Project highlights

  • Fieldwork in the Yellowstone hotspot track in southern Idaho and Nevada, USA
  • Physical volcanology of a super-eruption
  • Variations in glass chemistry used to track what happens during a catastrophic event
  • Training in modern fieldwork and micro-analytic techniques within a dynamic research team.

Overview

Much attention has been given to identifying giant explosive volcanic eruptions in the geological record, and estimating their size and frequency. Less attention has been given to what actually happens during one of these eruptions; e.g. what are the physical processes, how long do they last, and how does a single eruption evolve with time? It is becoming apparent that the style of giant eruptions may differ fundamentally from the largest (e.g. Plinian) historic eruptions1,2. Resolving these issues is important if we are to understand the wider effects of major events1.

This PhD project aims to develop new understanding about what happens during a super-eruption. It focusses on an eruption in Idaho, USA, with a volume of  ≤ 2800 km3 (magnitude 8.8) – the largest and hottest eruption from the Yellowstone hotspot yet documented3. The single welded ignimbrite covers ≥23,000 km2 – an area larger than Wales. It is well-exposed4 allowing field access to ashfall layers and associated ignimbrite, both proximally and distally. The student will document the internal stratigraphy of the deposit in the field, followed by micro-analysis of the glassy ash textures and compositions at different heights, to track how physical processes evolved with time, during the eruption. Results will be used to develop a new model of how the largest eruptions on Earth begin, wax to a peak and then wane, and how the ash from them is more widely dispersed. The project will draw from the latest advances in understanding of large explosive eruptions2, and should improve our understanding of some of the largest events on Earth.

Graph of super eruption on left, photo of volcanic rocks on right.

Fig. 1: Are plumes of super-eruptions really doughnut-shaped? (simulation from 2).
The evidence lies in vast pyroclastic sheet-like deposits; Snake River ignimbrites, USA1 (right).

Host

University of Leicester

Theme

  • Organisms and Ecosystems

Supervisors

Project investigator

Professor Michel J Branney, The University of Leicester ([email protected])

Co-investigators

Dr Tiffany Barry, The University of Leicester ([email protected])

How to apply

Methodology

The deposits of a single rhyolitic eruption will be logged and sampled in detail at numerous locations, in Idaho and neighbouring states. Geochemical analysis of individual glass shards5 at different levels in the deposit will be used to define time-lines (‘entrachrons’ 5) that can then be used to correlate with ultra-high precision across 100’s of km. This approach will allow us to distinguish between successive time-slices (windows of just a few minutes) during an evolving, protracted volcanic eruption. Where conventional sieving is precluded by welding, new robust techniques developed by the research group will then be employed to quantify the different grainsizes and sorting characteristics of the deposit and used to deduce how each time-slice within it was deposited. The project will, for the first time, produce a time-series of data through a geographic spread of sites, both near to, and far from, the supervolcano. This will provide a unique basis on which to reconstruct how successive events unfolded at different locations as the eruption began, waxed and waned, and as the various types of atmospheric plume and density currents developed and shifted geographically during the eruption. Such detailed reconstruction has not been attempted before on eruptions of this scale.

Training and skills

This project will suit a hard-working, curiosity-motivated student who enjoys the outdoors and is capable of independent travel in remote regions. Hands-on training will be given in physical volcanology field and laboratory techniques, including pyroclastic granulometry and shape analysis, optical and SEM micrscopy, analytical SEM, EMP and LA-ICP-MS analysis of volcanic glasses6. The student will benefit from training in interpretative geochemistry, interpreting field relations, and the sedimentology of fine ashes. By the end of the project the student will have gained expertise in the field interpretation of pyroclastic deposits and in a variety of state-of-art laboratory techniques, ideal to launch a career in academic research or industrial-based research. Across 3 years the student will also receive 50 days of other training provided by CENTA2 and ‘free choice’ external training.

Partners and collaboration

The student will benefit collaboration with experts in a dynamic international research group at Leicester who investigate extreme events including large volcanic eruptions and asteroid impacts. The project will involve local collaborators in the western USA.

Further details

For informal enquiries please contact Professor Mike Branney ([email protected] ) at the University of Leicester. Google ‘Volcanology at Leicester’.

If you wish to apply to the project, applications should include:

  • A CV with the names of at least two referees (preferably three and who can comment on your academic abilities)

Applications to be received by the end of the day on Wednesday 11th January 2023. 

Possible timeline

Year 1

Development of methods followed by initial fieldwork. Prior to the first field-season in USA field training in logging and interpreting pyroclastic deposits will be provided locally (UK or Canary islands). Fieldwork to Idaho in late Spring to log and collect key sections. Directed reading and optical microscopy, followed by SEM and LA-ICP-MS analysis of glass shard and crystal populations in rock thin-sections to determine the best ways to characterise chemical and textural variations with stratigraphic height. Conference and fieldtrip participation.

Year 2

Geochemical and shard textural micro-analysis of samples collected in 1st field season, data analysis, developing discriminate plots to track temporal changes during the eruption. Quantitative analysis of ash granulometry, with initial interpretations. Conference presentation of initial findings. Second field season in USA to document and sample more distal successions, exploration of new distal sites.

Year 3

Working-up data from 2nd field visit, for detailed comparison between proximal and distal data sets. Discussion with eruption modellers and development of a field-constrained interpretation of the evolving progress of a large super-eruption. Presentation of findings at an international conference. Writing-up thesis and publications.

Further reading

1Branney, M.J., Bonnichsen, B., Andrews, G.D.M., Ellis, B., Barry, T.L., McCurry, M. 2008. ‘Snake River (SR)–type’ volcanism at the Yellowstone hotspot track: distinctive products from unusual high-temperature silicic super-eruptions’. In: Leeman, B., and McCurry (eds). 2008. Volcanism and petrogenesis of the anorogenic rhyolites, Bulletin of Volcanology 70: pp. 293-314.

2 Costa, A., Suzuki, Y.J. and Koyaguchi, T., 2018. ‘Understanding the plume dynamics of Explosive super-eruptions’. Nature Communications 9:654 doi: 10.1038/s41467-018-02901-0

3Knott, T.R., Branney, M.J., Reichow, M.K., Finn, D.R., Tapster, S., Coe, R.S. 2020. ‘Discovery of two new superuptions from the Yellowstone hotspot: Is Yellowstone hotspot waning?’ Geology 48. https://doi.org/10.1130/G47384.1

4Andrews, G.D. M., Branney, M.J. 2011. Emplacement and rheomorphic deformation of a large rhyolitic ignimbrite: Grey’s Landing, southern Idaho. Geological Society of America, Bulletin 123: 725-743. doi: 10.1130/B30167.

5Branney, M.J. and Kokelaar, B.P., 2002. ‘Pyroclastic density currents and the sedimentation of ignimbrites’. Geological Society of London, Memoirs 27. pp. 152.

6Pearce, N.J.G. Westgate, J.A., Perkins, W.T., Preece, S.J. 2003. The application of ICP-MS methods to tephrochronological problems. Applied Geochemistry 19: pp. 289-322.

COVID-19

The research can begin without an initial sampling visit to the USA, because we hold a large collection of ignimbrite and tephra samples. Thereafter the student would would normally undertake independent fieldwork and sampling (Leicester allows safe fieldwork during the pandemic) but should the pandemic prevent this, our group includes local geologists, who could collect and ship samples to the UK. The analytical work can be done safely in-house at the University of Leicester, and international conference attendance could proceed on-line if required.