Tristan da Cunha is an active volcano and a future eruption is inevitable. Knowing when, where and how large the next eruption will be is the aspiration of any volcanologist and is important for those living close to active volcanoes. Unfortunately, the complexities of nature often triumph over scientific knowledge, so volcanologists can only gather clues and use their training, modern scientific techniques and equipment to make a best estimate. In order to ensure estimates are based on the best available knowledge, volcanologists must conduct thorough geological studies on volcanoes. Since the Royal Society Expedition in 1962, there has been little geological fieldwork conducted on Tristan, so the opportunity to spend three months gathering data was an exciting and scientifically valuable prospect.
My arrival on the island was well-timed with the creation of the Tristan disaster preparedness plan. Preparing for a volcanic eruption encompasses a small element of the plan, which also takes into consideration the risk of and response to harbour damage, fire and storms. One of the major objectives of my project is to make a volcanic hazard assessment of the island. To complete this, I needed to collect rock samples and make observations from each of the old eruptive centres (e.g. Hillpiece, Franks Hill, Stony Hill). I also felt it was imperative to understand the working practices on the island, so that the recommendations resulting from the hazard assessment will be appropriate and workable.
During my time on Tristan, I wanted to increase awareness of volcanic hazards and discuss what we know about Tristans geology. As volcanology is currently taught at Class 3 and 4 for the Tristan Studies course, I thought it would be a great idea to talk to the children about my work and organise some field trips to bring the concepts to life. Tristan is a natural playground and offers excellent opportunities to study geology. Following my first presentation to the children, we took the whole class out in the barge for a tour around the island. Volcanic features such as Hillpiece and Burntwood are more instructional when viewed from the sea, so the tour gave the children the opportunity to see the features at close range and ask questions about the processes that gave rise to them. As we travelled around the island, the children counted lava flows at Stony Hill and pointed out the many routes that magma had taken as it travelled vertically through the island. Unfortunately, over half of the class could only enjoy the view for a short time as they quickly succumbed to sea sickness....
Fortunately, the next field trip did not require good sea legs a hike up the 1961 lava dome! Since many of the children had never visited the dome before, it was a fantastic opportunity to allow them access to a feature that has loomed over them for their whole lives. Upon reaching the edge of the peripheral crater, I showed the children the digital thermometer I had been using to measure the temperature of the fumaroles. One by one, each child measured the temperatures of the fumaroles and noted the colourful encrustations and staining around the vents. The children went around to the pinnacle and recorded a maximum temperature of 44.3°C from a vent near the top. A short scramble later, we reached the summit of the dome and I pointed out the various features that we could see from this lofty vantage point. It was also an opportunity for the children to get a birds-eye view of the Settlement and they all scratched their names into the summit geyser (old wood-burning heater) as a reminder of the day.
Thanks to the generosity of the British Geological Survey (BGS), a simple seismometer has been left in the school which will allow the children to monitor earthquakes from around the world by watching the traces appearing on the accompanying computer. The children will be able to calculate the magnitude and location of each earthquake, and perhaps even locate some close to Tristan. The School Seismology Project was set up by the BGS and encourages children to understand the concepts of seismology and earthquakes. The project also involves St Marys sharing their data with other schools from the UK, Cyprus, Turkey and Indonesia who are also participating in the project.
As for my continuing project, I have now collected several kilograms of rock samples from Tristan, which will hopefully reach the UK safely! Over the next year, I will be analysing the samples to discover the age of many of the eruptions around the island. Constraining the age of the eruptions will expand our knowledge of the eruptive history of Tristan and most importantly, note the trends in activity and the periods of dormancy or low activity. Incorporating this empirical data into long term forecasts helps to predict the likelihood of another eruption and the probable modes of activity. I intend to return to Tristan early in 2011 to share my findings and arrange a meeting with the Island Council to discuss possible eruptive scenarios and mitigation measures. Should an eruption occur, it is imperative that islanders, their livelihoods and working practices are minimally affected, so preparation is critical. Even though the likelihood of an eruption is small, it is my hope that, upon completion of the planned evacuation site in the Patches, a full evacuation drill will be conducted. Undoubtedly many lessons will be learned from such an exercise and will only help to increase awareness and improve the disaster plan.
As my three months on Tristan draws to a close, I would like to thank everyone on the island for their kindness and generosity. In particular, special thanks to Leon and Gracie who have become a surrogate family and whose lasting friendship have made my trip both a thoroughly enjoyable one and undoubtedly helped the project to succeed. Fond memories of my time on the island will stay with me forever and I look forward in anticipation to my return early in 2011.
Anna Hicks (née Coulbeck), PhD Researcher, University of East Anglia, UK.