How will White Island volcanic eruption affect the rest of New Zealand?
Monday, 9 December 2019
It is unlikely more than a 'minor' amount of ash fall from a 'significant' eruption on White Island will reach the mainland of New Zealand, a volcanologist says.
At 2.30pm on Monday, White Island volcano, in the Bay of Plenty, erupted sending a large plume of white smoke into the sky. One person is critically injured and number of people who were visiting the island at the time are unaccounted for.
Brad Scott, a volcanologist from GNS Science, said it was very unlikely anyone on the mainland of New Zealand would suffer any adverse health impacts from the eruption.
'We do not expect more than a minor amount of ash to reach East Cape in the coming hours,' Scott said.
**READ MORE:
* In pictures: White Island eruption
* Injuries as volcano erupts**
'On the island however, unfortunately, there will be injuries - rocks and material thrown out from the volcano would have the possibility to kill or injure anybody nearby.
'It was a significant eruption and we are concerned for anybody who was on the island at the time.'
It is believed up to 50 people may have been on White Island when the eruption occurred.
Scott said the last time White Island erupted was in 2016. It was described as a 'minor eruption' and no-one was injured.
'As White Island is an active volcano, it can erupt and this cannot always be predicted,' Scott said, adding: 'The volcanic alert level on the island had been raised recently.'
The alert level on the island had been raised from a level one to a level two in November when a small amount of sulphur dioxide (SO2) gas output was observed.
SO2 gas originates from magma, or molten rocks, and indicates a possible increase in gas passing through the volcano from underneath it, Scott said.
Volcanic Alert Level two is mostly associated with unrest hazards on the volcano, which could include eruptions of steam, gas, mud and rocks, these eruptions could have little to no warning.
Currently, White Island is at alert level three, which indicated a minor local eruption was in progress.
Scott said it was up to tour operators on the island to monitor the situation and decide whether to continue operating when the volcanic alert level was raised.
Most of the ash from the eruption was falling one or two kilometres away from the island into the sea, Scott said.
He was unsure whether this would have any impact on sea life in the area.
Professor Shane Cronin, a volcanologist based at University of Auckland, said sudden eruptions from volcanoes such as White Island could be expected at any time.
'Magma is close to the surface, and the heat and gases from this heat the surface and ground waters to form vigorous hydrothermal systems, these eruptions can occur suddenly and with little or no warning because they are driven by the expansion of super-heated water into steam.'
'The hazards expected from such events are the violent ejection of hot blocks and ash, and formation of 'hurricane-like' currents of wet ash and coarse particles that radiate from the explosion vent. These can be deadly in terms of causing impact trauma, burns and respiratory problems. The eruptions are short-lived, but once one occurs, there are high chances for further, generally smaller ones as the system re-equilibrates.'
Whakaari/White Island, 48km offshore from Bay of Plenty, is New Zealand's most active cone volcano, built up by continuous volcanic activity during the past 150,000 years. With 70 per cent of the volcano under the sea, it is also the country's largest volcanic structure.
GeoNet said the longest historic eruption of the island was from 1975-2000. During that time, many collapse and explosion craters developed. For long periods active vents in the craters emitted volcanic ash.
GNS Science said there was still significant uncertainty as to future changes on White Island but currently, there were no signs of further escalation.