The police do not expect to find survivors. On New Zealand's White Island, at least five people died in a volcanic eruption on Monday, and 31 were injured. Eight persons are still missing. The victims had come to the island as tourists. Prime Minister Jacinda Ardern now wants to clarify why the sightseeing tours were not stopped.
Just a few weeks before the accident Geonet geological monitoring center upgraded the volcano's activity from 1 to 2 - the scale goes up to a maximum of 5. At that time, sulfur dioxide increasingly escaped from the depths of the volcano. In addition, the experts increasingly documented movements of the mountain.
However, the degree of activity of a volcano only provides limited information about the risk of an eruption. "Our volcanoes can break out at any activity level," writes Geonet on his website. So entering an active volcano is always a risk. According to experts, it was only a matter of time before disaster hit White Island.
New Zealand's most active and largest volcano
White Island has been the most active volcano in New Zealand for decades. Eruptions shook the island repeatedly in the years 1975 to 2000. The second known outbreak series began according to Geonet in 2011. It continues to this day. Even in a calm state, steam often rises from the surface of the fire mountain. In the Maori language, White Island is called "Te Puia o Whakaari" - the dramatic volcano.
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The special thing about White Island is its layout and location. The volcanic cone protrudes 900 meters above sea level, but the entire volcano is much larger. 70 percent of the structure is under water. In the crater is a lake. Considering the underwater part of the volcano, it is the largest in New Zealand. However, not its dimensions but the availability of water make it unpredictable.
The White Island volcano does not just break out when the pressure in its magma chambers gets too big, which is comparatively easy to predict. Also, when water in the rock spores of the volcano evaporates abruptly, it comes to violent eruptions. The talk is then of phreatic explosions that can occur without any warning.
Steam explosion blows rocks from the volcano
Starting point are so-called hydrothermal systems in the volcanic rock, explains the volcanic expert Shane Cronin of the University of Auckland at "The Conversation". In these systems, extremely hot water is trapped in rock spores. The pressure inside these capsules is huge and ensures that the water does not evaporate despite its high temperature.
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Volcanic eruption in New Zealand: 3600 meter high ash cloudThe slightest change in the environment of the pores can lead to the pressure escaping. Then it comes to the steam explosion. The water is suddenly gaseous due to the pressure relief and takes about 2000 times the volume. The released energy is enough to blow up solid rock. The water vapor struggles to the surface of the volcano and tears rocks and ashes with it.
"We know of places in New Zealand that have been blasted from over three kilometers away," says Cronin. The ash cloud over White Island lasted three kilometers on Monday. What triggered the explosion is still unclear. Movements in the subsurface, pressure changes due to migrating gases in the rock or changes in the water level in the crater lake could be conceivable.
Too dangerous for mass tourism
One thing is certain: outbreaks like these are typical of White Island. In the past eight years alone, there have been six minor eruptions, said Ben Kennedy of the University of Canterbury, UK. At that time no one came to harm, because due to bad weather or the time of day no tourists stayed on the island.
AUCKLAND RESCUE HELICOPTER TRUST / HANDOUT / EPA-EFE / REX
White Island volcano on December 9, 2019: Huge gas explosion
In the "New Zealand Herald" experts come to a similar assessment. He visited White Island twice, always thinking it would be too dangerous to bring groups there on a daily basis, said Ray Cas, emeritus professor at Monash University, Australia. Jessica Johnson of the UK University of East Anglia described Monday's incident in the article as "unhappy, but not totally unexpected". A disaster with announcement.
