The preservation of volcanic ash from Iceland in northern Scotland

Overview

The overall aim of the project is to understand the preservation of airborne volcanic ash (tephra) from small- and medium-scale eruptions. Tephra from eruptions of this scale can be disproportionately disruptive to aviation (e.g., the Eyjafjallajökull eruption in 2010 led to the cancellation of >100,000 flights), so it is important to understand how often it enters UK airspace and the areas it can affect. The observational record is short (in geological terms,) but the frequency and extent of tephra deposition can be inferred from sedimentary records. Small- to medium-scale eruptions like Eyjafjallajökull in 2010 are common; furthermore, studies of tephra deposits invisible to the naked eye (cryptotephras) have revealed that fine tephra shards can be transported over continental-scale distances. Given this, the UK sedimentary record should be packed with tephra from small- to medium scale Icelandic eruptions. However, this is not the case, indicating that we could be underestimating the incursion of volcanic ash into UK airspace. The sparsity of tephra from small- to medium-scale eruptions could be because there is a minimum intensity of fallout below which preservation is unreliable; alternatively, it could be due to variability in preservation (taphonomy) among different environments (e.g., lakes and peatlands) or a consequence of under-sampling. This project will focus on locations in the UK where tephra fallout has been recorded, in order to understand how that tephra was preserved in the sedimentary record (or not).

The project addresses three main challenges:
Component 1: We need to understand if there is a minimum threshold for the preservation of cryptotephras so we can assess the visibility of small- to medium-scale Icelandic eruptions in the UK sedimentary record.
Component 2: We need to understand the extent to which taphonomic processes in different environments might produce very different crypotephra records from the same initial deposit.
Component 3: We need to understand how cryptotephra deposits vary within individual lakes, in order to optimise sampling strategies.

Methodology

The project will focus on tephra originating from the eruptions of the Icelandic volcanoes Eyjafjallajökull in 2010 (Ey2010) and Grímsvötn in 2011 (G2011). Sufficient time has elapsed for this tephra to become part of the sedimentary record and it should be relatively accessible (i.e., close to the surface). Field sites will be located in the north of Scotland and the Northern Isles (Shetland and Orkney), because we know from satellite observations that Ey2010 and G2011 tephra was deposited in this region and we have records of fallout intensity. Northern Scotland also has many small lakes and extensive peat cover, facilitating comparisons between terrestrial and aquatic environments.

The project will involve: identifying field sites for which there are models and observations (surface or satellite) of the initial tephra deposit; field sampling (lake coring and peat monolith extraction) and laboratory work (the isolation, microscopic examination and geochemical analysis of tephra grains).

To address Component 1 the candidate will collect sediment samples from multiple locations across northern Scotland, recording the presence/absence and (if present) shard density of the cryptotephras. In Component 2 the candidate will extract replicate lake cores from a subset of the locations identified in Component 1 that contain the target cryptotephras. Peat monoliths will be taken from adjacent sites. The lake cores and peat will be compared to quantify variability of cryptotephra preservation in each depositional environment. For Component 3 the candidate will design a sampling strategy and take replicate cores from different locations within the same lake basin to quantify spatial variability in taphonomic conditions. For each component, the provenance of the tephra shards will be determined by geochemical analysis, using an electron microprobe at St Andrews University.

Project Timeline

Year 1

Literature review and site selection; training in lake coring and peat monolith extraction; sampling of first target areas in mainland Scotland (Component 1); training in tephra isolation and microscopic examination (residential course at Royal Holloway, UL).

Year 2

Completion of sampling in Northern Isles (Components 1-3); isolation of tephra from samples and microscopic examination (Components 1 & 2); training in geochemical analysis (St Andrews).

Year 3

Continuation of tephra analysis, including geochemical analysis on microprobe; attendance at major international conference (e.g., EGU); writing up.

Year 3.5

Writing up, manuscript production.

Training
& Skills

The candidate will receive training in the following areas: sampling design; field sampling of tephra (lake coring and extraction of peat monoliths); tephra analysis (extraction and microscopic examination, following by geochemical analysis on the microprobe in St Andrews); statistical analysis.

References & further reading

Cashman, K.V., & Rust, A.C. (2020). Far‐travelled ash in past and future eruptions: combining tephrochronology with volcanic studies. Journal of Quaternary Science, 35: 11–22.
McNamara, K., et al. (2019). Comparison of lake and land tephra records from the 2015 eruption of Calbuco volcano, Chile. Bulletin of Volcanology, 81.
Stevenson, J.A., et al. (2013). UK monitoring and deposition of tephra from the May 2011 eruption of Grímsvötn, Iceland. Journal of Applied Volcanology, 2: 1–17.
Stevenson, J.A., et al. (2012). Distal deposition of tephra from the Eyjafjallajökull 2010 summit eruption. Journal of Geophysical Research, 117.

Further Information

Contact Dr Nick Cutler (nick.cutler@newcastle.ac.uk), Dr Richard Streeter (rts3@st-andrews.ac.uk ) or Dr Helen Mackay (helen.mackay@durham.ac.uk) for further details.

Apply Now