Whakaari/White Island: Elevated volcanic unrest continues

Published: Wed Feb 19 2020 11:55 AM

Volcanic Alert BulletinWI – 2020/05
Wed Feb 19 2020 12:00 PM; Whakaari/White Island Volcano
Volcanic Alert Level remains at 2
Aviation Colour Code remains at Yellow

• Whakaari/White Island remains in an elevated state of unrest • Volcanic gas fluxes are declining slightly • Aerial observations confirm presence of high temperature fumaroles • The Volcanic Alert Level remains at Level 2; Aviation Colour Code remains at Yellow

As a continuation of our monitoring of Whakaari/White Island, we conducted two aerial-based measurements and observations of the island in the past two weeks. A gas flight confirms the steady decline in both CO2 and SO2 flux since the eruption, albeit at slightly elevated levels. The result from this flight is consistent with recent gas measurements and indicates the continued presence of shallow magma beneath the primary vent area. This is further confirmed by a helicopter-based thermal infrared survey of the five lava lobes and fumarolic gases in the vent area. Temperatures exceeding 660 °C mean that the system remains very hot with no sign of cooling over the past two weeks. Despite these high fumarole temperatures, a small pond of water is present in the primary vent area and small-scale jetting is now occurring. This is similar to the activity seen in September-December 2019.

Our volcano monitoring team met on Monday 17 February and evaluated the eruption likelihood, based on recent data and observations. The team consider an eruption to be very unlikely (1 %) in any 24-hour period. We will reassess next month, or earlier if needed.

Although very unlikely, the active vent area remains potentially unstable and an eruption could occur with limited precursory activity. Plausible eruption styles include collapse of unstable material around the vents, or a significant decrease in gas emissions to allow the rapid ingress of water onto the shallow magma body, causing a sharp, explosive event.

Should any explosive activity produce an ash cloud, the likelihood of ash affecting the mainland remains very low. Under suitable weather conditions, the gas and steam plume may be noticed on the mainland as weak acid rain.

Satellite data retrieved over the last two weeks shows continued land movement, at a reduced rate along the west wall of the Main Crater and the 1914 landslide scarp. No obvious changes were noted along the landslide scarps on the latest observation flight (12 February).

The Volcanic Alert Level remains at Level 2.

The Aviation Colour Code remains at Yellow.

Volcanic Alert Level 2 indicates moderate to heightened unrest with potential for eruption hazards, including unpredictable and life-threatening steam driven eruptions.

The Volcanic Alert Level reflects the current level of volcanic activity and is not a forecast of future activity.

GNS Science and our National Geohazards Monitoring Centre continue to closely monitor Whakaari/White Island for further signs of activity. Further updates will be provided as the situation evolves.

Geoff Kilgour

Duty Volcanologist

Media Contact: 021 574 541 or media@gns.cri.nz