Probing magma plumbing systems beneath volcanic calderas in the Galapagos Islandsa.email@example.com
Volcanic calderas are surface depressions that form by collapse of overburden into a subterranean magma reservoir during volcanic eruptions. They exist on the scale of kilometres to tens of kilometres and are associated with the largest eruptions ever to have occurred on Earth. Collapses are rare, with only seven cases ever having been documented. However, we can learn much about the current state of magma chambers beneath calderas systems by measuring deformation at the surface; pressure changes within magmatic systems lead to displacements of the surface, which can be measurable using techniques such as GPS and radar interferometry (InSAR) (Pinel et al, 2014).
Figure 1: Map of the western islands of the Galapagos Archipelago. Six volcanoes on Isabela and Fernandina islands have been actively deforming during the last decade, and three of them erupted. For each volcano, dates of the latest eruptions are reported. (Bagnardi and Amelung, 2012)
In the Galapagos Islands there are six volcanoes with calderas that have actively deformed in the last two decades. Fernandina volcano was the site of one of the largest caldera collapses in recent history (1968), with 350 m of subsidence of the caldera floor in a few days. This event, however, remains enigmatic because no large eruption was associated with the collapse.
Various studies have concluded the existence of shallow magma reservoirs a few kilometres beneath Fernandina and other Galapagos volcanoes with similar geometries to the calderas themselves (e.g. Bagnardi and Amelung, 2012). On the other hand, the most recent caldera collapse episode to have been observed, the 2014-2015 eruption/collapse at Bardarbunga volcano in Iceland, was associated with withdrawal of magma from much deeper, at around 12 km depth (Gudmundsson et al, 2016). However, deformation measurements in and around the caldera at Bardarbunga could equally well be explained by withdrawal of magma from a shallow chamber at only a few kilometres depth; caldera ring faults effectively transfer the source of deformation upwards. This raises the question of whether other caldera systems, such as those in the Galapagos, may not be as shallow as previously thought.
In this project you will test the hypothesis that magma reservoirs in the Galapagos may be deeper than currently thought using a combination of deformation measurements and gravity measurements. Inflow of magma at deeper depths will have a smaller gravity signal than the magma inflow required at shallow depths to give the same deformation signal, allowing us to distinguish between the two. Based on this new understanding, you will then go on to develop and test models for the caldera collapse that occurred at Fernadina last century.
Figure 2: Schematic cross-section across Fernandina Islands and the underlying oceanic crust showing the inferred structure of the shallow magmatic system (Bagnardi and Amelung, 2012)
You will work with leading scientists at Leeds and Ecuador to:
- Measure deformation at Fernandina Volcano using radar interferometry (InSAR) and a repeated GNSS field campaign.
- Measure gravity changes Fernandina Volcano in the Galapagos by means of a repeated gravity field campaign.
- Model the magma plumbing systems constrained by both deformation and gravity data and test the hypothesis of deeper magma chambers than implied by deformation data alone.
- Develop and test models for the caldera collapse event at Fernadina in 1968.
Potential for high impact outcome
Caldera collapses are associated with the largest of all volcanic eruptions, but are poorly understood due to the fact that they are rare. Constraints on the present-day plumbing systems beneath volcanoes with caldera systems, will contribute to our understanding of the causes of collapse and we expect at least one high impact publication from this research.
You will work under the supervision of Prof. Andy Hooper and Dr. Marco Bagnardi within the Institute of Geophysics and Tectonics in the School of Earth and Environmental Sciences. You will also become a member of the Centre for Observation and Modelling of Earthquakes, Volcanoes and Tectonics (COMET), which brings together experts from the Universities of Oxford, Cambridge, Leeds, Bristol, Reading, Liverpool and Newcastle and University College London (http://comet.nerc.ac.uk). Through COMET, you will have access to a range of training opportunities related to deformation monitoring and modelling, in addition to a broad spectrum of training workshops provided by the Faculty, from training in numerical modelling through to managing your degree and preparing for your viva (http://www.emeskillstraining.leeds.ac.uk/). You will also be actively encouraged to present work at conferences and to publish papers.
The student should have a strong interest in earth sciences and a strong background in a quantitative science (e.g. earth sciences, maths, physics, engineering). Enthusiasm to carry out fieldwork in tough volcanic environments is also essential.
Bagnardi, M., and F. Amelung (2012), Space-geodetic evidence for multiple magma reservoirs and subvolcanic lateral intrusions at Fernandina Volcano, Galápagos Islands, J. Geophys. Res., 117(B10), B10406.
Gudmundsson MT; Jónsdóttir K; Hooper A; et al (2016) Gradual caldera collapse at Bárdarbunga volcano, Iceland, regulated by lateral magma outflow, Science, 353.
Pinel V; Poland MP; Hooper A (2014) Volcanology: Lessons learned from Synthetic Aperture Radar imagery, Journal of Volcanology and Geothermal Research, 289, pp.81-113.
Related undergraduate subjects:
- Earth science