Unearthing the Secrets of Hill-Fort Vitrification in Early European History

Vitrified hillforts, those further fortified by the melting and fusing of outer rock walls, are found throughout Europe, with a significant number occurring across Scotland. Those specific to Scotland have been dated in origin from the Bronze age to early Medieval history, suggesting a cultural significance to fort vitrification. The circumstances and methods involved in the vitrification of hillforts, however, remain heavily debated.

The process of rock vitrification requires considerable fire technology, capable of melting rock in pervasive temperatures exceeding 1000 degrees C, forming a mineral 'glass'. In contrast, achieving these temperatures in contemporary settings requires complex equipment and experimental processes. This raises considerable questions as to the possibility of fort vitrification in early European history.

An interdisciplinary application of earth science analyses - including rock geochemistry, Raman spectroscopy, and palaeoecology - offers a unique opportunity to investigate how and why fort vitrification was achieved. To answer this, the project will be divided into two main parts.

The first component of the studentship will involve identifying and sampling rock, vitrified glasses, and charcoals from two different hillforts (one in Scotland, and the other in Ireland). Rock and glass samples will be used to conduct mineral analysis to understand changes in rock chemistry during vitrification, and olivine geothermometry (calculating temperatures of melt from olivine cooling rates).

Charcoals, encased within the glass, will be analysed using Raman spectroscopy to calculate the temperatures experienced during the fires. This research will also involve extensive application of the new scanning electron microscope in the School of Geosciences, University of Aberdeen. Comparing and calibrating these methods will help understand and develop new methods of geothermometry, specific to hillfort vitrification.

The second part of this project will include sampling soil and/or peat from each hillfort to identify potential windblown charcoals and pollutant geochemistry that may correspond to the vitrification event. Charcoals and peat/soil chemistry will then be analysed, alongside pollen and macrofossil study, to quantify the types of fuels and accelerants that may have been used during vitrification.

These data will offer insight into how hillfort sites, separated geographically and culturally, were vitrified using different fuels, rock types, and environmental conditions. This information, alongside results from thermometry, will then be used to plan and conduct experiments - attempting to replicate the temperatures required for vitrification in a laboratory setting.

Determining the potential processes and conditions behind fort vitrification may then reveal key information regarding the duration of firing, weather conditions experienced and/or utilised, and the purpose of fort vitrification (armour, arson, or accident). Throughout this project, the student will undertake a mix of fieldwork (UK & International) and laboratory work - including Raman spectroscopy, light microscopy, scanning electron microscopy, and gas chromatography-mass spectrometry (all training provided).

Desirable skills include good experience in any microscopy, and a comfortability with computer-based data processing.