Small steam explosions recorded at Whakaari/White Island

Published: Wed Dec 30 2020 5:15 PM

Volcanic Alert BulletinWI – 2020/18
Wed Dec 30 2020 5:15 PM; Whakaari/White Island Volcano
Volcanic Alert Level remains at 1
Aviation Colour Code remains at Green

A series of short-lived, low energy steam explosions occurred on 29 December 2020 at Whakaari / White Island over a period of ~ 30 mins. This small event consisted of at least 20 individual pulses and may have produced traces of ash locally in the steam plume for a few minutes. Since the event, activity has returned to low-level. The Volcanic Alert Level remains at 1.

Starting at around 3 pm on Tuesday 29 December, a series of small steam explosions were detected on our seismic and acoustic (air pressure) sensors at Whakaari/White Island. Images from the island’s webcams suggest some more vigorous pulses of steam coming from the active vent during that time. Ash was not detected in the atmosphere via satellite images by our colleagues at Metservice, but minor traces of ash might have been present near the vent for a few minutes during the steam explosions. The overall series of pulses lasted for about 30 min.

Sudden, small steam explosions can occur with little or no warning. While changes in the appearance of the steam emission at the surface can be subtle and may be difficult to see on the webcams, such small explosions can be recorded on our seismic (ground vibrations) and acoustic (pressure wave in the atmosphere) monitoring network.

The level of seismic tremor had been slightly above background in the previous two days but has since dropped back down to background levels. Gas emissions (Sulfur dioxide) also remain largely unchanged and we have seen very few discrete earthquakes. As a result, the Volcanic Alert Level remains at 1 and the Aviation Colour Code remains at Green.

The Volcanic Alert Level reflects the current level of volcanic unrest or activity and is 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. While Volcanic Alert Level 1 is mostly associated with environmental hazards, 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.

Further information about the volcanic alert levels and what they mean can be found here.

GNS Science and the National Geohazards Monitoring Centre continue to closely monitor Whakaari for further changes in unrest. GeoNet monitors Whakaari via a network of seismic and acoustic sensors, GNSS (GPS) receivers, cameras, and gas flights.

Agnes Mazot Duty Volcanologist

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