Whakaari/White Island: 'Small explosions' noted as volcanic tremors rumble

White Island after the deadly volcanic eruption on December 9, 2019. Photo / File

Two "low energy" volcanic tremors rumbled Whakaari/White Island last week.

GNS Science duty volcanologist Craig Miller said in a bulletin the "short-lived" tremors happened on Thursday and Friday.

The first started around 8.30pm on Thursday and lasted 30 minutes.

The second started the next day about 3.30pm and lasted around three hours. It was accompanied by "minor steam-gas bursts/explosions from the active vent area".

"The steam and gas-driven activity was recorded by our seismic and air pressure sensors and is interpreted as a series of small explosions, originating within the vent or at shallow depth.

"Any erupted material from this type of activity is typically limited to a few metres from the vent.

"No observations were available from the island's webcams. Both the recent episodes were smaller in size than those recorded on 29 December, 2020, and 18 February, 2021," Miller said.

Last week's events followed similar episodes in mid-February and early March and the activity has since returned to typical low levels.

The Volcanic Alert Level remained at 1 and the aviation code stayed green.

GNS Science said there had been no response noted from the island to the March 5 magnitude 7.3 earthquake off the East Cape.

"Gas and observation flights are scheduled this week to measure vent temperatures and gas emissions. The level of seismic tremor remains at background levels."

GNS Science and the National Geohazards Monitoring Centre continue to closely monitor Whakaari for further changes in unrest.

Volcanic alert levels

- Reflect the current level of volcanic unrest or activity
- Are not a forecast of future activity.
- Volcanic Alert Level 1 indicates the primary hazards are those expected during volcanic unrest; including discharge of steam and hot volcanic gases, earthquakes, landslides and hydrothermal activity.
- Level 1 is mostly associated with environmental hazards but eruptions can still occur with little or no warning.
- The main plausible triggers for a sudden eruption remain the collapse of unstable material in an active vent and the possible ingress of water underground onto the shallow magma body.