Rift volcanism: past, present, future
Ethiopia is the second most populous country in sub-Saharan Africa, with an estimated population of 110 million (UN, 2017) and population growth rate of 2.7 per cent (Central Statistical Agency, 2013). It suffers from the impacts of a range of natural hazards, including:
- ground cracking
- volcanic eruptions
Volcanic risks in Ethiopia
Whilst there are 59 volcanoes that are believed to be active within the Holocene, the knowledge of the past activity, processes driving activity and current extent of magmatism in Ethiopia is low by comparison with many other areas of the world. However, over 46 per cent of Ethiopia’s population lives within 100 km of a Holocene volcano and are exposed to volcanic hazards (Loughlin et al., 2015).
Our current understanding of volcanic hazards is largely derived from our knowledge and experience of activity in arc and intraplate oceanic settings. Continental rift settings, such as Ethiopia, where both effusive and explosive volcanism occur from fissure swarms, volcanic fields and stratovolcanoes, pose a different suite of challenges. In particular, the threat from large-magnitude explosions and their associated hazards in rift settings, particularly in the East African Rift, has likely been highly underestimated (Aspinall et al., 2011). Rapid population growth and development of towns and cities in this region are continuing with little or no regard for the long-term risks posed.
The RiftVolc project
The BGS is part of a NERC Large Grant to research past and current volcanism and volcanic hazards in the Main Ethiopian Rift. The £3.7 million, five-year long project ‘RiftVolc’ includes the universities of Edinburgh, Bristol, Cambridge, Leeds, Oxford and Southampton as well as Addis Ababa University and the Geological Survey of Ethiopia.
The RiftVolc project builds on previous NERC-funded projects, including the Ethiopia Afar Geoscientific Lithospheric Experiment (EAGLE), the Afar Rift Consortium (ARC) and the Airborne Research Facility‘s (ARF) data acquisition over volcanic complexes in the Afar Depression and the Main Ethiopian Rift. RiftVolc focuses on volcanoes and volcanic plumbing systems in three work packages (past, present and future volcanism) to address fundamental questions, including:
- what has driven eruptions over geological timescales?
- what controls the active magmatic system and volcanic unrest?
- what are the potential threats from future volcanic activity?
We are leading the third work package, investigating potential future volcanic activity in the central Main Ethiopian Rift. An improved understanding of the evolution and functioning of volcanic systems, gained from finding the answers to the first two questions, will provide the foundation on which established and new methods to quantify volcanic hazard from high-risk central volcanoes, active rift segments and volcanic fields will be developed to answer the final question.
Our work includes the following specific research areas.
Our research is focused on probabilistic assessment of volcanic hazards, including:
- ash fall
- pyroclastic density currents (PDCs) and lava flows on volcanic centres that have high population exposure
- recent activity (eruptions; deformation; hydrothermal activity)
The research also represents contrasting styles of historical activity to optimise probabilistic forecasting methodologies for a range of eruptive scenarios.
The hazard assessments are being developed at local, volcano-specific scales for ash fall, PDCs and lava flows and at regional scales for ash fall hazard. To enable hazard analyses, field data collected during the project alongside published data are used to:
- inform frequency and magnitude of previous events
- define values used for modelling
- develop a suite of eruption scenarios
Subsequently, physical and statistical modelling can be run to characterise the inundation by different volcanic hazards, the probability of an area being impacted, and to quantify uncertainty.
In data-poor environments, determining the frequency and magnitude of past eruptions can be very challenging. We use expert elicitation as a tool to characterise the knowledge and opinions of scientific experts in a quantitative way through a series of set questions, to inform uncertainty around frequency-magnitude relationships.
During RiftVolc we have used the SHeffield ELicitation Framework (SHELF), which elicits the judgement of a small number of experts. Elicitation does not provide an answer, rather a step towards better understanding of the volcanic system.
Use of analogues has also been investigated and a tool developed to identify where data-rich volcanic histories may help to plug the gaps in data in Ethiopia (Tierz et al., 2019).
We are supporting the Institute of Geophysics, Space Science and Astronomy at Addis Ababa University, which is a geophysical observatory for Ethiopia, through installation of real-time telemetry for seismometers in the Main Ethiopian Rift to augment initiatives in Ethiopia to improve monitoring capacity.
The development of telemetry accompanies a series of training events from seismology to data processing that have been held in Ethiopia.
We have worked alongside our Ethiopian partners at Addis Ababa University, the Geological Survey of Ethiopia and the National Disaster Risk Management Commission (NDRMC) through a series of workshops in Ethiopia since 2012. Held in 2012, 2016, 2017 and two in 2019, the events have drawn on findings from RiftVolc and the BGS ODA programme to create the platform for our Ethiopian colleagues to make the difference that is needed by providing science to support evidence-based decision making in Ethiopia.
The NDRMC announced via media interviews that they are shifting from reactive crisis management to anticipation of geohazards in response to the most recent workshop.
Aspinall, W, Auker, M, Hincks, T K, Mahony, S, Nadim, F, Pooley, J, Sparks, R S J, and Syre, E. 2011. Volcano Hazard and Exposure in Track II Countries and Risk Mitigation Measures — GFDRR Volcano Risk Study. Bristol University Cabot Institute and NGI Norway for the World Bank: NGI Report 20100806.
Loughlin, S C, Sparks, S, Brown, S K, Jenkins, S F, and Vye-Brown, C. (editors). 2015. Global Volcanic Hazards and Risk. (Cambridge, UK: Cambridge University Press.)
Tierz, P, Loughlin, S C, and Calder, E S. 2019. VOLCANS: an objective, structured and reproducible method for identifying sets of analogue volcanoes. Bulletin of Volcanology, Vol. 81(12), 76.
If you want to discover more then please contact Charlotte Brown.