CR2025_10 New insights into the timing and scale of past Mediterranean volcanism and climate change from Lake Ohrid (Macedonia/Albania).

Lead Supervisor: Paul Albert, Department of Geography, Swansea University

Email: p.g.albert@Swansea.ac.uk

Co-supervisors: Siwan Davies, Department of Geography, Swansea University; Bernd Wagner, Department of Geology and Mineralogy, University of Cologne

The coastal Neapolitan area (Italy) is one of the most densely populated volcanic regions in the world; more than three million people live within 10 km of the active volcanoes of Campi Flegrei, Vesuvius and Ischia, and are at risk from explosive volcanism. Campi Flegrei is showing increasing signs of unrest focusing attention on the associated risks to the region^[1]. Accurately reconstructing the eruptive histories of these volcanoes, including determining the frequency and magnitude of past explosive activity, is a critical to forecasting future eruption scenarios and hazard assessments, both for the Neapolitan area, but also the wider Central Mediterranean at risk from widespread ash fall events.

However there remains a significant problem, volcanic reconstructions largely focus on near-source eruption records, which are inherently fragmentary, resulting in eruption under-recording^[2-4]. Gaps in the eruption record are more acute further back in time and, as such, reconstructions are biased towards more recent and better-preserved records, which only provide short snapshots in time and do not reflect the full range and frequency of volcanic activity. Low- to mid-intensity explosive eruptions are particularly susceptible to under-recording, but the problem also extends to large magnitude events^[5].

To overcome this problem, this project will capitalise on the huge potential of long, undisturbed records of ash (tephra) fall events preserved in sedimentary archives (e.g. lacustrine/marine cores) far from the volcano, to fill the gaps in eruption records. The student will exploit microscopic ash layers (known as cryptotephra) as a tool for resolving the low- to mid-intensity explosive eruptions. The initial focus will be on identifying cryptotephra layers preserved in the iconic Lake Ohrid (DEEP site) sedimentary archive. This record from the Balkans, was cored as part of the International Continental Drilling Program (ICDP), and spans a continuous and unrivalled 1.364 million years of Mediterranean climate history^[6]. Critically, this sediment record is ideally located down-wind of the active Neapolitan volcanoes, and is an ideal depositional site/basin for preserving an undisturbed record of ash fall events^[7].

The project aims to; (1) reconstruct a long, comprehensive ash fall record from the Lake Ohrid sediments spanning approximately the last 150,000 years; (2) integrate these ash fall events with those recorded in other distal archives to better constrain the timing, scale and ash dispersal patterns of past Neapolitan explosive eruptions, including through the use of ash dispersion models; (3) use the cryptotephra layers traced across Mediterranean palaeoclimate archives as time-markers to assess the regional development of past climate changes spanning the last interglacial-glacial cycle.

The student will undertake a range of laboratory based volcanic investigations, for instance, density separation techniques will be employed to extract and identify cryptotephra, while major (EMP) and trace element (LA-CP-MS) glass geochemistry will be used to determine their volcanic source, and identify potential source eruptions. These geochemical fingerprints will also be used to correlate the Lake Ohrid cryptotephra layers to those ash fall deposits preserved in other key regional sedimentary records. Reliably correlating ash fall layers between sedimentary successions will be essential for precisely constraining the fall footprint and scale of individual eruptions, whilst also accurately assessing eruption frequencies. The student will also explore the potential of refining the Lake Ohrid age-depth model by integrating existing absolute ages (e.g., ⁴⁰Ar/³⁹Ar) of those eruptions preserved in the near-source, and transferring them to Lake Ohrid record, via cryptotephra occurrences. Improved chronological constraints placed upon the record will enhance the potential to explore the spatio-temporal palaeoclimatic change across the Mediterranean region.

Training opportunities:

The student will receive training in field and laboratory based volcanic studies. They will be trained in sediment core logging and sampling, the extraction and identification of cryptotephra from within sedimentary successions. Furthermore, they will be trained to undertake analytical techniques used to chemically fingerprint the ash fall deposits identified, such as electron microprobe (EMP) and LA-ICP-MS analysis. The student will have the opportunity for field based volcanological training with regards to recording and sampling near-source tephra deposits. They will receive training in the application of computational and geochronological methods, used for age-depth modelling and ash dispersion modelling.

Student profile:

This project would be suitable for students with a degree in Geology / Physical Geography, or a closely related environmental or physical science.

References:

1. Astort, A., et al. (2024) Nature Communications Earth and Environment 5; 506.
2. Kiyosugi, K., et al. (2015) Journal of Applied Volcanology 4:17.
3. Self, S. & Gertisser, R. (2015). Nature Geoscience 8, 248–250.
4. Brown, S et al., (2014). Journal of Applied Volcanology 3, 5.
5. Albert et al. (2019) Geology 47 (7), 595-599.
6. Wagner et al. (2019) Nature 573, 256-260.
7. Leicher et al. (2019) Quaternary Science Reviews 226, 106021.