'Minor' eruption on White Island

Tuesday, 13 September 2016

Volcanic and aviation alert levels have been raised for White Island after a minor eruption.

The aviation colour code has been raised from green to orange, with GeoNet reporting the 'volcano is exhibiting heightened unrest with increased likelihood of eruption'. The volcanic alert level had been raised from one to three, with 'eruption hazards' near the vent.

GeoNet's webcams on the island showed ash coming from the vent, although during the day some were affected by ash and steam.

'The level of volcanic activity at White Island has increased late this morning with minor volcanic ash been passively emitted from a vent on the 2012 lava dome,' GeoNet said.

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GNS Science volcanologist Brad Scott described the eruption as 'pretty passive'.

'It's not coming out under high velocity or high pressure.

'We have large gas and steam vents on the island, and occasionally they switch to just picking up debris in their path and carrying little rock fragments with them.'

Those fragments were less than a millimetre in size.

'We're right at the minor end of the spectrum,' Scott said.

Temperatures in the vent involved were about 295 degrees Celsius when measured during a visit last week. That was down 40-50C from the previous measurement in August.

'Basically the steam's just getting dirty.'

'We haven't seen any change in earthquake activity at the volcano. Normally when it starts ashing we get an increase in seismic activity. There hasn't been any this time. We haven't observed any other changes as of yet.'

Scott said the volume of ash coming from the volcano was not measurable.

'The word we are using now is 'minor', 'very minor' might be a better expression.'

Three possible scenarios were that the ash could stop, it could stay at current levels, or it could increase.

'This just started late this morning and we aren't really sure which of those scenarios we would back.'

Tour operators had been notified.

Tours were carried out by boat and helicopter. Anywhere from 50-100 people a day visited the island.

In a mid-afternoon update duty volcanologist Steve Sherburn said that as far as GNS could tell the level of activity at White Island had not escalated since late morning. 'Seismic activity remains low on the island.'

A MetService visible satellite image shows a narrow plume of ash from White Island heading northeast out to sea, passing to the north of East Cape.

'Any ash fall will follow wind direction and is likely to be blown offshore over the next day,' Sherburn said.

Scott said steam was always coming out of White Island, now it was just a slightly darker colour.

If any ships were going around East Cape, those on board might notice a minor amount of ash in the air or on the water, if their track took them under the plume. 'They'll be steaming through a bit of dust'.

White Island Tours marketing manager Patrick O'Sullivan said it was business as usual for the company at this stage.

The ability to operate tours was not affected at this point, he said, but there could be some modifications to the way a tour was carried out. That was assessed daily.

O'Sullivan said the amount of time spent near the part of the island producing the ash may be limited.

The company's website would also be updated and information sent to passengers would let them know what was happening.

At this time of year, the company only had a morning tour to the island. The next trip would be on Wednesday, weather conditions permitting.