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Many volcanoes worldwide still have poorly resolved eruption histories, with the date of the last eruption often undetermined. One such example is Ascension Island, where the timing of the last eruption, and consequently, the activity status of the volcano, is unclear. Here, we use the 40Ar/39Ar dating technique to resolve ages of the three youngest lava flows on the island, which are hawaiites and mugearite with 1.5 – 1.9 wt% K2O. In dating these lavas, we provide the first evidence of Holocene volcanic activity on Ascension (0.51 ± 0.18 ka; 0.55 ± 0.12 ka; 1.64 ± 0.37 ka), determining that it should be classed as an active volcanic system. In addition, we demonstrate that the 40Ar/39Ar method can reproducibly date mafic lava flows younger than 1 ka, decreasing the gap between recorded history and geological dating. These results offer new prospects for determining patterns of late-Holocene volcanic activity; critical for accurate volcanic hazard assessment.

Collaborative research projects have a significant role in filling the knowledge gaps that are obstacles to the rigorous assessment of volcanic hazards in some locations. Research is essential to generate the evidence on which raising awareness of volcanic hazards, monitoring and early warning systems, risk reduction activities and efforts to increase resilience can be built. We report the current state of volcanic hazards research and practice in Ethiopia and on the collaborative process used in the Afar Rift Consortium project to promote awareness of volcanic hazards. Effective dissemination of findings to stakeholders and the integration of results into existing practice need leadership by in-country researchers, effective long-term collaboration with other researchers (e.g. international groups) and operational scientists, in addition to integration with existing programmes related to disaster risk reduction initiatives.

1. An introduction to global volcanic hazard and risk S. C. Loughlin, C. Vye-Brown, R. S. J. Sparks, S. K. Brown, J. Barclay, E. Calder, E. Cottrell, G. Jolly, J.-C. Komorowski, C. Mandeville, C. Newhall, J. Palma, S. Potter, G. Valentine, B. Baptie, J. Biggs, H. S. Crosweller, E. Ilyinskaya, C. Kilburn, K. Mee and M. Pritchard 2. Global volcanic hazard and risk S. K. Brown, S. C. Loughlin, R. S. J. Sparks, C. Vye-Brown, J. Barclay, E. Calder, E. Cottrell, G. Jolly, J.-C. Komorowski, C. Mandeville, C. Newhall, J. Palma, S. Potter, G. Valentine, B. Baptie, J. Biggs, H. S. Crosweller, E. Ilyinskaya, C. Kilburn, K. Mee and M. Pritchard 3. Volcanic ash fall hazard and risk S. F. Jenkins, T. M. Wilson, C. Magill, V. Miller, C. Stewart, R. Blong, W. Marzocchi, M. Boulton, C. Bonadonna and A. Costa 4. Populations around Holocene volcanoes and development of a Population Exposure Index S. K. Brown, M. R. Auker and R. S. J. Sparks 5. An integrated approach to Determining Volcanic Risk in Auckland, New Zealand: the multidisciplinary DEVORA project N. I. Deligne, J. M. Lindsay and E. Smid 6. Tephra fall hazard for the Neapolitan area W. Marzocchi, J. Selva, A. Costa, L. Sandri, R. Tonini and G. Macedonio 7. Eruptions and lahars of Mount Pinatubo, 1991-2000 C. G. Newhall and R. Solidum 8. Improving crisis decision-making at times of uncertain volcanic unrest (Guadeloupe, 1976) J.-C. Komorowski, T. Hincks, R. S. J. Sparks, W. Aspinall and CASAVA ANR project consortium 9. Forecasting the November 2010 eruption of Merapi, Indonesia J. Pallister and Surono 10. The importance of communication in hazard zone areas: case study during and after 2010 Merapi eruption, Indonesia S. Andreastuti, J. Subandriyo, S. Sumarti and D. Sayudi 11. Nyiragongo (Democratic Republic of Congo), January 2002: a major eruption in the midst of a complex humanitarian emergency J.-C. Komorowski and K. Karume 12. Volcanic ash fall impacts T. M. Wilson, S. F. Jenkins and C. Stewart 13. Health impacts of volcanic eruptions C. Horwell, P. Baxter and R. Kamanyire 14. Volcanoes and the aviation industry P. W. Webley 15. The role of volcano observatories in risk reduction G. Jolly 16. Developing effective communication tools for volcanic hazards in New Zealand, using social science G. Leonard and S. Potter 17. Volcano monitoring from space M. Poland 18. Volcanic unrest and short-term forecasting capacity J. Gottsmann 19. Global monitoring capacity: development of the Global Volcano Research and Monitoring Institutions Database and analysis of monitoring in Latin America N. Ortiz Guerrero, S. K. Brown, H. Delgado Granados and C. Lombana Criollo 20. Volcanic hazard maps E. Calder, K. Wagner and S. E. Ogburn 21. Risk assessment case history: the Soufriere Hills Volcano, Montserrat W. Aspinall and G. Wadge 22. Development of a new global Volcanic Hazard Index (VHI) M. R. Auker, R. S. J. Sparks, S. F. Jenkins, S. K. Brown, W. Aspinall, N. I. Deligne, G. Jolly, S. C. Loughlin, W. Marzocchi, C. G. Newhall and J. L. Palma 23. Global distribution of volcanic threat S. K. Brown, R. S. J. Sparks and S. F. Jenkins 24. Scientific communication of uncertainty during volcanic emergencies J. Marti 25. Volcano Disaster Assistance Program: preventing volcanic crises from becoming disasters and advancing science diplomacy J. Pallister 26. Communities coping with uncertainty and reducing their risk: the collaborative monitoring and management of volcanic activity with the Vigias of Tungurahua J. Stone, J. Barclay, P. Ramon, P. Mothes and STREVA.

Originally prepared for the United Nations Office for Disaster Risk Reduction, this is the first comprehensive assessment of global volcanic hazards and risk, presenting the state of the art in our understanding of global volcanic activity. It examines our assessment and management capabilities, and considers the preparedness of the global scientific community and government agencies to manage volcanic hazards and risk. Particular attention is paid to volcanic ash, the most frequent and wide-ranging volcanic hazard. Of interest to government officials, the private sector, students and researchers, this book is a key resource for the disaster risk reduction community and for those interested in volcanology and natural hazards. A non-technical summary is included for policy makers. Regional volcanic hazard profiles, with invaluable information on volcanic hazards and risk at the local, national and global scale, are provided online. This title is available as an Open Access eBook via Cambridge Books Online.