Fig.1 The dead of Herculaneum, burnt to death by 800-centigree hot pyroclastic flows from Vesuvius AD 79 (O Louis Mazzatenta, National Geographic)
The volcanic eruptions of Mount St Helens in 1980 and Nevado del Ruiz in 1985 made the general public aware of the dangers of co-existing with a large and potentially lethal volcano. It doesn’t take much imagination to see the possibilities of a lateral St Helens-type blast on a population of a great city as unaware of the hazard as the unfortunate citizens of Armero, Colombia. Blasts from the past such as Vesuvius 79 AD eruption that obliterated the large Roman cities of Pompei and Herculaneum or the 1902 eruption of Mount Pelée on Martinique, that completely destroyed the town of St Pierre, leaving only two survivors out of a population of some 22,000, served to reinforce the message. With human populations world-wide soaring, it is inevitable that humans will settle closer to potentially active volcanoes in ever-increasing densities. As a result, more human beings than ever are at risk from volcanic eruptions.
With this in mind, the HYPERLINK “http://en.wikipedia.org/wiki/International_Association_of_Volcanology_and_Chemistry_of_the_Earth%27s_Interior” \o “International Association of Volcanology and Chemistry of the Earth’s Interior” (IAVCEI) set out to identify volcanoes that had a history of large, potentially destructive eruptions and were located close to high-density populations. As the project was initiated as part of the United Nations-sponsored International Decade for Natural Disaster Reduction, hence the name Decade Volcano, it was hoped that the United Nations would fund the programme the aims of which was to identify the major strengths and weaknesses of current hazard management and contingency plans at each volcano, and how to address the weaknesses identified.
Fig. 2 The UN General Assembly. It was ultimately here support for the Decade Volcano programme must be obtained, not at some faculty. (Marty Lederhandler, Associated Press)
It must be realised that in a highly politicised world, decisions are rarely based on scientific grounds, but on what is politically feasible. Hence the volcanoes chosen had to have a broad appeal, geopolitical as well as demographic, to the representative body that was to grant the funding. But in order to achieve at least a semblance to a scientifically motivated choice, the volcanoes chosen had to threaten tens of thousands of people with at least two of the following volcanic hazards – lava dome collapse, pyroclastic flows, lava flows, lahars, tephra fall or volcanic edifice instability. Furthermore, the volcano had to have been recently geologically active. As a sop to the UN representatives, who in turn would have to have the sanction of their masters at home, any volcano chosen had to be politically and physically accessible for study and there must also be local support for the work.
In the end, the UN did not undertake to support the programme, and funding had to be obtained elsewhere. Where there is a national body responsible for volcanologic research and monitoring such as in the USA, Italy, Mexico or Colombia, this organisation has assumed responsibility for the volcano or volcanoes that naturally fall under their aegis. The European Union supports research and monitoring at European volcanoes whereas some of its member countries, France and Germany, have undertaken to support the work of Indonesian authorities at the same time giving French and German volcanologists access to research at active volcanoes.
Fig. 3 Koryaksky volcano overlooking Petropavlovsk’s 180,000 inhabitants (Wikimedia)
The 16 volcanoes given status as Decade Volcanoes, with the (main) human habitations threatened given in brackets, are:
USA – Mount Rainier (Seattle, Washington) and Mauna Loa (Hawaii)
Japan – Sakurajima in the Aira caldera (Kagoshima and Kirishima) and Unsen (Unsen and Nagasaki)
Russia – Avachinsky and Koryaksky (Petropavlovsk, Kamchatka)
Italy – Vesuvius (Naples) and Etna (Catania)
Greece – Santorini, a.k.a. Thera (Aegean Islands)
Spain – Teide (Canaries, holiday paradise of Europe)
Mexico – Colima (Colima, Manzanillo)
Colombia – Galeras (Pasto)
Phillipines – Taal (Manilla)
Guatemala – Santa Maria/Santiaguito (Quezaltenango)
Indonesia, Java – Merapi (Yogyakarta)
Democratic Republic of Congo – Nyiragongo (Goma)
Papau New Guinea – Ulawun (???)
While no one doubts that given a possible or hypothetical worst-case scenario, these volcanoes pose a serious threat to nearby human settlements, it’s quite obvious that politics has been a main factor in their selection as Decade Volcanoes. The financially and politically influential USA, Russia and Japan have each been assigned two with four to the equally politically and economically influential Europe, while the large Hispanic contingent of nations accounts for no less than five of the sixteen.
