 2012.                                                                                               Magma chambers: formation, local stresses, excess pressures, and compartments.          Invited review for J. Volcanol. Geotherm. Res. (in revision).