Cataclysmic eruptions in densely populated areas: the ticking eruptive clock at Popocatepetl volcano (Mexico).

Andesitic stratovolcanoes are the most explosive volcanoes on our planet. On a societal level, they have great impact on the proximal region and human population, whilst on a larger Earth system scale, they affect climate and are thought to be key to the evolution of continental crust. The timescales over which an explosive andesitic stratovolcano switches from low-to-moderate explosive activity to cataclysmic Plinian eruption are fundamental in assessing volcanic hazards and safeguarding the lives of threatened human populations. Popocatépetl (Popo) volcano in Mexico is one of the most explosive andesitic stratovolcanoes in North America and one of the ten most populated active volcanoes in the world, threatening an overpopulated area (>20 million) including Mexico City. Its volcanic and magmatic history is well known and is characterised by a wide range of eruption styles including catastrophic Plinian events, effusive activity and moderate explosive Vulcanian activity separated by long but variable periods of quiescence. Key uncertainties at Popo (and in similar volcanoes) are the timescales over which the volcano reactivates or changes eruptive styles and whether these timescales relate to magma recharge of the system. The proposed work addresses these uncertainties via the following over-arching questions:
1) How and on what timescale do intermediate stratovolcanoes change their eruptive behaviour from low-to-moderate explosive activity to catastrophic Plinian eruption?
2) What (if any) is the relationship between timescales, eruptive style and magma recharge flux?
Popo represents a natural laboratory to answer these questions: by linking timescales derived from a variety of geochemical techniques to explore crystal residence times and crystal isotope stratigraphies we can determine the main cause(s) of the switch from moderate explosive eruption to highly-explosive catastrophic Plinian activity and inform hazard assessment on the timescales of magmatic processes and durations of quiescence that can be expected for different eruptive styles. We investigate the existing paradigm that an invers causal relationship exists between the flux of magma injection (i.e., frequency of mixing) and magnitude of volcanic eruption, at a constant crustal magma-supply rate. If flux of magma injection is directly related to explosive magnitude, then we would expect lower frequency of injection to eventually result in more explosive activity. Conversely, periods of high frequency of injection would be predicted to result in more effusive activity. A key question, therefore, is whether a distinct decrease in mixing frequency can be geochemically identified leading up to an explosive Plinian event?
We propose an innovative, multi-proxy approach combining crystal residence time and crystal isotope stratigraphy to provide a critical step forward in understanding past eruptive behaviour at Popo. Thus this work will enhance volcanic hazard assessment and provide a guideline for similar volcanic systems.

The results of this research are widely applicable to people and governments living nearby explosive volcanoes worldwide. We aim to "export" our working tool (linking geospeedometry and crystal isotope stratigraphy to obtain a time-related model of past eruptive behaviour) in the form of dissemination of the results via the NHM website, international and local press and direct contact, with volcano monitoring centres. One immediate contact will be established with Colima and Central America Volcano Observatories. This is relatively easy to achieve given the link of PP Delgado with them. Contact with the STREVA group (see Academic Beneficiaries) has already been established and a constant dialogue will be in place to exchange results and build up on their expertise in raising volcanic hazard awareness among local communities. We also look to communicate with BGS Edinburgh (Dr. Susan Loughin). This would have a wide application and immediate impact as they advise on volcanoes worldwide.
The main wider impact of this research is on Mexican authorities via the possibility to time-constrain multiple pre-eruptive magmatic events at Popo offering a working model of Popocatepetl's past eruptive behaviour. We will offer this information to CENAPRED (Mexican National Centre of Disaster Prevention) and local authorities in the form of seminars explaining the main results linking timescales and dynamics of volcanic activity with different style of eruptions. The final aim is to set the ground for a future real-time petrologic "monitoring" tool linking the pattern of seismicity and gas emission with timescale of syn-eruptive events. This has several important implications for risk mitigation and hazard assessment, but in order to make that link it is important to have a good knowledge of magmatic timescales and a good understanding of the magmatic implication of petrologic timescale.
The project has direct impact on the Mexican local communities (i.e., Parque Nacional Itza-Popo), and on the local schools, which will be involved during the project via the NHM Nature Live School Outreach Program. The results of the project will be communicated and disseminated. By involving the local communities and engaging in a dialogue with the children on the impact of the volcano on their lives and how scientific research can mitigate the risk, we aim to inspire the next generation of scientists in this field and raise volcanic hazard awareness.
The results of the projects will be widely disseminate to primary and secondary schools from across the UK and to the general public of NHM (~5.5 million visitors per year) via the involvement of NHM Public Engagement and NHM School Program. We plan to design and run a specific workshop (see Pathway to Impact) aimed at: demonstrated how scientific research can make a difference in understanding and mitigating volcanic risk; inspire the next generation of scientists in this field; raise volcanic hazards awareness showing how scientists can help in tackling important societal issues.
The proposed project falls within the remit of the Resilience to Environmental Hazards strand of the NERC strategy. A major element of the project is to reconstruct a time-related model of Popocatepetl past eruptive behaviour with the final aim of contributing to a better understanding of the behaviour of volcanic systems and volcanic hazard assessment.
The project is relevant to Natural History Museum's science strategy and will open a completely new strand for NHM science that will fit with two of the Five Challenges of the strategy (Challenge 4: Natural Resource and Hazards, and Challenge 5: Science, Society and Skill). There has been a lot of public interest generated around the recent NHM fieldtrip to Popocatépetl and the new gallery Volcanoes and Earthquakes, reopened last January, hosts a section dedicated to Popo and related samples. The outcome of this project will further boost the interest of the public.