Nevertheless, it is a start and a good one too. The programme has led to a better understanding of the volcanic hazards and in one case, at Etna in 1992, measures were taken on the advice of IAVCEI (International Association of Volcanology and Chemistry of the Earth’s Interior) that eventually prevented a lava flow from reaching a town. Scientists and civil protection authorities have learnt to cooperate as with the very nasty eruption of Merapi in 2010, without which the death toll would undoubtedly have been much higher. Awareness of volcanic hazards from volcanoes not on the list has been heightened as well. A summary of the advances and achievements brought by the first ten years of the programme can be found at “http://www.sveurop.org/gb/articles/articles/decade.htm” Directly below, followers of this blog may be surprised, or not as the case may be, to learn that our old friend Nemesio M. Pérez compiled the final report of the IAVCEI meeting in Teneriffe, 2010.
Fig. 4 The 2334 m high Ulawun stratovolcano, Papau New Guinea (listspress)
But it cannot be claimed that all the Decade Volcanoes represent the 16 volcanic centers most dangerous to human populations, nor that the efforts are directed where they are most needed. Let us look at Ulawun, Papau New Guinea as one example! Ulawun, a 2334 meter high stratovolcano, is the tallest volcano of the Bismarck Archipelago chain and one of the most active volcanoes in Papua New Guinea. According to John Seach, it is composed of lava flows interbedded with tephra and erupts basalt and andesite through Strombolian and Pelean eruptions. Thus the main danger to humans comes from the pyroclastic flows associated with Pelean eruptions, the other Decade criteria met are those of tephra fall and structural failure. John Seach reports that the 1980 eruption resulted in an 18 km high eruption column that devastated some 20 square kilometres and claims that structural collapse could potentially lay waste to an area hundreds of square kilometres. That is an area with a radius of about eight to ten kilometres.
But is Ulawun really such a highly dangerous volcano? First of all, as far as I can tell from maps and satellite images, there are few human habitations within the danger zone. Second, it erupts basalt and andesite, neither of which are associated with particularly devastating eruptions. Basalts erupt effusively as at Hawaii or semi-explosively as at Etna. Andesites predominantly erupt explosively, but rarely result in a high VEI as both volume-wise and explositivity-wise they are small to medium. Third, Ulawun erupts regularly, 34 eruptions over the past hundred years with most assigned a VEI of 1, 2 or 3 with a single VEI 4. While this is impressive and a constant reminder to the locals that theirs is a dangerous volcano, the regular eruptions prevent the build-up of a much larger eruption – and also inhibits the build-up of a large human population on its fertile slopes.
Let’s now move our examining eye some 200 km to the NW of Ulawun! There we find Rabaul, the city of WW II fame fought over by the Japanese and Americans for its superb anchorages. Up until 1994, Rabaul was the provincial capital with a population of some 17,000 inhabitants. On September 19th 1994, the Tavurvur and Vulcan stratovolcanoes erupted simultaneously which destroyed the town as had happened previously in 1937. Fortunately, no more than five people were killed this time against 500 on the previous occasion. Today, the provincial capital has moved to Kokopo, a scant 20 km away, but Rabaul is slowly being rebuilt as happened after its 1937 destruction.
Why is Rabaul then, to borrow a phrase from Carl, such an ill-begotten piece of real estate? The reason for its superb anchorage is that it is a submerged caldera, 8 by 14 km wide. The town is located on the rim of the caldera and there are no less than eight vents of which four are stratovolcanoes such as the already named Tavurvur and Vulcan. Just to make certain of the town’s eventual destruction, the spit of land on which Rabaul is situated is not only the edge of the Rabaul caldera. A scant three kilometres due north lies the equally submerged Tavui caldera, source of the 5100 BC Raluan rhyolitic ignimbrite, an eruption listed as producing 4.0 ± 1.0 x 109 m3 of tephra.
Fig. 6 Map of the Rabaul Caldera (USGS)
No doubt there are other, and better examples of volcanoes that ought to have been Decade Volcanoes instead of some of the obviously less than well-chosen current ones, but it cannot be denied that the project has realised its goals and done so very well indeed! The context of its genesis, well before the advent of the world-wide web with its instantly accessible webcams and monitoring equipment, has to be taken into account as well. In the final analysis, the Decade Volcano programme has to be regarded as being highly successful.