Whakaari ash plume silhouetted at sunrise

Author: Ben Leahy,
Publish Date: Fri, 26 Jul 2024, 11:28am

Ash has shot out of Whakaari/White Island setting up photo opportunities against a beautiful morning sunrise.

The “short period of sunrise ash emission” was also captured Geonet’s webcams.

The science group set up to monitor earthquakes and volcanoes said Whakaari has been emitting “an almost continuous stream and gas plume” in recent weeks.

However, this morning’s plume posed “no risk to the mainland” Bay of Plenty coastline.

It said the ash fall didn’t extend much beyond the island’s coast.

“As always, we will continue to closely monitor the volcano for further changes in unrest.”

What drives Whakaari’s emissions?

As molten rock (magma) rises under the volcano the pressure drops and volcanic gases leak from the magma, GeoNet said.

A short period of sunrise ash emission at Whakaari/White Island has been seen on our webcams this morning. Ashfall didn't extend much beyond the island and poses no risk to the mainland. As always, we will continue to closely monitor the volcano for further changes in unrest.
— GeoNet (@geonet) July 25, 2024

“This starts deep under the volcano. As the gas can travel more easily through the volcano than the magma, it soon makes its way to the surface, to vent and form a plume above the volcano.

“A steam and gas plume is about 80% steam and water vapour [H2O]. After steam, in order of volume, the gases are carbon dioxide [CO2], sulphur dioxide [SO2] and hydrogen sulphide [H2S]. GNS measures the volume of gases present during regular gas and observation monitoring flights.”

What about volcanic ash?

GeoNet’s Volcano Activity Bulletin published on July 16, advised that minor amounts of ash were observed intermittently at the vent during a recent gas flight.

This was not considered to constitute new eruptive activity.

Instead, the small amount of ash observed was likely caused by some erosion inside the vent due to the vigorous degassing that was feeding the steam and gas plume, says the volcanic monitoring organisation.

“These kinds of changes in the vent area and the plume have been seen many times in the past and represent normal processes at the volcano. No ash was observed in the plume outside of the crater.”

How far from the mainland is Whakaari/White Island?

Whakaari/White Island sits 48km offshore from Whakatāne.

This image captured on July 12 shows a plume of gas and steam emitting from a vent from Whakaari/White Island. Minor amounts of brown non-eruptive ash can also be seen near the vent at the base of the plume. Photo / GeoNet

What does it look like underwater?

Whakaari/White Island is a very large volcano, similar in scale to Tongariro. About 70% of the volcano is under the sea.

This image captured on July 4 shows the low-level plume of gas and vapour drifting eastwards from Whakaari/White Island. Photo / Chris Clark

What are the impacts of a plume?

Due to Whakaari/White Island’s distance from the North Island coast, and the prevailing wind that takes the plume away from the coast, there is a very low likelihood of it having any effect on the mainland, GeoNet said.

“However, plumes have reached the mainland before, and records exist of plumes reaching the coast dating back to at least 1873.

“The most likely, albeit infrequent, impact of a plume such as the one we are seeing now is that people might smell volcanic gas and possibly find it an irritant to the eyes and respiratory system.

“With the current activity taking place far from the coast, and with no ash in the plume, this is unlikely. Neither do we expect ashfall on the mainland with the current state of activity. Should the volcanic activity increase, people would be provided with appropriate advice to manage any hazard effects.”

Whakaari/White Island location.

What do New Zealand’s Volcanic Alert Levels mean?

At the time of publishing this story Whakaari White Island is at Volcanic Alert Level 2 – which means it is in a moderate to heightened state of unrest.

To help GeoNet communicate the current status of the active volcanoes in New Zealand, the organisation uses the New Zealand Volcanic Alert Level System.

This system defines the current level of activity at each active volcano. The alert levels range from 0 to 5, where level 0 is no volcanic unrest and Level 5 is a major volcanic eruption.

The alert level itself is a simple method of indicating a status change in the volcano. GeoNet uses Volcano Activity Bulletins to communicate in-depth and important information about the activity and trends occurring at the volcano. The bulletins are shared with local and national responding agencies, stakeholders, media and the public.

Whakaari/White Island size comparison.

Does Volcanic Alert Level 2 mean the volcano will erupt?

“The NZ Volcanic Alert system is not a predictive tool. It reports the current state of the volcano, and the level of unrest could be increasing towards an eruption or declining after one. Level 1 and Level 2 communicate periods of volcanic unrest. Levels 3, 4 and 5 relate to small, medium/moderate and large eruptions.

“On May 24, we raised the Volcanic Alert Level to 3 following minor and short-lived eruptive activity and lowered it back to Level 2 on 29 May when the eruption stopped. However, there have also been times recently that Whakaari/White Island has remained at Level 2 unrest and no subsequent eruptions happened.

“It’s important to note that an eruption might occur at any alert level, and volcanic alert levels do not necessarily move in sequence, as activity can change rapidly.

“Due to Whakaari/White Island’s distance from the North Island coast there is an extremely low likelihood of any effects from an eruption on the mainland. If there were any effects, the most likely are fine ash falls (like pollen or talcum powder) and the smell of volcanic gas.”

New Zealand Volcanic Alert Level System.

How does GeoNet keep watch on Whakaari/White Island?

At present, the Volcanic Ash Advisory Centre at MetService provides most of the ability to confirm if larger ash-producing eruptions have occurred, via satellite remote sensing and rain radar data.

“Our combined remote monitoring toolkit includes monitoring stations on the mainland, observation and gas flights, and remote sensing technology, like radar, gas, and thermal satellite imagery.

“We also receive information about Whakaari from satellite data from the German and European Space Agencies, which can provide us a view of ground deformation and gas emissions.”