White Island unrest increases, Aviation Colour Code changed
Volcanic Alert Bulletin WI-2013/3 - White Island Volcano
24 January 2013, 4:00pm - Volcanic unrest increases, Aviation Colour Code changed to Orange.
Over the last 20-30 hours the style of seismic activity at White Island has changed. The level of volcanic tremor has started to decrease, but hybrid volcanic earthquakes have appeared. Hybrid earthquakes are typically associated with the movement of molten material (magma) within an active volcano. This change in activity is consistent with an increase in the level of unrest; hence the Aviation Colour Code has been lifted to Orange.
The current episode of activity started in August 2012 (explosions and ash emission) followed in November 2012 by extrusion of a small lava dome. Elevated but not high unrest followed. However, volcanic unrest has been increasing at White Island since about January 14. This unrest has been manifested as increased hydrothermal activity in the ‘hot lake’ and has been described as some of the most vigorous activity seen at White Island for many years.
GNS volcanologist Gill Jolly commented “Visitors to White Island are now at the highest level of risk since the start of the 2012 eruptions. Hazards to visitors can include the health effects of volcanic gas exposure, including respiratory issues, skin and eye sensitivity to acid gases. Explosive eruptions can occur at any time with little or no warning. We advise a high level of caution should be taken, if visiting the island”.
The outcomes of the unrest could be either the passive intrusion of magma to shallow depths with no changes in surface activity, more dome building as in November 2012 or explosive eruptions and ash emissions, like in August 2012.
The state of unrest at White Island is increasing and future eruptions are possible with little or no warning. The increased level of unrest does mean that there is an increased hazard to visitors. GNS Science continues to closely monitor White Island through the GeoNet project.
Weather permitting a ‘gas flight’ will be made tomorrow morning to ascertain if there have been any changes in the gas flux from the volcano.
Hybrid volcanic earthquakes are so called because they are a mix of rock fracturing and magmatic vibration. They are thought to represent the movement of magma in a volcano.
Aviation Colour Codes are based on four colours and are intended for quick reference only in the international civil aviation community.
The Volcanic Alert Level ranges from 0 to 5 and defines the current status at a volcano. Level 1 indicates signs of volcanic unrest.
The GeoNet project is funded by EQC and provides monitoring for all of New Zealand’s volcanoes.