Earth processes infographic

Osman, Sara // Investigating tephra loads leading to roof collapse


This infographic summarises my project for attendees of Cities on Volcanoes, a multi-disciplinary conference for volcanologists and emergency planners. Using Ascension Island (a volcanically active UK Overseas Territory in the South Atlantic) as a case study, I am modelling volcanic eruption scenarios and assessing roof vulnerability to loading from tephra (particles erupted during explosive eruptions). I will then adapt the Structural Eurocode approach to designing roofs for snow loads, to make it applicable to designing buildings to withstand tephra loads.


Tephra fallout (ejected particles of all sizes) from volcanic plumes can lead to significant additional loading on roofs and collapse can occur when tephra is just 10-20 cm thick.

Buildings are often designed to withstand snow loading and this project is testing whether a similar approach, following the Structural Eurocode standards, could be used for tephra loading.

  • Laboratory tests to Investigate tephra sliding behaviour on various roof materials, using a tilt table.
  • Adapting the snow load Eurocodes by identifying roof shape coefficients (μ) for tephra loading which can be used in building design calculations.
Ascension Island case study

Ascension Island (a volcanically active UK Overseas Territory in the South Atlantic) will be used a case study to test out the project’s methods. Modelling of eruption scenarios will identify areas of the island which might be at risk during an eruption and building surveys in the main settlements will identify key building characteristics (eg. roof shape, pitch and material) so that roof vulnerability can be assessed.

  • Roof vulnerability assessment, to be shared with Ascension Island Government.
  • Roof shape coefficients, to be used in designing roofs to withstand tephra fall.
  • Methodology applicable to other volcanic areas to identify buildings at risk of roof collapse.

Sara Osman

Sara is a second year PhD student at the University of Leeds. Her project, ‘Assessing roof vulnerability to collapse from tephra fall loading, with relevance to Ascension Island’, is supported by the British Geological Survey (BUFI studentship). Her previous Masters research included investigating how the grain size distribution used to initialise ash dispersal models impact the modelled ash plume (University of Bristol) and assessing the hazard associated with large clasts falling from volcanic plumes at Mount Etna (University of Portsmouth).

Sara’s University of Leeds profile


Organisation: University of Leeds and British Geological Survey