After the recent tragedy on White Island, NZ, Jackie Pomeroy of Mt Agung Daily Report and Rio Helmi  felt that it was imperative to post some reflections on the issue of disaster mitigation given the disregard some tourists have of the warning levels on Mt Agung. Both authors have worked closely with Indonesia’s Indonesia’s Center for Vulcanology and Geological Hazard Mitigation during the recent Mt Agung crisis. (This article was first published on the Mt Agung Daily Report Facebook Page). 
Like many modern-day sciences, the roots of volcanology are found in traditional knowledge passed down from generation to generation. The problem is that much of that traditional evidence is very localized and subjective, as we see in the case of Mt Agung throughout history. Even after the major eruption of 1963-64, accounts of the eruptions and the associated volcanic phenomena varied wildly due partly to the wide variation in phenomena on different sides of the mountain, but also because there was little effort to collate and document a comprehensive account covering all sides and aspects of the erupting volcano. Some of this was clearly due to the lack of the necessary technology, and part can be attributed to nascent institutions in a developing country.
The advent of high-tech precision instruments have greatly improved scientists’ ability to document activity in volcanoes including measuring the inflation and deflation of mountains down to the millimeter, registering the vibration of magma flooding chambers deep underground and the rocking of conduits being broken open to craters, changing internal temperatures and much more. Yet no matter how good your historical data, volcanoes are known to change their behavior and that makes scientists’ ability to predict eruptions a science of probabilities. Better informed probabilities, certainly, but probabilities nonetheless. And this becomes the key issue when we are talking about disaster mitigation.
The main tool of today’s volcano disaster mitigation is the scaled warning level. The typical warning level system ranging from one to four – with four being the highest danger – has been adopted in many parts of the world, with a one to five scale used in some countries, including New Zealand. The warning levels coming from these scales are largely based on informed probabilities using the data obtained from available instruments, past histories and computer modelling that helps to predict the reach of hazards – the main point of mitigation. The USGS uses the following definitions, which are generally reflected in the Indonesian scale.
Level 1 Normal. Volcano is in typical background, noneruptive state or, after a change from a higher level, volcanic activity has ceased and volcano has returned to noneruptive background state.
Level 2 Advisory. Volcano is exhibiting signs of elevated unrest above known background level or, after a change from a higher level, volcanic activity has decreased significantly but continues to be closely monitored for possible renewed increase.
Level 3 Watch. Volcano is exhibiting heightened or escalating unrest with increased potential of eruption, timeframe uncertain, OR eruption is underway but poses limited hazards.
Level 4 Warning. Hazardous eruption is imminent, underway, or suspected.
Above: Media coverage on the day of the eruption
Indonesia’s Center for Vulcanology and Geological Hazard Mitigation (CVGHM or PVMBG in Indonesian) is one of the most experienced agencies in the world, and with nearly 130 active volcanoes in Indonesia this is understandable. But Indonesia’s volcanological history is unfortunately blighted with another distinction: the archipelago has suffered the highest number of eruptions that have resulted in fatalities. Given the high population densities around the fertile, major volcanic areas this is no surprise, but it is often complicated by social and economic patterns.
We saw this with the increase of activity in Mount Agung in 2017-2018: the reluctance of poor farmers high on the volcano to leave behind their only real assets – their livestock – and the non-stop demand for volcanic sand mined high on the volcano for distant construction proved to be complicating factors in developing strategies to mitigate the potential disaster. Warning levels can affect many aspects of life, from government budget resources available for emergency support to insurance availability, and their impact on tourism can have significant repercussions even if tourists are not at risk.
All these factors can (or will) pressurize the decision-making process. PVMBG’s leading volcanologist and head of the Eastern Indonesian sector of disaster mitigation, Devy Kamil Syahbana has stated that it’s better to err on the side of caution, even if your institution comes under fire from political and economic forces, rather than risk the lives of the affected population. Sometimes the technical criteria for the appropriate warning level might not reflect conservative safety standards. For example, an Australian expert who has visited White Island in New Zealand, site of the recent eruption catastrophe, has been quoted describing it as a disaster waiting to happen, yet also commented that he thinks the New Zealand authorities had set the right alert level.[1]
How can these conflicting interests be reconciled? It is worth noting that GNS (the New Zealand volcanology agency, equivalent to PVMBG) reported back in June[2] historically high levels of Sulphur dioxide gas associated with earthquake swarms, but more recent Volcanic Alert Bulletins (VABs) note increased activity with more measured language. Activity such as the tourist visits to the White Island crater would appear to need more detailed risk information, and we do not know the GNS mitigation protocols for this. It is far too early for us to know exactly how and where along the line the visitors’ risk factor fell beyond the line of reasonable caution – for that we will have to wait for the results of the inquiry.
What is absolutely clear is that this tragic event means we can expect a thorough discussion and debate in the next few months on a) the science and the art of setting volcano warning levels, b) effective communications about the levels of risk, and c) collaboration with local communities and authorities on best options for mitigating that risk.
©Rio Helmi and Jackie Pomeroy
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