white island eruption, hydrothermal
© Michael Schade

Following the death of five people due to the White Island eruption within New Zealand’s waters, questions are being asked as to why tourists were allowed access to the crater

Police have confirmed that there were 47 tourists on White Island at the time of the eruption (14:00 local time, 9 December). At least five people have died and eight more are missing and presumed dead. Authorities have not managed to get onto the island as it is still a highly volatile environment, but helicopters which were sent over on Monday believe they saw six bodies covered in ash.

The injured range in age from 13 to 72, many have suffered severe burns and doctors have warned that there is a chance not all will survive.

Two of those that were on the island at the time of the eruption were from the UK, four were from Germany, five from New Zealand, 24 from Australia, nine from the US, two from China and one from Malaysia.

What is the White Island Volcano?

White Island was discovered by Captain Cook in 1769 and was named after its rising smoke plumes. The volcano is one of the country’s most active and it has built up over 150,000 years of activity. It is situated 321 metres above sea level, however, nearly 70% of it is underwater.

White Island previously experienced a major eruption in 2000, which was followed by a long period of inactivity until several eruptions in 2012 and 2013, but no tourists were harmed. There was also a short-lived eruption in April 2016.

The Volcano sits 30 miles (48km) from the North Island’s east coast and it became a private scenic reserve in 1953. Daily tours allow over 10,000 people to visit the volcano every year. Police are now asking people to avoid areas on the North Island that were close to the eruption, including the Whakatane Heads and Muriwai Drive areas.

Brad Scott, a volcanologist with GNS Science, said:

“The eruption was significant and sent a plume of steam and ash about 12,000 feet into the air. It had affected the whole of the White Island crater floor.”

What caused the White Island eruption?

The eruption was a hydrothermal explosion which is caused by steam, rather than magma, making it harder to track and predict when it may erupt.

White Island is one of many volcanoes in New Zealand that can produce sudden hydrothermal explosions which can happen at any time. In these cases, magma is shallow and the water and gas which is trapped below the surface affect surface and groundwater to form vigorous hydrothermal systems.

Events such as earthquakes, gas input from below, or changes in the lake water level can disrupt the balance and release the pressure on the hot and trapped water which rapidly converts liquid to steam, causing an eruption.

The conversion of water to steam is supersonic in speed and the liquid can expand to 1,700 times its original volume, which is what causes the huge explosion. It is not known for sure what event triggered the explosion at White Island, but investigations are underway to discover what caused the volcano to suddenly spew plumes of smoke and debris 3,600m (12,000ft).

Were there any warnings in place?

In November, the GeoNet agency raised the volcanic eruption alert for White Island to two out of a possible five, indicating increased activity, however, tourists still continued to visit. After the eruption, the alert level increased to four. It later reduced the alert level back down to three as the eruption wasn’t sustained beyond the initial blast.

The alerts were delivered by scientists at the geological agency GeoNet, which stated in a 3 December report that “the level of activity at the vent is variable and when in a stronger phase, some material is being deposited” and that there was “substantial gas, steam and mud bursts observed at the vent located at the back of the crater lake.”

However, while scientists are responsible for recording and documenting volcanic information, they do not control who can and cannot visit volcanoes. A volcanologist at the University of Auckland, Shane Cronin, said:

“One thing that’s gone on in recent years is the increasing number of tour groups and the increasing popularity of the site. That brings perhaps an additional level of risk.”

“I think there should also be quite a bit of soul-searching about how the alert level systems are understood and used. They do seem quite artificial and quite out of touch with operational needs.”

Ray Cas, a professor in geosciences at Monash University, Melbourne added:

“White Island has been a disaster waiting to happen for many years. Having visited it twice, I have always felt that it was too dangerous to allow the daily tour groups that visit the uninhabited island volcano by boat and helicopter.”

Putting monitoring and warning systems in place for hydrothermal eruptions is a huge challenge. Those systems that already are in place are ‘primed’ for such events, but the triggers are poorly understood.

Warnings for hydrothermal eruptions can only be given in seconds to minutes. The only chance for predicting such events is to track the potential vapour and liquid pressure in the hydrothermal systems and to learn from long-term behaviour to understand when they may reach a supercritical state. However, there are no simple rules and each hydrothermal system differs.

Future eruptions and impacts

Hydrothermal eruptions are short-lived, but once one occurs, it is likely that further smaller eruptions may take place as the system re-equilibrates. White Island is an acute location for such activity.

The recent eruption at White Island is likely to have a significant impact on the tiny tourist town of Whakatāne. The town’s population of 35,500 is largely dependent on the 20,000 tourists who visit White Island each year.


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