Translating magma intrusion into volcano surface deformation

Modelling volcano ground deformation driven by magma movement is critical to eruption forecasting, but is limited by assumptions that the host rocks are simple and homogeneous. In this project, we will visit an ancient intrusion in Chile where the uplifted overlying and folded rock is exposed, allowing the area to be geologically mapped using digital techniques and samples collected for rock mechanic and magnetic experiments.

These data will enable us to find where deformation concentrates above intrusions, and establish how it locally changes the behaviour of rocks during folding. We will then explore how to build these complexities into ground deformation models, which will improve the reliability of their use in eruption forecasting.

Objectives and methodology

We can study the forms of intrusions and their associated host rock deformation (e.g. forced folds) where they are exposed at Earth's surface or imaged in geophysical data. To improve the reliability of ground deformation models, this project aims to quantify the distribution and style of deformation within intrusion-induced forced folds, and benchmark how these affect mechanical rock properties.

This data will feed into new ground deformation models that can account for spatial and temporal geological complexity. To achieve this aim, the project will involve:

1) Fieldwork in the Pan de Azucar, Chile, where you will use digital mapping techniques to constrain the style and distribution of structures within a forced fold above a granitic pluton intrusion; this will help ascertain where deformation becomes localized.

2) Mechanical testing of rock samples collected during fieldwork from across and beyond the study area, which will allow you to determine how resistant rocks are to different forms of deformation. We expect that areas where deformation localizes within the uplifting rock will become weaker or stronger, depending on the type of structures formed, and that this change will affect how continued uplift is expressed at Earth's surface.

3) Interpretation of seismic reflection data from offshore New Zealand where several studies have shown that sills are overlain by forced folds that contain numerous onlapped surfaces; these surfaces mark times when the contemporaneous seafloor was uplifted by magmatism. The presence of multiple onlap surfaces indicates that the fold, and thus the underlying sill, grew incrementally over a prolong period of time.

You will reconstruct the ground deformation at each onlap event and compute how ground deformation changes through time; this will be equivalent to analysing the ground deformation signal captured via satellites over timescales of 10's to 100's years, providing a predictive tool for what satellites we may acquire over the next century.

4) State-of-the-art numerical models will be used to establish how the ground deformation signal above intrusions, with a known form, may vary depending on how they are constructed through time.