Minor steam explosions at Whakaari/White Island
A series of short-lived, low-energy steam explosions occurred on 19 February 2021 at Whakaari / White Island following a small increase in volcanic tremor levels. These explosions took place over about 100 minutes. These small events do not appear to have produced any traces of ash locally. Since the event, activity has returned to low-level. The Volcanic Alert Level remains at 1.
Starting at around 2.20 am today (19 February) our seismic and acoustic (air pressure) sensors at Whakaari/White Island detected a series of small steam explosions. No observations were available from the island’s webcams as it was still dark. The overall series of pulses lasted for about 100 minutes and were of a similar size to those recorded on 29 December 2020. Volcanic tremor levels started to rise around 9 pm on 18 February and stopped around 5.50am today coincident with the end of the explosions.
Sudden, small steam explosions can occur with little or no warning. Small explosions like those this morning and on 29 December 2020 can be recorded on our seismic (ground vibrations) and acoustic (pressure wave in the atmosphere) monitoring network.
A gas flight was completed yesterday (18 February) showed no changes in gas flux or crater conditions from a month earlier. The level of seismic tremor had been slightly above background in the two days preceding the explosions but has since returned to background levels. 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 foundhere.
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 and visual observations.
Brad Scott Duty Volcanologist Media Contact: 021 574 541 or media@gns.cri.nz