Overview

Project Highlights:

  • Investigate the properties of erupted magmas spanning major edifice collapses
  • Use a set of unique marine sediment cores (Ritter Island and Montserrat) and post-collapse samples (Anak Krakatau) to reconstruct volcanic records across different timescales
  • Determine how magma storage and ascent processes are affected by edifice growth and destruction

Sector collapses are among the largest volume events to affect volcanic systems, potentially involving the rapid displacement of tens of cubic kilometres of rock. There is growing evidence that such substantial changes in surface loading can have profound effects on the stability of an underlying magma reservoir, potentially manifested through shifts in eruption rate or composition and dominant eruptive behaviour. Nevertheless, a detailed understanding of how and why collapses perturb a magma system is lacking, because of the challenges involved in generating high resolution reconstructions of past eruptive activity that span the periods before and after collapse. This project will take advantage of three unusual datasets to address this problem. The approach will draw on marine sediment samples collected offshore Montserrat (Lesser Antilles) and Ritter Island (Papua New Guinea), as well as samples related to the 2018 collapse of Anak Krakatau (Indonesia). These samples and cores preserve a record of activity at these volcanoes before and after major collapse events, and can advance our understanding of how volcanism at arc-volcanic systems responds to sudden changes in surface loading.

Ritter Island was the site of the largest historical sector collapse (around twice the size of the Mount St. Helens event in 1980), in 1888, and recent analysis of samples collected in 2016 indicates that unusually evolved magmas were erupted immediately following collapse, and that subsequent rebuilding of the submarine cone has produced rocks that are compositionally distinct from those erupted before collapse. The event provides an ideal opportunity to better understand the nature of post-collapse changes in activity. The 2016 samples were the first collected from the 1888 collapse. More will be collected on a planned research ship expedition in 2020. The recent devastating collapse of Anak Krakatau was smaller than that at Ritter, occurring on a young, basaltic volcano. Samples available from across the growth history of Anak, including post-collapse material, will allow a detailed petrological investigation of its evolution, testing results from Ritter.

Montserrat has been subject to multiple large scale sector collapses throughout its history, and provides an opportunity to investigate the impacts of collapse on volcanic behaviour over longer (103-5 year) timescales, thus complementing the higher-resolution, shorter timescale cases above. The student would work with extensive core samples from a 2019 marine expedition (M154-2; stored in Bremen, Germany) and IODP 340.

The RV Sonne collecting data and samples at Ritter Island in 2016. The crescent-shaped remnant of Ritter is all that remains of the subaerial island. The cone has been rebuilding beneath sea-level, with results indicating a shift in magma compositions following collapse.

Methodology

The project student would work with marine volcaniclastic sediment and core samples, applying a range of sedimentological, geochemical and petrographic approaches to investigate the nature of pre- and post-collapse volcanism at Montserrat, Ritter and Krakatau. Work will be undertaken at the University of Birmingham (general stratigraphy, sediment properties, SEM imaging), the University of Oxford (electron microprobe and laser ablation ICP-MS, analysing glass and mineral compositions) and the Natural History Museum (electron microprobe, diffusion chronometry). The student will also work with co-supervisors in Germany on the Montserrat core samples.

From this variety of approaches, the student will acquire evidence for changes in magma chemistry, mineral contents, eruptive style and frequency in both pre- and post-collapse periods, and develop an eruptive chronology (particularly for the Montserrat core datasets) from existing age data, with the potential for additional constraints using 40Ar/39Ar methods.

Using the combined dataset, the student will address whether and how the magmatic plumbing system that previously existed was affected and potentially reorganised following collapse. To develop this interpretation, the student will combine approaches including thermobarometry, textural analyses and diffusion chronometry, working with co-supervisors and facilities at the Natural History Museum and University of Oxford.

Training and Skills

The project student will receive training in core sampling and sedimentological analysis, and the preparation and geochemical analysis of volcaniclastic samples (optical microscopy, SEM analysis, electron probe micro-analysis) and techniques used to investigate and quantify magmatic processes (e.g., diffusion chronometry). There is a potential opportunity to experience marine research through participation in a ship expedition to Ritter, and through this to experience working as part of a major cross-disciplinary international project. The student will work with co-supervisors at facilities in the UK and Germany, with the potential to also gain experience with 40Ar/39Ar dating methods. The project thus provides the opportunity to obtain a wide range of analytical experience and work with varied facilities and several research groups.

Timeline

Year 1: Sampling of Montserrat cores; sedimentological analysis; production of stratigraphy; tephra sample preparation. Sampling and analysis of Ritter datasets. Attendance and presentation at a national volcanology conference.

Year 2: Geochemical and textural analyses of Montserrat samples; development of Ritter eruptive stratigraphy; development of growth history of Anak Krakatau; continuing geochemical analyses.

Year 3: Analysis of magmatic processes and plumbing system structure under pre- and post-collapse conditions, drawing on reconstructions across different timescales and between the different systems. Writing up of project results for publication; presentation at an international conference.

 

Partners and collaboration (including CASE)

The project student will be based at Birmingham but would work closely with co-supervisors at Oxford and the Natural History Museum (a CENTA2 Level 1 partner), making use of laboratory facilities at a number of UK institutions, and with co-supervisors at Bremen and GEOMAR (Germany) working on the Montserrat core dataset. The student will also have the opportunity to build relationships with other international collaborators within these research projects (including in Indonesia and Papua New Guinea).

Further Details

Please contact Dr Sebastian Watt - s.watt@bham.ac.uk

This project will suit a student with an interest and facility for detailed laboratory work, an enthusiasm for volcanology and an interest in working within a collaborative, interdisciplinary project.